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Transiting Exoplanet Survey Satellite
JRehling
post Jan 4 2019, 06:22 AM
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There's a lot to pore over here! Just perusing casually, I see case 259962054 looks like a really interesting terrestrial planet candidate. As I see the numbers, it has an equilibrium temperate a bit cooler than Mars and a radius of 1.2 Earths – certainly within the realm of possibility of earthlike conditions.


Many months of reading Kepler data tables makes this a lot more explicit to me than it otherwise would be. They are presenting the data in Kepler-like formats, which is great, because that framework was very well thought out.

It's going to be great to get more of this data, a somewhat more condensed summary of the information, and more evaluation of the candidates.
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JRehling
post Jan 5 2019, 04:27 PM
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Having taken a bit more time to review the data release, with a mind towards locating the more earthlike candidates, I'll emphasize the following:

There are about 40 stars that have a planet candidate with a period of 8 or more days. I focused on these since shorter periods are very likely to be very hot, even for small M dwarfs.

TESS, for those who don't know, will look at most of the entire sky, but will look, in the primary mission, at most of the sky for only about one month, and can therefore only find, in those parts of the sky, planets with quite short periods. However, the observed segments overlap, and in the overlap, planets with longer periods can be found. This data release covers three observational periods, so the longest possible period offering three transits is about two months.

In this data, I found five planet candidates worthy of being called somewhat earthlike, including two in the same system. Of those, none really hits the Goldilocks area of parameter space "just right." We have some too big, some too hot, and some too cold, but given our lack of understanding of how planets evolve, I think these five are worth of mention. I'll list simply the star's TESS ID, magnitude, orbital period (days), planet radius (in Earths), and equilibrium temperature (K).

12421862 9.85 20.4 1.6 325
37749396 8.43 13.5 1.6 466
12421862 11.24 3.8 1.1 379
12421862 11.24 10.6 1.4 268
259962054 12.17 52.0 1.2 171

Important reference: The equilibrium temperatures of Venus, Earth, and Mars are 301, 255, and 207, respectfully. Only the fourth of those planets falls in that range. However, remember that these parameters have considerable uncertainty, and we have no good knowledge of what a climate might be for any of them.

The variable I'd most like to add, and can perhaps derive, is distance in light years, because these are all obviously quite close compared to any of the Kepler discoveries. Note that "magnitude" isn't a simple constant for each star, but depends upon the wavelengths to which a telescope responds.

To put this further in context, the TESS main mission will have 26 such observational periods, of which this data includes only 3, so we may naively expect a 9x increase in the results, but that both understates and overstates the matter in various ways. For the stars that TESS observational periods overlap, we will also explore outward, seeing longer periods, and that may turn up additional earthlike planets at greater distances from hotter stars. However, some candidates may prove not to be real.

Still, this gives us confidence that tens of generally earthlike planets will be found by TESS, and these are particularly exciting in terms of the potential for follow-up science. These, along with the handful of terrestrial planets already know to orbit nearby stars, will be the systems that JWST and the ELT will observe and maybe give us actual observed data for the planets' atmospheric composition and temperature. This is the start of a very interesting decade, and some of those planets on the list above may become very famous in the next few years.
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antipode
post Jan 5 2019, 09:17 PM
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Very interesting taster of things tp come!

12421862 11.24 10.6 1.4 268 looks especially interesting.

Are we likely to see discovery papers soon on the arxiv, or will they wait til RV followup?

P
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Hungry4info
post Jan 5 2019, 09:28 PM
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Depends on the system. All of these candidates can be found here. This site is regularly (assuming the U.S. government is not shut down) updated as TESS data rolls in. Others will work to confirm them with RV.

GJ 143 + HD 23472, https://arxiv.org/abs/1812.04501
Pi Men, https://arxiv.org/abs/1809.05967
LHS 3844, https://arxiv.org/abs/1809.07242
HD 2685, https://arxiv.org/abs/1811.05518
HD 202772, https://arxiv.org/abs/1810.02341
HD 1397, https://arxiv.org/abs/1811.01882
HD 219666, https://arxiv.org/abs/1812.05881

Altogether nine planets have been confirmed so far (two at HD 23472).

QUOTE ("JRehling")
12421862 9.85 20.4 1.6 325
37749396 8.43 13.5 1.6 466
12421862 11.24 3.8 1.1 379
12421862 11.24 10.6 1.4 268
259962054 12.17 52.0 1.2 171


Which correspond to GJ 7, GJ 1008, LHS 1140 (TIC 92226327) and 2MASS J02520450-6741155. Both planets at LHS 1140 have been discovered (and confirmed) prior to TESS.
LHS 1140 b https://arxiv.org/abs/1704.05556
LHS 1140 c https://arxiv.org/abs/1808.00485


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JRehling
post Jan 6 2019, 06:46 PM
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That's a fantastic update (backdate!). How did you unify the TESS results with the existing discoveries? RA and Dec are given for each star, so you could do it that way. The number of nearby red dwarfs is not limitless, but I'd like to have a method to merge the data automatically if possible, as TESS data pours in.

The LHS 1140 system is about 40 light years away, the same as TRAPPIST-1, which, with ten planets between the two systems, will make ~40 light years an interesting distance threshold in discussions of nearby exoplanets.
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Hungry4info
post Jan 6 2019, 07:01 PM
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QUOTE ("JRehling")
How did you unify the TESS results with the existing discoveries?

Just going through SIMBAD and searching each RA+Dec. If you want I can e-mail you an Excel document containing each TOI and their respective ID where known.


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Hungry4info
post Jan 8 2019, 01:56 AM
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And now TOI-197.01 (HIP 116158 / HD 221416) is confirmed.
https://arxiv.org/abs/1901.01643


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Hungry4info
post Jan 29 2019, 02:01 AM
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Five low-mass planet candidates orbiting TYC 8856-192-1 (TOI-125), two of which have been confirmed.
https://arxiv.org/abs/1901.09092


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Hungry4info
post Jan 30 2019, 11:20 AM
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An Eccentric Massive Jupiter Orbiting a Sub-Giant on a 9.5 Day Period Discovered in the Transiting Exoplanet Survey Satellite Full Frame Images
https://arxiv.org/abs/1901.09950

TOI-172 = TYC 6932-301-1


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JRehling
post Aug 17 2020, 02:16 AM
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As of July 2020, TESS has completed its primary mission and is now beginning an extended mission that will approximately repeat the main mission.

While the observations of the primary mission are complete, the analysis is not nearly complete. Having found only 66 confirmed new planet discoveries so far, this will inevitably increase considerably even if no new observations occurred, although I couldn't begin to estimate what the right multiplier is for the future yield.

However, the extended mission provides the opportunity for completely new kinds of discoveries. TESS only viewed most of its primary mission targets for 27.4 days each, which means that a transiting planet with an orbital period less than 9.2 days was guaranteed to exhibit three transits during the observations, a planet with an orbital period of 9.2 to 13.7 days might exhibit three transits, and a planet with a longer orbital period could not exhibit three transits, but a planet with an orbital period up to 27.4 days might have exhibited two transits.

It's the planets in that range from 9.2 to 27.4 days that will benefit from the extended mission, when more observation time makes it very likely that planets with one or two previously recorded transits will be observed in a third or second and third transits. So, the window of orbital periods around each star will widen considerably. This will moreover mean that we can find candidate earthlike planets orbiting larger and brighter stars with the extended mission data. Even better, a second extension would suddenly widen that enormously, creating opportunities for the discovery of candidate earthlike planets orbiting sunlike stars. In essence, the primary mission lets us find candidate earthlike planets circling M dwarfs, the extended mission will push that out to brighter, hotter M dwarfs, and a second extended mission would push it out to K and G dwarfs.

So, if TESS has finished a third of its eventual observations, we may have only a minuscule fraction of the interesting discoveries in hand now. This is quite different from a mission like a planetary orbiter where one expects much of the scientific value to come with first observations.

By the way, TESS's observational windows overlap in some weird but fortuitous ways, so some stars have already been observed enough to allow discoveries in longer orbital periods. But the best is almost certainly yet to come.
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antipode
post Aug 17 2020, 04:23 AM
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I almost get the feeling that the discovery rate thus far is a little disappointing? Is that so? Does it accord at all which what was predicted?

I'm sure there are many many more discoveries to be pulled out of the data, even without an extended mission, which will probably morph into an extended extended mission anyway ($$$?)

P
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Hungry4info
post Aug 17 2020, 10:39 AM
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TESS has identified over 2,000 candidate planets. The problem is that ground-based RV follow-up is resource-intensive. It has always been the bottleneck of the process toward getting these kinds of planets confirmed.
https://exofop.ipac.caltech.edu/tess/


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JRehling
post Aug 17 2020, 04:46 PM
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I don't think the results are disappointing. The results are just at a very early stage of processing, despite the fact that the observations of the main mission have concluded. A few weeks before Kepler's main mission concluded, analyses of its data had found 105 confirmed planets. That number ended up at 2,662. (Coincidentally, the candidate planets as of early 2013 was about the same as the confirmed planets as of now.)

Thanks to Kepler, we know the intrinsic frequencies of various star-planet combinations. There's no reason to suspect that the TESS sample will differ significantly from what was expected based on that. All we have to hope for is that operations are successful, which has been the case so far.

Luck will apply when expected findings for a particular type of planet is in the single digits, and then we may get lucky and find, say, six, or unlucky and find one. But it will be a few years from now before we know how that goes.
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antipode
post Aug 18 2020, 10:11 AM
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Youre right - I keep forgetting that candidates need to be confirmed by ground based RV, and that's a slow process.

P
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