by Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news on exciting discoveries, scientific advances and more.
An object spotted with the help of citizen scientists was moving so fast through the Milky Way that it could escape the galaxy’s gravity and reach interstellar space, new research has found.
It is probably a faint red star, and the object is zooming along at a speed of about 1.3 million miles per hour (600 kilometers per second). In comparison, the sun orbits the Milky Way at a rate of 450,000 miles per hour (200 kilometers per second).
If confirmed, the object would be the first so-called “hypervelocity” star of very low mass, according to a team of astronomers and citizen scientists whose study has been accepted for publication in The Astrophysical Journal Letters.
There are many more low-mass stars than high-mass stars because star formation favors lower-mass objects and higher-mass stars have shorter lifetimes, said study coauthor Roman Gerasimov, a postdoctoral research fellow in Department of Physics and Astronomy at the University. of Notre Dame. But low-mass stars are harder to detect because they are cooler and less luminous.
Hypervelocity stars, first theorized in 1988 and discovered in 2005, are already extremely rare, making this new discovery “particularly exciting,” he said.
The volunteers participating in a project called Backyard Worlds: Planet 9 first discovered the star, named CWISE J124909.08+362116.0, or J1249+36 for short. Researchers involved in the project look for evidence of undiscovered objects or a large hypothetical world, known as Planet Nine, in the “backyard of the solar system” beyond Neptune.
Backyard Worlds participants look for patterns and anomalies within images and data collected by the Wide-field Infrared Survey Explorer mission, which mapped the sky in infrared light from 2009 to 2011. (The space agency reassigned the mission as Near-Earth Object Wide – the Explorer Survey Infrared field in 2013 to monitor near-Earth asteroids and comets before retiring completely on August 8.)
J1249+36 jumped out at citizen scientists combing the data a few years ago because the star was moving at about 0.1% the speed of light, according to the study’s authors.
“I can’t describe the level of excitement,” study co-author Martin Kabatnik, a citizen scientist from Nuremberg, Germany, said in a statement. “When I first saw how fast it was moving, I was sure it must have already been reported.”
Follow-up observations from multiple telescopes tracked the object and helped confirm the discovery.
“This is where the source became very interesting, as its speed and track indicated that it was moving fast enough to escape the Milky Way,” said the lead study author. Adam Burgasser, professor of astronomy and astrophysics at the University of California San Diego, in a statement.
Solving a cosmic mystery
The star’s low mass made it difficult to classify at first, leading astronomers to question whether it was a low-mass star or a brown dwarf, a celestial object that is neither a star nor a planet.
Brown dwarfs are larger than planets but not as massive as stars, and citizen scientists working on the Backyard Worlds project have found more than 4,000 of them.
But none of those brown dwarfs were passing on a trajectory that would send them out of the galaxy like the “runaway” hypervelocity stars that astronomers have observed over the past two decades.
Astronomers have observed J1249+36 using ground-based telescopes, including the WM Keck Observatory on Mauna Kea in Hawaii and the University of Hawaii Institute of Astronomy’s Pan-STARRS telescope located on Maui’s Haleakalā volcano.
Data from the Keck Observatory’s Echellette Near-Infrared Spectrograph indicated that the star was an L-subdwarf, or a star with a much lower mass and cooler temperature than the sun. Cool dwarfs are the oldest stars in the galaxy.
The telescope data showed that the prospective star had a lower concentration of metals, such as iron, than other stars or brown dwarfs.
By combining the data from multiple telescopes, astronomers determined the star’s position and velocity in space, allowing them to predict that it will exit the Milky Way at some point.
But questions remain about the true nature of the thing.
“I calculated the mass of this object to be about 8% of the mass of the Sun by comparing its observed properties with computer simulations of the star’s evolution,” Gerasimov said. “This places this object at the lower limit of the allowed stellar masses, and the mass of the object may be slightly below that limit, suggesting that the object is not a star but a brown dwarf instead.”
Revealing more details about the object could help astronomers determine whether it represents a broader population of high-velocity, low-mass objects that have undergone large accelerations, according to the study’s authors.
Understanding its exact nature could help them determine when it will leave the galaxy. Previously, astronomers have observed the supermassive black hole at the center of the Milky Way giving a quick kick to a star, which will leave the galaxy for 100 million years.
Quick star kick
The researchers believe there are two possible scenarios that put J1249+36 on its fast track.
The study team said the star was likely a companion to a white dwarf star, which is the remaining core of a dead star that has expelled the gases that serve as its nuclear fuel. In these stellar pairings, if the two stars are close together, the white dwarf will siphon its mass from its companion and have an explosion called a nova. And when the white dwarf accumulates too much mass, it will collapse and explode in a supernova.
“In this type of supernova, the white dwarf is completely destroyed, so its companion is ejected and flies off at whatever orbital speed it was moving at first, plus a bit of a kick from the supernova explosion as well,” Burgasser said. “Our calculations show that this scenario works. However, the white dwarf no longer exists and the remains of the explosion, which probably happened several million years ago, have already dispersed, so we have no definite proof that this is its origin.”
Another possibility is that J1249+36 existed in a globular cluster, or a group of closely connected, spherically shaped stars. Astronomers predict that there are black holes with different masses at the center of these clusters. Black holes can become binary pairs that can capture any stars that pull too close.
“When a star becomes a black hole binary, the complex dynamics of the interaction between these three bodies can throw that star out of the globular cluster,” said study co-author Kyle Kremer, a new assistant professor in the University of California’s Department of astronomy and astrophysics. San Diego. Astrophysics, in statement.
Kremer performed simulations and found that three-body interactions can knock a low-mass subsurface star out of a cluster and put it on a trajectory similar to that of J1249+36.
“It shows a proof of concept, but we don’t really know where this globular cluster of stars came from,” Kremer said.
Gerasimov is most interested in the idea that the object was expelled from a globular cluster because such clusters include stars older than 13 billion years.
“The chemical composition and distribution of stellar masses in globular clusters capture the earliest stages in the formation and evolution of our galaxy,” he said. “However, almost everything we know about globular clusters comes from studies of their high-mass members because low-mass stars and brown dwarfs are too difficult to see.”
The James Webb Space Telescope recently allowed astronomers to identify the first brown dwarfs in a globular cluster, which have a similar mass to the object. But there aren’t too many examples so far to nail down a broader understanding.
“However, if this hypervelocity star exists, if it is a former member of a globular cluster, it opens up a new way to study low-mass cluster members by looking for those that have been ejected and are traveling at high speed through the solar neighborhood. “Gerasimov said. “Since we were able to find one example, it is likely that many more will be found in the future.”
If the path that J1249+36 has taken so far is traced backwards, there may be a crowded part of the night sky where undiscovered clusters are waiting to be found, the researchers said.
Now, scientists are hoping to learn more clues from the star’s elemental composition, which could help explain how it ended up on a path rising from the Milky Way.
When white dwarfs explode, they create possible heavy elements around J1249+36. Likewise, stars in globular clusters throughout the Milky Way have distinct patterns of elements that act as the calling card of their origins.
“We’re basically looking for a chemical fingerprint that would indicate which system this star comes from,” Gerasimov said.
For more CNN news and newsletters create an account at CNN.com
