This is an interstellar comet, an ancient ball of ice, gas and dust, formed on the frozen periphery of a distant star, which, by a lucky chance and due to a strange twist of gravity, was “thrown” in our direction.
For astronomers, this comet has become a “premise” from outer space, a small fragment of the star that they can never visit, the key to all the worlds that they cannot observe on their own.
This is just the second interstellar “guest” that scientists have seen in our solar system. And the first “alien object”, which they were able to well consider. By tracking the comet’s movement, determining its composition and observing its behavior, researchers are trying to understand where it came from and what space it overcame before getting here. They have already discovered in its composition a carbon molecule and, possibly, water – two familiar chemicals in an object that arose in another stellar system.
When the sun goes down over the Tennessee Mountains and stars begin to flicker, astronomer Doug Durig rises to the roof of his observatory, turns on his three telescopes and directs them into the sky.
Every night, the comet in the sky becomes larger and brighter, forming a cloud of gas and dust around itself, which can become the key to unraveling its history. On the eighth of December it will approach it most closely to the Earth, appearing to researchers as a close-up, after which it will return to a cold, faceless void.
And far below, in the dark, Dyurig will wait.
Parcel from the Unlabeled Universe
Each star in the night sky represents a possible solar system. Each light in the Universe is, most likely, the sun of some planet of another star system.
This is the main lesson learned over twenty years of studying exoplanets. Scientists have discovered thousands of worlds outside our solar system: gas giants and tiny rocky spheres, worlds illuminated by the dim light of red suns, and celestial bodies that orbit around the spinning remnants of exploding stars. There are even planets that revolve around medium-sized yellow suns like ours, although none of the celestial bodies found to date can match the characteristics of the Earth, which has a habitable atmosphere and deep blue oceans.
However, even if you look at exoplanets through the most powerful telescopes, you can see only spots of light and glare. And none of the people living on Earth hopes to fly to another star, because in order to even get closer to the closest of them, it would take 40 thousand years.
To carefully study the other solar system, scientists hoped that they could wait until a fragment of one of these stars flies to us.
This happened in the quiet predawn minutes of August 30 in the Crimean mountain village. The amateur astronomer noticed a dim spot on the horizon, barely visible against the background of sparkling stars.
Gennady Borisov transferred the data of his observations to the Minor Planet Center, an organization that collects and systematizes data on small bodies in the solar system so that other scientists can familiarize themselves with them.
After some time, this strange observation report caught the attention of Durig, who conducted his nightly observations on the other side of the world.
“I was the second to see her,” said Durig. “And the fact that the comet really exists has been confirmed.”
For a couple of weeks, scientists have collected enough data to calculate the orbit of the comet. But they found that the orbit is not elliptical in shape, which is usually the case with comets orbiting the Sun, but hyperbolic – it is not closed. The object also moved at a speed of 41.57 kilometers per second, much faster than any comets, asteroids or planets that revolve around our sun.
“Wow,” exclaimed Davide Farnocchia, a navigation systems engineer at NASA’s Jet Propulsion Laboratory, who was one of the first to determine that the comet had flown from another star. “I did not expect to see anything like that.”
Only one interstellar object was discovered in our solar system: a cigar-shaped body made of stone called “Oumuamua”, which is translated from the Hawaiian language as “messenger from afar”.
But in October 2017, when Oumuamua was discovered, he was already leaving the system, and was so vaguely visible that scientists were unable to examine it and only observed a light point. They did not quite understand what they saw – an asteroid made of metal, stone or a comet made of ice and dust. And they did not know if it was just a happy accident that would never happen again, or a harbinger of future events.
Therefore, the researchers were surprised and delighted when, in less than two years, another interstellar messenger arrived
It is expected that the new comet, dubbed 2I / Borisov (which indicates its discoverer and the status of the second of the known interstellar objects), will be within reach of telescopes until the fall of 2020. At the maximum approximation, what will happen next month, it will be twice as far from the Earth as the Earth from the Sun.
Although Comet 2I / Borisov entered the solar system from the side of the constellation Cassiopeia, scientists still do not know where it came from, or how much it flew through the desert interstellar space. Given its current speed, it must have been flying for millions, if not billions of years.
As an object approaches the Sun, ice on its surface under the influence of heat turns into gas. This creates a characteristic “halo” like halo, which scientists can examine in detail to determine what the comet consists of. Already, comet 2I / Borisov has been observed more than two thousand times.
“It will be fun when it comes to exploring this object … because it first flew from where the temperatures are extremely low,” said Michele Bannister, an astronomer at the University of Queens in Belfast. “Let’s open it and see what we have with this special present from another star.”
Little Wanderers Wandering the Galaxy
The discovery of exoplanets has shown that we live in a crowded space. But it also allowed earthlings to understand how lonely we are. Most of the planetary systems discovered in recent decades are very incomprehensible, and exoplanets of the most common kind – the body is larger than the Earth, but smaller than Neptune – are far from us.
When astronomers knew only our own solar system, “it seemed that the issue of planet formation was resolved,” says Malena Rice, an astrophysicist at Yale University. “And then all these strange systems suddenly appear that do not fit into our ideas.”
Interstellar comets can be very useful in solving this riddle. They are “born” from the same rotating disk of gas and dust from which planets are formed around a young star. But then they get stuck on the ice periphery of the solar systems, where they can retain the primary components involved in the formation of the planets.
It turned out that comets in our solar system contain some of the basic components necessary for the origin of life: water, carbon, and even complex organic compounds. And now, having studied comet 2I / Borisov, one could find out whether the main molecules necessary for the origin of life were among the “building blocks” from which the world was formed, which was outside our own world.
This fall, Bannister colleague Alan Fitzsimmons discovered for the first time in history a chemical compound emitted by an interstellar comet. Having expanded the luminescence of the comet 2I / Borisov spectrum, his team discovered the characteristic signs of a cyanogen, a molecule consisting of a carbon atom and a nitrogen atom bound together. This gas is usually present in comets revolving around this sun.
“When, when I was in the office, I saw this, I cried out … what doesn’t often happen in a respectable newspaper,” recalls Fitzsimmons.
A few weeks later, astronomer Adam McKay discovered that the comet emits oxygen, which indicates that sunlight enters the water on the surface and the water molecule breaks up. If this is confirmed, then this will be the first case of the discovery in our solar system of water formed in another planetary system. In addition, this serves as further evidence that comet 2I / Borisov is very similar to comets known to us.
“It is possible that even in these other systems, the structure of which is very different, the basic physical and chemical parameters are still very similar,” says Mackay, a fellow at the Goddard Space Flight Center, NASA Research Laboratory.
By modeling our solar system, it can be assumed that about 90% of the material left after the formation of the planets was thrown into interstellar space. In the comic space beyond Neptune there are still millions of ice objects that could have been knocked out of orbit and thrown away from the sun for millennia.
If any of these scattered fragments, under the influence of gravitational forces, is pulled into another system and begins to glow in the rays of its star, then to any observer it will appear to be an interstellar comet.
“Surprisingly, this has versatility,” says Bannister. “Our planetary system is intertwined with another planetary system at the expense of these little wanderers roaming the galaxy.”
Long night
Only one hour is left before dawn, comet 2I / Borisov should appear above the horizon and make its way along the eastern part of the sky. For Durig, the long night was almost over.
Sevani: The University of the South, a liberal arts college with 1,600 students and Dyurig’s staff, doesn’t have the powerful high-resolution devices needed to monitor barely visible objects in the night sky. Instead, he must take hundreds of shots from the same place, and then use a computer program to process them for brighter and sharper images.
The astronomer checks the focus of his 12-inch Schmidt-Cassegrain telescope and adjusts it, preparing to take pictures of the part of the sky where the interstellar comet is to appear. He rubs his eyes with his eyes, which are tired and bake after long hours spent in the dim light of the red lamps, which he uses to protect his vision during night work.
This work is tiring and often monotonous. Unlike the discoverers, those who conduct all subsequent observations do not have to put their names on anything. And unlike researchers working in the largest observatories in the world, people like Durig face real obstacles that prevent them from achieving the results that are published in prestigious journals.
However, outstanding discoveries must be confirmed and clarified again and again, what ordinary people do. Probably, in order to become famous, you need to make an important discovery, and knowledge is cemented by ordinary people who do routine work after discoveries.
Here in Sevan, in a cramped observatory cluttered with piles of papers with observational data and piles of broken equipment, he hopes to someday change his work and turn it into something useful: “We are doing a very important scientific work,” says Durig. “We fill in all the gaps.”
Having taken a lot of pictures with a telescope, which took an entire hour, Durig composes them in 100 pieces. In the images taken, the colors are distributed the other way around, as in the negative, so the stars look like black strokes on a white background. In the lower left corner a dark dot is visible, surrounded by a “fluffy” halo.
Durig clicks, proceeds to the next group of shots, and the point moves an inch. Another click, and she moves again.
That is how, in his opinion, he looks at the comet, a fast and surrounded by a cloud of dust object that does not behave like everything else in the sky.
Dewig sends his images and whereabouts of the comet to the Center for Minor Planets – another drop in a sea of scientific knowledge.
Such consecutive joint observations that are carried out by the same people every night with the same instruments will become even more important when the comet can be observed in the Southern Hemisphere, where many of the world’s largest telescopes are located. They should be sent with extreme accuracy, so astronomers need to clearly determine the comet’s flight path and take into account everything that can slightly change it, for example, gas flares.
An accurate calculated orbit is of fundamental importance for the implementation of the most ambitious plan of astronomers regarding the comet.
“If we can find the most probable trajectory, then based on the exact direction in which it is approaching, we can track its beginning … maybe we can find out its origin, from which planet system it is,” says Farnokkya, an engineer from the Jet Laboratory NASA movements.
Determining the comet’s parent star would be the greatest achievement; for astronomy, it would be the same as finding a person who wrote it and sent it millions of years ago over billions of kilometers from a note in a bottle. Most scholars acknowledge that this may not be possible.
But it is possible that everything will work out, they say. Because the comet has already revealed many other secrets. It will allow us to learn something about the birth of solar systems. It has become the link between our home and what is happening in the galaxy in a broader sense. And now, when we saw this, it is easier for us to believe that there are still many other discoveries ahead.
And here, on Earth, Durig and his fellow astronomers will work, peering into the dark night sky, and wait.
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