The reason apparently is supersonic winds, perhaps as strong as 9,000 miles an hour, that constantly churn the planets' atmospheres and keep temperatures on the dark side from plunging.
The planets, gas giants similar in size to Jupiter, were discovered in the last decade orbiting stars about the same size as our sun and less than 150 light years from Earth. All of them orbit within about 5 million miles of their stars, far less than Mercury's distance from our sun.
Astronomers have wondered whether planets orbiting so close to their stars but with one side in constant daylight and the other permanently dark would exhibit sharp temperature differences between the day side and the night side. For the three planets in this study, the temperatures appear to be constant, likely because of the strong winds that mix the atmosphere planetwide, said Eric Agol, a University of Washington assistant professor of astronomy and co-author of a poster presenting the findings today at the American Astronomical Society national meeting in Seattle.
"We can't say for sure that we've ruled out significant day-night temperature differences, but it seems unlikely there is a very big contrast based on our measurements and what we know about these systems," said Agol, who is lead scientist for a project using the Spitzer Space Telescope to measure the temperature properties of extrasolar planets.
Agol and colleagues Nicolas Cowan, a UW astronomy doctoral student and lead author of the poster, and David Charbonneau of the Harvard-Smithsonian Center for Astrophysics measured infrared light from each of the planetary systems at eight different positions in their orbits in late 2005. They measured the thermal brightness of the systems when the planets' day sides faced the Earth, when the night sides faced the Earth and at various phases in between. They detected no infrared brightness variations in any of the systems, suggesting there are not big differences in temperatures on the day and night sides.
Instead the planets appear to have a fairly uniform temperature of about 925 degrees Celsius, or about 1700 degrees Fahrenheit.
"If heat from the parent star is carried to the dark side, then the overall temperature would be lowered somewhat because the heat is being distributed across the planet," Agol said. "Some theorists believe that supersonic winds are responsible for recirculating the heat."
Measuring the planets' temperatures is a painstaking process because a planet's radiation is drowned out by the light from its host star. Even when a planet goes behind the parent star and disappears completely from view, the decline in light from the entire system is almost imperceptible, on the order of 0.25 percent, Agol said. Making the observations requires precise calibration and light measurements.
The three planets are 51 Pegasi, about 50 light years from our sun, HD179949b about 100 light years distant, and HD209458b about 147 light years away. A light year is about 5.88 trillion miles. In 1995, 51 Pegasi became the first planet orbiting another star to be discovered. Since then numerous planets – gas giants the mass of Jupiter or larger – have been observed from Earth. Most orbit very close to their stars. A common theory is that they formed far away from their stars, perhaps in about the same position as Jupiter is to our sun, and then migrated close to their stars. Their distance makes it difficult to gather much direct data about the planets.
To date no Earth-sized planets have been reported orbiting other stars like our sun.
Agol noted that the planets probably have the same side always facing the star because they are so close to their parent stars. The effect is the same as the Earth has on the moon, which has had its rotation slowed so much by Earth's gravity that the same side always faces Earth.
"These planets are so close to their host stars that the tidal forces are enormous, a few thousand times as strong as on Earth," he said. "The tides are so strong and form a bulge that distorts the planet so much that the orbit is slowed by the star's tug on the tidal bulge."
The Spitzer telescope is managed by NASA's Jet Propulsion Laboratory in Pasadena, Calif., and its science operations are conducted at the California Institute of Technology.
Vince Stricherz | EurekAlert!
First evidence on the source of extragalactic particles
13.07.2018 | Technische Universität München
Simpler interferometer can fine tune even the quickest pulses of light
12.07.2018 | University of Rochester
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
13.07.2018 | Event News
13.07.2018 | Materials Sciences
13.07.2018 | Life Sciences