The Language of Planetary Light

Spitzer_ssc2005-09a_1024

spitzer_ssc2005-09a March 22nd, 2005

Credit: NASA/JPL-Caltech/D. Charbonneau (Harvard-Smithsonian CfA) and D. Deming (Goddard Space Flight Center)

This graph of data from NASA's Spitzer Space telescope shows changes in the infrared light output of two star-planet systems (one above, one below) located hundreds of light-years away. The data were taken while the planets, called HD 209458b and TrES-1, disappeared behind their stars in what is called a "secondary eclipse." The dip seen in the center of each graph represents the time when the planets were eclipsed, and tells astronomers exactly how much light they emit.

Why a secondary eclipse? When a planet transits, or passes in front of, its star, it partially blocks the light of the star. When the planet swings around behind the star, the star completely blocks its light. This drop in total light can be measured to determine the amount of light coming from just the planet.

Why infrared? In visible light, the glare of a star overwhelms its planetary companion and the little light the planet reflects. In infrared, a star shines less brightly, and its planet gives off its own internal light, or heat radiation, making the planet easier to detect.

By observing these secondary eclipses at different infrared wavelengths, astronomers can obtain the planet's temperature, and, in the future, they may be able to pick out chemicals sprinkled throughout a planet's atmosphere. The technique also reveals whether a planet's orbit is elongated or circular.

This strategy will not work for all known extrasolar planets. It is ideally suited to study those Jupiter-sized planets previously discovered to cross, or transit, between us and the Sun-like stars they orbit, out to distances of 500 light-years. NASA's Spitzer Space Telescope was the first to successfully employ this technique.

The data of HD 209458b were taken by Spitzer's multiband imaging photometer using the 24-micron array. The data of TrES-1 were taken by Spitzer's infrared array camera using the 8-micron array.

Provider: Spitzer Space Telescope

Image Source: http://www.spitzer.caltech.edu/images/81-ssc2005-09a-The-Language-of-Planetary-Light

Curator: Spitzer Space Telescope, Pasadena, CA, USA

Image Use Policy: http://www.spitzer.caltech.edu/info/18-Image-Use-Policy

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Image Details

Image Type
Chart
Object Name
HD 209458b TrES-1
Subject - Local Universe
Star > Circumstellar Material > Planetary System
Planet > Type > Gas Giant
Planet > Special Cases > Transiting
Planet > Special Cases > Hot Jupiter

Distance

Universescale1
153 light years

Position Details

Position (ICRS)
RA = 19h 4m 9.8s
DEC = 36° 37’ 57.0”
Constellation
Lyra

Color Mapping

  Telescope Spectral Band Wavelength
Spitzer (IRAC) Infrared (Mid-IR) 8.0 µm
Spitzer (MIPS) Infrared (Mid-IR) 24.0 µm
Entries correspond to time sequences plotted for two separate objects
Spectrum_ir1
Spitzer_ssc2005-09a_1280
×
ID
ssc2005-09a
Subject Category
C.3.7.1.   C.1.1.2.   C.1.3.1.   C.1.3.2.  
Subject Name
HD 209458b, TrES-1
Credits
NASA/JPL-Caltech/D. Charbonneau (Harvard-Smithsonian CfA) and D. Deming (Goddard Space Flight Center)
Release Date
2005-03-22
Lightyears
153
Redshift
Reference Url
http://www.spitzer.caltech.edu/images/81-ssc2005-09a-The-Language-of-Planetary-Light
Type
Chart
Image Quality
Good
Distance Notes
Distance refers to TrES-1 only
Facility
Spitzer, Spitzer
Instrument
IRAC, MIPS
Color Assignment
Band
Infrared, Infrared
Bandpass
Mid-IR, Mid-IR
Central Wavelength
8000, 24000
Start Time
Integration Time
Dataset ID
Notes
E
Coordinate Frame
ICRS
Equinox
Reference Value
286.04083333, 36.63250000
Reference Dimension
Reference Pixel
Scale
Rotation
Coordinate System Projection:
Quality
Position
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
http://www.spitzer.caltech.edu/info/18-Image-Use-Policy
Publisher
Spitzer Science Center
Publisher ID
spitzer
Resource ID
ssc2005-09a.tif
Metadata Date
2018-01-10
Metadata Version
1.1
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Detailed color mapping information coming soon...

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Universescalefull
153 light years

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