Research reveals clues to conditions of early universe

Using massive data sets collected with NASA’s James Webb Space Telescope, a research team led by an astronomer at Rutgers University in New Brunswick uncovers clues about conditions in the early universe .

The team cataloged the ages of stars in the Wolf-Lundmark-Melotte (WLM) galaxy, creating the most detailed picture to date, according to the researchers. WLM, neighboring the Milky Way, is an active star formation center that includes ancient stars formed 13 billion years ago.

“By looking so deeply and seeing so clearly, we were able to turn back time — effectively,” said Kristen McQuinn, an assistant professor in the Department of Physics and Astronomy in the School of Arts and Sciences, who led the ‘study. research, described in The Astrophysics Journal. “Basically, you’re doing a sort of archaeological dig to find the very low-mass stars that formed early in the history of the universe.”

McQuinn credited the Amarel high-performance computing cluster run by the Rutgers Office of Advanced Research Computing for allowing the team to calculate the galaxy’s stellar development history. One aspect of the research involved taking a massive calculation and repeating it 600 times, McQuinn said.

This major computational effort also helped confirm the telescope’s calibrations and data processing procedures, which will benefit the broader scientific community, she added.

So-called “low mass” galaxies are of particular interest to McQuinn. Because they are thought to have dominated the early universe, they allow researchers to study star formation, the evolution of chemical elements, and the impact of star formation on the gas and structure of a galaxy. Faint and distributed across the sky, they constitute the majority of galaxies in the local universe. Advanced telescopes such as the Webb allow scientists to observe more closely.

WLM – an “irregular” galaxy, meaning it does not have a distinct shape, such as a spiral or ellipse, was discovered by German astronomer Max Wolf in 1909 and further characterized in 1926 by Swedish astronomer Knut Lundmark and British astronomer. Philibert Jacques Melotte. It is positioned on the outskirts of the Local Group, a dumbbell-shaped group of galaxies that includes the Milky Way.

Being on the edge of the Local Group protected WLM from the ravages of mixing with other galaxies, leaving its star population in a pristine and useful state for study, McQuinn noted. WLM is also interesting to astronomers because it is a dynamic and complex system containing a lot of gas, allowing it to actively form stars.

To formulate the galaxy’s star formation history (the rate at which stars were born at different times in the universe), McQuinn and his team used the telescope to painstakingly focus on swathes of sky containing hundreds of thousands of individual stars. To determine the age of a star, they measured its color – an indicator of temperature – and its brightness.

“We can use what we know about stellar evolution and what those colors and brightnesses indicate to age the stars in the galaxy,” McQuinn said, adding that the researchers then counted stars of different ages and mapped the birth rate of stars throughout the history of the universe. “What you get is an idea of ​​how old this structure is that you’re looking at.”

Cataloging stars in this way showed researchers that WLM’s star production capabilities fluctuated over time. The team’s observations, which confirm earlier assessments by scientists using the Hubble Space Telescope, show that the galaxy produced stars early in the history of the universe over a period of 3 billion years. He stopped for a moment, then started again.

McQuinn said she thinks the pause was caused by specific conditions at the beginning of the universe.

“The universe at the time was really hot,” she said. “We think that the temperature of the universe ended up warming the gas in this galaxy and kind of turned off star formation for a while. The cooling period lasted a few billion years, and then star formation of stars has resumed.”

The research is part of NASA’s Early Release Program, in which designated scientists work with the Space Telescope Science Institute and conduct research designed to highlight Webb’s capabilities and help astronomers prepare for future observations.

NASA launched the Webb telescope in December 2021. The large-mirror instrument orbits the sun a million miles from Earth. Scientists compete for time on the telescope to study a multitude of topics, including conditions in the early universes, the history of the solar system and the search for exoplanets.

“A lot of science that hasn’t yet been done through this program is going to come out of this program,” McQuinn said.

Other Rutgers researchers participating in the study included Max Newman, a doctoral student, and Roger Cohen, a postdoctoral associate, both in the Department of Physics and Astronomy in the Rutgers School of Arts and Sciences.