The Largest Solar System Ever Has Been Discovered

Astronomers studying a lonely planet drifting through space have found its mum; a star a trillion kilometres away. 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.

Photo: Artist’s depiction of the gas giant planet 2MASS J2126-8140 in orbit around the red dwarf star TYC 9486-927-1, faintly visible in the background. Credit: University of Hertfordshire/Neil James Cook

"We were very surprised to find such a low-mass object so far from its parent star," said Dr Simon Murphy of The Australian National University (ANU) Research School of Astronomy and Astrophysics.

"There is no way it formed in the same way as our solar system did, from a large disc of dust and gas."

Only a handful of extremely wide pairs of this kind have been found in recent years. The distance between the new pair is 6,900 Astronomical Units (AU) — 1,000,000,000,000 kilometres or 0.1 light years – nearly three times the previous widest pair, which is 2,500AU (370,000,000,000 km).

2MASS J2126−8140's parent is 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.

Dr Murphy is part of an international team of scientists that studied 2MASS J2126−8140, a gas giant planet around 12 to 15 times the mass of Jupiter, as part of a survey of several thousand young stars and brown dwarfs close to our solar system.

Once they realised 2MASS J2126−8140 and TYC 9486-927-1 were a similar distance from the Earth — about 100 light years — they compared the motion of the two through space and realised they were moving together.

Photo: False colour infrared image of TYC 9486-927-1 and 2MASS J2126-8140, with arrows showing their motion on the sky over the next 1,000 years. The scale is given in Astronomical Units (AU), the average Earth-Sun distance. For comparison, Pluto has an average distance of only 39 AU. Credit: Two Micron All Sky Survey (2MASS)/Simon Murphy (ANU)

"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," Dr 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 research, which will be published in the Monthly Notices of The Royal Astronomical Society, was led by Dr Niall Deacon from University of Hertfordshire and included Dr Joshua Schlieder from the NASA Ames Research Center.

[Australian National University]

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    So in the image its showing a picture of the planet... how is that possible, we cant image a planet at this distance? It does say false color, but why does it show the planet like its a snapshot of the actual planet.....???

    From what I know, when they do artists depictions like that, the astronomers already have spectral line readings from the planet to allow them to get a solid picture of the elements that make up the atmosphere, which gives means they can sort-of predict how the planet will look up close under stellar light.

    Though I wonder how accurate that depiction is given the distance to it's parent, I half suspect there wouldn't be that much light.

    LOL sorry not the first picture.
    The second one!
    So thats an "artists depiction" also? 10 pixels or so of guesswork. Seems like the caption should mention that or use an icon vs a render.
    If we could ever image a planet at the sort of res shown in the second pic it would be earth shattering news (we'd have a giant space telescope too I guess..!)

      Hi Shannell - I made that image for the paper so hopefully I can answer your question. The second image (with the arrows and labels) is a real image made from observations by the Two Micron All Sky Survey (2MASS). I combined 3 images at wavelengths of 1.3, 1.7 and 2.2 microns to make the false colour image. 2MASS actually has pretty modest resolution so we are only able to detect the planet because it's so far away from the star. Only being 100 light years away from us helps too. It's much harder to directly image planets in closer orbits because we are blinded by the glare from the star, but new instruments such as SPHERE on the Very Large Telescope and the Gemini Planet Imager have started to do this in the last year or so for the brightest stars.

    Wow, so Ive been out of touch... I used to read a lot of astronomy stuff, I have a 10" scope also but I moved on to other hobbies. So it seems theres quite a few directly imaged planets, theres a wiki which lists a few:

    One has a 20 year orbit which is neat, to be able to see that move relatively quickly year to year.

    Cant believe I never heard about this... Ill be reading up on a few of these.

    Thanks Simon for taking the time to post here :)

    It's a fascinating, fast-moving field. I always like to point people to images of HR 8799 ( Four gas-giant planets in face-on orbits. Still blows my mind!

    Sure it's a big solar system, but when you consider that it's only 8x the size of the largest star detected so far (UY Scuti) , it's still quite small .

    please ignore last post. I'm confusing units.

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