NASA’s Roman space telescope Nancy Grace will study dim currents of stars that extend far beyond the apparent edges of many galaxies. Missions such as the Hubble Space Telescope and James Webb would need to patch up hundreds of small images to see these structures around nearby galaxies in their entirety. Roman will do it in a single snapshot. Astronomers will use these observations to explore how galaxies grow and their species dark matter.
Stellar currents look like ethereal hairs that extend outward from certain galaxies, drifting peacefully through space as part of a halo – a spherical region that surrounds a galaxy. But these stellar flights are signs of an ancient drama on a cosmic scale that serves as a fossil record of a galaxy’s past. Studying them turns astronomers into galactic archaeologists.
Particularly elusive star currents that formed when The Milky Way swayed stars from globular star clusters have been discovered before, but they have never been found in other galaxies. They are weaker because they contain fewer stars, making them much more difficult to detect in other, more distant galaxies.
Novel can detect them in several of our nearby galaxies for the first time ever. The mission’s broad, sharp, deep vision should even reveal individual stars in these huge, dark structures. IN a previous studyPearson led the development of an algorithm to systematically search for stellar currents derived from globular clusters in adjacent galaxies.
Starkenburg’s new study complements the picture by predicting that Roman should be able to detect dozens of currents in other galaxies derived from dwarf galaxies, providing unparalleled insight into how galaxies grow.
“It’s exciting to learn more about our Milky Way, but if we really want to understand galaxy formation and dark matter, we need a larger sample size,” said Starkenburg. “Studying stellar currents in other galaxies with Roman will help us see the big picture.”
The Nancy Grace Roman Space Telescope is operated at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, with the participation of NASA’s Jet Propulsion Laboratory and Caltech / IPAC in Southern California, the Space Telescope Science Institute in Baltimore, and a scientific team of scientists from different research institutions. The primary industrial partners are Ball Aerospace and Technologies Corporation of Boulder, Colorado; L3Harris Technologies in Melbourne, Florida; and Teledyne Scientific & Imaging in Thousand Oaks, California.
“Halos are mostly made of stars that have been removed from other galaxies,” said Tjitske Starkenburg, a postdoctoral fellow at Northwestern University in Evanston, Illinois, who studied the potential of the novel in this area. “The wide, deep images of the novel will be sharp enough for us to dissolve individual stars in the halos of other galaxies, making it possible to study stellar currents in a large number of galaxies for the first time.”
The team, led by Starkenburg, will share their findings at the American Astronomical Society’s 240th meeting in Pasadena, California, today.
Galactic cannibalism, stolen stars
Simulations support the theory that galaxies partially grow by devouring smaller groups of stars. A dwarf galaxy captured into orbit by a larger galaxy is distorted by gravity. Its stars drizzle out and trace arcs and loops around the larger galaxy until they eventually become its newest members.
“As individual stars leak out of the dwarf galaxy and fall into the more massive one, they form long, thin streams that remain intact for billions of years,” said Sarah Pearson, a Hubble Postdoctoral Fellow at New York University in New York. the main author of a separate study on the mission’s projected observations in this area. “So stellar currents have secrets from the past and can illuminate billions of years of evolution.”
Astronomers have captured this cannibalistic process at random using telescopes such as the ESA’s (European Space Agency) Gaia satellite, which is fine-tuned to measure the positions and movements of the stars in our Milky Way galaxy. The novel will expand these observations by making similar measurements of stars in both the Milky Way and other galaxies.
The Milky Way is home to at least 70 star currents, which means that it has probably eaten up at least 70 dwarf galaxies or globular clusters – groups of hundreds of thousands of gravitational stars. Romance’s Milky Way images can allow astronomers to put together snapshots in time to show the movements of stars. It will help us learn about what dark matter – invisible matter that we can only discover through its gravitational effects on visible objects – is made of.
One theory suggests that dark matter is “cold” or consists of heavy, sluggish particles. If so, it should clump together in galaxy halos, which would disrupt stellar currents in ways Roman could see. By either detecting or excluding these distortions, Roman was able to limit the candidates to what dark matter could be made of.
Astronomers are also looking forward to studying stellar currents in several of the Milky Way’s nearby galaxies. They are not well studied in other galaxies because they are so weak and far away. They are also so large that they can wrap around an entire galaxy. It takes an unmatched panoramic view like Romans to capture images that are both large and detailed enough to see.
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