Capitol News

Recent research led by Michigan State University has made strides in understanding dark comets, a phenomenon within our solar system. Darryl Seligman, a postdoctoral fellow in the College of Natural Science’s Department of Physics and Astronomy, spearheaded the study that identified seven new dark comets. This discovery doubles the known population of these objects and categorizes them into two distinct types based on their orbital characteristics.

Seligman emphasized the importance of studying small celestial bodies like asteroids and comets to understand material transport across the solar system. He stated, "Dark comets are a new class of near-Earth objects that may contain water, so they’re a new potential source for delivering materials to Earth which were necessary for the development of life."

The research, published in the Proceedings of the National Academy of Sciences, distinguishes between outer dark comets and inner dark comets. Outer dark comets are large with eccentric orbits akin to Jupiter-family comets and likely originate from the outer solar system. Inner dark comets are smaller with nearly circular orbits within the inner solar system, potentially originating from the asteroid belt.

Davide Farnocchia from NASA's Jet Propulsion Laboratory noted, "The interesting thing about these objects is that they look like asteroids, but their motion resembles that of comets." This challenges traditional classifications.

The concept of dark comets emerged when scientists observed unusual movements in asteroid 2003 RM in 2003 and later with interstellar object 'Oumuamua in 2017. These observations suggested an alternative classification due to characteristics not typical of either asteroids or traditional comets.

In 2023, both Farnocchia and Seligman identified seven objects sharing traits with 'Oumuamua using facilities like the European Southern Observatory's Very Large Telescope. Their findings classified these as a new category: dark comets.

Louise Edwards from NSF highlighted this discovery as evidence supporting innovative postdoctoral research. Seligman's work broadens knowledge about near-Earth objects and opens future research avenues regarding their origins and possible contributions to Earth's formation.

Seligman expressed optimism about future discoveries: “Expanding our knowledge on dark comets helps to contextualize ‘Oumuamua... With the 14 dark comets we now know about... there are windows of opportunity in the next few years for us to gather more data.”

His work is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship with additional funding from Charles Simonyi's gift to NSF's Division of Astronomical Sciences.