Study Reveals Secrets Of Comet 46P/Wirtanen

In 2018, comet 46P/Wirtanen made its closest approach to Earth on December 16, 2018. Due to the proximity to the holidays, the comet was nicknamed the "Christmas Comet" and exuded an interesting green glow. It passed 7.1 million miles from Earth which is the closest pass it had made to the Earth in centuries.

While 46P/Wirtanen has been gone for years, study into the comet has continued. Recently, a study was published and found it was releasing an unusually high amount of alcohol as it passed by our planet. John Hopkins scientist Neil Dello Russo said that 46P/Wirtanen has one of the highest alcohol-to-aldehyde ratios measured in any comet so far. According to Russo, that ratio tells scientists information about how carbon, oxygen, and hydrogen molecules were distributed in the early solar system where the comet formed.

Researchers at the Keck Observatory gathered data on the comet that revealed another odd characteristic. Typically as a comet orbits closer to the sun, frozen particles in the nucleus heat up and boil off, going from solid ice to gas, bypassing the liquid phase completely in a process called outgassing. Outgassing is responsible for the coma, which is the cloud of gas and dust that glows around the comet's nucleus.

As a comet nears the sun, solar radiation pushes some of the coma away from the comet creating the iconic tail they are known for. The interesting discovery about 46P/Wirtanen is that data from Keck shows another process in addition to solar radiation is heating the comet. Researchers found that measured temperatures for water gas in the coma did not decrease significantly with distance from the nucleus, implying a heating mechanism.

One potential explanation is a chemical reaction with sunlight ionizing some atoms or molecules in the coma close to the nucleus, which releases high-velocity electrons. When those electrons collide with other molecules, they transfer some kinetic energy and heat the water gas in the coma. Another potential reason is that solid chunks of ice may be coming off the comet. That process has been seen in other comets in the past, and those ice chunks can sublimate as they tumbled away from the nucleus and release energy further out in the coma. Scientists continue to study data gathered about the comet to try and reveal more of the comet's secrets.