Interstellar Comet 3I/ATLAS Is Back From Behind The Sun – Still Not An Alien Spacecraft, Though

Our interstellar visitor is visible again after reaching its closest approach to the Sun yesterday. The PUNCH mission, a group of small satellites studying the Sun, spotted comet 3I/ATLAS as it came out of the Sun’s glare. The interstellar comet, the third known object formed in another star system to be tracked through our Solar System, was spotted beyond the limb of the Sun after its highly anticipated solar conjunction, the moment where it was on the opposite side of the Sun from our point of view.

The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.

For serious astronomers, these last few weeks have been exciting. The interstellar comet is a lot more active than the previous two interstellar objects, 1I/’Oumuamua, discovered in 2017, and Comet 2I/Borisov in 2019. It might also be a lot older than them, maybe twice as old as the Solar System.

ⓘ IFLScience is not responsible for content shared from external sites.

The solar conjunction was just days before the perihelion, the closest approach of the comet to the Sun, which happened yesterday. That meant an increase in activity from the comet, with reports of not just its peculiar anti-tail but also the presence of a possible jet.

While the data is still coming in and it will take days before it is analyzed and shared – and it’s unlikely we’ll get anything from NASA due to the continued US government shutdown (30 days so far for anyone counting) – the automatic pipeline of data allows us to check images and progress, so it was a member of the public online who shared the image from PUNCH.

Data is also getting through automatic tracking systems and has confirmed that the comet passed both the conjunction and the perihelion without alteration to its expected trajectory. So, the space object continues to go where it was expected to, which is not really breaking news, but since its discovery in July, the media has run with Prof Avi Loeb's suggestion that comet 3I/ATLAS might be an alien spacecraft (it's not). 

Perihelion was a special moment; according to the spacecraft hypothesis, that was when the comet could reveal itself as being an artificial craft, using the gravity of the Sun to turn to pull the Oberth Maneuver, and come straight towards Earth. Unfortunately for the proponents of this baseless idea, the comet kept on cometing on its projected path.

Having passed the closest point to the Sun, 3I/ATLAS is now on its way out of the Solar System. It is currently within the orbit of Mars, but every day it gets a little bit further away from the Sun.

That doesn’t mean humans are going to stop studying it. On November 2 and then again on November 25, the European Space Agency will use its Jupiter-bound mission JUICE to observe the comet from deep space.

“JUICE will observe 3I/ATLAS between 2 and 25 November. We will be using five instruments: the camera, the near-infrared imaging instrument, the UV spectrometer, the sub-millimetre instrument, and a sensor to image neutral atoms. We are far away (0.5 Astronomical units), therefore, only remote sensing,” Olivier Witasse, ESA Project Scientist, told IFLScience previously. 

However, “Due to the position of JUICE with respect to Earth, the data rate is very low. We expect the data to be downloaded only in February 2026, so we need to be a bit patient.”

Many other observations are expected to take place in the coming months as the comet and Earth get closest to one another. The closest approach will be on December 19, when the comet is 269 million kilometers (167 million miles) away.

Both professional and amateur astronomers will soon be able to see 3I/ATLAS in the pre-dawn hours. From Sunday, it will appear near Venus in the sky.