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The Rosetta Mission ~ Nick James

In November 1993, the International Rosetta Mission was approved as a Cornerstone Mission in ESA's Horizons 2000 Science Programme.  Since then, scientists and engineers from all over Europe and the United States have been combining their talents to build an orbiter and a lander for this unique expedition to unravel the secrets of a mysterious 'mini' ice world – a comet.

Initially scheduled for January 2003, the launch of Rosetta had been postponed due to a failure of an Ariane rocket in December 2002. The adventure began March 2004, when a European Ariane 5 rocket lifted off from Kourou in French Guiana.  During a circuitous ten-year trek across the Solar System, Rosetta will cross the asteroid belt and travel into deep space, more than five times Earth’s distance from the Sun. Its destination will be a periodic comet known as Comet 67P/Churyumov-Gerasimenko.

The Rosetta orbiter will rendezvous with Comet 67P/Churyumov-Gerasimenko and remain in close proximity to the icy nucleus as it plunges towards the warmer inner reaches of the Sun’s domain. At the same time, a small lander will be released onto the surface of this mysterious cosmic iceberg.  More than a year will pass before the remarkable mission draws to a close in December 2015. By then, both the spacecraft and the comet will have circled the Sun and be on their way out of the inner Solar System.

Rosetta is controlled on Earth via a communications system developed in Essex and known as the Intermediate Frequency Modem System (IFMS). The system is capable of measuring Rosetta’s speed to within fractions of a millimetre per second and its distance to within a metre anywhere in the Solar System.  The probe is moving at speeds of up to 55,000km/h more than 500,000km away. The IFMS is also the means by which all the imagery and data sent back on Earth.

Tonight's speaker, Nick James, has been involved in the development of Rosetta's IFMS system. Professionally, Nick is an engineer in the space industry, leading a team responsible for implementing highly sensitive and accurate systems for receiving and processing signals from deep-space spacecraft. He is also a STEM ambassador involved in a number of initiatives to encourage young people to take up science and engineering as a career.

Nick has been interested in astronomy for as long as he can remember, certainly since the age of 8. He has been a member of the British Astronomical Association since he was 12 and is about to become the director of its Comet Section. Nick is also Assistant Editor of The Astronomer Magazine. He has written many articles for magazines and books, and co-authored Observing Comets which was published in 2003 as part of Sir Patrick Moore’s Practical Astronomy series.

Nick has a run-off observatory in Chelmsford containing an automated 11-inch Schmidt-Cassegrain telescope and uses this, along with remote telescopes, to observe a wide range of transient objects from Near Earth Objects to distant supernovae.

Evidence for Population III Stars ~ Tony Baxter

Stars observed in galaxies were originally divided into two populations by Walter Baade in the 1940s. Although a more refined means of classifying stellar populations has since been established (according to whether they are found in the thin disk, thick disk, halo or bulge of the galaxy), astronomers have continued to coarsely classify stars as either Population I (Pop I, metal-rich) or Population II (Pop II, metal-poor). However, even the most metal-poor Pop II stars have metallicities (commonly denoted [Z/H]) far above that of the gas left over from the Big Bang.

For this reason, astronomers have introduced a third class of star. Population III (Pop III) stars are composed entirely of primordial gas – hydrogen, helium and very small amounts of lithium and beryllium. This means that the gas from which Pop III stars formed had not been ‘recycled’ (incorporated into, and then expelled) from previous generations of stars, but was pristine material left over from the Big Bang. As such, these stars would have a [Z/H] ~ -10 and would constitute the very first generation of stars formed within a galaxy. These Pop III stars would then produce the metals observed in Pop II stars and initiate the gradual increase in metallicity across subsequent generations of stars.

The only problem is that Pop III stars are hypothetical. Despite intense searches, no Pop III star had ever been observed, that is until this year with the discovery of CR7.  Tony will present the latest findings in this area of research

The Local Group