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In 2018, a mysterious cigar-shaped object entered the Solar System. It was baptized as Oumuamua, which in Hawaiian means “message in order of arrival.” , and in a recently published new study, a much more science fiction theory emerged: The object resembles a spaceship designed by an alien civilization rather than a cosmic iceberg.
Compared to comets we know well, the appearance and behavior of Oumuamua, which has since left the Solar System and is about 800 meters long, was quite strange; as it approached Earth, its movement accelerated as if pushed. To date, there is no satisfactory explanation of how this could have happened.
There are theories, of course, but most of them assume natural causes in the background. According to this, the object is made up of hydrogen, which evaporates when it reaches the sun, and this invisible escaping gas drives the comet.
This is disputed by a study published on August 17 in the prestigious astronomical journal The Astrophysical Journal Letters. According to the authors, Avi Loeb (Harvard University) and Thiem Hoang (Korean Institute of Astronomy and Space Sciences), the hydrogen hypothesis would not work in reality, and they also describe why.
How does a hydrogen comet behave?
Before we get into this, it’s worth learning a little more about the hydrogen hypothesis.
Oumuamua’s interstellar origin became apparent when its orbit was discovered to be hyperbolic and it left the Solar System. The first oddity astronomers noticed was that, unlike the other comets, it didn’t breathe a sigh of relief.
Comets generally come from areas farther from the Sun, and the ice on their surface begins to evaporate as soon as they get close to our star. This degassing is actually the plume that we can observe in almost all comets. Exhaust gas propels comets like a rocket engine, and since evaporation is strongest near the Sun, the celestial body may gain more momentum here.
The Astrophysical Journal Letters also reported an earlier study that Oumuamua was made wholly or entirely of molecular hydrogen (Htwo).
Hydrogen has a freezing point of -259.2 degrees Celsius, which means that objects made of hydrogen can only form in very cold places. However, according to the findings of the publication, the existence of “hydrogen comets” is not at all inconceivable, and we could not observe their degassing from Earth, so we cannot see their plume either.
What’s wrong with the theory that explains natural causes?
According to Hoang and Loeb’s calculations Even the dimmest starlight can disrupt the process of forming hydrogen radishes the size of Oumuamua. – the ice particles formed by hydrogen melt before forming larger celestial bodies. In his opinion, it is absolutely impossible for a giant hydrogen iceberg to travel several light years away without falling apart in the meantime due to the heat radiated by the stars.
Loeb’s truth is even recognized by Darryl Seligman, author of a study describing the hydrogen hypothesis. That is why he believes that Oumuamua may be “only” 40 million years old and come from somewhere “nearby”. This time is sufficient for the degassing to form a cigar-shaped object of the comet without falling to pieces.
The only question is what is the place of origin of the celestial body. We will probably never know for sure again, but Seligman also identifies two possible sources; the Carina and Columba group, which includes young stars, formed 35 to 40 million years ago, so even Oumuamua could be rejected from these regions.
Loebs, of course, questions the idea that Carina and Columba are not an ideal place for the formation of hydrogen ice blocks, which tend to form around larger molecular clouds.
The controversies surrounding the mysterious celestial body are unlikely to subside in the next few years.
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