The interstellar object ‘Oumuamua would be a comet in disguise

Researchers studying the interstellar object ‘Oumuamua said that it might be an icy core hidden by a rocky, protective crust.

(ESO/M. Kornmesser)


Although it looks like an asteroid, the first interstellar object spotted passing through the solar system, the so-called ‘Oumuamua, maybe more like a comet in disguise.

When astronomers first spotted on the long, tumbling interstellar object ‘Oumuamua the passing of the solar system in October, they were surprised, not only did it come from outside the solar system, according to his job, it seemed to be an asteroid instead of comet researchers thought it was more likely for an interstellar visitor.

However, a new paper suggests ‘Oumuamua can be made of ice, like a comet, just disguised with a protective crust. [‘Oumuamua: The solar system the First Interstellar Visitor in Photos]

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According to professor Alan Fitzsimmons of Queen’s University Belfast, Northern Ireland, there is much more icy than rocky stuff” in the solar system, making it more likely for envoys of other systems can also be icy, like other solar energy systems developed in the same way.

“We know that our solar system has ejected a lot more icy bodies and rocky bodies,” Fitzsimmons, lead author of the paper published today (Dec. 18) in the journal Nature, Astronomy, told

If the solar system formed, planets are made of gas and ice in the vicinity of the outer edges of the solar system and ejected billions of objects, Fitzsimmons said. In addition, the mass of the small icy bodies in the outer reaches of the solar system, known as the Oort cloud, has lost over billions of years as a result of heavy disturbance of other stars. It was therefore logical for astronomers to expect the first interstellar visitor they would see the need to have of a comet.

“Given the fact that this object passed relatively close to our sun it was a trip through our solar system, one would expect the ices to the surface in principle be heated and it needs to behave like a comet,” Fitzsimmons said. “We should see gas streaming off the surface, we should see dust particles are ejected in the cometary atmosphere, maybe even a tail.”

But astronomers observe ‘Oumuamua with their telescopes have seen no signs of such a behavior. They concluded that the object must be rocky in nature — an asteroid. However, when Fitzsimmons and his colleagues looked at the surface of the object better, they find it doesn’t look like a typical asteroid.

“We didn’t see any signs of typical spectroscopic signatures that you would expect from the minerals on the surface of an asteroid we see in our solar system,” Fitzsimmons said. “It rather seems to resemble the [icy] objects that are there in the outer solar system. That was our head-scratching. If the object had, originally at least, ice, what happened?”

Fitzsimmons and his colleagues looked at older studies and laboratory experiments, which tried to find out what happens with icy bodies such as comets, which are exposed during a long time of energetic particles and cosmic rays. These studies suggest that the ice of the surface layers of such bodies vaporized by the cosmic environment.

“What is left is converted into a relatively rigid and desiccated surface held together by the carbon compounds, which at the same time gives a kind of reddish pink color,” Fitzsimmons said. “And that is what we saw in our spectra.” [Living on a Comet: “Dirty Snowball” Facts Explained (Infographic)]

The astronomers ran a series of computer experiments to model the behavior of the now icy ‘Oumuamua. They find that if the object crust was just 20 inches (50 cm) thick, would protect the ice on the object at the core of the warmth of the sun, thus preventing the display of the warning signs of gas and dust leaving a comet.

In a separate paper that will be published in the Astrophysical Journal Letters later this month, Fitzsimmons’ colleague Michele Bannister, also of Queen’s University, looked at the further properties of ‘Oumuamua in the near-infrared spectrum and compared the data with that of similar objects in the outer solar system. She found a whopping agreements.

“We have discovered that this is a planetesimal with a well-baked crust that looks a lot like the smallest of the worlds in the outer regions of our solar system,” Bannister said in a statement. “It is a gray/red surface and is very long, probably about the size and shape of the Gherkin skyscraper in London.”

While ‘Oumuamua arrival is one of the most important astronomical events of 2017, Fitzsimmons and Bannister expect that such events will not be in the future. Similar objects are likely to make it in the solar system quite frequently, the astronomers said, but they are usually too weak to spot with the current telescopes. As telescope technology advances, Fitzsimmons said he expects that the astronomers in the not so distant future will be able to study such interlopers may each year.

“On the horizon we have a new telescope facility they are building at the moment called the Large Synoptic Survey Telescope in Chile,” Fitzsimmons said.

“That is an incredibly powerful survey machine. If that starts to work in the first half of the next decade, which will have a much better chance of detecting these objects in the solar system than the current facilities that we have.”

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