Phoenix, the planet that puzzles scientists: It “isn’t evolving the way we thought”
Astronomers have discovered a “weird” exoplanet that belongs to a rare group known as “hot Neptunes” that should have lost all of its atmosphere.
In January 1992, a revolution took place in the field of astronomy, with the discovery of the first exoplanets (a planet outside our solar system) confirmed around another star announced by Alexander Wolszczan and Dale Frail. That star happened to be a pulsar, which was constantly blasting the newly discovered worlds with radiation meaning they cannot support organic life. However, “if you can find planets around a neutron star, planets have to be basically everywhere,” Wolszczan said.
And so it was, and a few years later a planet half the size of Juptier was discovered orbiting a star similar to our Sun. The discoverers of this exoplanet, named 51 Pegasi b (later known as Dimidio), were Didier Queloz and Michel Mayor. As the years roll on, the confirmation of new exoplanets has not stopped growing and the speed of discovery has quickened.
A couple of years ago, the confirmed number exceeded 5,000, according to the National Aeronautics and Space Administration (NASA). “Each one of them is a new world, a brand-new planet. I get excited about every one because we don’t know anything about them,” said Jessie Christiansen, chief scientist of the archive and scientific researcher at the NASA Exoplanetary Sciences Institute.
One of the lastest to be discovered has been named Phoenix, and preserves its “puffy” atmosphere despite the extreme radiation it receives from its nearby star, which is a red giant. A discovery that, due to its characteristics, calls into question what is known about how exoplanets age and die. In fact, it has been nicknamed the Phoenix for its ability to survive the intense energy to which it is exposed.
The specialized magazine The Astronomical Journal published this discovery, in an article in which the researchers assure that it should have been reduced to bare rock by the intense radiation of its large host star. However, “this planet isn’t evolving the way we thought it would. It appears to have a much bigger, less dense atmosphere than we expected for these systems”, explains Sam Grunblatt, astrophysicist at Johns Hopkins University.
Another 'hot Neptune'
The recently discovered exoplanet belongs to a category of not very common worlds known as ‘hot Neptunes’, because they share many characteristics of the icy planet in our solar system, despite being closer to their host stars and are much warmer. Phoenix is 6.2 times the size of Earth, completes an orbit around its star every 4.2 days and is six times closer to its host star than Mercury is to the Sun.
According to experts, this exoplanet is 60 times less dense than the highest mass ‘hot Neptune’ that has been discovered to date, and it is estimated that it will not survive more than 100 million years .
“It’s the smallest planet we’ve ever found around one of these red giants, and probably the lowest mass planet orbiting a [red] giant star we’ve ever seen. That’s why it looks really weird,” explains the expert. “We don’t know why it still has an atmosphere when other ‘hot Neptunes’ that are much smaller and much denser seem to be losing their atmospheres in much less extreme environments.”