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Old 19-04-2018, 10:16 AM
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Stonius (Markus)
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Scientists Think We're On The Cusp Of Finding The Sun's Siblings

http://www.iflscience.com/space/scie...suns-siblings/

If the great thing about this satellite is the sheer number of stars that it can measure, I wonder if a network of amateur spectographers could contribute too?

Keeping in mind I know next to nothing about spectroscopy and expect to be schooled in exactly why this is not possible in about 5 minutes time :-)

But the idea of knowing which stars came from the same stellar nursery is exciting nonetheless. :-)

Markus
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Old 19-04-2018, 10:47 AM
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Originally Posted by Stonius View Post
Keeping in mind I know next to nothing about spectroscopy and expect to be schooled in exactly why this is not possible in about 5 minutes time :-)
Two words... "absolute magnitude"

If we consider that our sibling was cast out at any sort of significant velocity say 4 billion years ago (let's allow it to grow up with Sol for 500million years), at a velocity of say 20km/s (a low velocity for a cast out star), it would be about 82000 parsecs away by now...

Even at 1 billion years ago, it would be at 23000 parsecs away.

The Sun's absolute magnitude is 4.7... if our sibling is the same G-type star, it would be very very very very faint...

Trying to get a spectra of such a faint star would require many minutes, if not hours of exposure. Only a space telescope (maybe Magellan on Earth) could manage that...

Merlin, care to comment on exposure times for spectra?

OIC!

Last edited by OICURMT; 20-04-2018 at 11:52 PM. Reason: apparent mag is viewed from the earth (obviously) , absolute from 1 parsec
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Old 19-04-2018, 12:54 PM
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Quote:
Originally Posted by OICURMT View Post
Two words... "apparent magnitude"

If we consider that our sibling was cast out at any sort of significant velocity say 4 billion years ago (let's allow it to grow up with Sol for 500million years), at a velocity of say 20km/s (a low velocity for a cast out star), it would be about 82000 parsecs away by now...

Even at 1 billion years ago, it would be at 23000 parsecs away.

The Sun's apparent magnitude is 4.7... if our sibling is the same G-type star, it would be very very very very faint...

Trying to get a spectra of such a faint star would require many minutes, if not hours of exposure. Only a space telescope (maybe Magellan on Earth) could manage that...

Merlin, care to comment on exposure times for spectra?

OIC!
I suppose I thought that as with open clusters, our sun's siblings would be lurking somewhere nearby. But aparrently we're galactic rejects and no-one wants to play with us

It's probably a good thing because a friendly companion star would disrupt the oort cloud and probably kill us.
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Old 20-04-2018, 01:25 PM
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Quote:
Originally Posted by OICURMT View Post
Two words... "apparent magnitude"

If we consider that our sibling was cast out at any sort of significant velocity say 4 billion years ago (let's allow it to grow up with Sol for 500million years), at a velocity of say 20km/s (a low velocity for a cast out star), it would be about 82000 parsecs away by now...

Even at 1 billion years ago, it would be at 23000 parsecs away.

The Sun's apparent magnitude is 4.7... if our sibling is the same G-type star, it would be very very very very faint...

Trying to get a spectra of such a faint star would require many minutes, if not hours of exposure. Only a space telescope (maybe Magellan on Earth) could manage that...

Merlin, care to comment on exposure times for spectra?

OIC!
Don't you mean absolute magnitude (4.83)
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Old 20-04-2018, 11:50 PM
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Don't you mean absolute magnitude (4.83)
ha ha... you are correct... original post corrected.

did the sun dim over the last 30 year? The old book I had listed it at 4.7... oh well, so much for the sun's influence on global warming
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Old 30-04-2018, 06:04 PM
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If we find the sun's siblings it will just start fighting with them...
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