Recent telescope images have revealed that a small dwarf planet far away in our solar system has a dense ring around it, not a moon. Scientists are perplexed by the discovery and are trying to discover the reason for formation.
The planet Quaoar is one of about 3,000 small planets orbiting the sun beyond Neptune and, at just over 1,000 kilometers wide, is the seventh largest.
Observations of Quaoar taken between 2018 and 2021 revealed that the planet has a ring farther from it than scientists believed possible, according to a press release from the European Space Agency (ESA), which used ground-based telescopes and a new space probe. to collect the data.
Based on conventional thinking, all the material that makes up Quaoar’s dense ring should have condensed to form a small moon, but it didn’t.
“Early results suggest that frigid temperatures on Quaoar may play a role in preventing ice particles from sticking together, but further investigation is needed,” according to the press release.
Beyond the Roche limit
Prior to these new Quaoar observations, scientists believed it was impossible for planets to form rings beyond a certain distance. It’s a generally accepted rule of celestial mechanics, that material in orbit around a planet will form a spherical object – or a moon – if it’s far enough away from the planet.
However, that moon will be torn apart if it approaches what’s called the “Roche limit,” a point at which the planet’s forces would be stronger than the gravity holding the moon together.
All of the rings around Saturn, for example, are within the planet’s Roche boundary. What’s intriguing about Quaoar, however, is that its ring lies well beyond Roche’s boundary, in an area where material should form a moon.
“As a result of our observations, the classical notion that dense rings survive only within the Roche limit of a planetary body must be completely revised,” Giovanni Bruno of the INAF Astrophysical Observatory in Catania, Italy, said in a statement.
How to study a small planet
Collecting the data that revealed Quaoar’s ring was in itself cause for celebration. Due to the planet’s small size and distance from Earth, the researchers wanted to observe it using an “occultation” – a means of observing a planet expecting it to be essentially illuminated by a star.
This can be an extremely difficult process, according to the ESA, because the telescope, planet and star must all be in perfect alignment. This observation was made possible by the space agency’s recent efforts to provide an unprecedentedly detailed map of the stars.
The Cheops telescope was also used, which was launched in 2019. Cheops normally studies exoplanets or bodies that lie outside Earth’s solar system.
In this case, the device took aim at the closest target of Quaoar, which orbits the Sun even further than Neptune — about 44 times farther than Earth’s orbit.
“I was a little skeptical about the possibility of doing this with Cheops,” said Isabella Pagano, director of the Astrophysical Observatory of Catania, in a statement.
The observation worked, and Cheops marked the first of its kind – an occultation of one of the most distant planets in our solar system by a space telescope.
The researchers then compared the data collected by Cheops with observations from ground-based telescopes, leading to their surprising revelation.
“When we put it all together, we saw dips in brightness that were not caused by Quaoar, but that pointed to the presence of material in a circular orbit around it. The moment we saw that, we said, ‘Okay, we’re seeing a ring around Quaoar,’” said Bruno Morgado, a professor at the Federal University of Rio de Janeiro, who led the analysis.
Theorists are now at work trying to guess how Quaoar’s ring survived.
Source: CNN Brasil
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