Sunday, March 13, 2011

Star Stuff

I recently began an internship at a small publishing outfit in New York because my professional life is going nowhere and I reckoned it would be at least a few cents cheaper than a semester of graduate school. Two mornings a week I hop a train to Manhattan, take the subway to Brooklyn, then walk ten minutes to the gallery building where the office is situated. On the two evenings that correspond to these two mornings, I exit the building and walk ten minutes, take the subway to Manhattan, and hop a train back to Jersey.

During my commute last week I was kicking around ideas for a new blog post, since the last two were such cop-outs -- one was an excerpt from someone else's novel, and one was an excerpt from my novel.* Turning to observations made on the four train rides I make during a day at the internship for material, I was all set to to squeeze some more out water of the "ways in which technology is making our lives worse instead of better" stone, but then I entered the subway after leaving the gallery and realized I still had the office keys in my pocket.

Up the escalator, through the turnstile, back to the street. Ten minute walk to the office to return the keys to the boss. By now it was nearly 7:00 PM and the urban twilight settled in. As I headed south, uphill along Washington Street, I spotted a bright yellowish star almost directly ahead.

Jupiter? I scanned its surroundings. No -- not Jupiter. Not with Orion at two o' clock. This would have to be Sirius. There was Jupiter -- above Manhattan in the west, blinking behind the arches of the Brooklyn Bridge.

Then I thought fuck it -- this week I'm just gonna write about stars.

Tonight we'll go over a small stretch of the winter sky that should be visible just after dark around this time of year (provided your latitude is in the same ballpark as Manhattan). Since the stars "revolve" along a curve, assume that we're looking at the stars around 7:00 pm (8:00 for daylight savings) in early March when I cite an o'clock as a direction from one star to the next.

Let's begin in the south, as I did the other night. All you need to do is face the direction in which the sun set and turn about 90 degrees counter-clockwise. Search the sky for a bright star. It won't be hard to find; it isn't that high up, and you'll probably know it when you see it. This would be the dog star, Sirius (α CMa): the second-brightest star in the sky (outshone only by the sun) and the centerpiece of the constellation Canis Major.

Believe it or not, Sirius is actually a binary star, composed of two individual stars (Sirius A and Sirius B) orbiting each other. Sirius A is the really massive and bright one, while Sirius B is an unassuming white dwarf, formerly a red giant and the larger of the two. Squint as hard as you like; unless you've got a real nice telescope and a great vantage point, you'll never resolve the two separately.
Moving along: at about two o' clock from Sirius stalks Orion, the hunter of the winter sky:

The three stars forming his belt (center) are nearly impossible to miss. From left to right, they're often listed by science types as ζ (Zeta) Ori, ε (Epsilon) Ori, and δ (Delta) Ori. The Greek letters come from the Bayer Designation, a system devised by astronomer Johann Bayer to catalog stars by constellation and brightness.

Fun fact: though the stars of Orion's Belt appear to be arranged in a neat row, this is only a trick of our terrestrial perspective. According to stellar parallax measurements collected by the Hipparcos satellite during the early 1990s, the distance between each star and the earth varies more than you might suspect:

Earth to ζ Ori: 800 light years (approx)
Earth to ε Ori: 1300 light years (approx)
Earth to δ Ori: 900 light years (approx)

The "belt," then, is actually a group of distant, unrelated stars arranged in a zigzag. Only because of our particular vantage point do we perceive them as sitting in a line.

At any rate, Orion is very recognizable, easy to find (even in areas with a lot of light pollution), and full of neat stuff. We'll begin at the hunter's left shoulder with the red supergiant Betelgeuse (α Ori).

Betelgeuse is another hard star to miss, thanks to its brightness and distinct hue: simply lift your gaze straight up from the belt's leftmost and middle stars and look for the orange-red star. Again, you'll know it when you see it.

Many astronomy books and educational materials like using Betelgeuse to demonstrate the relative sizes of stellar bodies, and I intend to follow suit -- but first, let's play with shapes.

If you think back to our November adventure and observation of the Andromeda Galaxy, you might recall a method of calculating distances using simple geometry. The same trick can also be used to get an idea of a distant object's size as well -- provided you already know its distance.

To begin, here's the Earth.

Now we draw a circle around the Earth. This represents the celestial sphere -- an imaginary construct representing how we perceive the heavens. Think of it as a huge hollow ball with stars painted on the interior. The Earth floats in the center, remaining still while the sphere rotates around it.

Since every star occupies a small but measurable width on this spherical plane, it is possible to quantify their perceived sizes as angular measurements. Betelgeuse probably isn't the best example we could be using, since observations of its angular size tend to vary (for a number of reasons). But if we just use the median of some measurements given by an uncited Wikipedia article (0.0545 arc seconds) and convert it to degrees using the Calculator application in my System Tools folder, we might hope to guess that of the 360 degrees in the sky, the red supergiant Betelgeuse occupies some 0.00001513 degrees (or so). Phew!

Now we draw a second circle around the first and mark off a section proportional to Betelgeuse's angular size on the first circle. This represents the star's actual width.

Astronomical voodoo places Betelgeuse's distance at something like 643 ± 146 light years from Earth. (This number was also pinched from Wikipedia, but at least we got a source.) For the sake of convenience, let's just use 643 light years (6,083,119,760,000,000 km) as our distance. Can you guess the equation yet?

(Betelgeuse's angular size) degrees / 360 degrees = (Betelgeuse's actual width) km / 2π(distance) km
0.00001513 degrees / 360 degrees = X km / 2π(6,083,119,760,000,000) km

Please feel free to add up the numbers yourself and let me know if I made a mistake (which isn't unlikely), but the value I got for X was something like 1,606,359,190.

By this measurement, we get a rough estimate of 1,606,000,000 kilometers for Betelgeuse's width. That's about 998,000,000 miles.

Betelgeuse is a seething, belching nuclear orb with a (very loosely) approximate diameter of 998,000,000 miles. Just for comparison's sake, the sun's diameter is only a measly 870,000 miles, and the diameter of Earth -- the planet on which you and I and six billion other humans live -- comes to an infinitesimal 7,926 miles.

Think about that for a moment, please.

Anyhow, we see variations in measurements of Betelgeuse's apparent size because of the star's instability. Its actual size fluctuates; the stuff it spits out into space make it hard to tell where the "exhaust" ends and the star begins. But astronomers are pretty certain that Betelgeuse is shrinking. If anything we've guessed about stellar life cycles is accurate, this means Betelgeuse is fixing to go supernova. (I don't think there's any proper terrestrial analogy for an event like this. Comparing it to the detonation of a billion mile-wide thermonuclear device probably doesn't even come close to the reality of it.)

We don't know when this is going to happen. It could be next year (though probably not). It could be a million years from now. But when information of the event reaches Earth, it will be very difficult for us (or whatever species survives us) not to notice. The last recorded supernova (1054 A.D.) is reported to have been visible during the day and brighter than the moon at night. More on this later.

Now! Let's move on from Betelgeuse at last and return to Orion's Belt. Hanging below the leftmost star of the belt (and its cute little neighbor) is the "scabbard." My city-dwelling friends might be out of luck where this is concerned -- maybe it was because the sun still hadn't completely set, but I couldn't make out any other stars between Orion's belt and Rigel in the Brooklyn sky.

Quick Rigel Fun Fact #1: Its Bayer Designation pegs it as β Ori, even though it's very perceptibly brighter than α Ori (Betelgeuse).

Quick Rigel Fun Fact #2: Kang and Kodos from The Simpsons claim to originate from the (fictional) fourth planet orbiting Rigel.

Anyway, on to the scabbard. What we're looking for now -- depending on the clarity of the skies -- is either the first or the second star from the top. (If conditions are good, you'll see three stars in the scabbard. Often, you'll only spot two.) Even without a telescope, if you look closely you can discern that it's not a tiny point, like most stars -- it actually looks more like a luminous smear. This is because what you're looking at isn't a star, but a cloud. This would be Messier Object 42, better known as the Orion Nebula.

All you require is a halfway-decent pair of binoculars and a clear evening to get a nice glimpse of it. What you see probably won't look quite as impressive as the above Hubble image, but it's a beautiful sight nonetheless.

Moving on at last from Orion! If we look at Betelgeuse and direct our gaze about two o' clock or so (or one o' clock from the rightmost star in the belt), we stumble into the constellation Taurus. What we're looking for is α Tau -- the orange giant Aldebaran (Arabic for "the follower"), sometimes colloquially referred to as the red eye of the bull.

Here's another stargazing opportunity in which my city-dwelling friends sadly get shortstrawed. If you've got either a very clear night or a pair of binoculars, direct your gaze to about four o' clock of Aldebaran and behold the Hyades star cluster.

From where I live, they're barely visible with the naked eye. With a pair of hand-me-down birdwatching binoculars, I can spot nearly a dozen of them. They're quite a sight -- like little gems sown across the firmament -- but the Hyades are a bit like the Jan Brady of star clusters: everyone pays more attention to their more noticeable and prettier sister(s), whom we'll get to in a sec.
If you look at Aldebaran and move to about ten o' clock, you bump into ζ Tau, the tip of the bull's lower horn. This star doesn't shine as brightly as the other ones we've looked at and can be difficult to find. It often helps to use both Betelgeuse and Aldebaran as signposts:

Right in Zeta Tau's vicinity sits Messier Object 1: the famous Crab Nebula.

Remember that 1054 A.D. supernova I mentioned earlier? This is the remnants -- a visible, tangible echo of the big KABOOM. To save you the trouble of looking it up and converting the units, the Crab Nebula's radius is somewhere in the neighborhood of 32,000,000,000,000 miles, and it seems to be expanding at about 900 miles a second -- which means, in a sense, that the explosion from 1054 A.D. is still happening.

I'll wait a moment while you try to wrap your head around that. Lord knows I can't.

The star wasn't quite massive enough to collapse into a black hole after the supernova, but somewhere in its billowing corpse spins a pulsar. I won't even pretend to know enough about neutron stars and pulsars to provide any facts, so I will direct you elsewhere for that. (The universe is full of very wonderful and frankly terrifying things.)

It is possible to glimpse the Crab Nebula from Earth, provided you have sufficiently clear skies and sufficiently powerful optics. Apparently I have neither, because I CAN'T FIND THE DAMN THING. (I can't quite pin down the location of the constellation Cancer, either. Strange that interstellar crustaceans should prove such elusive critters.)

To conclude our brief cosmic stroll and to wrap up this not-so-brief blog post, look at Aldebaran again and direct your gaze one or two o' clock or so. What you'll see is a star cluster that more than one inexperienced and clueless stargazer (including myself) has mistakenly assumed was the little dipper because of its shape. This is one of the most famous and renowned sights of the night sky: it so evoked the imagination of Arabic astronomers that they named a prominent orange star "the follower" because of how it appears to wander after it across the celestial sphere. You're looking Messier Object 45, the seven (well, six) sisters -- the Pleiades.

The Pleiades don't appear quite so bright (or blue) with the naked eye, though I have yet to view them through a good telescope. Even without any optical enhancements, they appear a lovely little jeweled tadpole in the winter night. If any of my New York-dwelling friends or readers are reading this, please look for them when you have a chance. I couldn't spot them during my walk to the subway the other night, though it very well could have been that my vision was obstructed by buildings. Let me know: does the tadpole wriggle in Manhattan's skies?

Yeesh. When I start waxing pseudo-poetic like that, it means I've spent too much time typing and not enough time sleeping. I hope this has been entertaining and informative for you, and I doubly hope it encourages you to spend a bit more time exploring the skies in the nights to come. (And I triply hope I've managed to trick you into thinking I have any idea what I'm talking about.) Stargazing can be an addictive hobby -- soon as you learn to "read" part of the cosmic tapestry, you find yourself more curious and eager to decipher more of it. (Also, strong circumstantial evidence suggests that pointing out stars and constellations when you're on a date doubles your chances of getting laid.)

Remember, these are all winter stars -- in another month or so, they'll be out of sight. Find them while you have the chance!

* Yeah, about that novel: in an epiphany, I realized that the only way I can possibly make it work is by rewriting 80% of it. I'm thrilled to have discovered a way out of the impasse, but at the same time...


  1. I haven't read this post yet (I promise to in the near future!), but did you know that if you become sleep deprived and are procrastinating and skim the article, the picture above the paragraph "All you require is a halfway-decent pair of binoculars..." looks like a cosmic image of an anthropomorphic figure shooting a cone of energy at an upside-down fetus...or a lizard?

  2. What a coincidence, I remember you implying you loved astronomy and I sent you a link about it in that email

    Also, did you get that email?

  3. Neat stuff. The Mars and Orion pictures are nnnuuuutttsss. I wish I could afford a super-fancy telescope.

  4. The photos are incredible and I could listen to you for hours. Can I come over?

    1. I wish I could take credit for the photos, but yes. Yes you can come over.