What happens when you take a camera that was designed to see things as far as 8 billion light-years away and point it at an object that’s a mere 51 million miles away? You get this amazing picture of comet Lovejoy.
The stunning image below is a composite of 62 pictures taken with the Dark Energy Camera, known to its astronomer friends as DECam. The 570-megapixel camera sits nearly 1.5 miles up in the Andes Mountains, at Cerro Tololo Inter-American Observatory. From its lofty perch, it is scanning the night skies to help solve one of the biggest mysteries in science: As the universe expands, why is it speeding up instead of being slowed down by gravity?
To answer that question, DECam is surveying as much of the universe’s 14-billion-year history as it possibly can. Seeing further into the past means seeing across mind-boggling distances. This camera, built at the Fermi National Accelerator Laboratory in Batavia, Ill., was specially designed for the task.
It has 74 chips that capture even faint hints of light and converts them into electrons that are combined into an image by a computer. Each of the chips can produce millions of pixels. For added sensitivity, the chips were built to detect stretched-out wavelengths of light that have become red-shifted along their travels from distant stars to us. The camera is cooled to nearly 150 degrees below 0 Fahrenheit and kept at extremely low vacuum pressure to help it see as much as possible.
Comet Lovejoy happened to fly in front of all this optical firepower on Dec. 27, 2014, as DECam was gathering data for the Dark Energy Survey. At the time, Earth was almost twice as close to the comet as it was to the sun. (The comet's closest approach to Earth came on Jan. 7, when it got within 43.6 million miles of our planet, according to measurements posted by NASA’s Jet Propulsion Laboratory.)
The icy nucleus of comet Lovejoy is about 3 miles wide, and it’s surrounded by a cloud of gas and dust that stretches 400,000 miles from end to end. In the picture, Lovejoy’s tail flares behind and extends out of view.
The comet — the fifth to be discovered by amateur astronomer Terry Lovejoy of Australia — really is as green as DECam makes it out to be. That’s because of the diatomic carbon — or C2 — that emanates from its nucleus. This gas glows green as it meets ultraviolet light from the sun in the near-vacuum of space.
Photo: The comet Lovejoy, created from a composite of 62 pictures taken with the Dark Energy Camera. Credit: Marty Murphy, Nikolay Kuropatkin, Huan Lin and Brian Yanny / Fermi National Accelerator LaboratoryCopyright © 2017, Los Angeles Times