What we know about the huge comet Nasa has spotted hurtling towards Earth

(Nasa)

Nasa has spotted a comet with an icy nucleus bigger than any other ever seen.

The object is hurtling towards our home further inside of the solar system – though will never get close enough to Earth to put us in danger.

Nonetheless, the comet is an important look at the early solar system, and the mysterious Oort Cloud that is thought to sit at its very edge today.

The ancient comet is in many ways a relic of a long-ago past – and a messenger from a distant part of the universe that we still know very little about.

Here’s everything we know about the object, officially known as Comet C/2014 UN271 (Bernardinelli-Bernstein).

How did we find it?

The comet has been known about for years: the 2014 in its name refers to the year it was detected in images. Back then, scientists were able to make some deductions about it: its trajectory seemed to suggest it had come from the Oort Cloud, and that it was a comet rather than an asteroid.

But the latest findings came from observations in 2022, when scientists used the Hubble Space Telescope to get more pictures of the object. Those offered enough for researchers to start to be able to discern the size of its nucleus.

That was not straightforward: to do so, scientists had to differentiate the nucleus at the core from the large dusty coma that envelops it. To do so, they had to create computer models and compare them with the images, using that comparison to estimate the size.

They found that it was very big indeed. The nucleus could be 85 miles across – making it the biggest one ever observed.

Are we in danger?

No. The object is coming in our direction, towards the inner solar system – but not near us.

The closest it will come is about a billion miles from the Sun, which is outside the orbit of Saturn.

But its journey in towards us is interesting for a host of reasons: it is a visitor from further out in the solar system, and as it comes closer we will be able to observe it.

What can we learn?

Comets are some of the oldest objects in the solar system. Objects like the newly discovered large one come from the Oort Cloud right at its edges: a floating spray of material that is so far from us that its edge could start 5,000 times as far away from the Sun as we are, and so mysterious and difficult to see that it remains theoretical for now.

When comets like this one come so close, they offer an opportunity to observe a relic from that cloud. Scientists can examine them to learn more about that cloud, representing an opportunity to study it without being able to see it.

The comet’s size is useful to understand the mass of the Oort Cloud in general, for instance. And researchers are able to examine its chemical makeup, to better imagine how that Oort Cloud might be constituted.