Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Pumblechook on 17/01/2009 12:59:15

Title: From what distance could you see the Sun with the naked eye?
Post by: Pumblechook on 17/01/2009 12:59:15

How bright is it compared to the stars we can see from Earth?

Title: From what distance could you see the Sun with the naked eye?
Post by: lightarrow on 17/01/2009 15:05:27

Quote from: Pumblechook on 17/01/2009 12:59:15

How bright is it compared to the stars we can see from Earth?

It depends on which stars.
http://en.wikipedia.org/wiki/Apparent_magnitude
If I computed it correctly, the Sun should be ~ 13 billions of times brighter than Sirius (the brightest star on the sky, after the Sun).

Title: From what distance could you see the Sun with the naked eye?
Post by: syhprum on 17/01/2009 16:28:05

I think pumblechook had in mind the intrinsic brightness of a star of the Suns class, at a guess I would say it could be seen up to about 1000 light years away.

Title: From what distance could you see the Sun with the naked eye?
Post by: lightarrow on 17/01/2009 19:27:43

I would say that at ~ 60 l.y. Sun would be of 6^th magnitude.

Title: From what distance could you see the Sun with the naked eye?
Post by: Soul Surfer on 18/01/2009 00:25:22

I agree with light arrow. The absolute magnitude of the sun is about 4.  The absolute magnitude of a star is its brightness at a distaance of 10 light years.  The very brightest stars have an absolute magnitude of -6 which is considerably brighter than the planet venus that is currenly visible in the south west shortly after sunset as a very bright star at magnitude -4.  The full moon has a magnitude of -12.

The dimmest stars have an absolute magnitude of around 15 which need a pertty big telescope to be seen.

Title: From what distance could you see the Sun with the naked eye?
Post by: syhprum on 18/01/2009 14:42:02

Give or take the odd supernova then the naked eye universe has a radius of about 200ly.

Title: From what distance could you see the Sun with the naked eye?
Post by: lyner on 18/01/2009 18:03:07

SS
Isn't absolute magnitude described in terms of Parsecs? (Not a lot of difference in Cosmological terms, of course, but I seem to remember that it is)

Title: From what distance could you see the Sun with the naked eye?
Post by: Soul Surfer on 18/01/2009 23:33:20

Yes you are right it is parsecs or about 33 light years.  Sorry, dashed off the answer and forgot do double check the detail. but it doesn't make all that much difference.

Agreed most of the visible stars are within a couple of hundred light years but there are a few very bright ones that are further away.  Of course the milky way  the magellanic clouds and the Andromeda nebula are all much further away an visible to the naked eye