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Van Maanen’s Star

September 12, 2017

The Sun outshines most other stars, but that won’t always be the case. Billions of years from now the nuclear reactions in its core will shut down. The Sun will then expel its outer layers into space. All that will remain will be the Sun’s dead core, known as a white dwarf — a faint cosmic cinder.

We can get a glimpse of that future by looking at a white dwarf that was discovered 100 years ago. It’s the closest single white dwarf yet seen.

The star is named for the astronomer who discovered it: Adriaan van Maanen, who worked at Mount Wilson Observatory in California. Yet the discovery was an accident. Van Maanen was actually examining another star. He was comparing photographic plates taken in 1917 with some taken three years earlier. He noticed a faint star in the constellation Pisces that had moved quite a bit during the interval — a sign that the star was close by.

To confirm that, Van Maanen and other astronomers measured its distance. And they found that, as expected, it’s one of our nearest neighbors — just 14 light-years from Earth. But the star is so faint you that need a telescope to see it; the Sun emits more light in 24 hours than this feeble star does in 15 years.

Only two other white dwarfs are closer to Earth. But both of them are companions to much brighter stars. In contrast, Van Maanen’s Star is all alone and fading from view — just as the Sun will billions of years from now.

Tomorrow: a final look at a giant planet.

Script by Ken Croswell, Copyright 2017


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