Nearby Exoplanets |
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Nearby Exoplanets |
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#31
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![]() Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 ![]() |
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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#32
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![]() Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 ![]() |
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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#33
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![]() Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 ![]() |
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. |
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#34
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![]() Member ![]() ![]() ![]() Group: Members Posts: 447 Joined: 1-July 05 From: New York City Member No.: 424 ![]() |
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.
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#35
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![]() Member ![]() ![]() ![]() Group: Members Posts: 684 Joined: 24-July 15 Member No.: 7619 ![]() |
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." |
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#36
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![]() Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 ![]() |
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/...for-alien-life/ |
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#37
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![]() Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 1452 Joined: 26-July 08 Member No.: 4270 ![]() |
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 claim of an RV detection of a planet that could explain the radio behaviour of the system, but a later re-analysis seemed to cast doubt on it. -------------------- -- Hungry4info (Sirius_Alpha)
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#38
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![]() Senior Member ![]() ![]() ![]() ![]() Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 ![]() |
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.
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#39
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Member ![]() ![]() ![]() Group: Members Posts: 126 Joined: 20-April 05 Member No.: 291 ![]() |
3rd planet potentially found around Proxima Centauri by the VLT's ESPRESSO. 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.
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#40
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Newbie ![]() Group: Members Posts: 9 Joined: 23-June 09 From: Leyland U.K. Member No.: 4834 ![]() |
Planetary bodies observed in habitable zone of dead star:-
https://ras.ac.uk/news-and-press/research-h...-zone-dead-star |
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#41
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Member ![]() ![]() ![]() Group: Members Posts: 250 Joined: 14-January 22 Member No.: 9140 ![]() |
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. |
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#42
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Member ![]() ![]() ![]() Group: Members Posts: 250 Joined: 14-January 22 Member No.: 9140 ![]() |
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. |
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#43
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Member ![]() ![]() ![]() Group: Members Posts: 250 Joined: 14-January 22 Member No.: 9140 ![]() |
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-di...arth-size-world |
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#44
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Member ![]() ![]() ![]() Group: Members Posts: 250 Joined: 14-January 22 Member No.: 9140 ![]() |
Interesting observation from JWST: It has observed a giant planet orbiting Epsilon Indi A. A giant planet orbiting Epsilon Indi A had previously been discovered, but the parameters of this one are so different than those previously derived that it's almost a judgment call whether to say that the new observations are of the previously-claimed planet or to say that this is an exoplanet discovery. The parameters derived from JWST direct imaging make the planet about twice as massive and three times farther out than the estimates from radial velocity, which is quite a discrepancy, and seems to bring into question more generally the derived parameters of any outer (>10 AU) giants detected with RV; after all, Epsilon Indi is very close as stars go and the planet is quite massive.
This heightens the drama regarding nearby systems like Epsilon Eridani, Alpha Centauri, and Tau Ceti. Estimates of the Tau Ceti system seemed to have some paradoxical implications, as there were indications that the orbits might be nearly face-on, which would make the planets so massive that the cited orbital distances would not be stable. Maybe errors are being underestimated and we need to wait for direct imaging to rewrite the stories of these nearby systems. |
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