The Universe Revealed

What is a satellite galaxy?

What is a satellite galaxy?

I don't think that people realize that the Milky Way galaxy has 30 satellite galaxies orbiting it within 1.4 million light years. There may be more, but this is how many have been discovered. The question is: what is a satellite galaxy?

By definition, a satellite galaxy is a small galaxy that orbits a larger galaxy due to gravitational attraction. A galaxy is a gravitational collection of stars, planets and nebulae that has a center of mass.

I thought that I would discuss some of the larger satellite galaxies that orbit the Milky Way. The largest is the Large Magellanic Cloud. This galaxy has a diameter of 14,000 light years and is 163,000 light years away. It contains several billion stars, the exact number of which is not determined. This satellite galaxy is the fourth largest galaxy in the Local Group, consisting of the Milky Way, Andromeda and Triangulum galaxies.

Although the LMC is irregular, it was once a nice barred spiral galaxy that has become distorted by the gravitational effects of the Milky Way. It still retains a ray or arm.

This amazing galaxy has a lot going in it. It contains 60 globular star clusters, 400 planetary nebulae, and 700 open star clusters. There is prodigious amount of new star formation occurring there. It's also the location of some very strong X-ray sources, supposedly from supernovae ruminants or a pulsar.

The Small Magellanic Cloud is about half the size of the LMC. It's 200,000 light years away and has a diameter of 7,000 light years. This galaxy has several hundred million stars. Again, it was once a nice spiral but has been torn apart by the Milky Way. This galaxy contains a large number of X-ray sources, some of which are pulsars, which suggests that it's older than the LMC.

There are lots of smaller satellite galaxies associated with the Milky way, including Sagittarius Dwarf, Ursa Major II, Ursa Minor Dwarf, Bootes Dwarf, Sculptor Dwarf, Draco Dwarf, Sextans Dwarf, Ursa Major I, Carina Dwarf and Formax Dwarf. These smaller satellite galaxies contain several million stars up to a hundred million.

Andromeda galaxy has 14 satellite galaxies orbiting it, which suggests that most spiral galaxies have these dwarf galaxies orbiting them. Not too much is known about them, but they show the diversity of galaxies in our Local Group.

My question is this: what's the possibility that life, especially intelligent life, could be living in these satellite galaxies? Think of how many planets must be orbiting the stars in these dwarf galaxies. We've only scratched the surface of finding exo-planets. And, to put this into perspective, our local group of galaxies is a tiny speck compared to the larger galaxy clusters and super clusters. There just has to be life in all of that, and I'll bet that ET is looking back at us and wondering if we're intelligent.

If there are intelligent species in those satellite galaxies, I'll bet their view of our Milky Way Galaxy is spectacular.

Thanks for reading.