Bob on Sesame Street taught us to know the people in our neighborhood.
(Song starts at 0:50)
But Sheldon in The Big Bang Theory taught us to know the stars in our neighborhood, too.
Our stellar neighborhood is a bit larger than your own neighborhood. As we discussed before, the nearest star to our own solar system is Proxima Centauri. Suppose you lived in a typical suburban house with a 50 foot driveway. If your driveway were like the distance from the Earth to the Sun, then Proxima Centauri would be about 2500 miles away. Even survivalists can’t get this far from their neighbors.
When the writers asked me to find the names of the stars, in order of proximity to us, I figured that would be easy. But it was a case where the internet fails. Nearly all the lists on the web are in disagreement with each other. And the writers needed an answer…fast.
Luckily one of my friends at UCLA, a professor over on the Astronomy floor bailed me out. He told me about RECONS, the Research Consortium on Nearby Stars. They maintain a definitive list on the stars in our neighborhood. (And for the record, Wikipedia had it right.)
So we heard the list from Sheldon. Special thanks to none other than “The Bad Astronomer” for helping out with the pronunciation of the star names.
(Of course the closest star to Sheldon is not Proxima Centauri at all. It is Sol, our own Sun. If you were thinking that during Sheldon’s song, good for you! You may stay after class and clean the erasers.)
What about those crazy names? These stars were discovered over thousands of years. Some are visible to the naked eye. “Sirius”, the brightest of the stars, was named by the Ancient Greeks after their word for scorcher. Others are named for the constellation they are in. “Alpha Centari A” is the brightest of the stars making up the constellation Centaurus. “Epsilon Eridani”, named after the constellation Eridanus and the fifth greek letter, is the fifth brightest star in that constellation. But closest need not mean the brightest. Many of these nearby stars were not discovered until modern times and are named after their discoverers: Jérôme Lalande discovered “Lalande 21185” in 1801 and “Ross 154” was only found in 1925.
And to this day, astronomers still are finding nearby stars. Teegarden’s star was missed until 2003. It is so close that it moves across our sky faster than almost any other star. Surveys find nearby stars because over the years their position on the sky can change slightly, just thousandths of a degree per year. But Teegarden’s star, a modest little red dwarf, moved so fast across the sky, it was always overlooked. It is humbling to think that the 23rd closest star closest to our own solar system was missed until this very decade. And there may be more…
Some of the stars are close together: Proxima Centauri and Alpha Centauri are a pair, forming a binary star system. So are Sirius A and B. About half the stars closest to us are pair-bonded. Our star appears to be alone. Or is it? Some people have proposed we have a distant and dim partner, called Nemesis. So-named because when its orbit brings it back close to Earth, its gravity would disrupt the comets and asteroids causing them to rain down on us. It has been proposed to explain a possible periodicity, about 27 million years, of mass extinctions found by paleontologists. The periodicity of these extinctions is not universally accepted. And the explanation of periodic extinctions being induced by a companion star even less so. Nevertheless, I named the first electronics board I build as a graduate student “Nemesis”.
If there is such a “Nemesis” star orbiting our own, a new survey will find it. The WISE satellite, the Wide-Field Infrared Survey Explorer (led by my same friend at UCLA) is looking. Infrared light is redder than the reddest light you can see. Really hot objects, thousands of degrees, glow in the visible light such as a lightbulb filament or the Sun. The reason you can see your friends’ faces it that visible light reflects off of their faces to your eyes. But if you had infrared eyes, your friends, cooler than the Sun but still hot, would glow but in the infrared. (Compared to absolute zero, all your friends are “hot”. Compared to the Sun, they are “cool”. Feel free to compliment them on this.) So infrared is the go-to color for astronomers to find small, cool, faint stars, that might have been missed by all astronomers until now.
Such dim stars could have their own planets orbiting them, and if close enough, could sustain life, maybe even intelligent life. There may even be one closer than Proxima Centauri. When I mentioned that to one of the co-creators and writers of the Big Bang Theory- when he was visiting UCLA to give the Physics and Astronomy Department commencement address — he told me, “The Federation may be sooner than we think.”
Update: Since the time this espisode aired, the measurements of the distances to the Procyon stellar system and 61 Cygni system have changed slightly, so their order according to RECONS is now different than the order in the song. Thanks to eagle-eared viewer Åingeal S. for asking me why they were “wrong” which allowed me to locate the difference using the internet archive of the RECONS webpage.