BOSTON – It’s not often we get the chance to have one comet with the naked eye. But in a year already filled with so many astronomical treats, it looks like we can add a comet to the list.

Comet C/2023 A3 makes its closest approach to Earth

Comet Tsuchinshan-ATLAS has an orbit of 80,000 years and coincidentally it is now approaching its closest pass to Earth. The comet made its closest approach to our sun on Wednesday, and on Saturday, October 12 at 11:39 a.m. it will be just 43,911,824 miles from Earth (its closest pass). At that point, the comet’s tail will be pointing essentially straight toward Earth. However, in the coming days the tail will turn east, causing dramatic changes in visibility from night to night.

The comet is enormous and long. Its head currently has a diameter of no less than three kilometers. The tail, which is made up mostly of small pieces of ice and dust, is believed to be as long as 30 million kilometers.

C/2023 A3 was brief and barely visible in the early morning sky last week. In the end, most people couldn’t see it because it was very faint and low on the horizon.

What time will the comet be visible tonight?

This time we have a much better chance. The comet will be visible in the western sky for several days from Friday evening after sunset.

On Friday it will be very low on the horizon (about 4 degrees) and probably difficult to see.

Conditions should continue to improve over the coming nights.

Peak visits occur between October 12 and 26. The comet will become the largest visible object in our solar system (after the moon, of course).

On Saturday the comet will be about 6 degrees above the west-southwest horizon about 45 minutes after sunset. If you extend your fist at arm’s length, the comet will be about half a “fist” above the horizon. It will set about 45 minutes later.

Next week, the comet will rise about 3 degrees higher in the sky each successive night and set about 16 minutes later.

On Saturday, October 19, the comet will have risen to about 30 degrees (3 fists) above the horizon and will set almost three and a half hours later. However, it will lose some brightness each night, slowly fading and becoming increasingly difficult to see with the naked eye.

Forecast for viewing the comet

Obviously we need the weather to cooperate so that we can see something on any given evening. In the short term, both Friday and Saturday nights should be mostly clear with some high cirrus clouds possible in some areas late Saturday. On Sunday night we expect some clouds and a few showers. These should clear up during the day on Monday and allow good visibility again.

As always, we’d love to see and share your photos. Send them to [email protected].