Hubble Detects Distant Planet Disappearing at Record Speed

Hubble finds far-away planet vanishing at record speed. This discovery will be essential for astronomers to understand how planets evolve.
Mario L. Major

Exoplanets--our distant cousins who look like us, and more importantly, offer a glimpse of our own fate many years into the future. From the ultrahot, vaporizing variety, to those whose conditions could support life similar to that found on Earth, each study offers more clues.

Scientists are putting the Hubble Space Telescope to work in examining the speed and distance at which planets are orbiting their stars. Their efforts have produced a recent study which is part of an ambitious program, the Panchromatic Comparative Exoplanet Treasury (PanCET).

No small endeavor, PanCET represents the largest exoplanet study program in the history of the Hubble Space Telescope's life.

The program involves an exhaustive measurement of 20 orbiting exoplanets: a combination of (1) optical, (2) infrared and (3) ultraviolet lights are used to measure their atmospheres. 

Professor David Sing, Bloomberg Distinguished Professor at Johns Hopkins University and an author on the study, led the team, which turned up with a very surprising find.

The Vanishing Exoplanet

The discovery was of a not-too-distant exoplanet, GJ 3470b, an exoplanet which is located roughly 97 light-years away from our planet, and which is about the size of the planet Neptune. 

Hubble Detects Distant Planet Disappearing at Record Speed
Source: NASA, ESA, and D. Player (STScI)

The evaporation rate, specifically, startled the scientists: it is occurring at a rate 100 times faster than GJ 436b, a previously discovered of roughly the same size. The scientists set out to understand why this loss of mass is happening at such a rapid rate.

Professor Sing explained how the behavior of the planet reveals many clues about the fate of many other planets the scientists are currently studying:

“This is the smoking gun that planets can lose a significant fraction of their entire mass. GJ 3470b is losing more of its mass than any other planet we have seen so far; in only a few billion years from now, half of the planet may be gone."

A Rare Opportunity

Beyond helping to understand the role of evaporation in a planetary mass loss, the project also offers an opportunity to examine the phenomenon in relatively larger Neptune-sized exoplanets. 

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They believe that mainly due to its low density, the exoplanet has already lost about 35% of its total mass.

The team also had the advantage of observing a relatively closer exoskeleton.

Generally, witnessing this kind of activity, due to the limitations of existing technology or interstellar material obscuring the view, is not possible unless the exoskeleton in question is within a range of 150 light-years.    


“We’re starting to better understand how planets are shaped and what properties influence their overall makeup,” Sing explained.

“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.”

Details about the study appear in a paper, titled "Hubble PanCET: an extended upper atmosphere of neutral hydrogen around the warm Neptune GJ 3470b", which was published in the Astronomy and Physics journal.