During the month of July, astronomers informed the world of a comet that recently passed planet Earth. The comet was first discovered in 2017, and at the time was over 1.5 billion miles from Earth; however, the comet has just passed by Earth on July 14th, and will likely remain visible for the rest of August. Although this comet is approximately estimated to have twice the size of Mount Everest, a shocking 11 miles, it has not been the largest comet discovered; C/2014 UN271 holds the title, with an average diameter of 85 miles, and has also been the farthest comet to be detected. Yet, the recent passing of C/2017 K2 PanSTARRS will provide astronomers and scientists with new observations and data on this unique comet.
Aside from other comets that pass Earth here and there, C/2017 K2 is considered an active comet, where its tail and coma are so luminous that the comet itself is visible from the surface of the Earth. However, scientists have been puzzled by this comet, such as how it has been capable of remaining “active” for such a large stretch of time, with much proximity to the Sun. In past research, the Sun has been the cause of any comet being so bright and detectable due to the powerful rays. The Sun helps make comets more visible by melting the ice with its heat, causing its coma to flare up as it changes into a gas state, and becomes larger and larger. However, C/2017 K2 is too far enough away from the Sun where this process would normally occur, which begs the question of why it is still visible from Earth. Astronomers and scientists have many proposals for this mystery–like different chemicals and gasses mixing with the ice to create such a luminous state–yet it is still unaware of how this is possible.
The Hubble Space Telescope was also able to capture an image of C/2017 K2 in June of 2017 when it had still been near Saturn. The pictures showed that somehow, sunlight was still capable of reaching the comet, making it the farthest ever “active” comet found within the solar system. The photographs also perplex scientists about the large formation of the comet’s coma from such a distance. Astronomers have hypothesized that the large flaring of the coma has been caused by a chemical reaction with the Sun and the chemicals that lie on the comet itself, including; oxygen, carbon dioxide, nitrogen, and carbon monoxide. Further evidence was pulled from previous comets that were closer to the sun, and they all had similar effects. Furthermore, the dust particles that would usually be swept behind the coma by the Sun’s heat, creating the infamous tail of the comet, were not featured in the pictures taken. Astronomers believe that the particles being lifted off of the coma are too massive for the Sun’s radiation and pressure to sweep them back. However, the distance of this comet from the Sun continues to fascinate and confuse research teams about how this is possible.