Thought you knew the solar system? Think again

We are in the middle of an astronomical revolution. As the telescopes used to discover the sky get stronger, astronomers have been able to study the biggest and brightest objects in the furthest reaches of space – in “alien” solar systems, and among our own.

And recent revelations paint a very different picture from the eight (or nine, depending on your views on Pluto) planet solar system most of us learned about at school.

What we find is that the further out from the sun we are, the weirder stuff gets Astronomer Alan Fitzsimmons, Queen’s University, Belfast

The first major discovery to shake up our very own inter-planetary system was the discovery of the Kuiper Belt, back in 1992. Before then, the most significant discovery was the planet Pluto, in 1930.

The Kuiper Belt lies just beyond the orbit of the planet Neptune, and was initially thought to contain one object, but astronomers have since discovered thousands of minor planetary bodies. It was the discovery of this icy belt, and the many more, smaller planets within it, that led to Pluto being demoted to “dwarf” status.

Many moons

As observation continued, it emerged that some of these objects were very large: this was the second most significant discovery to impact our solar system, says Alan Fitzsimmons, astronomer at the Astrophysics Research Centre at Queen’s University, Belfast.

“Some of these objects are very interesting in their own right,” he told Channel 4 News. “For example, many have their own moons.”

But past the icy Kuiper belt, past the “trans-Neptunian” region and beyond, the more murky our knowledge becomes. And as Professor Fitzsimmons puts it: “Generally, what we find is that the further out from the sun we are, the weirder stuff gets.”

Only one object, Sedna, was known to exist here in the farthest regions – in the area known as the “inner Oort cloud”.

Read more: Making waves, and other big scientific discoveries

Super earth?

And this is where the new dwarf planet, VP 113, is thought to lie. At 450 kilometres wide, and made up of rock and ice, this new planet is the most distant object discovered in our solar system, lying 80 astronomical units from the sun at its closest approach.

Beyond this area, and outside of our own solar system, Nasa’s Kepler telescope has discovered over 1,000 planets much further away – including one that is 1,000 degrees Celsius and rains glass. But kepler is not designed for this kind of operation.

This is why the discovery of VP 113 is a big deal in itself.

But it is its orbit which is making waves across the astronomy community, because it hints at the existence of another large body – either one “super earth” planet, or a mass of smaller objects – that is also orbiting the sun.

Along with the discovery of the Sedna planet a decade ago, these two new planets are a hugely significant discovery.

“There’s a group of objects out there in the distant reaches of solar system, and we don’t understand how we got there yet,” says Professor Fitzsimmons. “This discovery of VP 113 is one of these objects, in that its orbit places it entirely outside the realm of the planets. And yet we believe they must have been put there somehow.”

‘Golden age’

Mark Bailey MBE, director of the Armagh Observatory, agrees that astronomy is in a “golden age”, with new discoveries being made all the time.

But he urges “buckets of salt” when it comes to some of the large predictions that are made.

“I would urge you always to put on your sceptical hats,” he told Channel 4 News. “What’s interesting about astronomy, is that so many discoveries have been unexpected.”