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Nearby Hot Jupiter Analyzed As Part Of Ongoing Exoplanet Search

August 19, 2013
Image Caption: The planet HD 189733b was discovered in 2005 and is only 2.9 million miles from its parent star. The planet is so close to its star that it is gravitationally "tidally locked" so that one side always faces the star and the other side is always dark. Credit: NASA, ESA, and G. Bacon (STScI)

[ Watch the Video: The Strange Attraction of Hot Jupiters ]

redOrbit Staff & Wire Reports – Your Universe Online

The number of exoplanets discovered by astronomers since the beginning of the Space Age some five decades ago suggests there are possibly over 100 billion such worlds outside our solar system, according to one Caltech astronomer involved with NASA’s Kepler mission.

According to John Johnson, an assistant professor of astronomy at the Pasadena-based university, over the past 50 years the number of known planets located beyond the Milky Way has increased from zero to more than 850.

As if that wasn’t enough, there are also thousands of additional potential exoplanet candidates currently awaiting official confirmation, the US space agency said. The rate at which ground-based telescopes and orbiting observatories such as Kepler have located these extrasolar planets suggests, “there are at least 100 billion planets in our galaxy,” Johnson said. “That’s mind-boggling.”

Interestingly enough, when the earliest days of the search for exoplanets began, astronomers focused on attempting to find Earth-like worlds capable of supporting life in distant solar systems. However, NASA said planets as small as our own which are orbiting stars located hundreds of light-years away have proven difficult to find.

The “real haul,” according to the space agency, has been gas giants – especially the massive exoplanets known as “hot Jupiters.” These worlds share many of the characteristics of our solar system’s largest planet, except they have higher surface temperatures due to the close proximity of their orbits to their stars – between approximately 0.015 and 0.5 astronomical units. By comparison, Jupiter orbits the Sun at 5.2 astronomical units.

Since they orbit so close to their parent stars, hot Jupiters tend to block a portion of their star’s light when they transit in front. These events are known as “mini-eclipses” and have resulted in hundreds of discoveries. While interest in these types of exoplanets was initially low, they have begun to attract some attention as of late, NASA explained.

To illustrate the point, officials from the aeronautics administration refer to “HD 189733b,” a planet discovered by researchers working out of the Haute-Provence Observatory in France in 2005. This planet is just 63 light years away and manages to block three percent of the light produced by its orange-dwarf parent star, and NASA reports astronomers have been able to learn a great deal by analyzing it.

“For one thing, it’s blue,” the agency said. “Data obtained by the Hubble Space Telescope suggest that, seen from a distance, the azure disk of HD 189733b would look to the human eye much like Earth. Indeed, some members of the media have taken to calling it ‘the other blue planet.’ It is, however, anything but Earthlike.

“In 2007, Heather Knutson of Caltech made a global temperature map of HD189733b using NASA’s infrared Spitzer Space Telescope. She knew it would be hot because HD189733b orbits its star 13 times closer than Mercury,” added NASA. “Temperatures ranged from 1200 F on the nightside to 1700 F on the dayside. Thermal gradients drive winds as fast as 6000 mph, carrying suffocating heat around the globe.”

Experts believe the planet’s blue color could be caused by the presence of silicate particles in its atmosphere. Those particles would scatter blue wavelengths of light from its parent star, and since silicates are a component of glass, some researchers speculate it could be raining molten glass on HD189733b.

NASA and ESA X-ray observatories recently observed the planet transit its star and detected a drop in X-rays three times deeper than the corresponding decrease in optical light. That would indicate the planet’s outer atmosphere is larger than anyone expected. It could actually be boiling away, according to researchers who have estimated HD189733b is losing 100 million to 600 million kilograms of mass per second.

Last Thursday, NASA announced it was scrapping attempts to fully restore Kepler, which had two of its four gyroscope-like reaction wheels fail over the past 13 months. The wheels are used to precisely direct the spacecraft and engineers had been hoping to restore at least one of them to working condition.

Those efforts have proven unsuccessful and now the agency is working on potential new missions Kepler would be able to complete its current state. In the meantime, Kepler has been returned to its point rest state, which is a stable configuration where the telescope uses its thrusters to control its pointing with minimal fuel use.


Source: redOrbit Staff & Wire Reports - Your Universe Online



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