Unusual Supernova Opens a Rare Window on the Collapse of a Star

The above image shows a long exposure of the SOAR telescope with overlaid illustrations of a highly magnetized neutron star (top left) and an accreting black hole (top right). (Image: D. Maturana & NOAO/AURA/NSF; Overlay (top left): NASA/Penn State University/Casey Reed; (top right): NASA Goddard Space Flight Center)
The above image shows a long exposure of the SOAR telescope with overlaid illustrations of a highly magnetized neutron star (top left) and an accreting black hole (top right). (Image: D. Maturana & NOAO/AURA/NSF; Overlay (top left): NASA/Penn State University/Casey Reed; (top right): NASA Goddard Space Flight Center)

An unusual supernova studied by multiple telescopes, including the SOAR telescope and other telescopes at the National Science Foundation’s (NSF) Cerro Tololo Inter-American Observatory (CTIO) and NSF’s Kitt Peak National Observatory (KPNO), is thought to herald the birth of a new black hole or neutron star, caught at the exact moment of its creation.

Observations made with facilities ranging from X-rays to optical and radio wavelengths were used to understand this remarkable event. These multi-messenger observations give astronomers a rare glimpse into the physics at play during the creation of a black hole or neutron star.

A mysterious bright glow

On June 16, 2018, a sky survey telescope in Hawai’i alerted the astronomical community to the sudden appearance of a new object in the sky. It was similar to a supernova, except that it brightened, and then faded, faster than a typical supernova, and was intrinsically brighter at its peak. A supernova (from nova, meaning “new” star) is a sudden explosion of a massive star which has reached the end of its lifetime, leading to the formation of a black hole or neutron star.

The above image shows a long exposure of the SOAR telescope with overlaid illustrations of a highly magnetized neutron star (top left) and an accreting black hole (top right). (Image credit: D. Maturana & NOAO/AURA/NSF; Overlay (top left): NASA/Penn State University/Casey Reed; (top right): NASA Goddard Space Flight Center)

The above image shows a long exposure of the SOAR telescope with overlaid illustrations of a highly magnetized neutron star (top left) and an accreting black hole (top right).
(Image: D. Maturana & NOAO / AURA / NSF; Overlay (top left): NASA / Penn State University / Casey Reed; (top right): NASA Goddard Space Flight Center)

The transient object, assigned the designation AT2018cow, was immediately nicknamed “the Cow” based on the final 3 letters of its name. “The Cow” is located in a relatively nearby galaxy — only 200 million light years away from our own Milky Way galaxy in the direction of the constellation Hercules.

It takes a team

Immediately after receiving the alert, an international research team led by Raffaella Margutti (Northwestern University) leaped into action and began observing the unusual source across the electromagnetic spectrum — at X-ray, optical, infrared, and radio wavelengths. Telescopes around the world contributed to the effort using spectroscopy to decode the nature of the source.

Among the telescopes that contributed was the Southern Astrophysical Research Telescope (SOAR) in Chile, whose instruments obtained spectra of the Cow. With spectra, which spread out the light in the form of a rainbow, astronomers could quickly confirm that matter was expanding from the object at up to 10 percent the speed of light. Régis Cartier, who made the SOAR observations, said:

In addition to the SOAR telescope, other telescopes at NSF’s CTIO and KPNO imaged the object and contributed to a broader picture as the Cow faded away.

A nearly naked Cow

Because the collapsed star was surrounded by a relatively small amount of debris, the team was able to peer through the debris and get a glimpse of the object’s “central engine.” This rare event will help astronomers better understand the physics at play within the first moments of the creation of a black hole or neutron star. The results were presented at this week’s meeting of the American Astronomical Society in Seattle, Washington. Giacomo Terreran (Northwestern University), who led the CTIO observations, said:

A whole new world of transients

Although a supernova like the Cow has never been seen before, Cartier expects that astronomers will detect larger numbers of such rare events in the future. Now that surveys are searching for sources that vary on a wider range of timescales, “we’ve already discovered a whole family of fast transients that we didn’t know existed,” noted Cartier. The SOAR telescope is gearing up to help us understand these new events. Dr. Jay Elias, Director of SOAR, said:

The LSST is a new telescope being built on the same mountaintop as the SOAR telescope with major funding from NSF: It will conduct a 10-year survey of the sky with a special emphasis on transient events. The SOAR telescope, located in Chile, is operated by Cerro Tololo Inter-American Observatory, a division of National Optical Astronomical Observatory, which is operated by the Association of Universities for Research in Astronomy Inc. under a cooperative agreement with the National Science Foundation.

Image from the Dark Energy Camera Legacy Survey (DECaLS) with cross hairs indicating the location of the AT2018cow event in the host galaxy, CGCG 127-68. Image credit: Color image from the Imagine Viewer, created by Dustin Lang, for the Legacy Surveys project (see legacysurvey.org/viewer).

Image from the Dark Energy Camera Legacy Survey (DECaLS) with crosshairs indicating the location of the AT2018cow event in the host galaxy, CGCG 127-68. (Image: Color image from the Imagine Viewer, created by Dustin Lang, for the Legacy Surveys project (see legacysurvey.org/viewer)).

The CTIO complex is part of the U.S. National Optical Astronomy Observatory (NOAO), along with the Kitt Peak National Observatory (KPNO) in Tucson, Arizona. NOAO is operated by the Association of Universities for Research in Astronomy (AURA), under cooperative agreement with the National Science Foundation (NSF). NSF is an independent federal agency created by Congress in 1950 to promote the progress of science.

NSF supports basic research and people to create knowledge that transforms the future. CTIO, as part of the AURA Observatory in Chile, operates in Chile under Chilean law, through an Agreement with the University of Chile and with the auspices of the Ministry of Foreign Affairs of Chile.

Provided by: National Optical Astronomy Observatory [Note: Materials may be edited for content and length.]

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