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Is that something people searching for ET life look out for? Systems with a potentially habitable planet + at least one large celestial object to draw debris to

Is that something people searching for ET life look out for? Systems with a potentially habitable planet + at least one large celestial object to draw debris towards it and away from the potentially habitable planet?

pc86 5y ago
Are we able to see far-away systems in this level of detail? I know we can calculate number of planets and rough size/makeup, but are we able to tell that Planet A is in the habitable zone and Planet B is 300x+ the mass of Planet A, etc?
- rbanffy 5y ago
  We can for a lot of systems. The shorter the orbital period, the easier they are to detect, however, and to detect Jupiter from a nearby system we’d need to be very lucky.
- LeifCarrotson 5y ago
  Yes, at least using the transit method. Sometimes, we do use the Doppler shift caused by a planet pulling the star towards or away from us. That works as long as the orbital plane is not perfectly perpendicular to us. However, it only works for large planets (and reasonably sized stars) that have sufficient gravity to make the star move fast enough to see the light shift red or blue. An earth-mass planet would be undetectable compared to a Jovian planet. The transit method requires the orbital plane to be perfectly on axis so we can observe an eclipse as the planet passes between the star and our telescope. This is rare, but works for even small planets, as long as the angle is right. And if one angle is right, it's likely that others will be close enough as well; a large planet can also be observed. In systems that are at the right angle, Kepler often found several planets: https://en.wikipedia.org/wiki/List_of_exoplanets_discovered_using_the_Kepler_space_telescope https://en.wikipedia.org/wiki/List_of_exoplanets_discovered_...
Chris2048 5y ago
Hmm, I wonder if there are lots of variables that go into "likelihood of being hit by asteroid" - e.g. the size of the central star in the first place, and the resulting radius of the hab zone. It's also of not: if earth hadn't been hit by at least some asteroids, it mightn't have any water.

pc86 5y ago

Are we able to see far-away systems in this level of detail? I know we can calculate number of planets and rough size/makeup, but are we able to tell that Planet A is in the habitable zone and Planet B is 300x+ the mass of Planet A, etc?

rbanffy 5y ago
We can for a lot of systems. The shorter the orbital period, the easier they are to detect, however, and to detect Jupiter from a nearby system we’d need to be very lucky.
LeifCarrotson 5y ago
Yes, at least using the transit method. Sometimes, we do use the Doppler shift caused by a planet pulling the star towards or away from us. That works as long as the orbital plane is not perfectly perpendicular to us. However, it only works for large planets (and reasonably sized stars) that have sufficient gravity to make the star move fast enough to see the light shift red or blue. An earth-mass planet would be undetectable compared to a Jovian planet. The transit method requires the orbital plane to be perfectly on axis so we can observe an eclipse as the planet passes between the star and our telescope. This is rare, but works for even small planets, as long as the angle is right. And if one angle is right, it's likely that others will be close enough as well; a large planet can also be observed. In systems that are at the right angle, Kepler often found several planets: https://en.wikipedia.org/wiki/List_of_exoplanets_discovered_using_the_Kepler_space_telescope https://en.wikipedia.org/wiki/List_of_exoplanets_discovered_...

Chris2048 5y ago

Hmm, I wonder if there are lots of variables that go into "likelihood of being hit by asteroid" - e.g. the size of the central star in the first place, and the resulting radius of the hab zone. It's also of not: if earth hadn't been hit by at least some asteroids, it mightn't have any water.