Citizen Scientists Discover Hypervelocity Star on Escape Path from Milky Way

A team of astronomers and citizen scientists made a groundbreaking discovery when they detected an object moving through the Milky Way at such an incredible speed that it could potentially escape the galaxy's gravity and reach intergalactic space. This celestial object, likely a faint red star, was observed with the help of the public, who meticulously combed through data collected by NASA's Wide-field Infrared Survey Explorer mission. The results of their efforts have been accepted for publication in The Astrophysical Journal Letters.

The star, named CWISE J124909.08+362116.0 (J1249+36 for short), is moving at a speed of approximately 1.3 million miles per hour (600 kilometers per second). To put this into perspective, the sun orbits the Milky Way at a relatively slower rate of 450,000 miles per hour (200 kilometers per second). If confirmed, this discovery would mark the first known "hypervelocity" very low-mass star, which would be an extraordinary find in the realm of astronomy.

The Nature of Hypervelocity Stars

Hypervelocity stars, first theorized to exist in 1988 and discovered in 2005, are already extremely rare. According to study coauthor Roman Gerasimov, a postdoctoral research fellow in the department of physics and astronomy at the University of Notre Dame, the discovery of a hypervelocity low-mass star is particularly exciting because it expands our understanding of these elusive celestial objects.

Low-mass stars are more abundant than their high-mass counterparts because star formation favors objects of lower mass. Additionally, stars with more mass tend to have shorter lifespans. However, low-mass stars are challenging to detect due to their cooler and less luminous nature. This makes the detection of a hypervelocity low-mass star even more significant and noteworthy.

Citizen Scientists: Pioneers of Discovery

The citizen scientists participating in the project Backyard Worlds: Planet 9 had a pivotal role in this discovery. They initially detected the star while searching for evidence of undiscovered objects or the hypothetical Planet Nine in "the backyard of the solar system" beyond Neptune. The scientists involved with the project meticulously looked for patterns and anomalies within large amounts of data collected by NASA. Their dedication and keen observations ultimately led to the identification of the hypervelocity star.

The remarkable speed of J1249+36, moving at approximately 0.1% the speed of light, caught the attention of the citizen scientists. Martin Kabatnik, a citizen scientist from Nuremberg, Germany, expressed his excitement upon discovering the star's remarkable speed, initially believing it must have been reported before. The collaborative efforts between professional astronomers and citizen scientists demonstrate the power of crowdsourced efforts in advancing scientific knowledge.

Confirming the Discovery

Following the initial detection, subsequent observations from multiple telescopes focused on the object to confirm the discovery. Adam Burgasser, a professor of astronomy and astrophysics at the University of California San Diego and the lead study author, described how the object's speed and trajectory indicated the potential for escaping the Milky Way, sparking intrigue and validation among scientists.

The classification of J1249+36 proved challenging due to its low mass, leading astronomers to question whether it was a low-mass star or a brown dwarf. Brown dwarfs, which are more massive than planets but not quite as massive as stars, have been discovered by citizen scientists working on the Backyard Worlds project. However, none of the previously discovered brown dwarfs displayed the characteristic of a hypervelocity star moving on a trajectory that would carry them out of the galaxy.

Observations and Analysis

To gain further insight into J1249+36, astronomers conducted observations using ground-based telescopes, such as the W. M. Keck Observatory in Hawaii and the University of Hawaii Institute for Astronomy's Pan-STARRS telescope in Maui. Data from the Near-Infrared Echellette Spectrograph at the Keck Observatory provided valuable information, suggesting that the star may be an L subdwarf, characterized by a much lower mass and cooler temperature than the sun. The telescope data indicated a lower concentration of metals, such as iron, in these stars or brown dwarfs, adding to the intrigue of J1249+36's composition.

By combining data from multiple telescopes, astronomers were able to determine the star's position and velocity in space, allowing them to predict its eventual exit from the Milky Way. However, despite the wealth of data collected, questions remained about the true nature of the object. Roman Gerasimov estimated the mass of J1249+36 to be approximately 8% of the mass of the sun, placing it on the lower boundary of allowed stellar masses. There is a possibility that the object may not be a star but rather a brown dwarf, further complicating its classification and understanding.

Possible Origins and Future Exploration

The researchers proposed two possible scenarios for how J1249+36 ended up on its swift path. One possibility is that the star was once a companion to a white dwarf star, which, after going through significant changes, expelled the companion star with enough force to propel it at high speed. Adam Burgasser explained that calculations support this scenario, although definitive proof of its origin is lacking. Another possibility is that J1249+36 formed in a globular cluster and was later ejected from there, a concept supported by Kyle Kremer's simulations. The potential ejection from a globular cluster is particularly intriguing, as it could provide insights into the formation and evolution of such clusters.

Scientific Implications and Future Discoveries

The discovery of J1249+36 also raises the prospect of uncovering more examples of hypervelocity stars and their origins. The researchers are optimistic about the potential to find more instances of low-mass, ejected stars traveling at high speeds through the solar neighborhood. Gerasimov emphasized the importance of understanding the chemical composition of J1249+36 to shed light on its origin and potential future trajectory. By looking for specific elemental patterns, scientists aim to pinpoint the star's system of origin and gain further insights into its nature and history.

The collaborative effort between professional astronomers and citizen scientists exemplifies the power of crowdsourced exploration in advancing scientific knowledge. The discovery of J1249+36 has opened up new avenues for understanding hypervelocity stars, low-mass objects, and the intrinsic properties of celestial bodies within the Milky Way. Ascribing to this extraordinary find, scientists eagerly anticipate the prospects of further discoveries and the tantalizing possibility of unraveling even more cosmic mysteries.