Exoplanets – worlds of other suns

[firestar464]

A new beginning: Astronomers search for more temperate 'Tatooines'

https://phys.org/news/2024-02-astronome ... oines.html

[weatheriscool]

Observations find evidence of patchy cloud layers in the atmosphere of a nearby planetary-mass object
https://phys.org/news/2024-03-evidence- ... phere.html
by Tomasz Nowakowski , Phys.org

Astronomers have performed multi-wavelength photometric observations of a nearby planetary-mass object known as SIMP J013656.5+093347. Results of the observational campaign, presented February 22 on the pre-print server arXiv, suggest that the object hosts patchy cloud layers in its atmosphere.

Discovered in 2006, SIMP J013656.5+093347 (or SIMP0136 for short) is a highly variable planetary-mass object. Its mass is estimated to be about 12.7 Jupiter masses and its effective temperature is at a level of 1,100 K.

Previous observations of SIMP0136 have found that it has a rotation period of about 2.4 hours and a peak-to-peak J-band amplitude of approximately 50 mmag. Moreover, one study detected a highly circularly polarized pulsed radio emission in the 4-8 GHz band and a magnetic field of above 2.5 kG, suggesting the presence of aurorae on this object.

[weatheriscool]

Validation of a Third Planet in the LHS 1678 System
https://arxiv.org/abs/2403.00110

The nearby LHS 1678 (TOI-696) system contains two confirmed planets and a wide-orbit, likely-brown-dwarf companion, which orbit an M2 dwarf with a unique evolutionary history. The host star occupies a narrow "gap" in the HR diagram lower main sequence, associated with the M dwarf fully convective boundary and long-term luminosity fluctuations. This system is one of only about a dozen M dwarf multi-planet systems to date that hosts an ultra-short period planet (USP). Here we validate and characterize a third planet in the LHS 1678 system using TESS Cycle 1 and 3 data and a new ensemble of ground-based light curves. LHS 1678 d is a 0.98 +/-0.07 Earth radii planet in a 4.97-day orbit, with an insolation flux of 9.1 +0.9/-0.8 Earth insolations. These properties place it near 4:3 mean motion resonance with LHS 1678 c and in company with LHS 1678 c in the Venus zone. LHS 1678 c and d are also twins in size and predicted mass, making them a powerful duo for comparative exoplanet studies. LHS 1678 d joins its siblings as another compelling candidate for atmospheric measurements with the JWST and mass measurements using high-precision radial velocity techniques. Additionally, USP LHS 1678 b breaks the "peas-in-a-pod" trend in this system, although additional planets could fill in the "pod" beyond its orbit. LHS 1678's unique combination of system properties and their relative rarity among the ubiquity of compact multi-planet systems around M dwarfs makes the system a valuable benchmark for testing theories of planet formation and evolution.

[weatheriscool]

Astronomers discover new Saturn-sized exoplanet
https://phys.org/news/2024-03-astronome ... lanet.html
by Tomasz Nowakowski , Phys.org

An international team of astronomers reports the discovery of a new exoplanet orbiting a solar-type star. The newfound alien world, designated TOI-1135 b is young, hot and comparable in size to Saturn. The discovery was detailed in a paper published February 27 on the pre-print server arXiv.

To date, NASA's Transiting Exoplanet Survey Satellite (TESS) has identified nearly 7,100 candidate exoplanets (TESS Objects of Interest, or TOI), of which 420 have been confirmed so far. Since its launch in April 2018, TESS, with its array of wide-field cameras, is conducting a survey of about 200,000 of the brightest stars near the sun with the aim of searching for transiting exoplanets, including giant extrasolar worlds.

A group of astronomers led by Manuel Mallorquín Díaz of the University of La Laguna, Spain, has now confirmed another TOI monitored by TESS. They identified a transit signal in the light curve of TOI-1135 (also known as HIP 62908 or TIC 154872375)—a young solar-type star of spectral type G0 at a distance of some 371 light years. The planetary nature of this signal was confirmed by follow-up photometry and spectroscopy.

"This paper introduces the discovery and mass characterization of a close giant gas planet orbiting the young solar-type star TOI-1135," the researchers wrote.

TOI-1135 b has a radius of about 0.8 Jupiter radii and its mass is approximately 0.062 Jupiter masses, which yields a density at a level of 0.16 g/cm3. The planet orbits its host every 8.02 days, at a distance of 0.082 AU from it. The equilibrium temperature of TOI-1135 b is estimated to be around 950–1,200 K.

Therefore, the obtained results indicate that TOI-1135 b is an inflated exoplanet, similar in size to Saturn, however less massive than the solar system's two biggest gaseous giants. The planet has an extended atmosphere, most probably due to strong stellar radiation.

[weatheriscool]

TOI-4438 b: a transiting mini-Neptune amenable to atmospheric characterization
https://arxiv.org/abs/2403.09833

[weatheriscool]

Unveiling MOA-2007-BLG-192: An M Dwarf Hosting a Likely Super-Earth
https://arxiv.org/abs/2403.12118

[weatheriscool]

Here we present a transmission spectrum of LHS 1140 b between 1.7 and 5.2 μm, obtained using the NIRSpec instrument on JWST. By combining spectral retrievals and self-consistent atmospheric models, we show that the transmission spectrum is inconsistent with H2-rich atmospheres with varied size and metallicity, leaving a water world as the remaining scenario to explain the planet’s low density. Specifically, a H2-rich atmosphere would result in prominent spectral features of CH4 or CO2 on this planet, but they are not seen in the transmission spectrum.

Instead, the data favors a high-mean-molecular-weight atmosphere (possibly N2-dominated with H2O and CO2) with a modest confidence. Forming the planet by accreting C- and N-bearing ices could naturally give rise to a CO2– or N2-dominated atmosphere, and if the planet evolves to or has the climate-stabilizing mechanism to maintain a moderate-size CO2/N2-dominated atmosphere, the planet could have liquid-water oceans.

Our models suggest CO2 absorption features with an expected signal of 20 ppm at 4.2 μm. As the existence of an atmosphere on TRAPPIST-1 planets is uncertain, LHS 1140 b may well present the best current opportunity to detect and characterize a habitable world.

[weatheriscool]

2027 Space Telescope Could Find 400 Rogue Planets
March 26, 2024 by Brian Wang

Nancy Grace Roman Space Telescope will be sensitive to even lower-mass rogue planets since it will observe from space. It will have wide field of view and sharp vision which will allow us to study the objects it finds in more detail than we can do using only ground-based telescopes. In 2023, researchers estimate it could actually find about 400 rogue planets.

Scientists will couple Roman’s future data with ground-based observations from facilities such as Japan’s PRIME (Prime-focus Infrared Microlensing Experiment) telescope, located at the South African Astronomical Observatory in Sutherland. This 1.8-meter telescope will build on MOA’s work by conducting the first wide-area microlensing survey in near-infrared light. It’s equipped with four detectors from Roman’s detector development program.

https://www.nextbigfuture.com/2024/03/2 ... anets.html

[weatheriscool]

Vera Rubin Telescope Could Detect Mars, Mercury And Pluto Sized Planets from 2025-2035
March 26, 2024 by Brian Wang

Researchers estimate that the number of captured free-floating planets in the outer solar system with mass strictly greater than that of Mars is ∼1.2 and that the number of such planets with a strict cutoff at the mass of Mercury is ∼2.4.

When they instead adopt logarithmic bins centered at the Mars mass and the Mercury mass, respectively, they find that the expected number of such planets is ∼2.7 for mass comparable to that of Mars and ∼5.2 for mass comparable to that of Mercury. These planets would have a median heliocentric distance of ∼1400 au, with ∼half of them existing in the range 600–3500 au.

https://www.nextbigfuture.com/2024/03/v ... -2035.html

[weatheriscool]

A Perfect Tidal Storm: HD 104067 Planetary Architecture Creating an Incandescent World
https://arxiv.org/abs/2403.17062