What is a Galaxy (& what is the Milky Way)?

Most people are familiar with the words solar system, galaxy, Milky Way and Universe, and most people probably have a vague idea of what they mean. I’ve been throwing these words around quite a bit on the blog but I realized I’ve never actually explained what they are.

I thought I had a pretty good understanding of what they actually mean, but in an earlier post I defined what a solar system is, and I learnt a fair bit myself about where a solar system actually ends. The same goes with this post, I knew roughly what a galaxy is, turns out I didn’t really know about galaxy superclusters.

So in this post I’ll be talking about galaxies, clusters of galaxies, and I’ll explain what the Milky Way has to do with all of this.

Has Kepler already found the first Earth-like exoplanet?

The holy grail of exoplanet hunting is to find a planet like Earth orbiting a distant star in its habitable zone (the region around a star where life can exist).

Since 1992 the pace of exoplanet discovery has accelerated, with 538 confirmed planets found as of March 2011, and the space telescope Kepler, launched in 2009, has already made some exciting planetary discoveries, including a 6 planet solar system. And now it may have found the first known Earth-like exoplanets.

Panspermia: did life on Earth come from space? – Part 2, intentional panspermia & cosmic amino acids

Panspermia is the idea that life could have emerged on an alien planet, and then could have travelled through space to Earth, where it flourished and evolved into all the life we see today. So you, your family and your cat could all be aliens.

In the first post I looked at the idea that this alien life could have been simple bacteria, and could have travelled to Earth early in its history either in spores or in asteroids or comets. This is very much the ‘traditional view’ of panspermia.

In this post I’ll look at some alternative forms of panspermia, such as the idea that intelligent aliens may have deliberately seeded Earth with life.

How far away is the nearest galaxy?

Most of us know space is a big place, but few of us have an idea of just how big it really is. For instance, how feasible would it be for humans to travel right the way across our galaxy, and would we ever be able to reach other galaxies. In fact, what actually is a galaxy?

Some Fermi Paradox Answers: some cool, some lunatic, some faintly disturbing (part 1)

Before I talked about the Fermi Paradox. But the real fun comes in trying to answer Fermi’s question; where is everybody?

Hundreds, if not thousands of people have tried to do this and there are countless written sources, mostly websites but some cool books too. One of the best I’ve come across is a book by Stephen Webb called ‘Where is Everybody’. In it he details 50 explanations for the paradox, and I’ll borrow lots of them here.

You can categorize the different answers in lots of different ways, I group them into the boring ones, the lunatic ones, the cool answers and the, well frankly, faintly disturbing solutions…