Nearby Exoplanets |
Nearby Exoplanets |
Nov 15 2017, 04:17 PM
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
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/release...36/eso1736a.pdf |
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Jun 21 2019, 08:17 AM
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Senior Member Group: Members Posts: 3516 Joined: 4-November 05 From: North Wales Member No.: 542 |
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? |
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Jun 24 2019, 01:55 AM
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
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. |
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