As I heard the message this morning, it didn’t really capture me immediately: An interstellar asteroid that passed through our solar system. It was first detected Oct. 19 by the telescope at the University of Hawaii and is going to visit our solar system until January 2019.
The asteroid was named ‘Oumuamua, which is the hawaiian word for “messenger from afar arriving first”. It is a visitor originated outside our solar system and will leave into the interstellar space again after traveling beyond Saturn.
NASA stated that “the object passed Mars’s orbit around Nov. 1 and will pass Jupiter’s orbit in May of 2018. It will travel beyond Saturn’s orbit in January 2019”
But why is this particular object so special?
Well, at first, it has an unusual shape. “It seems to be at least ten times longer than it is wide,” explained Alan Fitzsimmons from the Astrophysics Research Center at the Queen’s University Belfast in the latest broadcast of the BBC Science Hour.
The shape was modeled by the different light incidents as it spins around its own axis. The lightcurve, as the first scientific description published Nov. 20 states, “indicates its rotation period is ~7.34±0.06 hours”. Which translates into “it spins on its axis every 7.3 hours,” as NASA wrote.
“The highly elongated shape of ‘Oumuamua implied by its large lightcurve range is very unusual,” state the researchers in their article. They predict, the interstellar asteroid is shaped like a giant cigar, presumably 400 to 800 meters end to end.
While rumors occurred, the object might be an alien spacecraft due to its rocket-like shape, Fitzsimmons doubts this. “When we look at the color of the surface it looks like an object we’ll expect to appear if it was natural. It does not look like metal,” or any other processed material some technology would have made.
Furthermore, the object doesn’t move like a spacecraft. “It’s just following the force of gravity,” explained Fitzsimmons. “It’s not slowing down or speeding up beyond that.” And it does not rotate as fast as a spacecraft would.
The other remarkable conclusion is that the object might come from a solar system that is approximately 200 to 250 light years away. “There is a region of star formation, where interstellar clouds of gas and dust are collapsing at this moment to form new stars and planets,” said Fitzsimmons.
When planets are newly forming around a sun, as our planetary system did 4.5 billion years ago, they eject a huge amount of objects – like ‘Oumuamua – into the galaxy.
With an estimated travel speed of 196,000 miles per hour (or 87.3 kilometers per second) this means, the asteroid might be traveling through the space for at least 40 million years, before it reached our solar system. But, as Fitzsimmons said, there is no evidence that the asteroid really came from this specific region. “It could have been out there for an awful lot longer”, he said.
As this seems to be not much, we have to keep in mind that “even in the world’s best telescopes, this thing only appears as a dot of light”, explained Fitzsimmons. Taking this into account, it is really remarkable, how much the scientists were able to search out so far about this first messenger from the galaxy.