The sun could be much bigger than we think, Nasa scientists have claimed.

Researchers studying the shadows cast during a solar eclipse believe they have found evidence suggesting our star has a far larger radius than previously believed.

And this year's historic solar eclipse, which falls on August 21, could prove that we've been underestimating the size of the sun for almost 200 years, the researchers said.

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Researchers believe they have found evidence suggesting our star has a far larger radius than previously believed (pictured is a stock image of a solar eclipse)

IS THE SUN BIGGER THAN WE THINK? Researchers studying the shadows cast during a solar eclipse believe they have found evidence suggesting our star has a far larger radius than previously believed. Xavier Jubier, a researcher that creates detailed models of solar and lunar eclipses for Google Maps, said his observations suggest the sun is bigger than we think. As part of his work, he predicts where the shadow created by a solar eclipse will fall on Earth. He noticed that something was wrong with the sun's measurements while he was comparing his previous eclipse predictions with photos taken during historical solar eclipses. Mr Jubier was able to match the location of the photographs to that predicted by his models - but only if he scaled by the sun's radius by a few hundred kilometres. 'For me, something was wrong somewhere, but that's all I could say,' Mr Jubier told Space.com. Advertisement

In 1891, a German astronomer known as Arthur Auwers was the first to estimate the size of the sun.

Based on the star's photosphere, the body of the sun whose wavelengths are visible to the naked eye, he calculated that the sun had a radius of 432,470 miles (696,000km).

This benchmark figure was widely used until 2015, when the International Astronomical Union updated this figure to 432,280 miles (695,700km) based on data from solar-observing satellites.

But now a growing number of scientists have claimed that both of these estimates are too small.

Xavier Jubier, a researcher from Antony in France who creates detailed models of solar and lunar eclipses for Google Maps, said his observations suggest the sun is bigger than we think.

As part of his work, he predicts where the shadow created by a solar eclipse will fall on Earth.

He noticed that something was wrong with the sun's measurements while he was comparing his previous eclipse predictions with photos taken during historical solar eclipses.

Mr Jubier was able to match the location of the photographs to that predicted by his models - but only if he scaled by the sun's radius by a few hundred kilometres.

'For me, something was wrong somewhere, but that's all I could say,' Mr Jubier told Space.com.

And Ernie Wright, a researcher from Nasa's Goddard Space Flight Center in Greenbelt, Maryland, who also creates precise models of solar eclipses, found himself in a similar dilemma to Mr Jubier.

He too found that he could only make his models match reality if he increased the size of the sun in his calculations.

The sun could be much bigger than we think, Nasa scientists have claimed. Pictured is sun with active regions combined to look something like a jack-o-lantern’s face

The researchers hope this year's upcoming eclipse, which will likely be the most-watched solar eclipse in history, will provide a chance for scientists to verify the size of the sun.

A group of scientists plan to study the eclipses' 'contact time', the time when the moon will cover the sun for a given location, to help them figure out the star's size.

Normally, researchers use the radius of the sun to predict the length of contact time during an eclipse - and it is believed that these calculations could be reversed to help scientists predict the size of the sun.

AUGUST 21ST'S HISTORIC SOLAR ECLIPSE The total solar eclipse on Monday, August 21, 2017 will cross the continental United States beginning in Oregon and ending in South Carolina. While a total solar eclipse occurred over the continental US in 1979, the last time one such event spanned the country coast to coast was in 1918. In that event, the the path of totality entered through the southwest corner of Washington and passed over Denver, Colorado, Jackson, Mississippi, and Orlando, Florida before exiting the country at the Atlantic coast of Florida. This year, the path of totality will cross through 14 states, with the path of totality stretching from Lincoln Beach, Oregon, to Charleston, South Carolina. If you're not in the 70-mile-wide path of totality, don't fret; as the eclipse will be partially visible across all of North America, and even in parts of South America, Africa, and Europe, according to NASA. Advertisement

'If we can measure contact times accurately, everything else being the same, the only thing that can change is the solar radius,' Luca Quaglia, a physicist and eclipse researcher from the American Astronomical Society, told Space.com.

'We can actually compute the solar radius that way.'

The team plan to to use 'flash spectrum' photography, which uses a textured grating over a camera to split incoming wavelengths of light.

By doing this, they can easily determine the precise moment contact time is initiated during the eclipse, they said.

And by combining this information with accurate time stamps, they will be able to make an accurate prediction of the size of the sun, they claimed.

'The more observations we have the better even if they are not providing the kind of quality we expected to get,' Mr Jubier said.

'Time will tell what we can make of all this.'