Interstellar object 3I/ATLAS is different from its predecessors, 1I/’Oumuamua, discovered in 2017, and Comet 2I/Borisov in 2019. It’s faster, it’s older, more active, and estimated to be larger. Now, observations from the X-ray telescope XRISM suggest that it is also the first interstellar object with an X-ray signature.Before the conspiracy theorists claim that this is some sort of engine signature or a weapon charging up, let’s stress that it is perfectly normal for comets to emit X-rays. This emission comes from specific interactions between the plasma released at high speed by the Sun and the coma, the atmosphere of the comet. This is gas and dust released as the comet gets near the Sun.
The European Space Agency’s X-ray space observatory XMM-Newton observed interstellar comet 3I/ATLAS on 3 December for around 20 hours. During that time, the comet was about 282–285 million km from the spacecraft.XMM-Newton observed the comet with its European Photon Imaging Camera (EPIC)-pn camera, its most sensitive X-ray camera.This image shows the comet glowing in low-energy X-rays: blue marks empty space with very few X-rays, while red highlights the comet’s X-ray glow. Astronomers expected to see this glow because when gas molecules streaming from the comet collide with the solar wind, they produce X-rays.These X-rays can come from the interaction of the solar wind with gases like water vapour, carbon dioxide, or carbon monoxide – which telescopes such as the NASA/ESA/CSA James Webb Space Telescope and NASA’s SPHEREx have already detected. But they are uniquely sensitive to gases like hydrogen (H₂) and nitrogen (N₂). These are almost invisible to optical and ultraviolet instruments, such as the cameras on the NASA/ESA Hubble Space Telescope or ESA’s JUICE.This makes X-ray observations a powerful tool. They allow scientists to detect and study gases that other instruments can’t easily spot.
On December 19, 2025, 3I/ATLAS reached its closest distance to Earth, at 1.7 AU (167 million miles). To obtain optimum sensitivity, we observed 3I/ATLAS with the largest steerable single-dish radio telescope in the world, the 100-meter Green Bank Telescope, less than 24 hours before the closest approach of 3I/ATLAS, on December 18, 2025. We used four receivers (L, S, C, and X) spanning frequencies of 1 - 12 GHz. At closest approach, the GBT is sensitive to transmitters with an EIRP of approximately 0.1 W, more sensitive than all previous observations. No artificial radio emission localized to 3I/ATLAS was detected.In summary, 3I/ATLAS continues to behave as expected from natural astrophysical processes. That said, it remains an extremely interesting target for observation given the overall rarity of interstellar objects. We will continue to observe 3I/ATLAS as a part of a broader strategy to thoroughly investigate all interstellar objects, consistent with our goal of conducting humanity’s most sensitive, intensive and comprehensive search for technosignatures.
After so many observations from so many different positions, do we have a 3d model of the "tails system" of this body? In other words: is it confirmed if the anti-tail is real? or is it perspective-induced? And how long are they?
Quote from: spacexplorer on 01/09/2026 07:11 amAfter so many observations from so many different positions, do we have a 3d model of the "tails system" of this body? In other words: is it confirmed if the anti-tail is real? or is it perspective-induced? And how long are they?3I/ATLAS is old news now. Everyone dumped it and went on to the Jupiter Conjunction. Sorry, continue one.
Very soon a telescope will detect another interstellar object. And very soon, some people will speculate that it is an alien spaceship.My totally unoriginal predictions for this thread.
