This article has been updated.
Our solar system has a visitor. It's cylindrical, dark and reddish, a quarter-mile long. The object won't be staying. This fall, astronomers announced that the thing came blazing into our neck of the galaxy at speeds of up to 196,000 mph. It is now headed away as quickly as it came.
The object's trajectory is so strange and its speeds are so blistering that it probably did not originate from within our solar system. Its discoverers concluded that the object is a rare interstellar traveler from beyond our solar system, the first object of its kind observed by humans.
Astronomers at the University of Hawaii, who discovered the object with the Pan-STARRS 1 telescope, said the visitor was an asteroid. In October, they named the asteroid 'Oumuamua — Hawaiian for “messenger.” 'Oumuamua, which appears rocky or metallic, lacks the characteristics of a comet.
Some scientists, though they are swift to say 'Oumuamua is probably natural, have not yet ruled out more extraordinary origins. “The possibility that this object is, in fact, an artificial object — that it is a spaceship, essentially — is a remote possibility,” Andrew Siemion, director of the Berkeley Search for Extraterrestrial Intelligence Research Center, told The Washington Post on Monday.
Siemion is a member of the Breakthrough Listen initiative: a $100 million project, backed by Russian billionaire Yuri Milner, to hunt for extraterrestrial intelligence. This week, researchers with the Breakthrough Listen initiative announced that a radio telescope will probe 'Oumuamua for signs of technology. The telescope, nestled within the hills of the Green Bank Observatory in West Virginia, began its search Wednesday. The first round of radio observations, the team reported Thursday, detected no strange signals, but they’ll keep listening.
“We don’t see anything continuously emitting from 'Oumuamua,” Siemion said. He said the team is “quite keen” to examine observations in the 1 to 2 gigahertz frequencies to look for molecules associated with water.
“A slew of optical telescopes are continuing to look at 'Oumuamua,” he said, “and I suspect we will learn more about its size, shape and composition in coming days and weeks.” (The Breakthrough Listen probe of 'Oumuamua will record a whopping petabyte of raw data.) Siemion and his colleagues plan to submit a journal article in December describing the interstellar body.
'Oumuamua behaves oddly. Planets and asteroids circle the sun on the same plane, like water swirling around a basin. 'Oumuamua dipped into the solar system from outside the plane, as if leaked from a cosmic faucet.
It is shaped strangely, too. Most asteroids of this size are spherical. This object has the proportions of a giant cucumber. In fact, Harvard University astronomer Avi Loeb recently told Milner that 'Oumuamua has the optimal design of a vessel meant to travel through space, the Atlantic reported.
Yet all of its features are “entirely consistent with being a natural object,” said Karen Meech, the University of Hawaii astronomer who led the research team to measure 'Oumuamua's physical properties. “That being said, we cannot disprove the unlikely hypothesis that it is not.”
Astronomers across the planet have turned their sensors at the object. The European Southern Observatory followed up on the initial Hawaiian detection from Chile, peering at 'Oumuamua through the Very Large Telescope in Chile.
Though the most likely explanation for 'Oumuamua is that it's lifeless rock, scientists aren't about to let it breeze by without scrutiny. That's why they are using Green Bank. Over the past 18 months, SETI astronomers have installed detectors at the telescope to look for signs of electromagnetic activity in space. If an electronic device no more powerful than a WiFi router or telephone handset is transmitting on 'Oumuamua, the telescope will be able to sense it.
“Green Bank is the most capable radio telescope in the world for conducting these types of observations,” Siemion said.
“This is the sort of opportunity that one would hate to miss, even if the chances are extremely low for success,” Meech said. SETI researchers typically measure the distance to curious objects in light-years. 'Oumuamua is still within light-minutes of Earth.
“If you don't try the experiment,” she added, “you will never know.”