A Cosmic Christmas: 14 Transient Objects Discovered in Distant Galaxy Cluster

MACS 0416 (Hubble ACS and WFC3 + Webb NIRCam Image)

This panchromatic view of galaxy cluster MACS0416 was created by combining infrared observations from NASA’s James Webb Space Telescope with visible-light data from NASA’s Hubble Space Telescope. To make the image, in general the shortest wavelengths of light were color-coded blue, the longest wavelengths red, and intermediate wavelengths green. Credit: NASA, ESA, CSA, STScI, Jose M. Diego (IFCA), Jordan C. J. D’Silva (UWA), Anton M. Koekemoer (STScI), Jake Summers (ASU), Rogier Windhorst (ASU), Haojing Yan (University of Missouri)

Astronomers used NASA’s James Webb Space Telescope to discover 14 transient objects in the “Christmas Tree Galaxy Cluster,” MACS0416, about 4.3 billion light-years away. Transients, which briefly brighten and then fade, reveal information about distant stars and the universe’s structure.

An international team of scientists, led by University of Missouri’s Haojing Yan, used NASA’s James Webb Space Telescope (JWST) to discover 14 new transient objects during their time-lapse study of galaxy cluster MACS0416 — located about 4.3 billion light-years from Earth — which they’ve dubbed as the “Christmas Tree Galaxy Cluster.”

This side-by-side comparison of galaxy cluster MACS0416 as seen by the Hubble Space Telescope in optical light (left) and the James Webb Space Telescope in infrared light (right) reveals different details. Both images feature hundreds of galaxies, however, the Webb image shows galaxies that are invisible or only barely visible in the Hubble image. This is because Webb’s infrared vision can detect galaxies too distant or dusty for Hubble to see. Credit: NASA, ESA, CSA, STScI

Understanding Transient Objects

“Transients are objects in space, like individual stars, that appear to suddenly brighten by orders of magnitudes and then fade away,” said Yan, an associate professor in the Department of Physics and Astronomy. “These transient objects appear bright for only a short period of time and then are gone; it’s like we’re peering through a shifting magnifying glass. Right now, we have this rare chance that nature has given us to get a detailed view of individual stars that are located very far away. While we are currently only able to see the brightest ones, if we do this long enough — and frequently enough — we will be able to determine how many bright stars there are, and how massive they are.”

MACS 0416 Mothra Pullout (Hubble ACS and WFC3 + Webb NIRCam Image)

This image of galaxy cluster MACS0416 highlights one particular gravitationally lensed background galaxy, which existed about 3 billion years after the Big Bang. That galaxy contains a transient, or object that varies in observed brightness over time, that the science team nicknamed “Mothra.” Mothra is a star that is magnified by a factor of at least 4,000 times. The team believes that Mothra is magnified not only by the gravity of galaxy cluster MACS0416, but also by an object known as a “milli-lens” that likely weighs about as much as a globular star cluster. Credit: NASA, ESA, CSA, STScI, Jose M. Diego (IFCA), Jordan C. J. D’Silva (UWA), Anton M. Koekemoer (STScI), Jake Summers (ASU), Rogier Windhorst (ASU), Haojing Yan (University of Missouri)

Advanced Observations with JWST

Using the advanced technological capabilities of the JWST, Yan and his team, including Mizzou graduate student Bangzheng Sun, confirmed what’s causing the galaxy cluster’s “flickering lights” or transients that scientists first saw years ago using NASA’s Hubble Space Telescope.

“We’re calling MACS0416 the Christmas Tree Galaxy Cluster, both because it’s so colorful and because of the flickering lights we find within it,” Yan said. “We can see so many transients in certain regions of this area because of a phenomenon known as gravitational lensing, which is magnifying galaxies behind this cluster.”

A color composite image of MACS0416 using the data from four sets of images taken by JWST of the galaxy cluster over a period of 126 days, or about four months. The regions where the transients are found are also marked. Photo courtesy of Bangzheng Sun. Credit: University of Missouri

Breakthrough Findings

The team discovered the transients by studying four sets of images taken by JWST of the galaxy cluster over a period of 126 days, or about four months. Yan is particularly excited that two of the transients are supernovae — stars that are at the end of their lifespans — because the team can use them to study the supernovae’s host galaxies.

“The two supernovae and the other twelve extremely magnified stars are of different nature, but they are all important,” Yan said. “We have traced the change in brightness over time through their light curves, and by examining in detail how the light changes over time, we’ll eventually be able to know what kind of stars they are. More importantly, we’ll be able to understand the detailed structure of the magnifying glass and how it relates to dark matter distribution. This is a completely new view of the universe that’s been opened by JWST.”

For more on this research:

“JWST’s PEARLS: Transients in the MACS J0416.1-2403 Field” by Haojing Yan, Zhiyuan Ma, Bangzheng Sun, Lifan Wang, Patrick Kelly, Jose M. Diego, Seth H. Cohen, Rogier A. Windhorst, Rolf A. Jansen, Norman A. Grogin, John F. Beacom, Christopher J. Conselice, Simon P. Driver, Brenda Frye, Dan Coe, Madeline A. Marshall, Anton Koekemoer, Christopher N. A. Willmer, Aaron Robotham, Jordan C. J. D’Silva, Jake Summers, Mario Nonino, Nor Pirzkal, Russell E. Ryan Jr., Rafael Ortiz III, Scott Tompkins, Rachana A. Bhatawdekar, Cheng Cheng, Adi Zitrin and S. P. Willner, Accepted, The Astrophysical Journal.
arXiv:2307.07579