Exoplanets – worlds of other suns

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Astronomers detect signature of magnetic field on an exoplanet
https://phys.org/news/2021-12-astronome ... lanet.html
by University of Arizona

Researchers have identified the first signature of a magnetic field surrounding a planet outside of our solar system. Earth's magnetic field acts as a shield against energetic particles from the sun known as the solar wind. Magnetic fields could play similar roles on other planets.

An international team of astronomers used data from the Hubble Space Telescope to discover the signature of a magnetic field in a planet outside our solar system. The finding, described in a paper in the journal Nature Astronomy, marks the first time such a feature has been seen on an exoplanet.

A magnetic field best explains the observations of an extended region of charged carbon particles that surround the planet and stream away from it in a long tail. Magnetic fields play a crucial role in protecting planetary atmospheres, so the ability to detect the magnetic fields of exoplanets is a significant step toward better understanding what these alien worlds may look like.

The team used Hubble to observe the exoplanet HAT-P-11b, a Neptune-sized planet 123 light-years from Earth, pass directly across the face of its host star six times in what is known as a "transit." The observations were made in the ultraviolet light spectrum, which is just beyond what the human eye can see.

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Astronomers uncover largest group of rogue planets yet
https://phys.org/news/2021-12-eso-teles ... group.html
by ESO

Rogue planets are elusive cosmic objects that have masses comparable to those of the planets in our Solar System but do not orbit a star, instead roaming freely on their own. Not many were known until now, but a team of astronomers, using data from several European Southern Observatory (ESO) telescopes and other facilities, have just discovered at least 70 new rogue planets in our galaxy. This is the largest group of rogue planets ever discovered, an important step towards understanding the origins and features of these mysterious galactic nomads.

"We did not know how many to expect and are excited to have found so many," says Núria Miret-Roig, an astronomer at the Laboratoire d'Astrophysique de Bordeaux, France and the University of Vienna, Austria, and the first author of the new study published today in Nature Astronomy.

Rogue planets, lurking far away from any star illuminating them, would normally be impossible to image. However, Miret-Roig and her team took advantage of the fact that, in the few million years after their formation, these planets are still hot enough to glow, making them directly detectable by sensitive cameras on large telescopes. They found at least 70 new rogue planets with masses comparable to Jupiter's in a star-forming region close to our Sun, in the Upper Scorpius and Ophiuchus constellations.

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TOI 560 : Two Transiting Planets Orbiting a K Dwarf Validated with iSHELL, PFS and HIRES RVs
https://arxiv.org/abs/2112.13448

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Astronomers Detect an Exoplanet’s Magnetic Field for the First Time
https://www.extremetech.com/extreme/329 ... first-time
By Ryan Whitwam on December 27, 2021 at 10:04 am

All we can say about most of the 4,000+ known exoplanets is that they exist. Their physical characteristics are unknowable with current technology, but a few have given up some secrets. Astronomers using the Hubble Space Telescope have identified a magnetic field around the exoplanet HAT-P-11b. Earth’s magnetic field is essential for our continued existence, and this is the first time we’ve confirmed one around an exoplanet.

Earth and several other objects in our solar system have magnetic fields, a consequence of the way planets and moons interact with the solar wind. On Earth, the magnetosphere deflects damaging radiation, which would otherwise render the surface inhospitable. Fields surrounding exoplanets could serve a similar purpose. There was every reason to think exoplanets could have magnetic fields like the ones we see locally, but this is the first time we’ve been able to confirm that.

Astronomers from the University of Arizona observed the exoplanet HAT-P-11 b across six transits — that’s when the exoplanet passes in front of its host star from our perspective. This is how the HATNet Project discovered HAT-P-11 b in 2009. It was confirmed and further characterized later using radial velocity measurements from the Keck Observatory, which is the other standard method for detecting distant planets. Although, HAT-P-11 b is relatively close in the grand scheme at just 123 light years away.

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A 38 Million Year Old Neptune-Sized Planet in the Kepler Field
https://arxiv.org/abs/2112.14776

Kepler 1627A is a G8V star previously known to host a 3.8 Earth-radius planet on a 7.2 day orbit. The star was observed by the Kepler space telescope because it is nearby (d=329 pc) and it resembles the Sun. Here we show using Gaia kinematics, TESS stellar rotation periods, and spectroscopic lithium abundances that Kepler 1627 is a member of the 38 ± 6 Myr old δ Lyr cluster. To our knowledge, this makes Kepler 1627Ab the youngest planet with a precise age yet found by the prime Kepler mission. The Kepler photometry shows two peculiarities: the average transit profile is asymmetric, and the individual transit times might be correlated with the local light curve slope. We discuss possible explanations for each anomaly. More importantly, the δ Lyr cluster is one of about 103 coeval groups whose properties have been clarified by Gaia. Many other exoplanet hosts are candidate members of these clusters; these memberships can be verified with the trifecta of Gaia, TESS, and ground-based spectroscopy.

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Eccentric exoplanet discovered
https://phys.org/news/2022-01-eccentric-exoplanet.html
by University of Bern

Led by the University of Bern, an international research team has discovered a sub-Neptune exoplanet orbiting a red dwarf star. The discovery was also made thanks to observations performed by the SAINT-EX observatory in Mexico. SAINT-EX is run by a consortium including the Center for Space and Habitability (CSH) at the University of Bern and the National Center of Competence in Research NCCR PlanetS.

"Red dwarfs" are small stars and thus much cooler than our Sun. Around stars like these, liquid water is possible on planets much closer to the star than in our solar system. The distance between an exoplanet and its star is a crucial factor in its detection: the closer a planet is to its host star, the higher the probability that it can be detected.

In a study recently published in the journal Astronomy & Astrophysics, researchers led by Dr. Nicole Schanche of the Center for Space and Habitability CSH of the University of Bern report the discovery of the exoplanet TOI-2257 b orbiting a nearby red dwarf. Nicole Schanche is also a member of the National Center of Competence in Research PlanetS, which the University of Bern runs together with the University of Geneva.

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New sub-Jupiter-mass exoplanet detected by astronomers
https://phys.org/news/2022-01-sub-jupit ... omers.html
by Tomasz Nowakowski , Phys.org

An international team of astronomers reports the detection of a new sub-Jupiter-mass alien world orbiting an M-dwarf star. The newly found exoplanet, designated OGLE-2014-BLG-0319Lb, turns out to be about half as massive as Jupiter. The discovery was detailed in a paper published December 30 on the arXiv pre-print repository.

Based on the gravitational lens effect, the microlensing method is mainly used to detect planetary and stellar-mass objects regardless of the light they emit. This technique is therefore sensitive to the mass of the objects, rather than their luminosity, which allows astronomers to study objects that emit little or no light at all.

The discovery of the microlensing event OGLE-2014-BLG-0319 was announced on March 21, 2014 by the Optical Gravitational Lensing Experiment (OGLE) collaboration. The event was also detected by the Microlensing Observations in Astrophysics (MOA) team and received designation MOA-2014-BLG-171.

Recently, a group of astronomers led by Shota Miyazaki of Osaka University in Japan has analyzed this microlensing event, what revealed the signal indicating the presence of a planetary object. Generally, planetary signals in microlensing events manifest as short-lived anomalous deviations from typical single-lens light curves. Sometimes, these deviations produce a degeneracy problem where several model interpretations are possible for an anomaly.

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Cheops reveals a rugby-ball-shaped exoplanet

by European Space Agency
https://phys.org/news/2022-01-cheops-re ... lanet.html

ESA's exoplanet mission Cheops has revealed that an exoplanet orbiting its host star within a day has a deformed shape more like that of a rugby ball than a sphere. This is the first time that the deformation of an exoplanet has been detected, offering new insights into the internal structure of these star-hugging planets.

The planet, known as WASP-103b is located in the constellation of Hercules. It has been deformed by the strong tidal forces between the planet and its host star WASP-103, which is about 200 degrees hotter and 1.7 times larger than the sun.

Tidal tug

We experience tides in the oceans of Earth mainly due to the Moon tugging slightly on our planet as it orbits us. The sun also has a small but significant effect on tides, however it is too far from Earth to cause major deformations of our planet. The same cannot be said for WASP-103b, a planet almost twice the size of Jupiter with 1.5 times its mass, orbiting its host star in less than a day. Astronomers have suspected that such a close proximity would cause monumental tides, but up until now they haven't been able to measure them.

Using new data from ESA's Cheops space telescope, combined with data that had already been obtained by the NASA/ESA Hubble Space Telescope and NASA's Spitzer Space Telescope, astronomers have now been able to detect how tidal forces deform exoplanet WASP-103b from a usual sphere into a rugby ball shape.

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A pair of Sub-Neptunes transiting the bright K-dwarf TOI-1064 characterised with CHEOPS
https://arxiv.org/abs/2201.03570

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Newly-discovered planets will be 'swallowed' by their stars
https://phys.org/news/2022-01-newly-dis ... stars.html
by University of Hawaii at Manoa

Astronomers at the University of Hawaiʻi Institute for Astronomy (IfA) are part of a team that recently discovered three planets orbiting dangerously close to stars nearing the ends of their lives.

Out of the thousands of extrasolar planets found so far, these three gas giant planets, first detected by the NASA TESS (Transiting Exoplanet Survey Satellite) Mission, have some of the shortest-period orbits around subgiant or giant stars. One of the planets, TOI-2337b, will be consumed by its host star in less than 1 million years, sooner than any other planet currently known.

"These discoveries are crucial to understanding a new frontier in exoplanet studies: how planetary systems evolve over time," explained lead author Samuel Grunblatt, a postdoctoral fellow at the American Museum of Natural History and the Flatiron Institute in New York City. Grunblatt, who earned his Ph.D. from the IfA, added that "these observations offer new windows into planets nearing the end of their lives, before their host stars swallow them up."

The discovery and confirmation of the planets has been accepted for publication in the Astronomical Journal, and was announced on January 13 at an American Astronomical Society press conference. The researchers estimate that the planets have masses between 0.5–1.7 times Jupiter's mass, and sizes that range from slightly smaller to more than 1.6 times the size of Jupiter. They also span a wide range of densities, from the density of cork to three times denser than water, implying a wide variety of origins.

These three planets are believed to be just the tip of the iceberg. "We expect to find tens to hundreds of these evolved transiting planet systems with TESS, providing new details on how planets interact with each other, inflate, and migrate around stars, including those like our Sun," said Nick Saunders, a graduate student at IfA and co-author of the study.

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New insights into seasons on a planet outside our solar system
https://phys.org/news/2022-01-insights- ... solar.html
by McGill University

Imagine being in a place where the winds are so strong that they move at the speed of sound. That's just one aspect of the atmosphere on XO-3b, one of a class of exoplanets (planets outside our solar system), known as hot Jupiters. The eccentric orbit of the planet also leads to seasonal variations hundreds of times stronger than what we experience on Earth. In a recent paper, a McGill-led research team, provides new insight into what seasons looks like on a planet outside our solar system. The researchers also suggest that the oval orbit, extremely high surface temperatures (2,000 degrees C- hot enough to vaporize rock) and "puffiness" of XO-3b reveal traces of the planet's history. The findings will potentially advance both the scientific understanding of how exoplanets form and evolve and give some context for planets in our own solar system.

Hot Jupiters are massive, gaseous worlds like Jupiter, that orbit closer to their parent stars than Mercury is to the Sun. Though not present in our own solar system, they appear to be common throughout the galaxy. Despite being the most studied type of exoplanet, major questions remain about how they form. Could there be subclasses of hot Jupiters with different formation stories? For example, do these planets take shape far from their parent stars—at a distance where it's cold enough for molecules such as water to become solid—or closer. The first scenario fits better with theories about how planets in our own solar system are born, but what would drive these types of planets to migrate so close to their parent stars remains unclear.

To test those ideas, the authors of a recent McGill-led study used data from NASA's retired Spitzer Space Telescope to look at the atmosphere of exoplanet XO-3b. They observed eccentric seasons and measured wind speeds on the planet by obtaining a phase curve of the planet as it completed a full revolution about its host star.

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Astronomers find evidence for a second supermoon beyond our solar system
https://phys.org/news/2022-01-astronome ... solar.html
by Columbia University

Astronomers have reported a second, super-sized moon orbiting a Jupiter-sized planet beyond our solar system. If confirmed, the sighting could mean that exomoons are as common in the universe as exoplanets, and that big or small, such moons are a feature of planetary systems. But it could be a long wait. The first-ever sighting of an exomoon four years ago is still awaiting confirmation, and verification of this newest candidate could be as equally long and contentious.

The discovery, published in Nature Astronomy, was led by David Kipping and his Cool Worlds Lab at Columbia University, which reported the first exomoon candidate in 2017.

"Astronomers have found more than 10,000 exoplanet candidates so far, but exomoons are far more challenging," said Kipping, who has spent the last decade hunting for exomoons. "They are terra incognita."

The team spotted the giant exomoon candidate orbiting the planet Kepler 1708b, a world 5,500 light-years from Earth in the direction of the Cygna and Lyra constellations. This new candidate is about a third smaller than the Neptune-sized moon that Kipping and his colleagues earlier found orbiting a similar Jupiter-sized planet, Kepler 1625b.

Both supermoon candidates are likely made of gas that has piled up under the gravitational pull caused by their enormous size, said Kipping. If one astronomer's hypothesis is correct, the moons may have even started life as planets, only to be pulled into the orbit of an even bigger planet like Kepler 1625b or 1708b.

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Water vapor detected on a 'super Neptune'
https://phys.org/news/2022-01-vapor-super-neptune.html
by Pat Brennan, NASA

The recently discovered planet TOI-674 b, a bit bigger than Neptune and orbiting a red-dwarf star about 150 light-years away, is a member of an exclusive club: Exoplanets, or planets around other stars, known to have water vapor in their atmospheres. Many questions remain, such as how much water vapor its atmosphere holds. But TOI-674 b's atmosphere is far easier to observe than those of many exoplanets, making it a prime target for deeper investigation.

The planet's distance, size and relationship to its star make it especially accessible to spaceborne telescopes. At 150 light-years, it's considered "nearby" in astronomical terms. The star itself, relatively cool and less than half as big around as our Sun, can't be seen from Earth with the naked eye, but this too translates into an advantage for astronomers. As the comparatively large planet—in a size-class known as "super Neptune"—crosses the face of its smallish star, starlight shining through its atmosphere can be more easily analyzed by our telescopes. Those equipped with special instruments called spectrographs—including the just-launched James Webb Space Telescope—can spread this light into a spectrum, revealing which gases are present in the planet's atmosphere.

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A group of astronomers and citizen scientists has uncovered a hidden planet the size of Jupiter in a distant solar system, and they should get the chance to see it again soon.
"There's a lot of science motivation," behind studying long-orbit exoplanets, Dalba added. "We can ask questions like, 'Do short and long orbit exoplanets form differently or evolve differently? How do they change over time?'"

TOI-2180 b is roughly the same size as Jupiter. But it's almost three times more massive; the planet contains roughly 105 Earth masses' worth of elements heavier than hydrogen and helium, according to a release issued by the University of New Mexico, the home institution of discovery team member Diana Dragomir. This density difference could indicate that the planet formed differently from Jupiter.

https://www.space.com/hidden-exoplanet- ... scientists

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NASA's TESS hits milestone of 5,000 exoplanet candidates
https://phys.org/news/2022-01-nasa-tess ... dates.html
by Massachusetts Institute of Technology

The catalog of planet candidates found with NASA's Transiting Exoplanet Survey Satellite (TESS) recently passed 5,000 TOIs, or TESS Objects of Interest.

The catalog has been growing steadily since the start of the mission in 2018, and the batch of TOIs boosting the catalog to over 5,000 come mostly from the Faint Star Search led by MIT postdoc Michelle Kunimoto.

Kunimoto reflects, "This time last year, TESS had found just over 2,400 TOIs. Today, TESS has reached more than twice that number—a huge testament to the mission and all the teams scouring the data for new planets. I'm excited to see thousands more in the years to come!"

Now in its extended mission, TESS is observing the Northern Hemisphere and ecliptic plane, including regions of the sky previously observed by the Kepler and K2 missions. The TOIs added in late December are from the third year of the TESS mission, which ran from July 2020 to June 2021. TESS re-observed the sky visible in the Earth's Southern Hemisphere, revisiting stars it had first observed at the mission's start in 2018.

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Extreme Exoplanet Has a Complex and Exotic Atmosphere
January 28, 2022

https://www.eurekalert.org/news-releases/941663

Introduction:

(EurekAlert) An international team including researchers from the University of Bern and the University of Geneva as well as the National Centre of Competence in Research (NCCR) PlanetS analyzed the atmosphere of one of the most extreme known planets in great detail. The results from this hot, Jupiter-like planet that was first characterized with the help of the CHEOPS space telescope, may help astronomers understand the complexities of many other exoplanets – including Earth-like planets.

The atmosphere of Earth is not a uniform envelope but consists of distinct layers that each have characteristic properties. The lowest layer that spans from sea level beyond the highest mountain peaks, for example – the troposphere –, contains most of the water vapour and is thus the layer in which most weather phenomena occur. The layer above it – the stratosphere – is the one that contains the famous ozone layer that shields us from the Sun's harmful ultraviolet radiation.

In a new study that appeared in the journal Nature Astronomy, an international team of researchers led by the University of Lund show for the first time that the atmosphere of one of the most extreme known planets may have similarly distinct layers as well – albeit with very different characteristics.

An exotic cocktail for an atmosphere

WASP-189b is a planet outside our own solar system, located 322 light years from Earth. Extensive observations with the CHEOPS space telescope in 2020 revealed among other things that the planet is 20 times closer to its host star than Earth is to the Sun and has a daytime temperature of 3200 degrees Celsius. More recent investigations with the HARPS spectrograph at the La Silla Observatory in Chile now for the first time allowed the researchers to take a closer look at the atmosphere of this Jupiter-like planet.

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Validation of 13 Hot and Potentially Terrestrial TESS Planets
https://iopscience.iop.org/article/10.3 ... 881/ac4334

The James Webb Space Telescope will be able to probe the atmospheres and surface properties of hot, terrestrial planets via emission spectroscopy. We identify 18 potentially terrestrial planet candidates detected by the Transiting Exoplanet Survey Satellite (TESS) that would make ideal targets for these observations. These planet candidates cover a broad range of planet radii (Rp ∼ 0.6–2.0R⊕) and orbit stars of various magnitudes (Ks = 5.78–10.78, V = 8.4–15.69) and effective temperatures (Teff ∼ 3000–6000 K). We use ground-based observations collected through the TESS Follow-up Observing Program (TFOP) and two vetting tools—DAVE and TRICERATOPS—to assess the reliabilities of these candidates as planets. We validate 13 planets: TOI-206 b, TOI-500 b, TOI-544 b, TOI-833 b, TOI-1075 b, TOI-1411 b, TOI-1442 b, TOI-1693 b, TOI-1860 b, TOI-2260 b, TOI-2411 b, TOI-2427 b, and TOI-2445 b. Seven of these planets (TOI-206 b, TOI-500 b, TOI-1075 b, TOI-1442 b, TOI-2260 b, TOI-2411 b, and TOI-2445 b) are ultra-short-period planets. TOI-1860 is the youngest (133 ± 26 Myr) solar twin with a known planet to date. TOI-2260 is a young (321 ± 96 Myr) G dwarf that is among the most metal-rich ([Fe/H] = 0.22 ± 0.06 dex) stars to host an ultra-short-period planet. With an estimated equilibrium temperature of ∼2600 K, TOI-2260 b is also the fourth hottest known planet with Rp < 2 R⊕.

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A temperate sub-Neptune at TOI-1759

TOI-1759 b: a transiting sub-Neptune around a low mass star characterized with SPIRou and TESS
https://arxiv.org/abs/2202.01259

A transiting, temperate mini-Neptune orbiting the M dwarf TOI-1759 unveiled by TESS
https://arxiv.org/abs/2202.01240

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Final moments of planetary remnants seen for first time
https://phys.org/news/2022-02-moments-p ... nants.html
by University of Warwick

The moment that debris from destroyed planets impacts the surface of a white dwarf star has been observed for the first time by astronomers at the University of Warwick.

They have used X-rays to detect the rocky and gaseous material left behind by a planetary system after its host star dies as it collides and is consumed within the surface of the star.

Published today (9 February) in the journal Nature, the results are the first direct measurement of the accretion of rocky material onto a white dwarf, and confirm decades of indirect evidence of accretion in over a thousand stars so far. The observed event occurred billions of years after the formation of the planetary system.