By piercing through thick dust, new details of galaxy M82-also called the Cigar Galaxy-shine through
University of Michigan astronomers were part of a team that has revealed an unprecedented look inside a fascinating galaxy 12 million light-years away using NASA's James Webb Space Telescope, or JWST.
The galaxy, known officially as Messier 82 or M82, was discovered more than 250 years ago and is also known as the Cigar Galaxy due to its elongated shape. Today, it's also characterized as a starburst galaxy, which means stars are forming in the galaxy at a remarkably high rate.
That's particularly true of M82's central region, where the star formation rate is 10 times that of the entire Milky Way. This activity and M82's location make it a one-of-a-kind environment to study, astronomers said. Researchers have been trying to peer deeper into M82 for decades to gain more insights about its history, but past efforts have been hampered by thick clouds of dust that shroud the galaxy's heart.
Equipped with JWST's Near-Infrared Camera, or NIRCam, instrument and 65 hours of observation time, the team has now revealed never-before-seen details with a new image of M82.
"M82 is a delightfully complex system," said Eric Bell, U-M professor of astronomy and co-author of the new report. "Webb's observations will help us address some ongoing mysteries, such as how star formation has moved within M82 over the last few billion years."
The new project revealed more of M82's distended disk structure and millions of individual stars. JWST's high-resolution imaging, specifically of the main plane of the disk, has unlocked vital information for astronomers as they seek to uncover M82's formation history.
"It was really spectacular seeing the galaxy's dust disappear with the JWST image," said Vaishnav Rao, U-M doctoral student in astronomy who also worked on the project. "In the past, we couldn't see individual stars near the galaxy center, but now we can with much more detail, which helps us understand the evolutionary history of the galaxy."
Additionally, the team said the new data will help scientists better understand the current processes occurring within the starburst galaxy.
"M82 is a mess, but it's a beautiful mess. We don't fully understand what's going on, but we do know there's something interesting happening within this starburst galaxy," said lead investigator Adam Smercina, a NASA Hubble Fellow at the Space Telescope Science Institute in Baltimore. "M82 is an ideal galaxy evolution laboratory. With the new Webb data and prior Hubble observations, we've been given a full lab setup-better than we could have ever possibly imagined."
Many earlier missions have observed M82, including NASA's Hubble and retired Spitzer space telescopes. However, the sheer volume of dust within that galaxy limited the amount of information astronomers could acquire. Even JWST has looked at this galaxy before, but not for as long as the new observation run, known as the Cibola survey.
The 65-hour duration of the Cibola survey along with the JWST's infrared sensitivity was an optimal combination that enabled the team to pierce through the galaxy's thick dust.
JWST's near-infrared-light view is a snapshot of a scene that has been evolving over a couple hundred million years. The image contains approximately 16.5 million individual stars dispersed throughout the galaxy. The starlight from these stellar sources is depicted as luminous blue grains. This is only a small portion of the total number of stars astronomers think reside in a galaxy like M82, with the majority too faint to be seen.
"The sheer number of stars that we were able to resolve with Webb is incredible," said co-investigator Benjamin Williams of the University of Washington. "It's a whole different world from what we've been able to see with other telescopes. All of these stars collectively provide a detailed fossil record of the formation and evolution of M82."
The information collected as part of the Cibola study is just one dataset scientists will analyze as they seek to piece together this starburst galaxy's formation history. A holistic approach is essential to continue developing our understanding, the team said.
"Galaxies are such intricate ecosystems that if you truly want to understand them, you have to pull datasets from different missions together," said co-investigator Kristen McQuinn of the Space Telescope Science Institute. "One mission cannot fully answer all of the questions we have about M82. Combining the data collected by different telescopes, like Webb and Hubble, is powerful. When you marry the datasets, you expand what you can probe, and the questions that you can pose are even more complex."
