ESA Athena to study the hot and energetic universe

Artist's impression of an active galaxy. 

Credit: ESA/AOES Medialab

ESA has selected the Athena advanced telescope for high-energy astrophysics as its second 'Large-class' science mission.

The observatory will study the hot and energetic Universe and takes the 'L2' slot in ESA's Cosmic Vision 2015–25 plan, with a launch foreseen in 2028.

By combining a large X-ray telescope with state-of-the-art scientific instruments, Athena will address key questions in astrophysics, including: how and why does ordinary matter assemble into the galaxies and galactic clusters that we see today? How do black holes grow and influence their surroundings?

Scientists believe that black holes lurk at the centre of almost all galaxies and that they play a fundamental role in their formation and evolution.

To investigate this connection, Athena will observe X-ray emission from very hot material just before it is swallowed by a black hole, measuring distortions due to gravitational light-bending and time-delay effects in this extreme environment. Athena will also be able to determine the spin of the black hole itself.

Athena's powerful instruments will also allow unprecedented studies of a wide range of astronomical phenomena.

These include distant gamma-ray bursts, the hot gas found in the space around clusters of galaxies, the magnetic interplay between exoplanets and their parent stars, Jupiter's auroras and comets in our own Solar System.

"Athena will be a state-of-the-art observatory that will provide a significant leap forward in scientific capabilities compared with previous X-ray missions, and will address fundamental open questions in astrophysics," says Alvaro Giménez, ESA's Director of Science and Robotic Exploration.

"Its selection ensures that Europe's success in the field of X-ray astronomy is maintained far beyond the lifetime of our flagship observatory XMM-Newton."

The selection process for L2 began in March 2013, when ESA issued a call to the European science community to suggest the scientific themes to be pursued by the Cosmic Vision programme's second and third Large missions.

In November 2013, the theme of "the hot and energetic Universe" was selected for L2 for a launch in 2028, with "the gravitational Universe" selected for L3 and a planned launch in 2034.

Now officially selected for L2, Athena now moves into a study phase. Once the mission design and costing have been completed, it will eventually be proposed for 'adoption' in around 2019, before the start of construction.

After launch, Athena will travel to its operational orbit around the gravitationally semi-stable location in space some 1.5 million kilometres beyond Earth as seen from the Sun, a position coincidentally known as L2. ESA's Herschel, Planck and Gaia missions have also used L2 orbits.

Energetic Space Tornadoes hold the key to Solar Mystery

A team of European scientists has discovered super-hot and super-fast tornados on the Sun, which may help answer a number of outstanding questions in the realm of physics.

Writing in the journal Nature, they report that these `magnetic tornadoes reach speeds of up to 10,000 kilometres per hour, completely dwarfing anything found on Earth.

For images and videos visit www.solartornado.info 

In fact the fastest recorded tornado on Earth only reached speeds of approximately 486 km per hour, and was by no means an example of a common occurrence.

These magnetic tornadoes on the Sun, created by rotating magnetic field structures which force plasma to move in spirals, are not only common but may hold the answer to a long-standing physics conundrum: why the surface of the Sun is cooler than its outermost atmospheric layer.

Think of any fire and it is common knowledge (and sense) that the closer one gets to the fire, the hotter it gets.

The Sun however doesn't quite follow this logic. Its central core is an amazing 15,000,000 degrees Celsius and its surface cools to 5,500 degrees Celsius - following the logic that the further away, the cooler it gets.

The Sun cools to a mere 4,300 degrees Celsius to where a layer of the Sun's atmosphere, the photosphere, meets the chromosphere. In the chromosphere, however, things become topsy-turvy.

When the chromosphere begins to merge with the Sun's outermost atmospheric layer, the corona, the temperature rises to 100,000 degrees Celsius and continues to increase to a scorching 2,000,000 degrees Celsius in the part of the corona that is farthest from the Sun.

This, almost accordion-like sequence of heat, has puzzled many scientists. A puzzle which this recent discovery of magnetic tornadoes may have solved.

Professor Robertus Erdélyi, head of the Solar Physics and Space Plasma Research Centre (SP2RC) of the University of Sheffield's School of Mathematics and Statistics explains: 'One of the major problems in modern astrophysics is why the atmosphere of a star, like our own Sun, is considerably hotter than its surface?

Imagine, that you climb a mountain, e.g. a munro in the Scottish highlands, and it becomes hotter as you go higher and higher.

'It is understood that the energy originates from below the Sun's surface, but how this massive amount of energy travels up to the solar atmosphere surrounding it is a mystery.'

'We believe we have found evidence in the form of rotating magnetic structures - solar tornadoes - that channel the necessary energy in the form of magnetic waves to heat the magnetised solar plasma.'

'We report here the discovery of ubiquitous magnetic solar tornadoes and their signature in the hottest areas of the Sun's atmosphere where the temperature is a few millions of degree kelvin, about thousands of kilometres from the Sun's surface. This is a major step in the field.'

It is estimated that there are as many as 11,000 of these magnetic tornadoes above the Sun's surface at any time, and each one more than 1,600 km wide. Despite their number and size, they have never been seen until now.

Read the full article at EU CORDIS

Read more info on Space Tornadoes here at Institute of Theoretical Physics, University Oslo