Astronomers discover new supernova magnified by gravitational lensing

Einstein’s general theory of relativity combines time and space into a single entity called spacetime. This theory suggests that massive objects, such as galaxies or galaxy clusters, can cause spacetime to curve.

Gravitational lensing provides a rare but observable demonstration of Einstein’s theory. When a large celestial body has enough mass, it can bend light as it travels through spacetime, similar to a magnifying lens. Scientists can use these light distortions to observe objects that would otherwise be too distant and faint to detect.

Recently, a team of international scientists, including University of Maryland astronomer Igor Andreoni, made an exceptional discovery of a gravitationally lensed supernova called “SN Zwicky.” Situated over 4 billion light years away, this supernova was magnified by almost 25 times due to a foreground galaxy acting as a lens.

This discovery presents a unique opportunity for astronomers to gain insights into the inner cores of galaxies, dark matter, and the mechanisms driving the expansion of the universe. The researchers published their comprehensive analysis, spectroscopic data, and imaging of SN Zwicky in the scientific journal Nature Astronomy on June 12, 2023.

“The identification of SN Zwicky not only demonstrates the incredible capabilities of modern astronomical instruments but also represents a significant advancement in our pursuit to comprehend the fundamental forces that shape our universe,” stated Ariel Goobar, the lead author of the research paper and the director of the Oskar Klein Center at Stockholm University.

Credit: University of Maryland

SN Zwicky was initially discovered by the Zwicky Transient Facility (ZTF), which promptly identified it as an intriguing object due to its exceptional brightness. The scientific team then utilized adaptive optics instruments on the W.M. Keck Observatory, the Very Large Telescopes, and NASA’s Hubble Space Telescope to observe four distinct images of SN Zwicky, captured from various positions in the sky. These observations confirmed that the supernova’s remarkable luminosity was a result of gravitational lensing.

Igor Andreoni, a postdoctoral associate at the University of Maryland’s Department of Astronomy and NASA’s Goddard Space Flight Center, explained that supernovae like SN Zwicky play a vital role in helping scientists gauge cosmic distances.

Zooming in to supernova Zwicky: starting from a small portion of the Palomar ZTF camera, one out of 64 “quadrants”, each one containing tens of thousands of stars and galaxies, the zoom in takes us to detailed explorations carried out with the larger and sharper VLT and Keck telescopes in Chile and Hawai’i respectively. On the best resolved Keck images, the four nearly identical “copies” of supernova Zwicky can be seen. The multiple images arise due to the warping of space caused by a foreground galaxy, also seen in the center and approximately half-way between the site of the supernova explosion and Earth. Credit: J. Johansson

SN Zwicky not only benefits from gravitational lensing magnification but also belongs to a category of supernovae referred to as “standard candles.” These supernovae have well-established luminosities that enable scientists to determine distances in space. By comparing the brightness of these standard candles, astronomers can independently measure distances without directly studying the galaxies themselves, akin to comparing the brightness of candles in a dark room.

Apart from serving as a valuable tool for measuring cosmic distances, SN Zwicky opens up new avenues of research for scientists investigating various aspects of galaxies, including dark matter—the elusive substance that constitutes the majority of matter in the universe but does not emit, reflect, or absorb light.

Moreover, lensed supernovae like SN Zwicky hold great promise for studying dark energy, the enigmatic force responsible for the accelerated expansion of the universe, as well as refining models that describe the universe’s expansion, such as determining the Hubble constant, which quantifies the rate of the universe’s expansion.

As Andreoni, who is anticipating the opening of the Vera Rubin Observatory in Chile, highlights, the team’s success in detecting and analyzing SN Zwicky represents just the beginning. The upcoming observatory, scheduled to commence full operations in 2024, will build upon these findings by capturing multiple images of the entire visible sky, enabling the search for additional supernovae and asteroids.

Andreoni believes that the strategy employed to discover SN Zwicky, focusing on the bigger picture rather than specific targets, will continue to yield vast amounts of data on celestial events. This approach, leveraging broad and untargeted optical surveys of the sky, will enable scientists to delve into the transient nature of the universe with unprecedented depth.

“This discovery sets the foundation for uncovering more rare lensed supernovae in future large-scale surveys, which will enhance our understanding of transient astronomical phenomena like supernovae and gamma-ray bursts,” Andreoni remarked. “We eagerly anticipate further unexpected discoveries through extensive exploration of the transient sky using approaches like the one that led us to SN Zwicky. It will enable us to probe the depths of the transient universe like never before.”

Source: University of Maryland

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