Some 8,000 years ago, back in the Neolithic, photons from this gossamer cloud started traveling toward Earth. It would be another 8,000 years before they tunneled into the eyepiece of William Herschel for the first time. A few hundred years later, they landed on the mirror of the Hubble Space Telescope, whose instruments stitched together the gorgeous image you see above.
This cosmic soap bubble—named, appropriately, the Bubble Nebula—is the result of a raging stellar wind streaming from the bright purplish star at center-left. That giant star, called SAO 20575, is between 10 and 20 times the mass of the Sun and its wind whistles outward in all directions, at 620,000 miles per hour, meaning the bubble is expanding fast.
The sun does a similar thing, enveloping the solar system in a bubble called the heliosphere. We all live in that bubble, although it is much smaller than this one, which stretches 10 light years across.
The Bubble Nebula sits inside a vast molecular cloud, one of the largest structures in a galaxy. Molecular clouds are full of cool dust and gas that eventually condense and collapse to form baby stars. Gas pressure from this cloud might explain why the star is blowing a perfectly round bubble around itself, even though is not at the bubble’s center.
Astronomers snapped this image as part of Hubble’s annual April birthday celebration. Each year, the team that runs the telescope dedicates time to an astronomical object chosen because it is especially awesome.
The whole nebula is too large on the sky for Hubble to see at one time, so previous pictures have only shown a slice. This image is a mosaic of shots from the telescope’s new Wide Field Camera 3, which spacewalking astronauts installed in May 2009.
Hubble was launched up 26 years ago this week, and shortly thereafter became a national embarrassment. Its main mirror, literally the most important piece of any telescope, was flawed. A tiny error about 1/50th the thickness of a sheet of paper caused light to bounce around incorrectly, resulting in blurry images. Three and a half years later, astronauts on the space shuttle were able to retrieve the telescope and swap out its main instruments, installing a set of corrective optics. The world saw Hubble’s first corrected image in January, 1994, and it was everything astronomers had hoped. More than two decades later, the telescope is still in its prime.