The Mysterious Interstellar Object: A Possible Alien Craft?
Earlier this month, astronomers observed a strange interstellar object passing through the solar system. This object, named 3I/ATLAS, is approximately 12 miles (20 kilometers) long and has traveled from another star, taking billions of years to reach our sun. However, a prominent physicist believes that this object could be an alien spacecraft.
Professor Avi Loeb, a theoretical physicist and cosmologist from Harvard University, argues that 3I/ATLAS is too large to be natural. Experts suggest it might be either an exceptionally large solid mass or a smaller comet with a bright envelope of gas and dust. If it isn’t a comet, Professor Loeb says the chances of it naturally reaching our sun are incredibly low.
He states, “It is difficult to imagine a natural process that would favor a plunge towards the inner solar system at 60 kilometers per second. An alternative is that the object targets the inner solar system by some technological design.”
Discovery and Orbit
3I/ATLAS was first detected by NASA’s Asteroid Terrestrial-impact Last Alert System on July 1. After tracing its orbital path, scientists realized that its extremely elliptical orbit and high speed indicated that it originated outside the solar system. This makes it only the third interstellar object humanity has detected, following ‘Oumuamua in 2017 and Borisov in 2019.
The object arrived from the direction of the constellation Sagittarius and is currently heading towards the inner solar system at 135,000 miles per hour. NASA predicts that it will reach its closest point to the sun on October 30, at a distance of 130 million miles (210 million km), which is just within the orbit of Mars.
Thankfully, the object poses no threat to Earth and will pass harmlessly at around 150 million miles (240 million km) away at its closest point. Since it is currently about 300 million miles (490 million km) from Earth, astronomers can’t directly measure its size. Instead, they estimate its size based on how much light it reflects.
If it is a solid object like an asteroid, which reflects about five percent of the light that hits it, then 3I/ATLAS must be between 12 and 14 miles (20-24 km) in diameter. That makes it up to 200 times larger than the 100-meter-long and extremely thin ‘Oumuamua.
Unusual Size and Implications
Professor Loeb points out that this fact immediately raised his suspicions since large objects are typically much rarer than smaller ones. He questions, “How many objects on the scale of ‘Oumuamua are there for each object that is 24 kilometers in size?” The answer is about a million. But we haven’t seen a million ‘Oumuamua-sized interstellar objects before seeing this one, which is very strange.
In a paper accepted for publication by the Research Notes of the AAS, Professor Loeb explored what it would take for an object of 3I/ATLAS’ size to reach Earth. Based on how often we see objects of this size, previous research calculated how many 12-mile-long objects could exist in the Milky Way. When he multiplied this number by the mass of 3I/ATLAS, the result didn’t make sense.
“This ends up being a quarter of the mass of the stars in the Milky Way,” says Professor Loeb. “But because only two percent of the mass in stars is in heavy elements that make rocks, you don’t have the mass to make enough rocks of this size.”
This implies that 3I/ATLAS is much rarer than its appearance in our Solar System suggests. Professor Loeb argues that objects this big are too rare for their appearance in the inner solar system to be random. He states, “It’s not like these objects are floating around in all directions; this object was aiming to get to the inner solar system. The question is: Why was it sent in the direction of the inner solar system?”
Alternative Explanations
While Professor Loeb suggests the possibility of an alien spacecraft, the alternative explanation is that 3I/ATLAS is much smaller and more reflective than any asteroid. This would be possible if the interstellar object is a comet, a ball of ice and dust moving quickly through space.
If it were a comet, the heat from the sun would evaporate a layer of ice and dust, reflecting back a lot of light. This would explain why 3I/ATLAS appears so bright while maintaining that its core is small enough to be natural.
Most astronomers and space agencies accept this as the likely explanation, labeling the object an “interstellar comet.” While Professor Loeb considers this the “simplest and most likely” solution, he doesn’t think the evidence for the comet theory is conclusive.
For example, he points to observations by the European Southern Observatory (ESO) Very Large Telescope (VLT). The VLT did not find direct evidence of dust or gas being released by the object but concluded it was a comet based on surface “reddening” caused by dust. Professor Loeb maintains that this could simply be due to the red surface.
Likewise, observations showing the fuzzy streak of the comet’s gas layer could be an artifact of the long exposure images and 3I/ATLAS’ high speed. This doesn’t mean that 3I/ATLAS isn’t a comet, but Professor Loeb believes it’s still too early to rule out the possibility that it is a solid object.
“The good news is that it will come closer to the sun and it will get heated up by sunlight,” says Professor Loeb. “The more it is heated, the more mass it would shed if it were a comet, and the easier it will be for us to tell what this object is.”
