Comet NEOWISE is one of the brightest comets observed by earthlings since Hale-Bopp in 1997. Under dark skies away from city lights, it can even be seen clearly with the naked eye (a rare occurrence). Keep reading to learn about the comet’s orbit, distance from Earth, size, composition, and why it has two tails. Also get crucial info about how you can see Comet NEOWISE for yourself in July of 2020!
What is Comet NEOWISE?
Comet C/2020 F3 NEOWISE was discovered on March 27, 2020 by the NEOWISE (Near Earth Object Wide-field Infrared Survey Explorer) space telescope. It is one of hundreds of objects found by the asteroid-hunting NEOWISE survey, which uses infrared to detect and characterize asteroids and comets. To get a sense of the distribution of near-earth objects being tracked by NASA in the inner solar system, check out the video below. Earth is teal, near-earth objects are green, comets are yellow, and all other asteroids are grey:
How to see Comet NEOWISE in July of 2020?
Comet NEOWISE has a near-parabolic orbit, and is currently swinging around the sun. It passed closest to the Sun on July 3, 2020 and will reach it’s closest approach to Earth on July 23, 2020. Due to its orbital trajectory relative to Earth, the position of the comet in our night sky is continually changing as it travels along. Prior to July 13th the best viewing hours were during the early morning. At the time of writing this post, evening hours now provide better opportunities for those in northern latitudes. The optimal evening window is July 14-19, as this is when the comet will be highest in the sky above the horizon (minimizing unfavorable effects from clouds, haze, and city lights). Around an hour after sunset, look above the north or northwest horizon approximately below the Big Dipper constellation (for specifics depending on your location, try using Stellarium Web). You should maximize your distance from city lights and bring a good pair of binoculars or a telescope to enhance your viewing experience. Check out our recommendations for quality beginner telescopes in 2020!
How far away is it? When will it be visible again?
At its closest point to Earth, Comet NEOWISE will be 103 million km (64 million miles) away from us. This is 0.69 Astronomical Units (AU) or around 2/3 of the distance from the Earth to the Sun. The semi-major axis of its outbound orbit is 360 AU; for comparison, the semi-major axis of Pluto’s orbit is something like 49 AU. This means that in a few thousand years, Comet NEOWISE will reach its aphelion (the point furthest from the Sun) far beyond the orbit of Pluto. The comet has an orbital period of 6800 years, so we’ll have to wait a long time to see it pass by Earth again!
How big is Comet NEOWISE? What is it made of?
According to Joseph Masiero of NASA’s Jet Propulsion Laboratory, scientists have determined from infrared and visible-light signatures that the comet is about 5 km (3 miles) across, and has a nucleus covered with sooty, dark particles. Similar to other comets in our solar system, Comet NEOWISE is a ‘dirty snowball’ made up of dust, rocks, and ice left over from the birth of our solar system 4.6 billion years ago. As the comet approaches the Sun, it emits a heat signature as it warms up, thus becoming detectable by NEOWISE infrared channels. You may notice in images of the comet that it appears to have two tails. One tail appears broad, curved, and fuzzy, while the other is straight, narrow, and sharper. The broader of the two is a dust tail, made up of heated dust particles streaming off the comet as it travels forward. The narrower tail is the plasma tail, made up of ionized gases from the comet being pushed away from the Sun by the solar wind. These gas molecules are heated and ionized when radiation from the Sun strips them of electrons, and thus glow with their own light – often emitting a pale blueish color in the visible spectrum.
Be sure to find a dark sky near you this month, bring a telescope if possible, and take in the wonder of the cosmos. Comet NEOWISE won’t approach us again for another 6800 years… now is your only chance to see it!