Circular orbits of small exoplanets: Which Earth-sized exoplanets are potentially habitable?

Viewed from above, our solar system's planetary orbits around the sun resemble rings around a bulls-eye. Each planet, including Earth, keeps to a roughly circular path, always maintaining the same distance from the sun. For decades, astronomers have wondered whether the solar system's circular orbits might be a rarity in our universe. Now a new analysis suggests that such orbital regularity is instead the norm, at least for systems with planets as small as Earth.

Source

(eta: sorry all, I somehow forgot to include the source...)

Interesting...the presence of smaller, Earth sized, planets help make orbits more circular...I found this today in one of my news feeds, and thought it interesting.

Being someone who is only just starting to learn about exoplanets, I didn't even think about the shapes of orbits, and thus, even armed with all of the appropriate data, was rather ignorant of this...I always like it when I get the opportunity to learn...even better in this case as will get to apply this new knowledge.

a reply to: tanka418

Good thing your link stated "roughly circular"…

neither 'round' nor 'oval', they are all elliptical.


Yahooo...

a reply to: tanka418

It's really significant, because an elliptical orbit that results in the minimum distance being half the maximum also results in radiation intensity being four times as great at the minimum (due to the inverse square law). This is quite a difference.

There are several possibilities. One is that planets with highly elliptical orbits either don't intersect or otherwise significantly interact with other planet's orbits, or else they are too young to have had such interaction yet. A popular idea for the formation of our own solar system is that it formed with many more than 8 planets, or planet-like objects, but only 8 survived.

Those that didn't survive may have been flung out of the solar system, or flung into the sun, through gravitational interactions, or as in the case of the hypothesized Theia, collided with another planet (in that case, Earth).

So you may get all kinds of elliptical orbits forming initially, but if there are a lot of planets the highly elliptical orbits may have a hard time surviving long-term due to interactions. If there aren't a lot of other planets to interact with the elliptical orbit, there's no reason it can't survive, though I agree with the article that it probably wouldn't be the best place for life as we know it.

a reply to: intrptr
Yes you can see the eccentricity data here which is a measure of how "not circular" the orbit is; the bigger the number, the less circular. Mercury isn't that circular but "roughly circular" is probably not a bad description for the rest. The orbit of Venus is closest to a circle of our eight planets.

Interesting...after checking the current data it seems that of the 2015 known / confirmed exoplanets only 36% (737)
have an orbital solution.

And of those 727...only 50 have an eccentricity like Earth (< 0.02).

You can view the latest exoplanet list and their properties here: Latest Exoplanet Data