Post by Chicago Astronomer - Astro Joe on Jan 7, 2005 14:41:36 GMT -6
I found this quite interesting, and something I never gave a thought to...
The Big Dipper is also a star cluster, with the majority of the stars travelling together in the same direction.
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This from Earth and Sky.org:
Dubhe and Merak are sometimes called The Pointers. They’re your guide to the North Star any time the Big Dipper is visible. But there are other reasons to linger on the Big Dipper pattern. Notice the second star from the end of the Dipper’s handle. This star is called Mizar. There are really two stars here, both of which are visible to the eye. I’ve marked Mizar only on today’s chart, but if you look . . . and if your sky is dark enough . . . you’ll see Mizar’s tiny companion on our sky’s dome as well. The fainter star is called Alcor.
Mizar and Alcor are sometimes called The Horse and Rider. Most noticeable sky patterns on our sky’s dome are not really connected in space. But five of the seven brightest stars in the Big Dipper are moving through space in the same direction and at the same speed. Only Dubhe and Alkaid are speeding through space in different directions. The five stars that move together are part of what is called the Ursa Major Moving Group. This is a true star cluster, one of many in our sky, but of great interest because it is the nearest star cluster to us. These stars all lie approximately 80 light-years away.
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You look up at the sky for decades, and never give it a second thought. The learning never ends.
The Big Dipper is also a star cluster, with the majority of the stars travelling together in the same direction.
--------------
This from Earth and Sky.org:
Dubhe and Merak are sometimes called The Pointers. They’re your guide to the North Star any time the Big Dipper is visible. But there are other reasons to linger on the Big Dipper pattern. Notice the second star from the end of the Dipper’s handle. This star is called Mizar. There are really two stars here, both of which are visible to the eye. I’ve marked Mizar only on today’s chart, but if you look . . . and if your sky is dark enough . . . you’ll see Mizar’s tiny companion on our sky’s dome as well. The fainter star is called Alcor.
Mizar and Alcor are sometimes called The Horse and Rider. Most noticeable sky patterns on our sky’s dome are not really connected in space. But five of the seven brightest stars in the Big Dipper are moving through space in the same direction and at the same speed. Only Dubhe and Alkaid are speeding through space in different directions. The five stars that move together are part of what is called the Ursa Major Moving Group. This is a true star cluster, one of many in our sky, but of great interest because it is the nearest star cluster to us. These stars all lie approximately 80 light-years away.
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You look up at the sky for decades, and never give it a second thought. The learning never ends.
