This month marks the tenth anniversary of one of the best ideas to come out of modern astronomy: the Hubble Heritage project. Astronomers at the Space Telescope Science Institute knew that Hubble was taking fantastic images that the public weren’t seeing, because Hubble was taking them faster than they could release to the press. So they decided that on the first Thursday of each month they would release a gorgeous picture online.
For their tenth anniversary*, they present this beautiful image of detail in the nebula NGC 3324:
Cooool. But what is it?
It’s a cavity several light years across, carved out by the fierce light and intense stellar winds from a group of young, massive, hot stars that are out of the frame ("up", if you will). This whole part of the sky, in the direction of Carina, is lousy with dust and gas. There are star-forming regions all over the place. Stars of all masses are born, from dinky brown dwarfs with less than 1/10th the Sun’s mass, up to bruising monsters 80 times the mass of the Sun. The massive stars are incredibly hot, and blow off a dense and fast wind of material which pushes against their nursery cocoon.
The result is a sharp-edged bubble of material. Inside is thin hot gas (colored blue in this image), and outside is thicker dust and gas (reds and browns). See the little pseudopods sticking in around the edges? Those are formed where you get denser blobs just inside the cavity edge. Note that the winds and light are streaming "down" in this image. When that flows past the blobs you get those finger-like sandbars. When you zoom in on them, they look a lot like the trunks in the Pillars of Creation Hubble image or the Spitzer image of nebula W5. If you look carefully in that zoom above, you can see lots of these features scattered around the cavity’s edge.
Zooming out is useful, too. In the picture to the right you can see the overall bubble shape to the nebula, and the stars near the center that are sculpting this vast cavern. The Hubble image is of the section to the upper right of the cavity, from about 1:00 to 3:00 if the circle were a clock face. But you can see amazing features all around the edges.
Hubble is having its woes right now, and even if it gets fixed its own clock is ticking. It was launched in April 1990 — I still remember it well, as I had just signed up to use it for my PhD project — and nothing lasts forever. But Hubble has taken thousands upon thousands of observations, all of which have been stored away. And while Hubble may eventually be shut off, the images, spectra, and other data it’s taken will live on. Astronomers a century from now will be digging through the archives, looking for an elusive supernova, a feature of a nebula that’s changed in the intervening years, the positions of stars in globular clusters, and the colors of galaxies so far away that when the light Hubble detected left them, the Earth was still a cooling ball of molten rock.
Diamond anniversaries come and go, but the treasures Hubble has unveiled will still be around a long, long time. Congratulations to my friends at the Hubble Heritage Project. Thanks for bringing us these jewels in the sky.