Exoplanets – worlds of other suns

weatheriscool
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Re: Exoplanets – worlds of other suns

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Team finds younger exoplanets are better candidates when looking for other Earths
https://phys.org/news/2022-05-team-youn ... arths.html
by Southwest Research Institute

As the scientific community searches for worlds orbiting nearby stars that could potentially harbor life, new Southwest Research Institute-led research suggests that younger rocky exoplanets are more likely to support temperate, Earth-like climates.

In the past, scientists have focused on planets situated within a star's habitable zone, where it is neither too hot nor too cold for liquid surface water to exist. However, even within this so-called "Goldilocks zone," planets can still develop climates inhospitable to life. Sustaining temperate climates also requires a planet have sufficient heat to power a planetary-scale carbon cycle. A key source of this energy is the decay of the radioactive isotopes of uranium, thorium and potassium. This critical heat source can power a rocky exoplanet's mantle convection, a slow creeping motion of the region between a planet's core and crust that eventually melts at the surface. Surface volcanic degassing is a primary source of CO2 to the atmosphere, which helps keep a planet warm. Without mantle degassing, planets are unlikely to support temperate, habitable climates like the Earth's.
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Re: Exoplanets – worlds of other suns

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Kepler and the Behemoth: Three Mini-Neptunes in a 40 Million Year Old Association
https://arxiv.org/abs/2205.01112
Stellar positions and velocities from Gaia are yielding a new view of open cluster dispersal. Here we present an analysis of a group of stars spanning Cepheus to Hercules, hereafter the Cep-Her complex. The group includes four Kepler Objects of Interest: Kepler-1643 b (2.32±0.14 Earth-radii, 5.3 day orbital period), KOI-7368 b (2.22±0.12 Earth-radii, 6.8 days), KOI-7913 Ab (2.34±0.18 Earth-radii, 24.2 days), and Kepler-1627 Ab (3.85±0.11 Earth-radii, 7.2 days). The latter Neptune-sized planet is in part of the Cep-Her complex called the δ Lyr cluster (Bouma et al. 2022). Here we focus on the former three systems, which are in other regions of the association. Based on kinematic evidence from Gaia, stellar rotation periods from TESS, and spectroscopy, these three objects are also approximately 40 million years (Myr) old. More specifically, we find that Kepler-1643 is 46+9−7 Myr old, based on its membership in a dense sub-cluster of the complex called RSG-5. KOI-7368 and KOI-7913 are 36+10−8 Myr old, and are in a diffuse region that we call CH-2. Based on the transit shapes and high resolution imaging, all three objects are most likely planets, with false positive probabilities of 6×10−9, 4×10−3, and 1×10−4 for Kepler-1643, KOI-7368, and KOI-7913 respectively. These planets demonstrate that mini-Neptunes with sizes of approximately 2 Earth radii exist at ages of 40 million years.
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Re: Exoplanets – worlds of other suns

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Dynamics of ocean worlds likely controlled by their rotation
https://phys.org/news/2022-05-dynamics- ... ation.html
by Morgan Rehnberg, American Geophysical Union
Discovering that many of the large moons in the outer solar system may host significant subsurface oceans of liquid water has been a key advance in planetary science. These moons represent some of the most promising habitats for life beyond Earth, but their hidden nature makes direct study difficult.

These oceans appear to be tens or even hundreds of kilometers deep, bounded at the top by a thick, icy shell and at the bottom by a source of geothermal heating. A key element to understanding their nature is to deduce the patterns of ocean circulation, because it is the ocean that transports heat, salt, and potential biosignatures to the surface, where they could be detected by future space missions.

Although some previous studies have simulated the dynamics of subsurface oceans, those calculations have relied on parameters that are poorly constrained by observations. In a new study published in the Journal of Geophysical Research: Planets, Bire et al pursued a novel approach by casting their simulations in terms of a dimensionless number—the natural Rossby number, which is a ratio of buoyancy flux, moon rotation rate, and ocean depth—for which observational constraints do exist.
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Re: Exoplanets – worlds of other suns

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Astronomers will train James Webb Telescope's high-precision spectrographs on two intriguing rocky exoplanets
https://phys.org/news/2022-05-astronome ... ision.html
by Space Telescope Science Institute
With its mirror segments beautifully aligned and its scientific instruments undergoing calibration, NASA's James Webb Space Telescope is just weeks away from full operation. Soon after the first observations are revealed this summer, Webb's in-depth science will begin.

Among the investigations planned for the first year are studies of two hot exoplanets classified as "super-Earths" for their size and rocky composition: the lava-covered 55 Cancri e and the airless LHS 3844 b. Researchers will train Webb's high-precision spectrographs on these planets with a view to understanding the geologic diversity of planets across the galaxy, and the evolution of rocky planets like Earth.

Super-hot super-earth 55 Cancri e

55 Cancri e orbits less than 1.5 million miles from its sun-like star (one twenty-fifth of the distance between Mercury and the sun), completing one circuit in less than 18 hours. With surface temperatures far above the melting point of typical rock-forming minerals, the day side of the planet is thought to be covered in oceans of lava.
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Re: Exoplanets – worlds of other suns

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Super-Earth exoplanet orbiting nearby star discovered
https://phys.org/news/2022-06-super-ear ... -star.html
by Tomasz Nowakowski , Phys.org
An international team of astronomers reports the discovery of a new super-Earth exoplanet orbiting a nearby M-dwarf star known as Ross 508. The newly found alien world, which received designation Ross 508 b, turns out to be at least four times more massive than our planet. The finding was detailed in a paper published May 24 on arXiv.org.

"Super-Earths" are planets more massive than Earth but not exceeding the mass of Neptune. Although the term "super-Earth" refers only to the mass of the planet, it is also used by astronomers to describe planets bigger than Earth but smaller than the so-called "mini-Neptunes" (with a radius between two to four Earth radii).

Now, astronomers led by Hiroki Harakawa of the Subaru Telescope have discovered a new planet of the super-Earth class. Using the InfraRed Doppler (IRD) instrument on the Subaru 8.2-m telescope, they conducted radial velocity (RV) measurements of Ross 508—an M dwarf of spectral type M4.5, located some 36.5 light years away.

"We showed that the M4.5 dwarf Ross 508 has a significant RV periodicity at 10.75 days with possible aliases at 1.099 and 0.913 days. This periodicity has no counterpart in photometry or stellar activity indicators, but is well-fit by a Keplerian orbit due to a new planet, Ross 508 b," the researchers explained.

The newly found exoplanet Ross 508 b has a minimum mass of four Earth masses and orbits its host every 10.75 days at a distance of about 0.053 AU from it. According to the astronomers, this indicates an orbit-averaged insolation of about 1.4 times the Earth's value, placing this planet near the inner edge of Ross 508's habitable zone.

The exact orbital eccentricity of Ross 508 b is still unknown and further studies on this could provide important information about the planet's origin. The researchers suppose that Ross 508 b may have formed beyond the snow line (about 0.16 AU) and undergone inward Type I migration. They noted that even if the eccentricity of a migrating alien world is initially high, it can be damped by the force exerted on the planet by density waves.
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Re: Exoplanets – worlds of other suns

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Re: Exoplanets – worlds of other suns

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A new third planet and the dynamical architecture of the HD33142 planetary system
Based on recently-taken and archival HARPS, FEROS and HIRES radial velocities (RVs), we present evidence for a new planet orbiting the first ascent red giant star HD33142 (with an improved mass estimate of 1.52±0.03 M⊙), already known to host two planets. We confirm the Jovian mass planets HD33142 b and c with periods of Pb = 330.0+0.4−0.4 d and Pc = 810.2+3.8−4.2 d and minimum dynamical masses of mbsini = 1.26+0.05−0.05 MJup and mcsini = 0.89+0.06−0.05 MJup. Furthermore, our periodogram analysis of the precise RVs shows strong evidence for a short-period Doppler signal in the residuals of a two-planet Keplerian fit, which we interpret as a third, Saturn-mass planet with mdsini = 0.20+0.02−0.03 MJup on a close-in orbit with an orbital period of Pd =89.9+0.1−0.1 d. We study the dynamical behavior of the three-planet system configurations with an N-body integration scheme, finding it long-term stable with the planets alternating between low and moderate eccentricities episodes. We also performed N-body simulations, including stellar evolution and second-order dynamical effects such as planet-stellar tides and stellar mass-loss on the way to the white dwarf phase. We find that planets HD33142 b, c and d are likely to be engulfed near the tip of the red giant branch phase due to tidal migration. These results make the HD33142 system an essential benchmark for the planet population statistics of the multiple-planet systems found around evolved stars.
https://arxiv.org/abs/2206.03899
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Re: Exoplanets – worlds of other suns

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TESS Hunt for Young and Maturing Exoplanets (THYME) VII : Membership, rotation, and lithium in the young cluster Group-X and a new young exoplanet
https://arxiv.org/abs/2206.06254
Quote :
The public, all-sky surveys Gaia and TESS provide the ability to identify new young associations and determine their ages. These associations enable study of planetary evolution by providing new opportunities to discover young exoplanets. A young association was recently identified by Tang et al. and F{ü}rnkranz et al. using astrometry from Gaia (called "Group-X" by the former). In this work, we investigate the age and membership of this association; and we validate the exoplanet TOI 2048 b, which was identified to transit a young, late G dwarf in Group-X using photometry from TESS. We first identified new candidate members of Group-X using Gaia EDR3 data. To infer the age of the association, we measured rotation periods for candidate members using TESS data. The clear color--period sequence indicates that the association is the same age as the 300±50 Myr-old NGC 3532. We obtained optical spectra for candidate members that show lithium absorption consistent with this young age. Further, we serendipitously identify a new, small association nearby Group-X, which we call MELANGE-2. Lastly, we statistically validate TOI 2048 b, which is 2.1±0.2 \rearth\ radius planet on a 13.8-day orbit around its 300 Myr-old host star.
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Re: Exoplanets – worlds of other suns

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Gaia DR3 is out! And we've got extrasolar planets. 215 from transit, 74 from astrometry, 10 from RV.


NAMING OF GAIA'S EXOPLANET CANDIDATES
The naming of the exoplanet candidates follows these three methods:

Astrometric detection: Gaia-ASOI-#
Photometric transit: Gaia-TROI-#
Radial velocity: Gaia-RVOI-#


Link to detected planets and candidates.
https://www.cosmos.esa.int/documents/29 ... 4699871498
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