Gigantic 'alien' comet spotted heading straight for the sun

Scientists have spotted an enormous, 'alien' iceball streaking straight towards the sun. 

The 3.7 mile-wide (6 kilometers) comet, called 96P/Machholz 1, is thought to have come from somewhere outside our solar system, and is being monitored by the NASA-European Space Agency (ESA) Solar and Heliospheric Observatory (SOHO) spacecraft as it zips toward our star inside the orbit of Mercury, leaving an icy trail in its wake. 

Comet tails are primarily composed of gas, which trickles behind the frozen clumps of ice and gas as they are heated by the sun's radiation. In 2008, an analysis of the material shed by 150 comets found that 96P/Machholz 1 contained less than 1.5% of the expected levels of the chemical cyanogen, while also being low in carbon — leading astronomers to conclude that it could be an interloper from another solar system. Now, its plunge towards the sun might reveal even more of its secrets. 

Related: Stunning images capture the moment a green comet's tail is blasted away by the sun

Machholz 1 as imaged by NASA's Galaxy Evolution Explorer (GALEX) spacecraft. (Image credit: NASA Image Collection/Alamy Stock Photo)

"96P is a very atypical comet, both in composition and in behavior, so we never know exactly what we might see," Karl Battams, an astrophysicist at the Naval Research Lab in Washington DC, told "Hopefully we can get some beautiful science out of this and share [it] with everyone as soon as we can."

David Machholz first spotted the eponymous comet in 1986 using a homemade cardboard telescope. Most comets that fall towards the sun tend to be smaller than 32 feet (10 meters) wide, and consequently get burned up as they approach our star. 

But the gigantic size of Machholz 1 (it is more than two-thirds the height of Mount Everest) appears to protect it from complete evaporation, and the SOHO has spotted the comet making five close passes around the sun since its discovery. The icy interloper's closest approach to the sun came on Tuesday (Jan. 31) when it was three times closer to our star than Mercury.

The comet may have found itself on its strange orbit after being ejected from its original solar system by the gravity of a giant planet. Then, after a considerable amount of time wandering the cosmos, an accidental rendezvous with Jupiter could have bent its trajectory to ensnare it around our sun. Other theories also suggest that the comet might not be alien, but may have formed in poorly-understood regions of the solar system or had its cyanogen blasted off by repeat journeys around the sun.

SOHO has spotted more than 3,000 comets since its December 1995 launch, although the spacecraft’s primary mission is to observe the sun for violent eruptions called coronal mass ejections, or solar flares that can cause geomagnetic storms on Earth. The most powerful of these storms can disrupt our planet's magnetic field enough to send satellites tumbling to Earth, and scientists have warned that extreme geomagnetic storms could even cripple the internet.

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Ben Turner
Live Science Staff Writer

Ben Turner is a U.K. based staff writer at Live Science. He covers physics and astronomy, among other topics like weird animals and climate change. He graduated from University College London with a degree in particle physics before training as a journalist. When he's not writing, Ben enjoys reading literature, playing the guitar and embarrassing himself with chess.