In celebration of the start of the Atacama Large Millimeter/submillimeter Array's (ALMA) Early Science observations, the National Radio Astronomy Observatory (NRAO) has released an image of a merging pair of galaxies as seen by the growing ALMA telescope. The detailed views of star-formation in the Antennae Galaxies confirm that this new telescope, while far from completed, and with only a fraction of its ultimate imaging capability, will surpass all others of its kind.
About six hundred million years ago, this peculiar object was two separate, beautiful spiral galaxies passing by each other for the first time. Now, it captivates astronomers as the youngest and nearest colliding galaxy pair ever found.
Spiral galaxies are a spectacular example of gravity's beautiful geometries, stunning structures created when swirling gas and dust are drawn together. In a spiral galaxy's center, a central massive black hole hoards a giant glowing bulge of gas and stars for itself, while out in the spinning disk, rippling compression waves trigger stars to form along its dusty, gas-rich arms. In isolation, a spiral galaxy would make stars like this until its gas was too thinly spread to fuel any new ones.
In contrast, colliding galaxies like the Antennae are an equally spectacular example of gravity's jumbled catastrophes. If two spirals form too near each other, their centers will slowly tug each other closer, and the gas and stars from their outer disks will lag behind, eventually trailing off into tails. As the central denser parts of the galaxies slowly collide over millions of years, their gas and dust clouds often compress together, eventually producing clumps of new stars.