A once in 80,000 year opportunity

2024 has been quite the year for astronomical bucket list events. A total solar eclipse, aurora borealis visible in southern New Hampshire, not once, but several times, and a comet! C/2023 A3 (Tsuchinshan–ATLAS) was discovered in early 2023 by the Purple Mountain Observatory in China and the Asteroid Terrestrial-impact Last Alert System (ATLAS) in Africa.

Tuesday, October 15, 2024 Comet C/2023 A3 as seen from Merrimack, NH Photo Credit: Danyele Manning (iPhone, 3-second exposure)

What we know about the comet (so far)

The spectrum of the comet when it was 2.66 astronomical units (AU') (1 AU = distance from the Earth to the Sun = 149,598,000 kilometers) from the Sun indicated a high cyanide component indicating that the comet did not contain much carbon. On October 9, the comet brightened to a magnitude of -4.9 the brightest of its time in our night sky. It made its closest approach to earth on October 12th at a distance of 0.47 AU, about half the distance from the earth to the Sun.

Evening of October 16, 2024, Merrimack, NH photo credit: Danyele Manning (iPhone 10-second exposure)

Its the brightest comet in 27 years! Hale - Bopp in 1997 was brighter. I remember going out to look for Hale Bopp as a homework assignment my senior year of high school. This comet also has a rare anti-tail. Normally a comets tail is pointed away from the sun. Comet tails are the result of the solar pressure and wind pushing the stream of dust and gas The tail of Comet C/2023 A3 is pointed toward the Sun!

How to see it?

Comet C/2023 A3 circles the Sun on a steeply inclined retrograde orbit. This view shows the comet's location during its closest approach to Earth on Oct. 12-13, 2024. Sky and Telescope Magazine

It is most visible about 30-45 minutes after sunset in the western sky. look for a tiny bright coma and a tail. If Venus observed the comet is about 2 1/2 fists to the upper right of Venus. The night I observed it, Venus was below my field of view hidden by trees but Antares was up. As the sky gets darker, it becomes easier to see. Moonlight is a bit of an issue with a full harvest super moon but on October 20th, if we have clear skies should have a good naked eye viewing of the coma, ion and dust trails.

Stellarium Web Screenshot of comet in relation to other objects

Visible until October 24, 2024, but getting dimmer every night as it moves away from Earth. Then it won’t be around again for another 80,000 years! You can get some decent shots using an iPhone on night mode with a 10-second exposure. It helps to have a tripod to stabilize the image. If the skies clear on Sunday, the 20th, I plan to pull out the big guns and setup my Nikon with a e30-second exposure to see if I can get more of the tail to reveal itself.

Map dates show the comet's position during evening hours for time zones in the contiguous U.S. states. The comet quickly climbs away from the Sun into a dark sky, while steadily fading. On October 14th it will shine at around +0.5 magnitude; magnitude 2.5 on October 17th; and magnitude 4 on October 22nd. Photo Source: Sky & Telescope

On to the next celestial event......I am still waiting for the nova from T Coronae Borealis. Come on universe!

C/2023 A 3 viewed from Hooper Hill, New Boston, NH. Photo credit Stephanie A. Erickson (iPhone, 10-sec exposure)

Resources for Teaching About Comets

I teach about comets in my Astronomy class, and we bring them up in Integrated Science when talking about characteristics of life and History of Earth and if time I cover them when I cover asteroids and impact craters. With the recent astronomical occurrence, we have been talking about comets in all my classes. Students able to see an object or event in person makes the learning in the classroom so much more potent and real for them. They are far more engaged because they feel it matters to them, since they can see what is happening.

Here are some of my favorites to use when teaching about comets.