The spring sky

1/05/2015| Galactic whirlpools from Richard Pearson on Vimeo.

Running time: 40m
Made with the help of the BBC

We begin with a tour of the spring sky followed by a look at galaxies.

The Whirlpool galaxy, like others of its kind, contains thousands of millions of stars, and it is impossible to doubt that many of these stars must be attended by inhabited planets. There must be astronomers, too, living in the midst of Messier 51 and using telescopes, and they will be able to see our Galaxy as a faint, blurred spiral of light in their sky.

The night sky this month

1/11/2014| The Autumn Sky from Richard Pearson on Vimeo.

Send your name to Mars with NASA

Add your name to a digital list which will be launched into space on board the Orion test flight in December.

September 2014 | Comets Unveiled

Comets are colourful fuzz-balls in space that have a small rocky nucleus, a shimmering hallo of dust known as the coma, and a long dusty tail stretching thousands of miles in length. They have been seen by sky watchers for centuries, and were once believed to be omens to bad fortune.

Over the last decade, a number of spacecraft have visited comets, and have helped to reveal their secrets, in this month's program we look at some of their findings to help better understand the discoveries that await us from Rosetta over the next year.

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A Spectacular Landscape of Star Formation

This image, captured by the Wide Field Imager at ESO’s La Silla Observatory in Chile, shows two dramatic star formation regions in the southern Milky Way. The first is of these, on the left, is dominated by the star cluster NGC 3603, located 20 000 light-years away, in the Carina–Sagittarius spiral arm of the Milky Way galaxy. The second object, on the right, is a collection of glowing gas clouds known as NGC 3576 that lies only about half as far from Earth.
          NGC 3603 is a very bright star cluster and is famed for having the highest concentration of massive stars that have been discovered in our galaxy so far. At the centre lies a Wolf–Rayet multiple star system, known as HD 97950. Wolf–Rayet stars are at an advanced stage of stellar evolution, and start off with around 20 times the mass of the Sun. But, despite this large mass, Wolf–Rayet stars shed a considerable amount of their matter due to intense stellar winds, which blast the star’s surface material off into space at several million kilometres per hour, a crash diet of cosmic proportions.
          NGC 3603 is in an area of very active star formation. Stars are born in dark and dusty regions of space, largely hidden from view. But as the very young stars gradually start to shine and clear away their surrounding cocoons of material they become visible and create glowing clouds in the surrounding material, known as HII regions. HII regions shine because of the interaction of ultraviolet radiation given off by the brilliant hot young stars with the hydrogen gas clouds. HII regions can measure several hundred light-years in diameter, and the one surrounding NGC 3603 has the distinction of being the most massive in our galaxy.
The cluster was first observed by John Herschel on 14 March 1834 during his three-year expedition to systematically survey the southern skies from near Cape Town. He described it as a remarkable object and thought that it might be a globular star cluster. Future studies showed that it is not an old globular, but a young open cluster, one of the richest known.
          NGC 3576, on the right of the image, also lies in the Carina–Sagittarius spiral arm of the Milky Way. But it is located only about 9000 light-years from Earth — much closer than NGC 3603, but appearing next to it in the sky.
NGC 3576 is notable for two huge curved objects resembling the curled horns of a ram. These odd filaments are the result of stellar winds from the hot, young stars within the central regions of the nebula, which have blown the dust and gas outwards across a hundred light-years. Two dark silhouetted areas known as Bok globules are also visible in this vast complex of nebulae. These black clouds near the top of the nebula also offer potential sites for the future formation of new stars.
          NGC 3576 was also discovered by John Herschel in 1834, making it a particularly productive and visually rewarding year for the English astronomer.

Scientists spot white dwarf reigniting and exploding

It is a blaze of glory rarely seen in the universe.

Astronomers have proved for the first time that dead stars known as white dwarfs can reignite and explode as supernovae.

These incredible images were created to show the stages of the spectacular death,The finding came after the unique signature of gamma rays from the radioactive elements created in one of these explosions was captured for the first time.

Astronomers using ESA's Integral gamma-ray observatory now say they have demonstrated beyond doubt that dead stars known as white dwarfs can reignite and explode as supernovae. 

The 'smoking gun' in this case was evidence for radioactive nuclei being created by fusion during the thermonuclear explosion of the white dwarf star, the European Space agency said.

'Integral has all the capabilities to detect the signature of this fusion, but we had to wait for more than ten years for a once-in-a-lifetime opportunity to catch a nearby supernova,' says Eugene Churazov, from the Space Research Institute (IKI) in Moscow, Russia and the Max Planck Institute for Astrophysics,in Garching, Germany.

Although Type IA supernovae are expected to occur frequently across the Universe they are rare occurrences in any one galaxy, with typical rates of one every few hundred years.

Integral's chance came on 21 January 2014, when students at the University College London's teaching observatory at Mill Hill, UK detected a type IA supernova, later named SN2014J, in the nearby galaxy M82.

According to the theory of such explosions, the carbon and oxygen found in a white dwarf should be fused into radioactive nickel during the explosion.

This nickel should then quickly decay into radioactive cobalt, which would itself subsequently decay, on a somewhat longer timescale, into stable iron. Because of its proximity – at a distance of about 11.5 million light-years from Earth, SN2014J is the closest of its type to be detected in decades – Integral stood a good chance of seeing the gamma rays produced by the decay.

Within one week of the initial discovery, an observing plan to use Integral had been drawn-up and approved.

Using Integral to study the aftermath of the supernova explosion, scientists looked for the signature of cobalt decay – and they found it, in exactly the quantities that the models predicted.

'The consistency of the spectra, obtained by Integral 50 days after the explosion, with that expected from cobalt decay in the expanding debris of the white dwarf was excellent,' says Churazov, who is lead author of a paper describing this study and reported in the journal Nature.

With that confirmation in hand, other astronomers could begin to look into the details of the process. In particular, how the white dwarf is detonated in the first place.