Investigating spiral galaxies

Seth Jarvis

I read lots of blogs on an occasional basis, but only a few blogs every day.  One of my “read it every day” blogs is “BadAstronomy” by Dr. Phil Plait.

BadAstronomy is well written, highly educational, thought provoking, and always a lot of fun.

Recently, BadAstronomy featured this amazing photograph (below) of the “Leo Triplet,” a lovely trio of galaxies located 35 million light-years from us in the direction of the constellation (can you guess?) Leo (the Lion).

The Leo Triplet.  Lovely, but it's what's in between them that I care about.

The Leo Triplet. Lovely, but it's what's in between them that I care about.

The image features three spiral galaxies, each about the size of our Milky Way galaxy, each containing roughly 100 billion stars, and each gravitationally bound to one another.

The galaxy on the far left of the image is seen edge-on, the galaxy in the upper right is seen at an oblique angle, and the galaxy on the lower-right is seen nearly face-on.

The European Southern Observatory, which took this image, has a nifty little animation of where these galaxies are when seen through the foreground stars of Leo.

You should absolutely read what Phil has to say on the subject, but to me what is fascinating about this image is everything in the image that is not those three lovely galaxies.

One of the regular features of BadAstronomy is that images Phil puts on his blog link to full-sized images of whatever it is that day’s post is about.

Because Phil thoughtfully provides links to the frequently enormous original image files, and because I am a nerd of the highest order, I dutifully download and inspect the huge image de jour in anticipation of seeing some fascinating detail that will inspire, delight, and put fresh wrinkles on my forehead.  This image of the Leo Triplet does not disappoint in any of those dimensions.

Do you know what an inspection of the original, huge image contains?  About a bazillion other galaxies.

Below are a few sections of the original Leo Triplet image, but focused on the otherwise “empty” sections of the image and blown up to see what galactic critters may be hiding in the background.

Can you spot the galaxies? They’re the little fuzzy, oblong shapes, brighter in their centers than at their edges.  They are anywhere from hundreds of millions to billions of light-years farther from us than the three main galaxies in the triplet.  These galaxies are way out there, and there are a lot of them.

Triplets #1

Triplets #2

Triplets #3

Triplets #4

Those are just a few – look at the large image for yourself and scroll around to see how many distant background galaxies you can count.  I stopped counting at a hundred.

And remember, if only one star in a million has a planet in orbit around it that is home to some kind of intelligent alien civilization, then in an image such as this one of the Leo Triplet, containing at least a hundred galaxies beyond the three main attractions, you’re seeing an image containing light from at least ten million other civilizations.

Then again, what if I’m wrong?  What if my estimate is too large by a factor of a thousand and that really it’s only one star in a billion that is home to some kind of E.T.?

Even if that’s the case then the image of the Leo Triplet is still an image within which you’re seeing the light from stars that are home to better than ten thousand civilizations.

And if you pointed that telescope in any other direction and took a similar image, even of “empty” space, you’d still get an image containing hundreds or thousands of other distant, yet-cataloged, yet-unnamed galaxies, each one having a statistically significant probability of being home to thousands upon thousands of other intelligent forms of life.

Do any of those E.T.’s have telescopes?  What do they think about when they look through their telescopes at our Milky Way?  To them, we would appear in our own little group of galaxies, dominated by us and our (relatively) nearby neighbor, the Andromeda Galaxy.  What a pretty picture they’d see of us!

That’s the kind of thing that keeps me staring into the ceiling late at night.

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2 thoughts on “Investigating spiral galaxies

  1. Well the truth is that if an alien individual was looking at me when the light left that galaxy, they are now gone for millions of years. In the same notion, when the light from the Sun or our Milky Way (most likely) reaches their galaxy, I will be long gone. What is perhaps equally amazing to me is to think of what happen to their civilization as it evolved and how did it end? What is the fate of our own species by the time the light reaches their galaxy?

  2. The author hit upon thoughts that many of us share with him. It is mind boggling to utter an understatement. We can’t deny the odds of other intelligent life elsewhere, supported by the fact so many exoplanets have been discovered recently with thousands more to come. Man, don’t you wish you had a time machine? But if I mass produced time machines, the first rule would be like a vase in a museum, “do not touch!”

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