Planets <-> solar systems <-> galaxies

3,073
3

Main Question or Discussion Point

Planets <--> solar systems <--> galaxies

Have planets been observed outside of solar systems, or solar systems outside of galaxies?
 

Answers and Replies

369
0
Re: Planets <--> solar systems <--> galaxies

Have planets been observed outside of solar systems, or solar systems outside of galaxies?
Just a rogue planet floating around without a star?... I though part of the definition of a plant was that it was in orbit around a star...
 
3,073
3
Re: Planets <--> solar systems <--> galaxies

Just a rogue planet floating around without a star?... I though part of the definition of a plant was that it was in orbit around a star...
Rogue it is.
 
DaveC426913
Gold Member
18,335
1,941
Re: Planets <--> solar systems <--> galaxies

No. It is hard enough to find planets when we know almost exactly where to look and they're well lit by their star.

Even if we knew exactly where look, a rogue planet would be pretty much invisible in the darkness.
 
russ_watters
Mentor
19,028
5,187
Re: Planets <--> solar systems <--> galaxies

Our planet detection methods require them to be around stars.
 
3,073
3
Re: Planets <--> solar systems <--> galaxies

Our planet detection methods require them to be around stars.
A sensible definition for the present. It follows that binary planets are precluded.

What about the possibility of solar systems outside of galaxies?
 
russ_watters
Mentor
19,028
5,187
Re: Planets <--> solar systems <--> galaxies

A sensible definition for the present. It follows that binary planets are precluded.
I'm not sure you understood me: It's not a definition, it is a matter of technological capability.
What about the possibility of solar systems outside of galaxies?
That, too is a matter of technological capability, but also a matter of the fact that the vast majority of stars are in galaxies.
 
Wallace
Science Advisor
1,249
0
Re: Planets <--> solar systems <--> galaxies

While a 'rogue' planet would be very difficult to detect, that is not to say they don't exist. The question comes down to the definition of a planet. We really don't know very much about the formation of very low mass stars (because they are very hard to see) so it is possible that when star clusters form, there are many 'stars' which form that are not sufficiently massive to start nuclear fusion. Technically, a ball of gas that is not burning at the core is a planet (such as the gas giants in our solar system) and as such there may well be many of these lone planets out there.

Detecting them would be very hard, and certainly the way we hunt for planets around stars would never find them. We could possibly see them via microlensing, if we got lucky.
 
DaveC426913
Gold Member
18,335
1,941
Re: Planets <--> solar systems <--> galaxies

We could possibly see them via microlensing, if we got lucky.
Now there's an understatement. :wink:
 
Wallace
Science Advisor
1,249
0
Re: Planets <--> solar systems <--> galaxies

Not really, the MACHO project in the late 90's found evidence for lone microlensing lenses with masses about twice that of Jupiter, and that was using a 40 inch telescope. In general, MACHO found a lot more microlensing events when looking towards the core of the Milky Way than expected, indicating the possible presence of many low mass stars/lone planets.

Modern microlensing surveys, e.g. see http://bustard.phys.nd.edu/MPS/" [Broken] are most definately aimed at addressing this question (amongst others). You have to be lucky to see an individual event, but the theory behind these surveys is that if you keep watching enough stars you're effectively rolling the dice many times, so you end up getting lucky pretty often.
 
Last edited by a moderator:

Related Threads for: Planets <-> solar systems <-> galaxies

  • Last Post
Replies
10
Views
4K
  • Last Post
Replies
0
Views
2K
Replies
9
Views
3K
Replies
9
Views
12K
Replies
62
Views
10K
Replies
4
Views
542
Replies
19
Views
4K
Replies
14
Views
13K
Top