[Spitzer News] NASA Finds Extremely Hot Planet,
Makes First Exoplanet Weather Map
spitzer-news at lists.ipac.caltech.edu
spitzer-news at lists.ipac.caltech.edu
Wed May 9 11:43:22 PDT 2007
In this issue:
1) NASA Finds Extremely Hot Planet, Makes First Exoplanet Weather Map
2) Explore the Infrared Universe at Caltech's Bandorama
3) Spitzer Spies Jet-Setting Stars
4) Spitzer Learns About Carbon's Cosmic Life
NASA FINDS EXTREMELY HOT PLANET, MAKES FIRST EXOPLANET WEATHER MAP
Researchers using NASA's Spitzer Space Telescope have learned what the
weather is like on two distant, exotic worlds. One team of astronomers
used the infrared telescope to map temperature variations over the
surface of a giant gas planet, HD 189733b, revealing it likely is
whipped by roaring winds. Another team determined that the gas planet HD
149026b is the hottest yet discovered. Both findings appear May 9 in
"We have mapped the temperature variations across the entire surface of
a planet that is so far away, its light takes 60 years to reach us,"
said Heather Knutson of the Harvard-Smithsonian Center for Astrophysics
in Cambridge, Mass., lead author of the paper describing HD 189733b.
The two planets are "hot Jupiters" - sizzling, gas giant planets that
zip closely around their stars. Roughly 50 of the more than 200 known
planets outside our solar system, called exoplanets, are hot Jupiters.
Visible-light telescopes can detect these strange worlds and determine
certain characteristics, such as their sizes and orbits, but not much is
known about their atmospheres or what they look like.
Since 2005, Spitzer has been revolutionizing the study of exoplanets'
atmospheres by examining their infrared light, or heat. In one of the
new studies, Spitzer set its infrared eyes on HD 189733b, located 60
light-years away in the constellation Vulpecula. HD 189733b is the
closest known transiting planet, which means that it crosses in front
and behind its star when viewed from Earth. It races around its star
every 2.2 days.
Spitzer measured the infrared light coming from the planet as it circled
around its star, revealing its different faces. These infrared
measurements, comprising about a quarter of a million data points, were
then assembled into pole-to-pole strips, and, ultimately, used to map
the temperature of the entire surface of the cloudy, giant planet.
The observations reveal that temperatures on this balmy world are fairly
even, ranging from 650 degrees Celsius (1,200 Fahrenheit) on the dark
side to 930 degrees Celsius (1,700 Fahrenheit) on the sunlit side. HD
189733b, and all other hot Jupiters, are believed to be tidally locked
like our moon, so one side of the planet always faces the star. Since
the planet's overall temperature variation is mild, scientists believe
winds must be spreading the heat from its permanently sunlit side around
to its dark side. Such winds might rage across the surface at up to 9600
kilometers per hour (6,000 miles per hour). The jet streams on Earth
travel at 322 kilometers per hour (200 miles per hour).
"These hot Jupiter exoplanets are blasted by 20,000 times more energy
per second than Jupiter," said co-author David Charbonneau, also of the
Harvard-Smithsonian Center for Astrophysics. "Now we can see how these
planets deal with all that energy."
Also, HD 189733b has a warm spot 30 degrees east of "high noon," or the
point directly below the star. In other words, if the high-noon point
were in Seattle, the warm spot would be in Chicago. Assuming the planet
is tidally locked to its parent star, this implies that fierce winds are
In the second Spitzer study, astronomers led by Joseph Harrington of the
University of Central Florida in Orlando discovered that HD 149026b is a
scorching 2,038 degrees Celsius (3,700 Fahrenheit), even hotter than
some low-mass stars. Spitzer was able to calculate the temperature of
this transiting planet by observing the drop in infrared light that
occurs as it dips behind its star.
"This planet is like a chunk of hot coal in space," said Harrington.
"Because this planet is so hot, we believe its heat is not being spread
around. The day side is very hot, and the night side is probably much
HD 149026b is located 256 light-years away in the constellation
Hercules. It is the smallest and densest known transiting planet, with a
size similar to Saturn's and a core suspected to be 70 to 90 times the
mass of Earth. It speeds around its star every 2.9 days.
According to Harrington and his team, the oddball planet probably
reflects almost no starlight, instead absorbing all of the heat into its
fiery body. That means HD 149026b might be the blackest planet known, in
addition to the hottest.
"This planet is off the temperature scale that we expect for planets,"
said Drake Deming, a co-author of the paper, from NASA's Goddard Space
Flight Center, Greenbelt, Md.
NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer
Space Telescope mission for NASA's Science Mission Directorate,
Washington. Science operations are conducted at the Spitzer Science
Center at the California Institute of Technology, also in Pasadena.
For more information about the Spitzer Space Telescope, visit
www.spitzer.caltech.edu or http://www.nasa.gov/spitzer.
EXPLORE THE INFRARED UNIVERSE AT CALTECH'S BANDORAMA
Can't afford a ticket to space? Lift off for free from Caltech's Ramo
auditorium on May 11 and 12, 2007 at 8 p.m. with Bandorama -- a free
concert presented by the Caltech Jazz Bands and the Caltech-Occidental
Soar through star-forming regions, out beyond our Milky Way galaxy to
the edge of the known universe with spectacular images from NASA's
Spitzer Space Telescope. The soundtrack for this cosmic expedition is
Star Life, an original score written by concert band member Les Deutsch,
an alumnus of Caltech who now serves as Chief Technologist and Strategic
Planner for NASA's Jet Propulsion Laboratory's Interplanetary Network
Caltech is located at 1200 California Blvd. in Pasadena, Calif. For more
information on the event please visit
SPITZER SPIES JET-SETTING STARS
Rainbow-colored jets in the cosmic cloud BHR 71 point to a celestial
smash occurring 600 light-years away from Earth -- and NASA's Spitzer
Space Telescope provides an exclusive peek at the "jet-setting" stars
The hot, young-stars can be seen in the Spitzer image (middle panel) as
yellow spots with dual rainbow-colored jets shooting out of them -- one
from the top and one from the bottom of each star. The colors in the
jets represent infrared light: green reveals really hot hydrogen gas,
orange shows warm gas, and the wisps of red represent the coolest gas.
These infrared rainbows of color are exposed when shockwaves from the
stars violently smash into surrounding gas and dust.
"Spitzer offers a spectacular view of this region. In space, there are
only a handful of places where we can see the chemical effects of
stellar outflows on the surrounding cloud -- and we see that in this
Spitzer image," says Dr. Tyler Bourke of the Harvard-Smithsonian Center
for Astrophysics, Cambridge, Mass.
The gas closest to the hot young-stars is heated most because the
high-energy shockwaves collide into these particles with incredible
force. As the shockwaves travel away from the star, resistance from gas
and dust particles along the way reduces the shockwaves' momentum -- so
collisions with material further out are not as intense -- and gas is
not heated as much.
Because green gas toward the beginning of BHR 71's jets is hotter than
the orange gas near the middle, Bourke thinks that the cloud's
"starlets" are shooting off energy in regular bursts. He notes that if
these stars had only shot off one burst of energy, then the gas closest
to the star would be the coldest. The logic behind this is that closely
orbiting dust and gas would have more time to cool as the shockwaves
traveled further away from the star. In this scenario, the material
toward the middle of the jet would be warmer because shockwaves from the
burst would have traveled away from the star, and currently be colliding
with molecules that are further out.
"Astronomers believe that all young stars at this stage of evolution [or
development] produce jets. However, we don't always see these jets
because they need a dense environment -- with a lot of gas and dust --
to run into," says Bourke. "We also need infrared telescopes to measure
heat created when the jets' shockwaves collide with gas molecules."
For years, stars inside BHR 71 have evaded the prying eyes of
visible-light telescopes. In an optical image taken by the ground-based
Very Large Telescope (left panel), BHR 71 is just a large, black cloud.
A burst of yellow light toward the bottom of BHR 71 is the only
indication that jet-setting starlets may lurk inside.
Before the Spitzer observations, astronomers suspected that this optical
rupture was a hot young star's powerful jet breaking through the dense
structure. This theory was confirmed when scientists combined the
visible-light view of BHR 71 with Spitzer's infrared view (right panel).
In this composite, the visible-light jet overlaps exactly with a jet
spouting-out of the left star, in the infrared image.
The combination of views also exposes a "crowd" of stars that escaped
visible-light detection. Yellow dots scattered throughout the image are
young stars forming inside BHR 71. Spitzer also uncovered another
jet-setting star located just to the right of the powerful jet-setting
star seen in the visible light image.
Spitzer was able to see details that visible-light telescopes didn't,
because its infrared instruments are sensitive to "heat."
Bourke is the lead author of a paper on BHR 71, which is being prepared
for publication in the Astrophysical Journal.
SPITZER LEARNS ABOUT CARBON'S COSMIC LIFE
Astronomers may be one step closer to understanding how the ingredients
of life are processed in space, thanks to NASA's Spitzer Space
On Earth, the elements carbon and hydrogen dominate the chemistry of all
life. Because molecules called polycyclic aromatic hydrocarbons, or
PAHs, contain both of these elements and are abundant all over the
universe, many astronomers suspect that they may be among life's
building blocks. PAHs are also especially hardy molecules -- typically
found in hot, chaotic regions of space -- leading some to believe that
they could have survived the harsh environments of the planet's early
So, how do PAHs come to be? Astronomers may be one step closer to
solving this mystery, now that a team of scientists led by Dr. Greg
Sloan of Cornell University, Ithaca, N.Y., has detected many
predecessors of PAHs in a relatively cool region of space.
"One of the greatest mysteries in astrobiology is the question of what
happens to carbon before it is caught up in stars, planets, asteroids,
and comets. This finding brings us one step closer to answering that
question," says Sloan.
In the case of PAHs, "polycyclic" indicates that these molecules consist
of multiple loops of carbon atoms, while "aromatic" refers to the kinds
of strong chemical bonds that exist between the carbon atoms.
For years, astronomers believed that PAHs were the by-products of
another molecule. They suspected that the predecessors of PAHs contained
more delicate "aliphatic" carbon bonds. Because PAHs are typically found
in regions polluted with intense ultraviolet radiation, scientists
thought that harsh ultraviolet light might be responsible for breaking
the fragile aliphatic bonds. Astronomers predicted that the stronger
aromatic bonds of carbon and hydrogen atoms left over after the
ultraviolet zapping became PAHs.
Now, Spitzer's infrared spectrograph instrument has finally confirmed
this hypothesis by sensing many predecessors of PAHs -- molecules with
relatively fragile aliphatic bonds -- in a cool and tranquil region of
space. These molecules do not survive for very long in the hot, chaotic
cosmic environments where PAHs are usually found. Sloan suspects that
these molecules have yet to be processed by intense ultraviolet light
and become PAHs.
Astronomers agree that almost everything on Earth once came from a star.
A few minutes after the Big Bang, hydrogen and helium made up almost all
of the elements in the universe. Other elements -- including carbon --
were formed later through nuclear fusion in the cores of stars, and
ejected into space near the end of a star's life. Much of this material
spread across space as dust. By studying the organics in the dust and
how they are processed in space, scientists hope to understand how
planets like Earth and the life on it formed.
Sloan's paper on this finding will be published in a forthcoming issue
of the Astrophysical Journal.
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