Exoplanets – worlds of other suns

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Astronomers detect new large sub-Neptune alien world
https://phys.org/news/2021-08-astronome ... world.html
by Tomasz Nowakowski , Phys.orgImage
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Astronomers Find Small Rocky Planet – Just Half the Mass of Venus
https://scitechdaily.com/astronomers-fi ... -of-venus/
By European Southern Observatory August 5, 2021
L 98–59 Planetary System
Image
This artist’s impression shows L 98-59b, one of the planets in the L 98-59 system 35 light-years away. The system contains four confirmed rocky planets with a potential fifth, the furthest from the star, being unconfirmed.

A team of astronomers has used the European Southern Observatory’s Very Large Telescope (ESO’s VLT) in Chile to shed new light on planets around a nearby star, L 98-59, that resemble those in the inner Solar System. Amongst the findings are a planet with half the mass of Venus — the lightest exoplanet ever to be measured using the radial velocity technique — an ocean world, and a possible planet in the habitable zone.
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New class of habitable exoplanets represent a big step forward in the search for life
https://phys.org/news/2021-08-class-hab ... 4Cl3TgT6Rs
by University of Cambridge
A new class of exoplanet very different to our own, but which could support life, has been identified by astronomers, which could greatly accelerate the search for life outside our Solar System.

In the search for life elsewhere, astronomers have mostly looked for planets of a similar size, mass, temperature and atmospheric composition to Earth. However, astronomers from the University of Cambridge believe there are more promising possibilities out there.

The researchers have identified a new class of habitable planets, dubbed 'Hycean' planets—hot, ocean-covered planets with hydrogen-rich atmospheres—which are more numerous and observable than Earth-like planets.

The researchers say the results, reported in The Astrophysical Journal, could mean that finding biosignatures of life outside our Solar System within the next two or three years is a real possibility.
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Re: Exoplanets – worlds of other suns

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HD22496b: the first ESPRESSO standalone planet discovery

Quote :
The ESPRESSO spectrograph is a new powerful tool to detect and characterize extrasolar planets. Its design allows unprecedented radial velocity precision (down to a few tens of cm/s) and long-term thermo-mechanical stability. We present the first standalone detection of an extrasolar planet by blind radial velocity search using ESPRESSO and aim at showing the power of the instrument in characterizing planetary signals at different periodicities in long time spans. We use 41 ESPRESSO measurements of HD\,22496 within a time span of 895 days with a median photon noise of 18 cm/s. A radial velocity analysis is performed to test the presence of planets in the system and to account for the stellar activity of this K5-K7 main sequence star. For benchmarking and comparison, we attempt the detection with 43 archive HARPS measurements and compare the results yielded by the two datasets. We also use four TESS sectors to search for transits. We find radial velocity variations compatible with a close-in planet with an orbital period of P=5.09071±0.00026 days when simultaneously accounting for the effects of stellar activity at longer time scales (Prot=34.99+0.58−0.53 days). We characterize the physical and orbital properties of the planet and find a minimum mass of 5.57+0.73−0.68 M⊕, right in the dichotomic regime between rocky and gaseous planets. Although not transiting according to TESS data, if aligned with the stellar spin axis, the absolute mass of the planet must be below 16 M⊕. We find no significant evidence for additional signals with semi-amplitudes above 56 cm/s at 95% confidence. With a modest set of radial velocity measurements, ESPRESSO is capable of detecting and characterizing low-mass planets and constrain the presence of planets in the habitable zone of K-dwarfs down to the rocky-mass regime.
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Re: Exoplanets – worlds of other suns

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New ultra-hot Jupiter exoplanet discovered
https://phys.org/news/2021-09-ultra-hot ... lanet.html
by Tomasz Nowakowski , Phys.org
An international team of astronomers has detected a new ultra-hot Jupiter extrasolar planet using NASA's Transiting Exoplanet Survey Satellite (TESS). The newfound alien world is nearly two times larger than Jupiter and has a misaligned orbit. The finding is detailed in a paper published August 25 on the arXiv pre-print repository.

The so-called "hot Jupiters" are similar in characteristics to the solar system's biggest planet, but have orbital periods of less than 10 days. Such exoplanets have high surface temperatures, as they orbit their parent stars very closely.

Now, a group of astronomers led by Samuel H. C. Cabot of Yale University reports the finding of a new exoplanet of this type, which turns out to have an ultra-high surface temperature. While observing a bright star designated TOI-1518 with TESS, a transit signal was identified in the light curve of this object. The planetary nature of this signal was confirmed by follow-up high-resolution observations with the EXPRES spectrograph at the Lowell Discovery Telescope.
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Re: Exoplanets – worlds of other suns

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The K2-OjOS Project: New and Revisited Planets and Candidates in K2 Campaigns 5, 16 & 18

Quote :
We present the first results of K2-OjOS, a collaborative project between professional and amateur astronomers primarily aimed to detect, characterize and validate new extrasolar planets. For this work, 10 amateur astronomers looked for planetary signals by visually inspecting the 20,427 light curves of K2 campaign 18 (C18). They found 42 planet candidates, of which 18 are new detections and 24 had been detected in the overlapping C5 by previous works. We used archival photometric and spectroscopic observations, as well as new high-spatial resolution images in order to carry out a complete analysis of the candidates found, including a homogeneous characterization of the host stars, transit modeling, search for transit timing variations and statistical validation. As a result, we report four new planets (K2-XXX b, K2-XXX b, K2-XXX b, and K2-XXX b) and 14 planet candidates. Besides, we refine the transit ephemeris of the previously published planets and candidates by modeling C5, C16 (when available) and C18 photometric data jointly, largely improving the period and mid-transit time precision. Regarding individual systems, we highlight the new planet K2-XXX b and candidate EPIC211537087.02 being near a 2:1 period commensurability, the detection of significant TTVs in the bright star K2-184 (V = 10.35), the location of K2-103 b inside the habitable zone according to optimistic models, the detection of a new single transit in the known system K2-274, and the disposition reassignment of K2-120 b, which we consider as a planet candidate as the origin of the signal can not be ascertained.

And further tens of newly confirmed ones with official K2 designation from NASA Exoplanet Archive de Leon et al. (2021):

https://exoplanetarchive.ipac.caltech.e ... #26Aug2021

Among these some additional planets to known systems, namely K2-185 c, K2-268 d, e, & f, K2-304 c, K2-307 c, K2-331 c & b.
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Re: Exoplanets – worlds of other suns

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TOI-2431 b, another "lava world" with orbital period of 5.4 hours (!!)

An ultra-short period lava world suitable for atmospheric investigation
https://tsc.mit.edu/2021/abstracts.html
Super-Earths with periods shorter than one day are usually referred as Ultra-Short Period planets. Some of them orbit the host star so closely that the surface temperature can reach several thousand degrees, and the thermal emission of the day side can be detected photometrically in the same light curve used to discover the planet. The HARPS-N GTO collaboration has been pivotal in measuring the mass and internal density of these so-called lava worlds detected by Kepler, K2, and now TESS. After briefly reviewing the most important lava worlds, in this proposed talk I will describe our efforts to characterize TOI-2431, a rocky planet orbiting a bright (V=10.9) K dwarf every 5.4 hours, the shortest period among planets with a known density. The planet is expected to have lost its primordial atmosphere, but it may well possess a rock vapor atmosphere sustained by its surface magma ocean. For its short orbital period and the brightness of the host star, this is so far the best target for the characterization of the molten surface of an exo-world using current and future facilities such as CHEOPS, Hubble, and James Webb Space Telescopes.
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Re: Exoplanets – worlds of other suns

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TOI-1246, another multiplanet system
https://zenodo.org/record/5126216#.YT9L250zY2w
TOI 1246 is one of only eight four-planet systems with measured masses and radii for all four planets. TESS observed this moderately bright K dwarf (V=11.6, K=9.9) for 12 sectors, and found four transiting planets. We collected 90 RV observations with Keck/HIRES and TNG/HARPS-N, many of which were contemporaneous with TESS photometry. We refit the photometry to refine planet radii, measure masses for all four planets, and find a surprising range of masses and densities. This system is brighter 93% of other four planet systems, and is a particularly interesting testing ground for mass loss and formation hypotheses due to the high planet multiplicity and varied planet masses.
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Re: Exoplanets – worlds of other suns

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GJ 3929 b
Small and rocky worlds orbiting M dwarfs: GJ 3473 b and GJ 3929 b
https://zenodo.org/record/5126616#.YT9SLJ0zY2w
We present two small transiting planets with mass measurements orbiting bright mid M dwarfs (GJ 3473, GJ 3929). GJ 3473 b (Kemmer et al. 2020) is a hot, presumably rocky, planet (P = 1.198 d, Mb = 1.86 ± 0.30 Me, and radius, Rb = 1.264 ± 0.050 Re), which is due to its high temperature a particularly attractive target for thermal emission spectroscopy. Further, it is accompanied by another non-transiting planet (Pc = 15.509 ± 0.033 d) that has a minimum mass of Mc sin i = 7.41 ± 0.91 Me. For GJ 3929 b (in prep.) we present a preliminary analysis that yields a period of P = 2.616 d, mass Mb = 2.03 ± 0.59 Me, and radius, Rb = 1.155 ± 0.043 Re. The radial velocity data show evidence for another signal, whose origin is, however, not yet clarified.
Both systems add to the TESS level-one science goal to measure the masses for 50 transiting planets with radii smaller than 4 Re.
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