Two of the oldest brown dwarf stars ever discovered could indicate the presence of nearby siblings.
The stars are fast moving (between 100 and 200 kilometers per second), have about seven percent the mass of the Sun, and are believed to be about from about 10 billion years ago when the universe was in its early days, a Royal Astronomical Society news release reported.
Brown dwarfs don't generate internal heat like many stars, as a result they "cool and fade" with time. These brow dwarf "seniors" are believed to have a surface temperature between 250 and 600 degrees Celsius, compared to the 5600-degree Sun.
The discovery was made at NASA's Wide-field Infrared Survey Explorer (WISE) observatory. The brown dwarfs were named WISE 0013+0634 and WISE 0833+0052 and can be found in the Pisces and Hydra constellations.
Finding a brown dwarf can be compared to finding "a needle in a haystack" because the sky is full of similarly-colored objects such as "reddened stars, faint background galaxies (large distances from our own Milky Way) and nebulous gas and dust," the news release reported.
The researchers were able to pick out the brown dwarfs by using WISE to scan the sky multiple times.
The behavior of these particular objects is unusual, and could be an indicator of that stars' ancient atmospheres. The stars' atmospheres are made up of primarily hydrogen, and lack the heavier elements that younger stars possess.
"Unlike in other walks of life, the Galaxy's oldest members move much faster than its younger population," lead researcher Doctor David Pinfield at the University of Hertfordshire, said.
"These two brown dwarfs may be the tip of an iceberg and are an intriguing piece of astronomical archaeology," Pinfield said. "We have only been able to find these objects by searching for the faintest and coolest things possible with WISE. And by finding more of them we will gain insight into the earliest epoch of the history of the Galaxy."
