It is the size of the Earth, around 11 billion years old, and is made entirely from diamond. The Dwarf Star is the coldest ever detected. A team of astronomers have identified the coldest, faintest white dwarf star estimated to be around 11-billion-years-old.
And it is so cold that it has turned into crystallized carbon, making it the biggest bling in the universe. It has been spotted 900 light-years away on the same pathway to the constellation Aquarius. University of Wisconsin-Milwaukee’s Professor David Kaplan said, “It really is a remarkable object.These things are out there, but because they are so dim, they are very difficult to find.”
Using the National Radio Astronomy Observatory’s Green Bank Telescope and Very Long Baseline Array, researchers at the University of Wisconsin-Milwaukee have identified an ancient stellar remnant believed to be so cold that its carbon has crystallised, forming an earth-sized diamond in space.
White dwarfs are the stars which are coming to the end of their life and slowly cool and fade over billions of years. Researchers have worked out the dwarf star would be no more than a comparatively cool 3,000 degrees Kelvin, around 2,700 Celsius.
White dwarfs are the extremely dense end-states of stars like our Sun that have collapsed to form an object approximately the size of Earth. Composed mostly of carbon and oxygen, white dwarfs slowly cool and fade over billions of years. The object in this new study is likely the same age as the Milky Way, approximately 11 billion years old.
Pulsars are rapidly spinning neutron stars, the superdense remains of massive stars that have exploded as supernovas. As neutron stars spin, lighthouse-like beams of radio waves, streaming from the poles of its powerful magnetic field, sweep through space. When one of these beams sweeps across Earth, radio telescopes can capture the pulse of radio waves.
The pulsar companion to this white dwarf, dubbed PSR J2222-0137, was the first object in this system to be detected. It was found using the GBT by Jason Boyles, then a graduate student at West Virginia University in Morgantown.
These first observations revealed that the pulsar was spinning more than 30 times each second and was gravitationally bound to a companion star, which was initially identified as either another neutron star or, more likely, an uncommonly cool white dwarf. The two were calculated to orbit each other once every 2.45 days.
The pulsar was then observed over a two-year period with the VLBA by Adam Deller, an astronomer at the Netherlands Institute for Radio Astronomy (ASTRON). These observations pinpointed its location and distance from Earth.
Knowing its location with such high precision and how bright a white dwarf should appear at that distance, the astronomers believed they should have been able to observe it in optical and infrared light.
Remarkably, neither the Southern Astrophysical Research (SOAR) telescope in Chile nor the 10-meter Keck telescope in Hawaii was able to detect it.
“Our final image should show us a companion 100 times fainter than any other white dwarf orbiting a neutron star and about 10 times fainter than any known white dwarf, but we don’t see a thing,” said Bart Dunlap, a graduate student at the University of North Carolina at Chapel Hill and one of the team members. “If there’s a white dwarf there, and there almost certainly is, it must be extremely cold.”
The researchers calculated that the white dwarf would be no more than a comparatively cool 3,000 degrees Kelvin (2,700 degrees Celsius). Our Sun at its center is about 5,000 times hotter.
Astronomers believe that such a cool, collapsed star would be largely crystallized carbon, not unlike a diamond. Other such stars have been identified and they are theoretically not that rare, but with a low intrinsic brightness, they can be deucedly difficult to detect. Its fortuitous location in a binary system with a neutron star enabled the team to identify this one.
A paper describing these results is published in the Astrophysical Journal.