Citizen scientists using data from NASA's WISE telescope (later dubbed the NEOWISE mission) have discovered an object zooming out of the Milky Way galaxy at 1 million miles per hour.
The object is speeding so fast, it was able to escape the gravitational pull of our galaxy and shoot out into space.
Given most stars orbit the centre of the Milky Way, that makes this mysterious, small stellar-mass object something of a find.
How the galaxy's ejected object was found
Citizen scientists play a key role in assisting astronomical studies of the Universe and in space missions.
These volunteers give their time to a range of projects, from helping discover exoplanets to producing colour images out of raw data captured by space probes.
In this case, citizen scientists were working on NASA’s Backyard Worlds: Planet 9 project, which uses images from NASA’s WISE (Wide Field Infrared Explorer) mission.
WISE mapped the sky in infrared light from 2009 to 2011 and was then re-activated as NEOWISE (Near-Earth Object Wide-field Infrared Survey Explorer) in 2013, before being retired on 8 August 2024.
Citizen scientists Martin Kabatnik, Thomas P. Bickle and Dan Caselden found a faint object called CWISE J124909.08+362116.0 zipping across the galaxy while checking WISE images.
Follow-up observations were made with ground-based telescopes, enabling astronomers to confirm that they were seeing what they thought they were seeing, and to characterise the object.
They found that CWISE J1249 is speeding out of the Milky Way at 1 million miles per hour.
What is CWISE J1249?
It has a low mass, making it difficult to classify: it could be a low-mass star or a brown dwarf (an object that's categorised between a gas giant planet and a star).
The citizen scientists are co-authors of a study that's been published in the Astrophysical Journal Letters.
"I can’t describe the level of excitement," says Kabatnik, a citizen scientist from Nuremberg, Germany.
"When I first saw how fast it was moving, I was convinced it must have been reported already."
If it is a brown dwarf, it joins some over 4,000 that have been discovered by Backyard Worlds: Planet 9 volunteers.
However, CWISE J1249 is the only one discovered so far to be speeding its way out of the galaxy.
Observations using the famous W. M. Keck Observatory in Maunakea, Hawaii, reveal it has much less iron and other metals than other stars and brown dwarfs.
That, say astronomers, means it's likely extremely old: even from the first generations of stars in our galaxy.
Why is CWISE J1249 moving so fast?
Why has CWISE J1249 been ejected out of the Milky Way at 1 million miles per hour?
Astronomers suggest it may have originally been part of a binary system with a white dwarf, which exploded as a supernova when it accreted too much material from its companion.
Or it may have been part of a type of ancient star cluster known as a globular cluster, and a close encounter with a pair of black holes boosted it out of the galaxy.
"When a star encounters a black hole binary, the complex dynamics of this three-body interaction can toss that star right out of the globular cluster," says Kyle Kremer, incoming assistant professor in UC San Diego’s Department of Astronomy and Astrophysics.
Scientists are now going to gather more data on CWISE J1249 to attempt to discern which of these scenarios is most likely.
The study is led by Backyard Worlds: Planet 9 science team member Adam Burgasser, a professor at the University of California, San Diego, and includes co-authors Hunter Brooks and Austin Rothermich, astronomy students who both began their astronomy careers as citizen scientists.
Read the full paper at arxiv.org/abs/2407.08578
