Hubble Spots Fast-Moving Runaway Star in Kleinmann-Low Nebula

In the search for free-floating exoplanets and brown dwarfs, astronomers using the NASA/ESA Hubble Space Telescope have created a mosaic image of the Kleinmann-Low Nebula, part of the famous Orion Nebula complex. During their survey of this region, they found what may be the missing piece of a cosmic puzzle: the third, long-lost member of a now-defunct multiple-star system.

This composite image of the Kleinmann-Low Nebula is composed of several pointings of the NASA/ESA Hubble Space Telescope in optical and near-infrared light. The revealed stars are shown with a bright red color in the image. Image credit: NASA / ESA / Hubble.
The Kleinmann-Low Nebula, the most active part of the Orion Nebula complex, is approximately 1,400 light-years away.
Penn State astronomer Kevin Luhman led a team that used Hubble to hunt for rogue planets — free-floating in space without a parent star — and brown dwarfs in this region.
The infrared capabilities of the telescope also allow it to peer through the swirling clouds of dust and gas and make the stars hidden within clearly visible.
Among these, the astronomers stumbled across a star moving at an unusually high speed — about 124,300 mph (200,000 km per hour).
This star could be the missing piece of the puzzle of a star system that had been broken apart 540 years ago.

This Hubble image shows a grouping of young stars, called the Trapezium Cluster (center). The box just above the Trapezium Cluster outlines the location of the three stars. A close-up of the stars is top right. The birthplace of the multi-star system is marked ‘initial position.’ Two of the stars - labeled BN, and ‘I’ - were discovered decades ago. The source ‘I’ is embedded in thick dust and cannot be seen. The third star - 'X’ - was recently discovered to have moved noticeably between 1998 and 2015, as shown in the inset image at bottom right. Image credit: NASA / ESA / K. Luhman, Penn State University / M. Robberto, STScI.
Scientists already knew about two other runaway stars in the Orion Nebula complex which were most likely once part of a now-defunct multiple-star system.
For years it was suspected that the original system contained more than just these two stars.
Now, by virtue of accident and curiosity, Hubble may have found the missing third piece of this cosmic puzzle.
Whether the new star is indeed the missing -and the last - piece of the puzzle will require further observations.
So will the answer to the question of why the original star system broke apart in the first place.
While there are several theories — interactions with other, nearby stellar groups, or two of the stars getting too close to each other — none can be ruled out or confirmed yet.
"The new Hubble observations provide very strong evidence that the three stars were ejected from a multiple-star system,” Dr. Luhman said.
"Astronomers had previously found a few other examples of fast-moving stars that trace back to multiple-star systems, and therefore were likely ejected.”
"But these three stars are the youngest examples of such ejected stars. They’re probably only a few hundred thousand years old.”
"In fact, based on infrared images, the stars are still young enough to have disks of material leftover from their formation.”
The team’s results were published online this month in the Astrophysical Journal Letters ( preprint).

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