Русский New site

Advanced search

[ New messages · Forum rules · Members ]
Page 1 of 11
Forum » SpaceEngine » Science and Astronomy Discussions » Question about Super Earths and current detection methods
Question about Super Earths and current detection methods
desertsoldier22Date: Monday, 17.03.2014, 08:05 | Message # 1
Astronaut
Group: Users
United States
Messages: 51
Status: Offline
It is my understanding that the current method of detecting exoplanets involves measuring a wobble in the motion of its parent star as the planet orbit. Extrapolating its mass by its apparent effect on the mass of its primary. Several rocky planets with enormous masses in excess of four times that of Earth and over twice its radii have been discovered. But wouldn't the presence of several large moons around that planet throw off those mass calculations? Even in the case of Kepler 22b, which was found using a transit method throw off its apparent size measurement if it had a moon half of its mass.

I would think our own world would look larger using the radial method to find it because of our moon.
 
HarbingerDawnDate: Monday, 17.03.2014, 09:18 | Message # 2
Cosmic Curator
Group: Administrators
United States
Messages: 8711
Status: Offline
Quote desertsoldier22 ()
Even in the case of Kepler 22b, which was found using a transit method throw off its apparent size measurement if it had a moon half of its mass.

If there were a large moon/companion of a planet, transit would reveal that, either directly or through transit timing variation.

Quote desertsoldier22 ()
I would think our own world would look larger using the radial method to find it because of our moon.

Yes, by about 1%... in other words, the difference is insignificant.





All forum users, please read this!
My SE mods and addons
Phenom II X6 1090T 3.2 GHz, 16 GB DDR3 RAM, GTX 970 3584 MB VRAM
 
apenpaapDate: Monday, 17.03.2014, 12:04 | Message # 3
World Builder
Group: Users
Antarctica
Messages: 1063
Status: Offline
If you look at our own Solar System, the mass ratios between planets and their moons are always extremely large. For the gas giants and Mars especially. Even Earth, which has relatively the largest moon, is still 81 times heavier than the Moon. You've got to remember planets are three-dimensional, and so even though the Moon is only about 4 times smaller, that translates to a 64 times smaller volume. (the rest of the difference is due to a lower density)

A moon could never be heavy enough to add significantly to the mass of the planet. It'd need to be a proper binary planet, which would indeed be easy to find through the transit method.





I occasionally stream at http://www.twitch.tv/magistermystax. Sometimes SE, sometimes other games.
 
desertsoldier22Date: Monday, 17.03.2014, 19:18 | Message # 4
Astronaut
Group: Users
United States
Messages: 51
Status: Offline
But theoretically we could support a system of 3-4 luna sized objects, a superearth could support many more. If they are in a close orbit you would think they would effect it?

Added (17.03.2014, 22:18)
---------------------------------------------
Or planets in trojan orbits?

 
SpaceEngineerDate: Monday, 17.03.2014, 23:05 | Message # 5
Author of Space Engine
Group: Administrators
Russian Federation
Messages: 4795
Status: Offline
90% of superearths are discovered in close vicinity of their parent star, where existence of a moon is impossible due to tides from a star. In multi-planetary systems moons are almost impossible too, due to very close distance between planetary orbits. There are only few dozen systems that looks like our own (large distances, only 4 planets within 3 AU radius) - exomoons can exist only in that systems.




 
desertsoldier22Date: Tuesday, 18.03.2014, 04:53 | Message # 6
Astronaut
Group: Users
United States
Messages: 51
Status: Offline
Quote SpaceEngineer ()
90% of superearths are discovered in close vicinity of their parent star, where existence of a moon is impossible due to tides from a star. In multi-planetary systems moons are almost impossible too, due to very close distance between planetary orbits. There are only few dozen systems that looks like our own (large distances, only 4 planets within 3 AU radius) - exomoons can exist only in that systems.


Good point most Exo earths have been found with M-class primaries, that would make it tough. Its just so hard to believe such a massive rocky world would be geologically stable, they must be hellish places or covered with water.


Edited by desertsoldier22 - Tuesday, 18.03.2014, 04:55
 
HarbingerDawnDate: Tuesday, 18.03.2014, 09:03 | Message # 7
Cosmic Curator
Group: Administrators
United States
Messages: 8711
Status: Offline
Quote desertsoldier22 ()
Its just so hard to believe such a massive rocky world would be geologically stable

There's no fine division between rocky worlds, icy worlds, and gaseous worlds. A world of 8 Earth masses might be exclusively rock and metal, or might have a thin layer of ices atop it (like water), or it could have an extremely thick gaseous envelope. But even if it were just rock and metal, what would be unstable about it? Just because it's larger than our world?

It's much the same as if a being who grew up on Mars thought it inconceivable that a world like Earth - 10 times more massive - could be as stable as it is.





All forum users, please read this!
My SE mods and addons
Phenom II X6 1090T 3.2 GHz, 16 GB DDR3 RAM, GTX 970 3584 MB VRAM
 
Forum » SpaceEngine » Science and Astronomy Discussions » Question about Super Earths and current detection methods
Page 1 of 11
Search: