Comet NeoWise Visible in July

Comet Neowise is bright and now easy to see.  I took this photo by Ft. Steele on Tuesday morning at 1:30am.  To see the comet, I’d recommend to go between midnight when it gets fully dark, until 3:30am when the Northern sky brightens with dawn.  Otherwise the faint streak of the comet is difficult to see against the glowing sky.  Binoculars make it brighter and allow you to see the pale-blue ion tail and pale-yellow dust tail, but it’s clearly visible by eye.

Neowise 2020 Jul 14 from Fort Steele, BC
Comet Neowise July 14, 2020 from Fort Steele BC

The photo shows Comet Neowise, looking North from Ft. Steele on Tuesday around 1:30am.  Lakit Mountain to the bottom right side with constellation Auriga hidden behind it, Capella the bright star there.  It was taken through a 28mm wide-angle lens.  The green glow along the horizon is the Northern Lights, which were slightly active that night.  According to NOAA, on their 9-point Kp scale it was a minor geomagnetic storm level 3.

Comet Neowise, Thurs Jul 16 at 2am from Fort Steele BC.
Comet Neowise, Thurs Jul 16 at 2am from Fort Steele BC.

Here’s the comet two days later, on Thursday morning at 2am.  Looking at the background stars, notice it’s shifted slightly upwards and to the left from the first photo.  Photographed with a more sensitive 28mm f/1.8 lens.  The comet looks a bit brighter, a white nucleus at bottom, with a pale-blue ion-jet going straight up, as well as a wide pale-yellow dust tail curving back.  Again, along the bottom right you can see Lakit Mountain with trees silhouetted in the red glow of the lights of Ft. Steele.

Comet Neowise Jul 16 zoomed in with 210mm Lens.
Comet Neowise Jul 16 zoomed in with 210mm Lens.

To take comet photos you’ll need about a 10 to 20 second exposure with a SLR camera on a tripod.  (A cell phone would be a challenge.)  This magnified photo was taken on a motorized equatorial tripod so the stars don’t make streaks as the Earth rotates.

Info about Comet NEOWISE C/2020 F3

Location: It’s currently on the Northern horizon, to the left of the constellation Auriga, in Lynx, and will slowly move higher and to the left through the feet of Ursa Major (beneath the Big Dipper asterism) over the next few weeks. It went around the Sun on July 3, inside the orbit of Mercury at 0.29 AU and it’s now moving out and away.   It will be closest to Earth within 64 million miles (103 million kilometers) on July 23.

The comet’s tail: The tail generally points away from the Sun.  (It doesn’t trace out the orbital path the comet is taking as many people assume, sometimes (after perihelion) the tail can point in the opposite direction that it is going.)  The Coma: is created when the heat of the sun melts the frozen ices and dust of the nucleus, which evaporates and lifts off the surface into a globular fog around the ice and dirt. There are various ices: water ice (H2O), dry ice (CO2), carbon monoxide (CO), methane (CH4) and ammonia (NH3). Carbon monoxide ionizes the easiest.   The Ion Tail: is the thin vertical pale-blue straight line in the photo, which is made up of carbon monoxide gases ionized by the Sun’s intense UV light and is pushed directly away from the Sun by its solar wind, along the Sun’s magnetic field streamlines.  It’s a very hot plasma that glows with a pale-blue light.  Sodium Tail: not visible in the photograph, it has a red separation in the tail caused by high amounts of sodium, which also ionizes easily.   Dust Tail: The broad and fuzzy curved pale-yellow tail in the photo. These dust grains and sublimated ice vapours (like steam) are pushed away from the coma by the Sun’s slight radiation pressure.  The dust tail curves as it is pulled by gravity along the orbit behind the comet, and smaller dust grains get pushed faster by sunlight than the bigger and heavier dust grains. The vapours and dust reflect the bright sunlight.  The comet is losing hundreds of kilograms of material every minute and will get smaller as weeks go by.  It should remain visible for a few weeks.

Why the name NEOWISE C/2020 F3?  The comet was discovered by NASA’s orbiting space telescope, the Near-Earth Object Wide-field Infrared Survey Explorer, or NEOWISE, on March 27, 2020.

How big is it?  NASA says: “From its infrared signature, we can tell that it is about 5 kilometers [3 miles] across, and by combining the infrared data with visible-light images, we can tell that the comet’s nucleus is covered with sooty, dark particles left over from its formation near the birth of our solar system 4.6 billion years ago,” said Joseph Masiero, NEOWISE deputy principal investigator at NASA’s Jet Propulsion Laboratory in Southern California.

Location of Comet Neowise plotted until July 26
Location of Comet Neowise plotted until July 26
I made up this skychart in Cartes du Ciel using data from the minor planet center.net.  In the starmap you can see Ursa Major (the Big Dipper) at upper left.  The comet drifts left along the feet of Ursa Major.  It should remain visible along the Northern horizon until Jul 26.

If you get a chance, take 50mm binoculars and try to spot the pale-blue ion tail and the pale-yellow dust tail.  Otherwise it’s clearly visible by eye for a few weeks.

Rick Nowell

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