With images from the Hubble Space Telescope, we have new information here in the Milky Way about our closest neighboring galaxy, Andromeda.
Researchers unveiled the most comprehensive survey of the galaxy to date in a paper published Thursday in the Astronomical Physics journal.
As we learn more about the spiral-shaped Andromeda, we also learn more about our own spiral-shaped galaxy.
“That’s because Earth is embedded inside the Milky Way. This is like trying to understand the layout of New York City by standing in the middle of Central Park,” explained a press release from the University of Washington.
Here on Earth, we can sometimes see Andromeda with our naked eye. Yet, even though it’s the closest galaxy to ours, it’s still approximately 2.5 million light years away from us. That’s according to the Hubble Telescope’s namesake, astronomer Edwin Hubble, who determined the distance a century ago.
While experts believe that the Milky Way and Andromeda formed around the same time and they are in the “same cosmological neighborhood,” it appears that Andromeda has a higher number of younger stars. Washington University also said it appears to have “unusual features like coherent streams of stars,” that imply more recent active star formation than in our own galaxy.
The work published this week “yields new clues to the evolutionary history of Andromeda,” that differentiate it from the Milky Way, according to the university.
“With Hubble we can get into enormous detail about what’s happening on a holistic scale across the entire disk of the galaxy. You can’t do that with any other large galaxy,” said principal investigator Benjamin Williams, a UW research associate professor of astronomy.
Two Hubble programs were required to photograph Andromeda and more than 1,000 orbits of the telescope were needed to complete the current map. This process took place over more than a decade.
First, the Panchromatic Hubble Andromeda Treasury program brought images that were obtained at near-ultraviolet, visible and near-infrared wavelengths using instruments aboard Hubble to photograph the northern half of the galaxy. Then, the Panchromatic Hubble Andromeda Southern Treasury brought phase added images of approximately 100 million stars in the southern half of Andromeda.
“This southern region is structurally unique and more sensitive to the galaxy’s merger history than the northern disk mapped earlier,” said the University of Washington.
Overall, the mosaic includes 2.5 billion pixels.
“The asymmetry between the two halves – now visually evident in this image – is incredibly intriguing,” said Zhuo Chen, a UW postdoctoral researcher in astronomy and lead author of the recent paper, which was presented in Maryland Thursday at a meeting of the American Astronomical Society. “It’s fascinating to see the detailed structures of an external spiral galaxy mapped over such a large, contiguous area.”
Now, astronomers can use the mosaic to better understand Andromeda and help them research different scenarios regarding its merger with other galaxies.
“This ambitious photography of the Andromeda galaxy sets a new benchmark for precision studies of large spiral galaxies,” Chen said.
Hubble launched nearly 35 years ago, in April 1990. It is expected to operate at least until the late 2020s.