[mantooon]

I recently found these forums and I really appreciate the knowledge that people share. I have been browsing the forums a few days, already learnt much and I am seeking for more :)

- The stars we see in the sky belong to our galaxy?
- Are all those stars suns of other solar systems?
- Are there multiple solar systems in a galaxy?

Thanks in advance

[Capuchin]

1. Yes, they will be in our galaxy - other galaxies are so far away that it's hard to pick out individual stars with the naked eye (you might see a whole other galaxy as a single star in the sky). With tools such as the hubble space telescope we can see much better detail in these.

2. Many of them are, we have found around 330 planets orbiting other stars. This is a hard question to answer, as it's hard to say "we know for certain that there are not planets around this star". It's likely that some stars will not have any planets - but that a very hard thing for us to work out without better detecting technology. We don't even know if we have found all the planets in the solar system!

3. Yes, nearly all (if not all) of the ones detected so far are in our galaxy - because they are so much closer to us and easy to observe. Here is a link to some information about an extragalactic planet we have identified. It was pretty much a fluke discovery, someone was watching the right piece of sky at the right time: Extrasolar Visions - The Q0957+561 Planet

I would like to discourage you from using the term "solar system" when talking about other planetary systems. The word "solar" refers to our sun, which is called Sol. We refer to "extrasolar planets" which are planets outside of the solar system. It's starting to become more important to use the proper terms in this sort of research as we find out more :)

[FlyYakker]

- Every star that you see is within our galaxy. Keep in mind that you can only see a very small percentage of the stars in the galaxy. It is actually also possible to see other galaxies, but they are at vast distances and tend to be dim and look cloud-like without a telescope.

- Are you asking if all the other suns have planets around them? Although stars with planets have been identified, it's not all that many as compared to the total number of stars that are seen. It appears that most stars are without planets, or simply have planets too small for us to detect, but it's work in progress. On the other hand, there are solar systems (oops! Extra solar systems) where two suns revolve around each other.

- Yes, there are multiple extra solar systems within a galaxy... keeping in mind that the number of stars in our galaxy is very, very large... maybe a billion or so (no one really knows - it's the lowest estimate I got when I "Googled" the question), and we don't really have any idea what percentage of them have planets around them.

You didn't ask, but if you were able to travel around the world (Northern and Southern Hemispheres) and looked up at the sky under the very best viewing conditions, you would be able to see, in total, about 6000 to 9000 stars (another case of varied answers) with the naked eye. Therefore, at most, you are capable seeing only a very small part of our galaxy. It boggles the mind.


I hope you live in, or are able to get to, a location with little or no light pollution so you can look up and see the stars at their best. It is an awesome sight.


There are a number of good general astronomy web sites, e.g.. SkyandTelescope.com (a magazine site but with free features) and of course NASA publishes many fine photographs from the Hubble Telescope, etc.

[ebaines]

There is only one other galaxy that can be seen with the naked eye - Andromeda. It requires extremely dark skies however. It appears as a fuzzy smudge, abut 1/2 degree across (about the same apparent size as the moon).

[FlyYakker]

Don't forget the Greater and Lesser Magellanic Clouds which are visible in the Southern Hemisphere and are considered satellite galaxies to our own Milky Way Galaxy. Apparently there is also some debate whether certain other galaxies can really be seen with the naked eye as well. A lot depends on how good you are at locating and identifying the object and on how good the "seeing" conditions are (and maybe how good of an imagination you have. ;)). Certainly the Andromeda galaxy is the only "easily" seen one that can be seen in northern skies, and even then you need a good clear dark night.

[mantooon]

Thank you all for your detailed replies.

Are the stars in the sky so much distant from earth, that sometimes we watch a star that no more exists?

@FlyYakker (sigh) I used to spend weekends away from the city so I did watch the marvellous night sky. Unfortunately, not anymore...

[ebaines]

Are the stars in the sky so much distant from earth, that sometimes we watch a star that no more exists?

It's certainly possible. The stars you see in the night sky with the naked eye are all within 1000 light-years of Earth. So the star light has actually been traveling for as much as 1000 years before it reaches your eye, and so it's possible that in the intervening 1000 years the star has dies out (or gone nova). However, these are very rare events, so the probability that any one star you can see with the naked eye no longer exists is very small. However, if you include all the stars that astronomers can see using advanced telescopes, then most certainly yes this is true.

[sandra xuereb]

What is the name of the star nearest to the sun?

[ebaines]

What is the name of the star nearest to the sun?

The nearest star to us, other than our own sun, is Proxima Centauri. It's 4.2 light years away. See:

Proxima Centauri - Wikipedia, the free encyclopedia