Looks as if we get to welcome yet another interstellar visitor to our solar system this fall — the second one in two years, by my count.
Before you call the Men in Black or Area 51, rest assured this is just another bit of space debris from some other star system, briefly hurtling through the inner solar system, never to return.
The first one, `Oumuamua, was discovered in October of 2017 by Robert Weryk using the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) located at Hawaii’s Haleakala Observatory. The object’s name means “messenger from afar who arrives first.” Some have shortened that to “scout,” which has certain military connotations. Google translates it as “firstborn.”
The 400-yard-long, reddish-brown asteroid discovered speeding through our solar system at 200,000 mph is clearly alien, moving too fast to be bound to the sun’s gravity. It is 10 times longer than it is wide, inciting one researcher to refer to it as “a cigar from another star.” Researchers have compared it with Arthur C. Clarke’s Rama interstellar spaceship, so much so that during its passage, they checked for signs of radio signals.
That it was tumbling end-over-end every 7.3 hours should put any alien rumors to rest, or the crew on board is having a really bad time of it.
After the global effort to chase this object for observations, how can we learn so much from a single point of light whizzing through our solar system? We can measure its speed, how far away it is and possibly learn where it originated. We know its size, shape and can estimate its mass. How is that even possible?
That little point of light reveals a lot. We can measure how bright it appears and then use the work of the Johannes Kepler, the 16th century astronomer, to find the object’s orbit and determine how bright it really is. Observations in different telescopic filters can tell us about color and size. Watching it vary in brightness tells us the dimensions as it spins through space, and so on.
I once spent a summer measuring the rotation periods of asteroids. Each evening, we’d choose 10 or so likely targets. Slewing the telescope from one to the other, we’d expose images for a few minutes at a time. We followed each image with calibrations to make sure the instrument was performing well and to correct for sources of noise due to temperature and fluctuations in the electronics. Later the next day, we’d measure the light from the images of each target, comparing to a reference star to ensure consistency, and plot the results. We could analyze these “light curves” for periodic variations and measure the rotation rate.
It took us all summer to get the rotation periods of 10 objects. Ten out of the millions or so asteroids in the solar system.
The way asteroids rotate tells us about their past interactions and their formation mechanisms. They are hints to the origin story of our solar system.
And in the case of `Oumuamua, a tantalizing and bizarre clue to the formation of another.
On Aug. 30, 2019, Crimean amateur astronomer Gennady Borisov spotted another one of these interstellar wanderers, only the second one to be discovered. He did so using a 0.65 meter telescope he built himself. His discovery was followed up by a handful of dedicated observers who determined, from the object’s orbit, that it was moving far too quickly to be gravitationally bound to the Sun.
The word “amateur” often gets confused with “novice,” but observers like Borisov are anything but. I think of them more like Olympic athletes: The most skilled of their field, at the top of their game. They just don’t get paid.
Come to think of it, Kepler made his living doing astrological readings for Emperor Rudolf II, not astronomy per se. I suppose, he was actually an amateur as well.
Textbook appendices are filled with bits of information — masses of planets, temperatures of stars, distances to galaxies — discovered by thousands upon thousands of people dedicating their lives just to add that small piece of knowledge to the whole.
Some of these data are collected at major observatories by professional astronomers. Some are measured by students studying to become professionals themselves.
A great many are measured by dedicated astronomers who have yet to quit their day jobs. Thus, we amass knowledge one tiny point of light at a time.