Astronavigation with broken engines
March 18, 2022 4:43 AM
If you were to draw a line from Earth to Gliese 876 but then keep drawing that line for 380 light years, where would the end of the line be.
Further points for telling me how you worked it out, and maybe providing me some kind of map so that I could resolve similar queries myself.
Further points for telling me how you worked it out, and maybe providing me some kind of map so that I could resolve similar queries myself.
So about 400 light years from Earth. Since Gliese 876 appears close to Tau² Aquarii from our perspective and Tau² Aquarii is 400 light years from Earth according to Erich Karkoschka's star atlas, that's about where you'd end up.
My method was, I looked in my star atlas at the stars around there and checked their distances from Earth. People with more detailed star atlases that list more info about more stars may give an even closer star to where you'd end up.
posted by starfishprime at 6:26 AM on March 18, 2022
My method was, I looked in my star atlas at the stars around there and checked their distances from Earth. People with more detailed star atlases that list more info about more stars may give an even closer star to where you'd end up.
posted by starfishprime at 6:26 AM on March 18, 2022
This is an extremely good question advicepig.
0.032c
So I suppose what I'm actually asking is what is going to be in that neighbourhood in 12,000 years.
posted by Just this guy, y'know at 6:47 AM on March 18, 2022
0.032c
So I suppose what I'm actually asking is what is going to be in that neighbourhood in 12,000 years.
posted by Just this guy, y'know at 6:47 AM on March 18, 2022
Tau basically. The speed of galactic rotation is insanely fast compared to running out for bread (even if on mars) but the distances are huge and 12k years is not much at any cosmic scale.
One observation I recall was that when we get to Alpha Centauri, virtually all the constellations will be identical to what we see. Space is non-intuitively beeg.
posted by sammyo at 8:02 AM on March 18, 2022
One observation I recall was that when we get to Alpha Centauri, virtually all the constellations will be identical to what we see. Space is non-intuitively beeg.
posted by sammyo at 8:02 AM on March 18, 2022
Based on the title of the question, I'm wondering about the 'straight line' definition here. If the intent were to accelerate to 0.032c, reach Gliese 876 and decelerate into some sort of stable orbit near its planets, then presumably the trajectory would deflect even without deceleration. Of course, that's a much more challenging question to answer as it requires a great many more assumptions.
posted by meinvt at 10:03 AM on March 18, 2022
posted by meinvt at 10:03 AM on March 18, 2022
I decided to work out how far τ2 Aquarii will move in 12,000 years. This page gives its proper motion as -0.012 arcsec/year RA, -0.038 arcsec/year Decl. The size of the resulting vector is 0.04 arcsec/year, which over that time period gives us 480 arcsec = 0.133° = .00037 of a circle.
The circumference of a circle with radius 380 ly is 2388 ly, and .00037 of that is 0.88 ly. (It's also moving away from the sun, but will only get about 0.04 ly farther away on that axis.)
By comparison, τ2 Aquarii is about 2° away from Gliese 876 in the sky. If you actually went in a straight line from Gliese 876 you'd be about 13 ly from τ2 Aquarii.
Look at a star chart for things like this. You can see τ on that chart; Gliese 876 is much closer to δ. You might think δ is a better target, but it's only 113 ly away. Note, 1h in RA (the X axis of the chart) = 15°.
If you're wondering what is actually near that point, the answer is going to be "mostly red dwarfs, a smattering of brighter stars", which is what the galaxy looks like 15 ly from us. When we look at the sky, we see mostly very bright stars that are very far from us. But in terms of sheer numbers, it's a sea of red dwarfs.
posted by zompist at 3:28 PM on March 18, 2022
The circumference of a circle with radius 380 ly is 2388 ly, and .00037 of that is 0.88 ly. (It's also moving away from the sun, but will only get about 0.04 ly farther away on that axis.)
By comparison, τ2 Aquarii is about 2° away from Gliese 876 in the sky. If you actually went in a straight line from Gliese 876 you'd be about 13 ly from τ2 Aquarii.
Look at a star chart for things like this. You can see τ on that chart; Gliese 876 is much closer to δ. You might think δ is a better target, but it's only 113 ly away. Note, 1h in RA (the X axis of the chart) = 15°.
#/media/File:Aquarius_IAU.svg){kind=link}
If you're wondering what is actually near that point, the answer is going to be "mostly red dwarfs, a smattering of brighter stars", which is what the galaxy looks like 15 ly from us. When we look at the sky, we see mostly very bright stars that are very far from us. But in terms of sheer numbers, it's a sea of red dwarfs.
posted by zompist at 3:28 PM on March 18, 2022
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posted by automatronic at 6:25 AM on March 18, 2022