Example of a mass orbiting more massive, less luminous body?

  • Context: Undergrad 
  • Thread starter Thread starter Deadstar
  • Start date Start date
  • Tags Tags
    Body Example Mass
Click For Summary

Discussion Overview

The discussion explores whether a more luminous, less massive body can orbit a more massive, less luminous body, particularly in the context of binary systems. Participants consider various scenarios, including extreme cases like black holes and more typical stellar configurations.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions if a more luminous, less massive body can orbit a more massive, less luminous body, suggesting a mass ratio of 10% or less.
  • Another participant cites the example of a white dwarf orbiting a black hole, where the black hole is more massive yet less luminous.
  • There is interest in less extreme cases, such as a star orbiting a non-black hole body, with considerations of luminosity equations and density.
  • A participant notes that only degenerate objects can be less luminous than a star of the same mass and provides the example of a red dwarf orbiting a white dwarf, which can be less luminous yet hotter.
  • It is mentioned that all stars in the Milky Way are more luminous and less massive than the supermassive black hole at the galactic center, indicating that such orbits do occur.

Areas of Agreement / Disagreement

Participants express varying levels of agreement on the possibility of such orbits, with some providing specific examples while others seek clarification on less extreme cases. The discussion remains unresolved regarding the general conditions under which these orbits can occur.

Contextual Notes

Participants reference luminosity equations and the conditions required for different types of stars and celestial bodies, indicating that assumptions about mass, density, and temperature play a significant role in the discussion.

Deadstar
Messages
99
Reaction score
0
Hey folks, I'm trying to find out if a more luminous, less massive body can orbit a more massive, less luminous body (is this an obvious question?). Can such a thing happen? Can it happen in a binary system perhaps..?

By less massive I'd also like to know if it can mean the smaller mass being say, 10% or less of the mass of the larger mass perhaps.
 
Astronomy news on Phys.org
Well, to take an extreme case you could have a white dwarf in orbit around a black hole, in which case the black hole is more massive yet less luminous.
 
Yeah I had thought about black holes. I'd be interested in the less extreme cases such when one of the bodies is a star and the other is not a black hole. My knowledge on this kinda thing is pretty low though and all I really have to go on are luminosity equations for black bodies relating luminosity to the bodies radius and temperature.

I'm guessing it will come down to one of the bodies, the more massive one, being denser than the other while having similar temperatures..?
 
Deadstar said:
Yeah I had thought about black holes. I'd be interested in the less extreme cases such when one of the bodies is a star and the other is not a black hole. My knowledge on this kinda thing is pretty low though and all I really have to go on are luminosity equations for black bodies relating luminosity to the bodies radius and temperature.

I'm guessing it will come down to one of the bodies, the more massive one, being denser than the other while having similar temperatures..?

Only degenerate objects can be less luminous than a star of the same mass. A less dramatic example than having a black hole as the heavy part of a binary is a red dwarf orbitting a white dwarf. Given sufficient time to cool the white dwarf can be less luminous, yet hotter, than the red dwarf. They can't orbit too close together or else there'd be mass exchange between the stars and the red dwarf would end up much heavier. I suppose it's possible for a brown dwarf to gain enough mass from a red giant over-spilling onto it to become a red-dwarf.
 
All the stars in the Milky Way are more luminous and less massive than the super massive black hole at the galactic center and they all orbit it.

So, yes.
 

Similar threads

  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 10 ·
Replies
10
Views
2K
  • · Replies 21 ·
Replies
21
Views
3K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 2 ·
Replies
2
Views
3K
Replies
1
Views
2K
  • · Replies 11 ·
Replies
11
Views
4K
  • · Replies 86 ·
3
Replies
86
Views
9K
  • · Replies 13 ·
Replies
13
Views
2K