Hubble ‘Star Wars’ Find: Gravitational Battle Produces Trio Of Runaway Stars

Researchers using NASA’s Hubble Space Telescope have uncovered evidence of a trio of runaway stars in the Orion Nebula that once had a common origin, but, due to an actual battle between stars, forces conspired to expel three of the competing stars and send them flying off through space in various directions. The struggle between gravitational fields ended around the year 1400, scientists say, with at least three stars being flung into space.

NASA reported this week that while English royal families were fighting the War of the Roses (mid- through late 1400s), a star war was being waged in the Orion Nebula some 1,344 light years away. That faraway war ended with the stars being ejected from their common point of origin.

The fact that there were runaway stars in the Orion Nebula went unnoticed for hundreds of years — until two of the stars were discovered in radio and infrared observations of the gaseous and dusty nebula (which had kept regular optical telescopes from detecting the stars).

The original observations found that two stars were moving at high speeds in opposite directions from each other. Although astronomers were able to track the duo backward some 540 years to a common point of origin, there seemed to be something wrong with the calculations involving a multiple star system and the energy required that would have initially set the two stars in motion. That propulsion, it was reasoned, would have required a third star.

NASA’s Hubble Space Telescope found it.

Astronomers were able to track a newly-found errant star all the back that same 540 years to the same point of origin as the other two wayward stars. The trio are moving through a region of the Orion Nebula complex called the Kleinmann-Low Nebula, located near the center of the complex, which is populated by young stars.

“The new Hubble observations provide very strong evidence that the three stars were ejected from a multiple-star system,” said lead researcher Kevin Luhman of Penn State University in University Park, Pennsylvania. “Astronomers had previously found a few other examples of fast-moving stars that trace back to multiple-star systems, and therefore were likely ejected.”

This trio of stars, though, have been found to be “the youngest examples of such ejected stars” and are estimated to be about “a few hundred thousand years old.” Luhman added, “In fact, based on infrared images, the stars are still young enough to have disks of material leftover from their formation.”

The three stars are moving at different speeds as well. The two original stars (designated BN, for Becklin-Neugebauer, and “source I”), which were found in infrared data in 1967, were found to be traveling at 60,000 and 22,000 miles (96,561 and 35,406 kilometers) per hour, respectively. The two stars were not discovered moving quickly away from each other until 1995.

Luhman himself came across the third star, which has been dubbed “source x,” while looking for rogue planets in the Orion Nebula as part of an international team led by Massimo Robberto of the Space Telescope Science Institute in Baltimore, Maryland. During the analysis, Luhman compared the new infrared images taken by Hubble’s Wide Field Camera 3 in 2015 with infrared observations taken in 1998 by the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) and discovered that source x had altered its position considerably relative to nearby stars, indicating that the star was moving extremely fast — at about 130,000 miles per hour.

Luhman likened the expulsion of the trio of stars to a cosmic game of billiards. Usually two stars in multiple star system gravitate toward each other to either merge into a single star or form a binary system. Regardless of which event occurs, gravitational gets released in such amounts as to propel all the stars away from each other.

Propelled or “runaway” stars like the trio inside the Orion Nebula and others like them are just one example of stars moving at high rates of speed relative to those around them. But they’re extremely slow compared hypervelocity stars, a class of stellar objects discovered in 2013, according to Space.com. These stars, caught in elliptical orbits around black holes, get slingshotted — instead of devoured by the black hole — out into space. These stars can reach speeds as high as 895 kilometers (556 miles) per second, or 3.2 million kilometers (2 million miles) per hour.

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