31/Atlas remains a mystery as it draws nearer to our planet, reaching its closest point next week, but the European Space Agency claims to have caught vital new clues with an x-ray camera.
The interstellar object has sparked fears of an alien invasion with its bizarre appearance and behaviour. A Harvard expert has spotted thrusters and others see hints of alien technology in how the comet's tail pointed the wrong way when it shot past the sun.
But we might be inching closer to unmasking 31/Atlas's true nature after the X-ray space observatory XMM-Newton observed it on 3 December for around 20 hours while it was about 282-285 million km from the spacecraft.
The space agency said the XMM-Newton tracked the comet with its European Photon Imaging Camera (EPIC)-pn camera, its most sensitive X-ray camera.
This camera's image shows the comet glowing in low-energy X-rays. Blue marks empty space with very few X-rays, while red shows the comet's X-ray glow. Astronomers expected to see this glow because gas molecules produce the rays when they stream from the comet and collide with the solar wind.
The agency highlighted how x-rays can tell us new details about the interstellar visitor. The rays can come from the interaction of the solar wind with gases like water vapour, carbon dioxide, or carbon monoxide. Telescopes such as the NASA/ESA/CSA James Webb Space Telescope and NASA's SPHEREx have already detected these.
But x-ray cameras are uniquely sensitive to gases like hydrogen (H₂) and nitrogen (N₂), which are almost invisible to optical and ultraviolet instruments such as the cameras on the NASA/ESA Hubble Space Telescope or ESA's JUICE.
X-ray observations are a powerful tool for scientists to detect and study gases that other instruments can't easily spot, said the agency
Lots of boffins believe the first detected interstellar object, 1I/'Oumuamua, found in 2017, may have been made of exotic ice like nitrogen or hydrogen. But it's too far away now for us to check. 3I/ATLAS presents a fresh chance to study an interstellar object. X-ray light can help us figure out what it's made of.
A wave of large-scale planetary defence drills has been carried out across the world in recent weeks, prompting speculation that governments are preparing for the unpredictable behaviour of 3I/ATLAS.
Astrophysicist Avi Loeb suggests that the comet's sunward anti-tail could be a swarm of compact objects travelling alongside 3I/ATLAS rather than a gas plume. A swarm would shift planetary defence from tracking a single body to monitoring multiple independent objects.
Defence planners view this as a dramatically more complex scenario requiring expanded sensor networks, additional satellites and faster response capability.