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Astronomers have spotted a strange exoplanet, the first of its kind, meaning a planet orbiting the solar system. Exoplanet HR 5183b, a gas giant representing three times the mass of Jupiter, pivots around the star of its star in a distant trajectory in the shape of an egg that oscillates between the sun and its near. By way of comparison, if HR 5183b were part of our solar system, its orbit would take it from the asteroid belt to that of Neptune, the farthest planet in our sun.
The planet is particularly unique considering what we know about solar systems. Conventional wisdom and evidence of observation indicate that quasi-circular orbits, like those occupied by the planets of our solar system (including the Earth), are the most stable in the long term and are therefore most often observed. in mature solar systems. If the planets oscillated enormously in their orbit, like the HR 5183 b, collisions would be common; it is unclear whether other planets are orbiting the parent star HR 5183.
The planets of the sun – and the proto-planets that preceded them – may have had much more chaotic elliptical orbits in the early solar system. Namely: There are more than 4 billion years ago, the Earth was hit by a body the size of Mars, called Theia. Due to the stable orbits of the bodies of the solar system, such massive collisions are (fortunately) no longer possible.
These results will soon be published in a study of the journal Astronomical Journal. Other giant planets with orbits like fronds were found around other stars in different solar systems, but none of these worlds were located on the periphery of their star systems like this- this.
"This planet does not look like the planets of our solar system, but even more so, it does not look like any other exoplanet we've discovered so far," said Sarah Blunt, lead author of the study that will be published shortly, in a press release. . "The other planets detected far from their stars usually have very low eccentricities, which means that their orbits are more circular."
Blunt added that this planet is so unique, it "speaks of some difference in the way it has formed or evolved compared to other planets".
Co-author Michael Endl of McDonald Observatory accepted.
"This new exoplanet is extreme and extremely interesting in many ways," he said in a statement. "It has a long record orbital period of more than 50 years, which is much longer than for other planets detected by this technique, and it orbits its host star into a very elongated egg-shaped orbit."
The researchers discovered the exoplanet using the radial velocity method, a discovery method that identifies new worlds by analyzing how their parent stars "flicker" in response to the gravitational tugs of these planets. Endl said: "Something dramatic must have happened to change the shape of its orbit."
Since the 1990s, astronomers have been observing HR 5183, the parent star of the planet. The planet is said to surround its star every 45 to 100 years or so. HR 5183 b spends most of its time strolling in the outer part of the planetary system of its star, then accelerates and slings around its star, according to Kepler's laws on planetary motions.
"For nearly 20 years, our data has shown no sign of a global companion," Endl said. "And then we observed the" sling "that lasted only about two years.
It is strange to imagine a massive planet around his star, like a comet. When asked what this solar system might look like, Avi Loeb, director of the Harvard Astronomy Department, told Salon by e-mail: "For a planet to be launched on an orbit also elongated from an initially circular orbit, it must cross the orbit. from another giant planet or from a passing star. "
As for why this never happened in our own solar system, Loeb said the orbits of Jupiter and Saturn do not come close enough for Jupiter to give Saturn an attractive kick.
"The gravitational force when the two planets meet must exceed the force that keeps the planet on which the ball is resting in a circular orbit around the Sun," Loeb said. "Since the Sun is a thousand times larger than Jupiter, the disturbed planet must pass very close to the struck planet."
He added: "If a passing star gives the jolt, the passage could be at a distance comparable to the separation of the planet struck from its host star."
According to Endl, we generally think that the planet is formed in circular orbits, but "a close encounter with another gigantic planet could have thrown it on its path lengthened around the star".
The researchers said that this planet reiterates the lack of understanding we have of planets outside our solar system. Before 1995, the year of the discovery of the first exoplanet, we did not even know if there were planets in other solar systems. Nearly two decades later, 4,000 exoplanets were discovered.
"To understand the planetary systems of our galaxy, it is necessary to find and study examples of the full range of possible systems," said Phillip MacQueen, chief technology officer and observer at the McDonald Observatory. for planet search, in a statement. "Although space vehicles have found thousands of systems, it is unlikely that a system like the HR 5183 will be detected by previous or current spacecraft."
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