Astronomers have unveiled a new panorama of the Andromeda Galaxy, revealing details about its star population and evolutionary journey. The research, led by Zhuo Chen, a postdoctoral researcher in astronomy at the University of Washington, was published in a paper titled "PHAST. The Panchromatic Hubble Andromeda Southern Treasury. I. Ultraviolet and Optical Photometry of over 90 Million Stars in M31."
Researchers at the University of Washington presented their findings at a meeting of the American Astronomical Society. "The asymmetry between the two halves—now visually evident in this image—is incredibly intriguing," Zhuo Chen said.
The panoramic image is the result of two Hubble observation programs: the Panchromatic Hubble Andromeda Treasury (PHAT), which began about a decade ago and mapped the northern half of the galaxy, and the Panchromatic Hubble Andromeda Southern Treasury (PHAST), which added images of approximately 100 million stars in the southern half. Together, these programs cover the entire galactic disk of Andromeda, which is seen almost edge-on and is tilted at an angle of 77 degrees, revealing its distinctive structural features, as reported by El Periódico.
"With Hubble, we can get huge details about what is happening at a holistic scale across the disk of the galaxy. You can't do that with any other large galaxy," said Ben Williams, principal investigator at the University of Washington.
The Andromeda Galaxy, also known as Messier 31 or M31, is a barred spiral galaxy similar in size and structure to our own Milky Way. Located approximately 2.5 million light-years from Earth, it is the Milky Way's most important neighboring galaxy, according to Universe Today.
Photographing the Andromeda Galaxy was a Herculean task that required ten years, around 1,000 orbits of the Hubble Space Telescope, and more than 600 overlapping snapshots. This effort resulted in a mosaic composed of at least 2.5 billion pixels, as reported by Phys.org. The final image reveals approximately 200 million stars and extends six times the apparent diameter of the full Moon in the night sky.
The southern region of the Andromeda Galaxy, mapped by the PHAST program, is structurally unique and more sensitive to the galaxy's merger history than the northern disk mapped by PHAT. It appears more disturbed, indicating the effects of Andromeda's merger history.
Daniel Weisz from the University of California, Berkeley, described Andromeda as a "train wreck," noting that "it looks like it has been through some kind of event that caused it to form a lot of stars and then just shut down," according to Phys.org. "Andromeda looks like a transitional type of galaxy that's between a star-forming spiral and a sort of elliptical galaxy dominated by aging red stars," Weisz added,
"This detailed look at the resolved stars will help us to piece together the galaxy's past merger and interaction history," Ben Williams said. The total population of the Andromeda Galaxy is estimated to be about one trillion stars, with many less massive stars falling below Hubble's sensitivity limit. Hubble can only detect stars that are brighter than our Sun, and many low-mass stars fall below its sensitivity threshold.
The map shows approximately 200 million of the brightest stars in optical, ultraviolet, and partially infrared light. Andromeda seems to be more highly populated with younger stars and features like coherent streams of stars, indicating its active star formation and interaction history. The large populations of younger stars suggest that it has gone through more interactions and mergers in recent times than the Milky Way galaxy, as reported by Phys.org.
Thanks to this mapping, astronomers can now decipher the history of the Andromeda Galaxy, including its collisions and interaction with the Milky Way, and distinguish between competing scenarios of its merger with other galaxies. Hubble's new findings will support future observations by NASA's James Webb Space Telescope and the upcoming Nancy Grace Roman Space Telescope, continuing the legacy of the Hubble Space Telescope and inspiring new research.
The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency (ESA) and is recognized for its major contributions to astronomy. The data now open up new possibilities for astronomers worldwide to explore the Andromeda Galaxy and its tumultuous history, helping to refine models of its evolution, as reported by Scinexx.
The article was written with the assistance of a news analysis system.