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I had an onslaught of relatives over the long holiday weekend (here in the U.S. we celebrate Presidents’ birthdays on the third Tuesday in February). My nephew brought his telescope along, and we did a little stargazing outside for as long as we could stand the cold weather. He’s starting to learn the constellations and a few of the brighter stars. Not that he needed the telescope to show us those things, but I think he wanted to show off his new acquisition.
Their visit was a nice break from show production. We’re working on a series of shows about stargazing and how easy it is, and we needed a bit of a break.

Stargazing is one of those things that I used to think everybody knew how to do. That was before I did lectures in the planetarium, back in grad school. Then I found out that people really don’t know much about the sky, other than “the sun sets in the west” kind of information. It’s kind of a shame that this knowledge isn’t really prized as much as it used to be, because the sky is up there, free for the gazing. Even through all the glow of light pollution, if you live in the city. I noticed when I was living and working in New York City, I was still able to make out a fair number of bright stars and planets each night (when it was clear).

I like winter stargazing because (for me, anyway) it brings Orion, the Hunter to my attention. My favorite constellation. It’s got it all: bright stars, a starbirth nebula, and an easily recognizable pattern.

A false-color view of the Orion Nebula from the Spitzer Space Telescope.

So, go out tonight and check it out. If you have a pair of binoculars or a small telescope, find the line of three stars (the “Belt” of Orion) and then look just below the belt. You’ll spot a fuzzy patch of light; that’s the Orion Nebula. It lies about 1,500 light-years away and is the nearest star-forming region to us. Here’s a false-color view of the nebula, as seen by the Spitzer Space Telescope in several wavelengths of infrared light.

Since it’s snowing like mad and the wind is blowing like a banshee here (and the temperature is a toasty 21 degrees Fahrenheit) right now, I want to talk about hot stars. Specifically, let’s talk about hot, dying stars that were once like the Sun. Here’s NGC 2440 to help me take my mind off the cold weather! (For you folks in sunnier climes, count your blessings!)

So, NGC 2440 first came to my attention back when I was working on my first book with Jack Brandt, called Hubble Vision. We wanted to show a nice array of stars at different stages in their lives. Star lives, by the way, are way longer than ours, but like us, they proceed in stages. There’s the infancy part—that takes place in a cocoon of gas and dust. Then, there’s the “living” part, where the star consumes nuclear fuel in its core for some amount of time. Then, there’s the old age part, where the star starts to lose mass in huge quantities and finally gives up the ghost. If the star is massive (like more than 8 or 10 times the mass of the Sun), then it sheds lots of its atmosphere before blowing itself to smithereens in a supernova explosion.

If the star is like the Sun, then it litters its environment with material that it blows away from itself. It does it maybe once, or maybe several times, creating shells of gas (nitrogen, hydrogen, oxygen, and helium, for example). That “exhaled” matter forms a shell around the star. Then, the interior star contracts (shrinks), and in the process, heats up.

So, NGC 2440 (what’s left of it) is very hot—like 400,000 degrees Fahrenheit (try more than 400,000 times hotter than your oven gets). All that heat has to go somewhere and do something, so it’s lighting up the huge cloud of mass that the star lost earlier in its life.

There was more than one outburst from NGC 2440 during its old age, which is why we see two “lobes” of material surrounding the central star.

If you want to see a huge version of the image above, go here (the HST news center). The highest-resolution image almost looks three-dimensional.

Now, I feel a bit warmer. How about you?

The Spacewriter's Ramblings

Warming Your Hands at The Fire of a Dying Star

Exploring Science and the Cosmos