“The lessons of science should be experimental also. The sight of a planet through a telescope is worth all the course on astronomy; the shock of the electric spark in the elbow outvalues all theories; the taste of the nitrous oxide, the firing of an artificial volcano, are better than volumes of chemistry.” –Ralph Waldo Emerson
As a theorist, one of the challenges I face is bringing the experimental and observational sides of what we study to all of you. I understand its importance, its significance, and how it is the ultimate arbiter of our understanding. And yet, it is not my strongest suit. Nonetheless, tomorrow night (the 19th) is an important milestone: the date I take my astronomy students up to the observatory to view the night sky!
What’s sort of amazing is how much you can see through just a simple telescope — even in less-than-ideal conditions — even if you know almost nothing about astronomy.
Let me take you through it, assuming you live in the Northern Hemisphere and only know how to find one thing:
The Big Dipper! The most easily identifiable object in the Northern Skies, if all you can do is find this guy, here’s how you — given good, dark skies — can find a whole slew of beautiful objects! Now, before we get going, you need to know that the more light pollution you have — i.e., the lower your elevation, the closer you are to cities, and the fuller the Moon is — the less able you’ll be to see faint and diffuse objects. Let’s get on with it!
You’ll need to get your bearings, and that means finding true North. In the Northern Hemisphere, we are guided by the North Star, which is easy to find if you know your Big Dipper! Simply take the last two stars in the “cup” portion of the dipper and follow them up and out of the cup; they’ll run into Polaris, the bright pole star and the edge of the handle in the Little Dipper!
Here in April, the Big Dipper stars out high in the sky after Sunset, making it the ideal guidepost for your night-sky hunting. The dipper itself is made up of seven stars… or is it?
Just barely visible to the naked eye is the fact that the second star in the handle of the Big Dipper is actually a double star. But if you point your telescope at it, know what you’ll find?
It’s actually four stars! Mizar is a binary star system, where both stars appear very bright, and there is a faint star behind and between Alcor and Mizar, visible only through (good) binoculars or a telescope.
But the Big Dipper can not only lead you to Polaris, it can lead you to a couple of the brightest and most spectacular stars in the Northern Hemisphere. Let’s start with #1!
If you follow the curve of the handle through space for a little while, you’ll come to Arcturus (make an “arc to Arcturus”), the orange giant that is the brightest star in the Northern Hemisphere! Unfortunately for you telescope enthusiasts, there’s nothing remarkable about it through a telescope.
But instead of following the handle, try following the two stars that make up the top of the Dipper’s cup.
They take you, going away from the Dipper’s handle, to Capella, the third brightest star in the Northern Hemisphere (and sixth overall)! Capella is notable for being the brightest star that’s also close to the North Pole (and hence is the most seen bright star in the Northern Skies year-round), but through a telescope, Capella is something special.
Capella is actually a double yellow giant! Two yellow giant stars, in close orbit around one another, that never eclipse one another! (In other words, any time you look at them, you’ll always be able to see two distinct, non-overlapping stars.)
But if you get a really good telescope, you won’t just see the two yellow giants…
You’ll see that Capella is a pair of binaries! The two yellow giants and two red dwarf stars.
Not bad for stars, simply by being able to find the Big Dipper. What if you wanted to go beyond stars, and find a beautiful planetary nebula?
Guess what? There’s one in the Big Dipper! In the 18th Century, Charles Messier made the first catalogue of “non-cometary” objects in our night skies. Only four of them were planetary nebulae, or stellar corpses of red giants that have blown off their outer layers. One of them — the Owl Nebula, or M97 — is right there, just below the bottom of the “cup” of the Dipper!
The two dark “eyes” give it its name, although perhaps today it would be called the Amy Winehouse nebula? While it’s one of the fainter nebulae in the sky, its compactness means it’s going to be visible even with substantial light pollution through a reasonably-sized telescope. Originally around the mass of our Sun, the Owl Nebula is only about 6,000 years old, with about 15% of the Sun’s mass making up the glowing, “nebular” region.
But what if you’re dissatisfied with stars or nebulae? What if you want to find some galaxies? Luckily for you, the Big Dipper can help you find three of the most spectacular ones. Let’s start with the easiest.
Go directly “below” the last star in the handle, perpendicular to the line it makes with the Alcor/Mizar double star next to it. That’s the location of the Whirlpool Galaxy, M51, one of the most spectacular (and one of the brighter) face-on spirals in our sky!
If you had a really good telescope, you might see something like this…
Of course, you likely don’t have Hubble, but with good skies, you can see the companion galaxy, NGC 5195, even with large binoculars or a small telescope! Those pink regions in M51 are real, not false color, and are emission lines from star-forming regions.
Want a challenge? Try to find one of the faintest face-on spiral galaxies near the Big Dipper:
M101! Start at Mizar/Alcor, and follow the line that Mizar makes with Alcor. That should take you to a fairly bright star, labeled “81” above. Bend “down” (back towards the Dipper’s handle) and follow the rough “line” of brighter stars until you’ve hit four in a row, and then head back “up” (away from the Dipper’s handle) one last time; that fuzzy blob is M101, the Pinwheel galaxy!
Only visible in places with low light pollution, M101 is a challenge for amateur observers. But for Hubble…
I certainly don’t expect to see this, polluted by bright city skies (and a nearly full Moon tomorrow night), but it is certainly worth a try!
But there is one more candidate that I would like to try for, the great galaxy pair, M81 and M82. How to get there?
Take the last star in the “cup” of the Big Dipper (the last of the pointer stars that points towards the North Star) and the one diagonally down from it. (Dubhe and Phecda, respectively.) Connect Phecda to Dubhe, and continue on in an imaginary line for the same distance, and that should plunk you down very close to a pair of bright, interacting galaxies, M81 and M82!
With dark skies and a good telescope, these are spectacular. With city skies and a moderately-sized scope, they may be visible at all… we’ll see.
And those are some amazing sights available to you, even if all you have is a simple telescope, and even if all you know is the Big Dipper! And for those of you who are way ahead of me, tomorrow night, what objects do you recommend viewing with a 16″ scope under heavy light pollution? I know that Saturn is up…