Are We Alone?
Last updated 10/30/2020 at 1:50pm
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 like 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 world there are living creatures and plants and other living things we see in this world."
But it wasn't until 25 years ago – on Oct. 6, 1995 – that Swiss astronomers Michel Mayor and Didier Queloz made an announcement that rocked the astronomical community – enough to earn them the 2019 Nobel Prize in physics.
They reported that the sunlike star 51 Pegasi, some 50.9 light-years away, appeared to be wobbling as if a planet were orbiting nearby and tugging gravitationally on it. Originally named 51 Pegasi b, this world is now known as Dimidium, the Latin word for "half," because it is believed to contain about half the mass of Jupiter.
Astronomers calculated that this alien world orbits its parent star in only 4.2 days and that it endures a temperature of some 1,800 degrees F (992 degrees C). While a few worlds had already been reported to be circling pulsars –and even a few technical glitches masquerading as planets – astronomers often cite this as the first detection of an extrasolar planet of an ordinary star.
Since that historic day, astronomers have found 4,356 such extrasolar planets in 3,220 systems. But 51 Pegasi (affectionately known to astronomers as 51 Peg) will always be special because it was our first. Not only that, but 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, 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 its planet, though; that's a feat reserved for today's most sophisticated telescopes.
Whether 51 Peg b – or any other extrasolar 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 possible answers: yes or no.
And either is staggering in its implications!