Looking Up: Free Streaming Featuring Major Stars

Feb 3, 2020

Credit public domain / earthsky.org

This week on Looking Up Hal grabs a celestial lion by the tail.

One of my favorite constellations is Leo the Lion, now rising in the east after sunset. Leo has lots of interesting stars, and it also actually looks a bit like what it is supposed to be, a lion.

The star that makes up the, well, start near the backside of the lion is the very interesting star Zosma. It seems way back when such things were getting named, some unknown Greek named the star Zosma, thinking it meant “back.” It actually translates better as “girdle” which robs the star of a bit of its dignity.

As stars go, though, Zosma is pretty neat. It’s relatively close at only about 58 ly away, and so it’s been studied fairly closely. It really spins on its axis quickly, and even though it’s bigger than our Sun, a day on Zosma only lasts a few hours.

But what makes Zosma really weird is that it seems to be part of a collection of stars that are all moving through space in the same direction at roughly the same speed. This group includes Sirius and most of the stars in the Big Dipper. The group is actually named the “Ursa Major stream.” That would seem to imply all those stars got their starts in the same part of space, perhaps in a long-gone dust nebula, and all got tossed out in the same direction. We don’t really know. Oh, and to make things even weirder, Zosma is vibrating every few hours, like a bell that has been rung. Why? We don’t know! Pretty freaky, right?

If you’d like to take a closer look at Zosma, or any of the other wonderful and amazing things in the sky, please visit csastro.org for a link to information on our monthly meetings and our free public star parties.