NASA Astronomy Picture of the Day

September 25, 2024

Comet A3 Through an Australian Sunrise

Comet Tsuchinshan-ATLAS is now visible in the early morning sky. Diving into the inner Solar System at an odd angle, this large dirty iceberg will pass its closest to the Sun between the orbits of Mercury and Venus in just two days. Long camera exposures are now capturing C/2023 A3 (Tsuchinshan–ATLAS), sometimes abbreviated as just A3, and its dust tail before and during sunrise. The featured image composite was taken four days ago and captured the comet as it rose above Lake George, NSW, Australia. Vertical bands further left are images of the comet as the rising Sun made the predawn sky increasingly bright and colorful. Just how bright the comet will become over the next month is currently unknown as it involves how much gas and dust the comet's nucleus will expel. Optimistic skywatchers are hoping for a great show where Tsuchinshan–ATLAS creates dust and ion tails visible across Earth's sky and becomes known as the Great Comet of 2024.

https://apod.nasa.gov/apod/astropix.html

"Totally awesome to see a comet from orbit". Astronauts photograph Comet C/2023 A3 from the Space Station

September 25, 2024 at 2:13 am

If you've been waiting all year for Comet C/2023 A3 Tsuchinshan-ATLAS to reach its best, excited at the possibility of it becoming a naked-eye sight in the autumn sky, imagine what it would be like to see the comet from space.

NASA astronauts Matthew Dominick and Don Pettit have been observing and photographing Comet C/2023 A3 from the International Space Station and sharing their views on X (formerly Twitter).

They were able to spot the comet from the Space Station's cupola, which is a module on the ISS used for observing external activities like spacewalks or approaching spacecraft.

Astronauts also use the cupola to watch Earth's continents and oceans drift by as the Space Station orbits our planet, often capturing incredible images of Earth from space.

Comet C/2023 A3 from the Space Station

On 20 September, NASA astronaut Matthew Dominick posted a timelapse video of Comet C/2023 A3 from space, writing "so far Comet Tsuchinshan-ATLAS looks like a fuzzy star to the naked eye looking out the cupola windows."

"But with a 200mm, f2 lens at 1/8s exposure you can really start to see it.

"This comet is going to make for some really cool images as it gets closer to the Sun."

Then on 22 September, NASA astronaut Don Pettit followed Dominick's lead and captured his own images of Comet C/2023 A3.

"It is totally awesome to see a comet from orbit," he wrote on X.

"The perspective of rising through the atmosphere on edge is truly unique from our vantage point.

"The comet tail is still too dim to see with your eyes, but it is heading towards the sun and growing brighter every day."

But how did the astronauts know where to look to find the comet?

Pettit hinted at Dominick's background in engineering and physics, as well as his experience as a Naval test pilot.

"Matthew used math (go figure) and our orbital geometry to figure out where to point our cameras and was the first to get a good photo," Pettit explained on X.

"Using Matthew’s technique, I will photograph every day to see what develops in the tail structure.

"Currently, there appears to be a forward directed 'tail' that I am not certain is real or an artefact from shooting through 4 window panes.

"Time will tell if this structure brightens. Stay tuned."

If you want to observe Comet C/2023 A3 Tsuchinshan-ATLAS for yourself, the next few weeks will be prime period.

It will be visible in Virgo at the start of October, and will look amazing through binoculars or a telescope.

There's even hope that the comet may become naked-eye, but comets are unpredictable, and this is not yet certain.

https://www.skyatnightmagazine.com/news/astronauts-photograph-comet-c-2023-a3-from-space-station