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“Superstorm” detected on planet outside our system

June 23, 2010
Courtesy of the European Southern Observatory
and World Science staff

As­tro­no­mers have for the first time meas­ured a “su­pe­r­storm” in the at­mos­phere of a plan­et out­side our so­lar sys­tem, ac­cord­ing to a re­port.

Sci­en­tists say the plan­et, dubbed HD209458b, is si­m­i­lar to Ju­pi­ter in our sys­tem, but much hot­ter.

Artist's con­cept of plan­et HD209458b, with its host star in the back­ground. (Courtesy NA­SA)


Car­bon mon­ox­ide gas is con­tin­uous­ly stream­ing at enor­mous speed from the plan­et’s scorch­ing day side to­ward the cool­er, night side, as­tro­no­mers said. Their ob­serva­t­ions al­so al­low an­oth­er ex­cit­ing “first,” they added: meas­ur­ing the or­bit­al speed of the plan­et it­self. That pro­vides a di­rect de­ter­mina­t­ion of its mass, the to­tal amount of ma­te­ri­al that makes it up.

The find­ings are pub­lished this week in the re­search jour­nal Na­ture.

“HD209458b is def­i­nitely not a place for the faint-hearted. By stu­dy­ing the poi­son­ous car­bon mon­ox­ide gas with great ac­cu­ra­cy we found ev­i­dence for a su­pe­r wind, blow­ing at a speed of 5,000 to 10,000 km (3,000 to 6,000 miles) per hour‚” said Ig­nas Snel­len of Lei­den Ob­servatory in The Neth­er­lands, who led the group of as­tro­no­mers.

The plan­et, with about 60 per­cent Ju­pi­ter’s mass, or­bits a sun-like star lo­cat­ed 150 light-years from Earth in the di­rection of the con­stella­t­ion Peg­a­sus (the Winged Horse), re­search­ers said. A light-year is the dis­tance light trav­els in a year.

Cir­cling the star at a dis­tance of only one twen­ti­eth the dis­tance be­tween Sun and Earth, the plan­et’s hot side has a sur­face tempe­rature estimated at a scald­ing 1,000 de­grees Cel­si­us. But as the plan­et al­ways has its same side fac­ing its star, one side is very hot; the oth­er is much cool­er. “On Earth, big tempe­rature dif­fer­ences in­evitably lead to fierce winds, and as our new mea­sure­ments re­veal, the situa­t­ion is no dif­fer­ent on HD209458b,” said team mem­ber Si­mon Al­brecht of the Mas­sa­chu­setts In­sti­tute of Tech­nol­o­gy.

Every 3.5 days the plan­et moves in front of its host star from our point of view. It then blocks a bit of the star­light for three hours. This is the way the plan­et was orig­i­nally de­tected.

Dur­ing such events, a ti­ny frac­tion of the star­light fil­ters through the plan­et’s at­mos­phere, which leaves an im­print on the star light. Snel­len’s group an­a­lyzed this faint sig­na­ture us­ing Eu­ro­pe­an South­ern Ob­servatory’s Very Large Tel­e­scope and an at­tached spec­tro­graph, or light anal­y­sis in­stru­ment.

Its “high pre­ci­sion al­lows us to meas­ure the ve­locity of the car­bon mon­ox­ide gas for the first time,” said an­oth­er team mem­ber, Remco de Kok of the Neth­er­lands In­sti­tute for Space Re­search. This meas­urement was based on the Dop­pler ef­fect, in which char­ac­ter­is­tic dark lines that car­bon mon­ox­ide leaves on the light’s spec­trum are slightly shifted while the gas moves.

The as­tro­no­mers said they achieved sev­er­al oth­er firsts. They di­rectly meas­ured the ve­locity of the plan­et as it or­bits its home star. In gen­er­al, the mass of a plan­et out­side the sol­ar sys­tem is de­ter­mined by meas­ur­ing the wob­ble of the star under the planet's influence, “and as­sum­ing a mass for the star, ac­cord­ing to the­o­ry,” said co-author Ernst de Mooij of Lei­den Ob­servatory. “He­re, we have been able to meas­ure the mo­tion of the plan­et as well, and thus de­ter­mine both the mass of the star and of the plan­et.”

Al­so for the first time, the as­tro­no­mers meas­ured how much car­bon is pre­s­ent in the at­mos­phere of this plan­et. “It seems that H209458b is ac­tu­ally as car­bon-rich as Ju­pi­ter and Sat­urn. This could in­di­cate that it was formed in the same way,” said Snel­len. “In the fu­ture, as­tro­no­mers may be able to use this type of ob­serva­t­ion to study the at­mos­pheres of Earth-like plan­ets, to de­ter­mine wheth­er life al­so ex­ists else­where.”


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Astronomers have measured a superstorm for the first time in the atmosphere of a planet outside our solar system, according to a report. Scientists say the planet, dubbed HD209458b, is similar to Jupiter in our system, but much hotter. Observations of carbon monoxide gas show it’s streaming at enormous speed from the planet’s extremely hot day side toward the cooler, night side, astronomers said. The observations also allow another exciting “first,” they added: measuring the orbital speed of the planet itself. That provides a direct determination of its mass, the total amount of material that makes it up. The findings are published this week in the research journal Nature. “HD209458b is definitely not a place for the faint-hearted. By studying the poisonous carbon monoxide gas with great accuracy we found evidence for a super wind, blowing at a speed of 5,000 to 10,000 km (3,000 to 6,000 miles) per hour‚” said Ignas Snellen of Leiden Observatory in The Netherlands, who led the group of astronomers. The planet, with about 60% Jupiter’s mass, orbis a sun-like star located 150 light-years from Earth in the direction of the constellation of Pegasus (the Winged Horse), researchers said. A light-year is the distance light travels in a year. Circling the star at a distance of only one twentieth the distance between Sun and Earth, the planet’s hot side has a scorching surface temperature of about 1,000 degrees Celsius. But as the planet always has its same side facing its star, one side is very hot; the other is much cooler. “On Earth, big temperature differences inevitably lead to fierce winds, and as our new measurements reveal, the situation is no different on HD209458b,” said team member Simon Albrecht of the Massachusetts Institute of Technology. Every 3.5 days the planet moves in front of its host star from our point of view. It then blocks a bit of the starlight for three hours. This is the way the planet was originally detected. During such events, a tiny fraction of the starlight filters through the planet’s atmosphere, which leaves an imprint on the star light. Snellen’s group analyzed this faint signature using European Southern Observatory’s Very Large Telescope and an attached spectrograph, or light analysis instrument. Its “high precision allows us to measure the velocity of the carbon monoxide gas for the first time,” said another team member, Remco de Kok of the Netherlands Institute for Space Research. This measurement was based on the Doppler effect, in which characteristic dark lines that carbon monoxide leaves on the light’s spectrum are slightly shifted while the gas moves. The astronomers said they achieved several other firsts. They directly measured the velocity of the exoplanet as it orbits its home star. “In general, the mass of an exoplanet is determined by measuring the wobble of the star and assuming a mass for the star, according to theory. Here, we have been able to measure the motion of the planet as well, and thus determine both the mass of the star and of the planet,” said co-author Ernst de Mooij of Leiden Observatory. Also for the first time, the astronomers measured how much carbon is present in the atmosphere of this planet. “It seems that H209458b is actually as carbon-rich as Jupiter and Saturn. This could indicate that it was formed in the same way,” said Snellen. “In the future, astronomers may be able to use this type of observation to study the atmospheres of Earth-like planets, to determine whether life also exists elsewhere.”