For the first time in history, scientists have detected the first interstellar object ever observed.
In October 2017, an elongated interstellar object named "Oumuamua" — the first to enter the solar system — was detected by a survey telescope in Hawaii. A new study published this week in the Astronomical Journal, coauthored by scientists at NASA's Jet Propulsion Laboratory, uncovered new information that suggested there was a limit to how big Oumuamua actually is, and gave astronomers a better indication of its size.
Scientists have been looking for signs of extraterrestrial life for decades. So does the appearance of Oumuamua mean the elusive "E.T" has finally been detected? Perhaps: Experts say it is exceedingly unlikely, but the possibility can't be ruled out just yet.
"I personally think the odds are much better that is something natural, but I don't want to dismiss the possibility that it could be from an alien civilization. But we have to have an open mind," Michael Wall, a writer at Space.com and a biologist, told CNBC recently.
Scientists believe Oumuamua is shaped like a cigar, approximately 400 feet long and 40 feet wide. However, they are only able to guess based on its changing brightness as it spins.
But scientists' biggest unanswered question is the object's thickness. As far as the scientific community is aware, there is no naturally occurring object that is as big as Oumuamua that appears so thin at the same time, increasing the likelihood that it was created by another life form.
Given the speed the object is moving, experts believe that it may be a light sail — an object that is thin enough to be pushed by the sun or another star, almost like a plastic bag in the wind, according to Matija Cuk, a research scientist at the Search for Extraterrestrial Intelligence (SETI) Institute.
Seth Shostak, a SETI research fellow, told CNBC that for that to be true, Oumuamua would have to be about a millimeter thick—about as thick as 5-10 sheets of paper stacked together.
According to Wall, scientists originally hypothesized that Oumuamua was a comet or an asteroid. However, both theories were ruled out: Unlike comets studied here on earth, this object does not have a tail, nor jets of gas that a comet would normally emit.
If Oumuamua is not a comet or an asteroid, chances of it being a light sail increase. According to SETI's Cuk, it is possible that outside our solar system, composition of space objects are different.
"Maybe in other solar systems comets could be made differently," Cuk said. That suggests the object could be naturally occurring, despite the fact that nothing like it has ever been seen anywhere near earth before.
Shostak said there are likely many objects similar to Oumuamua in the depths of space. This time, the object "hit the bullseye" by reaching the earth's solar system.
"This implies a number of these things are drifting through the cosmos, as ubiquitous as fire hydrants," Shostak said.
These objects have also likely reached our solar system in the past and gone unnoticed. Scientists are building another telescope similar to the one in Hawaii that detected Oumuamua. Once it is completed in Chile, it will be used to search for similar objects.
"Unless a miracle has occurred, these are entering our solar system all the time. This is just the first one we've found," Shostak said. He acknowledged the alien hypothesis was plausible, adding that Oumuamua acted more like a rock than a spaceship.
"If they really wanted to target our solar system, they'd hang around longer and probably come closer to the earth," he said.
Scientists also would have been able to detect any sort of signal the object had if it were as advanced as a cell phone, Shostak said. That does not prove anything, but decreases the likelihood that it was deliberately sent.
Oumuamua is now drifting further away from our solar system. The longer the distance, the harder it will be for earthlings to study it. Yet as technology increases, scientists may discover more objects similar to Oumuamua, perhaps in the next three to ten years.
"If we don't keep finding them, this will be increasingly peculiar," Shostak said.
Correction: Oumuamua was first discovered in October 2017.