Exoplanets – worlds of other suns

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Astronomers discover twin sub-Neptune exoplanets orbiting nearby star
https://phys.org/news/2021-10-astronome ... iting.html
by Tomasz Nowakowski , Phys.org

By analyzing the data from the TESS-Keck Survey (TKS), an international team of astronomers reports the detection of two almost identically sized sub-Neptune exoplanets orbiting a nearby star. The newly found alien worlds, designated HD 63935 b and HD 63935 c, are about three times larger than the Earth. The finding is detailed in a paper published October 13 on the arXiv pre-print server.

NASA's Transiting Exoplanet Survey Satellite (TESS) is conducting a survey of about 200,000 of the brightest stars near the sun with the aim of searching for transiting exoplanets. So far, it has identified over 4,500 candidate exoplanets (TESS Objects of Interest, or TOI), of which 161 have been confirmed so far.

TKS performs precise radial velocity (PRV) follow-up observations of TESS planet candidates using the Keck telescope on Mauna Kea, Hawaii and the Automated Planet Finder (APF) telescope at Lick Observatory, California. It is the largest collaborative effort in the northern hemisphere to measure precise masses and orbits of over 100 TESS-identified exoplanets.

As part of TKS, a group of astronomers led by Nicholas Scarsdale of the University of California, Santa Cruz, has now confirmed that two sub-Neptune are transiting a nearby bright sun-like star known as HD 63935 (other designations HIP 38374 and TIC 453211454).

"In this paper, we present the confirmation of the subNeptune planets HD 63935 b and c," the researchers wrote.

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Astronomers provide 'field guide' to exoplanets known as hot Jupiters
https://phys.org/news/2021-10-astronome ... iters.html
by University of Arizona

Hot Jupiters—giant gas planets that race around their host stars in extremely tight orbits—have become a little bit less mysterious thanks to a new study combining theoretical modeling with observations by the Hubble Space Telescope.

While previous studies mostly focused on individual worlds classified as "hot Jupiters" due to their superficial similarity to the gas giant in our own solar system, the new study is the first to look at a broader population of the strange worlds. Published in Nature Astronomy, the study, led by a University of Arizona researcher, provides astronomers with an unprecedented "field guide" to hot Jupiters and offers insight into planet formation in general.

Although astronomers think that only about 1 in 10 stars host an exoplanet in the hot Jupiter class, the peculiar planets make up a sizeable portion of exoplanets discovered to date, due to the fact that they are bigger and brighter than other types of exoplanets, such as rocky, more Earthlike planets or smaller, cooler gas planets. Ranging in size from about one-third the size of Jupiter to 10 Jupiter masses, all hot Jupiters orbit their host star at an extremely close range, usually much closer than Mercury, the innermost planet in our solar system, is to the sun. A "year" on a typical hot Jupiter lasts hours, or at most a few days. For comparison, Mercury takes almost three months to complete a trip around the sun.

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TOI-2285b: A 1.7 Earth-radius Planet Near the Habitable Zone around a Nearby M Dwarf
https://arxiv.org/abs/2110.10215

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Astronomers discover infant planet
https://phys.org/news/2021-10-astronome ... lanet.html
by University of Hawaii at Manoa

One of the youngest planets ever found around a distant infant star has been discovered by an international team of scientists led by University of Hawaiʻi at Mānoa faculty, students, and alumni.

Thousands of planets have been discovered around other stars, but what sets this one apart is that it is newly-formed and can be directly observed. The planet, named 2M0437b, joins a handful of objects advancing our understanding of how planets form and change with time, helping shed new light on the origin of the Solar System and Earth. The in-depth research was recently published in Monthly Notices of the Royal Astronomical Society.

"This serendipitous discovery adds to an elite list of planets that we can directly observe with our telescopes," explained lead author Eric Gaidos, a professor in the UH Mānoa Department of Earth Sciences. "By analyzing the light from this planet we can say something about its composition, and perhaps where and how it formed in a long-vanished disk of gas and dust around its host star."

The researchers estimate that the planet is a few times more massive than Jupiter, and that it formed with its star several million years ago, around the time the main Hawaiian Islands first emerged above the ocean. The planet is so young that it is still hot from the energy released during its formation, with a temperature similar to the lava erupting from Kīlauea Volcano.
Subaru Telescope and Keck Observatory on Maunakea. Credit: University of Hawaii

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Astronomers may have discovered the first planet outside of our galaxy
https://phys.org/news/2021-10-astronome ... alaxy.html
by Harvard-Smithsonian Center for Astrophysics

Signs of a planet transiting a star outside of the Milky Way galaxy may have been detected for the first time. This intriguing result, using NASA's Chandra X-ray Observatory, opens up a new window to search for exoplanets at greater distances than ever before.

The possible exoplanet candidate is located in the spiral galaxy Messier 51 (M51), also called the Whirlpool Galaxy because of its distinctive profile.

Exoplanets are defined as planets outside of our Solar System. Until now, astronomers have found all other known exoplanets and exoplanet candidates in the Milky Way galaxy, almost all of them less than about 3,000 light-years from Earth. An exoplanet in M51 would be about 28 million light-years away, meaning it would be thousands of times farther away than those in the Milky Way.

"We are trying to open up a whole new arena for finding other worlds by searching for planet candidates at X-ray wavelengths, a strategy that makes it possible to discover them in other galaxies," said Rosanne Di Stefano of the Center for Astrophysics | Harvard & Smithsonian (CfA) in Cambridge, Massachusetts, who led the study, which was published today in Nature Astronomy.

This new result is based on transits, events in which the passage of a planet in front of a star blocks some of the star's light and produces a characteristic dip. Astronomers using both ground-based and space-based telescopes—like those on NASA's Kepler and TESS missions—have searched for dips in optical light, electromagnetic radiation humans can see, enabling the discovery of thousands of planets.

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Rocky exoplanets are even stranger than we thought
https://phys.org/news/2021-11-rocky-exo ... ought.html
by NOIRLab

An astronomer from NSF's NOIRLab has teamed up with a geologist from California State University, Fresno, to make the first estimates of rock types that exist on planets orbiting nearby stars. After studying the chemical composition of "polluted" white dwarfs, they have concluded that most rocky planets orbiting nearby stars are more diverse and exotic than previously thought, with types of rocks not found anywhere in our Solar System.

Astronomers have discovered thousands of planets orbiting stars in our galaxy—known as exoplanets. However, it's difficult to know what exactly these planets are made of, or whether any resemble Earth. To try to find out, astronomer Siyi Xu of NSF's NOIRLab partnered with geologist Keith Putirka of California State University, Fresno, to study the atmospheres of what are known as polluted white dwarfs. These are the dense, collapsed cores of once-normal stars like the Sun that contain foreign material from planets, asteroids, or other rocky bodies that once orbited the star but eventually fell into the white dwarf and "contaminated" its atmosphere. By looking for elements that wouldn't naturally exist in a white dwarf's atmosphere (anything other than hydrogen and helium), scientists can figure out what the rocky planetary objects that fell into the star were made of.

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TOI-2076 and TOI-1807: Two Young, Comoving Planetary Systems Within 50 pc Identified by TESS that are Ideal Candidates for Further Follow-Up
http://arxiv.org/abs/2111.01311v1

TOI-2257 b: A Highly Eccentric Long-Period Sub-Neptune Transiting a Nearby M Dwarf
http://arxiv.org/abs/2111.01749v1

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Hunting for alien planets with a new solar telescope

by Suvrath Mahadevan, Sam Sholtis, and Jorge Salazar, Texas Advanced Computing Center
https://phys.org/news/2021-11-alien-pla ... scope.html

Thousands of alien worlds are known to orbit stars beyond our solar system. And many more worlds, possibly harboring life, lie waiting to be discovered. A new astronomical instrument called NEID, the NN-explore Exoplanet Investigations with Doppler spectroscopy, has come online in 2021 to help scientists hunt for new alien worlds.

The Texas Advanced Computing Center (TACC) is assisting the effort with supercomputer time and expertise in NEID's scientific search for new worlds.

The name "NEID" derives from the word meaning "to see" in the native language of the Tohono O'odham, on whose land Kitt Peak National Observatory is located. NEID is a spectrograph attached to the WIYN 3.5m telescope at the observatory in Arizona.

"We're proud that NEID is available to the worldwide astronomical community for exoplanet discovery and characterization," said Jason Wright, professor of astronomy and astrophysics at Penn State and NEID project scientist. "I can't wait to see the results we and our colleagues around the world will produce over the next few years from discovering new, rocky planets, to measuring the compositions of exoplanetary atmospheres, to measuring the shapes and orientations of planetary orbits, to characterization of the physical processes of these planets' host stars."

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Astronomers discover a sub-Neptune exoplanet orbiting nearby star
https://phys.org/news/2021-11-astronome ... earby.html
by Tomasz Nowakowski , Phys.org

Using NASA's Transiting Exoplanet Survey Satellite (TESS), an international team of astronomers has detected a sub-Neptune exoplanet orbiting a nearby M dwarf star. The newly found alien world, designated TOI-2257b is about two times larger than the Earth. The finding is reported in a paper published November 2 on the arXiv pre-print server.

TESS is conducting a survey of about 200,000 of the brightest stars near the sun with the aim of searching for transiting exoplanets. So far, it has identified over 4,600 candidate exoplanets (TESS Objects of Interest, or TOI), of which 167 have been confirmed so far.

Recently, a group of astronomers led by Nicole Schanche of the University of Bern in Switzerland has confirmed another TOI monitored by TESS. While observing a nearby M-dwarf known as TOI-2257 (other designation TIC 198485881), a transit signal was identified in the light curve of this star. The planetary nature of this signal was confirmed by follow-up observations using ground-based facilities.

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Alleviating the transit timing variation bias in transit surveys. I. RIVERS: Method and detection of a pair of resonant super-Earths around Kepler-1705
https://arxiv.org/abs/2111.06825

Transit timing variations (TTVs) can provide useful information for systems observed by transit, as they allow us to put constraints on the masses and eccentricities of the observed planets, or even to constrain the existence of non-transiting companions. However, TTVs can also act as a detection bias that can prevent the detection of small planets in transit surveys that would otherwise be detected by standard algorithms such as the Boxed Least Square algorithm (BLS) if their orbit was not perturbed. This bias is especially present for surveys with a long baseline, such as Kepler, some of the TESS sectors, and the upcoming PLATO mission. Here we introduce a detection method that is robust to large TTVs, and illustrate its use by recovering and confirming a pair of resonant super-Earths with ten-hour TTVs around Kepler-1705. The method is based on a neural network trained to recover the tracks of low-signal-to-noise-ratio(S/N) perturbed planets in river diagrams. We recover the transit parameters of these candidates by fitting the light curve. The individual transit S/N of Kepler-1705b and c are about three times lower than all the previously known planets with TTVs of 3 hours or more, pushing the boundaries in the recovery of these small, dynamically active planets. Recovering this type of object is essential for obtaining a complete picture of the observed planetary systems, and solving for a bias not often taken into account in statistical studies of exoplanet populations. In addition, TTVs are a means of obtaining mass estimates which can be essential for studying the internal structure of planets discovered by transit surveys. Finally, we show that due to the strong orbital perturbations, it is possible that the spin of the outer resonant planet of Kepler-1705 is trapped in a sub- or super-synchronous spin-orbit resonance.

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The worlds next door: Looking for habitable planets around Alpha Centauri
https://phys.org/news/2021-11-worlds-do ... alpha.html
by University of Sydney

Could life exist around our nearest stellar neighbors? Led by the University of Sydney and supported by the Breakthrough Initiatives, NASA's Jet Propulsion Laboratory and Saber Astronautics, this project aims to find out.

A mission to discover new planets potentially capable of sustaining life around Earth's nearest neighbor, Alpha Centauri, was announced today.

The proposed telescope project will look for planets in the 'Goldilocks' zone around the star system just four light years away, where temperatures could allow for liquid surface water on rocky planets.

Work on the project began in April of this year. Scientists from the University of Sydney, in partnership with the Breakthrough Initiatives in California, Saber Astronautics in Australia and NASA's Jet Propulsion Laboratory, have named the project TOLIMAN, the Arabic-derived name for Alpha Centauri from antiquity.

"Our nearest stellar neighbors—the Alpha Centauri and Proxima Centauri systems—are turning out to be extraordinarily interesting," said Dr. Pete Worden, Executive Director of the Breakthrough Initiatives. "The TOLIMAN mission will be a huge step towards finding out if planets capable of supporting life exist there."

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A highly mutually-inclined, compact warm-Jupiter system KOI-984?
https://arxiv.org/abs/2111.09668

The discovery of a population of close-orbiting giant planets (≤ 1 au) has raised a number of questions about their origins and dynamical histories. These issues have still not yet been fully resolved, despite over 20 years of exoplanet detections and a large number of discovered exoplanets. In particular, it is unclear whether warm Jupiters (WJs) form in situ, or whether they migrate from further outside and are even currently migrating to form hot Jupiters (HJs). Here, we report the possible discovery and characterization of the planets in a highly mutually-inclined (Imut≃45∘), compact two-planet system (KOI-984), in which the newly discovered warm Jupiter KOI-984c is on a 21.5-day, moderately eccentric (e≃0.4) orbit, in addition to a previously known 4.3-day planet candidate KOI-984b. Meanwhile, the orbital configuration of a moderately inclined (Imut≃15∘), low-mass (mc≃24M⊕;Pb≃8.6 days) perturbing planet near 1:2 mean motion resonace with KOI-984b could also well reproduce observed transit timing variations and transit duration variations of KOI-984b. Such an eccentric WJ with a close-in sibling would pose a challenge to the proposed formation and migration mechanisms of WJs, if the first scenario is supported with more evidences in near future; this system with several other well-measured inclined WJ systems (e.g., Kepler-419 and Kepler-108) may provide additional clues for the origin and dynamical histories of WJs.

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Water Found in Habitable Super-Earth’s Atmosphere for First Time
by Ignat

Astronomers have discovered water vapor in the atmosphere of a super-Earth exoplanet orbiting within its star’s habitable zone. The discovery suggests that liquid water could exist on the rocky world’s surface, possibly forming a global ocean.

The discovery, made with NASA’s Hubble Space Telescope, is the first detection of water vapor in the atmosphere of such a planet. Because the planet, dubbed K2-18 b, is likely to have a temperature similar to Earth, the newly discovered water vapor makes it one of the most promising candidates for follow-up studies with next-generation space telescopes.

“This is the only planet right now that we know outside the solar system that has the correct temperature to support water, it has an atmosphere, and it has water in it, making this planet the best candidate for habitability that we know right now,” lead author Angelos Tsiaras, an astronomer at University College London, said in a press conference.

https://ilovetheuniverse.com/water-foun ... A0JCoogJvs

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Water Found in Habitable Super-Earth’s Atmosphere for First Time
by Ignat

Astronomers have discovered water vapor in the atmosphere of a super-Earth exoplanet orbiting within its star’s habitable zone. The discovery suggests that liquid water could exist on the rocky world’s surface, possibly forming a global ocean.

The discovery, made with NASA’s Hubble Space Telescope, is the first detection of water vapor in the atmosphere of such a planet. Because the planet, dubbed K2-18 b, is likely to have a temperature similar to Earth, the newly discovered water vapor makes it one of the most promising candidates for follow-up studies with next-generation space telescopes.

“This is the only planet right now that we know outside the solar system that has the correct temperature to support water, it has an atmosphere, and it has water in it, making this planet the best candidate for habitability that we know right now,” lead author Angelos Tsiaras, an astronomer at University College London, said in a press conference.

https://ilovetheuniverse.com/water-foun ... A0JCoogJvs

Old study from two years ago.

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New deep learning method adds 301 planets to Kepler's total count

by Jet Propulsion Laboratory

Over 4,5000 planets have been found around other stars, but scientists expect that our galaxy contains millions of planets. There are multiple methods for detecting these small, faint bodies around much larger, bright stars. Credit: NASA/JPL-Caltech

Scientists recently added a whopping 301 newly validated exoplanets to the total exoplanet tally. The throng of planets is the latest to join the 4,569 already validated planets orbiting a multitude of distant stars. How did scientists discover such a huge number of planets, seemingly all at once? The answer lies with a new deep neural network called ExoMiner.

Deep neural networks are machine learning methods that automatically learn a task when provided with enough data. ExoMiner is a new deep neural network that leverages NASA's Supercomputer, Pleiades, and can distinguish real exoplanets from different types of imposters, or "false positives." Its design is inspired by various tests and properties human experts use to confirm new exoplanets. And it learns by using past confirmed exoplanets and false positive cases.

https://phys.org/news/2021-11-deep-meth ... total.html

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HATS-74Ab, HATS-75b, HATS-76b and HATS-77b: Four Transiting Giant Planets around K and M Dwarfs
https://arxiv.org/abs/2112.01928

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New Planet Discovered in the Massive b Centauri Two-star System
by Dustin Manduffie
December 8, 2021

https://www.courthousenews.com/new-plan ... ar-system/

Introduction:

(Courthouse News) — Scientists with the European Southern Observatory discovered a planet in the hottest and most massive planet-hosting star system ever recorded.

The two-star system where the planet is located, known as HIP 71865, or b Centauri, sits within the constellation Centaurus about 325-light years from Earth.

At six times the mass of our own sun, the system is so massive, and so hot, that until being photographed by the ESO’s Very Large Telescope, many experts didn’t believe a planet could exist there. The new discovery shows that it is possible; the planet was found orbiting one of the system’s two stars at around 100 times the distance between Jupiter and the sun.

A team of astronomers from across Europe described the newly identified planet in a study published Wednesday in the journal Nature. See also:
(https://www.eurekalert.org/news-releases/936966? ).

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TESS Finds a New Mars-Sized Planet (With the Density of Mercury)
by Evan Gough
December 8, 2021

https://www.universetoday.com/153610/te ... ore-153610

Introduction:

(Universe Today) Some planets orbit their stars so closely that they have extremely high surface temperatures and extremely rapid orbits. Most of the ones astronomers have found are Hot Jupiters— planets in the size range of Jupiter and with similar compositions as Jupiter. Their size and proximity to their star make them easier to spot using the transit method.

But there’s another type of planet that also orbits very close to their stars and has extremely high surface temperatures. They’re small, rocky, and they orbit their star in less than 24 hours. They’re called ultra-short-period (USP) planets and TESS found one that orbits its star in only eight hours.

And the planet’s density is almost equivalent to pure iron.

The planet orbits a red (M-type) dwarf star named GJ 367 about 31 light-years away. It’s named GJ 367b and it’s about 70% as large as Earth and about 55% as massive.

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An Integrative Analysis of the HD 219134 Planetary System and the Inner Solar System: Extending DYNAMITE with Enhanced Orbital Dynamical Stability Criteria
https://arxiv.org/abs/2112.05337
Quote :

Planetary architectures remain unexplored for the vast majority of exoplanetary systems, even among the closest ones, with potentially hundreds of planets still ``hidden" from our knowledge. DYNAMITE is a powerful software package that can predict the presence and properties of these yet undiscovered planets. We have significantly expanded the integrative capabilities of DYNAMITE, which now allows for (i) planets of unknown inclinations alongside planets of known inclinations, (ii) population statistics and model distributions for the eccentricity of planetary orbits, and (iii) three different dynamical stability criteria. We demonstrate the new capabilities with a study of the HD 219134 exoplanet system consisting of four confirmed planets and two likely candidates, where five of the likely planets are Neptune-size or below with orbital periods less than 100 days. By integrating the known data for the HD 219134 planetary system with contextual and statistical exoplanet population information, we tested different system architecture hypotheses to determine their likely dynamical stability. Our results provide support for the planet candidates, and we predict at least two additional planets in this system. We also deploy DYNAMITE on analogs of the inner Solar System by excluding Venus or Earth from the input parameters to test DYNAMITE's predictive power. Our analysis finds the system remains stable while also recovering the excluded planets, demonstrating the increasing capability of DYNAMITE to accurately and precisely model the parameters of additional planets in multi-planet systems.

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Kepler Bonus: Aperture Photometry Light Curves of EXBA Sources
https://arxiv.org/abs/2112.06683
Quote :

NASA's Kepler mission observed background regions across its field of view for more than three consecutive years using custom designed super apertures (EXBA masks). Since these apertures were designed to capture a region of the sky rather than single targets, the Kepler Science Data Processing pipeline produced Target Pixel Files, but did not produce light curves for the sources within these background regions. In this work we produce light curves for 9,327 sources observed in the EXBA masks. These light curves are generated using aperture photometry estimated from the instrument's Pixel Response Function (PRF) profile computed from Kepler's full-frame images. The PRF models enable the creation of apertures that follow the characteristic shapes of the PSF in the image and the computation of flux completeness and contamination metrics. The light curves are available at MAST as a High Level Science Product (kbonus-apexba). Alongside this dataset, we present kepler-apertures, a Python library to compute PRF models and use them to perform aperture photometry on Kepler-like data. Using light curves from the EXBA masks we found an exoplanet candidate around Gaia EDR3 2077240046296834304 consistent with a large planet companion with a 0.81RJ radius. Additionally, we report a catalog of 69 eclipsing binaries. We encourage the community to exploit this new dataset to perform in depth time domain analysis, such as eclipsing binaries demographic and others.