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Glowing Ghosts: Astronomers Hunt for the Milky Way’s Hidden Supernova Remnants

Animation showing the formation of a supernova remnant. New research, which will utilize advanced telescopes and blend machine learning with manual observation, hopes to double the number of known supernova remnants.

A new study to identify more supernova remnants in the Milky WayThe Milky Way is the galaxy that contains our Solar System and is part of the Local Group of galaxies. It is a barred spiral galaxy that contains an estimated 100-400 billion stars and has a diameter between 150,000 and 200,000 light-years. The name "Milky Way" comes from the appearance of the galaxy from Earth as a faint band of light that stretches across the night sky, resembling spilled milk.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>Milky Way aims to close the gap between expected and identified remnants. Utilizing advanced technology and educational outreach, the research holds significance for understanding our galaxy and promoting STEM education.

A West Virginia University astronomer is searching the Milky Way for debris left behind by supernovas, the violent explosions that occur when massive stars die.

After a supernova explosion, material that was part of the star expands outward, forming a shell or “remnant.” According to Loren Anderson, professor at the Eberly College of Arts and Sciences, studying supernova remnants is “essential for understanding the properties and dynamics of our galaxy — but there is a severe discrepancy in the number of supernova remnants we would expect to see compared to the relatively low number we have detected.”

Around 300 to 400 supernova remnants have been identified in the Milky Way, but studies of similar galaxies suggest closer to 1,000 supernova remnants likely exist in this galaxy. With $331,170 in National Science Foundation funding, Anderson will close that gap. He believes he could double the number of known supernova remnants by the end of his three-year study.

Timothy Faerber and Loren Anderson

Timothy Faerber, a West Virginia University graduate student, and Professor Loren Anderson study supernova remnants to further understand the properties and dynamics of the galaxy. Credit: WVU Photo/Nathaniel Godwin

Challenges and Methodology

Identifying supernova remnants requires sensitive data and can be challenging. For instance, Anderson said supernova remnants are often confused with the much more numerous HII regions, clouds of dense plasmaPlasma is one of the four fundamental states of matter, along with solid, liquid, and gas. It is an ionized gas consisting of positive ions and free electrons. It was first described by chemist Irving Langmuir in the 1920s.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>plasma that surround massive stars.

Working with graduate student Timothy Faerber of Potomac, Maryland, Anderson will use radio wavelength data from the Very Large Array and MeerKAT telescopes to identify supernova remnant candidates, combining machine-learning software with old-school scanning “by eye.”  This method will enable Anderson to discover new supernova remnants, confirm suspected supernova remnants, and remove incorrectly identified remnants from the catalog.

“This study is timely,” said Anderson, astronomy professor and member of the WVU Center for Gravitational Waves and Cosmology. “Recent data from MeerKAT allow for the most sensitive search for supernova remnants yet, and recent works have identified hundreds of possible supernova remnants that need to be confirmed. We have already begun an initial search of a few square degrees of GPSGPS, or Global Positioning System, is a satellite-based navigation system that provides location and time information anywhere on or near the Earth's surface. It consists of a network of satellites, ground control stations, and GPS receivers, which are found in a variety of devices such as smartphones, cars, and aircraft. GPS is used for a wide range of applications including navigation, mapping, tracking, and timing, and has an accuracy of about 3 meters (10 feet) in most conditions.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>GPS data from the MeerKAT telescope and the results are incredibly promising.”

Loren Anderson

Loren Anderson, professor, astronomy, WVU Eberly College of Arts and Sciences. Credit: WVU Photo

He said his methodology is well suited to discovering supernova remnants in crowded parts of the inner galaxy, increasing the odds of finding newer remnants that still haven’t spread out or dispersed far. Those “young, compact” remnants are especially valuable to researchers interested in supernovas’ impacts on interstellar matter and radiation.

The Significance of New Findings

According to Anderson, every newly confirmed remnant is an opportunity for detailed study. It might permit a chance to create three-dimensional reconstructions of the material flung out by a supernova explosion, for example, or to learn more about what the shock of a supernova does to other matter in the galaxy.

He added the project also marks an opportunity to find supernova remnants that are associated with pulsars. A pulsarFirst observed at radio frequencies, a pulsar is a rotating neutron star that emits regular pulses of radiation. Astronomers developed three categories for pulsars: accretion-powered pulsars, rotation-powered pulsars, and nuclear-powered pulsars; and have since observed them at X-ray, optical, and gamma-ray energies.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>pulsar is the ultra-dense, rotating core that remains after a star has exploded in a supernova. Even though pulsars and supernova remnants are both created by supernova explosions, they’re rarely found in association.

Pulsars are important because their highly precise “pulsing” allows them to serve as cosmic clocks for astronomers, including Anderson’s WVU colleagues who in June made international headlines for discovering ripples in spacetime, thanks in large part to their study of pulsars.

Educational Outreach

Anderson’s research group will work with the West Virginia Science Public Outreach Team, which trains WVU undergraduates to deliver STEM presentations to K-12 students, making classrooms part of current, cutting-edge science that’s happening locally.

None of WV SPOT’s existing presentations showcase supernovas, Anderson said, so they will develop a new module that also provides a general overview of radio telescopes. The presentation will incorporate supernova remnant observations that will be acquired live from a telescope at the observatory in Green Bank, giving students hands-on, real-time experience with astronomy.

Funding: National Science Foundation

Source: SciTechDaily