Comets from our own Solar System come screaming into the bright light and melting heat of the inner regions, fleeing their birthplace into a dark and icy domain far, far away. In this mysterious region of cold and perpetual twilight, the icy and bright comet nuclei of our own Solar System remain as relics of an ancient era when planets were first forming from a myriad of frozen chunks of primordial material that collide and merge. planetesimals–the building blocks of the major planets. But sometimes a comet entering our Sun is the icy offspring of a distant star beyond our own. In January 2020, the astronomers of the National Astronomical Observatory (NAOJ) in Japan, announced that they have analyzed the trajectories of a duo of frozen wanderers on their way out of our Solar System and determined that they were most likely born into the family of another star. These findings improve astronomers’ understanding of the outer limits of our Sun’s own family – and beyond.

Not all the comets we see in our dark night sky travel in tight orbits around our Star. Some soar through our Solar System at impressive speeds before hurtling into the space between the stars, never to return. Although it is easy for astronomers to calculate where these comets are heading, determining where they originated is much more difficult.

Frozen tramps

Most comets are small objects in the Solar System that travel in elongated orbits that take them close to our Star for part of its orbit, and then to the remote outer limits of our Solar System for the rest. Comets are frequently classified according to the length of their orbital periods. The longer the period, the longer the orbit.

The two classes of comets in the Solar System are short period and long period.

Short period kites: Short period kites they are generally defined as those that have orbital periods of less than 200 years. These comets normally orbit (roughly) in the plane of the ecliptic in the same direction as the planets. Their orbits often carry these frigid wanderers into the realm of the quartet of gaseous outer planets – Jupiter, Saturn, Uranus, and Neptune – in aphelion (when they are farthest from our Sun). For example, him aphelion of the famous Halley comet it is slightly beyond the orbit of the outermost planet Neptune. Those comets that have a Aphelia near one of the orbits of a major planet they are known as its “family.” These “families” are believed to have formed when the planet gravitationally attracted what was originally long period kites in shorter orbits.

At the end of the shortest orbital period, Encke’s kite has an orbital period that does not even reach the orbit of the innermost giant planet, the banded giant Jupiter, and is therefore known as a Encke-type kite. Short period kites that have orbital periods of less than 20 years and have low inclinations to the ecliptic they are called traditional Comets of the Jupiter family (JFC). Comets that are similar to Halley comet, which sports orbital periods of between 20 and 200 years and show inclinations that extend from zero to more than 90 degrees, are called Halley-type kites (HTC).

Recently discovered comets, orbiting within the Handheld Asteroid Belt between Mars and Jupiter, they have been designated as a distinct class. These comets orbit in more circular orbits within the asteroid belt.

Because his elliptical orbits often bring them close to the quartet of gas giant planets, comets experience additional gravitational disturbances. Short period kites tend to have their Aphelia coincide with one of the semi-major axes of the giant planet, with the JFC populating the largest group. Kites traveling from the remote oort cloud– which forms a sphere around our entire Solar System that reaches up to the nearest star half beyond ours – has orbits that are powerfully influenced by the gravity of the giant planets as a result of close encounters. The huge planet Jupiter is, of course, the source of the most powerful disturbances. This is because Jupiter is more than twice as massive as all the other planets in our Solar System put together. These disturbances can divert long period kites in shorter orbital periods.

As a result of its observed orbital characteristics, short period kites believed to originate in the centaurs and the Kuiper belt / scattered disk. This disc is populated by frozen objects in the trans-Neptunian region. On the contrary, the origin of long period kites it is believed to be on the remote control oort cloud (named after the Dutch astronomer Jan Oort (1900-1992), who hypothesized its existence). A huge population of icy comet-like objects is believed to swarm within these remote regions in roughly circular orbits around our Sun. From time to time, gravitational disturbances caused by the outer giant planets (in the case of Kuiper Belt Objects) or nearby stars (in the case of Oort Cloud Objects) it can throw one of these icy bodies howling into an elliptical orbit that carries it inward, into the molten heat of our Sun, and a visible comet is born. In contrast to the predictable return of periodic comets, whose orbits have been well established in previous observations, the appearance of new comets cannot be predicted by this mechanism. When they are thrown into the orbit of our Star, being dragged perpetually towards its dazzling and turbulent fires, tons of matter are torn from the comets. This dangerous journey, of course, greatly shortens its “lifespan”.

Long period kites

Long period kites sporting periods ranging from 200 years to thousands of years. These frozen objects also show highly eccentric orbits. An eccentricity that exceeds 1 when close perihelion (when a comet is closer to our Sun) does not necessarily indicate that a comet will escape our Solar System.

By definition long period kites they are gravitationally bound to our Star. Comets that are ejected from our Sun family have generally been disturbed as a result of a path that has brought them too close to the main planets. As a result, they are no longer considered to have “periods”. The orbits of long period kites take them far beyond the realm of the quartet of giant planets in Aphelia, and the plane of their orbits need not be located near the ecliptic. For instance, Kite west–For long period kite–may have a aphelion distance of nearly 70,000 astronomical units (AU), with an orbital period calculated in approximately 6 million years. One FOR it is equal to the average distance between the Earth and the Sun, which is approximately 93,000,000 miles.

As of 2019, only two comets with an eccentricity significantly greater than 1 have been detected: 1I / ‘Oumuamua and 2I / Borisov. This indicates that the two comets originated beyond our Solar System and are the wandering children of another star. Weather Oumuamua It showed no optical signs of cometary activity during its journey through the inner Solar System in October 2017, alterations in its trajectory, suggesting outgassing, indicate that it is likely a comet. In contrast, the interstellar comet, 2IBorisov, It has been observed that the gossiper shows eat characteristic feature of comets.

In addition to comets born in our own Solar System, exocomets circling other stars, they have also been detected. Indeed, exocomets they are believed to be common throughout our Milky Way. First exocomet system to discover circles a Main sequence (burning hydrogen) named star Beta Pictoris. Beta Pictoris it is very young by star standards, “only” around 20 million years old. Eleven of those exocomet systems have been detected, as of 2013, by astronomers using the Absorption spectrum which is caused by the large clouds of gas that comets emit when they travel close to their star. For a decade, the Kepler space telescope searched for planets and other bodies beyond our Solar System. The first transit exocomets were discovered in February 2018 by a team of professional astronomers and citizen scientists studying the light curves recorded by Kepler. After KeplerThe mission ended in October 2018, a new telescope called TESS assumed his mission. Given that TESS was launched, astronomers have used it to discover the transits of exocomets around Beta Pictoris using a light curve obtained from TESS.

If there is a large population of comets flying in the space between the stars, they would travel at speeds of the same order as the relative speeds of stars near our Sun, that is, a few tens of kilometers per second. If these icy wandering children of another star entered our Solar System, they would possess positive specific orbital energy and would be observed to have hyperbolic trajectories. A rough calculation shows that there could be four hyperbolic comets per century within the orbit of Jupiter, plus or minus one and possibly two orders of magnitude.

Where are you going and where have you been?

Two possible scenarios have been proposed to explain the existence of mysterious outgoing comets. According to the first model, a comet is born in a stable orbit far away from the Sun. Unfortunately, gravitational disturbances with a passing object tear the comet out of its original orbit. The comet then migrates to the warm, well-lit inner Solar System, where it can be observed before it is unceremoniously evicted into interstellar space. In contrast, the second model proposes that a comet is born somewhere very far away, perhaps within a completely different planetary system. As the frigid wanderer traverses the space between the stars, by sheer chance he enters our own Solar System before continuing on his journey.

Dr. Arika Higuchi and Dr. Elichiro Kokubo in NAOJ calculated the types of trajectories that would normally be expected in each of the two models. The team then compared their calculations with the duo’s observations of strange protruding objects, ‘Oumuamua and 2I Borisov. The astronomers found that the interstellar origin scenario provided the best match for the trajectories of both unusual comets.

The astronomers also showed that it is possible for giant bodies of gas, which roam near our Solar System, to destabilize. long period kites. According to this scenario, the disturbed comets are launched on similar paths as the two unusual comets. The survey observations have not revealed any bodies the size of a gas giant that can be linked to the mysterious duo of outgoing comets. However, more studies, both observational and theoretical, of small interstellar objects are needed to better understand the origins of these strange travelers.