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Seeing Sextuple
StarDate:
July 9, 2021Star systems with more stars than you can count on one hand are rare. In fact, you could probably total them all up by yourself if you use your hands and feet.
One of those systems is called 65 Ursae Majoris. It consists of six known stars. The two stars at the center of the system orbit each other. All the other stars orbit them.
The stars at the center are almost identical — they’re almost twice as big and heavy as the Sun. They’re so close together that they orbit each other every couple of days.
The first two stars out from them are more than twice the Sun’s mass. One of them orbits the central pair every 21 months, and the other, once every 118 years.
The two most remote members of the system are less well known. One of them takes thousands of years to complete a single orbit. And the other — the one you need an extra hand to tally up — takes hundreds of thousands of years. Astronomers have been watching the stars for only a fraction of that time, though, so they haven’t plotted enough of their orbits to know the details. And it could take centuries to figure it all out.
65 Ursae Majoris is in Ursa Major, the great bear. The bear’s body and tail are outlined by the Big Dipper, which is in the northwest on July evenings. 65 Ursae Majoris is to the left of the dipper. At a distance of 700 light-years, though, even the combined light of its six stars isn’t enough to see without a telescope.
Script by Damond Benningfield
