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Blog » Space

 
     
 

16th September 2014

First evidence of water ice clouds beyond our
Solar System

Astronomers have discovered the first evidence of water ice clouds on an object outside our own Solar System.

 

WISE 0855–0714
W0855 is the fourth closest system to our Sun, at 7.3 light-years away. In this illustration, the Sun is the bright star directly to the right of the brown dwarf. The slightly shifted star field accurately reflects how the sky around the constellations of Aquila and Delphinus would appear from this vantage point.

 

Scientists at the Carnegie Institution of Washington report the first evidence of water ice clouds on a body outside of our own Solar System. Water ice clouds are present on the gas giants – Jupiter, Saturn, Uranus, and Neptune – but have never been seen outside the planets orbiting our Sun until now. This finding is published by The Astrophysical Journal Letters.

At the Las Campanas Observatory in Chile, a near-infrared camera was used to detect WISE 0855–0714 (also called W0855) a tiny sub-brown dwarf located approximately 7.3 light years from Earth. This was first seen by a NASA space telescope – Wide-Field Infrared Survey Explorer – and confirmed in April 2014. But it was not known if the object could be seen by ground-based facilities. The Carnegie researchers managed to obtain 151 images from Las Campanas over a period of three nights.

"This was a battle at the telescope to get the detection," said Jacqueline Faherty, who led the study. 

Chris Tinney, co-author on the result, stated: "This is a great result. This object is so faint and it’s exciting to be the first people to detect it with a telescope on the ground."

 

nearest stars

 

Brown dwarfs are too small to be classified as stars, but too large to be considered planets. Because of their size, they are too small to sustain the hydrogen fusion process that fuels stars. Their temperatures can range from nearly as hot as a star to as cool as a planet, and their masses also range between star-like and giant planet-like. They are of particular interest to scientists because they offer clues to star-formation processes. They also overlap with the temperatures of planets, but are much easier to study since they are commonly found in isolation.

W0855 is the fourth closest system to our own, practically next door in terms of astronomical distances. It is also the coldest object of its type found in interstellar space, having a temperature between 225 to 260 K (−48 to −13°C; −55 to 8°F). A comparison of near-infrared images of W0855 with models for predicting the atmospheric content of brown dwarfs showed evidence of frozen clouds of sulfide and water.

"Ice clouds are predicted to be very important in the atmospheres of planets beyond our Solar System, but they've never been observed outside of it before now," Faherty said.

The next generation of telescopes – such as the E-ELT (2022), PLATO observatory (2024-2030) and the ATLAST project (2025-2035) – will provide more detailed views of planets' and brown dwarfs' atmospheres.

 

 

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3rd September 2014

NASA to go ahead with its huge new rocket

NASA has completed a review of the Space Launch System (SLS). The rocket will have its first test launch "no later than November 2018" with a possibility of manned flights to Mars in the 2030s.

 

space launch system rocket

 

NASA has completed a rigorous review of the Space Launch System (SLS) – a next generation rocket designed to carry humans beyond Earth orbit and eventually to Mars. The project has received the go-ahead to proceed from the formulation stage to development, something no other exploration class launch vehicle has achieved since the agency built the Space Shuttle.

"We are on a journey of scientific and human exploration that leads to Mars," said NASA Administrator Charles Bolden. "And we’re firmly committed to building the launch vehicle and other supporting systems that will take us on that journey."

For its first test flight, the SLS will be configured for a 70-metric-ton (77-ton) lift capacity and carry an uncrewed Orion spacecraft beyond low-Earth orbit. In its most powerful configuration, it will provide an unprecedented lift capability of 130 metric tons (143 tons), enabling missions even farther into our Solar System, including such destinations as an asteroid and Mars.

“Our nation is embarked on an ambitious space exploration program, and we owe it to the American taxpayers to get it right,” said Associate Administrator Robert Lightfoot, who oversaw the review process. “After rigorous review, we’re committing today to a funding level and readiness date that will keep us on track to sending humans to Mars in the 2030s – and we’re going to stand behind that commitment.”

"The Space Launch System Program has done exemplary work during the past three years to get us to this point," said William Gerstenmaier, associate administrator for the Human Explorations and Operations Mission Directorate, at the NASA Headquarters in Washington. "We will keep the teams working toward a more ambitious readiness date, but will be ready no later than November 2018.”

“Engineers have made significant technical progress on the rocket and have produced hardware for all elements of the SLS program,” said SLS program manager Todd May. “The team members deserve an enormous amount of credit for their dedication to building this national asset.”

In April, the program delivered the first piece of flight hardware for Orion’s maiden flight, targeted for December 2014. This features the same design that will be used on the SLS rocket’s first flight, Exploration Mission-1.

The SLS will be the largest, most capable rocket ever built. In addition to opening new frontiers for human explorers, it will enable a new generation of science missions in the outer Solar System – with heavier payloads and more complex robotic landers, for example.

 

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27th August 2014

Lockheed Martin agrees deal to track space debris

US defence giant Lockheed Martin has formed a partnership with Australian tech firm Electro Optic Systems to monitor the growing problem of space debris.

 

space junk

 

Lockheed Martin announced yesterday that it will join forces with Electro Optic Systems (EOS) to provide space tracking services to the space industry. This joint development will see the establishment of a new facility in Western Australia – operational by early 2016 – to offer a more detailed picture of space debris for both government and commercial customers.

The site will use a combination of lasers and highly sensitive optical systems to detect, track and characterise an estimated 200,000 man-made objects. These advanced electro-optical technologies will zoom in on specific objects to determine how fast they’re moving, what direction they’re spinning and what they’re made of.

“Ground-based space situational awareness is a growing priority for government and commercial organisations around the world that need to protect their investments in space,” said Rick Ambrose, executive vice president, Lockheed Martin Space Systems. “Through this agreement with Electro Optic Systems, we’ll offer customers a clearer picture of the objects that could endanger their satellites, and do so with great precision and cost-effectiveness.”

“The partnership with Lockheed Martin will help both organisations establish a global network of space sensors, while simultaneously increasing the market reach of the partners’ data and services,” said Electro Optic Systems Chief Executive Officer Ben Greene. “We consider the strategic partnership with Lockheed Martin a major step towards the achievement of critical mass of sensors, data and services, all of which are critical in providing detailed yet easily usable information on space debris.”

Space junk has been accumulating in Earth orbit for over 50 years. It is made up of everything from spent rocket stages, to defunct satellites, to debris left over from accidental collisions. The amount of space junk is expected to triple by 2030. Experts have expressed concerns about a potential scenario known as Kessler Syndrome – in which a catastrophic chain reaction occurs, making space exploration and satellite communications impossible. This was depicted in the recent sci-fi movie Gravity.

 

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6th August 2014

Rosetta probe arrives at comet 67P

As we reported last month, the European Space Agency's Rosetta probe has been nearing its destination: the icy comet 67P/Churyumov-Gerasimenko. After a journey of ten years, five months and four days – covering a distance of 4 billion miles (6.4 billion km) – it has finally arrived in orbit. The journey involved looping around the Sun five times, followed by a series of ten rendezvous manoeuvres that began in May to adjust its speed and trajectory to gradually match those of the comet, which is rushing towards the inner Solar System at nearly 34,000 mph (55,000 km/h). If any of those manoeuvres had failed, the mission would have been lost, and the spacecraft would simply have flown by the comet.

ESA's Director of Science and Robotic Exploration, Alvaro Giménez: "Today's achievement is a result of a huge international endeavour spanning several decades. We have come an extraordinarily long way since the mission concept was first discussed in the late 1970s and approved in 1993, and now we are ready to open a treasure chest of scientific discovery that is destined to rewrite the textbooks on comets for even more decades to come."

Rosetta will now perform a detailed study of the comet, identifying a target site for the Philae robotic lander. As many as five possible landing sites will be identified by late August, before the primary site is identified in mid-September. The final timeline for the sequence of events for deploying Philae – currently expected for 11th November – will be confirmed by the middle of October. After landing, Rosetta will continue to accompany the comet until its closest approach to the Sun in August 2015 and beyond, watching its behaviour from close quarters to provide a unique insight and real-time experience of how a comet works as it hurtles around the Sun. This could reveal new clues to the origins of the Solar System, our home planet and life itself.

 

comet 67p

 

comet 67p

 

comet closeup image

 

comet close up image

All images credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

 

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1st August 2014

NASA reveals payload for Mars 2020 rover

NASA has announced the payload for its Mars 2020 rover mission, an upgraded version of the Curiosity rover currently exploring the Red Planet.

 

mars rover 2020

 

The next rover NASA will send to Mars in 2020 will carry seven instruments for unprecedented science and exploratory investigations. The agency confirmed the selected payload yesterday at its headquarters in Washington. Managers made their selections out of 58 proposals received in January from researchers and engineers worldwide. Proposals received were twice the usual number submitted for instrument competitions in the recent past. This is an indication of the extraordinary interest by the science community in the future exploration of Mars. The selected proposals have a total value of approximately $130 million for research and development.

The Mars 2020 mission will be based on the design of the highly successful Mars Science Laboratory rover – Curiositywhich landed in 2012 and is currently operating on Mars. The new rover will carry more sophisticated, upgraded hardware and new instruments to conduct geological assessments of the rover's landing site, determine the potential habitability of the environment, and directly search for signs of ancient Martian life. It will identify and store a collection of 30 rock and soil samples for return to Earth by a later mission. The rover will feature a new set of wheels, tougher and more durable than its predecessor, potentially boosting the mission lifespan.

"The Mars 2020 rover, with these new advanced scientific instruments – including those from our international partners – holds the promise to unlock more mysteries of Mars' past as revealed in the geological record," said John Grunsfeld, a former astronaut, and associate administrator of NASA's Science Mission Directorate in Washington. "This mission will further our search for life in the universe and also offer opportunities to advance new capabilities in exploration technology."

The Mars 2020 rover will also help to advance our knowledge of how future human explorers could use natural resources available on the surface of the Red Planet. An ability to live off the Martian land would transform future exploration of the planet. Designers of manned expeditions can use this mission to understand the hazards posed by Martian dust and demonstrate technology to process carbon dioxide from the atmosphere to produce oxygen. These experiments will help engineers learn how to use Martian resources to produce oxygen for human respiration and potentially for use as an oxidiser for rocket fuel.

"The 2020 rover will help answer questions about the Martian environment that astronauts will face and test technologies they need before landing on, exploring and returning from the Red Planet," said William Gerstenmaier, associate administrator for the Human Exploration and Operations Mission Directorate at the NASA Headquarters in Washington. "Mars has resources needed to help sustain life, which can reduce the amount of supplies that human missions will need to carry. Better understanding the Martian dust and weather will be valuable data for planning human Mars missions. Testing ways to extract these resources and understand the environment will help make the pioneering of Mars feasible."

 

mars 2020 rover payload

 

The selected payload instruments are:

  • Mastcam-Z, an advanced hi-res camera system with panoramic, stereoscopic and zoom ability.
  • SuperCam, an instrument that can provide imaging, chemical composition analysis, and mineralogy. The instrument will also be able to detect the presence of organic compounds in rocks and regolith from a distance.
  • Planetary Instrument for X-ray Lithochemistry (PIXL), an X-ray fluorescence spectrometer that will also contain an imager with high resolution to determine the fine scale elemental composition of Martian surface materials. PIXL will provide capabilities that permit more detailed detection and analysis of chemical elements than ever before.
  • Scanning Habitable Environments with Raman & Luminescence for Organics and Chemicals (SHERLOC), a spectrometer that will provide fine-scale imaging and uses an ultraviolet (UV) laser to determine fine-scale mineralogy and detect organic compounds. SHERLOC will be the first UV Raman spectrometer to fly to the surface of Mars and will provide complementary measurements with other instruments in the payload.
  • The Mars Oxygen ISRU Experiment (MOXIE), a device that will produce oxygen from Martian atmospheric CO2, demonstrating a technology of critical importance in future manned exploration.
  • Mars Environmental Dynamics Analyzer (MEDA), a set of sensors that will provide measurements of temperature, wind speed and direction, pressure, relative humidity and dust size and shape.
  • Radar Imager for Mars' Subsurface Exploration (RIMFAX), a ground-penetrating radar that will provide centimetre-scale resolution of the geologic structure of the subsurface.

This announcement comes in the same week that an earlier 2004 roverOpportunity – having travelled more than 25 miles (40 kilometres), has set a new "off-world" record as the rover having driven the greatest distance. It surpasses the previous record held by the Soviet Union's Lunokhod 2 rover that had travelled 24 miles (39 kilometres).

 

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21st July 2014

New images of comet as Rosetta probe nears target

The European Space Agency has released striking new images of comet 67P/Churyumov-Gerasimenko. As part of the Rosetta mission, a robotic lander will be deployed on the surface.

 

comet animation

 

As the Rosetta spacecraft nears its destination – comet 67P/Churyumov-Gerasimenko – the object is proving to be full of surprises. New images obtained by OSIRIS, the onboard scientific imaging system, confirm the body's peculiar shape hinted at in earlier pictures. Comet 67P is obviously different from other comets visited so far.

"The distance still separating Rosetta from 67P is now far from astronomical," said Holger Sierks, OSIRIS Principal Investigator from the Max Planck Institute for Solar System Research (MPS) in Germany. "It's a trip of less than 14,000 kilometres [about 8,700 miles]. That's comparable to travelling from Germany to Hawaii on a summer holiday."

However, while taking a snapshot of Mauna Kea, Hawaii's highest mountain, from Germany is an impossible feat, Rosetta's camera OSIRIS is doing a great job at catching ever clearer glimpses of its similarly sized destination. Images obtained on 14th July show a tantalizing shape. The comet's nucleus consists of two distinctly separated parts.

"This is unlike any other comet we have ever seen before," said OSIRIS project manager Carsten Güttler from the MPS. "The images faintly remind me of a rubber ducky with a body and a head." How 67P developed this intriguing shape is still unclear. "At this point we know too little about 67P to allow for more than an educated guess," said Sierks.

Later this year, the scientists hope to determine more of the comet's physical and mineralogical properties, which may help to confirm whether its body and head were formerly two individual bodies. In November, the probe will come within 2.5 km (1.5 miles) of the comet and deploy a small robotic lander called Philae. This will take around two hours to reach the surface, using a harpoon system to counter the extremely low gravity. Screws will be drilled to anchor its feet in place, as shown in the video below.

Once attached to the comet, the lander will begin its science mission – using ten instruments to characterise the surface, sub-surface and nucleus, determine the chemical compounds present and study the comet's activities over time. Six cameras mounted on the sides at 60° intervals will provide a 360° panorama around the lander.

 

 

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19th July 2014

Direct evidence of a multiverse?

Scientists are working to bring the multiverse hypothesis – which sounds like science fiction to some – firmly into the realm of testable science.

 

multiverse

 

The Perimeter Institute for Theoretical Physics in Canada is to begin a series of experiments that could demonstrate – for the first time – direct evidence of the so-called multiverse. This theory postulates that other universes may reside outside our own. The central idea is that a "vacuum" existed prior to what we know as the Big Bang. This vacuum simmered with energy (variously called dark energy, vacuum energy, the inflation field, and the Higgs field). Like water in a pot, its high energy began to evaporate – forming bubbles.

Each bubble contained another vacuum, whose energy was lower, but still greater than zero. This energy drove the bubbles to expand, causing some to collide with each other. It’s possible that some produced secondary bubbles. Maybe the bubbles were rare and far apart; maybe they were packed as close together as foam. But the point is: each of these bubbles was a universe. In this picture, our universe is one bubble in a frothy sea of bubbles, possible an infinite number of them.

This version of the multiverse hypothesis is based on what's currently known about cosmic inflation. Although cosmic inflation isn’t accepted by everyone – cyclical models of the universe tend to reject the idea – it is nevertheless a leading theory of the universe’s very early development, and there is some observational evidence to support it.

Inflation holds that in the instant after the Big Bang, the universe expanded at a super-exponential rate – so rapidly that a cubic nanometre of space became a quarter-billion light years across in just a trillionth of a trillionth of a trillionth of a second. It’s an amazing idea, but it would explain some otherwise puzzling astrophysical observations.

 

big bang inflation

 

Inflation is thought to have been driven by an inflation field – which is vacuum energy by another name. Once you postulate that an inflation field exists, it’s hard to avoid an “in the beginning was the vacuum” kind of story. This is where the theory of inflation becomes controversial – when it starts to postulate multiple universes.

Proponents of the multiverse theory argue that it’s the next logical step in the inflation story. Detractors argue that it is not physics, but metaphysics – that it is not science, because it cannot be tested. After all, physics lives or dies by data that can be gathered and predictions that can be checked.

That’s where Perimeter Associate Faculty member Matthew Johnson comes in. Working with a small team that also includes Perimeter Faculty member Luis Lehner, Johnson is working to bring the multiverse hypothesis firmly into the realm of testable science.

“That’s what this research program is all about. We’re trying to find out what the testable predictions of this picture would be, and then going out and looking for them,” says Johnson. Specifically, his research team is considering the rare cases in which our bubble universe might collide with another bubble universe. He lays out the steps: “We simulate the whole universe. We start with a multiverse that has two bubbles in it, we collide the bubbles on a computer to figure out what happens, and then we stick a virtual observer in various places and ask what that observer would see from there.”

 

multiverse computer model

 

Simulating the whole universe – and indeed more than one – might sound extremely difficult, but apparently that’s not so.

“Simulating the universe is easy,” says Johnson. Simulations don't have to include every atom, star, or galaxy – in fact, they account for none of them. “We’re simulating things only on the largest scales,” he says. “All I need is gravity and the stuff that makes these bubbles up. We’re now at the point where if you have a favourite model of the multiverse, I can stick it on a computer and tell you what you should see.”

That’s a small step for a computer simulation program, but a giant leap for multiverse cosmology. By creating testable predictions, the multiverse model has crossed the line from appealing story to real science. In fact, Johnson says, the program has reached the point where it can rule out certain models of the multiverse: “We’re now able to say that some models predict something that we should be able to see, and since we don’t in fact see it, we can rule those models out.”

For example, the collision from a neighbouring bubble universe might leave a mark or imprint – what Johnson calls “a disk on the sky” – in the form of a circular bruise in the cosmic microwave background. The fact that no such pattern has been found yet makes certain collision-filled models less likely. Meanwhile, his team is working to figure out what other kinds of evidence a bubble collision may leave behind. It’s the first time, they say in their paper, that anyone has produced a direct, quantitative set of predictions for observable signatures of bubble collisions. And though none of those signatures has so far been found, some of them are possible to look for.

The real significance of this work is as a proof of principle: it shows that the multiverse hypothesis can be testable. In other words, if we are living in a bubble universe, we might actually be able to tell.

And what might neighbouring alternative universes look like? Supposing there are infinite numbers of them – it may mean that anything that can happen, will happen in at least one of them. A universe may exist in which dinosaurs survived the asteroid impact. A universe may exist where you are President of the United States. A universe may exist where flowers have the ability to talk. Some universes could be subject to entirely new and different sets of physical laws, with bizarre arrangements of matter and energy. If we ever reach Type V status on the Kardashev scale, we may know for sure.

 

 

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13th July 2014

The world's first dedicated launch service for nanosatellites

A new rocket design that incorporates methane fuel can provide a low-cost platform for launching clusters of tiny satellites, greatly improving broadband delivery and Earth observation missions.

 

nanosatellites
A cluster of tiny "CubeSats" is shown in this image photographed by a crew member on the International Space Station.

 

Firefly Space Systems, a small satellite launch company, has officially announced its first launch vehicle, “Firefly Alpha.” This efficient, brand new rocket, capable of carrying 400kg (882lb) into low earth orbit, will be the world’s first dedicated light satellite launch vehicle in this mass class.

Following its launch and seed funding in January, the company – which includes highly experienced aerospace engineers from SpaceX and Virgin Galactic – has aggressively moved forward in its goal to reduce the prohibitively high costs of small satellite launches. Clusters of these micro and nanosatellites placed in low orbit could revolutionise broadband data delivery and Earth observation missions, among other uses. CubeSats like those pictured above are only a litre (10 cm cube) in volume, with masses of little more than a kilogram (2.2lb), typically using off-the-shelf components for their electronics.

“What used to cost hundreds of millions of dollars is rapidly becoming available in the single digit millions,” said Firefly CEO Thomas Markusic. “We are offering small satellite customers the launch they need for a fraction of that, around $8 or 9 million – the lowest cost in the world. It’s far cheaper than the alternatives, without the headaches of a multi manifest launch.”

Simplified and optimised for least cost – and utilising innovations such as a more aerodynamic engine design – Firefly has positioned itself to be a technological and cost effective solution for traditional manufacturers of small satellites.

“To say that this is an exciting and significant technological milestone would be an understatement,” said Michael Blum, co-founder of Firefly. “Until now, there existed virtually no dedicated launcher capacity in the small satellite industry to deliver their respective payloads to orbit. This announcement today just changed all that.”

 

 

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11th July 2014

Astronomers discover the most distant Milky Way stars detected to date

The boundaries of our home galaxy may have to be redrawn, as two stars have been found orbiting the Milky Way at distances of 775,000 and 900,000 light-years from Earth, respectively.

 

milky way and distant star
This simulated image demonstrates how large the Milky Way would look from ULAS J0744+25, nearly 775,000 light years away.

 

The distant outskirts of the Milky Way harbour valuable clues for understanding the formation and evolution of our galaxy.  Yet, due to overwhelming distances and an extremely sparse population of stars, few objects have been identified beyond 400,000 light years, with only seven stars known to date beyond this limit.

Recently, a team of astronomers led by John Bochanski, an assistant professor at Haverford College, began targeting stars in the Milky Way’s outer halo – a sparse shroud of stars that surrounds the disk of our galaxy and stretches to at least 500,000 light years away. The team has now discovered two stars in this halo that are the most distant ever discovered in our galaxy.

On 3rd July, Bochanski and his team, which includes Associate Professor of Astronomy Beth Willman, published a letter in Astrophysical Journal Letters, detailing the discovery of two cool red giants, ULAS J0744+25 and ULAS J0015+01.  These stars are extremely far away, at distances of 775,000 and 900,000 light years, respectively. The giant stars were selected from observations in the UKIRT Infrared Deep Sky Survey and Sloan Digital Sky Survey.

Red giant stars are relatively rare when compared to nearby cool red dwarfs, which vastly outnumber giants. Yet giants are nearly 10,000 times brighter than dwarfs, making them visible even at huge distances. Using a combination of filters highlighting different parts of the optical and near-infrared light from these giants, the team was able to identify cool red giant candidates. The scientists then obtained spectroscopic confirmation of the identity of these stars using the 6.5m telescope at the MMT Observatory on Mt. Hopkins in Arizona.

“It really is like looking for a needle in a haystack,” Bochanski says.  “Except our haystack is made up of millions of red dwarf stars.”

During a visit last November to the MMT Observatory, Bochanski and his team observed ULAS J0744+25 and ULAS J0015+01, using a variety of methods to estimate the distances to these stars. Every method pointed to the same conclusion: these stars are extremely far away. They are over 50 percent farther from the Sun than any known star in the Milky Way, or about five times more distant than the Large Magellanic Cloud. In fact, they lie one-third of the distance to the Andromeda Galaxy, the Milky Way’s sister spiral in the Local Group.

 

Click to enlarge

local group
By Andrew Z. Colvin (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0), via Wikimedia Commons

 

“The distances to these two stars are almost too large to comprehend,” adds Bochanski. “To put it in perspective, when the light from ULAS J0015+01 left the star, our early human ancestors were just starting to make fires here on Earth.”

“It is remarkable to find stars this far out in the Milky Way galaxy," remarked Daniel Evans, lead for Individual Investigator Programs at NSF's Division of Astronomical Sciences, which funded the research. “These results will undoubtedly shed new light on the formation and evolution of our galactic home.”

The significance of these stars goes beyond their record-holding distances because they inhabit the Milky Way’s halo. Some astronomers believe the halo is like a cloud of galactic crumbs, a result of the Milky Way’s merger with many smaller galaxies over our galaxy’s lifetime, says Beth Willman, co-author of the study: “Theory predicts the presence of such an extended stellar halo, formed by destroyed remains of small dwarf galaxies that merged over the cosmic ages to form the Milky Way itself. The properties of cool red giants in the halo thus preserve the formation history of our Milky Way. These stars are truly ghosts of galaxies past.”

By assembling a larger sample of distant red giants, Bochanski and his team hope to test model predictions for the Milky Way's formation. Their results may already be putting some of these models to the test. “Most models don’t predict many stars at these distances,” says Bochanski. “If more distant red giants are discovered, the models may need to be revised.” The search in the outer reaches of our Milky Way goes on, using the brightest stars to guide the way.

 

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4th July 2014

Ocean inside Titan could be as salty as the Dead Sea

Scientists analysing data from NASA's Cassini mission have firm evidence the ocean inside Saturn's largest moon, Titan, might be as salty as Earth's Dead Sea.

 

Titan

 

The new results come from a study of gravity and topography data collected during Cassini's repeated flybys of Titan during the past 10 years. Using the Cassini data, researchers presented a model structure for Titan, resulting in an improved understanding of the structure of the moon's outer ice shell. The findings are published in this week's edition of the journal Icarus.

"Titan continues to prove itself as an endlessly fascinating world, and with our long-lived Cassini spacecraft, we're unlocking new mysteries as fast as we solve old ones," said Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory in California.

Additional findings support previous indications the moon's icy shell is rigid and in the process of freezing solid. Researchers found that a relatively high density was required for Titan's ocean in order to explain the gravity data. This indicates the ocean is probably an extremely salty brine of water mixed with dissolved salts likely composed of sulfur, sodium and potassium. The density indicated for this brine would give the ocean a salt content roughly equal to the saltiest bodies of water on Earth.

 

dead sea
The Dead Sea, Israel

 

"This is an extremely salty ocean by Earth standards," said the paper's lead author, Giuseppe Mitri of the University of Nantes in France. "Knowing this may change the way we view this ocean as a possible abode for present-day life, but conditions might have been very different there in the past."

Cassini data also indicate the thickness of Titan's ice crust varies slightly from place to place. The researchers said this can best be explained if the moon's outer shell is stiff, as would be the case if the ocean were slowly crystalizing and turning to ice. Otherwise, the moon's shape would tend to even itself out over time, like warm candle wax. This freezing process would have important implications for the habitability of Titan's ocean, as it would limit the ability of materials to exchange between the surface and the ocean.

A further consequence of a rigid ice shell, according to the study, is that any outgassing of methane into Titan's atmosphere must happen at scattered "hot spots" – like the hot spot on Earth that gave rise to the Hawaiian Island chain. Titan's methane does not appear to result from convection or plate tectonics recycling its ice shell.

How methane gets into the moon's atmosphere has long been of great interest to researchers, as molecules of this gas are broken apart by sunlight on short geological timescales. Titan's present atmosphere contains about five percent methane. This means some process, thought to be geological in nature, must be replenishing the gas. The study indicates that whatever process is responsible, the restoration of Titan's methane is localised and intermittent.

"Our work suggests looking for signs of methane outgassing will be difficult with Cassini, and may require a future mission that can find localised methane sources," said Jonathan Lunine, a scientist on the Cassini mission at Cornell University, Ithaca, New York, and one of the paper's co-authors. "As on Mars, this is a challenging task."

 

titan earth moon
Size comparison of Titan (lower left), Earth and the Moon.

 

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17th June 2014

Hubble to search beyond Pluto for a New Horizons mission target

After careful consideration and analysis, a committee has recommended using Hubble to search for an object the New Horizons mission could visit after its flyby of Pluto in July 2015.

 

new horizons pluto 2015 mission

 

The planned search will involve targeting a small area of sky to find a Kuiper Belt object (KBO) for the outbound spacecraft to visit. The Kuiper Belt is a vast debris field of icy bodies left over from the solar system's formation 4.6 billion years ago. A KBO has never been seen up close because the belt is so far from the Sun, stretching out to a distance of 5 billion miles into a never-before-visited frontier of the solar system.

"I am pleased that our science peer-review process arrived at a consensus as to how to effectively use Hubble's unique capabilities to support the science goals of the New Horizons mission," said Matt Mountain, director of the Space Telescope Science Institute (STScI) in Baltimore, Maryland.

With ground-based telescopes, the team estimates they have only a 40 per cent chance of identifying a suitable KBO target. With access to the Hubble Space Telescope, however, they will have a greater than 90 percent chance. The space telescope will scan an area of sky in the direction of the constellation Sagittarius to try and identify any objects orbiting within the Kuiper Belt. To discriminate between a foreground KBO and the clutter of background stars, the observatory will turn at the predicted rate that KBOs are moving against the background stars. In the resulting images, the stars will be streaked, but any KBOs should appear as pinpoint objects.

If the initial test observation identifies at least two KBOs of specified brightness, it will demonstrate statistically that Hubble has a chance of finding an appropriate KBO for New Horizons to visit. At that point, an additional allotment of observing time will continue the search across a field of view roughly the angular size of the full Moon.

 

kuiper belt

 

Astronomers around the world apply for observing time on Hubble. Competition for use of the telescope is extremely intense and the requested time significantly exceeds the available time in a given year. Proposals must address significant astronomical questions that can only be answered with Hubble's unique capabilities and are beyond the capabilities of ground-based telescopes. The proposals are peer reviewed by an expert committee, which looks for the best possible science that can be conducted by Hubble and recommends to the STScI director a balanced program of small, medium, and large investigations.

Though Hubble is powerful enough to see galaxies near the horizon of the universe, finding a KBO is a challenging needle-in-haystack search. A typical KBO along the New Horizons' trajectory may be no larger than Manhattan Island and as black as charcoal.

Even before the launch of New Horizons in 2006, Hubble has provided consistent support for this edge-of-the-solar system mission. Hubble was used to discover four small moons orbiting Pluto and its binary companion Charon, providing new targets to enhance the mission's scientific return. Hubble has also provided the most sensitive search yet for potentially hazardous dust rings around Pluto, along with a map of the surface, which astronomers are using to plan New Horizons' close-up photos.

 

pluto surface
Artist's impression of Pluto's surface and its largest moon Charon, with our Sun in the top right.

 

In addition to Pluto exploration, recent Hubble solar system observations have discovered a new satellite around Neptune, probed the magnetospheres of the gas giants, found circumstantial evidence for oceans on Europa, and uncovered several bizarre cases of asteroids disintegrating before our eyes. Hubble has supported numerous NASA Mars missions by monitoring the Red Planet's seasonal atmospheric changes. Hubble has made complementary observations in support of the Dawn asteroid mission, and comet flybys. Nearly 20 years ago, in July 1994, Hubble documented the never-before-seen string of comet collisions with Jupiter that resulted from the tidal breakup of comet Shoemaker-Levy 9.

"The planned search for a suitable target for New Horizons further demonstrates how Hubble is effectively being used to support humankind's initial reconnaissance of the solar system," said Mountain. "Likewise, it is also a preview of how the powerful capabilities of the upcoming James Webb Space Telescope will bolster planetary science. We are excited by the potential of both observatories for ongoing solar system exploration and discovery."

 

pluto new horizons orbit location
Current location of New Horizons.

 

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14th June 2014

New evidence for "oceans" of water lying deep inside the Earth

Researchers have presented new evidence indicating vast amounts of water in a transition layer below Earth's crust. Although not in liquid form, this discovery may represent the planet's single largest reservoir.

 

oceans of water in earth mantle

 

Earlier this year, a sample of the mineral ringwoodite provided strong evidence of water in huge volumes below the Earth at depths of 250 to 430 miles (400 to 700 km). Now researchers have built upon that discovery with additional findings, based on seismic wave patterns and laboratory simulations.

Geophysicist Steve Jacobsen (Northwestern University) and seismologist Brandon Schmandt (University of New Mexico) found deep pockets of magma located about 400 miles below North America – a likely signature of the presence of water at these depths. Their discovery suggests that water from Earth's surface can be driven to such great depths by plate tectonics, leading to partial melting of the rocks found deep in the mantle. The study results, published yesterday in the journal Science, will aid scientists in better understanding how the Earth formed, its current composition and inner workings and how much water is trapped in mantle rock.

"Geological processes on the Earth's surface, such as earthquakes or erupting volcanoes, are an expression of what is going on inside the Earth, out of our sight," said Jacobsen. "I think we are finally seeing evidence for a whole-Earth water cycle, which may help explain the vast amount of liquid water on the surface of our habitable planet. Scientists have been looking for this missing deep water for decades."

The study combined Jacobsen's laboratory experiments – in which mantle rock was simulated under high pressure at 400 miles below Earth's surface – with Schmandt's observations using vast amounts of seismic data from the USArray, a dense network of 2,000 seismometers across the United States. The pair's findings converged to produce evidence that melting occurs about 400 miles deep in the Earth. H2O stored in mantle rocks, such as those containing ringwoodite, is key to this process, the researchers said.

 

ringwoodite

A sample of ringwoodite, able to contain hydroxide ions (oxygen and hydrogen atoms bound together). Credit: Jasperox (CC BY 3.0)

 

"Melting of rock at this depth is remarkable because most melting in the mantle occurs much shallower, in the upper 50 miles," said Schmandt. "If there is a substantial amount of H2O in the transition zone, then some melting should take place in areas where there is flow into the lower mantle – and that is consistent with what we found."

The total amount of water is so huge that it could fill the volume of Earth's oceans three times over. It exists as neither liquid, ice nor vapour, however – but in a fourth form. The weight of 250 miles of solid rock creates such high pressure, along with temperatures of more than 1100°C (2000°F), that a water molecule splits to form a hydroxyl radical (OH), which can be trapped inside a mineral's crystal structure.

"The ringwoodite is like a sponge, soaking up water," Jacobsen says. "There is something very special about the crystal structure of ringwoodite that allows it to attract hydrogen and trap water. This mineral can contain a lot of water under conditions of the deep mantle."

The melting the researchers have detected is known as "dehydration" melting. Rocks in the transition zone can hold a lot of H2O, but rocks in the top of the lower mantle hold almost none. The water contained in ringwoodite in the transition zone is forced out when it goes deeper (into the lower mantle) and forms a higher-pressure mineral called silicate perovskite, which cannot absorb the water. This causes the rock at the boundary between the transition zone and lower mantle to partially melt.

"When a rock with a lot of H2O moves from the transition zone to the lower mantle, it needs to get rid of the H2O somehow, so it melts a little bit," Schmandt said. "This is called dehydration melting."

"Once the water is released, much of it may become trapped there in the transition zone," Jacobsen added.

 

earth layers

 

The confirmation of water in this transition zone may lend support to alternative theories about the origin of Earth's oceans. Instead of being deposited on the surface by comet impacts, it may have gradually oozed up from the interior. The hidden water could also have acted as a surface "buffer", explaining why the oceans have remained the same size for millions of years.

"We should be grateful for this deep reservoir," says Jacobsen. "If it wasn't there, it would be on the surface of the Earth, and mountain tops would be the only land poking out."

At 400 miles down, this region is far beyond the reach of current drilling technology. The deepest humans have ever drilled is 7.6 miles (12.2 km) at the Kola Superdeep Borehole in Russia. Plans have also been made to obtain samples from the mantle, by probing a particularly thin area of the crust at depths of 5 miles (8 km) in 2018. However, it will likely be many decades or even centuries before we attempt a "Journey to the centre of the Earth".

 

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5th June 2014

Astronomers discover a bizarre new type of
"hybrid" star

Astronomers have detected the first Thorne-Żytkow objects (TŻOs). These hybrids of red supergiant and neutron stars, first proposed in 1975, had been theoretical until now.

 

red giant neutron hybrid

 

In a discovery decades in the making, scientists have detected the first of a “theoretical” class of stars first proposed in 1975 by physicist Kip Thorne and astronomer Anna Żytkow. Thorne-Żytkow objects (TŻOs) are hybrids of red supergiant and neutron stars that superficially resemble normal supergiants like Betelgeuse in the constellation Orion. They differ, however, in their distinct chemical signatures resulting from unique activity in their stellar interiors.

TŻOs are thought to be formed by the interaction of two massive stars – a red supergiant and a neutron star formed during a supernova explosion – within a close binary system. While the exact mechanism is uncertain, the most commonly held theory suggests that, during the evolutionary interaction of the two stars, the much more massive red supergiant essentially swallows the neutron star, which spirals into the core of the red supergiant.

While normal supergiants derive their energy from nuclear fusion in their cores, TŻOs are powered by the unusual activity of the absorbed neutron stars in their cores. The discovery of this TŻO thus provides evidence of a model of stellar interiors previously undetected by astronomers.

Project leader Emily Levesque of the University of Colorado Boulder, who earlier this year was awarded the American Astronomical Society’s Annie Jump Cannon Award, said: “Studying these objects is exciting as it represents a completely new model of how stellar interiors can work. In these interiors we also have a new way of producing heavy elements in our universe. You’ve heard that everything is made of ‘star stuff’ – inside these stars we might now have a new way to make some of it.”

The study, published in the Monthly Notices of the Royal Astronomical Society Letters, is co-authored by Philip Massey, of the Lowell Observatory in Flagstaff, Arizona; Anna Żytkow of the University of Cambridge in the UK; and Nidia Morrell of the Carnegie Observatories in Chile. The astronomers achieved their discovery using the 6.5-metre Magellan Clay telescope on Las Campanas in Chile, pointed at the Small Magellanic Cloud, which lies about 200,000 light years away:

 

local galactic neighbourhood
Credit: Richard Powell, Atlas of the Universe

 

They examined the spectrum of light emitted from apparent red supergiants, which tells them what elements are present. When the spectrum of one particular star – HV 2112 – was first displayed, the observers were surprised by some of its unusual features. As Morrell commented: “I don’t know what this is, but I know that I like it!”

When Levesque and her colleagues looked closely at the subtle lines in the spectrum, they found it contained excess rubidium, lithium and molybdenum. Past research has shown that normal stellar processes can create each of these separate elements. But high abundances of all three at temperatures typical of red supergiants are a unique signature of TŻOs.

“I am extremely happy that observational confirmation of our theoretical prediction has started to emerge,” Żytkow said. “Since Kip Thorne and I proposed our models of stars with neutron cores, people were not able to disprove our work. If theory is sound, experimental confirmation shows up sooner or later. So it was a matter of identification of a promising group of stars, getting telescope time and proceeding with the project.”

The researchers are careful to point out that HV 2112 displays some chemical characteristics that don’t quite match theoretical models. As Massey adds: “We could, of course, be wrong. There are some minor inconsistencies between some of the details of what we found and what theory predicts. But the theoretical predictions are quite old, and there have been a lot of improvements in the theory since then. Hopefully our discovery will spur additional work on the theoretical side now.”

 

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1st June 2014

One percent of all exoplanets may be suitable for complex organisms

The number of planets on which complex life could exist in the Milky Way may be as high as 100 million, according to a study published this week by two former University of Texas at El Paso (UTEP) professors and their colleagues in the journal Challenges.

 

exoplanets dna

 

“This constitutes the first quantitative estimate of the number of worlds in our galaxy that could harbour life above the microbial level – based on objective data,” says lead author of the peer-reviewed study, Dr. Louis Irwin, Professor Emeritus and former Chair of Biological Sciences at UTEP.

Irwin and his colleagues surveyed the growing list of more than a thousand confirmed exoplanets (planets in other solar systems). Using a formula that considers planetary density, temperature, substrate (liquid, solid, or gas), chemistry, distance from its central star, and age, Irwin’s team computed a “biological complexity index (BCI)”, which rates planets on a scale of 0 to 1.0 according to the number and degree of characteristics assumed to be important for supporting multiple forms of multicellular life.

The BCI calculation revealed that 1 to 2 percent of exoplanets showed a rating higher than Europa, a moon of Jupiter thought to have a subsurface global ocean which could harbour different forms of life. Based on a very conservative estimate of 10 billion stars in the Milky Way, and assuming an average of one planet per star, this yields the figure of 100 million. It could be over 10 times higher if we consider a larger number of stars in our galaxy.

Irwin emphasized that the study does not indicate that complex life exists on that many planets, only that planetary conditions that could support it do. He also noted that complex life does not mean intelligent life (although it doesn't rule it out), or even animal life – but simply that organisms larger and more complex than microbes could exist in a number of different forms, quite likely forming stable food webs like those found in ecosystems on Earth.

 

alien life

 

“Other scientists have tried to make educated guesses about the frequency of life on other worlds based on hypothetical assumptions, but this is the first study that relies on observable data from actual planetary bodies beyond our solar system,” Irwin said.

Despite the large absolute number of planets that could harbour complex life, the Milky Way is so vast that, statistically, planets with high BCI values are very far apart. One of the closest and most promising extrasolar systems, known as Gliese 581, has possibly two planets with the apparent capacity to host complex biospheres, yet the distance from the Sun to Gliese 581 is about 20 light years. Most planets with a high BCI are much further away. If the 100 million planets that Irwin’s team says have a theoretical capacity for hosting complex life were randomly distributed across the galaxy, they would average about 24 light years apart.

 

alien landscape

 

“On the one hand,” according to Professor Irwin, “it seems highly unlikely that we are alone. On the other hand, we are likely so far away from life at our level of complexity, that a meeting with such alien forms is extremely improbable for the foreseeable future.”

Co-authors of the study include Dirk Schulze-Makuch, former Associate Professor of Geological Sciences at UTEP, now at Washington State University, Alberto Fairén of Cornell University, and Abel Méndez, of the University of Puerto Rico at Arecibo. In 2011, these same scientists were part of the team that published an “Earth Similarity Index (ESI)”, which rates exoplanets also on a scale of 0 to 1.0 according to how similar they are to Earth.

Not surprisingly, higher BCI values tend to be correlated with higher ESI values, but there are some exceptions. “Planets with the highest BCI values tend to be larger, warmer, and older than Earth,” said Irwin, “so any search for complex or intelligent life that is restricted just to Earth-like planets, or to life as we know it on Earth, will probably be too restrictive.”

The paper is available at MDPI.

 

exoplanet BCI ESI index

Biological complexity (BCI) relative to Earth similarity (ESI) for Solar System planets (orange squares) and satellites (yellow squares), and for 365 exoplanets for which BCI>0. The vast majority of exoplanets known to date are gas giants (green circles), but the ones with highest BCI values are likely rocky-water worlds (purple circles).

 

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8th May 2014

Simulation recreates universe in unprecedented detail

A realistic "virtual universe" has been created, simulating 13 billion years of cosmic evolution at both large and small scales.

 

universe

 

Researchers at MIT and the Harvard-Smithsonian Center for Astrophysics have generated the first realistic virtual universe using a computer simulation called "Illustris." This has recreated 13 billion years of cosmic evolution in a cube 350 million light years across with unprecedented resolution.

"Until now, no single simulation was able to reproduce the universe on both large and small scales simultaneously," says lead author Mark Vogelsberger who collaborated with researchers at several institutions, including the Heidelberg Institute for Theoretical Studies in Germany. The study is reported in the journal Nature.

Previous attempts to simulate the universe were hampered by a lack of computing power, along with complexities of the underlying physics. As a result, those programs were either limited in resolution, or forced to focus on a smaller portion of the universe. Earlier simulations also had trouble modelling complex feedback from star formation, supernova explosions, and supermassive black holes.

Illustris, however, employs a sophisticated computer program to recreate the evolution of the universe in high fidelity. This includes both normal matter and dark matter using 12 billion 3-D pixels.

The team dedicated five years to developing the Illustris program. The actual calculations took 3 months of "run time" – using a total of 8,000 CPUs running in parallel. If they had used an average desktop computer, the calculations would have taken over 2,000 years to complete.

 

 

The simulation began a mere 12 million years after the Big Bang. When it reached the present day, astronomers counted more than 41,000 galaxies in the cube of simulated space. Importantly, Illustris yielded a realistic mix of spiral galaxies like the Milky Way and football-shaped elliptical galaxies. It also recreated large-scale structures, like galaxy clusters, along with bubbles and voids of the cosmic web.

On the small scale, it accurately simulated the chemistries of individual galaxies. The smallest features it can model are roughly 1,000 light years across – about 1% of the Milky Way's diameter. Vogelsberger believes that 10 years from now, advances in computing power will make it possible to show features only a few light years across. Individual stars and planets would be much harder to simulate, due to the vast number of calculations required, though it should be possible eventually.

Since light travels at a fixed speed, the farther away astronomers look, the farther back in time they can see. A galaxy one billion light years away is seen as it was a billion years ago. Telescopes like Hubble can provide us with views of the early universe by looking to greater distances. However, astronomers can't use Hubble to follow the evolution of a single galaxy over time.

"Illustris is like a time machine. We can go forward and backward in time. We can pause the simulation and zoom into a single galaxy or galaxy cluster to see what's really going on," says co-author Shy Genel.

The video shown above morphs between different components of the simulation to highlight various layers – e.g. dark matter density, gas temperature and chemistry. A full resolution version is available to download here (right-click, save as). Several smaller videos and associated imagery have also been released at http://www.illustris-project.org/

 

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3rd May 2014

Length of exoplanet day measured for first time

Astronomers have measured an exoplanet's length of day for the first time. Beta Pictoris b was found to have a day that lasts only eight hours.

 

beta pictoris b exoplanet
Artist's impression of the Beta Pictoris system. Credit: ESO L. Calçada/N. Risinger (skysurvey.org)

 

Our ability to glean information from distant planets beyond our own Solar System has taken yet another step forward. Researchers at the European Southern Observatory (ESO) have, for the first time, determined the rotation rate of an exoplanet. Beta Pictoris b was found to have a day that lasts only 8.1 hours. This is much quicker than any known planet – its equator is moving at almost 100,000 kilometres per hour. For comparison, Jupiter rotates at 45,300 km/h and Earth rotates at just 1,674 km/h.

This new result extends the relation between mass and rotation seen in the Solar System to exoplanets. Similar techniques will allow astronomers to map exoplanets in detail in the future using the European Extremely Large Telescope (E-ELT).

Beta Pictoris b orbits the naked-eye star Beta Pictoris, which lies about 63 light-years away in the southern constellation of Pictor (The Painter's Easel). This planet was discovered nearly six years ago and was among the first exoplanets to be directly imaged. It orbits its host star at a distance of only eight times the Earth-Sun distance (8 AU), making it the closest exoplanet to a star ever to be directly imaged. It is 16 times larger and 3,000 times more massive than the Earth.

 

 
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beta pictoris system
Credit: ESO/A.-M. Lagrange et al.

 

Using the CRIRES instrument on the Very Large Telescope (VLT), a team of Dutch astronomers from Leiden University and the Netherlands Institute for Space Research (SRON) employed a precise technique called high-dispersion spectroscopy. This was done to split light into its constituent colours – different wavelengths on the spectrum. The principle of the Doppler effect (or Doppler shift) allowed them to use the change in wavelength to detect that different parts of the planet were moving at different speeds and in opposite directions relative to the observer. By very carefully removing the effects of the much brighter parent star, they were able to extract the rotation signal from the planet.

"We have measured the wavelengths of radiation emitted by the planet to a precision of one part in a hundred thousand, which makes the measurements sensitive to the Doppler effects that can reveal the velocity of emitting objects," says lead author Ignas Snellen. "Using this technique we find that different parts of the planet's surface are moving towards or away from us at different speeds, which can only mean that the planet is rotating around its axis."

The fast spin of Beta Pictoris b means that in the future, it will be possible to make a global map of the planet, and others, showing cloud patterns and large storms: "This technique can be used on a much larger sample of exoplanets with the superb resolution and sensitivity of the E-ELT and an imaging high-dispersion spectrograph. With the planned Mid-infrared E-ELT Imager and Spectrograph (METIS) we will be able to make global maps of exoplanets and characterise much smaller planets than Beta Pictoris b with this technique", says co-author, Bernhard Brandl.

Beta Pictoris b is a very young planet, only about 20 million years old (compared to 4.5 billion years for Earth). Over time, it is expected to cool and shrink – making it spin even faster. On the other hand, other processes might be at play that change the spin of the planet. For instance, the spin of the Earth is slowing down over time due to the tidal interactions with our Moon.

 

 

Planet rotation speeds compared

Diameters are shown to scale

 

Earth Jupiter Beta Pictoris b

 

Earth

24 hours

 

 

Jupiter

10 hours

 

 

Beta Pictoris b

8 hours

 

GIF animations by Will Fox

 

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23rd April 2014

Asteroid impacts are more common than previously thought

The B612 Foundation has released a video showing evidence of 26 multi-kiloton asteroid impacts since 2001.

 

 

 

At a press conference yesterday at the Seattle Museum of Flight, three prominent astronauts supporting the B612 Foundation presented a visualisation of new data showing the surprising frequency at which the Earth is hit by asteroids. The astronauts were guests of the Seattle Museum for a special series of public events on Earth Day 2014.

Dr. Ed Lu, former US Shuttle and Soyuz Astronaut and co-founder and CEO of the B612 Foundation was joined by former NASA Astronaut Tom Jones, President of the Association of Space Explorers and Apollo 8 Astronaut Bill Anders, first Chairman of the Nuclear Regulatory Commission. They discussed findings recently released from the Nuclear Test Ban Treaty Organisation, which operates a network of sensors that monitors Earth around the clock listening for the infrasound signature of nuclear detonations.

Between 2000 and 2013, this network detected 26 explosions on Earth ranging in energy from 1 to 600 kilotons – all caused not by nuclear explosions, but rather by asteroid impacts. To put that in perspective, the atomic bomb that destroyed Hiroshima in 1945, exploded with an energy of 15 kilotons. While most of these asteroids exploded too high in the atmosphere to do serious damage on the ground, the evidence is important in estimating the frequency of a potential "city-killer-size" asteroid.

The Earth is continuously colliding with fragments of asteroids, the largest in recent times exploding over Tunguska, Siberia in 1908 with an energy impact of 5-15 megatons. More recently, we witnessed the 600-kiloton impact in Chelyabinsk, Russia in 2013, and impacts greater than 20 kilotons occurred in South Sulawesi, Indonesia in 2009, in the Southern Ocean in 2004, and in the Mediterranean Sea in 2002. Important to note as well is the fact that none of these asteroids were detected or tracked in advance by any existing space-based or terrestrial observatory.

"While most large asteroids with the potential to destroy an entire country or continent have been detected, less than 10,000 of the more than a million dangerous asteroids with the potential to destroy an entire major metropolitan area have been found by all existing space or terrestrially-operated observatories," stated Dr. Lu. "Because we don't know where or when the next major impact will occur, the only thing preventing a catastrophe from a 'city-killer' sized asteroid has been blind luck."

The B612 Foundation aims to change that by building the Sentinel Space Telescope Mission, an early warning infrared space telescope for tracking asteroids that would provide many years to deflect an asteroid when it is still millions of miles away. The B612 Sentinel Mission will be the world's first privately funded deep space mission that will create the first comprehensive, dynamic map of our inner Solar System, identifying the current and future locations and trajectories of Earth crossing asteroids. Sentinel will detect and track over 200,000 asteroids in just the first year of operation, after a planned launch in 2018. The spacecraft will be operational until 2024.

 

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17th April 2014

First Earth-sized exoplanet orbiting within the habitable zone of another star has been confirmed

NASA has announced the discovery of Kepler 186 f, an Earth-sized exoplanet in the habitable zone of its host star, Kepler 186.

 

earth sized exoplanet in habitable zone kepler 186f
This artistic concept is the result of scientists and artists collaborating to help imagine the appearance of the Kepler-186 star system and its planets. Credit: NASA.

 

The first Earth-sized exoplanet orbiting within the habitable zone of another star has been confirmed by observations with both the W. M. Keck Observatory and the Gemini Observatory. The initial discovery, made by NASA's Kepler Space Telescope, is one of a handful of smaller planets found by Kepler and verified using large ground-based telescopes. It also confirms that Earth-sized planets do exist in the habitable zone of other stars.

"What makes this finding particularly compelling is that this Earth-sized planet, one of five orbiting this star, which is cooler than the Sun, resides in a temperate region where water could exist in liquid form," says Elisa Quintana of the SETI Institute and NASA Ames Research Centre, who led the paper published in the current issue of the journal Science. The region in which this planet orbits its star is called the habitable zone, as it is thought that life would most likely form on planets with liquid water.

Steve Howell, Kepler's Project Scientist and a co-author on the paper, adds that neither Kepler (nor any telescope) is currently able to directly spot exoplanets of this size and proximity to their host star. "However, what we can do is eliminate essentially all other possibilities, so the validity of these planets is really the only viable option."

With such a small host star, the team employed a technique that eliminated the possibility that either a background star or a stellar companion could be mimicking what Kepler detected. To do this, they obtained extremely high spatial resolution observations from the eight-metre Gemini North telescope on Mauna Kea in Hawaii, using a technique called speckle imaging, as well as adaptive optics (AO) observations from the ten-metre Keck II telescope, Gemini's neighbour on Mauna Kea. Together, these data allowed the team to rule out sources close enough to the star's line-of-sight to confound the Kepler evidence, and conclude that Kepler's detected signal has to be from a small planet transiting its host star.

"The Keck and Gemini data are two key pieces of this puzzle," says Quintana. "Without these complementary observations, we wouldn't have been able to confirm this Earth-sized planet."

The Gemini "speckle" data directly imaged the system, zooming to within about 400 million miles (about 4 AU, approximately equal to the orbit of Jupiter in our Solar System) of the host star and confirming there were no other stellar-sized objects orbiting within this radius from the star. Augmenting this, Keck AO observations probed a larger region around the star but to fainter limits. According to Quintana, "These Earth-sized planets are extremely hard to detect and confirm, and now that we've found one, we want to search for more. Gemini and Keck will no doubt play a large role in these endeavours."

 

exoplanet scale diagram

 

The host star, Kepler-186, is an M1-type dwarf star relatively close to our Solar System at 500 light years and in the constellation of Cygnus. The star is very dim, being over half a million times fainter than the faintest stars we can see with the naked eye. Five small planets have been found orbiting it – four of which are in very short-period orbits and are very hot. The planet designated Kepler-186f, however, is Earth-sized and orbits within the star's habitable zone. The Kepler evidence for this planetary system comes from the detection of planetary transits. These transits can be thought of as tiny eclipses of the host star by a planet (or planets) as seen from the Earth. When such planets block part of the star's light, its total brightness diminishes. Kepler detects that as a variation in the star's total light output and evidence for planets. So far, more than 3,800 candidate planets have been detected by this method with Kepler.

The Gemini data utilised the Differential Speckle Survey Instrument (DSSI) on the Gemini North telescope. DSSI is a visiting instrument developed by a team led by Howell who adds, "DSSI on Gemini rocks! With this combination, we can probe down into this star system to a distance of about 4 times that between the Earth and the Sun. It's simply remarkable that we can look inside other solar systems." DSSI works on a principle that utilises multiple short exposures of an object to capture and remove the noise introduced by atmospheric turbulence producing images with extreme detail.

Observations with the W.M. Keck Observatory used the Natural Guide Star Adaptive Optics system with the NIRC2 camera on the Keck II telescope. NIRC2 (the Near-Infrared Camera, second generation) works in combination with the Keck II adaptive optics system to obtain very sharp images at near-infrared wavelengths, achieving spatial resolutions comparable to or better than those achieved by the Hubble Space Telescope at optical wavelengths. NIRC2 is probably best known for helping to provide definitive proof of a central massive black hole at the centre of our galaxy. Astronomers also use NIRC2 to map surface features of Solar System bodies, detect planets orbiting other stars, and study detailed morphology of distant galaxies.

"Observations from Keck and Gemini, combined with other data and numerical calculations, allowed us to be 99.98% confident that Kepler-186f is real," says Thomas Barclay, Kepler scientist and co-author on the paper. "Kepler started this story, and Gemini and Keck helped close it," he adds.

 

 

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27th March 2014

First ring system around asteroid

Astronomers have discovered the first ring system around an asteroid.

 

asteroid with ring
Credit: ESO/L. Calçada/M. Kornmesser/Nick Risinger

 

Observations at many sites in South America, including ESO's La Silla Observatory, have made the surprise discovery that the remote asteroid Chariklo is surrounded by two dense and narrow rings. This is the smallest object by far found to have rings and only the fifth body in the Solar System — after the much larger planets Jupiter, Saturn, Uranus and Neptune — to have this feature. The origin of these rings remains a mystery, but they may be the result of a collision that created a disc of debris.

The rings of Saturn are one of the most spectacular sights in the sky, and less prominent rings have also been found around the other giant planets. Despite many careful searches, no rings had been found around smaller objects orbiting the Sun in the Solar System. Now observations of the distant minor planet (10199) Chariklo as it passed in front of a star have shown that this object too is surrounded by two fine rings.

"We weren't looking for a ring and didn't think small bodies like Chariklo had them at all, so the discovery — and the amazing amount of detail we saw in the system — came as a complete surprise!" says Felipe Braga-Ribas (Observatório Nacional/MCTI, Rio de Janeiro, Brazil) who planned the observation campaign and is lead author on the new paper.

 

asteroid with ring
Credit: ESO/L. Calçada/M. Kornmesser/Nick Risinger

 

Chariklo is the largest member of a class known as the Centaurs and it orbits between Saturn and Uranus in the outer Solar System. Predictions had shown that it would pass in front of the star UCAC4 248-108672 on 3 June 2013, as seen from South America. Astronomers using telescopes at seven different locations, including the 1.54-metre Danish and TRAPPIST telescopes at ESO's La Silla Observatory in Chile, were able to watch the star apparently vanish for a few seconds as its light was blocked by Chariklo — an occultation.

But they found much more than they were expecting. A few seconds before, and again a few seconds after the main occultation there were two further very short dips in the star's apparent brightness. Something around Chariklo was blocking the light. By comparing what was seen from different sites the team could reconstruct not only the shape and size of the object itself but also the shape, width, orientation and other properties of the newly discovered rings.

The team found that the ring system consists of two sharply confined rings only seven and three kilometres wide, separated by a clear gap of nine kilometres — around a small 250-kilometre diameter object orbiting beyond Saturn.

"For me, it was quite amazing to realise that we were able not only to detect a ring system, but also pinpoint that it consists of two clearly distinct rings," adds Uffe Gråe Jørgensen (Niels Bohr Institute, University of Copenhagen, Denmark), one of the team. "I try to imagine how it would be to stand on the surface of this icy object — small enough that a fast sports car could reach escape velocity and drive off into space — and stare up at a 20-kilometre wide ring system 1000 times closer than the Moon."

 

asteroid ring and sun
Credit: ESO/L. Calçada/Nick Risinger

 

Although many questions remain unanswered, astronomers think that this sort of ring is likely to be formed from debris left over after a collision. It must be confined into the two narrow rings by the presence of small putative satellites.

"So, as well as the rings, it's likely that Chariklo has at least one small moon still waiting to be discovered," adds Felipe Braga Ribas.

The rings may prove to be a phenomenon that might in turn later lead to the formation of a small moon. Such a sequence of events, on a much larger scale, may explain the birth of our own Moon in the early days of the Solar System, as well as the origin of many other satellites around planets and asteroids.

The leaders of this project are provisionally calling the rings by the nicknames Oiapoque and Chuí, two rivers near the northern and southern extremes of Brazil.

 

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