Two months ago, right on time for the holidays, we received an unexpected visitor from far away. By we I refer to “earthlings” and “far away” means hailing from another stellar system somewhere in the Milky Way galaxy.
Our guest was an interstellar asteroid. Immediately after its initial discovery in October by a University of Hawaii telescope, astronomers around the world went into action. Urgency for viewing from ground-based telescopes was vital to get the best data on the object’s orbit, brightness and color.
“For decades we’ve theorized that such interstellar objects are out there, and now – for the first time – we have direct evidence they exist,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate in Washington, D.C. “This history-making discovery is opening a new window to study formation of solar systems beyond our own.” (NASA released a three-minute video about this discovery.) The asteroid was named ‘Oumuamua’ (pronounced oh MOO-uh MOO-uh), Hawaiian for “a messenger from afar arriving first.”
What astronomers learned turned out to be very strange indeed. As reported in the journal Nature, the object is an asteroid that has been sailing through the Milky Way, unattached to any star system, for hundreds of millions of years before its chance encounter with our star system. Preliminary orbital calculations suggest that the object came from the direction of the bright star Vega, in the northern constellation of Lyra. However, it took so long for the interstellar object to make the journey that Vega was not near that position when the asteroid was there about 300,000 years ago.
A surprise discovery was the object’s cigar-like shape. It is about a quarter mile long with a length ten times greater than its width. That aspect ratio is greater than that of any asteroid or comet observed in our solar system. Every 7.3 hours it revolves on its axis, like a baton twirled in a majorette’s hand. Scientists think it’s made of rock and metals, and that its reddish surface is due to irradiation from cosmic rays over hundreds of millions of years.
As earth’s 2017 winter holidays ended, Oumuamua didn’t stick around. It hightailed it at some 85,700 miles per hour. The closest it got to your and my home was 19 million miles. In May it will pass Jupiter’s orbit and this time next year it will be on the far side of Saturn’s orbit, thence to depart our solar system. Pegasus will be the next star system it visits.
Reflecting on phenomena such as Oumuamua invites a sense of the sublime, a word rare today but familiar to every poet and philosopher in the 18th and 19th centuries. (Terence Malick offered a magnificent visual expression of the celestial sublime in a two-minute segment of his 2011 film “The Tree of Life.” )
I’m not sure this rises to the level of Zen paradox but an awareness of my own insignificance – infinitesimal body size relative to the vastness of the cosmos plus the eye-blink of time I have been allocated – can fill me with wonder and gratitude. My thoughts get pulled in a religious direction. How nice to have a mind to ponder this and a soul that can sense the sublime.
Earth to Oumuamua: Please give Pegasus and whatever else you happen to find out there our humble planet’s regards.
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