Astronomers discover Earth-sized diamond-encrusted white dwarf

              Stars are usually unfathomably hot objects fueled by a nuclear inferno that can only be extinguished when it runs its course, but astronomers have detected an elusive object that doesn’t come close to fitting that description. A white dwarf star 900 light years away might be the coldest star ever found in the cosmos. Hovering near a much larger pulsar, this ancient stellar remnant has a temperature of less than 3,000 K, or about 2,700 degrees Celsius.

              That’s cooler than an industrial acetylene torch. It’s so old that it has crystallized into what is essentially a Earth-sized diamond, and it was surprisingly difficult to spot.
               A white dwarf like the one found near the pulsar is what’s left over after a star about the size of the Sun runs through all its nuclear fuel. The outer layers are thrown off, and all that’s left is a tiny, super-dense core of elements like carbon and oxygen. They burn at an excruciatingly slow pace, taking billions and billions of years to finally go out, and even newly transformed white dwarfs are incredibly hard to spot compared to active stars. This one was only discovered because it happens to be nestled right up next to a pulsar.
In the same way a white dwarf is what’s left after a sun-sized star runs out of fuel, a neutron star is what’s left after a slightly larger one runs its course. A spinning neutron star is known as a pulsar because it appears to pulse as it strobes the universe with beams of radio waves while whirring around. The pulsar partnered up with our diamond-encrusted white dwarf goes by the catchy name PSR J2222-0137, and is 1.2 times the mass of our sun, but even smaller than the white dwarf. Astronomers were tipped off to the presence of something near the pulsar by distortions in its radio waves. An old-fashioned space hunt was on for the culprit.