by Chris Peterson » Tue Nov 19, 2019 11:15 pm
MarkBour wrote: ↑Tue Nov 19, 2019 10:51 pm
Chris Peterson wrote: ↑Fri Nov 15, 2019 11:10 pm
MarkBour wrote: ↑Fri Nov 15, 2019 11:07 pm
A question that I find interesting here, a thought experiment I'll not be able to perform
in ipsa re.
If we were to travel 1000 light years away and look back at our Solar system with a Kepler-like instrument. According to neufer, from that distance, a Mercury transit would cause a 12.34 ppm light diminution. As the Sun seems
to us to have a 10 ppm natural variability, it might just be able to be detected above that. What I find interesting is wondering whether or not, once we were 1000 light years away, we might find that the Sun has
more variability in our observation of its output, rising to the level of 19.5 ppm, and thus masking out swift Mercury.
Why would the measured variability of the Sun change with distance? (And it is possible to detect a 10 ppm transit against 20 ppm variability. It just requires sampling enough orbits. So it might take a long time.)
As to your parenthetical comment, I'm sure you're right ... if you can get enough data and the 20 ppm variability is random, statistical analysis should be able to tease out anything that can be detected at all.
As to your question, I'm glad you asked, because it encourages me to continue my fanciful conjecture. :-)
I don't know what lies between us and the stars that Kepler imaged. We look at those suns through the entire radius of their magnetosphere and their solar winds. Through all of the debris in their solar disks. And then through the matter floating around in the interstellar medium. We tend to think of space as the clear void through which we can see everything as it really is, but I'm suspicious of that. Another question I have is whether or not it matters in which direction one would travel. Does the Sun show more variability if viewed from its north pole, or from its equator, or neither? If viewed from > about 10 times the radius of Pluto's orbit, I would expect that viewing straight through our "planetary plane" would have more variability than viewing from above the plane.
I doubt that the interstellar medium, or anything lying between stars and us, represents a measurable component of variability. There's no correlation between the light curves of very close stars, as you'd expect for something in the interstellar medium. And the time scales of variability are too fast. In rare cases material in the star systems might interfere, but we get a barely measurable signal from an entire planet; the vastly lower mass (and slower variation) of distant material in the system is probably not a factor.
The question of viewing direction is more interesting. I don't think there's a difference in "conventional" variability with direction. But some variability comes from star spots, and star spots do have favored latitudes. So over the period of stellar magnetic cycles (assuming they behave in a similar way to the Sun) I can imagine that viewing from different directions might give somewhat different results.
[quote=MarkBour post_id=297154 time=1574203875 user_id=141361]
[quote="Chris Peterson" post_id=297053 time=1573859423 user_id=117706]
[quote=MarkBour post_id=297052 time=1573859253 user_id=141361]
A question that I find interesting here, a thought experiment I'll not be able to perform [i]in ipsa re[/i].
If we were to travel 1000 light years away and look back at our Solar system with a Kepler-like instrument. According to neufer, from that distance, a Mercury transit would cause a 12.34 ppm light diminution. As the Sun seems [b][i]to us[/i][/b] to have a 10 ppm natural variability, it might just be able to be detected above that. What I find interesting is wondering whether or not, once we were 1000 light years away, we might find that the Sun has [i]more[/i] variability in our observation of its output, rising to the level of 19.5 ppm, and thus masking out swift Mercury.
[/quote]
Why would the measured variability of the Sun change with distance? (And it is possible to detect a 10 ppm transit against 20 ppm variability. It just requires sampling enough orbits. So it might take a long time.)
[/quote]
As to your parenthetical comment, I'm sure you're right ... if you can get enough data and the 20 ppm variability is random, statistical analysis should be able to tease out anything that can be detected at all.
As to your question, I'm glad you asked, because it encourages me to continue my fanciful conjecture. :-)
I don't know what lies between us and the stars that Kepler imaged. We look at those suns through the entire radius of their magnetosphere and their solar winds. Through all of the debris in their solar disks. And then through the matter floating around in the interstellar medium. We tend to think of space as the clear void through which we can see everything as it really is, but I'm suspicious of that. Another question I have is whether or not it matters in which direction one would travel. Does the Sun show more variability if viewed from its north pole, or from its equator, or neither? If viewed from > about 10 times the radius of Pluto's orbit, I would expect that viewing straight through our "planetary plane" would have more variability than viewing from above the plane.
[/quote]
I doubt that the interstellar medium, or anything lying between stars and us, represents a measurable component of variability. There's no correlation between the light curves of very close stars, as you'd expect for something in the interstellar medium. And the time scales of variability are too fast. In rare cases material in the star systems might interfere, but we get a barely measurable signal from an entire planet; the vastly lower mass (and slower variation) of distant material in the system is probably not a factor.
The question of viewing direction is more interesting. I don't think there's a difference in "conventional" variability with direction. But some variability comes from star spots, and star spots do have favored latitudes. So over the period of stellar magnetic cycles (assuming they behave in a similar way to the Sun) I can imagine that viewing from different directions might give somewhat different results.