Interloper Speeding Through Solar System Is Interstellar Comet, Not Alien Spacecraft

In early July, an observation made by a NASA-funded survey telescope in Chile sent the astrophysics community into a frenzy. The telescope, whose purpose is to search for objects that might collide with Earth, had discovered an intruder in our solar system – a stranger in our cosmic backyard, zipping along at speeds exceeding 210,000 km per hour (130,000 mph).

The initial consensus among astronomers was that the mystery object, named 3I/ATLAS after the Chilean telescope, was a comet from interstellar space, the third such object ever detected (3I standing for “3rd interstellar”). The evidence showed that its size was just a few km across and that it would not come closer than 270 million km (170 million miles) to Earth. But puzzling questions remained.

If the interloper was indeed a comet, why wasn’t it accompanied by the usual “tail,” the stream of gas and dust millions of km long stretching out behind a comet’s path? Why was it moving so fast, much faster than typical solar system comets? And why, contrary to most comets, was it traveling close to the so-called ecliptic, the orbital plane of Earth and most planets around the sun?

Enter famed Harvard astrophysicist Avi Loeb, recognized for his work on the evolution of the first stars. Rejecting the consensus, Loeb postulated that 3I/ATLAS could be an “extraterrestrial artifact” — maybe even an “alien mothership” on a reconnaissance mission through our solar system.

Loeb quickly submitted a preprint espousing his hypothesis, setting out his arguments for 3I/ATLAS being technological and possibly even hostile. One argument, put forward separately in a blog post of his, was that subsequent study of the extraterrestrial visitor by the Hubble space-based telescope suggested that it could now be producing its own light, as seen in the figure below.

The glow of light ahead of its motion had been interpreted by other astronomers as evaporation of dust from the sun-facing side of the object. But Loeb had a different interpretation: that 3I/ATLAS could be “a spacecraft powered by nuclear energy,” the dust emitted from its front surface being dirt that accumulated during its interstellar travel.

In his preprint, Loeb expounds his other arguments. Spectroscopic analysis has so far showed no sign of a cometary tail, essentially ruling out the comet hypothesis, he maintains. Furthermore, the interloper’s extremely high speed at its present large distance from the sun, which could give it a future gravitational “push,’’ means it cannot have come from the solar system. Most comets originate in the Kuiper Belt in the outer reaches of the solar system, but not beyond; 3I/ATLAS passed through the Kuiper Belt eight years ago, says Loeb.

As for its near alignment with the ecliptic plane, Loeb calculates that the probability of such a trajectory for an incoming object is a low 0.2%. In addition, the trajectory takes the unknown intruder unusually close to Venus, Mars and Jupiter, as indicated in the next figure, without coming too close to Earth. Assuming that 3I/ATLAS could have entered the solar system at any time, the probability of this trajectory is a vanishingly small 0.005%.

Loeb finds such estimates, together with other observations, suspicious. He speculates that the trajectory of 3I/ATLAS has all the hallmarks of an alien spacecraft dispatched to investigate the solar system while remaining beyond the range of our most powerful ballistic missiles.

Needless to say, other astrophysicists have found Loeb’s ideas outlandish – and for good reason.

On August 6, the awesome capabilities of the James Webb Space Telescope were brought to bear on the apparent trespasser, when the telescope’s near-infrared spectrograph was employed for a detailed study of the light emitted by the object. One of the many spectrograph images is displayed in the figure below, the arrow (S,v) denoting the direction of motion.   

The James Webb images show the light emitted by 3I/ATLAS much more clearly than the earlier pictures obtained by the Hubble telescope. The light pattern is in fact confirming evidence of the “coma” characteristic of a typical comet. A coma is the luminous halo of gas and dust that forms around the cometary nucleus as the comet approaches the sun; the coma appears as a diffuse “head” to the comet, the material eventually being swept into the comet’s tail.

What’s unusual about the coma of 3I/ATLAS is that it’s rich in CO₂ and has less water than most ordinary solar system comets. In another preprint, a research group headed by two NASA astrophysicists proposes that the comet contains ices exposed to higher levels of radiation than normal comets, accumulated as it traveled for probably billions of years through interstellar space, or that it formed close to the CO₂ ice line in another star system.

Even Loeb in his earlier preprint conceded that 3I/ATLAS was most likely a comet. He defended his paper as “largely a pedagogical exercise.”

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Are UFO Sightings a Threat to Science?

Credit: CoolCatGameStudio from Pixabay

Do UFO sightings threaten science? The short answer is that UFO observations don’t in themselves – as long as one separates true observations from the questionable claims of alien abduction and other supposed extraterrestrial activity on Earth.    

Unlike pseudosciences such as astrology or crystal healing, UFOs belong to the realm of science, even if we don’t know exactly what some of them are. Sightings of ethereal objects in the sky have been reported throughout recorded history, although there’s been a definite uptick since the advent of air travel in the 20th century. According to recently released records, UK wartime prime minister Winston Churchill colluded with General Dwight Eisenhower to suppress the alleged observation of a UFO by a British bomber crew toward the end of World War II, out of fear that reporting it would cause mass panic.

Since then, numerous incidents have been reported in countries across the globe, by scientists and nonscientists alike. The U.S. Air Force, which coined the term UFO, undertook a series of studies from 1947 to 1969 that included more than 12,000 claimed UFO sightings. The project concluded that the vast majority of sightings could be explained as misidentified conventional objects or natural phenomena, such as spy planes, helium balloons, clouds or meteors – or occasionally, hoaxes. Nonetheless, there was no explanation for 701 (about 6%) of the sightings investigated. 

Only in the last several months has the existence of a new U.S. program to study UFOs been disclosed, this time under the aegis of the Pentagon. Begun in 2007, the secret program apparently continues until this day, though its government funding ended in 2012. One of the few publicized incidents which was examined involved two Navy F/A-18F fighter pilots, who chased an oval object that appeared to be moving at impossibly high speeds for humans, off the coast of southern California in 2004.

Perhaps the most famous American event was the so-called Roswell incident in 1947, when an Air Force balloon designed for nuclear test monitoring crashed at a ranch near Roswell, New Mexico. The official but deceptive statement by the military that it was a high-altitude weather balloon only served to generate ever-escalating conspiracy theories about the crash. The theories postulated that the military had covered up the crash landing of an alien spacecraft, and that bodies of its extraterrestrial crew had been recovered and preserved. Over the years, details of the story became embellished to the point where more than one candidate for U.S. President promised to unlock the secret government files on Roswell.

Belief in alien activity is where UFO lore departs from science. While it’s possible that some of the small percentage of unexplained UFO sightings have been spaceships piloted by extraterrestrial beings, there’s currently no credible evidence that aliens actually exist, nor that they’ve ever visited planet Earth.

In particular, it’s belief in alien abductions that constitutes a threat to science, the hallmarks of which are empirical evidence and logic. In the U.S., the phenomenon began with the mysterious case of Betty and Barney Hill in 1961. The Hills claim to have encountered a UFO while driving home on an isolated rural road in New Hampshire, and to have been seized by humanoid figures with large eyes who took them onto their spaceship, where invasive experiments were performed on the terrified pair. Afterwards, both the Hills’ watches stopped working and they had no recollection of two hours of their bewildering drive.

Although the alien abduction narrative captured the American imagination during the next two decades, the Air Force ultimately dismissed the story and determined that the alien craft was a “natural” object. Indeed, there’s no reliable empirical evidence that any of the millions of other reported abductions have been real.  

Psychologists attribute the episodes to false memories and fantasies created by a human brain that we’re still struggling to understand. Possible physical causes of the abduction phenomenon include epilepsy, hallucinations and sleep paralysis, a condition in which a person is half-awake — conscious, though unable to move.

But while abduction stories may be entertaining, they qualify as irrational pseudoscience because they can’t be falsified. Pseudoscience is frequently based on faith in a belief, instead of scientific evidence, and makes vague and often grandiose claims that can’t be tested. One of the clear-cut ways to differentiate real science from pseudoscience is the falsifiability criterion formulated by 20th-century philosopher Sir Karl Popper: a genuine scientific theory or law must be capable in principle of being invalidated – of being disproved – by observation or experiment. That’s not possible with alien abductions, which can’t be either proved or disproved.

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