The study of planets outside of our immediate solar system has greatly advanced. Through the research efforts of astronomers and scientists they have determined that our galaxy consists of at least 400 worlds, all of which have been found beyond the reach of our sun. They have determined that in addition to our terrestrial and Jovian planets, our galaxy consists of hot Jupiters, pulsar planets, Super-Earths, eccentric planets, hot Neptunes, water worlds, free-floating planets, exo-Earths and Chthonian planets. HD209458b is a hot Jupiter said to be evolving into a chthonian planet.

Sometimes hot Jupiters or hot Neptunes live too close to their stars. Once their stars roast these exoplanets and rip at them with their gravity, they might blow the gas completely off them, leaving behind rocky cores scientists have dubbed chthonian planets or evaporated remnant cores. Their proximity to their stars could mean they are covered in lava. (Choi) HD209458b, also called Osiris, was discovered in 1999 via Doppler spectroscopy, and entered the astronomical hall of fame when it passed in front of its parent star and eclipsed it.

In 2001 Hubble detected the element sodium in the lower part of the planet’s atmosphere. In 2003 hydrogen was detected in its upper atmosphere. In 2004, oxygen and carbon were detected in the upper atmosphere. Today, HD209458b is considered to be a part of a new class of extrasolar planets proposed, called the chthonian planets, as the cores of these giant planets are primarily comprised of evaporated gas. In the July 10th issue of The Astrophysical Journal it has been reported that the Hubble Space Telescope astronomers have confirmed the existence of a tortured, baked object that they are calling a cometary planet.

Now, observations by the new Cosmic Origins Spectrograph (COS) aboard NASA’s Hubble suggest that powerful stellar winds are sweeping the castoff material behind the scorched planet and shaping it into a comet-like tail. (HubbleSite) “Since 2003 scientists have theorized that the lost mass is being pushed back into a tail and have even calculated what the tail looks like,” says astronomer Jeffrey Linsky of the University of Colorado in Boulder, leader of the COS study. “We think we have the best observational evidence to support that theory. We have measured gas coming off the planet at specific speeds, some coming toward Earth.

The most likely interpretation is that we have measured the velocity of material in a tail. ” (NASA Release: 10-167) HD 209458b weighs slightly less than Jupiter, but it orbits 100 times closer to its star than Jupiter does. It is orbiting so close to its star that its heated atmosphere is escaping into space. The roasted planet zips around in a mere 3. 5 days. (In contrast, our solar system’s speedster, Mercury, orbits the Sun in 88 days. ) The planet is one of the most intensely scrutinized extrasolar planets because it is one of the few known alien worlds that can be seen passing in front of, or transiting, its star.

The transit causes the starlight to dim slightly. In fact, the gas giant is the first alien world discovered to transit its parent star. It orbits the star HD 209458, located 153 light-years from Earth. (HubbleSite) Linsky and his team used Cosmic Origins Spectrograph to analyze the planet’s atmosphere during transiting events. During a transit, astronomers can study the structure and chemical makeup of a planet’s atmosphere by sampling the starlight that passes through it. The dip in starlight due to the planet’s passage, excluding the planet’s atmosphere, is very small, only 1. 5 percent.

When the atmosphere is added, the dip jumps to 8 percent, indicating a bloated atmosphere. (NASA Release 10-167) COS detected the heavy elements carbon and silicon in the planet’s super-hot (2,000-degree-Fahrenheit) atmosphere. This detection reveals that the parent star is heating the entire atmosphere, dredging up the heavier elements and allowing them to escape the planet. The COS data also showed that the material leaving the planet was not all traveling at the same velocity. According to Linsky, they found gas escaping at high velocities with a large amount of gas flowing towards Earth at 22,000 miles per hour.

Linsky explains. “This large gas flow is likely gas swept up by the stellar wind to form the comet-like tail trailing the planet. ” Hubble’s newest spectrograph, with its ability to probe a planet’s chemistry at ultraviolet wavelengths that are not accessible to ground-based telescopes, is proving to be an important instrument for probing the atmospheres of planets like HD 209458b. Astronomers have also used COS to sample the atmosphere of another baked planet called WASP-12b, whose atmosphere is spilling onto its star.

Another Hubble instrument called the Space Telescope Imaging Spectrograph observed HD 209458b in 2003. The STIS data showed an active, evaporating atmosphere, and a comet-tail-like structure was suggested as a possibility. But STIS wasn’t able to obtain the spectroscopic detail necessary to show an earthward-moving component of the gas during transits. Because of COS’s unique combination of very high ultraviolet sensitivity and good spectral resolution, the earthward moving component of the gas — the tail — could be directly detected for the first time. NASA) Although this extreme planet is getting roasted by its star, it won’t be destroyed anytime soon. “It will take about a trillion years for the planet to evaporate,” Linsky says. NASA’s Kepler mission monitors thousands of stars in search of transiting planets. Kepler will be sensitive enough to detect Earth-sized worlds, if any exist, around several hundred nearby stars. These studies will then lead to the proposed Terrestrial Planet Finder mission which will examine known extrasolar planets for signs of life. The findings of this research will enable us to determine what type of planet HD 209458b is.

In addition to the type of planet, scientists will be able to determine the planets composition. In previous research HD 209458b showed tiny silicates in its atmosphere. If future research unravels new information about the planets atmosphere, we could determine whether or not the planets skies are filled with dense, dusty clouds, unlike anything studied in our solar system; we may also discover whether or not water is present in its cloudlike layer of atmosphere. If water is in fact present then we would be able to detect other vital molecules critical to support life processes.

While we do not expect such a hot, gaseous planet to support life, it is encouraging to discover that the spectroscopic analysis of such transit events will, in time, reveal the chemical signatures of other life-bearing planets in our solar system.

Works Cited Choi, Charles Q. “Untitled Document. ” Space. com. Web. 31 October 2010. . “HubbleSite – NewsCenter – Superhot Planet Likely Possesses Comet-like Tail (07/15/2010) – The Full Story. ” HubbleSite — Out of the Ordinary… out of This World. Web. 31 October 2010. . NASA Release 10-167. NASA Finds Super Hot Planet With Unique Comet-Like Tail. ” NASA – Home. Web. 31 October 2010. .


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