“If you don’t like what you’re doing, you can always pick up your needle and move to another groove.” -Timothy Leary
Up in the night sky, shortly after sunset, the night sky holds some spectacular sights. Some are permanent, some are transient, some have been known for thousands of years, and some are still being discovered. Looking to the west after sunset tonight, this is what you’re likely to see.
The Big Dipper, perhaps the most famous collection of seven stars in the night sky, looms large over the horizon. As always, you can follow the “arc” of the handle to Arcturus, the orange giant that’s the brightest star in the northern hemisphere, and “speed on” towards Spica, a blue giant that’s still the 15th brightest star in the sky despite being 260 light years away.
Next to Spica, you can find Saturn, Mars, and the Moon. The Moon is just there for tonight; it will move on by by tomorrow. Saturn will be there all year, while Mars will actually pass through the line created by Spica and Saturn on August 13th. (And don’t forget to think about Mars on August 5th/6th.) But it isn’t these transient, nearby worlds that I’m here to tell you about today, nor even the stars that are many light years distant. Instead, I want us to turn millions of light years away, to the distant galaxies that lie far beyond any star in the Milky Way.
Dim, faint, and with very diverse appearances, most galaxies are either elliptical (center), or spirals (left and right). But the spiral structure isn’t always visible, as you can see, because occasionally the spiral galaxy appears on its edge from our point of view.
Today, I’d like to introduce you to perhaps the most spectacular, completely edge-on spiral galaxy in our night sky: the Needle Galaxy. To find it, find the Big Dipper and Arcturus in the night sky, and point your telescope at the area where the blue rectangle is two images above. Your finderscope will likely show you a cluster of stars like this.
This collection of stars — not at all prominent to the naked eye but spectacular through binoculars — is known as Coma Berenices, and is both a traditional and modern constellation in the night sky. There are seven bright galaxies within Coma Berenices that were included in the first catalogue of deep-sky objects by Charles Messier. But one prominent bright galaxy, the edge-on Needle Galaxy, was somehow missed.
And through a telescope, it is spectacular.
At maybe 50 million light years distant, it’s one of the closer galaxies to us in the night sky, and arguably (by me, certainly) the most spectacular galaxy that Messier inexplicably* missed in his catalogue. At even this relatively tame distance, the Needle Galaxy is caught up in the expansion of the Universe, and speeds away from us at over 1,200 kilometers per second, or about 0.4% the speed of light!
Because it’s edge-on to us, we’re able to use it as a perfect example to show how much larger the central, bulging region of a spiral galaxy is compared to the “thin-disc” portion.
The image above, by the European Southern Observatory, also shows off just how close this galaxy is to us, because the small, faint, fuzzy objects in the background here are also galaxies, only much more distant than the Needle Galaxy.
The best single-image of the Needle Galaxy, which shows off its bulge, its slightly warped disc, its various colors, and its light-blocking dust lanes that I could find for you was taken with “only” a 24-inch telescope in Arizona.
But the highest-resolution image of this galaxy? As always, we’ve got to turn to the Hubble Space Telescope for that. The field-of-view for Hubble is so small compared to this galaxy that with the Advanced Camera for Surveys, we’re unable to fit the entire galaxy into the picture.
For as far as color, sharpness and resolving the individual features within the galaxy, Hubble still can’t be beat. For a galaxy that’s this far away, we can — and this is truly amazing — identify regions where new stars have just formed: open star clusters!
By using the original resolution image, I can even pick some of them out for you.
These bright blue regions only exist where the brightest, hottest and youngest stars are located, and you can see two very prominent ones clearly, above, just beneath the light-blocking dust lane, which no doubt shrouds many more star-forming regions.
But, as with all Hubble images, my favorite thing to do is to hunt for background galaxies.
Just as spectacular as any galaxy in the night sky, coming in a variety of colors, sizes, and morphologies (that’s your astronomy word of the day; it means “shapes”), these background galaxies only appear as they do because of the great distances between them and Earth. A region of space as big as the one images by the main Hubble image — one not even containing the entire Needle Galaxy — will contain around 10,000 background galaxies, of which maybe 1,000 are visible to a diligent galaxy hunter.
Because it isn’t just the big, extended shapes above that are galaxies; it’s every distant point of light that isn’t a star within our own galaxy. The one true “Space Needle” points the way not just to a distant, island Universe, but helps give us a window into the massive expanse of space that lies beyond. And that’s from looking at just one galaxy that wasn’t even prominent enough to make it into the Messier catalogue. Well, Charles (and his assistant, Pierre Méchain), bet you wish you’d included it now!
* — There are plenty of deep sky objects that Messier missed because he couldn’t observe them from his location on Earth. While it’s hard to fault him for that, he’s got no excuse for the Needle Galaxy!