What's hotter than the surface of the Sun?

Nasa study offers new evidence for 'nanoflares' - tiny, intense solar events that heat the Sun's atmosphere to millions of degrees hotter than its surface

You might be forgiven for thinking that when it comes to hot stuff you can’t beat the surface of the Sun. Scientists, however, have known for years that the surrounding atmosphere of the star is actually much, much hotter – and now they think they know why.

While the visible surface of the Sun, the photosphere, reaches temperatures of 6,000 degrees Kelvin or 5,700 degrees Celsius, the star’s corona - the fluctuating area of plasma that extends millions of kilometres into space - regularly exceeds heights of 2 million Kelvin.

"That's a bit of a puzzle," says Jeff Brosius, a space scientist with the University of Washington. "Things usually get cooler farther away from a hot source. When you're roasting a marshmallow you move it closer to the fire to cook it, not farther away."

New research published by Brosius and his team in the Astrophysical Journal gives credence to the idea that a solar phenomenon known as nanoflares are responsible – extremely intense bursts of heat and energy that act like tiny heating elements in the surrounding plasma.

In order to do so nanoflares are thought to reach temperatures of 10 million Kelvin. Unfortunately this means that the resulting solar event is so short-lived and small that scientists can’t observe them directly - instead, they have to rely on measuring wavelengths of light emitted at those temperatures.

This is exactly what Brosius and his team have done, scanning a particularly active region of the Sun using a relatively rough-and-ready spacecraft known as a sounding rocket. These are launched into Space for 15 minutes at a time, reaching heights of around 200 miles before falling back to Earth.

This type of mission produces just six minutes of observational data, but this proved enough for Brosius and his team. The craft they launched in April last year came back with data described as the nanoflares’ “smoking gun”: a spectral emission corresponding to material heated to 10 million degrees.

For astronomers, confirming the existence of nanoflares is just another step towards solving the complex puzzle of the Sun's solar 'ecosystem', but for Brosius the discovery is a little more tangible.

"This [...] really gives us the strongest evidence yet for the presence of nanoflares," he told ScienceDaily. "The fact that we were able to resolve this emission line so clearly from its neighbors is what makes spectroscopists like me stay awake at night with excitement."

Start your day with The Independent, sign up for daily news emails
ebooks
ebooksA special investigation by Andy McSmith
  • Get to the point
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

SThree: IT Recruitment Consultant

£22500 - £30000 per annum + Commission: SThree: Sthree are looking for experie...

Recruitment Genius: Cleaner / Handyman

£16575 - £18785 per annum: Recruitment Genius: This Dundee based butchers requ...

Recruitment Genius: Confectionery Manager

Negotiable: Recruitment Genius: To effectively manage a team which is responsi...

Recruitment Genius: Workshop Deputy & Production Manager

Negotiable: Recruitment Genius: A rare and exciting role has arisen within thi...

Day In a Page

General Election 2015: The masterminds behind the scenes

The masterminds behind the election

How do you get your party leader to embrace a message and then stick to it? By employing these people
Machine Gun America: The amusement park where teenagers go to shoot a huge range of automatic weapons

Machine Gun America

The amusement park where teenagers go to shoot a huge range of automatic weapons
The ethics of pet food: Why are we are so selective in how we show animals our love?

The ethics of pet food

Why are we are so selective in how we show animals our love?
How Tansy Davies turned 9/11 into her opera 'Between Worlds'

How a composer turned 9/11 into her opera 'Between Worlds'

Tansy Davies makes her operatic debut with a work about the attack on the Twin Towers. Despite the topic, she says it is a life-affirming piece
11 best bedside tables

11 best bedside tables

It could be the first thing you see in the morning, so make it work for you. We find night stands, tables and cabinets to wake up to
Italy vs England player ratings: Did Andros Townsend's goal see him beat Harry Kane and Wayne Rooney to top marks?

Italy vs England player ratings

Did Townsend's goal see him beat Kane and Rooney to top marks?
Danny Higginbotham: An underdog's tale of making the most of it

An underdog's tale of making the most of it

Danny Higginbotham on being let go by Manchester United, annoying Gordon Strachan, utilising his talents to the full at Stoke and plunging into the world of analysis
Audley Harrison's abusers forget the debt he's due, but Errol Christie will always remember what he owes the police

Steve Bunce: Inside Boxing

Audley Harrison's abusers forget the debt he's due, but Errol Christie will always remember what he owes the police
No postcode? No vote

Floating voters

How living on a houseboat meant I didn't officially 'exist'
Louis Theroux's affable Englishman routine begins to wear thin

By Reason of Insanity

Louis Theroux's affable Englishman routine begins to wear thin
Power dressing is back – but no shoulderpads!

Power dressing is back

But banish all thoughts of Eighties shoulderpads
Spanish stone-age cave paintings 'under threat' after being re-opened to the public

Spanish stone-age cave paintings in Altamira 'under threat'

Caves were re-opened to the public
'I was the bookies’ favourite to be first to leave the Cabinet'

Vince Cable interview

'I was the bookies’ favourite to be first to leave the Cabinet'
Election 2015: How many of the Government's coalition agreement promises have been kept?

Promises, promises

But how many coalition agreement pledges have been kept?
The Gaza fisherman who built his own reef - and was shot dead there by an Israeli gunboat

The death of a Gaza fisherman

He built his own reef, and was fatally shot there by an Israeli gunboat