Are We Alone?

By Dennis Mammana

October 5, 2017 4 min read

Week of October 8-14, 2017

Who among us has never gazed into a starry night sky and wondered, "Are we alone in the universe?" With the hundreds of billions of stars in just our own Milky Way galaxy — many similar to our own sun — is it not possible that, orbiting nearby, there are planets and, at least on some of them, life?

You may be surprised to learn that these are not questions conjured up by modern astronomers. In fact, they've been debated and studied for millennia. In a letter to Herodotus, the ancient Greek philosopher Epicurus wrote: "There are infinite worlds both like and unlike this world of ours. ... We must believe that in all worlds there are living creatures and plants and other living things we see in this world."

But it wasn't until 22 years ago — on Oct. 6, 1995 — that Swiss astronomers Michel Mayor and Didier Queloz made an announcement that rocked the astronomical community.

They reported that a sun-like star some 50.9 light years away, appeared to be wobbling as if a planet were orbiting nearby and tugging gravitationally on it. Officially named 51 Pegasi b, this world received the unofficial name of "Bellerophon" after the Greek hero who tamed Pegasus, the mythological winged horse.

They calculated that this alien world must have about half the mass of Jupiter, that it orbits its parent star in only 4.2 days, and that it endures a temperature of some 2,200 F. While a few worlds had already been reported to be circling pulsars, astronomers often cite this as the first detection of an extrasolar planet of an ordinary star.

Since that historic day, astronomers have found 3,667 such extrasolar planets in 2,747 systems — many (616) multiple-planet systems — and the spaceborne Kepler Telescope has located nearly 4,496 additional candidates. But 51 Pegasi, more affectionately known to astronomers as 51 Peg, will always be special, since it was our first. Not only that: It's a star that backyard stargazers can see easily from Earth.

This week, go outdoors after dark and look midway up in the eastern sky. There you should spot the four stars making up what astronomers know as the Great Square of Pegasus. With the accompanying map in hand, identify its shape and some of the stars that make it up.

If your sky is dark and relatively free from light pollution, try to spot 51 Peg. It's located almost midway between the two westernmost stars of the square, and slightly west of the line connecting them.

It's a faint star, barely visible to the naked eye, but you should have little trouble spotting it with binoculars. Don't expect to see actual planets, though; that's a feat beyond even today's most sophisticated telescopes.

Whether the 51 Peg — or any other extra-solar world — supports life is anyone's guess. What is clear, though, is that the number of planets where life might exist is growing every day, and the chemistry for life as we know it is found everywhere we look in the universe.

As profound as the question "Are we alone?" is, there are only two answers: Yes or no.

And either is staggering in its implications!

 In 1995, Swiss astronomers discovered 51 Pegasi b, an extrasolar planet.
In 1995, Swiss astronomers discovered 51 Pegasi b, an extrasolar planet.

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