Exoplanet Stuff

[lpetrich]

The 7 Rocky TRAPPIST-1 Planets May Be Made of Similar Stuff | NASA
noting
Refining the Transit-timing and Photometric Analysis of TRAPPIST-1: Masses, Radii, Densities, Dynamics, and Ephemerides - IOPscience

We find that all seven planets' densities may be described with a single rocky mass–radius relation which is depleted in iron relative to Earth, with Fe 21 wt% versus 32 wt% for Earth, and otherwise Earth-like in composition. Alternatively, the planets may have an Earth-like composition but enhanced in light elements, such as a surface water layer or a core-free structure with oxidized iron in the mantle. We measure planet masses to a precision of 3%–5%, equivalent to a radial-velocity (RV) precision of 2.5 cm s−1, or two orders of magnitude more precise than current RV capabilities. We find the eccentricities of the planets are very small, the orbits are extremely coplanar, and the system is stable on 10 Myr timescales.

"Although the planets in the TRAPPIST-1 system have short orbital periods, ranging from 1.5 to 19 days, the dynamical interactions accumulate gradually with time, which requires longer-timescale monitoring to accurately constrain the orbital model."

Then noting that the planets are in orbital resonances with a resonance period of 491+-5 days (485d to 500d). The observing arc discussed in that paper is for over 4 years, about 3 resonance periods. That will make it easier to disentangle the resonances and other effects.

There is no evidence of an eighth planet with an orbit not much larger than the seventh one's orbit and with a mass around the other planets' masses.

The planets' mean densities somewhat less than the Earth's, correcting for compression due to interior pressure. This means either less iron, more water, or both. There is a downward trend with increasing distance, something not very surprising, since water is much more volatile than metal silicates (rocky material) or iron.

 

[lpetrich]

NASA Exoplanet Archive has lots of interesting news: 2021 Exoplanet Archive News

Warm terrestrial planet with half the mass of Venus transiting a nearby star - NASA/ADS
New ESO observations show rocky exoplanet has just half the mass of Venus | ESO
Comparison of the L 98-59 exoplanet system with the inner Solar System | ESO
ESO = European Southern Observatory

 L 98-59 is a red dwarf with 3 and possibly 4 planets. I looked at other languages, and I was pleasantly surprised to find the Italian and the German versions having more detail. There were separate English articles on b, c, d, and e, but the Italian version has a combined table.

Google Translate helped me out.

That star is 11 parsecs / 35 light years from the Earth, and like many other red-dwarf planets, its planets are very close in.

The first three planets, b, c, and d, were discovered by transits with the TESS planet-hunting satellite, and the recent two, e and f, by radial velocity with the ESPRESSO spectrograph of ESO's Very Large Telescope in Chile.

• b - 0.40 mse - 0.85 rde - 3.60 g/cm^3 - 2.25 days - 0.022 AU - 619 K (346 C)
• c - 2.22 mse - 1.38 rde - 4.57 g/cm^3 - 3.69 days - 0.030 AU - 530 K (257 C)
• d - 1.94 mse - 1.52 rde - 2.95 g/cm^3 - 7.45 days - 0.049 AU - 415 K (142 C)
• e - 3.06 mse - - - 12.8 days - 0.072 AU - 342 K (69 C)
• f - 2.56 mse - - - 23.2 days - 0.103 AU - 286 K (13 C) (unconfirmed)

Solar-System equilibrium temperatures:
Mercury 454 K (181 C), Venus 331 K (58 C), Earth 282 K (9 C), Mars 229 K (-44 C), Jupiter 124 K, Saturn 91 K, Uranus 64 K, Neptune 51 K

 

[lpetrich]

Massive COCONUTS exoplanet discovery led by UH grad student | University of Hawaiʻi System News
[2107.02805] The Second Discovery from the COol Companions ON Ultrawide orbiTS (COCONUTS) Program: A Cold Wide-Orbit Exoplanet around a Young Field M Dwarf at 10.9 pc

The planet is a Jupiter-like planet that orbits a red dwarf called L-34-26 about 11 parsecs (35 ly) away from the Solar System. The planet's surface temperature is around 434 K (161 C), and its projected distance around 6,000 AU. The system's age is about 150 - 800 million years, estimated from the star's rotation period of 2.83 days and its strong stellar activity: H-alpha, UV, and X-rays.


Follow-up of non-transiting planets detected by Kepler. Confirmation of three hot-Jupiters and validation of three other planets - NASA/ADS - "Close-in planets, however, leave additional imprints in the light curve even if they do not transit. These are the so-called phase curve variations that include ellipsoidal, reflection and beaming effects."

Among the ten systems, we confirm three new hot-Jupiters (KIC8121913 b, KIC10068024 b, and KIC5479689 b) with masses in the range 0.5-2 M(Jup) and set mass constraints within the planetary regime for the other three candidates (KIC8026887b, KIC5878307 b, and KIC11362225 b), thus strongly suggestive of their planetary nature. For the first time, we validate the technique of detecting non-transiting planets via their phase curve variations. We present the new planetary systems and their properties. We find good agreement between the RV-derived masses and the photometric masses in all cases except KIC8121913 b, which shows a significantly lower mass derived from the ellipsoidal modulations than from beaming and radial velocity data.

Reflection - direct observation of an exoplanet.

Ellipsoidal variations - from the planet making a tide on the star. It stretches the star both toward the planet and away from it, something like the shape of an American football. That makes the star's cross section larger when the planet is on the side of the star than when it is in front of or behind the star.

Relativistic beaming - moving toward us will make the star look brighter and moving away from us will make it look fainter, from its light alternately being squeezed and stretched.

From 2013:
New method of finding planets scores its first discovery
[1304.6841] BEER analysis of Kepler and CoRoT light curves: I. Discovery of Kepler-76b: A hot Jupiter with evidence for superrotation

BEER = BEaming, Ellipsoidal effects, Reflection

 

[lpetrich]

TESS considering companion smallsat mission - SpaceNews

"The leaders of a NASA exoplanet mission are considering using a spare camera for a companion mission that would enable them to confirm existing discoveries and make new ones."

"TESS, which completed its two-year primary mission in 2020 and is now in an extended mission, has discovered thousands of potential exoplanets."

Comparable to Kepler. This spacecraft would be called TESS-L5, from its operating in the Earth-Sun L5 point, 60d behind the Earth in its orbit.

"The TESS-L5 mission would use laser communications to transmit data back to Earth. That system would provide six megabits per second of bandwidth and would use one-meter telescopes on Earth to receive the signals. Those downlinks would take place in daylight, meaning that the telescopes could be for astronomical observations at night as well."


Like star, like planet — NCCR PlanetS - "One of the patterns emerging from the thousands of exoplanets that astronomers have discovered to date, is that the larger planets often orbit more massive stars."

Michael Lozovsky and his colleagues considered several possible solutions, with mixed results.

Based on their findings, the researchers conclude that planets around larger stars tend to collect gases more quickly during their formation. This is important, because the gas and dust from which the planets form, begins to evaporate as the star grows and radiates more strongly. Thus, the planets only have limited time to grow and acquire what they need for their later existence – perhaps not entirely unlike children, who are expected to stand on their own feet eventually.

 

[lpetrich]

[2108.10888] Habitability and Biosignatures of Hycean Worlds - "We investigate a new class of habitable planets composed of water-rich interiors with massive oceans underlying H2-rich atmospheres, referred to here as Hycean worlds."

Hycean = hydrogen-ocean

We show that Hycean planets can be significantly larger compared to previous considerations for habitable planets, with radii as large as 2.6 Earth radii (2.3 Earth radii) for a mass of 10 Earth masses (5 Earth masses). We construct the Hycean habitable zone (HZ), considering stellar hosts from late M to sun-like stars, and find it to be significantly wider than the terrestrial-like HZ. While the inner boundary of the Hycean HZ corresponds to equilibrium temperatures as high as ~500 K for late M dwarfs, the outer boundary is unrestricted to arbitrarily large orbital separations. Our investigations include tidally locked `Dark Hycean' worlds that permit habitable conditions only on their permanent nightsides and `Cold Hycean' worlds that see negligible irradiation. Finally, we investigate the observability of possible biosignatures in Hycean atmospheres. We find that a number of trace terrestrial biomarkers which may be expected to be present in Hycean atmospheres would be readily detectable using modest observing time with the James Webb Space Telescope (JWST).

Exoplanet-Hunting Satellite CHEOPS Unexpectedly Detects a Strange Planet “Without a Known Equivalent”

This bright star similar to the sun, called Nu2 Lupi, is a little more than 50 light-years from Earth, in the constellation of Lupus. In 2019, HARPS (High Accuracy Radial velocity Planet Searcher) of the European Southern Observatory (ESO) in Chile discovered three exoplanets in this system (called b, c, and d) with masses between those of the Earth and Neptune, and with orbital periods of 11.6, 27.6 and 107.6 days respectively. Afterward, NASA’s TESS satellite, designed to detect transiting planets, found that the two interior planets, b and c, transit Nu2 Lupi, making it one of the only three naked-eye stars which have more than one transiting planet.

“Transiting systems such as Nu2 Lupi are of great importance in our understanding of how planets form and evolve, because we can compare several planets around the same bright star in detail,” explains Laetitia Delrez, a researcher at the University of Liege (Belgium) and first author of the article.

“Our idea was to follow up previous studies of Nu2 Lupi and to observe planets b and c passing in front of Nu2 Lupi with CHEOPS, but during a transit of planet c we were amazed to see an unexpected transit of planet d, which is further out within the system,” she adds.

...
Combining the new data from CHEOPS with archive data from other observatories, the researchers found that planet b is mainly rocky, while planets c and d appear to have large quantities of water surrounded by hydrogen and helium gas. In fact, planets c and d contain much more water than the Earth, a quarter of the mass of each of them is water, in comparison with less than 0.1% on Earth. But this water is not liquid, it is high-pressure ice, or high-temperature water vapor.

 Nu2 Lupi

• b -- 4.6 Me, 1.5 Re, 7.5 g/cm^3, 0.097 AU, 11.6 d, 911 K
• c -- 11.3 Me, 2.6 Re, 3.5 g/cm^3, 0.173 AU, 27.6 d, 682 K
• d -- 8.8 Me, 2.6 Re, 2.8 g/cm^3, 0.425 AU, 107.2 d, 435 K

 

[lpetrich]

 Hycean planet
This article has this warning about it:

The topic of this article may not meet Wikipedia's general notability guideline. Please help to demonstrate the notability of the topic by citing reliable secondary sources that are independent of the topic and provide significant coverage of it beyond a mere trivial mention. If notability cannot be shown, the article is likely to be merged, redirected, or deleted.

Because all the articles on it are derived from only one journal article.

 List of planet types has these lists of Wikipedia articles:

• By range of mass: Giant planet, Ice Giant, Mesoplanet, Mini-Neptune, Planetar, Super-Earth, Super-Jupiter, Sub-Earth
• By range of orbit: Circumbinary planet, Double planet, Eccentric Jupiter, Exoplanet, Extragalactic planet, Goldilocks planet, Hot Jupiter, Hot Neptune, Inferior planets, Inner planet, Outer planet, Pulsar planet, Rogue planet, Superior planets, Trojan planet
• By composition: Chthonian planet, Carbon planet, Coreless planet, Desert planet, Gas dwarf, Gas giant, Helium planet, Ice giant, Ice planet, Iron planet, Lava planet, Ocean planet, Protoplanet, Puffy planet, Silicate planet, Terrestrial planet
• Others: Classical planets, Earth analog, Hypothetical planet, Toroidal planet

 

[lpetrich]

Into the Brown Dwarf Desert

Brown dwarfs rarely occur in close orbits around main sequence stars, the word ‘close’ in this case meaning orbits at 5 AU or closer to the primary. Thus the phrase ‘brown dwarf desert’ to characterize orbits that brown dwarfs rarely occupy as a companion object.

quoting

The relative lack of brown dwarf companions may be related to a transition of the formation mechanisms required to form giant planets and low-mass stars. In this case, lower mass brown dwarfs may form similar to giant planets via core accretion (Pollack et al. 1996) or disk instability (Cameron 1978; Boss 1997) and higher mass brown dwarfs may form similar to stars from gravitational collapse and turbulent fragmentation of molecular clouds (Padoan & Nordlund 2004; Hennebelle & Chabrier 2008). The boundary of these formation mechanisms is unclear and certainly depends on an object’s initial environment.

from this paper:

Populating the brown dwarf and stellar boundary: Five stars with transiting companions near the hydrogen-burning mass limit | Astronomy & Astrophysics (A&A)
and
[2107.03480] Populating the brown dwarf and stellar boundary: Five stars with transiting companions near the hydrogen-burning mass limit


At Least a Quarter of All Sun-Like Stars May Have Devoured One of Their Own Planets
noting
Chemical evidence for planetary ingestion in a quarter of Sun-like stars | Nature Astronomy

Stellar members of binary systems are formed from the same material, and therefore they should be chemically identical. However, recent studies have unveiled chemical differences between the two members of binary pairs composed of Sun-like stars. These chemically inhomogeneous binaries represent one of the most contradictory examples in stellar astrophysics and a source of tension between theory and observations. It is still unclear whether the abundance variations are the result of inhomogeneities in the protostellar gas clouds or are due to planet engulfment events that occurred after the stellar formation. The former scenario undermines the general belief that the chemical makeup of stars provides the fossil information of the environment in which they formed, whereas the second scenario would shed light on the possible evolutionary paths of planetary systems. Our study provides compelling evidence in favour of the planet engulfment scenario. We also establish that planet engulfment events occur in Sun-like stars with a 20–35% probability. Therefore, an important fraction of planetary systems undergo very dynamical evolutionary paths that critically modify their architectures, unlike our calm Solar System. This study opens the possibility of using chemical abundances of stars to identify which ones are the most likely to host Solar System analogues.

Their evidence was from binary stars, and binary stars have an unstable-orbit region around their mutual orbit. So if a planet drifts into that region, it may eventually be ejected or else "eaten" by one of the stars.

An alternate route is what might happen to a "hot Jupiter". These planets likely got to where they were by spiraling in, and if a planet spirals in far enough, it can be "eaten" by its star.

 

[lpetrich]

These so-called 'super-puff' worlds could be exoplanets with ring | Astronomy.com - "Astronomers investigate whether mysterious low-density planets are actually ringed planets that have been misunderstood."

With a picture from a simulation of Saturn doing a transit across the Sun.

Shreyas Vissapragada, a planetary astronomer at Caltech, started thinking about the possibility of super-puffs being ringed planets after another astronomer asked him about it.

“If an alien observed Saturn with the Kepler space telescope, how badly would they get the density wrong if they didn't realize it had rings?” Vissapragada said he asked himself. He did the math and found that they might calculate Saturn’s density to be only half of what it really is.

He teamed up with Anthony Piro, an astronomer at the Carnegie Institution for Science, to investigate what this could mean for Earth astronomers’ observations.

The pair considered what the ring systems would have to be like for known super-puffs to be ringed planets. For example, most known super-puffs are fairly close to their stars, so their rings would have to be rocky rather than icy. Some of the planets wouldn’t be able to have rocky rings wide enough to throw off density estimates, because rocky material that's too far from the planet would clump to form moons. For other super-puffs, rings might still be a possibility.

One will need high-precision photometry to test the ring hypothesis.

Noting
[1911.09673v1] Exploring Whether Super-Puffs Can Be Explained as Ringed Exoplanets

 

[Jimmy Higgins]

Saw a video on this discovery which helps to provide evidence regarding our solar system's future post Sun going all big and stuff. This article covers the subject of a Jupiter like planet orbiting a white dwarf.

Currently, finding planets orbiting white dwarfs is exceptionally difficult. Also, because they are dead systems, is there much reason to look.

 

[lpetrich]

The First Dynamical Mass Measurement in the HR 8799 System - IOPscience
 HR 8799 is a star with four directly-imaged giant planets in large orbits.

The mass measurement was from the pull of the planets on the star, but it is a very new kind of mass measurement. It was from measuring the star's position, something done with the Gaia astrometric satellite and its predecessor Hipparcos. The star accelerated a tiny bit, but enough for us to discover that effect in the satellites' observations.

They find that the innermost planet, e, has a mass of 9.6+1.9-1.8 Jupiter masses, though that depends on hypotheses about the masses of the other planets. But that dependence is not very strong, because gravitational acceleration ~ (mass)/(distance)^2.

Physically-motivated Basis Functions For Temperature Maps Of Exoplanets - Astrobiology

We construct a framework for describing two-dimensional temperature maps of exoplanets with mathematical basis functions derived for a fluid layer on a rotating, heated sphere with drag/friction, which are generalizations of spherical harmonics. These basis functions naturally produce physically-motivated temperature maps for exoplanets with few free parameters.

[2108.04745] Unveiling shrouded oceans on temperate sub-Neptunes via transit signatures of solubility equilibria vs. gas thermochemistry -- using atmospheric chemistry to test the hypothesis of a possible planetary ocean.

 

[lpetrich]

Chandra Sees Evidence for Possible Planet in Another Galaxy | NASA
"Di Stefano and colleagues have instead searched for dips in the brightness of X-rays received from X-ray bright binaries. These luminous systems typically contain a neutron star or black hole pulling in gas from a closely orbiting companion star. The material near the neutron star or black hole becomes superheated and glows in X-rays."

The evidence: a dip in X-ray intensity that may be a transit by a Saturn-sized planet.

Noting
Chandra :: Photo Album :: Whirlpool Galaxy :: October 25, 2021
noting
m51_paper.pdf
"Density enhancements in gas and dust (such as blobs) do not have hard surfaces or thin atmospheres, and therefore produce changes in the X-ray color. That is, they alter the ratios between the numbers of low-energy (soft) and high energy (hard) X-ray photons."

"There is no evidence for a sharp change in the spectrum with intensity."

"We thus conclude that the event is characterized by a grey intensity variation, unlike accretion related dips, and that the cause of this dip is not associated with the source of the emission. These characteristics suggest that the event is caused by the passage of an opaque body with sharp borders in front of the source. Note that this type of spectral stability is also exhibited by eclipses of an XRS by its donor star. "

Like a planet.

 

[lpetrich]

Astronomers Provide 'Field Guide' to Exoplanets Known as Hot Jupiters | University of Arizona News
"By combining Hubble Space Telescope observations with theoretical models, a team of astronomers has gained insights into the chemical and physical makeup of a variety of exoplanets known as hot Jupiters. The findings provide a new and improved "field guide" for this group of planets and inform ideas about 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 stars 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.

Because of their close orbits, most, if not all, hot Jupiters are thought to be locked in a high-speed embrace with their host stars, with one side eternally exposed to the star's radiation and the other shrouded in perpetual darkness. The surface of a typical hot Jupiter can get as hot as almost 5,000 degrees Fahrenheit, with "cooler" specimens reaching 1,400 degrees – hot enough to melt aluminum.

Megan Mansfield and her team use secondary eclipses, where the star goes in front of the planet. The planet is bright enough to be noticed, at least in infrared light, which the team used.

For example, if water is present in the planet's atmosphere, it will absorb light at 1.4 microns, which falls into the range of wavelengths that Hubble can see very well.

"In a way, we use molecules to scan through the atmospheres on these hot Jupiters," Mansfield said. "We can use the spectrum we observe to get information on what the atmosphere is made of, and we can also get information on what the structure of the atmosphere looks like."

The team went a step further by quantifying the observational data and comparing it to models of the physical processes believed to be at work in the atmospheres of hot Jupiters. The two sets matched very well, confirming that many predictions about the planets' nature – based on theoretical work – appear to be correct, according to Mansfield, who said the findings are "exciting because they were anything but guaranteed."

The results suggest that all hot Jupiters, not just the 19 included in the study, are likely to contain similar sets of molecules, like water and carbon monoxide, along with smaller amounts of other molecules. The differences among individual planets should mostly amount to varying relative amounts of these molecules. The findings also revealed that the observed water absorption features varied slightly from one hot Jupiter to the next.

Noting
A unique hot Jupiter spectral sequence with evidence for compositional diversity | Nature Astronomy

Here we show that hot Jupiter secondary eclipse spectra centred around a water absorption band at 1.4 μm follow a common trend in water feature strength with temperature. The observed trend is broadly consistent with model predictions for how the thermal structures of solar-composition planets vary with irradiation level, but is inconsistent with the predictions of self-consistent one-dimensional models for internally heated objects. This is particularly the case because models of internally heated objects show absorption features at temperatures above 2,000 K, whereas the observed hot Jupiters show emission features and featureless spectra. Nevertheless, the ensemble of planets exhibits some degree of scatter around the mean trend for solar-composition planets. The spread can be accounted for if the planets have modest variations in metallicity and/or elemental abundance ratios, which is expected from planet formation models.

Meaning that these planets' surfaces are mostly heated by the planets' stars instead of from their interiors.

 

[lpetrich]

[2106.08538] Waterworlds Probably Do Not Experience Magmatic Outgassing - their ocean-floor pressures are too high

[2107.05597] A Five-Planet Resonant Chain: Reevaluation of the Kepler-80 System
"We find that the four middle planets are in a resonant chain, but that the outermost planet only dynamically interacts in ∼14\% of our solutions. We also find that the system and its dynamic behaviour are consistent with \emph{in situ} formation and compare our results to two other resonant chain systems, Kepler-60 and TRAPPIST-1. "

•  TRAPPIST-1 b, c, d, e, f, g, h: 8:5, 5:3, 3:2, 3:2, 4:3, 3:2
•  Kepler-80(f), d, e, b, c, g: 3:2, 3:2, 4:3, 3:2
• Kepler-60 b, c, d: 5:4, 4:3

Study reveals that giant planets could reach "maturity" much earlier than previously thought | Instituto de Astrofísica de Canarias • IAC

An international team of scientists, in which researchers from the Instituto de Astrofísica de Canarias (IAC) participate together with other institutions from Spain, Italy, Germany, Belgium, UK, and Mexico, has been able to measure the masses of the giant planets of the V1298 Tau system, just 20 million year old. Masses for such young giant planets had not been obtained previously, and this is the first evidence that these objects have already reached their final size at very early stages of their evolution. For this study they have used radial velocity measurements from the HARPS-N spectrographs, at the Roque de los Muchachos Observatory (ORM), and CARMENES, at the Calar Alto Observatory. The results are published today in the journal Nature Astronomy.

...
The study shows that the masses and radii of the planets V1298 Tau b and c are surprisingly similar to those of the giant planets of the Solar System or in other old extra-solar systems. These measurements, which are the first to be obtained of such young giant planets, allow us to test current ideas about the formation of planetary systems. “For many years, theoretical models have indicated that giant planets begin their evolution as bodies with a larger size, and later they contract over hundreds millions or even billions of years '', explains Víctor J. Sánchez Béjar, researcher at the IAC and co-author of the work. "We now know that they can actually reach a size similar to that of the planets in the Solar System in a very short time," he notes.

Meaning that they settle down to their final sizes much faster than one might expect from some theoretical models.

Noting
Rapid contraction of giant planets orbiting the 20-million-year-old star V1298 Tau | Nature Astronomy

We find that the two outermost giant planets, V1298 Tau b and e (0.64 ± 0.19 and 1.16 ± 0.30 Jupiter masses, respectively), seem to contradict our knowledge of early-stages planetary evolution. According to models, they should reach their mass–radius combination only hundreds of millions of years after formation. This result suggests that giant planets can contract much more quickly than usually assumed.

 

[lpetrich]

Modeling Magma Ocean Exoplanets

"A new article explores the possibility that water-rich planets might hide their water deep in their interiors, dissolved in an ocean of magma."

"The authors found that a planet’s interior structure has a discernible effect on its size. For planets of the same mass, those with wet melt–solid interiors can be as much as 16% smaller than those with dry melt–solid interiors or rocky interiors. This can be explained on the molecular level: water molecules nestled snugly between silicate molecules in the mantle increase a planet’s radius less than freewheeling water molecules in the atmosphere or on the surface."

Noting
Hidden Water in Magma Ocean Exoplanets - IOPscience

 

[lpetrich]

Why Does Our Solar System Have No Super-Earths, and Other Questions for Comparative Planetology | News | Astrobiology

Noting
Why Do M Dwarfs Have More Transiting Planets? - IOPscience

We propose a planet formation scenario to explain the elevated occurrence rates of transiting planets around M dwarfs compared to Sun-like stars discovered by Kepler. We use a pebble drift and accretion model to simulate the growth of planet cores inside and outside of the snow line. A smaller pebble size interior to the snow line delays the growth of super-Earths, allowing giant planet cores in the outer disk to form first. When those giant planets reach pebble isolation mass they cut off the flow of pebbles to the inner disk and prevent the formation of close-in super-Earths. We apply this model to stars with masses between 0.1 and 2 M⊙ and for a range of initial disk masses. We find that the masses of hot super-Earths and of cold giant planets are anticorrelated. The fraction of our simulations that form hot super-Earths is higher around lower-mass stars and matches the exoplanet occurrence rates from Kepler. The fraction of simulations forming cold giant planets is consistent with the stellar mass dependence from radial-velocity surveys. A key testable prediction of the pebble accretion hypothesis is that the occurrence rates of super-Earths should decrease again for M dwarfs near the substellar boundary like Trappist-1.

and
Why Does Our Solar System Have No Super-Earths, and Other Questions for Comparative Planetology – Many Worlds

A key component in the hypothesis is that the presence of gas giant planets (such as Jupiter) suppresses the formation of super-Earths. The paper argues that this is due to the process by which the giant planets are formed, and their locations.

Mulders and his group used a newly-embraced theory of planet formation called “pebble accretion,” whereby planets are formed by the pulling in of small bits of solid material (from centimeters to meters in diameter) from the protoplanetary disk. A competing theory says that planets form via “planetesimal accretion,” where much larger forming planets and objects crash into other planets and together they form a much larger object.

Here is Mulders’ explanation of why large planets outside the snowline of a disk keep super-Earths from forming:

quoting

“Initially, pebbles are continuously flowing inward through the disk unimpeded, first passing the locations where cold giant planets can form, than the locations where hot super-earths can form, and eventually they fall into the star.”

“When planets start growing, they initially only accrete a small amount of pebbles. But as they grow larger they start accreting more pebbles, and so fewer pebbles can reach the other planets located closer to the star. If a (giant) planet reaches a certain mass called ‘isolation mass’ they create a structure in the disk that completely blocks the flow of pebbles.”

“So in the model, it’s the location of the giant planet being upstream of where the super-Earths form which allows the giant planet to act as a dam, and preventing the super-Earths downstream from growing.”

Back to Many Worlds.

The presence of both Jupiter and Saturn in our solar system would, then, create a solar dynamic that would block the formation of inner system planets larger than Earth and Venus.

Then about using a systems approach.

In keeping with this approach, the pebble accretion theory of planet formation arose in part because other models could not account convincingly for the formation of large inner cores of the Jupiter and Saturn gas giants. And so a different system was proposed to better explain those phenomena, as well as many others.

As further indication that pebbles often play a significant role in planet formation, Mulders pointed to ringed structures in the dust of the protoplanetary disk of HL Tauri, which he said was a sign of “drifting pebbles.”

Then quoting again.

“So we have ‘seen’ that pebbles are common in planet forming disks,” he said.

“I think the consensus is that pebble accretion plays some role in (rocky) planet formation, but the discussion is how big that role is. Some scientists advocate that pebble accretion is the dominant mechanism in planet formation and should be applied everywhere, other scientists believe that other mechanisms (planetesimal accretion, planet migration) are equally or more important and that the role of pebbles is much more limited and not applicable to many situations.”

“A good example is Earth: it is possible to explain some of its properties such as its mass and location with a pebble accretion model, but there are also geochemical constraints that suggest Earth was assembled through giant impacts, and thus a planetesimal formation model for the Earth and the terrestrial planets is more likely.”

 

[lpetrich]

More from Many Worlds.

For instance, a surprising conclusion published in 2007 is that super-Earths can theoretically be more likely to support life than Earth. As presented by Diana Valencia of the University of Toronto in the Astrophysical Journal, rocky super-Earths will likely be more geologically active than Earth, with more vigorous plate tectonics due to thinner plates under more stress. In fact, models by Valencia and others suggested that Earth was itself a “borderline” case, just barely large enough to sustain plate tectonics — which are generally deemed necessary to recycle compounds needed for life.

(PDF) Inevitability of Plate Tectonics on Super-Earths
Inevitability of Plate Tectonics on Super-Earths - IOPscience

The recent discovery of super-Earths (masses ≤10 M⊕) has initiated a discussion about conditions for habitable worlds. Among these is the mode of convection, which influences a planet's thermal evolution and surface conditions. On Earth, plate tectonics has been proposed as a necessary condition for life. Here we show that super-Earths will also have plate tectonics. We demonstrate that as planetary mass increases, the shear stress available to overcome resistance to plate motion increases while the plate thickness decreases, thereby enhancing plate weakness. These effects contribute favorably to the subduction of the lithosphere, an essential component of plate tectonics. Moreover, uncertainties in achieving plate tectonics in the 1 M⊕ regime disappear as mass increases: super-Earths, even if dry, will exhibit plate tectonic behavior.

 

[lpetrich]

Astronomers find record-breaking haul of starless 'rogue' planets | Space - "The known population of nomadic rogues just went up by nearly a factor of two."

They were observed in infrared light, what their internal-heat energy is radiated as from their surface temperature.

The researchers saw infrared energy emitted by 70 to 170 gas-giant rogue planets, they report in the new study, which was published online today (Dec. 22) in the journal Nature Astronomy. (Young rogues of this heft glow with the heat of their formation for the first few million years of their lives.)

The range stems from uncertainty: The observations did not allow the team to nail down the observed bodies' exact masses, and objects at least 13 times more massive than Jupiter are likely to be "failed stars" known as brown dwarfs rather than planets.

The new results bolster the idea that rogue planets are common throughout the Milky Way galaxy, perhaps even outnumbering "normal" worlds that orbit parent stars.

And further investigation of these newfound worlds, and others like them, could help astronomers better understand how rogue planets come to be, study team members said. For example, do most of them form solo, condensing from a cloud of material too small to produce a star? Or are rogues usually born in "normal" solar systems but booted into the vast dark void by dramatic gravitational interactions?

The paper:
eso2120a_en.pdf - "A rich population of free-floating planets in the Upper Scorpius young stellar association"

 

[lpetrich]

Weird 'hot Jupiter' exoplanet is shaped like a football | Space - an American football
ESA - Cheops reveals a rugby ball-shaped exoplanet
Rugby is a close relative of American football.

Planet b of star  WASP-103 a little bit more massive and brighter and hotter than the Sun.

Cheops measures exoplanet transits – the dip in light caused when a planet passes in front of its star from our point of view. Ordinarily, studying the shape of the light curve will reveal details about the planet such as its size. The high precision of Cheops together with its pointing flexibility, which enables the satellite to return to a target and to observe multiple transits, has allowed astronomers to detect the minute signal of the tidal deformation of WASP-103b. This distinct signature can be used to unveil even more about the planet.

“It’s incredible that Cheops was actually able to reveal this tiny deformation,” says Jacques Laskar of Paris Observatory, Université Paris Sciences et Lettres, and co-author of the research. “This is the first time such analysis has been made, and we can hope that observing over a longer time interval will strengthen this observation and lead to better knowledge of the planet’s internal structure."

What did they measure?

The team was able to use the transit light curve of WASP-103b to derive a parameter – the Love number – that measures how mass is distributed within a planet. Understanding how mass is distributed can reveal details on the internal structure of the planet.

“The resistance of a material to being deformed depends on its composition,” explains Susana Barros of Instituto de Astrofísica e Ciências do Espaço and University of Porto, Portugal, and lead author of the research. “For example, here on Earth we have tides due to the Moon and the Sun but we can only see tides in the oceans. The rocky part doesn’t move that much. By measuring how much the planet is deformed we can tell how much of it is rocky, gaseous or water.”

The Love number for WASP-103b is similar to Jupiter, which tentatively suggests that the internal structure is similar, despite WASP-103b having twice the radius.

“In principle we would expect a planet with 1.5 times the mass of the Jupiter to be roughly the same size, so WASP-103b must be very inflated due to heating from its star and maybe other mechanisms,” says Susana.

“If we can confirm the details of its internal structure with future observations maybe we could better understand what makes it so inflated. Knowing the size of the core of this exoplanet will also be important to better understand how it formed.”

Love numbers are named after geophysicist Augustus Edward Hough Love | British geophysicist | Britannica - they are parameters for measuring distortion as a function of amount of tidal force:  Love number

 

[lpetrich]

Astrometry is back for exoplanets.

Astrometry is measurement of positions of celestial bodies, and it is good for finding out how they move across the sky.

It was a part of a prominent claim of exoplanets early in my life, purported planets of  Barnard's Star discovered by Peter van de Kamp at Sproul Observatory at Swarthmore College a little west of Philadelphia PA. Those purported planets were detected by astrometry on that star, but other astronomers could not reproduce those observations, and maintenance on the telescope was found to produced similar-sized effects. So those planets are now discredited.

But I have found several recent papers on astrometric detection of exoplanets.

[2109.10422] Precise Masses and Orbits for Nine Radial Velocity Exoplanets - with the help of Gaia-spacecraft astrometry.

IoW_20220131 - Gaia - Cosmos - "Astrometric orbit of the exoplanet-host star HD81040" - one of the previous paper's stars.

New Observational Constraints on the υ Andromedae System with Data from the Hubble Space Telescope and Hobby-Eberly Telescope - NASA/ADS -- the HST did astrometry and the HET did radial velocity.

The mass of planet GJ 676A b from ground-based astrometry. A planetary system with two mature gas giants suitable for direct imaging - NASA/ADS -- FORS2 did astrometry and HARPS did radial velocity. FORS2 is on the Very Large Telescope at Paranal Observatory in Chile did astrometry and HARPS is on the 3.6-m Telescope at La Silla Observatory in Chile.

An Astrometric Planetary Companion Candidate to the M9 Dwarf TVLM 513-46546 - NASA/ADS -- the VLBA did astrometry, with nothing for radial velocity. The VLBA is the Very Long Baseline Array of radio telescopes across the contiguous United States, Hawaii, and the US Virgin Islands. Their received signals are combined using interferometry to make the telescopes act like one big telescope.

 

[lpetrich]

Let's see what one can learn.  Methods of detecting exoplanets discusses a variety of methods, and here are counts of planets in NASA Exoplanet Archive by discovery method.

Method	Discovered Planets
Transit	3756
Radial velocity	912
Microlensing	124
Imaging	58
Transit timing variations	22
Eclipse timing variations	16
Orbital brightness modulation	9
Pulsar timing	7
Pulsation timing variations	2
Astrometry	1
Disk kinematics	1
(Total)	4908

Some exoplanets have been detected by other methods after their discovery, notably radial velocity for many transiting ones. I downloaded a data table from NASA's archive and I counted up which methods were used on each exoplanets.

Method(s)	Observed Planets
tran	2994
rv	890
rv,tran	768
micro	124
ima	50
rv,tran,obm	23
etv	16
	8
pul	7
ast,ima	7
obm	5
rv,obm	5
rv,ima	3
ptv	2
rv,ast	2
ast	1
dkin	1
tran,etv	1
tran,obm	1