What time will comet A3 be visible this week? Also known as Comet Tsuchinshan-ATLAS (C/2023 A3), it’s currently shining brightly for those in the Northern Hemisphere — but there’s a catch.
It’s brightened and is visible in in the east before sunrise, which means it’s necessary to rise very early before it gets swamped by the light of dawn, and then sunrise. In late-Oct. it will become bright in the west after sunset.
Will you see the comet this week? With some good planning, clear weather and well-timed observing, comet A3 and its bright tail could make an eye-catching sight — particularly because the moon is now waning, darkening the pre-dawn sky.
Why And When Comet A3 Is Visible
Comet A3 is moving to a position in between the Earth and the sun. On Sept. 27, comet A3 reached its perihelion — the closest it gets to the sun — at about 36 million miles (59 million km). Comet A3 will get closest to Earth on Oct. 12, when it will pass about 44 million miles (71 million km) from Earth.
Around those two dates are key times to view the comet — and we’re now halfway through that first observing window.
Here are some sky-charts to help you find comet A3 this week. Note that it’s getting closer to the sun with each passing morning, so will appear slightly lower on the horizon. The earlier this week you try to see it, the easier it will likely be.
Where To See Comet A3: Monday, Sept. 30
Position: east-southeast, 21.6 degrees from the sun in Leo
Time: an hour before sunrise where you are (around 07:00 in the U.S.)
Expected magnitude: +4.5
Comet’s distance from the sun: 59.6 million km
Comet’s distance from Earth: 118.5 million km
This morning, comet A3 will be visible close to the east-southeast an hour before sunrise. It will shine to the lower-right of a 5%-lit waning crescent moon. Regulus, the brightest star in the constellation Leo, will shine above the pair.
It should be visible just above east-southeast about 75 minutes before sunrise and will be best seen in astronomical darkness, which will last until about 60 minutes before sunrise. Timing will be everything!
Where To See Comet A3: Tuesday, Oct. 1
Position: east-southeast, 21 degrees from the sun in Leo
Time: an hour before sunrise where you are (around 07:00 in the U.S.)
Expected magnitude: +4.5
Comet’s distance from the sun: 60.5 million km
Comet’s distance from Earth: 112.3 million km
Here’s a chance for something truly spectacular — a naked-eye comet alongside the a crescent moon that’s as delicate as it can be.
Look due east an hour before sunrise to see the comet on the right and a 1.5%-lit crescent moon on the left. Look about about 75 minutes before sunrise, when the two will be seen in astronomical darkness, which will last until about 60 minutes before sunrise.
Where To See Comet A3: Wednesday, Oct. 2:
Position: east-southeast, 19.5 degrees from the sun in Leo
Time: an hour before sunrise where you are (around 07:00 in the U.S.)
Expected magnitude: +4.5
Comet’s distance from the sun: 61.6 million km
Comet’s distance from Earth: 106.2 million km
This morning, comet A3 will be visible a little closer to the east-southeast an hour before sunrise than previously, and now with no moon in sight.
Once again, the comet should be visible just above east-southeast about 75 minutes before sunrise and will be best seen in astronomical darkness, which will last until about 60 minutes before sunrise.
Where To See Comet A3: Thursday, Oct. 3:
Position: east-southeast, 18.2 degrees from the sun in Leo
Time: an hour before sunrise where you are (around 07:00 in the U.S.)
Expected magnitude: +4.5
Comet’s distance from the sun: 62.9 million km
Comet’s distance from Earth: 100.4 million km
Here’s the last real chance to see comet A3 during this first observing window. It will be visible even closer to the east-southeast and be best seen about 75 minutes before sunrise in astronomical darkness, which will last until about 60 minutes before sunrise.
When To See Comet A3 In October 2024
Around Oct. 4, comet A3 will head into the sun’s glare, and be much harder to see for a few days, before being swallowed-up completely by our star’s light. Here are sky-charts for Oct. 4-6, but note that comet A3 will be almost impossible to see in the gathering light of dawn:
When To See Comet A3 In Mid-October
Comet A3 will re-emerge in twilight around Oct. 12 for those in the Northern Hemisphere. Look to the west immediately after sunset to glimpse it possibly at its brightest and best, though in the evenings after Oct. 12, it will rise higher into the sky.
Check my feed every day this week and next for a daily “comet tracker” with sky-charts and tips for viewing Comet A3.
Wishing you clear skies and wide eyes.
