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Nearby Exoplanets
JRehling
post Mar 23 2021, 06:19 PM
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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.
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JRehling
post Mar 30 2021, 08:37 PM
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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.
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