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MIt discovers the hottest planet ever at 3,700 degrees Fahrenheit
:: 11 May, 2007
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 Nature.
"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 blowing eastward.
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 colder."
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.
News Inside News:
About the Object -Object Name: HD 189733b
Object Type: Exoplanet
Position (J2000): RA: 20 00 43 Dec: +22 42 39
Distance: 63 light-years
Constellation: Vulpecula
About the Data -Image Credit: NASA/JPL-Caltech/H. Knutson (Harvard-Smithsonian CfA)
Instrument: IRAC
Wavelength: 8.0 microns
Exposure Date: Oct 28 and 29, 2006
Exposure Time: 33 hours
Release Date: May 9,2007
Observers-
H. Knutson (Harvard-Smithsonian CfA)
David Charbonneau (Harvard-Smithsonian CfA)
Lori E. Allen (Harvard-Smithsonian CfA)
Jonathan J. Fortney (NASA Ames Research Center)
Eric Agol (University of Washington, Seattle)
Nicolas B. Cowan (University of Washington, Seattle)
Adam P. Showman (University of Arizona)
Curtis S. Cooper (University of Arizona)
S. Thomas Megeath (University of Toledo)
About the Object -
Object Name: HD 149026b
Object Type: Exoplanet
Position (J2000): RA: 16 30 29 Dec: +38 20 50
Distance: 256 light-years
Constellation: Hercules
About the Data Image -
Credit: NASA/ JPL-Caltech/J. Harrington (Univ. of Central Florida)
Instrument: IRAC
Wavelength: 8.0 microns
Exposure Date: August 24, 2005
Exposure Time: 6 hours
Release Date: May 9,2007
Observers Joseph Harrington (University of Central Florida)
Statia Luszcz (University of California Berkeley)
Drake Deming (Goddard Space Flight Center)
Sara Seager (Carnegie Institute of Washington)
L. Jeremy Richardson (Goddard Space Flight Center)
About Other hottest Venus-
Venus (Greek: Aphrodite; Babylonian: Ishtar) is the goddess of love and beauty. The planet is so named probably because it is the brightest of the planets known to the ancients. (With a few exceptions, the surface features on Venus are named for female figures.)
Venus has been known since prehistoric times. It is the brightest object in the sky except for the Sun and the Moon. Like Mercury, it was popularly thought to be two separate bodies: Eosphorus as the morning star and Hesperus as the evening star, but the Greek astronomers knew better. (Venus's apparition as the morning star is also sometimes called Lucifer.)
Since Venus is an inferior planet, it shows phases when viewed with a telescope from the perspective of Earth. Galileo's observation of this phenomenon was important evidence in favor of Copernicus's heliocentric theory of the solar system
The first spacecraft to visit Venus was Mariner 2 in 1962. It was subsequently visited by many others (more than 20 in all so far), including Pioneer Venus and the Soviet Venera 7 the first spacecraft to land on another planet, and Venera 9 which returned the first photographs of the surface.
The first orbiter, the US spacecraft Magellan produced detailed maps of Venus' surface using radar. ESA's Venus Express is now in orbit with a large variety of instruments
Venus' rotation is somewhat unusual in that it is both very slow (243 Earth days per Venus day, slightly longer than Venus' year) and retrograde. In addition, the periods of Venus' rotation and of its orbit are synchronized such that it always presents the same face toward Earth when the two planets are at their closest approach. Whether this is a resonance effect or merely a coincidence is not known.
Venus is sometimes regarded as Earth's sister planet. In some ways they are very similar:
Venus is only slightly smaller than Earth (95% of Earth's diameter, 80% of Earth's mass).
Both have few craters indicating relatively young surfaces.
Their densities and chemical compositions are similar.
Because of these similarities, it was thought that below its dense clouds Venus might be very Earthlike and might even have life. But, unfortunately, more detailed study of Venus reveals that in many important ways it is radically different from Earth. It may be the least hospitable place for life in the solar systemThe pressure of Venus' atmosphere at the surface is 90 atmospheres (about the same as the pressure at a depth of 1 km in Earth's oceans). It is composed mostly of carbon dioxide. There are several layers of clouds many kilometers thick composed of sulfuric acid. These clouds completely obscure our view of the surface. This dense atmosphere produces a run-away greenhouse effect that raises Venus' surface temperature by about 400 degrees to over 740 K (hot enough to melt lead). Venus' surface is actually hotter than Mercury's despite being nearly twice as far from the SunThere are strong (350 kph) winds at the cloud tops but winds at the surface are very slow, no more than a few kilometers per hour.
Venus probably once had large amounts of water like Earth but it all boiled away. Venus is now quite dry. Earth would have suffered the same fate had it been just a little closer to the Sun. We may learn a lot about Earth by learning why the basically similar Venus turned out so differently.
Most of Venus' surface consists of gently rolling plains with little relief. There are also several broad depressions: Atalanta Planitia, Guinevere Planitia, Lavinia Planitia. There two large highland areas: Ishtar Terra in the northern hemisphere (about the size of Australia) and Aphrodite Terra along the equator (about the size of South America). The interior of Ishtar consists mainly of a high plateau, Lakshmi Planum, which is surrounded by the highest mountains on Venus including the enormous Maxwell Montes.
Data from Magellan's imaging radar shows that much of the surface of Venus is covered by lava flows. There are several large shield volcanoes (similar to Hawaii or Olympus Mons) such as Sif Mons. Recently announced findings indicate that Venus is still volcanically active, but only in a few hot spots; for the most part it has been geologically rather quiet for the past few hundred million years.
There are no small craters on Venus. It seems that small meteoroids burn up in Venus' dense atmosphere before reaching the surface. Craters on Venus seem to come in bunches indicating that large meteoroids that do reach the surface usually break up in the atmosphere.
The oldest terrains on Venus seem to be about 800 million years old. Extensive volcanism at that time wiped out the earlier surface including any large craters from early in Venus' history.
About The Team-
Sara Seager
Ellen Swallow Richards Associate Professor (January 2007)
Ph.D., 1999, Harvard University
Phone: 617-253-6775
Address:
54-1626
Dept. of Earth, Atmospheric, and Planetary Sciences
Massachusetts Institute of Technology
77 Massachusetts Ave.
Cambridge, MA 02139-4307 USA
Joseph Harrington-
Assistant Professor of Physics and
Planetary Science
Office: MAP 420
Phone: 407-823-3416
Email: jharring@physics.ucf.edu
Website: http://physics.ucf.edu/~jh
Degrees Earned
S.B., Physics, 1988,
Massachusetts Institute of Technology
Ph.D., Planetary Science, 1994,
Massachusetts Institute of Technology
About Spitzer Space Telescope:
The Spitzer Space Telescope (formerly SIRTF, the Space Infrared Telescope Facility) was launched into space by a Delta rocket from Cape Canaveral, Florida on 25 August 2003. During its mission, Spitzer will obtain images and spectra by detecting the infrared energy, or heat, radiated by objects in space between wavelengths of 3 and 180 microns (1 micron is one-millionth of a meter). Most of this infrared radiation is blocked by the Earth's atmosphere and cannot be observed from the ground.
Consisting of a 0.85-meter telescope and three cryogenically-cooled science instruments, Spitzer is the largest infrared telescope ever launched into space. Its highly sensitive instruments give us a unique view of the Universe and allow us to peer into regions of space which are hidden from optical telescopes. Many areas of space are filled with vast, dense clouds of gas and dust which block our view. Infrared light, however can penetrate these clouds, allowing us to peer into regions of star formation, the centers of galaxies, and into newly forming planetary systems. Infrared also brings us information about the cooler objects in space, such as smaller stars which are too dim to be detected by their visible light, extrasolar planets, and giant molecular clouds. Also, many molecules in space, including organic molecules, have their unique signatures in the infrared.
Because infrared is primarily heat radiation, the telescope must be cooled to near absolute zero (-459 degrees Fahrenheit or -273 degrees Celsius) so that it can observe infrared signals from space without interference from the telescope's own heat. Also, the telescope must be protected from the heat of the Sun and the infrared radiation put out by the Earth. To do this, Spitzer carries a solar shield and will be launched into an Earth-trailing solar orbit. This unique orbit places Spitzer far enough away from the Earth to allow the telescope to cool rapidy without having to carry large amounts of cryogen (coolant). This innovative approach has significantly reduced the cost of the mission.
In The Images:
1.This artist's concept illustrates the hottest planet yet observed in the universe. The scorching ball of gas, a "hot Jupiter" called HD 149026b, is a sweltering 3,700 degrees Fahrenheit (2,040 degrees Celsius) -- about 3 times hotter than the rocky surface of Venus, the hottest planet in our solar system
2.Sara Seager
3. Very Faraway Planet (Widescreen Version
4.Joseph Harrington
Release link: http://www.spitzer.caltech.edu/Media/releases/ssc2007-09/release.shtml
