Astronomers have been baffled to find young stars spiraling into the center of a massive star cluster in the Small Magellanic Cloud, a satellite galaxy of the Milky Way. The outer arm of the spiral in this huge, oddly shaped stellar nursery, called NGC 346, could be fueling star formation in a motion similar to the river of gas and stars. It is an effective way to feed star birthsay the researchers.
The work was featured in an article published in the magazine The Astrophysical Journal.
The researchers determined the motion of stars in NGC 346 in two different ways. Using Hubble, Sabbi and her team measured changes in star positions over 11 years. The stars in this region move at an average speed of 3,200 kilometers per hour, which means that in 11 years they travel 320 million kilometers. This is about twice the distance between the Earth and the Sun.
Different methods, same conclusion
But this cluster is relatively far away, within a neighboring galaxy. This means that the observed movement is very small and therefore difficult to measure. These remarkably precise observations were only possible thanks to Hubble’s excellent resolution and high sensitivity. Additionally, Hubble’s three-decade history of observations provides a baseline for astronomers to track celestial movements over time.
The second team, led by Peter Zeidler of AURA/STScI for ESA, used the VLT’s Multi Unit Spectroscopic Explorer (MUSE) instrument to measure radial velocity, which determines whether an object is approaching or moving away from an observer. .
“What was really amazing was that we used two completely different methods with different setups and came to the same conclusion independently,” Zeidler said. “With Hubble you can see the stars, but with MUSE we can also see the movement of gas in the third dimension, and that supports the theory that everything is spiraling inward.”
But why a spiral? “A spiral is really the right natural way to fuel star formation from the outside to the center of the cluster,” Zeidler explained. “It’s the most efficient way for stars and gas that further fuel star formation to move toward the center.”
Half of the Hubble data for this study of the NGC 346 cluster is archival. The first sightings were made 11 years ago. They have recently been repeated to track the movement of stars over time. Given the telescope’s longevity, the Hubble Data Archive now contains more than 32 years of astronomical data, fueling unprecedented long-term studies.
“The Hubble Archive is truly a gold mine,” Sabbi said. “There are many interesting regions of star formation that Hubble has observed over the years. Since Hubble works so well, we can actually repeat those observations. This could really advance our understanding of star formation.
Observations with the NASA/ESA/CSA James Webb Space Telescope should provide a resolution of lower mass stars in the cluster, giving a more holistic view of the region. During Webb’s lifetime, astronomers will be able to repeat this experiment and measure the motion of low-mass stars. They will then be able to compare high-mass and low-mass stars to finally know the full extent of the dynamics of this nursery.