Is Sirius a star?

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Message 1180357 - Posted: 24 Dec 2011, 2:26:54 UTC
Last modified: 24 Dec 2011, 2:29:35 UTC

From my geographic latitude, about 63 degrees north, I am able to see the brightest star in the sky, Sirius, in the winter evenings low in the sky.

Because of the turbulent atmosphere, the star is apparently shining (or twinkling) in all kinds of colors, including red and blue.

But it is a blu(e)ish white main sequence star, early spectral class A. It also has a white dwarf companion making an orbit around it every 50 years or so, but this white dwarf is very difficult to detect visually.

If there was no atmosphere at all, I would still be able to see that Betelgeuse (maybe with z, rather), is having a strong reddish color and both Rigel as well as Sirius would appear to be having a blueish or whitish color (or maybe both).

Have anyone here ever had a look at Sirius using a telescope with this star well above the horizon? How does it appear when it comes to the colors?

Thank you for answers!

Merry Christmas!

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Profile Bob DeWoody
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Message 1180363 - Posted: 24 Dec 2011, 3:18:53 UTC

Sirius is a star, a very close one. Actually it is a binary system. Do a google search to find more information.


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Message 1180377 - Posted: 24 Dec 2011, 5:21:38 UTC

Sirius A is a class A star. It's supposed to be white or slightly bluish-white. Some people do report seeing it with all kinds of different colors though, especially when it's low on the horizon as it would have to be at your latitude. If you combine that with the Dogon legends it definitely gives the Dog star an aura of mystery. It's only 8.6 ly away. I'd like to fly over there and have a look.


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Profile Gary CharpentierCrowdfunding Project Donor
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Message 1180380 - Posted: 24 Dec 2011, 5:30:17 UTC - in response to Message 1180357.

Color depends if you are young or old. Young it may look bluish-white. Old and it will be white. Has to do with how our eyes age and color perception of faint objects.

If you just move yourself to an area with stable air you can see the colors of the brightest stars and planets as our ancestors did.


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Message 1180573 - Posted: 25 Dec 2011, 3:52:20 UTC - in response to Message 1180380.

Sirius is a very large star and 10000 times more lumious than our sun. Its extremly large size isnt the largest some are so large the lARGEST if you could orbit it at 600 mph would take 1500 years at its equartor. I dont recall its name antares maybe. Sirius also has a campanion star sirius b. The Dogon people of africa belive they come from this star a red dwarf star that is not visible to the naked eye with an ellipical orbit. How ever could these stone age people in modern times know this through elders tales.

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Message 1180582 - Posted: 25 Dec 2011, 6:31:49 UTC - in response to Message 1180573.

The Dogon people of africa belive they come from this star a red dwarf star that is not visible to the naked eye with an ellipical orbit. How ever could these stone age people in modern times know this through elders tales.


The Dogons simply guessed that their origins were from another planet. When Sirius B was discovered, the simply retro-fitted their belief to this star. Star charts from where they claimed they came from years prior indicate that they had no clue where Sirius B was at the time.

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Message 1181332 - Posted: 29 Dec 2011, 10:21:32 UTC
Last modified: 29 Dec 2011, 10:23:30 UTC

The fleeting colour changes seen in bright, white stars, most prominent when they’re at low altitudes, are due to scintillation: "twinkle, twinkle” and all that. Turbulence in the atmosphere causes transient changes in its index of refraction, so from moment to moment the frequencies that can be brought to focus in the eye will vary. The effect is rarely seen from planets, because they’re much less like point-sources and the variations from different parts of the disc tend to average out. Faint stars often seem to ‘wink’ on and off, but bright stars—Sirius especially—will display flashing colours under the right atmospheric conditions.

P.S. See Wikipedia’s article on astronomical scintillation.


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Message boards : SETI@home Science : Is Sirius a star?


 
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