The comet NEOWISE has captured the interest of all novice and professional astronomers alike. Having been discovered March 27, 2020, by NASA’s Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE), it made its closest pass to the sun on July 3rd, before circling back towards our solar system. The reason it is such an exceptional sight to see is for a variety of reasons. The first being its clear visibility within the sky, the second is its incredibly long orbit, and the third and most exceptional is the likelihood of it having a sulfur tail. Here is an overview of the various factors that have caused NEOWISE to be an overnight sensation.
Comets are small celestial bodies encased in ice. They are formed by particles of dust coated in water ice and various other molecules. When passing by a star such as the Sun, the ice melts and releases gases, a process called outgassing. This is what creates the tail we see behind NEOWISE and all other comets. It is also what causes the comet to be visible to the naked eye. NEOWISE, in this case, is clearly visible across the world for a variety of reasons. Thanks to its diameter of 3 miles, relative distance from Earth, and exceptionally long tail, we have one of the best views of a comet in the last several centuries.
Our Earth has an orbit of 365 days while Neptune has an orbit of 165 years. Just like the varying orbits of our solar system, comets can have an orbit of anywhere between 200 years to 1,000 years, at most. NEOWISE is unusual, as it is one of the few comets that have an orbit of over 5,000 years, though it is not known if it is bound to the Sun or to another force of gravity. NEOWISE has an orbit of 6,800 years, but in time, it may bind itself to another star with stronger gravity than our own and not revisit our solar system. Since we will never see this comet again in the course of our lives, nor even in the next 5,000 years, it is understandable that everyone is scrambling to get a look at the sensational comet.
Lastly, and perhaps the most exciting discovery of NEOWISE, is the possibility of the sodium tail of the comet. Most commonly, comets have two tails that are visible within the sky, one made of ions and one made of space dust. NEOWISE had been believed to be similar to these past comets as it had a faint blue tail formed of ions and a larger, brighter dust tail. It was discovered on July 8th that NEOWISE may have an atomic sodium tail. Researchers at the Planetary Science Institute were able to record yellow light wavelengths emitting from the comet that indicate traces of atomic sodium in the larger dust tail of the comet. Being able to create an image from the emissions is relatively rare since the glare of the Sun makes it a challenge for researchers. NEOWISE continues to exceed our expectations, with the various discoveries being made about it.
NEOWISE has already brought forth new information and discoveries in the short time it has been visible in the sky. Who knows what we might find over the course of the next few weeks, and even if we don’t make any groundbreaking discoveries, being able to experience something as spectacular as viewing a comet that won’t reach Earth for the next 6.8 millennium is an experience that none shall take for granted nor forget through their entire life.