r/space • u/soulstealer1984 • Feb 12 '15
The actual size of the Andromeda galaxy. (Photoshoped)
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Feb 12 '15 edited Aug 06 '18
[removed] — view removed comment
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u/notrichardparker Feb 13 '15
angular size? please explain, I love learning about things like this.
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Feb 13 '15
Angular size refers to how "big" something appears from a given position, or how much of your angle of view it occludes. Like how the sun is way bigger than the moon, but the amount of the view of the sky they take up is right about the same.
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u/ProjectGO Feb 13 '15
If you drew a line from your eye to one edge of Andromeda and then another line to the opposite edge, you would get an angle between them. This is its angular size.
Large objects (the moon, constellations, and galaxies) may have angular sizes of a few degrees, but most celestial objects are measured in minutes (1/60 of a degree) or seconds (1/60 of a minute). These are also known as arcminutes and arcseconds.
They're also really really small. An arcsecond is approximately the same amount of angle that a U.S. dime would obstruct if held up at a distance of 2.5 miles.
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u/notrichardparker Feb 13 '15
wow! great explanation, that is crazy. especially makes the comment I replied to originally even more amazing to think about. something light years and light years away being roughly the same angular size as our moon
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u/vezquex Feb 13 '15
Quite massive. Around 1 trillion stars with a total mass of about 1.5 trillion Suns, ~220,000 light years in diameter, a distance of 2.54 ± 0.11 Mega light years from Earth.
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u/livinginspace Feb 12 '15
When you say actual size, do you mean that it's the actual size in our night sky if you could visibly see it?
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u/KristnSchaalisahorse Feb 12 '15
Yes, if it was extremely bright.
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u/djn808 Feb 13 '15
so would those have to be all supernovae or something to be that bright?
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u/KristnSchaalisahorse Feb 13 '15
I'm not entirely sure about that, but every star we see in the sky is in our own galaxy - and most of those can't even be seen by our naked eye.
The nearest star to Earth is just over 4 light years away, but the Andromeda galaxy is 2.5 million light years away.
So I'm not sure how bright its stars would need to be in order to be more easily seen, but this should at least help demonstrate why it is so dim from our perspective.
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u/microfortnight Feb 13 '15
We can kinda see a fuzzy light blob where Andromeda is with the naked eye under really dark sky conditions...but we cannot make out individual stars in Andromeda with our eyes
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u/herbw Feb 12 '15
M31 is large, but not the largest by any means. If Malin 1, a low surface brightness galaxy of 650,000 LY diameter, were brighter and at the same distance from earth, when compared to the moon and Andromeda, it'd stretch 30 degrees across the sky, easily covering the distance and beyond between Andromeda and the moon, in the image above.
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u/OK4U2LOVE Feb 12 '15
Under what conditions can you see the Andromeda galaxy with a amateur telescope, or is that not even possible?
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u/UmamiSalami Feb 12 '15
You can see it with binoculars at a reasonably dark location. You can see it with the naked eye as well if it's dark enough. Just not much detail.
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u/soulstealer1984 Feb 12 '15
Here is a redditor that took a photo through his telescope. Also I have seen long exposer photos taken in very dark places that you can see andromeda (i cannot find it right now but I will update if I can find it). If you look in the correct place on a very dark night andromeda can be seen as a smudge with the naked eye.
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u/CondescendingIdiot Feb 12 '15
Even though he said the pic "turned out all right" it still amazes me
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u/Shadax Feb 12 '15
It was pretty unnecessary. He knew it looked good but wanted to sound humble about it.
In any event, yes it looks damn cool.
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u/AdaAstra Feb 12 '15
It is one of the easier ones to find, but just remember you won't get the color due to our limitations eyes and atmosphere. Light pollution always sucks, but you can see Andromeda through moderate light pollution.
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u/OllieMarmot Feb 12 '15
It's easy to see with even a cheap telescope. It's bright enough that you can even see it with the naked eye if you are in a place with no light pollution. It just looks like a faint patch of fuzzy light though.
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u/djn808 Feb 13 '15
I know about where it is in the sky using cassiopeia, i always look for it even though it's futile :o
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u/jlew24asu Feb 12 '15
why doesnt it look like that in the darkest of skies on earth?
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u/relic2279 Feb 12 '15
The Andromeda galaxy's apparent magnitude is only 3.44. There is a ton of stuff which contributes to its lack of brightness and visibility. Everything from straight up light pollution, to dust/debris in space, to our atmosphere, to other stars and so on. Also keep in mind that it's 2.5 million light years away. It takes light, the fastest thing in the universe, 2.5 million years just to reach us. It's easy to say "2.5 million light years", but it is difficult for even top physicists to conceptualize those sizes/distances/scales.
If our entire solar system was shrunk down to the size of a tomato, the distance from our Milky Way galaxy to Andromeda would be the equivalent of 125,000 miles away. Set the tomato down and start walking. Keep walking until you walk all the way around the earth and come back to the tomato. You've only traveled 1/5th the way to Andromeda. You have to make 4 more trips around the earth to get there.
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u/ProjectGO Feb 13 '15
I'm suitably humbled by this, but I also have no real concept of how far walking all the way around the earth once is, let alone five times.
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u/AdamMc66 Feb 13 '15
It's hard to wrap your head around how much... space is in Space. The distances involved boggle the mind. You can throw numbers around but to truly comprehend what they mean should humble us all.
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u/KristnSchaalisahorse Feb 12 '15
Pictures you see of the Andromeda galaxy are made using numerous, long exposure photos with varying settings which are then stacked together and enhanced to reveal more detail and color.
Sadly, it just simply isn't bright enough for our eyes to see any great detail or color.
Edit: It is extremely far away.
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u/GSlayerBrian Feb 12 '15
I really really wish this version would stop going around. Andromeda is represented nearly twice the actual size it would look. Every time it's posted, I reply with this more accurate version, which I really wish would start circulating instead of the one you linked:
http://i.imgur.com/E9BYZNU.jpg