Is the interstellar object known as “‘Oumuamua” a sign of extraterrestrial life? Avi Loeb, chair of Harvard’s Astronomy Department, isn’t surprised that his idea has drawn skepticism. All the same, he notes, progress begins with an open mind.
“This is how science works,” said Loeb. “We make a conjecture … and if someone else advances another explanation, we will compare notes and the next time we see an object of this type we will hopefully be able to tell the difference. That’s the process by which science makes progress.”
Loeb, also the Frank B. Baird Jr. Professor of Science, collaborated with postdoctoral fellow Shmuel Bialy on a paper suggesting that ‘Oumuamua may be a lightsail created by an alien civilization.
“When I first heard about ‘Oumuamua, this idea was in the back of my mind,” Loeb said. “So I approached Shmuel and said, ‘Let’s see whether sunlight can push this’ … because there was nothing else I could think of which could account for our observations, because this object is weird. So, my approach was to follow the maxim of Sherlock Homes — ‘When you have excluded the impossible, whatever remains, however improbable, must be the truth.’”
An alternative to traditional rocket propulsion, lightsails are propelled by radiation from the sun or from lasers. Calculations by Loeb and Bialy show that for solar radiation to push ‘Oumuamua, it must have an unusual geometry — tens of meters in size, but less than a millimeter thick.
In their paper, published this month in The Astrophysical Journal Letters, Loeb and Bialy advanced two possibilities for the object’s origins — that it is debris from a now-defunct craft tumbling through the galaxy, or that it was launched as a sort of reconnaissance probe from elsewhere in the galaxy.
While he acknowledged that other astronomers — including the researcher who discovered ‘Oumuamua — have dismissed those ideas, Loeb said such debates are an important part of the scientific process. And while alien life may once have been strictly science fiction, Loeb pointed to a growing body of evidence suggesting we’re not alone.
“We know a quarter of all the stars in the galaxy have planets in the habitable zone of their host star … so to me it’s not impossible that there may be life elsewhere,” he said.