Hey Bay Area, Don’t Miss NEOWISE, the Brightest Naked-Eye Comet Since Hale-Bopp!

Picture of comet NEOWISE in the skies over Deer Park, Utah, taken on July 9, 2020.  (NASA)

Have you heard? There’s a comet appearing in the evening and morning skies, bright enough to give even city dwellers a chance to see it.

The comet is named “NEOWISE” after the spacecraft that first spotted it. Discovered on March 27 — not long after the coronavirus lockdowns and stay-at-home orders went into effect — the comet has since grown closer and brighter.

After swinging close to the sun in early July, the comet is now getting closer to Earth, and has grown its familiar tail, a silver lining to grace the twilight and give us something special to look up to as we continue our pandemic hunkering in place.

Where To Look

Comet NEOWISE is visible now in the early evening sky. Though it’s changing position nightly, as comets do, this weekend it may be found just above the northwestern horizon during the last of the evening twilight, close to where the sun set. If you can spot the familiar pattern of stars of the Big Dipper, which hangs vertically with its “cup” on the bottom, comet NEOWISE will be almost directly below, just above the horizon.

Sky map showing the position of comet NEOWISE during the weekend of July 18. The comet will be low near the horizon shortly after sunset, located under the Big Dipper. This photo was taken using the Stellarium at the Chabot Space & Science Center, which filters in a wide range of colors of light. (Ben Burress/Chabot Space & Science Center) (Ben Burress)

Over the next week, comet NEOWISE will climb higher and more westerly night by night. Earlier, the comet put on its best appearance in the morning sky, but now is better to view after sunset.

To see comet NEOWISE you need an unobstructed view of the northwest horizon, with no tall trees, buildings or hills blocking the view. 

Interference from city light pollution will also limit your viewing experience, so if you can find a place to observe away from light-congested areas, you’ll have a better shot at seeing the comet. The darker your sky, the more of the comet and its tail you will be able to see. (And if you choose to travel to a better viewing spot, be sure to maintain proper physical distance from other comet watchers!)

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If urban light pollution is a problem where you live, you may have a difficult time spotting the comet with your eyes, but if you have a pair of binoculars you should be able to see it. 

Virtual Comet Viewing From Chabot Space & Science Center

Chabot Space & Science Center will hold a virtual presentation and Q&A featuring comet NEOWISE at 8 p.m. on Friday, July 17, during the regular “The Sky This Month” livestream. 

Then, during Chabot’s regular Virtual Telescope Viewing events on Saturday, July 18, and a week later on July 25, astronomers will attempt to livestream the comet through the observatory’s 36-inch telescope, Nellie. The events begin at 9:30 p.m., weather permitting. 

Image of comet NEOWISE captured by NASA's STEREO solar observatory spacecraft on June 24, 2020. (William Thompson/NASA/STEREO) (William Thompson/NASA/STEREO)

Comet NEOWISE, Also Known As C/2020 F3

NEOWISE is a “long period” comet that originates in the cold, distant reaches of our solar system called the Oort Cloud. This is a vast, sparsely populated “bubble” of icy objects — comets and primordial “planetesimals” — that surrounds the solar system, extending trillions of miles into space.

Comet NEOWISE’s extremely elongated orbit carried it to within 27 million miles of the sun on July 3, closer than the planet Mercury. The comet will pass closest to Earth on July 23, about 64 million miles away.

On July 5, two days after the comet’s hot encounter with the sun, NASA’s Parker Solar Probe was in the right position to capture an image showing the comet’s twin tails. Comets often have multiple tails, one composed of gas from frozen volatile materials (like water) sublimating under solar heating, and one made of dust particles shed by the outgassing. Pressure from sunlight “blows” the gas tail away from the sun more strongly, producing separate tails.

Now outbound and heading back to the Oort Cloud, the comet’s “slingshot” fling through the sun’s gravitational field has boosted its speed, and it won’t pass by Earth again for almost 7,000 years. 

Diagram showing the perihelion end of comet NEOWISE's orbit around the sun. At closest approach (perihelion), the comet is only 29 million miles from the sun, closer than the planet Mercury. Though the diagram suggests the comet crosses Earth's orbital path, the high inclination of the comet's orbit brings it no closer than 64 million miles from Earth. (NASA) (NASA)

When it reaches its farthest point from the sun over 3 millennia from now, NEOWISE will be about 77 billion miles away — roughly 20 times farther than Pluto.

NASA’s NEOWISE Spacecraft

The comet’s namesake discoverer, NASA’s NEOWISE spacecraft, is on a repurposed mission to hunt for Near Earth Objects (NEOs) — asteroids and comets that may pose an impact risk to Earth. And though this comet is no threat to us, and won’t return for almost 7 millennia, NEOWISE is well suited to the job of detecting comets, because it uses an infrared telescope to survey sources of heat in the cosmos.

Since beginning its new career as NEO-hunter in 2013, NEOWISE has detected around 158,000 asteroids, including about 700 Near Earth Objects. Of these detections, about 34,000 are new discoveries, including 135 NEOs. 

Don’t Miss It

Comets come and go, and there are usually a handful of them lurking somewhere in the sky, if you have a telescope to see them with. 

Rarer are those that come close enough to the sun and Earth for us to see with our unaided eyes. Not since the encounter with comet Hale-Bopp in 1996/1997 has there been a naked-eye comet as bright as NEOWISE. There were a few that showed some promise, only to fizzle out. Comet apparitions are notoriously unpredictable. 

So, if you miss NEOWISE, there will be other comet spectacles in the future — but there’s no telling when.

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