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Apparent size of Andromeda galaxy compared to the Moon
- possiblydrunk 4y agoOh 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.
- ISL 4y ago"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!"
- possiblydrunk 4y agoThat's beautiful. Forgive my ignorance -- what's that from?
- loganwedwards 4y agoAhh, great quote from Battlestar Galactica.
- aaronbrethorst 4y agoPlease no one offer any more context! Anything else might end up being a spoiler for folks who haven’t had the chance to enjoy it yet :)
- ISL 4y agoPrecisely why I left it un-referenced :).
- p1esk 4y agoIs it a book, or TV show, or?
- simonh 4y agoIt’s from the reboot of the TV show in the early 2000s. An incredible show.
- p1esk 4y agoThanks! Is it similar to Expanse?
- ISL 4y agoIf you like anything in the spacefaring sci-fi genre and haven't yet watched the 2000's iteration of Battlestar Galactica, you're in for one hell of a treat. Be forewarned. It is very difficult to avoid binge-watching the show.
- p1esk 4y agoI did like Expanse, but I tried to watch a few of the older Star Trek and/or Star Wars movies (don't remember the difference), and I didn't like them at all.
- 4y ago
- RcouF1uZ4gsC 4y ago> 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.
- ISL 4y agoThe wind you feel today probably has a meaningful supernova component.
- shagie 4y agoEven the neutrinos from a supernova would be enough. https://what-if.xkcd.com/73/ https://what-if.xkcd.com/73/ > How close would you have to be to a supernova to get a lethal dose of neutrino radiation? > The phrase "lethal dose of neutrino radiation" is a weird one. I had to turn it over in my head a few times after I heard it.
- raydiatian 4y ago> Only one neutrino will hit you every few years Ah, the excuse I’ve been looking for. “Can’t come into work today, was hit by a neutrino this morning. Need to rest up.”
- somat 4y agoAn even better one is proton decay. Proton decay is theoretically possible but has never been observed. and perhaps somewhere in the vast universe one might have done so... maybe. So I like to blame it on many of life's unexpected events. https://en.wikipedia.org/wiki/Proton_decay https://en.wikipedia.org/wiki/Proton_decay
- d0mine 4y ago"there are about a trillion neutrinos from the Sun passing through it every second."
- PhasmaFelis 4y agoThat's exactly the point, isn't it?
- wruza 4y agoI relate so much to every bit of it. Being a human is not a blessing, but a curse truly absurd one for a conscious being.
- specialist 4y agoI think humans would relate to each other very differently if the stars (Milky Way) were normally visible.
- dreamcompiler 4y agoLikewise 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.
- nullc 4y agoIf it's less real to see something with an instrument-- are people who need glasses to see blind? :D
- tombh 4y agoI 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. 1. https://www.reddit.com/r/spaceporn/comments/1u0dxs/andromedas_actual_size_if_it_was_brighter/ https://www.reddit.com/r/spaceporn/comments/1u0dxs/andromeda... 2. https://news.ycombinator.com/item?id=22992384 https://news.ycombinator.com/item?id=22992384 3. https://apod.nasa.gov/apod/astropix.html https://apod.nasa.gov/apod/astropix.html
- got2surf 4y agoThank you! For making the image, and sharing story behind it
- quickthrower2 4y agoVery good image, thanks for sharing it out there. Not even JWST could do that ha ha :-) Do you mind if I ask: is that image CC licensed at all?
- tombh 4y agoThank you :-) The base image is indeed public domain: https://www.flickr.com/photos/srahn/9013096528 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.
- Archelaos 4y agoI 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.
- javajosh 4y agoJust 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.
- spindle 4y agoI believe it was Lemaître who first discovered that! Just in case it matters.
- djmips 4y agoApparently, there was lively debate prior to it being settle by Lemaître and Hubble. I like the original name of 'island universes' https://physicsworld.com/a/shapley-curtis-and-the-island-universes-controversy/ https://physicsworld.com/a/shapley-curtis-and-the-island-uni...
- exitb 4y agoTo be clear, people have discovered galaxies earlier, but didn’t understand their true nature. Hence, the discussed galaxy was first known as “Andromeda Nebula”.
- mnw21cam 4y agoAnd 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.
- jader201 4y agoIt 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.
- thfuran 4y agoAndromeda 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.
- dang 4y agoOk, we've consed "apparent" onto the title above.
- haimez 4y agoThank you for your cons-cientious moderation!
- ronnirradd 4y ago
- dylan604 4y ago> 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. [0]https://www.timeanddate.com/astronomy/measuring-the-sky-by-hand.html https://www.timeanddate.com/astronomy/measuring-the-sky-by-h...
- somat 4y agoThis (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.
- ISL 4y agoI 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.
- pophenat 4y agoA 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.
- bumbledraven 4y agoOr you can buy image stabilizing binoculars which mechanically keep the image steady in your view despite the slight motion of your hands.
- sph 4y ago
- em-bee 4y agoi saw a similar image in a documentary video. i was so impressed by it that i took a screenshot, intending to look up more about that some time. looks like i don't have to do that anymore because HN brought it to me.
- 8bitsrule 4y agoIt'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. US: https://www.go-astronomy.com/dark-sky-sites.php https://www.go-astronomy.com/dark-sky-sites.php World: https://blue-marble.de/nightlights/2019 https://blue-marble.de/nightlights/2019
- ByThyGrace 4y agoI 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.)
- ggm 4y agoignoring actual size, what is the APPARENT size of the object from the same observers point of view, if they could "see" all the fainter magnitude stars which make it up? thats what this shows. the arc of vision the moon covers, against the arc of vision the galaxy covers, for the same observer, if they are drawn "together" its right there in the title. Apparent size, is about what things "appear" to be to you, the observer.
- bumbledraven 4y agoThe apparent size of the Andromeda galaxy (M31) is 3.167 square degrees [1], and the angular diameter of Moon ranges from 29.3 to 34.1 arcminutes [2]. Using area = πr², the apparent size of Moon ranges from 0.1873 to 0.2537 square degrees. Hence M31 should appear to be roughly 12.5 to 16.9 times the size of Moon. [1] https://en.wikipedia.org/wiki/Andromeda_Galaxy https://en.wikipedia.org/wiki/Andromeda_Galaxy [2] https://en.wikipedia.org/wiki/Moon https://en.wikipedia.org/wiki/Moon
- deleted 4y ago[deleted]
- rendall 4y ago> Hence M31 should appear... I don't think square degrees should be used here. People don't visually approximate that way when fitting round objects into a space. Andromeda 3.167° across its longest length. Moon 0.518°. That's about 6 moons across the longest length. Andromeda is 1° across the shorter axis. Approximately 2 moons. So, appearing about 10-12 moons in area maximum, shaving some off at the corners.
- bumbledraven 4y agoI should have mentioned that area = π r² is only an approximation for the moon’s apparent size in square degrees. What we really want to calculate is the surface area of the spherical cap (on a unit sphere) with the same angular diameter as the moon. A formula for that is 2π(1 – cos r) [1], where r again is the radius of the moon in degrees. In this case, the two formulas give the same result to four significant digits (e.g. [2]). [1] https://en.m.wikipedia.org/wiki/Spherical_cap https://en.m.wikipedia.org/wiki/Spherical_cap [2] http://www.wolframalpha.com/input/?i=2pi%281-cos%5B%2834.1%2F60%2F2%29%2Api%2F180%5D%29%20steradians%20to%20square%20degrees http://www.wolframalpha.com/input/?i=2pi%281-cos%5B%2834.1%2...
- anandrmedia 4y agoI got confused with the term "size compared to moon".
- ReptileMan 4y agoBegs the question - if everything was brighter what would be the biggest object - excluding solar system and milky way. Quasar, Pulsars, Filaments...
- 5mv2 4y agoFun classics for star lovers: - The three body problem - The hitchhiker’s guide to the galaxy
- dirtyid 4y agoWhich animal has eyes best biologically tuned to star gaze? And when cam I get that transplant.
- lopuhin 4y agoA 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.
- mandmandam 4y agoAahh, it's coming right at us!!
- superposeur 4y agoI’ve heard it said that the angular size of many astronomical targets is not so small — that the real limit to seeing them is the overall amount of light collected. But then some basic sense of scale eludes me: 1) isn’t most astronomical stuff insanely far away, to the point that it would have to be cosmically large to take up a medium angular size? 2) the angular “real estate” in the sky is severely limited (4pi solid angle) so wouldn’t this get quickly used up such that we could only see a small collection of such objects? (Andromeda is already taking up a huge patch of the night sky!) Of course these are quantitative questions that can be settled by calculation, but does anyone have relevant intuition to offer?
- zoomablemind 4y agoThe image of M31 in the sky reminded me of that StarTrek DS9 wormwhole. How's going there, Cmdr Sisko? I do agree that without the myriad of stars from our Milky Way the M31 looks very much pasted in.
- nullc 4y agoA 200mm telephoto lens on a DSLR/mirrorless on a tripod can take a passable photo of Andromeda from the bay area with a bit of technical technique (well perhaps not in the most light polluted parts,...). The key to doing it with nothing other than a tripod is merging a lot of relatively short exposures (e.g. a half second) to avoid blurring the image. Likewise, a fast telephoto w/ live view on a modern camera is an interesting alternative to binoculars-- especially because image stabilization is common on such devices while IS binoculars are a pretty niche thing. (Obviously binoculars are less expensive, but if you already have an expensive camera...)