Astronomers get another chance to study an alien visitor
Long time readers of this column will remember “Oumuamua”, which we last talked about back in January of this year. For those of you who aren’t familiar with Oumuamua, it’s the first object ever detected that we know came from outside of the solar system.
And if that isn’t crazy enough, there’s also some compelling evidence that it is actually an artificial object, maybe even an alien probe or solar sail.
(See my January 2019 and December 2017 columns for more info—they are both archived here on The Pulse website.)
Well, Oumuamua’s detection back in 2017 got folks watching the skies for other interstellar visitors. Lo and behold, just last month, another one was spotted! This time around, it was discovered on Aug. 30, 2019, by Gennady Borisov at the MARGO observatory in Nauchnij, Crimea.
The object, which currently has the designation “C/2019 Q4 (Borisov)”, is currently thought to be a comet. That’s because, unlike Oumuamua, it’s already showing signs of a “tail”. (Oumuamua never developed a tail or other cometary characteristics. This was one of several things that caused speculation it might be artificial in origin.)
Okay. So, it’s a comet. But, how do we know it’s not just another comet knocked loose from the Oort Cloud at the edge of the solar system? Well, there are a couple of clues:
First of all, it’s coming in from way above the plane of the ecliptic. That’s the plane in which most items in our solar system orbit the Sun. You can think of it this way: If the Solar System was a plate, the Sun would sit at the center, and most of the other the planets would sit on the plate at different distances from the center. Most comets approach the Sun from just a tiny bit above or below the orbits of the planets. This object is coming in as if it had been thrown at the plate from above.
And when I say “thrown”, I mean it. This bad boy is moving fast: 93,000mph. (That’s 150,000kph for those of you reading this in a country that isn’t the USA.) If that still doesn’t seem fast, that’s almost 29 miles per second. Or, to put it in a way that all Chattanoogans can understand: Q4 would go from Chattanooga to Atlanta in about four seconds.
When it actually passes through the Solar System in October, it will be out past the orbit of Mars. Out there, the escape velocity for the Sun is relatively low, so, once it passes through the ecliptic, it’s not coming back. (The Sun’s gravity will certainly bend its path a little, but nowhere near enough to capture it.)
Oh, and if you’re worried about it hitting the Earth and killing us all, don’t be. As I mentioned, it’s going to be crossing through the Solar System out past the orbit of Mars. It will also be on the opposite side of the Sun from us, so, no worries there.
Unlike Oumuamua, Q4 was detected on its way towards the Solar System. That means that astronomers are going to have plenty of time to study it both coming and going. Oumuamua was spotted as it was moving away from the Sun and is already incredibly faint.
Q4 will actually be visible to amateur astronomers later this year, and still visible to large telescopes for months after that.
Better still, since it seems to be off-gassing (that’s what a comet’s tail is), we’ll actually be able to take spectra of it and see what it’s made of! By comparison, Oumuamua had no tail and was a very dark object, so, we really aren’t sure what it was made of.
So…wow! Two interstellar objects found just a couple of years apart. It’s truly an amazing time to be an astronomer. I can’t wait to see what we learn from these strange visitors.
Steven W. Disbrow is the proprietor of “Improv Chattanooga” on the South Side of town. He also creates e-commerce systems and reads comic books when he’s not on stage acting like a fool.