WISE
Go outside tonight after the sun has long set. Find a place where there are no streetlights and you haven’t a flashlight or match. Choose a night when the moon is not up and its cloudy. Now, toss your car keys a few yards in front of you and try to find them. While you’re at it, attempt to make sense of the gloomy shapes around you: the bushes and trees, the rocks, any nearby or distant buildings, and that mugger waiting to attack you. Can you trace out the shape the mountains on the horizon?
Probably you’ll have trouble locating your keys or discerning any details about the landscape around you. Good luck identifying that mugger in the police lineup.
But now pull out your night vision goggles—surely you have a pair on you, right? Thanks to their ability to let you see the infrared wavelengths of light that are invisible to your naked eyes, the world will suddenly become bright and clear. You’ll find your keys and running away from the mugger will be a snap.
On Monday, December 14, 2009 a space probe was launched from Vandenberg Air Force Base on the coast of California that was designed to do much the same thing for our view of the universe as those night vision goggles would do for you in a scary back alley. The Wide-field Infrared Survey Explorer, also called WISE, is a telescope with a sixteen inch diameter mirror designed to survey the entire sky in the infrared-wavelengths of light. It was launched from Vandenberg rather than Cape Canaveral in Florida because it was placed in a polar orbit—so that it circles the Earth north and south instead of east to west like most satellites. It operated until it ran out of hydrogen coolent in 2011.
WISE took a total of 1.5 million photographs—about one every eleven seconds of its ten month mission. It was many times more sensitive than previous infrared satellite telescopes. The Infrared Astronomical Satellite (IRAS) and the Cosmic Background Explorer (COBE) both conducted full sky surveys back in the 1980s. IRAS used just 62 pixels to cover four infrared bands, while COBE had but a single pixel per band. In contrast, WISE covered a million pixels per band. The difference between the previous orbiting infrared observatories and WISE was like the difference between a poorly photocopied impressionist painting of a forest and what you see on your high definition TV when you watch a Blu-ray disc of a forest.
The images that WISE took contained data on the local solar system, our galaxy, and the universe as a whole. The discoveries from this mission were unprecedented. Scientists discovered thousands of new asteroids and comets, including many of the kind that swing close to Earth called NEOs (Near Earth Objects). Given that asteroids have struck our planet with devastating results–most recently the close call in Russia–finding them beforehand is valuable. In June 30, 1908 a small asteroid estimated at only around 300 feet across exploded in the air about 5 miles above the surface of Siberia, near the Tunguska River. Estimates of the energy released by the explosion range from 5 to 30 megatons—at least 1000 times more powerful than the atomic bomb that destroyed Hiroshima in 1945. The Tunguska blast devastated an area of 830 square miles, flattening 80 million trees. Had the asteroid exploded over a city like Los Angeles, the death toll would have been in the millions.
WISE is found many new brown dwarfs—balls of gas more massive than Jupiter but too small to have become true stars. Astronomers also discovered a lot of new, dim stars called red dwarfs. They believe that it is entirely possible we’ll discover one or more that are closer to our solar system than the currently known closest star, Proxima Centauri, which is about four light years from us. Thus far in analyzing the data, scientists have discovered one previously unknown Red Dwarf only about 10 light years from Earth, currently designated WISE 1049-5319. WISE was not able to detect Kuiper belt objects, since their temperature is too low. It was only able to detect objects warmer than 70–100 Kelvins. A Neptune-sized object would therefore have been detectable out to 700 AU, a Jupiter-mass object out to one light year (63,000 AU). A larger object of 2–3 Jupiter masses was visible to WISE at a distance of up to seven to ten light years.
WISE was also capable of imaging any ultraluminous infrared galaxies that are out there, up to ten billion light years away.
All the WISE data has been publicly released, but the analysis of the mountains of data it beamed back will take years. Many more discoveries are yet to be announced.
So the portions of our universe, both nearby and far off that before WISE were dark to us, hidden by the shadows, are finally starting gleam brightly.
