First stellar stream beyond Milky Way could decode dark matter
What's the story
Astronomers have made a groundbreaking discovery by detecting the first-ever globular cluster stellar stream outside of our Milky Way galaxy. The finding, published in Nature, was made by researchers from the Niels Bohr Institute and DTU Space with international collaborators. The stellar stream was found in UGC9050-Dw1, an ultra-diffuse galaxy that is unusually faint despite its large physical size.
Stellar streams
What are globular cluster stellar streams?
Globular cluster stellar streams are long, faint structures of stars that were once part of a globular cluster.
Gravitational forces can pull these stars away from their clusters and spread them along their orbit, creating a stream.
These structures carry information about the gravitational environment they have traveled through, making them valuable for studying dark matter, an invisible form of matter thought to account for most of the universe's mass.
Dark matter
UGC9050-Dw1 has a lot of dark matter
The discovery of the stellar stream in UGC9050-Dw1 is more than just an observation. The researchers used this stream to estimate how mass is distributed within the galaxy and how much mass it contains.
Their analysis suggests that UGC9050-Dw1 has a lot of dark matter, in line with previous studies of ultra-diffuse galaxies.
This study offers a new way to probe dark matter in galaxies where traditional measurements can be difficult.
Importance
What is dark matter and why does it matter?
Dark matter is not directly detectable by conventional telescopes as it neither emits, absorbs, nor reflects light.
Its presence is inferred from its gravitational influence on visible matter like stars and galaxies.
Understanding the distribution of dark matter could provide vital clues about its nature and role in galaxy formation and evolution.
Until now, insights from globular cluster stellar streams have been limited to the Milky Way.
Future prospects
Future of stellar streams and dark matter studies
The discovery of the stellar stream in UGC9050-Dw1 opens up new possibilities for finding globular cluster stellar streams in other galaxies. This could eventually allow researchers to measure the dark matter content of more ultra-diffuse galaxies.
The team expects that as astronomical surveys become more powerful, the number of detectable stellar streams will increase.