NASA unveils atlas of infrared photos of the sky

NASA unveiled an unusual atlas and catalog of infrared images of the entire sky on Wednesday that includes more than 500 million stars, galaxies and other objects that have been captured by the Wide-field Infrared Survey Explorer, or WISE, spacecraft. “Today, WISE delivers the fruit of 14 years of effort to the astronomical community,” said Edward Wright, WISE principal investigator at UCLA, who first began working on the mission with other team members in 1998, in a Wednesday news release. The WISE spacecraft was launched in December 2009, and spent all of 2010 mapping space surrounding Earth. The mission collected more than 2.7 million images recorded at four infrared wavelengths of light. Those images recorded everything from asteroids moving near this planet to distant galaxies. A first release of WISE data, covering half the sky, occurred last April. Individual exposures have been combined to create an atlas of more than 18,000 images, and a catalog listing the infrared properties of more than 560 million individual objects. Most are stars and galaxies, many of which had never been viewed before. The WISE mission is credited with discovering the coolest class of stars, failed orbs called “Y-dwarfs” that don’t shine in visible light, and thus were only visible using infrared sensors. WISE astronomers also surveyed near-Earth asteroids, finding fewer mid-size objects than previously thought, and cataloging more than 90 percent of the largest near-Earth asteroids. One of those was the first known “Trojan” asteroid, which shares the same orbit around the Sun as Earth. Another image shows an “echo” of infrared light emanating from an exploded star, created in the clouds of gas and dust when the flash of light from the supernova explosion headed surrounding clouds. The mission already has resulted in the publication of 100 scientific papers, and more discoveries will follow, as researchers continue to study the atlas’s images. “It will be exciting and rewarding to see the innovative ways the science and educational communities will use WISE in their studies now that they have the data at their fingertips,” said Roc Cutri, who leads the WISE data processing and archiving effort at the Infrared and Processing Analysis Center at the California Institute of Technology in Pasadena. The mosaic of images at the top of this article shows in two dimensions the area of the sky that was mapped. The technicians creating the mosaic used a projection technique called an “equirectangular,” often used by planetariums. In the image, the Milky Way Galaxy is a horizontal band across its center. The Milky Way is shaped like a disc, and our solar system is about two-thirds of the way out from the center. Towards the center, there’s a noticeable increase in stars, colored blue-green, as the view is through more of the disc than when looking at angles away from the center. Bright red spots at the 1 o’clock, 2 o’clock and 7 o’clock positins in the image are the planets Saturn, Jupiter and Mars, respectively. Rectangular-shaped features at several locations in the image are the result of the difficulty of matching backgrounds of individual atlas frames. Colors in the image represent the wavelengths of infrared light. Cyan, or blue-green, shows light emitted mostly from stars and galaxies, at a wavelength of 3.4 microns. Green and red represent light largely emitted from dist at 12 and 22 microns, respectively. The second image records the death of a supergiant star within our galaxy that occurred more than 11,000 years ago. As the star’s core collapsed, it formed an ultradense ball of neutrons, while the outer part of the gaseous orb was blasted away in a supernova. The light from the explosion first reached Earth from the direction of the constellation Cassiopeia in 1667, but there’s no record of anyone seeing it then. Dust between the dying star and Earth is thought to have dimmed the brightness of the explosion, making it barely visible to the unaided eye. The supernova was discovered in 1947 when scientists first monitored its powerful radio emission, and dubbed it Cassiopeia A. In the image, the central bright cloud of dust is the blast wave moving through interstellar space, heating up dust as it travels. The blast wave moves at an average speed of 11,000 miles per second, but that’s only about 6 percent of the speed of light. The blast material has moved about 21 light-years – the distance light travels in a year, at 186,000 miles per second – from the initial explosion, though that explosion’s first flash of light moved much faster. The orange colors indicate dist heated as the supernova flash reached it centuries after the original explosion. The third image combines data from four different space telescopes, including WISE, to illustrate the oldest documented example of a supernova, called RCW 86. This star explosion was first witnessed by Chinese astronomers in the year 185 A.D., who recorded a temporary star in the sky that could be viewed for 8 months. This image combines X-ray images from the European Space Agency’s XMM-Newton Observatory and NASA’s Chandra X-ray Observatory to form the blue and green colors. The X-rays record interstellar gas that has been heated to millions of degrees by the passage of the shock wave from the star explosion. Infrared data from NASA’s Spitzer Space Telescope and WISE are shown in yellow and red, revealing dust radiating at a temperature of several hundred degrees below zero. That’s still warm, compared to normal dust in the Milky Way.