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Astronomers have once again combined the observing powers of NASA’s James Webb Space Telescope and Hubble Space Telescope to create one of the most detailed and colorful portraits of the cosmos, just in time for the holidays.
The new image, by the research team that also includes astronomer Dr. Lifan Wang of Texas A&M University, called the Christmas Tree Galaxy Cluster, combines visible light from Hubble with infrared light detected by Webb to demonstrate MACS0416, a cluster of galaxies about 4.3 billion light-years away. Soil. Because the cluster is able to magnify light from more distant background galaxies through a phenomenon known as gravitational lensing, it has allowed researchers to identify magnified supernovae and even very highly magnified individual stars.
“We call MACS0416 the Christmas Tree Galaxy Cluster, both because it is so colorful and because of the flickering lights we find within it,” says astronomer Dr. Haojing Yan of the University of Missouri, lead author of one of the two papers describing the scientific results. . The paper, co-authored by Wang, has been accepted for publication in The Astrophysical Journal.
Wang, a member of the Texas A&M Department of Physics and Astronomy and the George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy since 2006, is part of a time-domain astronomy team using JWST to discover the first-ever supernovae, including the oldest ever dates from a time when the universe was more than 3 billion years old. The international collaboration, known as the Prime Extragalactic Areas for Reionization and Lensing Science (PEARLS), is led by astronomer Dr. Rogier Windhorst of Arizona State University and is credited with collecting the data that led to the discoveries.
One of the team’s tactics is to use Webb’s unparalleled observational power to look for objects that vary in perceived brightness over time, known as transients. In a 2017 white paper published ahead of JWST’s launch, Wang and his co-authors predicted that the telescope would find a few such transients in a single shot using its powerful main camera, the Near Infrared Camera (NIRCam). Wang cites the MACS0416 image and the 14 transients it contains as positive evidence, noting that the discoveries exceed the team’s predictions.
“The JWST discovers a large number of transient objects, mainly supernovae, in the universe,” Wang said. “Not only does it find supernovas, it has also found stars in distant galaxies that are magnified by the gravitational field of nearby foreground galaxies.”
The discoveries were made through repeated observations of a region of sky in the direction of the cluster MACS0416. The Northern Ecliptic Pole (NEP), a region that JWST can continuously reference and collect data throughout the year, is ideal for acquiring time-domain observations in the future. Wang says the unprecedented sensitivity means that some supernovae, such as those from the explosions of white dwarf stars, can be detected throughout the universe, even back to the epoch when the universe was just beginning to form its first stars.
“There are two fundamental questions in astronomy: how did the first stars form and what is the nature of the forces driving the expansion of the universe?” Wang said. “The transients that JWST can discover will provide the data needed to answer these questions.
‘These discoveries show that JWST is the most powerful tool for studying the faint transients at the cosmic dawn, when the universe emerges from the dark age without stars to the current epoch. The supernovae it observes could trace the process of the first stars and the expansion of the universe to a time when the universe was less than 1 billion years old.”
Wang says some of these supernovae are likely the result of the death of low-mass stars, which evolve into white dwarfs and explode in thermonuclear explosions. Thanks to the lens stars, individual stars in the distant universe can be studied. These early stars are also likely to be very massive stars that produce extremely bright transients due to the so-called instability process of pair production.
“We expect that these ‘routinely discoverable’ transients will have great potential in answering the questions about the end of the cosmic dark age and the physics of the expansion of the dark universe,” Wang said.
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