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It bears mentioning that the Milky Way is only one of 150 billion galaxies visible to our telescopes - and each of these will have its own complement of planets.

Astronomers still can't decide what the shape of our universe is. Is it closed and finite, which is to say, is there a countable tally of all the galaxies that exist, even beyond the ones we can see? Or is it infinite? The latter possibility is still on the table.

Estimates are that at least 70 per cent of all stars are accompanied by planets, and since the latter can occur in systems rather than as individuals (think of our own solar system), the number of planets in the Milky Way galaxy is of order one trillion.

Our galaxy's pretty ordinary, garden-variety. So if we believe our galaxy has a super massive black hole, that tells us that most, if not all, galaxies host such a black hole at their centers.

I am undecided whether or not the Milky Way is but one of countless others all of which form an entire system. Perhaps the light from these infinitely distant galaxies is so faint that we cannot see them.

The bottom line is, like, one in five stars has at least one planet where life might spring up. That's a fantastically large percentage. That means in our galaxy, there's on the order of tens of billions of Earth-like worlds.

There may be aliens in our Milky Way galaxy, and there are billions of other galaxies. The probability is almost certain that there is life somewhere in space.

I've read that a naked eye can see six thousand stars in the hundred billion galaxies, but I couldn't believe it, what with the sky white with starlight. I saw a million stars with one eye and two million with both.

The Milky Way is nothing else but a mass of innumerable stars planted together in clusters.

We've accounted for 95 percent of all the stars in the Milky Way. The other 5 percent are big, bright stars - the kind that dominate the night sky, but are lamentably both rare and short-lived. If biology's your thing, you can forget those guys.