Hot, Dry and Cloudy Planet

Spitzer_ssc2007-04d_1024

spitzer_ssc2007-04d February 21st, 2007

Credit: NASA/JPL-Caltech/T. Pyle (SSC)

This artist's concept shows a cloudy Jupiter-like planet that orbits very close to its fiery hot star. NASA's Spitzer Space Telescope was recently used to capture spectra, or molecular fingerprints, of two "hot Jupiter" worlds like the one depicted here. This is the first time a spectrum has ever been obtained for an exoplanet, or a planet beyond our solar system.

The ground-breaking observations were made with Spitzer's spectrograph, which pries apart infrared light into its basic wavelengths, revealing the "fingerprints" of molecules imprinted inside. Spitzer studied two planets, HD 209458b and HD 189733b, both of which were found, surprisingly, to have no water in the tops of their atmospheres. The results suggest that the hot planets are socked in with dry, high clouds, which are obscuring water that lies underneath. In addition, HD209458b showed hints of silicates, suggesting that the high clouds on that planet contain very fine sand-like particles.

Capturing the spectra from the two hot-Jupiter planets was no easy feat. The planets cannot be distinguished from their stars and instead appear to telescopes as single blurs of light. One way to get around this is through what is known as the secondary eclipse technique. In this method, changes in the total light from a so-called transiting planet system are measured as a planet is eclipsed by its star, vanishing from our Earthly point of view. The dip in observed light can then be attributed to the planet alone.

This technique, first used by Spitzer in 2005 to directly detect the light from an exoplanet, currently only works at infrared wavelengths, where the differences in brightness between the planet and star are less, and the planet's light is easier to pick out. For example, if the experiment had been done in visible light, the star is so much brighter than the planet that the total light from the system would appear to be unchanged, even as the planet disappeared from view.

To capture spectra of the planets, Spitzer observed their secondary eclipses with its spectrograph. It took a spectrum of a star together with its planet, then, as the planet disappeared from view, a spectrum of just the star. By subtracting the spectrum of the star from the spectrum of the star and planet together, astronomers were able to determine the spectrum of the planet itself.

Provider: Spitzer Space Telescope

Image Source: https://www.spitzer.caltech.edu/image/ssc2007-04d-hot-dry-and-cloudy-planet

Curator: Spitzer Space Telescope, Pasadena, CA, USA

Image Use Policy: Public Domain

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Image Details

Image Type
Artwork
Subject - General
Planet > Type > Gas Giant
Planet > Feature > Atmosphere
Planet > Special Cases > Transiting
Planet > Special Cases > Hot Jupiter
Spitzer_ssc2007-04d_1280
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ID
ssc2007-04d
Subject Category
E.1.1.2   E.1.2.2   E.1.3.1   E.1.3.2  
Subject Name
Credits
NASA/JPL-Caltech/T. Pyle (SSC)
Release Date
2007-02-21
Lightyears
Redshift
Reference Url
https://www.spitzer.caltech.edu/image/ssc2007-04d-hot-dry-and-cloudy-planet
Type
Artwork
Image Quality
Good
Distance Notes
Facility
Instrument
Color Assignment
Band
Bandpass
Central Wavelength
Start Time
Integration Time
Dataset ID
Notes
Coordinate Frame
Equinox
Reference Value
Reference Dimension
Reference Pixel
Scale
Rotation
Coordinate System Projection:
Quality
FITS Header
Notes
Creator (Curator)
Spitzer Space Telescope
URL
http://www.spitzer.caltech.edu
Name
Spitzer Space Telescope
Email
Telephone
Address
1200 E. California Blvd.
City
Pasadena
State/Province
CA
Postal Code
91125
Country
USA
Rights
Public Domain
Publisher
Spitzer Science Center
Publisher ID
spitzer
Resource ID
ssc2007-04d.tif
Metadata Date
2021-08-04T07:32:03Z
Metadata Version
1.2
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