“My God, it’s full of galaxies!”

Our own galaxy, the Milky Way, contains somewhere between 200 billion and 400 billion stars. The Universe, according to Wikipedia, contains more than 170 billion galaxies. According to findings of recent years, most if not all stars have at least one planet orbiting around them. If the average galaxy, to make a semi-educated guess, holds about 300 billion stars, then we’re talking about some 50,000 billion billion stars. That amounts to quite a mind-boggling lot of planets, if you’ll pardon my vast understatement.

If just one in ten stars have a planet in their habitable zone, and one in ten of those planets are earth type (made of rock, possessing an atmosphere, and more or less the same size), that’s still 500 billion billion planets with potential for harbouring life as we know it. Not to mention that we’ve no idea, really, how life considerably different from anything we know might arise and evolve under considerably different conditions on considerably different planets.

I’m pretty sure we’re not alone, though our nearest neighbours may be somewhat farther than just a quick stroll down a country road.

Continues below the video.

This computer-generated video contains only 400 000 galaxies, and still looks amazing.
Open video in new window.

For scale and perspective, consider the Hubble Ultra Deep Field image. At just over 3 arc minutes across (1/20th of the width of your pinky nail at arm’s length, or 1/10th of the width of the moon in the sky), showing a whopping 10,000 galaxies. And this is only what the Hubble telescope could see at the given exposure (11.4 days – you try to hold a camera steady for that long). The longer the exposure and sharper the telescope, the farther out one can look.

And that’s just ten square degrees. The full sphere of the sky is 41,253 square degrees. If evenly distributed, this amounts to 41,253,000 galaxies, which in itself is a pretty large number to wrap one’s mind around, though it is easily dwarfed by the 170 billion ones already mentioned. Future telescopes will be sharper and more light-sensitive yet, likely to reveal even more galaxies and in greater detail.

Though if you look at the night sky, even if you’re in a place with little or no light pollution from nearby cities or residential areas, with the possible exception of the Andromeda Galaxy which you will only catch sight of if conditions are right and you know where to look, every point or patch of light that you see are only relatively nearby stars and nebulae, and no more than a handful thousand of those at best. In other words, you see only a fraction of a fraction of a fraction of what’s in our own galaxy, let alone any other.

The most awesomely amazing things are out there, far out, in the dark patches between the stars that you can see, invisible to our eyes, and visible to our technological viewing aids only through special effort. But they are out there. And I’m pretty sure that right now, on at least one of the planets around one of the stars in one of those countless galaxies, someone is looking up at their night sky in our direction, wondering if there’s anyone out there.

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2 Responses to “My God, it’s full of galaxies!”

  1. The Old Wolf says:

    “Through it shone the Stars!
    Not Earth’s feeble thirty-six hundred Stars visible to the eye; Lagash was in the center of a giant cluster. Thirty thousand might suns shone down in a soul-searing splendor that was more frighteningly cold in its awful indifference than the bitter wind that shivered across the cold horribly bleak world.”
    -Isaac Asimov, Nightfall, Astounding Science Fiction, September 1941
    ——–
    I’d pay to see that…

  2. The Old Wolf says:

    That’s supposed to be “mighty suns”. 9_9

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