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Unmanned Spaceflight.com _ Telescopic Observations _ Nearby Exoplanets

Posted by: JRehling Nov 15 2017, 04:17 PM

There have been a few topics in recent years pertaining to exoplanets found circling nearby red dwarfs, particularly Proxima Centauri and Trappist-1. There's a new one to report, and I thought I'd give the topic a more general scope rather than specific to this one.

The star in question is Ross 128, and the planet's solar flux is between that of Earth and Venus. There's a good chance that this is potentially the most "habitable" exoplanet yet found, and is happily quite close (13th closest system), so that telescopes will be able to separate the light of the planet from that of the star. This is a circumstance that only a few nearby stars will permit in the foreseeable future, so Ross 128 is likely to figure large in our exoplanet studies over the next century.

https://www.eso.org/public/archives/releases/sciencepapers/eso1736/eso1736a.pdf

Posted by: Ron Hobbs Nov 15 2017, 09:26 PM

Excellent! Thank you for the link to the article.

Here is a link to the ESO release, which has cool artistic impressions videos.

https://www.eso.org/public/news/eso1736/

I look forward to hearing more about this system.


Posted by: JRehling Nov 17 2017, 04:17 PM

A quick look outward:

Ross 128 is the 8th closest single red dwarf star. So far, we know of two ~earthsized planets in their ~HZs. Not a significant sample, and we don't know how many are yet to be found, but this is certainly suggestive that about a third of such stars have such planets. (The Doppler method can easily miss planets in orbits more or less perpendicular to our line of sight.) The true number may be much higher, because we don't have clear negatives yet on the other 6 of those 8.

Now, between Ross 128 and 20 light years out, there are 36 more single red dwarfs. Between 20 and 30 light years out, there are 75 more. And of course, there are 6 farther than Proxima Centauri and closer than Ross 128, making 117 more red dwarfs within 30 LY. If a third of those have such planets, we have dozens yet to find.

This says seriously good things about the sample we are going to be able to examine with followup studies.

The closest such transiting planet, however, may be quite a bit farther, but distance won't be a serious impediment for detection and characterization of those.

And, of course, there are also many multiple systems and bigger, hotter stars. We already know that the closest single non-red dwarf, Epsilon Eridani, probably has planets.

It's going to be an interesting few decades ahead for studying nearby terrestrial planets.

Posted by: JRehling Dec 6 2017, 04:40 PM

A best-of-its-kind discovery: K2-18b (announced in 2015) is a transiting Super Earth 111 light years away. It orbits a red dwarf with a period of 32 days and has an equilibrium temperature very nearly equal to Earth's.

What's good: It transits! Studying the planet's atmosphere, therefore, can be done as the star's light passes through it, or by subtracting the planet's light from the system's as a whole when the star eclipses the planet. There is no need to resolve the planet, so the distance is not highly relevant to follow-up science.

This has also allowed an accurate measurement of mass and therefore density, and this reveals that the planet has a very earthlike density with 2.24x the radius and 8x the mass. This is itself a striking result as part of a new and growing survey of Super Earths, and the mystery of whether they are more like big Earths or little Neptunes. In most cases, we know the radius or the mass but not both.

What's bad: If we're looking for Earth analogues, the larger size may still mean that the atmosphere and climate are radically different from anything we've seen before. On the other hand, with red dwarf systems, there's a fear that flares could strip away an atmosphere and in this case, those two concerns potentially offset one another. Maybe a big planet with this high escape velocity could end up with an intact atmosphere that could even be more earthlike if a bit of it has been blasted away.

Add this to the short list of ones that we'll be watching closely over the next decade +.

Posted by: JRehling Feb 12 2018, 02:56 PM

New clues to the density (and composition) of the Trappist-1 exoplanets:

https://www.jpl.nasa.gov/news/news.php?release=2018-022

Posted by: JRehling Nov 15 2018, 04:38 AM

An article in Nature announces the discovery of a cold super-earth orbiting Barnard's Star.

https://phys.org/news/2018-11-astronomers-super-earth-barnard-star.html

I wonder if some super-earths might have warm surfaces due to greenhouse effect from a thick atmosphere, but I will leave that up to the experts.

This would mean that both of the closest red dwarfs and at least three of the closest four have planets orbiting them. The evidence is shaping up that nearly all red dwarfs have planetary systems, although the 5th and 6th closest, Luyten 726-8, are a binary pair that come within 2.1 AU of one another, which might make that system in particular an unusual case. This also makes five planetary systems within 11.1 light years. There could also be more with smaller planets, more distant planets, and/or an orbital inclination that hides planets from the radial velocity method.

Intrigue grows for the eventual observations from JWST (2021) and ELT (2024).

Posted by: Steve G Nov 15 2018, 01:46 PM

Bernard's star was the first star ever to have a suspected planet. In the sixties Peter van de Kamp claimed that he had detected a perturbation in the proper motion caused by a Jovian-class planet. It was eventually refuted but I'm glad to see the star finally has been confirmed as having a planet. Exciting news to have something so close to home.

Posted by: JRehling Nov 15 2018, 06:24 PM

Yeah, Steve, my public library had a book that flat-out stated that Barnard's Star had planets, so it's a sweet resolution to that long-running narrative – and, as is clear, this discovery cannot be the planet(s) that were claimed long ago.

I took a picture of Barnard's Star this summer so I can make a "video" of its proper motion over a span of year(s) – it's a pretty little dot, more orange than red. One distinction held by this system is that it's the closest planetary system (and closest star, period) that can be seen from north of the tropics.

With a nominal orbital distance of 0.4 AU, Barnard's Star b will have about 5 times the angular distance from its star that Proxima b will from Proxima Centauri. That is much less angular separation, however, than cases like Fomalhaut b, which is much farther from its primary than Neptune is from the Sun. Barnard's Star b will likely be one of the easiest exoplanets to resolve and one day reveal non-pointlike images of its surface.

Posted by: JRehling Jun 19 2019, 04:48 PM

Various updates:

Two planets, potentially habitable, have been discovered orbiting Teegarden's Star:
https://www.nationalgeographic.com/science/2019/06/two-potentially-life-friendly-planets-found-12-light-years-away-teegardens-star/

A visual (IR) search for planets orbiting Alpha Centauri A and B is now underway, with observations already far along. It is not likely that a close Earth analogue could be observed now, but other planets whose existence could either boost or deflate the possibility of an Earth analogue could be detected.
https://www.space.com/alien-planets-alpha-centauri-breakthrough-watch.html

Aggregating reports from different researchers, we now have reports of 7 ~Earth-sized and ~Earth-temperature planets orbiting 6 of the 17 closest red dwarfs, all within 14 light years. This is in line with Kepler estimates of planetary frequency suggesting that "eta Earth" for red dwarfs is on the order of 0.4 to 0.5 such planets per star. (FWIW, Barnard's Star is probably excluded from the possibility because of the detection of other planets orbiting it, with observations that could have detected an earthlike planet if it existed.)

Currently, no planet discovery methods except the transiting method (which requires exceptional luck regarding orbital inclination) is capable of having discovered Earth-sized and Earth-temperature planets orbiting K or G stars, and any such discoveries will likely require visual detection via JWST or 30-meter class ground observatories. This is sensitive to the proximity of such systems, so there are probably four that stand above the rest in future searches: Alpha Centauri A and B, with their unique closeness; Epsilon Eridani, known to possess larger outer planets; and, Tau Ceti, known to possess super-Earths bracketing the habitable zone on both sides with an intriguing gap in between that does not contain any larger planet and which, given known systems, is highly suggestive that some smaller planet could be present right in the habitable zone.

These approximately 11 planets + opportunities largely define the set of any possibly habitable planets which will be characterized with spectroscopy as that capability comes online in the next few years. Of the four M and G stars where we only hope for such a planet to exist, the expected number of such planets is roughly 1, but we will simply have to wait and see if that number is higher or lower. It is not impossible that more candidates will emerge among the remaining nearby red dwarfs, though in many cases, the current status of non-detection equals evidence against the existence of an Earth analogue. Overall, the number of nearby Earth analogue candidates is plausibly between 7 and 15, with the most likely number to be approximately 9.

These nearby non-transiting exoplanets define one major direction for future study. Transiting exoplanets (Earth analogue or otherwise) allow a completely separate technique for followup study, and allow for systems at greater distance to be characterized, but, again, depend on the exceptional luck of a transit, which will only apply to very roughly 2% of cases.

Exciting times!

Posted by: ngunn Jun 21 2019, 08:17 AM

The Science Daily article contains these sentences:

But the system is located at a special place in the sky: from Teegarden's star you can see the planets of the solar system passing in front of the Sun.

"An inhabitant of the new planets would therefore have the opportunity to view the Earth using the transit method," says Reiners.


I plotted the RA and Dec in my little star atlas and can see that it certainly lies close to our ecliptic plane. However the planets in our system are very widely spaced compared with Teegarden's, TRAPPIST 1 and the like, also their orbital planes differ significantly, so I'm wondering which ones actually do transit as seen from Teegarden's star? They cannnot all do so for sure. (I've found a crude animation that appears to show them doing so but it uses coplanar orbits and is all out of scale.) Can anyone point me to some good information on this?

Posted by: Hungry4info Jun 21 2019, 10:46 AM

The claim in the paper was a bit more nuanced than it has been reported. Right now only Mercury transits, but the others will soon because of the star's high proper motion. The attached figure is from the paper.

 

Posted by: ngunn Jun 21 2019, 11:19 AM

That's perfect, thanks! The figure shows nicely how no external observer anywhere could discover all our planets by the transit method.

Posted by: Gladstoner Jun 21 2019, 11:39 PM

Interesting.

Plus, for each Sol system planet, a band can be projected onto our celestial sphere which would contain all stars from which a transit could theoretically be observed. In the case of the earth, it would be 1/2 degree wide along the ecliptic.

Posted by: JRehling Jun 24 2019, 01:55 AM

QUOTE (ngunn @ Jun 21 2019, 01:17 AM) *
the planets in our system are very widely spaced compared with Teegarden's, TRAPPIST 1 and the like


A perhaps-transparent explanation: Tidal dynamics vary with the third power of distance, so close-in (portions of) systems are much more likely to be controlled by tides, with planetary orbital inclinations clustering near that of the star, and therefore near one another. This is therefore true of "habitable zones" of red dwarfs and, preferentially, most multi planet systems whose planets were discovered by the transit method.

The future work in characterizing exoplanets with spectroscopy (particularly ones that aren't extremely hot) will to a fair extent break down into a 2x2 matrix: {red dwarf, sunlike [KG dwarfs]} x {nearby enough to allow separation and direct imaging, transiting planets}. By and large, nearby and transiting end up [almost?] totally exclusive because of the low probability of an inclination that allows a transit.

Of those four possibilities, red dwarf + direct imaging will have a very small set of possibilities that could even begin and end with Proxima b for the time being, but hopefully the technology and circumstances will allow a few more. Transiting Earth analogues orbiting sunlike stars will be hard to study, too, for the simple reason that the long orbital period means a long wait between observations, and a few hours once a year means very limited signal-to-noise ratio and a serious constraint for earthbound observatories, which spend half the time in daylight.

Posted by: JRehling Aug 8 2019, 02:27 PM

Here's a fresh update on the specific and unique case of Alpha Centauri:

https://www.scientificamerican.com/article/the-hunt-is-on-for-alpha-centauris-planets/

It's interesting to know that relatively massive planets have been ruled out for Alpha Centauri A and B, which leaves us with a large probability, especially for B, that there are either terrestrial planets or none at all. It's also interesting to note that the increasing distance between A and B makes the search easier all the time. Finally, the best and latest visual search will post its results in October.

I'd add that the orbital period of any putative earthlike planet will compare to one year, which means that a visual search, to be thorough, has to include observations spread over at least a year because in any given month, a putative planet might be poorly positioned, either in terms of separation between the planet and its primary star or being positioned for the time being on the side that is unfortunately closer to the other star in the binary pair, and thus experience more stray light interference.

It seems likely that the ELT will resolve the issue definitively, either giving us the ability to perform spectroscopy on terrestrial planets orbiting Alpha Centauri or to establish that any planets there are too small to be very earthlike.

Posted by: dtolman Aug 14 2019, 03:11 PM

Not sure the best place to put this... but researchers have used https://arxiv.org/ftp/arxiv/papers/1908/1908.04350.pdf that manages to capture the rough shape of North America, Eurasia, Africa, and Australia/Antarctica.

A similar technique could be used for any exoplanet with static albedo features (such as oceans or continents).

Posted by: HSchirmer Aug 15 2019, 04:31 PM

QUOTE (dtolman @ Aug 14 2019, 04:11 PM) *
Not sure the best place to put this... but researchers have used https://arxiv.org/ftp/arxiv/papers/1908/1908.04350.pdf that manages to capture the rough shape of North America, Eurasia, Africa, and Australia/Antarctica.

A similar technique could be used for any exoplanet with static albedo features (such as oceans or continents).



Interesting article about locating a telescope near the Lagrange point, which would use diffraction through the outer atmosphere to create an image with up to 45,000 amplification.

QUOTE
The Terrascope: Challenges Going Forward
https://www.centauri-dreams.org/2019/08/13/the-terrascope-challenges-going-forward/


Posted by: JRehling Jan 16 2020, 08:03 PM

Proxima c, a candidate planet orbiting Proxima Centauri at 1.5 AU.

https://www.scientificamerican.com/article/the-curious-case-of-proxima-c/

Posted by: JRehling Apr 16 2020, 07:02 PM

Reanalysis of Kepler data finds one of the most promising earthlike candidate exoplanets yet:

https://www.nasa.gov/press-release/earth-size-habitable-zone-planet-found-hidden-in-early-nasa-kepler-data

Key takeaways, in my opinion:

Kepler 1649-c is the second planet found in its system and the first has previously been called a candidate Venus-like planet.

The mass and density of the planet have not yet been measured.

The host star is a red dwarf. It has not been established yet how prone this star is to flares.

This is unusually close for a Kepler discovery

For a reasonably stringent definition of "earthlike" in terms of size and thermal radiation, this is only the fourth star found to host a transiting earthlike candidate. The other three are Kepler 186, TOI 700, and TRAPPIST-1, which hosts about two such candidates.

So, we have about five such candidates that transit their star, and these will all be outstanding candidates for examination with JWST, to see if we can assess their color, albedo, spectrum, temperature, and atmospheric composition. Of these, only one, Kepler 186f, does not orbit a red dwarf, and is therefore not tidally locked. That may be important for habitability, and also would allow us to determine a light curve and produce a low resolution map.

Posted by: JRehling Apr 22 2020, 08:34 PM

Astronomers using the VLT may have detected Proxima c optically.

This result still lurks on the boundary between a suspected detection and an actual detection, and I think if you read the literature fairly, it remains possible that Proxima c doesn't even exist. Multiple lines of evidence (each individually not compelling) pointing to the same entity start to add up to some real evidence, but there's no formal way to assess the significance of an unknown signal.

Meanwhile a VLT campaign aimed at Alpha Centauri A and B last year has still not released its results.

The key takeaway is that optical studies of nearby exoplanets have not yet begun, but we're knocking on the door.

https://www.scientificamerican.com/article/astronomers-may-have-captured-the-first-ever-image-of-nearby-exoplanet-proxima-c1/

Posted by: JRehling Jun 7 2020, 04:25 AM

The story of Proxima c has twisted and turned with a fourth result pointing to its existence and apparent confirmation. This is a unique case in all of exoplanet science as the evidence for its existence combines radial velocity, direct imaging, and astrometry (side-to-side motion).

http://astrobiology.com/2020/06/25-year-old-hubble-data-confirms-exoplanet-proxima-centauri-c.html

Furthermore, careful studies of Proxima b have refined (and lowered) its estimated mass, and furthermore provided evidence of Proxima d: a planet with a mass of about 0.3 ME and an orbital period of 5.15 days.

All told, Proxima Centauri now has a possible "Mercury" to go along with its "Earth" and "Neptune." Proxima c (the Neptune) remains the best, possibly unsurpassable, case scenario for imaging a nearby exoplanet as the technologies become available.

There has still been no publication regarding VLT searches for possible planets orbiting Alpha Centauri A and B that took place at this time last year. Originally, the team was hopeful that they would have something to say, one way or the other, by October.

Posted by: ngunn Jun 10 2020, 07:09 AM

Thanks for the interesting update and, in general, for keeping this thread refreshed with new information and ideas. I am always reminded as the curtain slowly lifts of the limitations imposed by observational selection and wonder about the remaining unseen planets in this and other systems.

Posted by: JRehling Jul 6 2020, 08:02 PM

Another nearby system with interesting potential: Last month, the discovery of two warm/hot Super Earths around Lacaille 9352 (Gliese 887) was announced. This is actually the brightest red dwarf in the sky (or nearly so) at 10.7 light years away, and is near the boundary of classification as a K star rather than M. This alone is a notable discovery. What might be more interesting is the additional indication of a third planet with an orbital period of 51 days, because such a planet, if real, could be an earth-sized planet in the habitable zone. Moreover, such a planet might turn out to be outside the grip of tidal locking. I'm putting the cart before the horse with all those "if"s but the significance is that tidal locking might turn out to be a factor restricting habitability, and we know of very few earth-sized planets in habitable zones that aren't likely to be tidally locked, and we don't know of any that are this nearby. (Of course, we have yet to establish the rotation of any earth-sized exoplanets, but dynamical factors strongly imply this for many cases.)

I think we should be on the lookout for confirmation and followup in case Gliese 887 d exists. This, along with Alpha Centauri A and B, Tau Ceti, and Epsilon Eridani, offer five nearby possibilities for non-tidally locked earthlike planets that we will be able to observe directly. As yet, we have zero discoveries, so this mere hint of one is already something to pique the intrigue.

Posted by: HSchirmer Jul 9 2020, 12:38 PM

QUOTE (HSchirmer @ Aug 15 2019, 04:31 PM) *
Interesting article about locating a telescope near the Lagrange point, which would use diffraction through the outer atmosphere to create an image with up to 45,000 amplification.


I like the naming convention - Terrascope for Earth as lens, that would make the FOCAL / solar Einstein ring scope a Solscope?

Can't wait for the figures for the Jovascope...

Posted by: JRehling Dec 23 2020, 10:19 PM

We obviously have not yet begun to learn about the climates or geology of terrestrial exoplanets or super-earths. Here's a paper suggesting that Proxima Centauri c might just be more earthlike than some of the "earthlike" terrestrial exoplanets orbiting red dwarfs.

http://www.sci-news.com/astronomy/super-earth-proxima-c-earth-like-stellar-environment-09106.html

It seems to me that when one factor might make a planet relatively less earthlike, there is the possibility that another factor could make up for that, meaning that we might find some earthlike climates out there where the planet's physical parameters different from Earth's in two offsetting ways. For example, a harsh stellar wind that would strip away an atmosphere might be compensated for on a planet with higher escape velocity. Or, a planet with a strong greenhouse effect might end up with earthlike temperatures if it gets much less heat from its star. It will be a while before we find out, but Proxima c might well be the first place for which we get the answers – it's the closest super-earth we'll ever find.

Posted by: JRehling Feb 23 2021, 08:52 AM

We've been waiting well over a year to hear about observations of Alpha Centauri made in 2019. Here we have the still provisional first report: the VLT may have discovered, in 10µm IR, a Neptune-sized exoplanet in the habitable zone of Alpha Centauri A.

As the article notes, any such detection would be slightly bad news for anyone hoping that an Earth-sized planet might exist in that niche. For now, the detection is uncertain. If it does turn out to be real, it leaves room for a more earthlike discovery on the edges of Alpha Centauri A's habitable zone, and Alpha Centauri B is still a possibility. In a subtle way, the lack of any detection at Alpha Centauri B may even be the best news, because it may mean that any such planet there is smaller, and more Earth-sized. Then again, it could be that other planets just happened to be in unfavorable locations in their orbits at the time of the observations.

Future observations await!

https://www.scientificamerican.com/article/is-it-a-planet-astronomers-spy-promising-potential-world-around-alpha-centauri/

Posted by: Decepticon Feb 23 2021, 09:53 PM

A Earth-sized Moon sitting in orbit would be wishful thinking.


Posted by: JRehling Feb 24 2021, 12:36 AM

If I had to guess, the large natural moon of a "Neptune" inside the ice line would be about the mass of Titania minus its ice mass, so more like Vesta than Earth, but I'm extrapolating from very low n!

For the hope of a close Earth analogue orbiting Alpha Centauri A, I think we have a better chance that this will be a false detection and a yet-undetected terrestrial planet will coincidentally be in its place. Or, that this planet is real and an earth-sized terrestrial planet will be outside of it, still in the habitable zone.

If this is a Neptune where we think it is, it would stand a good chance of holding this distinction: The exoplanet with the largest apparent diameter, and thus, likely the first we will ever image with detail… whenever appropriately powerful instruments come about.

Posted by: HSchirmer Feb 24 2021, 01:26 AM

QUOTE (Decepticon)
A Earth-sized Moon sitting in orbit would be wishful thinking.


Eh, not entirely out of the realm of possibilities, but I guess they'd be more likely to be water-worlds?


QUOTE (JRehling @ Feb 24 2021, 01:36 AM) *
If I had to guess, the large natural moon of a "Neptune" inside the ice line would be about the mass of Titania minus its ice mass, so more like Vesta than Earth, but I'm extrapolating from very low n!


I will be interesting either way, especially because this may be our first glimpse of an ice giant with the primordial moon system intact. Given that in our solar system "we can't have nice things" and both our ice giants are a bit damaged.....

Posted by: JRehling Mar 14 2021, 06:20 AM

This pushes the boundary of "nearby" a bit, but TESS has found a five-planet transiting system orbiting a sunlike star.

https://en.wikipedia.org/wiki/HD_108236

By the nature of TESS, it is a given that any of its discoveries are in short-period orbits, so while the solar system's fifth planet has an orbital period of 12 years, this system's fifth planet has an orbital period of under 30 days.

The estimated densities of the two inner planets are rather similar to Earth while the three outer planets have more Neptune-like densities.

High temperatures should make these planets rather unlike Earth but these are still of great interest because, as transiting planets only 211 LY away, these are still good candidates for follow-on study, because the apparent magnitude of the star (9.24) allows for good signal to noise ratio. For comparison, TRAPPIST-1, though much closer, is a red dwarf, and appears much dimmer. HD 108236's system may permit some breakthroughs in our understanding of the evolution of super Earths. Studies to characterize these planets will certainly book some time on JWST and terrestrial telescopes.

Posted by: JRehling Mar 23 2021, 06:19 PM

A new important discovery: Gliese 486 b, a small Super Earth in a transiting orbit only 26 light years away:

https://arxiv.org/pdf/2103.04950.pdf

This is significant for one reason: The proximity and thus the apparent brightness of the star (magnitude ~11.4) make this planet's frequent transits extremely favorable for studying this planet's atmosphere and possibly surface composition. It is, in a nutshell, the single terrestrial planet that offers the best signal-to-noise ratio for such studies, (and it may possibly maintain that distinction forever against any future discoveries.)

The bad news… it's hot, almost certainly much hotter than Venus. This would be worse news if it turns out to be too hot to hold onto an atmosphere, and then the potential for such studies are moot.

It's a sure thing that this world will, along with TRAPPIST-1 and HD 108236, which I mentioned in my last post on this thread, leap to the top of priorities for observation time with JWST and other instruments capable of characterizing exoplanets during transits.

It could well be that within a short time, we'll know more about this planet than we knew about Venus in the 1940s.

Posted by: JRehling Mar 30 2021, 08:37 PM

The initial set of TOIs (Tess Objects of Interest) from the main mission has been published.

https://arxiv.org/pdf/2103.12538.pdf

There are 2241 TOIs reported; the data here and its presentation is strongly analogous to Kepler data, even down to the nomenclature, while the astrophysical parameters differ quite a bit from Kepler. In particular, the vast majority of stars were observed for only 27 days each, and most of the rest were observed for only 54 days, which places an upper bound of any possible TOIs' orbital periods for such stars. Accordingly, the set includes a lot of planets that are in the habitable zone of M dwarfs or in the very hot zone of other stars. This is also unlike Kepler in that Kepler looked at one, small favorable part of the sky and certainly left open the possibility of future missions / campaigns conducting the same approach looking at other parts of the sky; in contrast, TESS is looking at virtually all stars of a certain kind, and is performing a kind of definitive and even final search for all such cases – "bright" stars all over the entire sky.

I can't speak with authority as to the characteristics of the data, but with the Kepler equivalent, KOIs, the expectation was that the vast majority actually correspond to planets but that verifying some of them would not be possible with Kepler data alone. I can say for sure that Kepler's instrument had unexpectedly high (and idiosyncratic, non-isotropic) noise and that led to a lot of false positives, and I would optimistically hope for better performance from TESS. I would further project that we can expect approximately 2000 of these to be real planets and that TESS's extended mission(s) will increase the harvest considerably.

All told, we can expect the number of known exoplanets to jump by about 40% as this data is reviewed. Virtually all candidates for "earthlike" planets that transit red dwarfs and are worthy targets for followup science should end up being known at the conclusion of this analysis.

Posted by: JRehling Aug 19 2021, 02:29 PM

There's a long-running saga in progress about the violence of red dwarf stars, and rather than try to capture it all, I'll post the latest installment. There is considerable concern that the extremely active nature of red dwarfs – violent flares that increase the stars' brightness by more than 100% in high-energy wavelengths – might blast every otherwise "earthlike" planet orbiting them into an airless state like Luna rather than like Earth.

However, the last big story offers hope: Those flares may congregate at high latitudes, aiming the flares away from the plane of nearby planets.

https://www.washington.edu/news/2021/08/05/superflares-tess/

Over the next two decades, we'll be getting empirical data as we start probing known exoplanets' spectra for signs of atmospheres, and that will be the answer that really matters.

Posted by: Tom Tamlyn Aug 19 2021, 05:24 PM

The idea of living in a solar system with titanic high-energy flares screaming (metaphorically) overhead is nonetheless scary, even if they miss the planet ... usually.

Posted by: HSchirmer Aug 19 2021, 08:47 PM

QUOTE (Tom Tamlyn @ Aug 19 2021, 05:24 PM) *
The idea of living in a solar system with titanic high-energy flares screaming (metaphorically) overhead is nonetheless scary, even if they miss the planet ... usually.

Well, it makes the sample return to Earth a bit easier if we can figure out how to make a "plasma magnet drive."

Posted by: JRehling Oct 12 2021, 04:13 PM

An exciting and new method for detecting candidate exoplanets: Radio astronomy detection of planetary magnetospheres, akin to the detection of radio waves from Jupiter which goes back decades.

I haven't found access to the paper, but this SciAm article describes one of the candidate planets as a Hot Earth 26 light years away.

This means of detection may not give us the kind of information about the planet that we get as a consequence of detection with the transiting and radial Doppler methods. However, it's also exciting as it is not very prone to noise from the associated star, and it gives us a new kind of information that is of intrinsic interest and has previously been impossible.

There's a bit of supposition that a big difference between Venus and Earth, evolutionarily, comes down to Venus's lack of a magnetic field. Here's a kind of exoplanet science that speaks directly to that question.

https://www.scientificamerican.com/article/auroral-exoplanets-could-help-boost-searches-for-alien-life/

Posted by: Hungry4info Oct 12 2021, 11:17 PM

QUOTE ("JRehling")
I haven't found access to the paper, but this SciAm article describes one of the candidate planets as a Hot Earth 26 light years away

Check out this paper -- it seems to be the first reference to this candidate at GJ 1151.
https://www.nature.com/articles/s41550-020-1011-9
(Edit: I realize now you must have seen that -- the link is in the article you posted)

It's worth noting that in February, there was a http://arxiv.org/abs/2102.02233 of an RV detection of a planet that could explain the radio behaviour of the system, but a http://arxiv.org/abs/2103.10216 seemed to cast doubt on it.

Posted by: JRehling Oct 13 2021, 05:26 AM

The Perger, et al paper that finds no evidence for the planet expresses the conclusion in a confusing way, placing upper limits on the minimum mass (eg, if sin i =1). That doesn't place upper limits on the maximum mass (eg, if sin i <1), so if the orbit were more or less face-on, there could be a planet of whatever mass. It's relatively unlikely for a randomly-oriented orbit to have low sin i, but this certainly doesn't rule out a planet with earthlike (or greater) mass that could produce the aforementioned radio emissions.

Posted by: dtolman Feb 10 2022, 04:14 PM

https://www.eso.org/public/news/eso2202/ Orbits at about 1/10 Mercury's distance, and potentially has a mass of .26 earth - the lightest planet ever found using the Radial Velocity method.

Posted by: g4ayu Feb 11 2022, 07:59 AM

Planetary bodies observed in habitable zone of dead star:-
https://ras.ac.uk/news-and-press/research-highlights/planetary-bodies-observed-habitable-zone-dead-star

Posted by: StargazeInWonder Jun 18 2022, 07:06 PM

TESS finds a star with two hot transiting terrestrial planets 33 light years away.

https://news.mit.edu/2022/multiplanet-system-nearby-0615

These are great candidates for JWST to study their atmospheres, if the high temperatures haven't stripped any such atmospheres away.

It's also possible that the system would also have more temperate terrestrial planets orbiting farther out, which may not be transiting.

Posted by: StargazeInWonder Sep 20 2022, 06:19 AM

TESS has found a system with two planets somewhat larger than Earth, one of which receives 91% the irradiation of Earth from its star. The other receives about twice the irradiation of Venus. Their mass has not yet been characterized.

https://arxiv.org/abs/2209.02831

Interestingly, this star and TRAPPIST-1 are the two coolest stars known to have exoplanets and both have planets comparable to Earth in size and irradiation.

Both planets, LP 890-9 b and c, will be great targets for JWST to examine for atmospheric composition. LP 890-9 c immediately becomes one of the most intriguing exoplanets known.

Posted by: StargazeInWonder Jan 13 2023, 02:54 PM

Not a typo: TESS has discovered a second candidate earthlike planet in the same system where it had made its first such discovery.

TOI 700 e is a little smaller than TOI 700 d, and despite the later discovery and higher letter designation, it orbits closer in than "d", not farther out. It took more observations to discover because its smaller size leads to less prominent transit signals.

As TOI 700 d was not a promising candidate for characterization by JWST, and that's probably true of the new discovery as well, so we may be waiting quite a while until we know more, but as telescopes for characterizing transiting candidate earthlike planets come online, this will be one of the more promising targets waiting for us to make those observations.

https://www.jpl.nasa.gov/news/nasas-tess-discovers-planetary-systems-second-earth-size-world

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