As the mysterious interstellar visitor 3I/ATLAS screams across the solar system, astronomers are racing to get a closer look.
The object, widely believed to be a comet, is expected to make its closest approach to Earth in December and to Jupiter in March next year. Despite numerous direct observations from ground-based and space-based telescopes, many questions remain about the object: What is it actually made of? How big is it? How did it get here?
Last month, the European Space Agency used five scientific instruments on board the Jupiter Ice Satellite Explorer (JUICE) to better understand its composition and behavior. JUICE completed a flyby of Venus in August, accelerating its decade-long journey to Jupiter’s icy moons.
While ESA scientists awaited the data, the spacecraft’s navigation camera captured preliminary images of the extremely rare visitor on November 2. Just two days before the probe made its closest approach to 3I/ATLAS, a distance of just 41 million miles, the object reached perihelion, the point closest to the sun, three days later. A statement said scientists were “surprised” to find that it was “surrounded by signs of activity” as it was heated by the sun.
“While data from science instruments will not arrive on Earth until February 2026, our JUICE team cannot wait that long,” ESA wrote.
New images from ESA’s Jupiter Ice Satellite Explorer show signs of activity on 3I/ATLAS.
The Navigation Camera isn’t technically designed to capture high-resolution pictures of the universe; as its name suggests, it’s intended to help JUICE navigate Jupiter’s icy moons in 2031. But even after downloading only a quarter of the data from a single image, the team could clearly observe 3I/ATLAS’s coma, the glowing halo of gas and dust surrounding its core.
According to the European Space Agency, the image also shows “hints of two tails”: a “plasma tail” made of electrically charged gas, and a harder-to-spot “dust tail,” which in the case of a solar system comet would consist of tiny specks the size of smoke particles. The former tends to move away from the Sun, while the latter curves into the path of the comet.
In October, as 3I/ATLAS approached its perihelion, the point closest to the Sun, astronomers observed a more pronounced front-tail growth. This is largely expected for a natural comet, as it is exposed to large amounts of solar radiation, causing the ice to sublime and leave a trail behind.
In the case of 3I/ATLAS, this is an extremely rare opportunity to study interstellar space, as it is the third object from a different star system discovered to date to pass through our solar system.
Fortunately, with the help of existing spacecraft, we will soon be able to better understand its nature. For example, the five instruments accompanying JUICE will include high-resolution multispectral and hyperspectral images, ultraviolet and submillimeter wave data, and particle spectrometer readings.
But scientists will have to be patient because the data is expected to arrive by the end of February, and the European Space Agency said JUICE “uses its main high-gain antenna as a heat shield to protect it from the sun, leaving its smaller medium-gain antenna to send data back to Earth at a much lower rate,” causing the delay.
More information about 3I/ATLAS: 3I/ATLAS Ice volcano appears to be erupting