A star whose surface temperatures are similar to those of the Earth's polar regions was discovered at a distance of 7.2 light years, the fourth neighbor from the Sun
A brown dwarf, a cold and dark star, perhaps the coldest of its kind whose surface temperature, even though it is a star and not a planet, is similar to that of the Earth's poles, was conceived by an astronomer from the University of Pennsylvania (Penn State) who used NASA's Wise and Spitzer space telescopes. The images taken by the two telescopes also pointed to the fact that the distance to the new object is 7.2 light years, making it the fourth nearest star to the Sun.
"It's exciting to discover a new neighbor so close to our solar system," said Kevin Lohmann, professor of astronomy and astrophysics at Penn State and researcher at the Penn State Center for Extrasolar Planets and Habitable Worlds. "In addition, its extreme temperature may tell us a lot about the atmosphere of planets similar to it in cold temperatures."
Brown dwarfs begin life like stars as a ball of gas that collapsed in on itself from a cloud of dust and gas, but they lack the mass to burn their nuclear fuel and radiate sunlight. The temperature on the surface of the new brown dwarf, named WISE J085510.83-071442.5, ranges from minus 48 to minus 13 degrees Celsius. The previous record recorded by a cold-heat dwarf was also discovered by Weiss and Spitzer, but there prevails a temperature similar to room temperature on Earth.
Although close to the Solar System, WISE J085510.83-071442.5 does not appear to be a target for manned space travel in the not-so-distant future. "Any planet that might orbit it would be too cold to support life as we know it," Lohmann said.
"The bone moves very quickly in the Wise data," Lohman said. "This is already a hint that this is something special." The closer the bone is, the more its movement can be felt in the shadows at intervals of months. This is similar to low-flying airplanes that seem to fly faster than high-flying airplanes.
Wise was able to locate the rare object because he scanned the entire infrared sky twice, and in some cases he viewed the same areas three times. Cold objects such as brown dwarfs can be invisible to telescopes operating in visible light, but their heat signature—even if faint—stands out in infrared light.
After detecting the rapid motion of WISE J085510.83-071442.5 in March 2013, Lohmann spent time analyzing additional images of the same region of the sky taken by the Spitzer Space Telescope and the Gemini Southern Telescope in Chile. Spitzer's infrared observations allowed researchers to determine the freezing temperature of the brown dwarf.
The mass of WISE J085510.83-071442.5 is about 3-10 Jupiter masses. With such a small mass it could have been a Jupiter-type gas giant ejected from its own solar system. However, the scientists estimate that it is a brown dwarf and not a planet because such stars are quite common. So this is one of the lightest known brown dwarfs.
The joint discovery by Weisz and Spitzer, photographed from different positions in the Earth's orbit around the Sun, made it possible to measure its distance using the parallax effect, the same principle that explains why the finger in front of the nose appears as if it is moving left and right when one closes one eye alternately.
In March 2013, Lohmann analyzed the Wizz images and revealed a pair of brown dwarfs 6.5 light-years away, making the system the third closest to the Sun. His research into fast-moving objects showed that the outer solar system probably does not contain a large yet-to-be-discovered planet, which has received nicknames such as "Planet X" or "Nemesis".
"It is impressive to discover that even after decades of extensive study of the sky, we do not have a complete inventory of the nearest neighbors of the solar system," says Michael Warner, Spitzer Project Scientist at NASA's Jet Propulsion Laboratory, which manages and operates Spitzer. "The spectacular new findings illustrate the power of exploring the universe using new tools such as the infrared eyes of Weisz and Spitzer."
