These Mini-Neptunes Are Changing From Puffy Planets To Super-Earths
Scientists have observed a pair of exoplanets in the mini-Neptune category that are slowly losing their atmosphere and evolving into super-Earths.
Astronomers have reported the discovery of two 'mini-Neptune' planets that are slowly losing their atmosphere in space owing to the radiation from their star and are slowly turning into another class of exoplanets called super-Earths. To understand the significance of the latest research, one must first understand the idea behind these cosmic objects. Simply put, exoplanets are planets that orbit another star beyond Earth's solar system. So far, thousands of them have been discovered, and they come in all shapes and sizes with their own unique composition.
They've been divided across four categories — gas giants (usually the size of Jupiter and Saturn, or much larger), Neptunian (rocky planets similar to Neptune and Uranus), super-Earths (terrestrial planets that are larger than Earth but smaller than Neptune), and terrestrial (similar to Earth in size and composition). Further studies have led scientists to develop a new class called mini-Neptunes, which are smaller than Neptune but still bigger than Earth. They have a thick atmosphere made predominantly of Hydrogen and Helium. Late last year, astronomers spotted an object called M51-ULS-1b that might be the first exoplanet seen outside the Milky Way galaxy.
A new study claims to have observed two mini-Neptunes that are losing their atmosphere due to the X-rays and ultraviolet radiation coming from their star and are slowly turning into super-Earths. Now, barely a few planets that fall in the size bracket between mini-Neptunes and super-Earths have been detected so far, with scientists suspecting that mini-Neptunes are transforming into the super-Earths. Using the W. M. Keck Observatory's Near-Infrared Spectrograph, scientists studied a mini-Neptune in the TOI 560 star system that had gas leaving its atmosphere in the same fashion as "steam from a pot of boiling water." The team also used data from the Hubble Space Telescope to study another mini-Neptune in a similar atmosphere-losing process at a distance of about 73 light-years in the HD 63433 star system. The findings have been published in two separate papers in The Astronomical Journal.
Take, for example, Mars, whose atmosphere is being eaten away by the sun's radiation. The only way to make it habitable is to create a giant magnetic shield that blocks this radiation. Something similar is happening with the mini-Neptunes that astronauts have observed. While studying the mini-Neptune called TOI 560.01, scientists noticed that instead of gas blowing away from the planet, it was escaping towards the star it was orbiting. Likewise, the team observed two mini-Neptunes in the HD 63433 star system, but the one closer to its star didn't show any signs of Helium or Hydrogen ejection, leading scientists to believe that it may have already lost its atmosphere.
Scientists observed the pace of Helium leaving TOI 560.01 at about 20 kilometers per second and Hydrogen escaping away from HD 63433c at roughly 50 kilometers per second to detect the process of atmosphere erosion. In comparison, an international team of scientists recently reported the discovery of the first wandering stellar-mass black hole moving across the Milky Way galaxy at about 45 kilometers per second. The latest exoplanet discovery is remarkable because so far, scientists have only theorized that mini-Neptunes may have an evaporating atmosphere, but only now has the process been observed for the first time.