The solar system's Interstellar Visitor 3I/ATLAS is expected to reach perihelion on October 29. Earlier this week, it reached conjunction, which means it is behind the Sun relative to Earth and cannot be observed from Earth. However, scientists have used spacecraft stationed near Mars to observe it, and it will return to people's view again at the end of November.
Harvard astronomer:
It may be "making small moves" behind the sun
Although scientists have gathered a wealth of evidence that this unusual visitor from other star systems is a comet, composed mainly of carbon dioxide and ice, Harvard astronomer Avi Loeb has never given up his suspicions.He speculated that 3I/ATLAS is a huge "mothership" sent to the solar system by an alien intelligent civilization.
▲The Hubble Telescope captured 3I/ATLAS on July 21
Loeb has repeatedly pointed out the object's "anomalies," from its enormous size to its unusual trajectory that brought it suspiciously close to Mars earlier this month.
In a new blog post, Loeb said that if 3I/ATLAS were a spacecraft, it might use its powerful gravitational proximity to the sun to speed up or slow down—while hiding just behind it.
Loeb used the Obert effect to support his theory that 3I/ATLAS, if indeed a spacecraft, might use perihelion to increase its speed.
The Obert Effect means that a spacecraft engine burns fuel most efficiently when its orbital speed is maximum. The astronomer said: "If 3I/ATLAS is a huge mothership, it is likely to continue flying along its original gravitational path and eventually leave the solar system. In this case, the Obert effect may apply to the conditions when it launches micro-probes to the solar system planets at perihelion."
Loeb believes that the “best time” for 3I/ATLAS to adjust its speed is near perihelion. "I noticed that this best time coincided with a period when various telescopes could not observe it," Loeb pointed out. "Is this just a coincidence, or is it due to careful orbital design and aerospace technology?"
astronomer:
Spouts water vapor at a pouring rate of approximately 88 pounds per second
The scientific community has repeatedly poured cold water on Loeb's jaw-dropping idea. Astronomers believe that 3I/ATLAS came from the center of the Milky Way, was likely expelled from its original star system by gravitational disturbances (such as a close flyby of another star), traveled through interstellar space, and eventually passed through our solar system.
Based on these inferences, astronomers estimate that the comet must be billions of years old, perhaps even 3 billion years older than the sun itself. It's not just a snapshot of a different part of the Milky Way, it's a microcosm of an entirely different era in the universe.
Fortunately, 3I/ATLAS will provide us with more observation opportunities before it completely leaves the solar system. It is expected to make a close approach to Jupiter next month, when NASA's Juno probe and the European Space Agency's Juice probe will have a chance to catch a glimpse of it.
Currently, 3I/ATLAS is behind the sun. Previously, astronomers discovered that 3I/ATLAS was spewing large amounts of water. Its ratio of carbon dioxide to water appears to be surprisingly high compared to comets in the solar system.
Images of 3I/ATLAS captured by NASA's Neil Grylls Swift Space Telescope show that it emits intense ultraviolet radiation, a sure sign of hydroxyl gas (OH), a byproduct of water. Because UV rays are absorbed by the atmosphere, these radiations can only be observed from space.
The astronomers, whose findings were published in the Astrophysical Journal Letters, believe that the presence of all OH indicates that the comet is spewing water vapor at a rate of about 88 pounds per second - about the same speed as a fire hose running at full speed.
The most peculiar thing is that this phenomenon occurs quite far away from the sun, about three astronomical units (AU) from the center of the sun, which is equivalent to three times the distance between the earth and the sun. Normally, when a comet approaches the sun, the water ice in its core (called the comet's nucleus) begins to sublime, changing from solid to gas in an instant.
"When we detect water from an interstellar comet, we are reading a record from another interstellar system," said Dennis Bodwitz, a professor of physics at Auburn University and co-author of the research article. "It tells us that the ingredients for the chemistry of life are not unique to us."
It's weird in many ways compared to comets within our solar system, hinting at just how unique these unimaginable alien worlds are, and suggesting there's still much we don't yet understand about how star systems form and how their structures evolve.