After a decade of painstaking engineering and construction, the Atacama Large Millimeter/submillimeter Array (ALMA) is now open for business. ALMA is a collection of (currently) 19 telescopes, each 12 meters across, that can detect light that is between the radio and infrared parts of the spectrum. All sorts of interesting objects emit this kind of light, including solar systems in the process of forming, very distant galaxies nearly at the very edge of the visible Universe, and warm gas and dust from star birth. In fact, ALMA released an image of that latter type of thing, and it’s pretty nifty: That’s a close up of the Antennae Galaxies, one of my favorite objects in the whole sky. This is what used to be two separate spiral galaxies like our Milky Way. A few hundred million years ago they collided, and are still in the process of merging. As they do so, vast clouds of gas slam into each other, collapse, and form stars. We get a pretty good view using visible light, but ALMA can penetrate the thick dust and see what’s going on inside those clouds, and does so in detail and resolution we literally could not get in the past. In that image, blue is visible light from Hubble, and orange and yellow is from ALMA, showing where stars are currently being born. Observations like this allow astronomers to get more information from these complex sites of star formation. We understand quite a bit about how stars are born, but the details are incredibly difficult to disentangle because so many processes are going on. When we look at objects at different wavelengths we see different physics going on (for example, ultraviolet light can come from very hot stars, while submillimeter light is generated by warm dust), so, when coupled with high-resolution Hubble images like this one inset here, these different physical processes can be teased apart. And this view will only get better. Right now, 19 dishes are in operation for ALMA, but that will increase to 66 by 2013, spread out over the 5000-meter-high (16,500 foot) plains in northern Chile. When completed it will be able to see even deeper and with more resolution. I think I’m most excited about the prospect of observing young planetary systems. I did some work on those back in my Hubble days, and it’s amazing how much progress has been made in this very young field of astronomy. ALMA will see these systems in the millimeter regime more clearly than any telescope before, and no doubt will be a boon to scientists trying to figure out just how swirling disks of gas and dust turn into planets like Earth. My congratulations to all my friends at the National Radio Astronomy Observatory and to everyone involved in this project! It’s always great news when we get new eyes on the sky. Image credits: (NRAO/AUI/NSF), ALMA (ESO/NAOJ/NRAO), HST (NASA, ESA, and B. Whitmore (STScI)); Davide de Martin, NASA; W. Garnier, ALMA (ESO/NAOJ/NRAO)
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