From NASA/ESA Hubble Telescope: “Hubble Detects Helium in the Atmosphere of an Exoplanet for the First Time”

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NASA/ESA Hubble Telescope

May 2, 2018

Jessica Spake
University of Exeter, Exeter, United Kingdom
jspake@astro.ex.ac.uk

David Sing
University of Exeter, Exeter, United Kingdom
011-44-13-9272-5652
sing@astro.ex.ac.uk

Mathias Jäger
ESA/Hubble, Garching, Germany
011-49-1-76-6239-7500
mjaeger@partner.eso.org

Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
410-338-4514
villard@stsci.edu

1
Ballooning Atmosphere Extends Tens of Thousands of Miles Above a Gas Giant Planet.

There may be no shortage of balloon-filled birthday parties or people with silly high-pitched voices on the planet WASP-107b. That’s because NASA’s Hubble Space Telescope was used to detect helium in the atmosphere for the first time ever on a world outside of our solar system. The discovery demonstrates the ability to use infrared spectra to study exoplanet atmospheres.

Though as far back as 2000 helium was predicted to be one of the most readily-detectable gases on giant exoplanets, until now helium had not been found — despite searches for it. Helium was first discovered on the Sun, and is the second-most common element in the universe after hydrogen. It’s one of the main constituents of the planets Jupiter and Saturn.

An international team of astronomers led by Jessica Spake of the University of Exeter, UK, used Hubble’s Wide Field Camera 3 to discover helium. The atmosphere of WASP-107b must stretch tens of thousands of miles out into space. This is the first time that such an extended atmosphere has been discovered at infrared wavelengths.

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Astronomers using NASA’s Hubble Space Telescope have detected helium in the atmosphere of the exoplanet WASP-107b. This is the first time this element has been detected in the atmosphere of a planet outside the solar system. The discovery demonstrates the ability to use infrared spectra to study exoplanet extended atmospheres.

The international team of astronomers, led by Jessica Spake, a PhD student at the University of Exeter in the UK, used Hubble’s Wide Field Camera 3 to discover helium in the atmosphere of the exoplanet WASP-107b. This is the first detection of its kind.

NASA/ESA Hubble WFC3

Spake explained the importance of the discovery: “Helium is the second-most common element in the universe after hydrogen. It is also one of the main constituents of the planets Jupiter and Saturn in our solar system. However, up until now helium had not been detected on exoplanets — despite searches for it.”

The team made the detection by analyzing the infrared spectrum of the atmosphere of WASP-107b. Previous detections of extended exoplanet atmospheres have been made by studying the spectrum at ultraviolet and optical wavelengths; this detection therefore demonstrates that exoplanet atmospheres can also be studied at longer wavelengths.

The measurement of an exoplanet’s atmosphere is performed when the planet passes in front of its host star. A tiny portion of the star’s light passes through the exoplanet’s atmosphere, leaving detectable fingerprints in the spectrum of the star. The larger the amount of an element present in the atmosphere, the easier the detection becomes.

“The strong signal from helium we measured demonstrates a new technique to study upper layers of exoplanet atmospheres in a wider range of planets,” said Spake. “Current methods, which use ultraviolet light, are limited to the closest exoplanets. We know there is helium in the Earth’s upper atmosphere and this new technique may help us to detect atmospheres around Earth-sized exoplanets — which is very difficult with current technology.”

WASP-107b is one of the lowest density planets known: While the planet is about the same size as Jupiter, it has only 12 percent of Jupiter’s mass. The exoplanet is about 200 light-years from Earth and takes less than six days to orbit its host star.

The amount of helium detected in the atmosphere of WASP-107b is so large that its upper atmosphere must extend tens of thousands of miles out into space. This also makes it the first time that an extended atmosphere has been discovered at infrared wavelengths.

Since its atmosphere is so extended, the planet is losing a significant amount of its atmospheric gases into space — between about 0.1 percent to 4 percent of its atmosphere’s total mass every billion years.

Stellar radiation has a significant effect on the rate at which a planet’s atmosphere escapes. The star WASP-107 is highly active, supporting the atmospheric loss. As the atmosphere absorbs radiation it heats up, so the gas rapidly expands and escapes more quickly into space.

As far back as the year 2000, it was predicted that helium would be one of the most readily-detectable gases on giant exoplanets, but until now, searches were unsuccessful.

David Sing, co-author of the study also from the University of Exeter, concluded: “Our new method, along with future telescopes such as NASA’s James Webb Space Telescope, will allow us to analyze atmospheres of exoplanets in far greater detail than ever before.”

The team’s study appears on May 2, 2018, in the online issue of science journal Nature.

The international team of astronomers in this study consists of J. Spake (University of Exeter, Exeter, UK), D. Sing (University of Exeter, Exeter, UK; Johns Hopkins University, Baltimore, Maryland), T. Evans (University of Exeter, UK), A. Oklopčić (Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts), V. Bourrier (University Geneva Observatory, Sauverny, Switzerland), L. Kreidberg (Harvard Society of Fellows and Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts), B. Rackham (University of Arizona, Tucson, Arizona), J. Irwin (Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts), D. Ehrenreich and A. Wyttenbach (University of Geneva Observatory, Sauverny, Switzerland), H. Wakeford (Space Telescope Science Institute, Baltimore, Maryland), Y. Zhou (University of Arizona, Tucson, Arizona), K. Chubb (University College London, London, UK), N. Nikolov and J. Goyal (University of Exeter, Exeter, UK), G. Henry and M. Williamson (Tennessee State University, Nashville, Tennessee), S. Blumenthal (Space Telescope Science Institute, Baltimore, Maryland), D. Anderson and C. Hellier (Keele University, Staffordshire, UK), D. Charbonneau (Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts), S. Udry (University of Geneva Observatory, Sauverny, Switzerland), and N. Madhusudhan (University of Cambridge, Cambridge, UK).

See the full article here .

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The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

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