Date with ʻOumuamua. First interstellar object in the Solar System
On October 19, 2017, when analyzing the data of the Pan-STARRS telescope, the long-awaited discovery occurred - the first interstellar object in the Solar System. The search for interstellar small bodies (comets and asteroids) has been devoted to whole decades, many articles, where the upper limits were calculated for their number in a unit volume of the Galaxy. And then - finally.
Since it was already several days after the opening, and Ethan was silent for some reason, I decided to write an article myself.
Actually the object itself, which was first called P10Ee5V, had a trajectory that showed one unusual feature that has never been seen before in any of the hundreds of thousands of small bodies of the Solar System that have been discovered to date. The calculated eccentricity of the “orbit” turned out to be ~ 1.2. The word "orbit" here was quoted, since with an eccentricity of more than 1, a closed circular or elliptical orbit turns into an open hyperbolic trajectory. But one eccentricity is not enough. Objects with an eccentricity a little more than 1 had already been discovered before, but it always turned out that this was due to a disturbance from the planets of the Solar System or disturbances of the Oort Cloud by stars. Knowing the eccentricity and perihelion distance (the minimum distance that an object approaches the Sun), one can calculate the speed with which a certain celestial body moved when it was far from the Sun and the influence of the planets of the Solar System. For example, for comets from the Oort Cloud, this speed “at infinite distance” never exceeds ~ 200 m / s. For the recently opened P10Ee5V object, this velocity was ~ 26 km / s. Since this velocity approximately coincides with the average relative velocity between stars neighboring the Sun, doubts that the object is of interstellar origin immediately disappeared. The object began to be called the first interstellar comet - C / 2017 U1 (Pan-STARRS).
The largest telescopes in the world were torn from their schedules and aimed at the earliest possible study of a temporary guest of the Solar System. Looking ahead - at the end of November, observations are planned with space telescopes to them. Hubble and them. Spitzer.
It is interesting that when the researchers “rewound” the position of the object back in time, they found that its trajectory leads from the constellation Lyra , that is, exactly in the direction of the solar system relative to the averaged motion of neighboring stars, which also removes any doubts about the origin of this object.
The new object immediately threw a puzzle to astrophysicists - the lack of noticeable comet activity. The object was supposed to be formed in the same way as the objects of “our” Oort Cloud, and from the Oort Cloud, astronomers observe precisely comets. Actually from the category of comets C / 2017 U1 was demoted and a new designation was given - A / 2017 U1 (to emphasize the absence of cometary signs). A little later, astronomers introduced a new designation for interstellar objects and the object began to be designated 1I (I - “interstellar”), which clearly demonstrates all the commotion caused by this guest in the astronomical community. A name was also given in Hawaiian - 'Oumuamua , which means something like “pioneer”. In connection with the absolute illegibility of this name, hereinafter in the article the hero of the occasion will be designated simply "U1 ".
It is worth noting that before being open, on September 9, 2017, U1 approached the Sun 4 times closer than the Earth. Then U1 began again to move away from the Sun and “whistled” unnoticed at a fairly small (by the standards of the Solar System) distance from the Earth on October 14 - only 0.16 AU (one and a half times closer than the minimum distance to Venus, the closest planet to Earth). And only 5 days later, U1 was discovered already receding at a distance of 0.2 AU Later, U1 was still detected in the images from October 14 and 18, which allowed to clarify its trajectory. The fact that astronomers could not find a single interstellar object around for a long time until they practically “poked it with their nose” suggests that there can be quite a lot of such objects within the Solar System right now, however, interstellar objects,
From observations by many telescopes, it was possible to find out some properties of U1. The size is likely about 100 to 200 meters (judging by the light curve, it has an elongated shape with a ratio of 1: 2). By the standards of typical comets and asteroids, it’s a pretty small object. It was even possible to obtain spectra, but the errors are so large that it is not yet possible to draw an unambiguous conclusion about the surface composition. Everything suggests that U1 is similar in spectrum to the nuclei of comets and some asteroids rich in organic matter (the so-called spectral class “D”). However, quite heated discussions are ongoing regarding the interpretation of the spectrum, and other options cannot yet be completely ruled out.
The scientific journals have already begun an avalanche of articles devoted to this discovery, which will provide researchers with work for months and even years ahead. The mystery of the lack of cometary activity alone is worth a lot. Perhaps this is not a comet or even an asteroid at all? The famous science fiction writer Arthur Clark has a no less famous work, “Date with Rama,” which tells about the collision of mankind with an alien starship moving through the solar system along a hyperbolic trajectory. Here is a short excerpt from the very beginning of the novel:
As can be seen from the graph of the number of near-Earth asteroid discoveries by years below, they began to systematically "comb" outer space since about 1997:
Moreover, the increase in the number of open small bodies can be roughly considered linear. That is, over the past 20 years, the area of the "combed" space has grown. Given the movement of the Sun among many interstellar objects and the motion of the Earth around the Sun, we can estimate the volume in which the first interstellar object was discovered. In shape, this volume will look like a spiral, the thickness of which grows with each turn. The length of such a (expanded) spiral will be ~ 1688 AE over 20 years. Since U1 was detected at a distance of 0.2 AU from the Earth, the thickness of this spiral will increase from 0 to 0.2 AE. Then the resulting volume of space will be approximately 71 cubic meters. AE. This volume corresponds to a sphere with a radius of 2.57 AU, that is, in this radius, as a rule, at least one such object should always be located.
If we assume that the distribution of interstellar small bodies is exponential with an exponent of -3, then we can estimate how many more objects and what size nearby should be:
New observations indicate strong variability - the brightness of U1 varies 4-6 times with a period of about 8 hours and 2 peaks. There are no asteroids in the Solar System with such a strong variability of light that makes the object U1 even more mysterious.
Since it was already several days after the opening, and Ethan was silent for some reason, I decided to write an article myself.
Actually the object itself, which was first called P10Ee5V, had a trajectory that showed one unusual feature that has never been seen before in any of the hundreds of thousands of small bodies of the Solar System that have been discovered to date. The calculated eccentricity of the “orbit” turned out to be ~ 1.2. The word "orbit" here was quoted, since with an eccentricity of more than 1, a closed circular or elliptical orbit turns into an open hyperbolic trajectory. But one eccentricity is not enough. Objects with an eccentricity a little more than 1 had already been discovered before, but it always turned out that this was due to a disturbance from the planets of the Solar System or disturbances of the Oort Cloud by stars. Knowing the eccentricity and perihelion distance (the minimum distance that an object approaches the Sun), one can calculate the speed with which a certain celestial body moved when it was far from the Sun and the influence of the planets of the Solar System. For example, for comets from the Oort Cloud, this speed “at infinite distance” never exceeds ~ 200 m / s. For the recently opened P10Ee5V object, this velocity was ~ 26 km / s. Since this velocity approximately coincides with the average relative velocity between stars neighboring the Sun, doubts that the object is of interstellar origin immediately disappeared. The object began to be called the first interstellar comet - C / 2017 U1 (Pan-STARRS).
The largest telescopes in the world were torn from their schedules and aimed at the earliest possible study of a temporary guest of the Solar System. Looking ahead - at the end of November, observations are planned with space telescopes to them. Hubble and them. Spitzer.
It is interesting that when the researchers “rewound” the position of the object back in time, they found that its trajectory leads from the constellation Lyra , that is, exactly in the direction of the solar system relative to the averaged motion of neighboring stars, which also removes any doubts about the origin of this object.
The new object immediately threw a puzzle to astrophysicists - the lack of noticeable comet activity. The object was supposed to be formed in the same way as the objects of “our” Oort Cloud, and from the Oort Cloud, astronomers observe precisely comets. Actually from the category of comets C / 2017 U1 was demoted and a new designation was given - A / 2017 U1 (to emphasize the absence of cometary signs). A little later, astronomers introduced a new designation for interstellar objects and the object began to be designated 1I (I - “interstellar”), which clearly demonstrates all the commotion caused by this guest in the astronomical community. A name was also given in Hawaiian - 'Oumuamua , which means something like “pioneer”. In connection with the absolute illegibility of this name, hereinafter in the article the hero of the occasion will be designated simply "U1 ".
It is worth noting that before being open, on September 9, 2017, U1 approached the Sun 4 times closer than the Earth. Then U1 began again to move away from the Sun and “whistled” unnoticed at a fairly small (by the standards of the Solar System) distance from the Earth on October 14 - only 0.16 AU (one and a half times closer than the minimum distance to Venus, the closest planet to Earth). And only 5 days later, U1 was discovered already receding at a distance of 0.2 AU Later, U1 was still detected in the images from October 14 and 18, which allowed to clarify its trajectory. The fact that astronomers could not find a single interstellar object around for a long time until they practically “poked it with their nose” suggests that there can be quite a lot of such objects within the Solar System right now, however, interstellar objects,
What is U1
From observations by many telescopes, it was possible to find out some properties of U1. The size is likely about 100 to 200 meters (judging by the light curve, it has an elongated shape with a ratio of 1: 2). By the standards of typical comets and asteroids, it’s a pretty small object. It was even possible to obtain spectra, but the errors are so large that it is not yet possible to draw an unambiguous conclusion about the surface composition. Everything suggests that U1 is similar in spectrum to the nuclei of comets and some asteroids rich in organic matter (the so-called spectral class “D”). However, quite heated discussions are ongoing regarding the interpretation of the spectrum, and other options cannot yet be completely ruled out.
The scientific journals have already begun an avalanche of articles devoted to this discovery, which will provide researchers with work for months and even years ahead. The mystery of the lack of cometary activity alone is worth a lot. Perhaps this is not a comet or even an asteroid at all? The famous science fiction writer Arthur Clark has a no less famous work, “Date with Rama,” which tells about the collision of mankind with an alien starship moving through the solar system along a hyperbolic trajectory. Here is a short excerpt from the very beginning of the novel:
...
When the elements of the orbit of the new asteroid were calculated, the riddle seemed to be
solved, but it was replaced by another, more substantial one.
Number 31/439 was not at all an ordinary asteroid, running in an
elliptical orbit and repeating it with the accuracy of a clockwork
every few years. He turned out to be a lonely interstellar wanderer who
visited the Solar System for the first and last time, and moved so
swiftly that even the gravitational field of the Sun was not able to
capture him. Piercing the orbits of Jupiter, Mars, Earth, Venus and
Mercury and continuously gaining speed, he had to finally
go around the Sun and again go into the unknown.
Then, having completed the calculations, computers sent people signals:
“Attention! We have unearthed something interesting for you, ”and number 31/439
first attracted the attention of mankind. A light flurry of excitement at the
headquarters of the Space Patrol - and the interstellar stroller, instead of an ordinary
number, was awarded a proper name. Astronomers have long exhausted both
Greek and Roman mythology, and now set to the Hindu
pantheon. Number 31/439 was named Rama.
...
More about U1
- Wikipedia
- NASA: Small Asteroid or Comet 'Visits' from Beyond the Solar System
- A / 2017 U1, first interstellar asteroid ever detected!
UPDATE
As can be seen from the graph of the number of near-Earth asteroid discoveries by years below, they began to systematically "comb" outer space since about 1997:
Moreover, the increase in the number of open small bodies can be roughly considered linear. That is, over the past 20 years, the area of the "combed" space has grown. Given the movement of the Sun among many interstellar objects and the motion of the Earth around the Sun, we can estimate the volume in which the first interstellar object was discovered. In shape, this volume will look like a spiral, the thickness of which grows with each turn. The length of such a (expanded) spiral will be ~ 1688 AE over 20 years. Since U1 was detected at a distance of 0.2 AU from the Earth, the thickness of this spiral will increase from 0 to 0.2 AE. Then the resulting volume of space will be approximately 71 cubic meters. AE. This volume corresponds to a sphere with a radius of 2.57 AU, that is, in this radius, as a rule, at least one such object should always be located.
If we assume that the distribution of interstellar small bodies is exponential with an exponent of -3, then we can estimate how many more objects and what size nearby should be:
- Within a radius of 5.13 AU from the Sun: ~ 8 objects no larger than 0.3 km
- Within a radius of 10.3 AU from the Sun: ~ 64 objects no larger than 0.6 km
- Within a radius of 20.5 AU from the Sun: ~ 512 objects no larger than 1.2 km
- Within a radius of 41 AU from the Sun: ~ 2048 objects no larger than 2.4 km
UPDATE 2
New observations indicate strong variability - the brightness of U1 varies 4-6 times with a period of about 8 hours and 2 peaks. There are no asteroids in the Solar System with such a strong variability of light that makes the object U1 even more mysterious.