The solar system was smaller in the past. According to a new theory, Neptune long ago migrated away from the Sun and took a vast field of rocks with it.
An enigmatic field of ice blocks known as the Kuiper Belt came to populate the outer regions of the Solar System thanks to a gravitational nudge from young Neptune billions of years ago. This is according to research.
The Kuiper Belt is a disk-like region that moves behind the orbit of Neptune and is inhabited by icy bodies, which according to some theories also include Pluto, whose status as a planet is in doubt, and may be the source of several types of comets.
However, the belt has raised questions since it was discovered in the XNUMXs by the American-Dutch astronomer Gerard Kuiper, who said that it is the remnant left over from the building blocks of the solar system. One of the reasons for this is that the belt has too little mass relative to its large distance. Either it lost mass over time, or it formed closer to the Sun and was moved.
In an article published last Thursday in the British journal Nature, Harold Lewison of the Southwest Research Center in Boulder, Colorado, and Alessandro Morbidelli of the Cote d'Azur Observatory in Nice went back to the early days of the solar system.
In its initial stage, the solar system contained the sun and the embryonic planets - a mixture of gas and dust that crystallized into larger masses. The forming planets were surrounded by giant rings of bodies the size of asteroids called planetesimals that orbit the sun at distances of up to 5 billion kilometers from the sun, according to the theory. The gravitational pull of this giant ring was such that the young planets except Jupiter were deflected away from the Sun.
As their orbits expanded the planets gathered additional mass from the dust and rocks surrounding them, and then their gravitational force in turn affected the orbit of the planetesimals. In the end, the rest of the planetesimals were pushed out by Neptune - who by now had already become a gas giant - and that's how the belt reached its current location - about 7 billion kilometers from the Sun.
The original Kuiper belt could have been almost empty and retained only a small mass. says Rodney Gomez, of the Federal University of Rio de Janeiro, Brazil, in a release.
The solar system built by Neptune
Robert Roy Britt, space.com (Translation: Dikla Oren)
The solar system was smaller in the past. According to a new theory, Neptune long ago migrated away from the Sun and took a vast field of rocks with it.
The idea of the great Neptune construction project is based on computer simulation, which tries to solve a mystery that has been troubling astronomers for the past few years. In 1992 researchers discovered the first object beyond Neptune other than Pluto (Pluto is sometimes inside Neptune's orbit and sometimes outside it).
Today the area is known as the Kuiper Belt, and about 1000 Kuiper Belt Objects (KBOs - Kuiper Belt Objects) have been found. The size of some of them is almost half the size of Pluto. Scientists estimate that there are at least another billion such objects, large and small.
But not everyone is supposed to be there.
The leading theory of the formation of the Solar System holds that KBOs such as asteroids, comets and rocky planets formed shortly after the birth of the Sun about 4.6 billion years ago. Remnants of gas and dust, called the pre-planetary disk (protoplanetary disk), collided and remained together.
For the impact and adhesion scenario to occur in today's Kuiper belt, the region would have to contain an amount of material ten times greater than the amount of material on Earth. This amount of matter is needed to allow for the chance of collisions, which create large objects.
Observations so far have suggested that the Kuiper Belt contains only about a tenth of the mass on Earth.
Researchers tried to figure out where the missing material went. Collisions between the Kuiper belt itself may have turned most of the material into dust, and it was blown out of the solar system. But this explanation is not accepted by everyone. The new theory simply concludes that this substance was not there in the first place.
"The truth is that we haven't solved the problem of the lack of mass," says Harold Levison of the Southwest Research Institute. "We tricked her."
Levison and his colleague Alessandro Morbidelli concluded that the outer boundary of the Kuiper Belt used to be where Neptune is now, about 30 astronomical units (AU) away. One astronomical unit is the distance between the Earth and the Sun.
In space there was enough material for self-evolving Kuiper Belt KBOs. Then the gravity of Neptune, which was also soft in years at the time, would have pushed some of these objects outwards, where they would have settled into more or less stable orbits around the Sun up to an eraser of about 48 astronomical units.
The new computer model explains another oddity. Astronomers have suspected for 20 years that Neptune is moving out of its birthplace, based on the possible impact of small objects on it.
However, theorists wondered why Neptune stopped moving. "Neptune migrated until it encountered the edge of the protoplanetary disk, where it suddenly stopped," said Morbidelli, of the La Cote de l'Azur Observatory in France.
The details of the work can be found in the November XNUMX issue of the journal Nature.
Rodney Gomez of the National Observatory in Brazil provided an analysis of the new concept to Nature. In an email interview, Gomez told space.com that "Lewison and Morbidly make strong claims that their scenario is true."
Gumed did not take part in the work on the new visualization. However, in a separate paper submitted to the journal Icarus, Gomez collaborated with Levison and Morbidly to show that the region now occupied by the Kuiper Belt was previously desolate, otherwise Neptune might have migrated farther than it did.
Gomez said that finer computer simulations are needed to determine whether Neptune's influence is properly understood, but even if the Kuiper Belt mystery is solved, there is still more to understand.
In previous scenarios of the Solar System's history, it begins with a small, truncated protoplanetary disk, as depicted in the new simulation. However, limited observations of similar rings of gas and dust in young stars suggest they are wider, Gomez said.
"So, is the solar system a rare case?" he wonders. "This, I believe, will be a major issue in planetary science in the coming years."
