Exoplanets – worlds of other suns

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HST/WFC3 Light Curve Confirms the Closest Exoplanet to Transit an M Dwarf is Terrestrial
https://arxiv.org/abs/2307.02970

Refinement of the radius of LTT 1445 Ac, confirmation that it is indeed terrestrial.

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TESS discovers a super-Earth orbiting the M dwarf star TOI-1680
https://arxiv.org/abs/2307.05368

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Brightest known exoplanet is like 'giant mirror in space'

12th July 2023

The highest albedo ever observed for an exoplanet has been confirmed using the CHEOPS space telescope. The ultra-hot Neptune LTT 9779 b reflects 80% of incoming light from its star, due to the high metal content of its clouds.

https://www.futuretimeline.net/blog/202 ... 9779-b.htm

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New study reveals NASA's Roman could find 400 Earth-mass rogue planets
https://phys.org/news/2023-07-reveals-n ... rogue.html
by NASA's Goddard Space Flight Center

New research by scientists from NASA and Japan's Osaka University suggests that rogue planets—worlds that drift through space untethered to a star—far outnumber planets that orbit stars. The results imply that NASA's Nancy Grace Roman Space Telescope, set to launch by May 2027, could find a staggering 400 Earth-mass rogue worlds. Indeed, this new study has already identified one such candidate.

"We estimate that our galaxy is home to 20 times more rogue planets than stars—trillions of worlds wandering alone," said David Bennett, a senior research scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and a co-author of two papers describing the results. "This is the first measurement of the number of rogue planets in the galaxy that is sensitive to planets less massive than Earth."

The team's findings stem from a nine-year survey called MOA (Microlensing Observations in Astrophysics), conducted at the Mount John University Observatory in New Zealand. Microlensing events occur when an object such as a star or planet comes into near-perfect alignment with an unrelated background star from our vantage point.

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Two additional exoplanets detected in a nearby planetary system
https://phys.org/news/2023-07-additiona ... etary.html
by Tomasz Nowakowski , Phys.org

By conducting radial velocity (RV) follow-up observations of the GJ 367 planetary system with the High Accuracy Radial velocity Planet Searcher (HARPS), an international team of astronomers has detected two additional alien worlds, at least four times as massive as the Earth. The finding was reported July 18 on the pre-print server arXiv.

Located some 30.7 light years away, GJ 367 (also known as TOI-731 or TIC 34068865) is a bright star of spectral type M1.0 V, nearly half the size and mass of the sun. It hosts an ultra-short-period (USP) sub-Earth exoplanet, GJ 367 b, discovered in 2021. This small extrasolar world, which encircles the host star in less than eight hours, has a radius of approximately 0.72 Earth radii and its mass is estimated to be 0.55 Earth masses.

Now, a group of astronomers led by Elisa Goffo of the University of Turin in Italy, reports that GJ 367 b has two low-mass companions. The discovery is a result of an intensive radial velocity campaign conducted with the HARPS spectrograph, complemented with observations using NASA's Transiting Exoplanet Survey Satellite (TESS).

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Ethereal New Image Reveals The Birth of Giant Jupiter-Like Worlds
SPACE
30 July 2023
By MICHELLE STARR

New observations of the roiling cloud of dust around a baby star have revealed what looks like the early stages in the gestation of giant planets.

By using the Very Large Telescope and the Atacama Large Millimeter/submillimeter Array, astronomers have identified clumps in the thick material around a star named V960 Mon that could gravitationally collapse to form the seeds of planets like Jupiter.

It's a discovery that could help us better understand the formation of these huge worlds, a process shrouded in dust and mystery.

"This discovery is truly captivating as it marks the very first detection of clumps around a young star that have the potential to give rise to giant planets," says astronomer Alice Zurlo of the Universidad Diego Portales in Chile.

According to models, gas giant planets have two possible formation routes. You start with a baby star, surrounded by swirling material leftover from the star's formation. It's from these leftovers that planets are born.

More:
https://www.sciencealert.com/ethereal-n ... ike-worlds

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New exoplanet discovery builds better understanding of planet formation
https://phys.org/news/2023-08-exoplanet ... ation.html
by University of Birmingham

An international team of scientists has discovered an unusual Jupiter-sized planet orbiting a low-mass star called TOI-4860, located in the Corvus constellation.

The newly discovered gas giant, named TOI-4860 b, is an unusual planet for two reasons: Stars of such low mass are not expected to host planets like Jupiter, and the planet appears to be particularly enriched by heavy elements.

The study, led by University of Birmingham astronomers, is published today in a letter published within the Monthly Notices of the Royal Astronomical Society.

The planet was initially identified using NASA's Transiting Exoplanet Survey Satellite as a drop of brightness while transiting in front of its host star, but that data alone was insufficient to confirm that it was a planet.

The team used the SPECULOOS South Observatory, located in the Atacama Desert in Chile, to measure the planetary signal in several wavelengths and validated the planetary nature. The astronomers also observed the planet just before and after it disappeared behind its host star, noticing that there was no change in light, meaning the planet was not emitting any. Finally, the team collaborated with a Japanese group using the Subaru Telescope in Hawai'i. Together they measured the mass of the planet to fully confirm it.

Following this star and confirming its planet was the initiative of a group of Ph.D. students within the SPECULOOS project.

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Longest time-lapse footage of an exoplanet to date assembled from real data
https://phys.org/news/2023-08-longest-t ... -date.html
by Amanda Morris, Northwestern University

A Northwestern University astrophysicist has created the longest time-lapse video of an exoplanet to date.

Constructed from real data, the footage shows Beta Pictoris b—a planet 12 times the mass of Jupiter—sailing around its star in a tilted orbit. The time-lapse video condenses 17 years of footage (collected between 2003 and 2020) into 10 seconds. Within those seconds, viewers can watch the planet make about 75% of one full orbit.

"We need another six years of data before we can see one whole orbit," said Northwestern astrophysicist Jason Wang, who led the work. "We're almost there. Patience is key."

An expert in exoplanet imaging, Wang is an assistant professor of physics and astronomy in Northwestern's Weinberg College of Arts and Sciences and member of the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA). Late last year, Wang unveiled a 12-year time-lapse video (below) of a family of four exoplanets orbiting their star.

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Helium escapes from the atmosphere of a nearby exoplanet, observations find
https://phys.org/news/2023-08-helium-at ... lanet.html
by Tomasz Nowakowski , Phys.org

Astronomers from the University of Chicago and elsewhere report the detection of an outflowing helium from the atmosphere of a nearby mini-Neptune exoplanet known as TOI-2134 b. The finding was detailed in a research paper published August 3 on the pre-print server arXiv.

Atmospheric escape is a process during which atmospheric gas leaves the planet's gravitational source and disperses into space. This process fundamentally shapes the properties of exoplanets.

Observations show that atmospheric escape occurs in a few nearby exoplanet systems, from hot Jupiters to lower-mass super-Earths/mini-Neptunes. However, in hot Jupiters, the mass-loss rates are not high enough to affect their evolution, but in the case of lower mass planets, atmospheric escape drives and controls their evolution.

Exoplanets with substantial hydrogen/helium atmospheres, due to extreme irradiation levels in their atmospheres, undergo hydrodynamic atmospheric escape. It is a thermal atmospheric escape mechanism leading to the escape of heavier atoms of a planetary atmosphere through numerous collisions with lighter atoms.

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Transit Timing Variations in the three-planet system: TOI-270

Quote :
We present ground and space-based photometric observations of TOI-270 (L231-32), a system of three transiting planets consisting of one super-Earth and two sub-Neptunes discovered by TESS around a bright (K-mag=8.25) M3V dwarf. The planets orbit near low-order mean-motion resonances (5:3 and 2:1), and are thus expected to exhibit large transit timing variations (TTVs). Following an extensive observing campaign using 8 different observatories between 2018 and 2020, we now report a clear detection of TTVs for planets c and d, with amplitudes of ∼10 minutes and a super-period of ∼3 years, as well as significantly refined estimates of the radii and mean orbital periods of all three planets.
Dynamical modeling of the TTVs alone puts strong constraints on the mass ratio of planets c and d and on their eccentricities. When incorporating recently published constraints from radial velocity observations, we obtain masses of Mb=1.48±0.18M⊕, Mc=6.20±0.31M⊕ and Md=4.20±0.16M⊕ for planets b, c and d, respectively. We also detect small, but significant eccentricities for all three planets : eb=0.0167±0.0084, ec=0.0044±0.0006 and ed=0.0066±0.0020. Our findings imply an Earth-like rocky composition for the inner planet, and Earth-like cores with an additional He/H2O atmosphere for the outer two. TOI-270 is now one of the best-constrained systems of small transiting planets, and it remains an excellent target for atmospheric characterization.