Exoplanets – worlds of other suns

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New exoplanet detected with the ESPRESSO spectrograph

by Tomasz Nowakowski , Phys.org
https://phys.org/news/2022-11-exoplanet ... graph.html
Using the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO), astronomers from Switzerland and Austria have discovered a new alien world. The newfound exoplanet orbits a nearby M dwarf star and is at least four times more massive than the Earth. The finding is reported in a paper published October 23 on arXiv.org.

ESPRESSO is the state-of-the-art ultra-stable high resolution spectrograph installed at the Very Large Telescope (VLT) in Chile, covering the spectral range from about 380 nm to 788 nm. The instrument is able to reach a precision allowing it to detect Earth-like planets around sun-like stars.

A team of astronomers led by Lia F. Sartori of the Swiss Federal Institute of Technology in Zürich, Switzerland, is conducting a blind ESPRESSO radial velocity search for planets around nearby stars. One of their targets was L 363-38—an M dwarf located some 33.3 light years away. They monitored this star between December 12, 2020 and February 08, 2022, obtaining a total of 31 observations, which resulted in the detection of a new planet.

"In the following we report the detection and characterization of a planet orbiting the nearby M dwarf star L 363-38. This is one of the few standalone planet discoveries with ESPRESSO so far," the researchers wrote in the paper.

The newly detected planet, designated L 363-38 b, has a minimum mass of about 4.67 Earth masses and its radius is estimated to be between 1.55 and 2.75 Earth radii. The exoplanet orbits its host every 8.78 days, at a distance of some 0.048 AU from it, therefore inside the inner edge of the habitable zone. The equilibrium temperature of L 363-38 b was calculated to be approximately 330 K.
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Many planets could have atmospheres rich in helium, study finds
https://phys.org/news/2022-11-planets-a ... elium.html
by Louise Lerner, University of Chicago
For centuries, no one knew if we were alone in the universe—or if there were even other planets like ours.

But thanks to new telescopes and methods in the past decades, we now know there are thousands and thousands of planets out there circling faraway stars, and they come in all sorts of shapes and sizes—large and small, rocky and gaseous, cloudy or icy or wet.

A study by scientists with the University of Chicago, the University of Michigan and the University of Maryland suggests another for the list: planets with helium atmospheres. Moreover, the discovery may suggest a new step in our understanding of planet evolution.

Their simulations found that it's likely that helium would build up in the atmospheres of certain types of exoplanets over time. If confirmed, this would explain a decades-long puzzle about the sizes of these exoplanets.

"There are so many weird and wonderful kinds of exoplanets out there, and this finding not only adds a new kind but may have implications for understanding the evolution and formation of planets in general," said University of Chicago astrophysicist Leslie Rogers, a co-author of the new paper published in Nature Astronomy.

Mystery of the radius valley

It took us so long to find faraway planets because even the biggest are far outshone by the stars they orbit. So scientists came up with an ingenious way to spot them: by looking for the dip in the light of a star as a planet passes in front of it. This tells you how large the planet is.

Now we know planets are incredibly common. In fact, from what we can tell so far, at least half of all stars like our sun have at least one planet between the size of Earth and Neptune that orbits very close to the star. It's hypothesized these planets have atmospheres with a lot of hydrogen and helium, collected when the planets first formed out of gas and dust around the star.
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“Hell Planet” Orbits Its Sun Every 17.5 Hours
by Jim Shelton
December 9, 2022

Introduction:
(Futurity) New technology has helped astronomers follow the fiery trail of the so-called “hell planet.”

It’s an exoplanet located 40 light years from Earth and nicknamed for its extremely close orbit to its sun.

Debra Fischer, a professor of astronomy at Yale University, developed the instrument that enabled the work, which is housed at the Lowell Observatory’s Lowell Discovery Telescope in Arizona.

The EXtreme PREcision Spectrometer (EXPRES), has captured ultra-precise measurements of the starlight from the distant planet’s sun. Astronomers have now analyzed those measurements to determine the orbit of planet 55 Cnc e.

55 Cnc e, which was discovered in 2004, is so hot (roughly 3,600 degrees Fahrenheit) that its surface is an ocean of lava.
Read more here: https://www.futurity.org/hell-planet-orbit-2843032/
Don't mourn, organize.

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Two Temperate Earth-mass Planets Orbiting The Nearby Star GJ1002
By Keith Cowing
https://astrobiology.com/2022/12/two-te ... j1002.html
December 14, 2022

Filed under astro-ph.EP, CARMENES, ESPRESSO, exoplanet, extrasolar, GJ~1002, Habitable Zone, M5.5~V, Spectrograph, TESS
Two Temperate Earth-mass Planets Orbiting The Nearby Star GJ1002
Two-planet model. Top panels: Combined FWHM time series of ESPRESSO and CARMENES with the best fit model. The right panel shows a zoom to the latest ESPRESSO campaign. Middle panels: Combined RV time series of ESPRESSO and CARMENES with the best fit of the GP+2p model. The red line shows the best combined model, while the grey line shows the stellar activity component. Bottom panels: Residuals after the fit of the RV time series of ESPRESSO and CARMENES. The right panel shows the GLS periodogram of the residuals. The computation of the periodogram uses the offsets and the jitters estimated for model 2-Planets (Circ) in table B.1. — astro-ph.EP

We report the discovery and characterisation of two Earth-mass planets orbiting in the habitable zone of the nearby M-dwarf GJ~1002 based on the analysis of the radial-velocity (RV) time series from the ESPRESSO and CARMENES spectrographs.
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Alien planet found spiraling to its doom around an aging star
https://phys.org/news/2022-12-alien-pla ... aging.html
by Harvard-Smithsonian Center for Astrophysics

For the first time, astronomers have spotted an exoplanet whose orbit is decaying around an evolved, or older, host star. The stricken world appears destined to spiral closer and closer to its maturing star until collision and ultimate obliteration.

The discovery offers new insights into the long-winded process of planetary orbital decay by providing the first look at a system at this late stage of evolution.

Death-by-star is a fate thought to await many worlds and could be the Earth's ultimate adios billions of years from now as our Sun grows older.

"We've previously detected evidence for exoplanets inspiraling toward their stars, but we have never before seen such a planet around an evolved star," says Shreyas Vissapragada, a 51 Pegasi b Fellow at the Center for Astrophysics | Harvard & Smithsonian and lead author of a new study describing the results. "Theory predicts that evolved stars are very effective at sapping energy from their planets' orbits, and now we can test those theories with observations."

The findings were published Monday in The Astrophysical Journal Letters.

The ill-fated exoplanet is designated Kepler-1658b. As its name indicates, astronomers discovered the exoplanet with the Kepler space telescope, a pioneering planet-hunting mission that launched in 2009. Oddly enough, the world was the very first new exoplanet candidate Kepler ever observed. Yet it took nearly a decade to confirm the planet's existence, at which time the object entered Kepler's catalogue officially as the 1658th entry.
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Kepler-80 Revisited: Assessing the Participation of a Newly Discovered Planet in the Resonant Chain
https://arxiv.org/abs/2212.08695
In this paper, we consider the chain of resonances in the Kepler-80 system and evaluate the impact that the additional member of the resonant chain discovered by Shallue & Vanderburg (2018) has on the dynamics of the system and the physical parameters that can be recovered by a fit to the transit timing variations (TTVs). Ultimately, we calculate the mass of Kepler-80 g to be 0.8±0.3M⊕ when assuming all planets have zero eccentricity, and 1.0±0.3 M⊕ when relaxing that assumption. We show that the outer five planets are in successive three-body mean-motion resonances (MMRs). We assess the current state of two-body MMRs in the system and find that the planets do not appear to be in two-body MMRs. We find that while the existence of the additional member of the resonant chain does not significantly alter the character of the Kepler-80 three-body MMRs, it can alter the physical parameters derived from the TTVs, suggesting caution should be applied when drawing conclusions from TTVs for potentially incomplete systems. We also compare our results to those of MacDonald et al. (2021), who perform a similar analysis on the same system with a different method. Although the results of this work and MacDonald et al. (2021) show that different fit methodologies and underlying assumptions can result in different measured orbital parameters, the most secure conclusion is that which holds true across all lines of analysis: Kepler-80 contains a chain of planets in three-body MMRs but not in two-body MMRs.
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NASA Discovers Pair of Super-Earths With 1,000-Mile-Deep Oceans
Earth and Exoplanet Kepler-138 d Cross-Sections
https://scitechdaily.com/nasa-discovers ... ceans/amp/
NASA’s Hubble and Spitzer Find Two Exoplanets May Be Mostly Water

In the 1995 post-apocalyptic action film “Waterworld” Earth’s polar ice caps have completely melted, and the sea level has risen to over 5 miles, covering nearly all of the land. Astronomers have uncovered a pair of planets that are true “water worlds,” unlike any planet found in our solar system.

Slightly larger than Earth, they don’t have the density of rock. And yet, they are denser than the gas-giant outer planets orbiting our Sun. So, what are they made of? The best answer is that these exoplanets have global oceans at least 500 times deeper than the average depth of Earth’s oceans, which simply are a wet veneer on a rocky ball.

The soggy worlds orbit the red dwarf star Kepler-138, located 218 light-years away in the constellation Lyra. The planets were found in 2014 with NASA’s Kepler Space Observatory. Follow-up observations with the Spitzer and Hubble space telescopes found that the planets must be composed largely of water. The spectral signature of water wasn’t directly observed. But this conclusion is based on their density, which is calculated from comparing their size and mass.
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NASA's TESS discovers planetary system's second Earth-size world

https://phys.org/news/2023-01-nasa-tess ... world.html
by Jeanette Kazmierczak, NASA's Goddard Space Flight Center
Using data from NASA's Transiting Exoplanet Survey Satellite, scientists have identified an Earth-size world, called TOI 700 e, orbiting within the habitable zone of its star—the range of distances where liquid water could occur on a planet's surface. The world is 95% Earth's size and likely rocky.

Astronomers had previously discovered three planets in this system, called TOI 700 b, c, and d. Planet d also orbits in the habitable zone. But scientists needed an additional year of TESS observations to discover TOI 700 e.

"This is one of only a few systems with multiple, small, habitable-zone planets that we know of," said Emily Gilbert, a postdoctoral fellow at NASA's Jet Propulsion Laboratory in Southern California who led the work. "That makes the TOI 700 system an exciting prospect for additional follow up. Planet e is about 10% smaller than planet d, so the system also shows how additional TESS observations help us find smaller and smaller worlds."

Gilbert presented the result on behalf of her team at the 241st meeting of the American Astronomical Society in Seattle. A paper about the newly discovered planet was accepted by The Astrophysical Journal Letters.

TOI 700 is a small, cool M dwarf star located around 100 light-years away in the southern constellation Dorado. In 2020, Gilbert and others announced the discovery of the Earth-size, habitable-zone planet d, which is on a 37-day orbit, along with two other worlds.

The innermost planet, TOI 700 b, is about 90% Earth's size and orbits the star every 10 days. TOI 700 c is over 2.5 times bigger than Earth and completes an orbit every 16 days. The planets are probably tidally locked, which means they spin only once per orbit such that one side always faces the star, just as one side of the moon is always turned toward Earth.
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