Hubble Telescope Discovers New Planet GJ 3470b ‘Evaporating’ At Record Speed

Planets have been here long before mankind and will be here long after, but one planet may be disappearing faster than most.

Scientists who study planets beyond our own solar system have discovered that GJ 3470b, a Neptune-sized planet, is “evaporating” much faster than other similar-sized bodies. It is apparently vanishing at a rate 100 times quicker than GJ 436b, which is roughly the same size, Phys.org noted.

Published in Astronomy & Astrophysics, the astronomers' findings could be a breakthrough in the study of how planets evolve. David Sing, Bloomberg distinguished professor at Johns Hopkins and co-author of the study, revealed that this new discovery could be evidence that planets can lose a significant portion of their mass with time. And at the rate GJ 3470b is losing its mass, half of it could vanish in a few billion years.

The program leading this study is Panchromatic Comparative Exoplanet Treasury (PanCET), the largest exoplanet observation program to be run with NASA's Hubble Space Telescope. The NASA program, which is led by Sing, aims to measure the atmospheres of 20 exoplanets while they orbit their stars with the use of optical, ultraviolet and infrared light.

The scientists also looked into how planets lose their mass through evaporation. Planets like Earth and Jupiter travel more closely to their stars and are therefore hotter. This results in the outermost layer of their atmospheres disappearing due to evaporation.

However, unlike Jupiter-sized and Earth-sized exoplanets, medium exoplanets that are about four times larger than Earth can rarely be observed. Scientists believe that these Neptune-sized planets lose most of their atmospheres to evaporation, so they eventually become smaller bodies.

But research has not been as extensive as the only way to study them is by UV light. This hinders scientists from observing nearby stars no greater than 150 light-years away from Earth. GJ 3470b is 96 light-years away and orbits around a red dwarf star in the general direction of the constellation Cancer.

Scientists found that GJ 3470b had lost significantly more mass and had a smaller exosphere than GJ 436b. This is because the former received a stronger radiation blast from its host star, on top of it having a lower density.

GJ 3470b's lower density prevents it from being able to gravitationally hang on to the heated atmosphere. In addition, the star hosting GJ 3470b is only 2 billion years old, which is several billion years younger than the one hosting GJ 436b. A younger star is more powerful and active, so it contains more radiation to heat up the planet's atmosphere.

Sing and his team estimated that around 35 percent of GJ 3470b's total mass may have already vanished. And at this rate, the planet would be stripped of its gas in a few billion years, leaving only its rocky core behind.

“We're starting to better understand how planets are shaped and what properties influence their overall makeup,” Sing said. “Our goal with this study and the overarching PanCET program is to take a broad look at these planets' atmospheres to determine how each planet is affected by its own environment. By comparing different planets, we can start piecing together the larger picture in how they evolve.”