3 ms·

TLDR: a bright infrared source is differentiable from a dim infrared source. If (big if) you can be confident about the distance of the object, that'll help te

TLDR: a bright infrared source is differentiable from a dim infrared source. If (big if) you can be confident about the distance of the object, that'll help tell you the total power output. If you have total power output and the black body spectrum, you can gauge it's size. A brown dwarf is, notably, small. If you took Sol and put a dyson swarm around it, the eventual power output would stay the same, just shifted colder as the light is now the waste product of all the industrial activity we did with it (minus any anti matter or magic matter fabrication we did) as opposed hot plasma collisions.

lrem 5y ago
How can you get that kind of confidence? I imagine a slightly more advanced civilisation than ours can send a telescope far enough to use parallax. Are there better options?
- PeterisP 5y ago
  It's not about measuring "size" by looking at width, but rather by looking at the total power emitted (for which you need essentially just the brightness and distance) which gives you the size (mass) of the star. So the OP's point seems to be that a Sol-mass star with a Dyson sphere may have the spectrum like a brown dwarf, but it would have the total emission quantity many, many times larger than a brown dwarf can have.
  - lrem 5y ago
    > for which you need essentially just the brightness and distance Parallax, which I mentioned, can be used for measuring the distance. I'm asking if there are better alternatives for getting the distance. For objects that are sufficiently far or slow moving, we can use Earth's natural movement to get some 2 AU of parallax base. Simply wait half a year before pointing the telescope at the object again. But, for things that move fast enough and are close enough to get some arc offset, we'll get wrong results. Which maybe isn't a problem, because we can detect such movement outright? I literally have no intuition how the math here works out. Hence asking.
- dogma1138 5y ago
  A Dyson sphere or a swarm would not change the total amount of perceived energy being emitted from a star however it would change the composition of the light emitted. If you put a shade around a light bulb the amount of visible light will be reduced however if you measure the total output of the lightbulb with or without a shade it would remain the same just more shifted towards the IR spectrum as the shade would absorb visible light will get hot and emit that energy as IR.

lrem 5y ago

How can you get that kind of confidence? I imagine a slightly more advanced civilisation than ours can send a telescope far enough to use parallax. Are there better options?

PeterisP 5y ago
It's not about measuring "size" by looking at width, but rather by looking at the total power emitted (for which you need essentially just the brightness and distance) which gives you the size (mass) of the star. So the OP's point seems to be that a Sol-mass star with a Dyson sphere may have the spectrum like a brown dwarf, but it would have the total emission quantity many, many times larger than a brown dwarf can have.
- lrem 5y ago
  > for which you need essentially just the brightness and distance Parallax, which I mentioned, can be used for measuring the distance. I'm asking if there are better alternatives for getting the distance. For objects that are sufficiently far or slow moving, we can use Earth's natural movement to get some 2 AU of parallax base. Simply wait half a year before pointing the telescope at the object again. But, for things that move fast enough and are close enough to get some arc offset, we'll get wrong results. Which maybe isn't a problem, because we can detect such movement outright? I literally have no intuition how the math here works out. Hence asking.
dogma1138 5y ago
A Dyson sphere or a swarm would not change the total amount of perceived energy being emitted from a star however it would change the composition of the light emitted. If you put a shade around a light bulb the amount of visible light will be reduced however if you measure the total output of the lightbulb with or without a shade it would remain the same just more shifted towards the IR spectrum as the shade would absorb visible light will get hot and emit that energy as IR.