h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

First, I am not very familiar with astronomy. But I do like the images the astronomers give us, like the great book "Galaxies" by Timothy Ferris. It really makes me wonder what this is all about ... if I ever meet whoever "designed" the universe, my first question would be "What were you thinking ... so BIG?"

But I do have a question. Years ago, I took an evening astronomy course, non-credit lectures, given by a very interesting professor. For example, he would be talking and all of a sudden stop, walk over to a chair against the wall and sit down for a minute. Then he would say, "Sometimes I get all wrapped around myself."

I naively asked at one point "Are all stars in galaxies, or are they just denser in galaxies?" He responded, "Some things are hard to know."

So, is there any evidence of stars in inter-galactic space? My guess is that they would be so dim, i.e. a single star outside the Milky Way, that we could not see them. But I dunno ...

Hi Steve,

The answer is yes, as the following press release will attest.

http://oposite.stsci.edu/pubinfo/PR/97/02/PR.html

Logically it would be expected that IG stars would exist, when stars are thrown out of their host galaxy due to a galactic collision or an internal collision within a galaxy. The trouble would be trying to find them, because intergalactic space is measured in the millions (sometimes billions) of light-years, and the light of a single star across such distances is negligible.

Many galaxies are accompanied by satellite clusters of stars which are not part of the galaxy itself. Our own Milky Way has a number of satellite star-clusters, known as the Magellanic Clouds.

There is also some evidence that planets which are unconnected to any stars are also floating around the Milky Way. They may actually be quite common, but because they don't emit any light, it would be almost impossible to find them with current technologies.

Woodpigeon

Great response, thanks. I had not heard that report of IG stars found by the Hubble.

I've hired there is good theoretical of planets being expelled form solar systems, when the orbits of different planets come into sync with each other and become unstable (or something like that)

I'm watching a video course from The Teaching Company titled "My Favorite Universe". The astrophysicist lecturer described collisions between galaxies, which could result in a star passing close to our sun, possibly "capturing" the Earth. Or, worse, throwing the planet into interstellar space, which would be ... bad.