May 2009: May the 4th be with you

It's Roy's last episode of the Jodcast and we welcome some of the new Jodcast Juniors who were our roving reporters at the Joint European and National Astronomy Meeting (JENAM) this year.

The News

In the news this month:

• A team of astronomers have discovered a mysterious object in the early universe which could be one of the earliest ancestors of a forming galaxy ever detected. The object is almost 13 billion light years away when the Universe was only 6% of its current age, and is a type of object known as a Lyman alpha emitter. As the Universe expanded after the Big Bang, it slowly cooled, eventually allowing gas to form as the protons and electrons in the hot primordial plasma combined to form hydrogen atoms. Galaxies started to form when this neutral, opaque gas began to collapse under gravity, forming stars which ionised the surrounding gas making the Universe transparent in what is known as the Epoch of Reionisation. This occurred between about 150 million and one billion years after the Big Bang. This mysterious object, dubbed "Himiko" by its discoverers, is a giant blob of hydrogen gas 55 thousand light years across, roughly the radius of the Milky Way, and formed when the Universe was a mere 800 million years old. Finding such a large object so far back in time was unexpected since it is thought that small objects formed first and then merged to create larger objects over time. Named after particular spectral signature of hydrogen, many smaller examples of these Lyman alpha emitters are known, although most exist at a time when the Universe was between two and three billion years old. Himiko is unique in other ways too. It is both the brightest and largest Lyman alpha object yet discovered. Its character is something of a mystery however. In a paper accepted for publication in the Astrophysical Journal, the authors make several suggestions based on their observations so far, including gas ionised by a hidden supermassive black hole, clouds of ionised hydrogen in very early galaxy, gas falling onto a massive dark halo object generating a massive starburst, a merger of giant gas clouds, or outflowing gas from a starburst or merger. With the data available, it is not clear which of these suggestions is correct, but the researchers point out that observations with the Atacama Large Millimetre Array when it is complete should narrow down the possibilities by characterising the dust and molecular gas properties of the object.
• Astronomers using a telescope in Spain have detected two of the most complex molecules ever found in interstellar space in a region known as Sagittarius B2, close to the Galactic centre. While hydrogen accounts for approximately three quarters of the visible matter in the Universe, many heavier elements are also present. Under the right conditions, these elements can form bonds creating a variety of different molecules. Like atoms, molecules emit electromagnetic radiation at very specific frequencies, resulting in a characteristic fingerprint of lines in the spectrum of an astronomical object. Detecting complex molecules in space involves searching for these fingerprints and trying to disentangle overlapping lines from different molecules. So far, more than 150 different molecules have been detected either in the interstellar medium or around stars. These include various organic molecules, those containing carbon atoms, although those found to date are much simpler than the amino acids which are the building blocks of all life here on Earth. Astronomers studying the chemistry of the Sagittarius B2 region have previously found numerous different large molecules including alcohols, aldehydes and acids. The cloud itself is a hot, dense ball of gas around a luminous young star in a known star forming region located approximately 100 parsecs from the Galactic centre. The new study, led by Arnaud Belloche at the Max Planck Institute for Radio Astronomy in Germany and published in the journal Astronomy and Astrophysics, used the IRAM 30m telescope on Pico Veleta in Spain to obtain sensitive spectra of the region. When theteam analysed their data, they discovered the spectral signatures of ethyl formate and n-propyl cyanide, two of the most complex molecules discovered in space so far. Some chemicals form by the collision of particles in a gas cloud, but astrochemical models suggest that more complex molecules form on small dust grains from individual atoms and simple molecules reacting together. Larger, more complex molecules are then formed by the addition of further simple molecules to the chain. While the simplest amino acids, glycine, has not yet been detected in space, its size and complexity is similar to ethyl formate and n-propyl cyanide, suggesting that future surveys with more sensitive instruments could detect amino acids.
• When two asteroids collide, they create a family of fragments with newly exposed surfaces. As these fragments age, they become redder in colour, but the actual process, and the timescales over which they act, have been heavily debated. A team of researchers, led by Pierre Vernazza of the European Space Agency, have observed asteroids from different groups with various ages and compositions, and concluded that the ageing process is far more rapid than though. The research, published in Nature (PDF) during April, not only shows that asteroid surfaces age and redden in less than one million years, but that the solar wind is the most likely cause of this weathering. While human skin is damaged over time by repeated exposure to the Sun's ultraviolet light, it is the highly energetic particles in the solar wind which damages the outer layers of an asteroid, destroying the molecules and crystals on the surface and forming a thin crust of material with distinctive properties. By studying different families of asteroids, the team found that the composition of an asteroid is an important factor in determining how red its surface becomes. After the initial rapid reddening during the first million years, the surface ages more slowly with the colour determined more by composition than by age. Their research also showed that collisions alone cannot account for the high proportion of fresh-looking surfaces seen on near-Earth asteroids: roughly 10% of 1-km size near Earth objects appear to have unreddened surfaces. Instead, they suggest that these may be the result of planetary encounters where tidal shaking could expose fresh, unaltered material. The authors point out that, if this is the case, then a comparison of the colours of near-Earth asteroids with similar asteroids in the main asteroid belt should show a greater abundance of redder objects away from the Earth in the main belt.
• The discovery of the lightest exoplanet found so far was announced at the Joint European and National Astronomy Meeting at the University of Hertfordshire on the 21st of April. This is the fourth planet discovered in the Gliese 581 system, orbiting a star located 20.5 light years away in the constellation Libra. The planet, known as Gliese 581 e, has a mass just 1.9 times that of Earth and orbits its parent star in just 3.15 days. The team, led by Michel Mayor of Geneva Observatory, have been searching for planets using the HARPS spectrograph on ESO's 3.6-metre telescope at La Silla in Chile for more than four years. The same study found that one of their previous planetary discoveries is located within the habitable zone of Gliese 581, a low mass red dwarf star. While the mass of this planet means it is unlikely to be a rocky, Earth-like planet, its location in the habitable zone means there could be liquid water on its surface. The results of the study have been submitted for publication in the journal Astronomy and Astrophysics (PDF).

JENAM 2009

The European Week of Astronomy and Space Science incorporating the RAS NAM 2009 and the EAS JENAM 2009 took place at the University of Hertfordshire from 20-23rd April. A crack team of Jodcast roving reporters were there and brought back the following interviews:

Interview with Professor Andy Fabian (Institute of Astronomy)

Jen, Neil and Kerry talked to Andy Fabian (Institute of Astronomy, President of the RAS) about the Joint European National Astronomy Meeting held at the University of Hertfordshire

Interview with Dr Jane Greaves (University of St Andrews)

Following up on an interview at NAM last year, Jen and Kerry talked to Jane Greaves (University of St Andrews) about the eMERLIN legacy project PEBBLES (Planet Earth Building Blocks - a Legacy eMERLIN Survey) to observe circumstellar disks around stars and try to find planets forming.

Interview with Dr Joeri van Leeuwen (ASTRON)

Neil talked to Joeri van Leeuwen (ASTRON) about ASTRON, LOFAR and pulsars.

Interview with Dr Chris Benn (ING)

Adam talked to Chris Benn, Head of Astronomy at the Isaac Newton Group of Telescopes, about the facilities at ING, new instruments at the telescopes and finding exo-planets.

Interview with Dr René Oudmaijer (University of Leeds)

Neil talked to René Oudmaijer (University of Leeds) about an attempt to find very young stars in our galaxy.

Interview with Dr Linda Tacconi (Max-Planck-Institut für extraterrestrische Physik)

Dandan talked to Linda Tacconi (Max-Planck-Institut für extraterrestrische Physik) about star-forming galaxies in the deep universe which are different from galaxies nearby. Her research helps us to understand how the first galaxies started to grow in the early universe.

Interview with Dr Andrew Levan (University of Warwick)

Neil talked to Andrew Levan (University of Warwick) about short gamma ray bursts.

The Night Sky

Ian Morison tells us what we can see in the night sky during May 2009.

Northern Hemisphere

In order to see a dark sky in May you have to wait up quite a bit but when it does get dark you'll see Gemini, with its bright stars Castor and Pollux, setting towards the south west. Leo is holding pride of place in the south and below it is the planet Saturn. Below Gemini is the constellation of Canis Minor. Over to the south east is the constellation of Virgo with the bright star Spica. Between Spica and the tail of Leo is the Realm of the Galaxies. Here you'll find the Virgo Supercluster of galaxies. Our own local group of galaxies is on the outskirts of this supercluster. On the night sky pages you'll find some of the nice things you can see in these constellations with binoculars or a small telescope.

Jupiter is a morning object. It rises before the Sun but because the ecliptic is fairly low, it will only be around 20 or so degrees above the horizon before dawn. Even so, you'll have a chance to look at the Galilean moons. On May 17th Jupiter is just below the last quarter Moon in the pre-dawn sky. Mars is also low in the pre-dawn sky and is beginning to rise increasing earlier than the Sun as the month progresses. It has a magnitude of about +1.2. Venus passed between the Earth and the Sun in March. It will only lie 12 degrees above the horizon as the Sun rises on the first of May, so will be easier to spot later in the month. It is at magnitude -4.4 at mid month, up and to the right of Mars. In the middle of May, a small telescope will show a crescent phase equivalent to just before a first quarter Moon. An interesting fact about its brightness is that it stays pretty constant at about -4.4 (not +4.4) for most of the time that it is visible even though the apparent phase changes greatly. When the phase is thin, Venus is nearer to us and the effective reflecting area of Venus as seen from Earth remains pretty constant. May is prehaps the last month to see Saturn well in the evening sky. It starts the month at magnitude +0.8 and that falls to about +0.9 as the month progresses. On May 2nd we have the best chance to see Mercury next to the Pleiades Cluster about half an hour after sunset if you have a good low western horizon. On May 21st there is a chance to see Venus, Mars and the thin crescent Moon in the hour before dawn.

Southern Hemisphere

The New Zealand Astronomical Year Book has some lovely maps for each month showing you what you can see. Low in the south is a fairly empty part of the sky but the Small Magellanic Cloud is roughly due south around 9pm in early May. Above that to the right is the Large Magellanic Cloud. As we go through summer towards autumn, the Milky Way gets higher in the sky. The centre of our galaxy - towards the constellation of Sagittarius is just rising in the south-east. Above that is the constellation Scorpius. One way to find the Southern Cross is to use the Pointers - alpha and beta Centauri - which point up towards it. Beta Centauri does not appear as bright as Alpha Centauri but is actually about 100 times further away so is actually a very bright star. Up to the left of Beta Centauri past another bright star you should see a fuzzy glow with binoculars. This is Omega Centauri and was thought to be a globular star cluster. Recent analysis of the stars ages in Omega Centauri indicate that it may be the core of a galaxy that had its outer parts ripped off as came close to the Milky Way.

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