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17h
comment Could spy satellites use laser guide stars (for adaptive optics)?
@HDE226868 Well, it is about adaptive optics used by astronomers. If astronomy isn't the right place to ask if an Earth observing space telescope could use that technology, then where?
1d
asked Could spy satellites use laser guide stars (for adaptive optics)?
Jul
31
awarded  Investor
Jul
30
comment Is the diameter of the observable universe a relative quantity?
Yes of course I got that to begin with. A square root here or there doesn't change much. But what do you really mean with a speedy passer by here observing another size of the visible universe? Something wrong is hard here, either your formulation, or my brain (or in worst case: reality).
Jul
30
comment Is the diameter of the observable universe a relative quantity?
(1−0.8662²)= 1/2 Maybe it is true in astronomy, I can't tell anymore. But it is the concept that is the issue anyway.
Jul
30
comment Is the diameter of the observable universe a relative quantity?
So if a civilization passed us by, which has been traveling at 0.866 c since soon after Big Bang, the visible universe would look 1/5 smaller to them as it does to us next to them at the same time? They would make different measurement of the CMB? (This is the weirdest thing I've heard since that stuff about galaxies looking larger the further away they are when z is big).
Jul
30
asked How easy is it to mine water on Ceres?
Jul
29
comment How common are exoplanets in distant orbits?
Great answer! A single transit is unreliable, but microlensing gives certain exoplanets, right? (And I like using the word "substantial" for big instead of "significant". Is "a significant error bar" a statistical concept? :-) Sorry for the picking a nit).
Jul
29
revised Could evaporating hot Jupiters have metallic hydrogen on their surfaces?
added 31 characters in body
Jul
29
asked Could evaporating hot Jupiters have metallic hydrogen on their surfaces?
Jul
29
asked How common are exoplanets in distant orbits?
Jul
28
comment How large must an object be to be seen through a telescope?
"at infinity" is a funny expression, since stuff look larger the further away they are, at z++. In astronomy, where else.
Jul
25
revised Why do some artificial satellites decrease and increase in brightness multiple times?
Added "artificial" to the headline
Jul
23
comment why does pluto have a high orbital inclination
AFAIK, the basic models today say that Pluto formed in a circular orbit in a thin protoplanetary disk, like all planets. Pluto's orbit became eccentric and inclined because of gravitational interaction with migrating giant planets soon after their formation.
Jul
21
comment Can a galaxy splits into multiple galaxies?
Does the dark matter halo also split up and follow the debris in those small starburst galaxies?
Jul
21
asked Has SETI data been used for astrophysics? How, or why not?
Jul
21
revised How will the Breakthrough Initiatives affect other astronomy observations?
edited title
Jul
21
asked How will the Breakthrough Initiatives affect other astronomy observations?
Jul
21
comment Can a galaxy splits into multiple galaxies?
Maybe if it collides with two other galaxies simultaneously :-p
Jul
20
asked Could an ejected “extra ice-giant” still be lurking in distant solar orbit?