Page last updated at 18:27 GMT, Wednesday, 21 April 2010 19:27 UK

Nasa's Solar Dynamics Observatory returns first images

By Jonathan Amos
Science correspondent, BBC News

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The observatory's images are acquired at a rapid rate

Nasa's Solar Dynamics Observatory has provided an astonishing new vista on our turbulent star.

The first public release of images from the satellite record huge explosions and great looping prominences of gas.

The observatory's super-fine resolution is expected to help scientists get a better understanding of what drives solar activity.

Launched in February on an Atlas rocket from Cape Canaveral, SDO is expected to operate for at least five years.

Researchers hope in this time to go a long way towards their eventual goal of being able to forecast the effects of the Sun's behaviour on Earth.

It's like looking at the details of our star through a microscope
Richard Harrison, Rutherford Appleton Laboratory

Solar activity has a profound influence on our planet. Huge eruptions of charged particles and the emission of intense radiation can disrupt satellite, communication and power systems, and pose a serious health risk to astronauts.

Scientists working on SDO say they are thrilled with the quality of the data received so far.

"When we see these fantastic images, even hard-core solar physicists like myself are struck with awe, literally," said Lika Guhathakurta, the SDO programme scientist at Nasa Headquarters.

Whole Sun view from SDO (Nasa)
SDO sees the Sun's whole disc but can then zoom in to view fine detail

SDO is equipped with three instruments to investigate the physics at work inside, on the surface and in the atmosphere of the Sun.

The probe views the entire solar disc with a resolution 10 times better than the average high-definition television camera. This allows it to pick out features on the surface and in the atmosphere that are as small as 350km across.

The pictures are also acquired at a rapid rate, every few seconds.

In addition, the different wavelengths in which the instruments operate mean scientists can study the Sun's atmosphere layer by layer.

A key quest will be to probe the inner workings of the solar dynamo, the deep network of plasma currents that generates the Sun's tangled and sometimes explosive magnetic field.

It is the dynamo that ultimately lies behind all forms of solar activity, from the solar flares that explode in the Sun's atmosphere to the relatively cool patches, or sunspots, that pock the solar disc and wander across its surface for days or even weeks.

"The SDO images are stunning and the level of detail they reveal will undoubtedly lead to a new branch of research into how the fine-scale solar magnetic fields form and evolve, leading to a much, much better understanding of how solar activity develops," said co-investigator Richard Harrison from the UK's Rutherford Appleton Laboratory (RAL).

"It's like looking at the details of our star through a microscope," he told BBC News.

And Dr Guhathakurta added: "It's thought that [SDO] is going to revolutionise heliophysics much as the Hubble Space Telescope has revolutionised astrophysics and cosmology, which is true. There is however a very key difference. While Hubble is designed to observe almost everything in the cosmos, SDO is designed to study only one thing and that is our very own star. It is tailor-made for the study of Sun stuff."

Diagram of SDO (Nasa)

SDO's three remote-sensing instruments are:

Helioseismic and Magnetic Imager (HMI): will study the motions and magnetic fields at the Sun's surface, or photosphere, to determine what is happening inside the star. It will try to decipher the physics of the solar dynamo - the very source of the Sun's activity. The dynamo regulates all forms of solar activity from the lightning-fast eruptions of solar flares to the slow decadal undulations of the sunspot cycle.

Atmospheric Imaging Assembly (AIA): is a suite of four telescopes that will image the corona, the outer layer of the Sun's atmosphere. The AIA filters cover 10 different wavelength bands, or colours, from the extreme ultraviolet to the visible. It will see details as small as 725km across. These images will be acquired every 10 seconds. Previous observatories have taken pictures at best every few minutes.

Extreme Ultraviolet Variability Experiment (EVE): will measure the Sun's energy output in extreme-ultraviolet (E-UV) wavelengths (this is called irradiance) with unprecedented precision. The Sun is at its most variable in the E-UV. E-UV rays can break apart atoms and molecules in the Earth's upper-atmosphere, creating a layer of ions that can severely disturb radio signals.

The UK has a prominent role in the mission through the Rutherford Appleton Laboratory in Didcot; the e2v company in Chelmsford which supplied CCD camera detectors; ABSL Space Products in Abingdon which provided the battery, the Mullard Space Science Laboratory in London; the University of Warwick; the University of Sheffield; and the University of Central Lancashire (UCLan) in Preston.

UCLan handles the SDO data coming into the UK. With the mission producing some 1.5 tera-bytes per day, it requires a dedicated gateway for scientists to exploit.

Multiwavelength view of solar atmosphere
Multi-wavelength observations slice through the different atmospheric layers

Jonathan.Amos-INTERNET@bbc.co.uk



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