70 Falmouth Street Portland, Maine 04103
43.6667° N 70.2667° W
Altitude: 10 feet below sea level
Founded January 1970
Julian Date: 245914.16
2019-2020: CXI
"Heavens below!"
THE DAILY ASTRONOMER
Thursday, March 5, 2020
Star Crossed
We know that astronomy can be frightening. After all, through astronomy we have learned that we're all amalgams of stardust that somehow evolved the capacity for self-reflection. Moreover, while the molecules comprising everything percolated through the bubbling mud, gushing floods and smouldering lava, the Universe beyond expanded to immense proportions. All the while, myriad stars and their attendant planets coalesced out of the gases so that now trillions upon trillions of stars and planets populate the cosmos. Add to that immensity the now serious notion of other Universes and one can feel vanishingly small in a space-time system that stretches ad infinitum in all directions. It is little wonder that astronomy can be terribly sleep disturbing.
So, whenever someone tells us that an astronomical concept has caused them fear, we feel compelled to alleviate the anxiety the concept aroused. The other day a young couple told me that their seven year old daughter was worried about the Sun "running into another star and causing a big explosion." You see, some planetarium jerk had just told her and her fellow audience members that the galaxy contains billions of stars. This young lady, being very thoughtful and logical, assumed that the Sun was moving through a teeming mass of stars like a commuter on a crowded subway.
Well.
The Sun is moving through the Milky Way Galaxy at quite the impressive speed of 143 miles per second. Also, according to recent estimates, the Milky Way Galaxy does contain more than one hundred billion stars. A star speeding quickly through such a star-rich galaxy would seem to be careening inexorably toward a stellar collision. It isn't.
The closest star system to the Sun, Alpha Centauri, is 4.4 light years away, a distance almost equal to 25 trillion miles. By scale, if the Sun were a softball in Portland, Maine, Alpha Centauri would be two softballs and a small apple in Florida. (Alpha Centauri is a triple star system with its red dwarf, Proxima Centauri closest to us.) By this scale model, one can see how infrequent any stellar collisions would be here in the Milky Way's spiral arms where the stellar density is 0.004 stars per cubic light year. Stellar collisions are more frequent in more dense regions around the nucleus and in globular clusters. However, the Sun isn't about to venture toward such areas.
Astronomers have looked into the question of eventual Sun-star encounters. Their research should do much to calm your nerves. According to current models, the dwarf star Gliese 710 will come within 1.5 light years of the Sun in about 1.4 million years. It is currently 63 light years away, but moving toward us at 15 kilometers per second.
Of all the worries that life has to offer, we can be well assured that our Sun will not collide with any other star...at least not for the foreseeable future and most likely, never. Sometimes astronomy can be a comfort, as well.
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