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January 26, 2016

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Astronomers report finding widest known solar system by far

Jan. 26, 2016
Courtesy of the Aus­tral­ian Na­t­ional Un­ivers­ity
and World Science staff

As­tro­no­mers stu­dy­ing a “lonely” or seeming­ly un­moored plan­et drift­ing through space have found its mom—a star a tril­lion kilo­me­ters (about 6,400 bil­lion miles) away. That would make it easily the larg­est so­lar sys­tem ev­er found.

The sci­en­tists say the plan­et, known as 2MASS J2126-8140, has an or­bit around its host star that takes nearly a mil­lion Earth years and is more than 140 times wid­er than Plu­to’s. 

An infrared-light im­age of TYC 9486-927-1 and 2MASS J2126. The ar­rows show the pro­jected move­ment of the star and plan­et on the sky over 1000 years. The scale in­di­cates a dis­tance of 4000 As­tro­nom­i­cal Units (AU), where 1 AU is the av­er­age dis­tance be­tween the Earth and the Sun. (Cred­it: 2MASS/S. Mur­phy/ANU)


“We were very sur­prised to find such a low-mass ob­ject so far from its par­ent star,” said Aus­tral­ian Na­t­ional Un­ivers­ity as­tron­o­mer Si­mon Mur­phy. “There is no way it formed in the same way as our so­lar sys­tem did, from a large disc of dust and gas” sur­round­ing the star.

“There is little pros­pect of any life on an exo­tic world like this,” Mur­phy added. “But any in­habi­tants would see their 'Sun' as no more than a bright star, and might not even ima­gine they were con­nected to it at all.”

Only a hand­ful of ex­tremely wide pairs of this kind have been found in re­cent years, he added. The dis­tance be­tween the new pair is meas­ured as 6,900 as­tro­nom­i­cal un­its, or Earth-sun dis­tances—nearly three times that of the pre­vi­ous wid­est pair, which is 2,500 as­tro­nom­i­cal un­its.

The plan­et’s par­ent is iden­ti­fied as a red dwarf star called TYC 9486-927-1. At that dis­tance, it would ap­pear as only a mod­er­ately bright star in the sky, and its light would take about a month to reach the plan­et.

Mur­phy is part of an in­terna­t­ional team of sci­en­tists that stud­ied the plan­et, a gas gi­ant weigh­ing the equiv­a­lent of an es­ti­mat­ed 12 to 15 Jupiters, as part of a sur­vey of sev­eral thou­sand young stars and brown dwarfs close to our so­lar sys­tem.

The re­search­ers real­ized the plan­et and the star were a si­m­i­lar dis­tance from the Earth—a­bout 100 light-years. A light-year is the dis­tance light trav­els in a year. Hav­ing no­ticed the dis­tance si­m­i­lar­ity, the as­tron­o­mers com­pared the mo­tion of the two through space and real­ized they were mov­ing to­geth­er. 

“We can spec­u­late they formed 10 mil­lion to 45 mil­lion years ago from a fil­a­ment of gas that pushed them to­geth­er in the same di­rec­tion,” Mur­phy said. “They must not have lived their lives in a very dense en­vi­ron­ment. They are so ten­u­ously bound to­geth­er that any near­by star would have dis­rupted their or­bit com­plete­ly.”

The findings are to be pub­lished in the jour­nal Month­ly No­tices of The Roy­al Astro­n­om­i­cal So­ciety.


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Astronomers studying a lonely planet drifting through space have found its mom—a star a trillion kilometers (about 6,400 billion miles) away. The scientists say the planet, known as 2MASS J2126-8140, has an orbit around its host star that takes nearly a million Earth years and is more than 140 times wider than Pluto’s. This makes it easily the largest solar system ever found. “We were very surprised to find such a low-mass object so far from its parent star,” said Australian National University astronomer Simon Murphy. “There is no way it formed in the same way as our solar system did, from a large disc of dust and gas” surrounding the star. Only a handful of extremely wide pairs of this kind have been found in recent years, he added. The distance between the new pair is measured as 6,900 astronomical units, or Earth-sun distances—nearly three times that of the previous widest pair, which is 2,500 astronomical units. The planet’s parent is identified as a red dwarf star called TYC 9486-927-1. At that distance, it would appear as only a moderately bright star in the sky, and light would take about a month to reach the planet. Murphy is part of an international team of scientists that studied the planet, a gas giant weighing the equivalent of an estimated 12 to 15 Jupiters, as part of a survey of several thousand young stars and brown dwarfs close to our solar system. The researchers realized the planet and the star were a similar distance from the Earth—about 100 light-years. A light-year is the distance light travels in a year. Having noticed the distance similarity, the astronomers compared the motion of the two through space and realized they were moving together. “We can speculate they formed 10 million to 45 million years ago from a filament of gas that pushed them together in the same direction,” Murphy said. “They must not have lived their lives in a very dense environment. They are so tenuously bound together that any nearby star would have disrupted their orbit completely.”