satelites and stars

merlinspeed · #1 (**permalink**) 10-03-2008, 09:47 PM

is it the case that you can see satelites orbiting the earth on a clear nite.

also which is the brightest star in the sky.

Fishing By Nature Forum

am i allowed to put that link in here not sure.....

UB4 gardener · #2 (**permalink**) 11-03-2008, 05:19 PM

also the international space station. there is a website Heavens-Above Home Page that gives details of some of the brighter objects.

Chris

petermcgain · #3 (**permalink**) 12-03-2008, 08:20 AM

Sirius, the Dog Star, is the brightest star (after our sun of course). It's bottom left of Orion and Orion's belt points down to it. Apparently it's 25 times brighter than our sun, which isn't saying a lot - there are many others much brighter, but it appears bright to us because it's so close (in astronomical terms that is) at 8.3 light years away. That means the light from the star we can see today left just before we went out and partied for the Millenium. Compare that to the Andromeda Galaxy which can be seen with the naked eye near Pegasus which is more than 2 million light years away! Can't imagine what sort of partying was going on then.

James M · #4 (**permalink**) 12-03-2008, 09:42 AM

Quote:

Originally Posted by petermcgain

Sirius, the Dog Star, is the brightest star (after our sun of course). It's bottom left of Orion and Orion's belt points down to it. Apparently it's 25 times brighter than our sun, which isn't saying a lot - there are many others much brighter, but it appears bright to us because it's so close (in astronomical terms that is) at 8.3 light years away. That means the light from the star we can see today left just before we went out and partied for the Millenium. Compare that to the Andromeda Galaxy which can be seen with the naked eye near Pegasus which is more than 2 million light years away! Can't imagine what sort of partying was going on then.

That's something that amazes me with these distances, I remember seeing a photo of galaxies 10 billion light years away so we're seeing them as they were 10 billion years ago, so would it be theoretically possible to see the big bang if you looked further out enough?

Cidermaker · #5 (**permalink**) 12-03-2008, 10:15 AM

" ... so would it be theoretically possible to see the big bang if you looked further out enough?"

Yes, sort of. The light would be so red-shifted that it would be impossibly red and pale, so we wouldn't see anything quite that far back, but cosmologists are very interested in the Cosmic Microwave Background. This is believed (by pretty much everybody) to be the cosmic radiation shortly after the big bang. Cosmologists are interested in it because it is lumpy, and this lumpiness tells us a lot about how matter was distributed, and is important for theories of how galaxies formed.

So in a sense, yes. The CMB is the closest we can get to seeing the big bang, and it is quite close.

James M · #6 (**permalink**) 12-03-2008, 10:22 AM

Quote:

Originally Posted by Cidermaker

" ... so would it be theoretically possible to see the big bang if you looked further out enough?"

Yes, sort of. The light would be so red-shifted that it would be impossibly red and pale, so we wouldn't see anything quite that far back, but cosmologists are very interested in the Cosmic Microwave Background. This is believed (by pretty much everybody) to be the cosmic radiation shortly after the big bang. Cosmologists are interested in it because it is lumpy, and this lumpiness tells us a lot about how matter was distributed, and is important for theories of how galaxies formed.

So in a sense, yes. The CMB is the closest we can get to seeing the big bang, and it is quite close.

That's interesting, thanks.

Rich_ · #7 (**permalink**) 15-03-2008, 09:23 AM

Merlin'

It is surprising how many satellites you can see on a clear moonless night. They just look like stars, points of light, moving through the sky & they vary in brightness. They don't flash like aircraft though.

If you look at an area of sky for more than a few minutes you are likely to see one or more, and through binoculars you wil see even more that are below naked eye magnitude. The space station is often as bright or brighter than Sirius.