I was awestruck by this picture over at APOD. (It’s a composite, in case you skip the description.) Anyway the thing that amazed me is that we can’t see Andromeda not cause it’s so small in the sky, just cause the individual stars are so faint.
Which immediately made me wonder: this is true for how many other awe-inspiring Hubble images? Are the Pillars of Creation the size of the full moon too? (Okay, probably not those, but you get the idea) Has anyone done a map of the sky that accounts for all the stuff the human eye can’t quite see? I’m sure Andromeda’s one of the bigger things in the sky, but it’s definitely got me curious!
The Hubble has a very small field of view. This image of the Crab Nebula is a “mosaic” made up of 24 Hubble images stitched together, but the nebula is only about 8 arcminutes in size. (The moon’s diameter is about 30 arcminutes.) I think this is the largest object fully imaged by the Hubble.
But there are many other deep-sky objects larger than the moon. For example, Bernard’s Loop is 10 degrees in size - about the size of your fist with your arm outstretched. Unfortunately it’s so faint you can’t see it visually at all.
And by the way, the Andromeda galaxy is not hard to see with your naked eyes if you have a dark clear sky. Though you can’t compare it with the moon because if the moon is up, the sky will not be dark enough to see Andromeda.
But you *can *see the Andromeda Galaxy with the naked eye. You just have to get away from the towns with all that street lighting.
And BTW, it is “the Andromeda Galaxy” (or M31, if you prefer something snappier). “Andromeda” is the constellation that the Andromeda Galaxy is in. [/pedant]
Edit: I see I’ve been beaten to it. Preview is my friend…
But unless I need to go into the Outback or something, you can’t see THAT MUCH of the galaxy, right? Certainly not a glowy three-times-the-size-of-the-moon expanse like in the picture. What I’ve seen has been a faint splotch corresponding to the center of the galaxy.
You can see it a bit better if you don’t look directly at it, but instead view it with your peripheral vision. Takes a bit of getting used to, but you can observe much fainter objects this way, since your peripheral vision contains a higher density of light-sensitive rod cells, compared to your central vision which contains more color-sensitive cones which are not as light sensitive.
Just found another good example: APOD says the IC 1396 nebula is over three degrees in the sky, whereas the moon is only a half-degree. This stuff is nuts, now that I think about it - I really do want to see (or make) a 360-degree image showing all this cool stuff in the sky.
NOW you are talking. That would be great! Sure you wouldn’t be able to go outside and see them with the naked eye, but it would be nice to get the perspective and recognition of the objects. The star maps that I find in books and magazines usually have a little dotted oval indicating the position of the object and the name, but not the actual object.
Come to think of it, it would be neat to have a clickable/zoomable image to look at…let me know when it is ready, happywaffle!
Celestia does something like that: All of the deep-sky objects in its catalog are represented as zoomable images, not just points or outlines. But I don’t think they have any of the really huge, really faint objects like the Veil Nebula.
I second that someone ought to make a deep exposure view of the whole sky, to bring out all the faint objects. (With the highly luminous ones like the brightest stars adjusted downward in brightness to avoid overwhelming the exposure).
Well, of course, if you’re in Chicago, or many other large cities for that matter, you can avail yourself of their planetarium machine. Here in Chicago, I think they retired and replaced the old Zeiss gizmo at the Adler, but depending on the program they’re showing - or one they can create for you if you want to bring a huge bunch of squirmy kiddos - you can see such an array. If it’s true that there’s no place on Earth like the world, consider the joys of looking outward. xo, C.
Of course, if you want to see a lot of really huge things up there, look in the infrared. Stuff that looks like hazy smears the size of a big star look REALLLLY big like that. I imagine APOD has some of those in the archives. xo, C.
I know nothing of large galaxies when I look up to the night sky. So enlighten me…When I am up at our cabin in Vermont, no moon, and every start you can imagine is out, I can see a cloudy oblong object in the sky…I always thought that was our own milky way that we were seeing from the side view. Am I really looking at Andromeda? Or are we talking about two separate celestial bodies when we look up in the night sky?
There are a few things which might qualify as a “cloudy oblong object.” The Milky Way might reasonably be described thusly, but it’s more of a band across the sky than an oblong. It’s unlikely you’re referring to Andromeda; it’s such a faint object despite its relatively large angular size–all most people can make out with the naked eye is a small fuzzy patch where the galactic center lies. You might also be seeing the Pleiades, an open cluster consisting of seven fairly bright stars and a whole bunch of less bright ones. To many people, the seven individual main stars aren’t easily resolved to the naked eye, and the whole appears as a small, fuzzy patch.
To best answer the question of what it is you’re seeing, it would be helpful to know the time of year you’re seeing it.
In addition to the time of year, Phlospher, could you maybe give a little more detail on the size of the object? If it stretches clear across the entire sky, it’s the Milky Way, without a doubt. If it’s just a speck-sized blur, there are a few possibilities. From Vermont, the most easily-visible fuzzy object is the Orion nebula, which would mostly just be visible in the fall and winter. Besides that and the Pleiades (which probably won’t look fuzzy, unless you need glasses), all the other things, you’d really need to try hard, and have good eyesight and great skies, to see with the naked eye.
