Nav: Home

Hubble reveals diversity of exoplanet atmosphere

December 14, 2015

Astronomers have used the NASA/ESA Hubble Space Telescope and the NASA Spitzer Space Telescope to study the atmospheres of ten hot, Jupiter-sized exoplanets in detail, the largest number of such planets ever studied. The team was able to discover why some of these worlds seem to have less water than expected -- a long-standing mystery. The results are published in Nature.

To date, astronomers have discovered nearly 2000 planets orbiting other stars. Some of these planets are known as hot Jupiters, hot, gaseous planets with characteristics similar to those of Jupiter. They orbit very close to their stars, making their surface hot, and the planets tricky to study in detail without being overwhelmed by bright starlight.

Due to this difficulty, Hubble has only explored a handful of hot Jupiters in the past, across a limited wavelength range. These initial studies have found several planets to hold less water than expected opo1436a , opo1354a .

Now, an international team of astronomers has tackled the problem by making the largest ever study of hot Jupiters, exploring and comparing ten such planets in a bid to understand their atmospheres [1]. Only three of these planetary atmospheres had previously been studied in detail; this new sample forms the largest ever spectroscopic catalogue of exoplanet atmospheres.

The team used multiple observations from both the NASA/ESA Hubble Space Telescope and NASA's Spitzer Space Telescope. Using the power of both telescopes allowed the team to study the planets, which are of various masses, sizes, and temperatures, across an unprecedented range of wavelengths [2].

"I'm really excited to finally 'see' this wide group of planets together, as this is the first time we've had sufficient wavelength coverage to be able to compare multiple features from one planet to another," says David Sing of the University of Exeter, UK, lead author of the new paper. "We found the planetary atmospheres to be much more diverse than we expected."

All of the planets have a favourable orbit that brings them between their parent star and Earth. As the exoplanet passes in front of its host star, as seen from Earth, some of this starlight travels through the planet's outer atmosphere. "The atmosphere leaves its unique fingerprint on the starlight, which we can study when the light reaches us," explains co-author Hannah Wakeford, now at NASA Goddard Space Flight Center, USA.

These fingerprints allowed the team to extract the signatures from various elements and molecules -- including water -- and to distinguish between cloudy and cloud-free exoplanets, a property that could explain the missing water mystery.

The team's models revealed that, while apparently cloud-free exoplanets showed strong signs of water, the atmospheres of those hot Jupiters with faint water signals also contained clouds and haze -- both of which are known to hide water from view. Mystery solved!

"The alternative to this is that planets form in an environment deprived of water -- but this would require us to completely rethink our current theories of how planets are born," explained co-author Jonathan Fortney of the University of California, Santa Cruz, USA. "Our results have ruled out the dry scenario, and strongly suggest that it's simply clouds hiding the water from prying eyes."

The study of exoplanetary atmospheres is currently in its infancy, with only a handful of observations taken so far. Hubble's successor, the James Webb Space Telescope , will open a new infrared window on the study of exoplanets and their atmospheres.
-end-
Notes

[1] To date, studies of exoplanet atmospheres have been dominated by a small number of well-studied planets. The team used Hubble and Spitzer observations of two such planets, HD 209458b heic0303, opo0707b and HD 189733b heic1312, heic0720a, and used Hubble to observe eight other exoplanets -- WASP-6b, WASP-12b, WASP-17b, WASP-19b, WASP-31b, WASP-39b, HAT-P-1b, HAT-P-12b. These planets have a broad range of physical parameters.

[2] The observations spanned from the ultraviolet (0.3 micrometres) to the mid-infrared (4.5 micrometres).

More information

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

This research was presented in a paper entitled 'A continuum from clear to cloudy hot-Jupiter exoplanets', to appear in the journal Nature on Dec. 14, 2015.

The international team of astronomers in this study consists of David K. Sing (University of Exeter, UK), Jonathan J. Fortney (University of California, Santa Cruz; USA), Nikolay Nikolov (University of Exeter, UK), Hannah R. Wakeford (University of Exeter, UK), Tiffany Kataria (University of Exeter, UK), Thomas M. Evans (University of Exeter, UK), Suzanne Aigrain (University of Oxford, UK), Gilda E. Ballester (University of Arizona, USA), Adam S. Burrows (Princeton University, USA), Drake Deming (University of Maryland, USA), Jean-Michel Désert (University of Colorado, USA), Neale P. Gibson (Queen's University Belfast, UK), Gregory W. Henry (Tennessee State University, USA), Catherine M. Huitson (University of Colorado, USA), Heather A. Knutson (California Institute of Technology, USA), Alain Lecavelier des Etangs (CNRS, France), Frederic Pont (University of Exeter, UK), Adam P. Showman (University of Arizona, USA), Alfred Vidal-Madjar (CNRS, France), Michael H. Williamson (Tennessee State University, USA), Paul A. Wilson (CNRS, France).

Image credit: ESA/Hubble & NASA

Links

Contacts

David Sing
sing@astro.ex.ac.uk
44-1392725652
University of Exeter
Exeter, UK

Hannah Wakeford
hannah.wakeford@nasa.gov
1-3012867975
NASA Goddard Space Flight Center
Greenbelt, USA

Jonathan Fortney
jfortney@ucsc.edu
1-8315027285
University of California Santa Cruz
Santa Cruz, USA

Mathias Jaeger
ESA/Hubble, Public Information Officer
mjaeger@partner.eso.org
49-176-62397500
Garching, Germany

ESA/Hubble Information Centre

Related Planets Articles:

How planets may form after dust sticks together
Scientists may have figured out how dust particles can stick together to form planets, according to a Rutgers co-authored study that may also help to improve industrial processes.
Planets around a black hole?
Theoreticians in two different fields defied the common knowledge that planets orbit stars like the Sun.
The rare molecule weighing in on the birth of planets
Astronomers using one of the most advanced radio telescopes have discovered a rare molecule in the dust and gas disc around a young star -- and it may provide an answer to one of the conundrums facing astronomers.
How many Earth-like planets are around sun-like stars?
A new study provides the most accurate estimate of the frequency that planets that are similar to Earth in size and in distance from their host star occur around stars similar to our Sun.
Dead planets can 'broadcast' for up to a billion years
Astronomers are planning to hunt for cores of exoplanets around white dwarf stars by 'tuning in' to the radio waves that they emit.
The sun follows the rhythm of the planets
One of the big questions in solar physics is why the sun's activity follows a regular cycle of 11 years.
Five planets revealed after 20 years of observation
To confirm the presence of a planet, it is necessary to wait until it has made one or more revolutions around its star.
Icy giant planets in the laboratory
Giant planets like Neptune may contain much less free hydrogen than previously assumed.
New NASA mission could find more than 1,000 planets
A NASA telescope that will give humans the largest, deepest, clearest picture of the universe since the Hubble Space Telescope could find as many as 1,400 new planets outside Earth's solar system, new research suggests.
Giant planets around young star raise questions about how planets form
Researchers have identified a young star with four Jupiter and Saturn-sized planets in orbit around it, the first time that so many massive planets have been detected in such a young system.
More Planets News and Planets Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Uncharted
There's so much we've yet to explore–from outer space to the deep ocean to our own brains. This hour, Manoush goes on a journey through those uncharted places, led by TED Science Curator David Biello.
Now Playing: Science for the People

#556 The Power of Friendship
It's 2020 and times are tough. Maybe some of us are learning about social distancing the hard way. Maybe we just are all a little anxious. No matter what, we could probably use a friend. But what is a friend, exactly? And why do we need them so much? This week host Bethany Brookshire speaks with Lydia Denworth, author of the new book "Friendship: The Evolution, Biology, and Extraordinary Power of Life's Fundamental Bond". This episode is hosted by Bethany Brookshire, science writer from Science News.
Now Playing: Radiolab

Dispatch 1: Numbers
In a recent Radiolab group huddle, with coronavirus unraveling around us, the team found themselves grappling with all the numbers connected to COVID-19. Our new found 6 foot bubbles of personal space. Three percent mortality rate (or 1, or 2, or 4). 7,000 cases (now, much much more). So in the wake of that meeting, we reflect on the onslaught of numbers - what they reveal, and what they hide.  Support Radiolab today at Radiolab.org/donate.