I made that image![1]. And this is not the first time it's been on the front page of HN either[2]. So I'd like to share some context that I've not mentioned elsewhere before.
My father died from alcoholism in 2004. He made his living writing software (hence why I do too, and why I enjoy HN). But he also, for a short time, taught Astronomy evening classes. I've always felt short-changed by the emotional absence and traumatic passing of my male parent. But the continued virality of this image has been some sort of magical glimmer from the depths of the universe that it was still his shoulders that I stood on in order to reach where I am today. Maybe it was the glint in his eyes every time he showed me the latest APOD image[3], and the deep love with which he would explain their contexts. I made this composite image of Andromeda and the moon precisely because of that extra commentary, or rather I should say, extra love, of the night sky that my father gave me. Seeing it here, sparkling in the "night sky" of the HN front page stirs the same kind of wonder I sometimes feel catching those million year old specks of light above my head. Reminding me that though the universe is mostly cold and dark that doesn't diminish its warmth and brightness.
> You should read Nightfall by Isaac Asimov. It's a short story about a planet that has four suns so it is always daytime, except for one night every thousand years.
>> If the stars should appear one night in a thousand years, how would men believe and adore, and preserve for many generations the remembrance of the city of God!
A place where there's daytime all the time, except every once in a while is quite close to us. It's the Moon.
If you live on the near side of the Moon, then you always see the Earth hanging there in the sky in the same spot every day. It does not rise and it does not set, it just stays in place. But it goes through phases. New Earth, Crescent Earth, Half Earth, etc.
The Sun does rise and set. A "day" on the moon is half a month long. When the Sun is in the sky, the Earth is at most in "half Earth" phase. When it's nighttime though, the Earth is at least "half Earth".
And seen from the Moon, the Earth is big. Very big. Just take the Andromeda in the picture, and make it a disk. That's how big. (Actually about 15% bigger).
The Earth is also bright. Much brighter than we see the Moon on a bright night. Earth's albedo is about 3 times higher than Moon's. All in all, at "full Earth", you would receive about 40 times more light that we get here from the Moon when it's full.
In other words, when the Sun is not in the sky, you get enough light from the Earth to see around. The closer to "midnight" the more light you get, because the Earth is closer to "full Earth" phase.
Of course, when you have a solar eclipse, you stop seeing light from either the Sun or the Earth. Here on Earth, solar eclipses are quite short. The moment of full eclipse is fleeting, generally it's 3 minutes or less. On the Moon, because the Earth is so much bigger in the sky, the eclipse is long. Of course, we knew that from here: when it's a solar eclipse on the Moon, it's a lunar eclipse on Earth, and that takes hours.
It's not completely dark on the Moon when there's a solar eclipse.
It's not completely dark here either. Because of the Sun's corona. The apparent diameter of the sun is virtually identical with the diameter of the Moon as seen from the Earth, but the Sun's corona extends a bit further, so we get to see it during total eclipse.
But on the Moon, the Earth is so large that the Sun and the corona are fully obscured during total solar eclipse. What you will see instead is the Earth atmosphere. Very thin, impossibly thin, you will not be able to perceive its thikness. It will just look like a one-dimensional line. A part of it will be very, very bright. And very red. It will be a very bright, very large and very red circle in the sky.
You will also see the inner planets, Mercury and Venus. Normally you can't see them on the Moon, but during a full solar eclipse they'll be quite close to that bright circle, and they'll be very bright themselves.
And what a glory the Milky Way will be at that time. And if you are lucky, you'll see that very oblong shape that's the Andromeda. Somewhat faint, but still, much brighter than any of us here on Earth would perceive it.
I also remember reading that such a system can exist, but can’t find a reference. It’s probably not that surprising, though, given that the proposed system has one large star and five minor ones, making it similar to a system with one star and five giant planets. Putting a planet in in such a way that it only has a night every 2000 years may be the only tricky part (giving it a much smaller orbit than the minor stars would help avoiding nights, but giving it a single moon that can cause nights once every 2000 years?)
A small counterpoint. The pain of losing someone is the cost of having someone decent and good, for the time you had with them. Some of us have never felt that because we've never had someone decent to lose (though I will be glad; feel the world a better place; when one of my parents dies, and mainly indifferent when the other goes, reflecting his apparent indifference to me. Sometimes being left alone is the better option).
To all those with normal lives, make sure you count your blessings now, now when it's too late.
Sorry for weird post, but I had to say it.
Perhaps though, people should not go through life always acutely aware of what they've got. Perhaps in some ways it's better to feel your loved ones' presence but not think about it, sort of take it for granted, feel the warmth of their presence but not think about it. I don't know. Anyway, I'm glad you had him.
BTW absolutely love the pic! I just wish I had the eyesight to see it. In fact In london, I wish I could just see the stars at all...
Saying "enjoy it while it lasts" serves no purpose other than to blunt a person's enjoyment of the the thing. They will already suffer when the the thing goes away...why remind them of their future suffering, causing double the suffering? If one person has a pleasant 15 minute call with their father as a result of reading this thread, but 30 people get depressed or anxious about not having visited their parents for too long due to the normal circumstances of life, there is a net loss.
The base image is indeed public domain: https://www.flickr.com/photos/srahn/9013096528 But I don't remember where I got the image of Andromeda from. Not that I believe I have any power to claim rights over it, but I've always considered it to be affectively CC licensed.
Your awesome, thank you for sharing this comment and the image you created with the world. As someone who has struggled with a similar family history with my own father, I appreciate and am thankful for the humanity you have shared. We are all better for it. Thank you.
This (or some sort of very similar comparison) prompted me to figure out how to locate Andromeda. And I could not see anything, So I bought a nice pair of binoculars, and perhaps I could see something, but it was impossible to tell for sure. until I went camping in Arizona, I was looking at the stars, I remembered how to find Andromeda, remembered my binoculars. everything had came together and there it was! it looked like a blue mist.
But really it was a nearly spiritual experience. Out in the cold Arizona desert, more stars than I have ever seen in my life and you bring up a pair of binoculars to what looks like an empty area of sky and it too is full of stars, And there is this blue mist, the furthest thing you can see with the naked eye(at least with better eyes than mine) with billions and billions of stars contained within. I don't know, but you feel stuff under those circumstances.
I just about fell on my arse the first time I saw Saturn through my telescope, actually looking at it and seeing the rings. Rings, right around a planet, right there. I couldn't see a lot of of detail because it's a fairly small refractor but there it was, a planet with rings.
Rings. Right around a whole fucking planet. Right there for everyone with a couple of hundred quid's worth of glass and aluminium and a reasonable view of the night sky to see. Just, right there in the sky, bright and clear.
I mean, in Southern Hemisphere you can see ie Large Magellanic Cloud with naked eye, and its by definition another (albeit smaller) galaxy.
I do love astronomy and can stare at starry skies on top of mountains for half a night, but you don't need to buy some crazy equipment to see similar things, just travel a bit (or not if you live there).
I believe mankind would be mentally in a bit better place of all folks that want enjoyed starry nights more often, and maybe grokked a bit what they actually see. Humility and all.
I often recommend to beginning sky-watchers that they try looking at the night sky with a large pair of binoculars (look for large objective-lenses and not too much magnification) rather than a telescope.
The nebulae and larger Messier objects are beautiful and approachable with bright handheld optics.
A small bit of advice from me: consider the weight of the binoculars when buying them. They can be too heavy to hold for more than a minute - especially large ones made for astronomy. You will either want a tripod (which is inconvenient to carry around and set up), or you’d want the binoculars to be smaller in size.
How amazing would it be if it were as bright as in the photo though? We'd probably take it for granted, but at the same time, maybe not always. I'll sometimes marvel at the moon when you can really see its details and three-dimensionality, and that's just a moon. I expect being able to look up and see a whole galaxy with your naked eyes like that would be a pretty incredible experience.
> billions and billions of stars contained within. I don't know, but you feel stuff under those circumstances.
Obligatory link to Gigapixels of Andromeda[1]. There are other Gigapixels of Andromeda videos out there but this one also has the perfect background music.
Crazy how "billions and billions" might be an understatement, looking at how many stars appear after the 2min mark alone. And Andromeda is not even a huge galaxy[2].
If you have good eyesight (or good glasses/contacts prescription), you can see it without binoculars (at least the brighter core of the galaxy). Just don't look directly at it or it disappears, because you don't have rod cells in the middle of your field of view.
It may be obvious and this may be a bit pedantic, but the “actual size” and “size compared to the moon” part is confusing, as comparing the size of two objects is usually comparing two objects at the same scale.
If someone was completely clueless, they would think Andromeda is a teeny tiny galaxy. But it’s actually 110,000 light years wide — quite a bit bigger than the moon. :)
The title show just be something along the lines of “Andromeda in the sky if it were brighter, next to the moon”. Or just “Andromeda if it were brighter”.
I say this because I’ve seen other “X compared to Y” articles on HN (one compared planets and the sun to the moon, where the moon was a pixel), and these are all at-scale comparisons. So I was expecting something similar here from the title.
Andromeda Galaxy is visible at its actual brightness, but it appears much smaller than in that image because only the central area is bright enough to be seen. Thus the "actual size" part. I don't think anyone was going to demand a 100,000 light-year wide image based on that phrasing.
> as comparing the size of two objects is usually comparing two objects at the same scale.
It is actually quite common to hear that something in the night sky is xFullMoons distant/apart. Of course, that is a relative measurement of area of sky covered from a human's viewpoint while standing on terra firma. It's just a size/distance that is understandable by most people. Telling someone that one object is 3° from another object means nothing. Knowing that the width of the moon is roughly 0.5° means that it is the distance of 6 full moons is more relatable. So in this case, the width of the full moon is the scale
Slight tangent, there are other measurements that make things easier to navigate[0]. The width of your index finger ~1°, the width of 3 fingers ~5°, the full fist ~10°, the width of thumb/pinky fully extended ~25°. Knowing these helps find other objects.
It's even bigger than that: the diameter of the main galactic disk of Andromeda is 152 000 light years. There are additional stars orbiting the galaxy in a halo with a total diameter 220 000 light years.
In comparison, Earth's moon is very much smaller, with a diameter of less than 1 light year.
For some reason I really enjoy the way you describe the moon as having "a diameter of less than 1 light year.", which is also true of my cat and the shoe I am wearing. And everything else I have ever seen or will experience in my life.
Yeah, I realized that after it was too late to edit. I posted that after a quick Google search — I originally had no idea how big it was, but new it was more the 2x the moon :) — and of course the big “110,000 light years” it returned at the top was the radius, not the diameter.
You'd have no trouble understanding that andromeda is a large number of magnitudes bigger than the moon even if your entire astronomical education was from that Star Wars intro scroller. It's a total non-issue.
What I find surprising (really unexpected!) is how close this
"appears bigger than the moon" observation makes our neighbor galaxy: considerably less than 100 "galaxy diameters"! My intuitive understanding of the vastness of space would have expected far more emptiness. (objectively, that's certainly more than made up by the insane amounts of emptiness we already have within each galaxy, but still, so close!)
I once tried to observe Andromeda on a clear night with simple binoculars. The hardest thing was not to shake too much, to get a good view. In the binoculars it was clearly larger than the moon. It appeared like a smudge with a very soft eliptic halo. I was surprised by its size.
Just want to point out that it was only about 100 years ago humans discovered that galaxies exist. Good old Edwin Hubble doing observations from Palomar in a Southern California sky that was still good for seeing.
To be clear, people have discovered galaxies earlier, but didn’t understand their true nature. Hence, the discussed galaxy was first known as “Andromeda Nebula”.
And anyone to anyone sailing on one of those first ships to Australia, the SMC and LMC would have been really obvious in the sky. Sure, they're only dwarf galaxies, but still.
Oh man, if only we could see the deep sky like the cameras do (with long exposures/filters/etc). Space looks so underwhelming in comparison with plain human eyesight -- though it's still cool to see the stars from a dark site. Andromeda is a tiny fuzzy smudge in our eyes.
"I saw a star explode and send out the building blocks of the Universe. Other stars, other planets and eventually other life. A supernova! Creation itself! I was there. I wanted to see it and be part of the moment. And you know how I perceived one of the most glorious events in the universe? With these ridiculous gelatinous orbs in my skull! With eyes designed to perceive only a tiny fraction of the EM spectrum. With ears designed only to hear vibrations in the air. ...
I don't want to be human! I want to see gamma rays! I want to hear X-rays! And I want to - I want to smell dark matter! Do you see the absurdity of what I am? I can't even express these things properly because I have to - I have to conceptualize complex ideas in this stupid limiting spoken language! But I know I want to reach out with something other than these prehensile paws! And feel the wind of a supernova flowing over me!"
Likewise magnification for bright objects like Saturn. Saturn is usually one of the brightest "stars" in the sky, but it's just a point of light without magnification. Once you add some magnification, it looks like all those photos you've seen of Saturn with the rings. It blows your mind the first time you see it.
It's too bad it isn't brighter. I managed to see most of it one time when I was in an place with 'good seeing' and a very dark sky (150 miles from the nearest city).
I'd been looking at that part of the sky for a long time, and was astonished that something that big had always been there!
These maps may help you to find the nearest dark spots.
I would like to know if there's estimates for how long it should be before Andromeda gets near enough to be as visible as the moon in plain daylight. (All else being equal.)
A nitpick on the image Andromeda image: when viewed with telescope and in most images you can find online, the core of the galaxy and the region around the core is much brighter than the outer branches, while on the composite image it looks like the core is dimmed to make the outer branches stand out more.
So the actual bright part of the Andromeda, seen with naked eye under dark skies, is much smaller.
Readit News
My father died from alcoholism in 2004. He made his living writing software (hence why I do too, and why I enjoy HN). But he also, for a short time, taught Astronomy evening classes. I've always felt short-changed by the emotional absence and traumatic passing of my male parent. But the continued virality of this image has been some sort of magical glimmer from the depths of the universe that it was still his shoulders that I stood on in order to reach where I am today. Maybe it was the glint in his eyes every time he showed me the latest APOD image[3], and the deep love with which he would explain their contexts. I made this composite image of Andromeda and the moon precisely because of that extra commentary, or rather I should say, extra love, of the night sky that my father gave me. Seeing it here, sparkling in the "night sky" of the HN front page stirs the same kind of wonder I sometimes feel catching those million year old specks of light above my head. Reminding me that though the universe is mostly cold and dark that doesn't diminish its warmth and brightness.
1. https://www.reddit.com/r/spaceporn/comments/1u0dxs/andromeda...
2. https://news.ycombinator.com/item?id=22992384
3. https://apod.nasa.gov/apod/astropix.html
>> If the stars should appear one night in a thousand years, how would men believe and adore, and preserve for many generations the remembrance of the city of God!
Love that Reddit comment.
https://old.reddit.com/r/spaceporn/comments/1u0dxs/andromeda...
A place where there's daytime all the time, except every once in a while is quite close to us. It's the Moon.
If you live on the near side of the Moon, then you always see the Earth hanging there in the sky in the same spot every day. It does not rise and it does not set, it just stays in place. But it goes through phases. New Earth, Crescent Earth, Half Earth, etc.
The Sun does rise and set. A "day" on the moon is half a month long. When the Sun is in the sky, the Earth is at most in "half Earth" phase. When it's nighttime though, the Earth is at least "half Earth".
And seen from the Moon, the Earth is big. Very big. Just take the Andromeda in the picture, and make it a disk. That's how big. (Actually about 15% bigger).
The Earth is also bright. Much brighter than we see the Moon on a bright night. Earth's albedo is about 3 times higher than Moon's. All in all, at "full Earth", you would receive about 40 times more light that we get here from the Moon when it's full.
In other words, when the Sun is not in the sky, you get enough light from the Earth to see around. The closer to "midnight" the more light you get, because the Earth is closer to "full Earth" phase.
Of course, when you have a solar eclipse, you stop seeing light from either the Sun or the Earth. Here on Earth, solar eclipses are quite short. The moment of full eclipse is fleeting, generally it's 3 minutes or less. On the Moon, because the Earth is so much bigger in the sky, the eclipse is long. Of course, we knew that from here: when it's a solar eclipse on the Moon, it's a lunar eclipse on Earth, and that takes hours.
It's not completely dark on the Moon when there's a solar eclipse.
It's not completely dark here either. Because of the Sun's corona. The apparent diameter of the sun is virtually identical with the diameter of the Moon as seen from the Earth, but the Sun's corona extends a bit further, so we get to see it during total eclipse.
But on the Moon, the Earth is so large that the Sun and the corona are fully obscured during total solar eclipse. What you will see instead is the Earth atmosphere. Very thin, impossibly thin, you will not be able to perceive its thikness. It will just look like a one-dimensional line. A part of it will be very, very bright. And very red. It will be a very bright, very large and very red circle in the sky.
You will also see the inner planets, Mercury and Venus. Normally you can't see them on the Moon, but during a full solar eclipse they'll be quite close to that bright circle, and they'll be very bright themselves.
And what a glory the Milky Way will be at that time. And if you are lucky, you'll see that very oblong shape that's the Andromeda. Somewhat faint, but still, much brighter than any of us here on Earth would perceive it.
I remembered five; Wikipedia says six, two of which form a binary star system (https://en.wikipedia.org/wiki/Nightfall_(Asimov_novelette_an...)
I also remember reading that such a system can exist, but can’t find a reference. It’s probably not that surprising, though, given that the proposed system has one large star and five minor ones, making it similar to a system with one star and five giant planets. Putting a planet in in such a way that it only has a night every 2000 years may be the only tricky part (giving it a much smaller orbit than the minor stars would help avoiding nights, but giving it a single moon that can cause nights once every 2000 years?)
Foundation also fails because human society is chaotic so his psychohistory would never work.
To all those with normal lives, make sure you count your blessings now, now when it's too late.
Sorry for weird post, but I had to say it.
Perhaps though, people should not go through life always acutely aware of what they've got. Perhaps in some ways it's better to feel your loved ones' presence but not think about it, sort of take it for granted, feel the warmth of their presence but not think about it. I don't know. Anyway, I'm glad you had him.
BTW absolutely love the pic! I just wish I had the eyesight to see it. In fact In london, I wish I could just see the stars at all...
Do you mind if I ask: is that image CC licensed at all?
The base image is indeed public domain: https://www.flickr.com/photos/srahn/9013096528 But I don't remember where I got the image of Andromeda from. Not that I believe I have any power to claim rights over it, but I've always considered it to be affectively CC licensed.
Deleted Comment
But really it was a nearly spiritual experience. Out in the cold Arizona desert, more stars than I have ever seen in my life and you bring up a pair of binoculars to what looks like an empty area of sky and it too is full of stars, And there is this blue mist, the furthest thing you can see with the naked eye(at least with better eyes than mine) with billions and billions of stars contained within. I don't know, but you feel stuff under those circumstances.
Rings. Right around a whole fucking planet. Right there for everyone with a couple of hundred quid's worth of glass and aluminium and a reasonable view of the night sky to see. Just, right there in the sky, bright and clear.
I do love astronomy and can stare at starry skies on top of mountains for half a night, but you don't need to buy some crazy equipment to see similar things, just travel a bit (or not if you live there).
I believe mankind would be mentally in a bit better place of all folks that want enjoyed starry nights more often, and maybe grokked a bit what they actually see. Humility and all.
The nebulae and larger Messier objects are beautiful and approachable with bright handheld optics.
Obligatory link to Gigapixels of Andromeda[1]. There are other Gigapixels of Andromeda videos out there but this one also has the perfect background music.
Crazy how "billions and billions" might be an understatement, looking at how many stars appear after the 2min mark alone. And Andromeda is not even a huge galaxy[2].
1. https://www.youtube.com/watch?v=udAL48P5NJU
2. https://en.wikipedia.org/wiki/List_of_largest_galaxies
If someone was completely clueless, they would think Andromeda is a teeny tiny galaxy. But it’s actually 110,000 light years wide — quite a bit bigger than the moon. :)
The title show just be something along the lines of “Andromeda in the sky if it were brighter, next to the moon”. Or just “Andromeda if it were brighter”.
I say this because I’ve seen other “X compared to Y” articles on HN (one compared planets and the sun to the moon, where the moon was a pixel), and these are all at-scale comparisons. So I was expecting something similar here from the title.
It is actually quite common to hear that something in the night sky is xFullMoons distant/apart. Of course, that is a relative measurement of area of sky covered from a human's viewpoint while standing on terra firma. It's just a size/distance that is understandable by most people. Telling someone that one object is 3° from another object means nothing. Knowing that the width of the moon is roughly 0.5° means that it is the distance of 6 full moons is more relatable. So in this case, the width of the full moon is the scale
Slight tangent, there are other measurements that make things easier to navigate[0]. The width of your index finger ~1°, the width of 3 fingers ~5°, the full fist ~10°, the width of thumb/pinky fully extended ~25°. Knowing these helps find other objects.
[0]https://www.timeanddate.com/astronomy/measuring-the-sky-by-h...
In comparison, Earth's moon is very much smaller, with a diameter of less than 1 light year.
What I find surprising (really unexpected!) is how close this "appears bigger than the moon" observation makes our neighbor galaxy: considerably less than 100 "galaxy diameters"! My intuitive understanding of the vastness of space would have expected far more emptiness. (objectively, that's certainly more than made up by the insane amounts of emptiness we already have within each galaxy, but still, so close!)
Dead Comment
https://physicsworld.com/a/shapley-curtis-and-the-island-uni...
I don't want to be human! I want to see gamma rays! I want to hear X-rays! And I want to - I want to smell dark matter! Do you see the absurdity of what I am? I can't even express these things properly because I have to - I have to conceptualize complex ideas in this stupid limiting spoken language! But I know I want to reach out with something other than these prehensile paws! And feel the wind of a supernova flowing over me!"
The wind of a supernova flowing over you would be the end of you and everything around you.
I'd been looking at that part of the sky for a long time, and was astonished that something that big had always been there!
These maps may help you to find the nearest dark spots.
US: https://www.go-astronomy.com/dark-sky-sites.php
World: https://blue-marble.de/nightlights/2019
So the actual bright part of the Andromeda, seen with naked eye under dark skies, is much smaller.