CAP and NAM. In the show this time we get an update on two recent conferences that Jodcast presenters were lucky enough to attend. Megan brings us a series of interviews from the Communicating Astronomy with the Public conference. Jen and Stuart find out about the National Astronomy Meeting 2010, planets orbiting backwards and the possibilities of life elsewhere in the Universe. As ever we have the latest astronomical news, and what you can see in the May night sky.
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In the news this month:
Many stars vary in brightness, sometimes due to changes within the star itself such as novae or Cepheid variables, others because of external factors. One well-known variable star is epsilon Aurigae, an F-type supergiant in the constellation of Auriga, located at an estimated distance of 625 parsecs (2,100 light years). Since its variable nature was discovered in the 1820s, the star has been seen to fade in brightness every 27.1 years. During these eighteen-month-long eclipses, the brightness of the star fades to around 50 per cent of its normal magnitude. While the variability of the system has been well-studied, the exact physical nature of the eclipsing companion is less certain as it has remained undetected, and many models have been put forward to explain the unusual nature of the system. Observations of epsion Aurigae show that the star and its darker companion have a similar mass which, until recently, was thought to be around 15 times the mass of the Sun. More recent observations have shown that the supergiant star has a much lower mass of between two and three solar masses, and that the companion may be a single B5V-type star embedded within a disk of opaque material.
Now, using the CHARA interferometer, an array of infrared telescopes located on Mount Wilson in California, a team led by Brian Kloppenborg from the University of Denver have for the first time imaged the eclipsing object as it transits the disk of the star. This is the first time a spatially resolved observation of an eclipsing binary has been made. Their observations show that the eclipsing object is an opaque disk of dust, tilted to our line of sight by an estimated 84 degrees. From the motion of the disk between two observations carried out in November and December 2009, the team infer that the companion object is more massive than the visible F-type supergiant. Assuming the B-type star within the disk has a typical mass of 5.9 solar masses, the researchers calculate a mass of 3.6 solar masses for the F-type supergiant. They also calculate that if the disk is composed entirely of dust, then its mass is less than 10 per cent of the Earth's.
While the nature of the disk is now clearer, there are still several unanswered questions which remain. The model that best fits the data is of a geometrically thin disk tilted to our line of sight, rather than a thick disk seen edge on. However, the fact that it is opaque suggests that its nature is more like a debris disk than a dusty accretion disk around a young stellar object. The tilted disk model also predicts a central hole which should cause a mid-eclipse brightening of the F-type star. Observers the world-over will continue to monitor the system during the eclipse, and the data should help build up a profile of the disk and constrain the evolutionary history of the system.
- Most known extrasolar planets are massive gas giants orbiting close to their parent stars. If one of these planets happens to pass directly between us and its parent star during its orbit, then sensitive spectroscopy can be used to determine the chemical make-up of its atmosphere. Models of such atmospheres predict which gases should be present and in what relative abundances, based on physical conditions such as the temperature. Recent infra red observations carried out with the Spitzer Space Telescope have provided the first details of the atmospheric composition of a so-called hot Neptune. The planet, known as GJ 436b, orbits an M-type dwarf star in the constellation of Leo. It is similar to Neptune in size, but orbits its parent star in just 2.6 days. Previous observations of the planet showed that its surface temperature was estimated to be 712 K, higher than predicted due to stellar heating alone, and the new observations (reported in the April 22nd issue of Nature) suggest that its atmosphere may not be in equilibrium. The team, led by Kevin Stevenson at the University of Central Florida, observed the planet's day side as it passed around the far side of the star and examined the infra red spectrum for various chemical signatures. What they found was a high abundance of carbon monoxide and a deficiency of methane compared to predictions from atmospheric models at this temperature for an atmosphere thought to be dominated by hydrogen. In an atmosphere such as this, methane (one carbon atom and four hydrogen atoms) should be the main carbon-bearing molecule, but the observations show the actual abundance is less than that predicted by a factor of seven thousand. The large amount of absorption due to carbon monoxide is also unexpected, the results suggesting that the atmosphere may not be in thermochemical equilibrium. One alternative explanation considered by the authors is that the atmosphere may not be dominated by hydrogen, but this is unlikely given the dominance of hydrogen in planet forming disks. Another possibility is that vertical mixing within the atmosphere may dredge up carbon monoxide from lower, hotter parts of the atmosphere, although the authors point out that, in order to explain the observed abundances, the amount of mixing would have to be large. These new data will provide useful information for future atmospheric modeling.
- Closer to home, the planet Venus shows large amounts of evidence of volcanic activity. Despite being shrouded under a thick layer of cloud, spacecraft have been able to map the surface of our nearest neighbour using radar, leading to the realisation that much of the planet's surface is comparatively young, suggesting that at some point in the recent past the planet underwent a complete resurfacing. However the question remains whether Venus is currently a geologically active planet. Most of the planet's surface is known to be covered by features caused by volcanic activity: shield volcanoes, coronae, pancake domes and other features caused by lava flows or crustal uplifts. The relative lack of craters, compared to known ancient surfaces like the Lunar and Martian highlands, implies that the surface is comparatively young. While the thick atmosphere of Venus prevents observers from seeing directly signs of current volcanic activity, a team using data from the Visible and Infrared Thermal Imaging Spectrometer on board the European Space Agency's Venus Express orbiter have discovered evidence of recent resurfacing. They used data from the VIRTIS instrument to examine closely several known hot spots on Venus. These hot spots are analogous to their terrestrial counterparts such as the Hawaiian chain of islands in that they have distinctive rises compared to the surrounding terrain, major volcanic centres and gravitational anomalies, suggestive of active plumes of material flowing up through the planet's mantle. By studying the thermal emissivity of these regions, the researchers have identified compositional differences in lava flows at these hot spots compared to the surrounding surfaces, which they interpret as being due to a lack of surface weathering. Since weathering is a gradual process which occurs over long time scales, this all implies that the features are younger than 2.5 million years, and possibly much younger, showing that Venus has been actively resurfacing, at least partially, in the recent past. The results were published in Science Express on April 8th.
- NASA's Solar Dynamics Observatory made its first light observations during April. Launched aboard an Atlas V rocket on February 11th, the spacecraft is on a five year mission to observe our nearest star in detail. The observations will help solar physicists understand solar activity and how it impacts us here on the Earth. The first light observations were released on April 21st and show a turbulent and dynamic surface. As well as taking images at a variety of wavelengths in order to probe different levels of the solar atmosphere, the instruments on board SDO can pick out features as small as 350 km across and take images every few seconds so events can be studied in detail. One of the main goals of SDO is to try and understand how the Sun's magnetic field is generated and how the energy stored in the magnetic field is released into the heliosphere. Data from SDO's instruments should help predict solar variations that affect life here on Earth. Images and movies from the first light observations are available on the SDO website.
Megan attended the Communicating Astronomy with the Public meeting in Cape Town, South Africa earlier in the year. While she was there she managed to record some interviews for us.
Prof George Miley tells us about Commission 55 of the International Astronomical Union. The IAU has recently developed a strategic plan for astronomy (PDF) in the developing world. George tells us how astronomy is a unique tool to inspire children to pursue a career in science and technology.
Kevin Govender talks about organising the CAP2010 meeting.
Dr Carolina Odman shares her experience of CAP2010.
Dr Pamela Gay talks about the cultural challenges of astronomy outreach and education in the developing world.
Prospery Simpemba is a founding member of Space Science Zambia Chapter of Astronomers Without Borders. Prospery tells us about the work of Astronomers Without Borders which brings people together to share the beauty of the night sky.
Avivah Yamani tells us about astronomy in Indonesia during the International Year of Astronomy.
Saevar Bragason tells us about astronomy in Iceland during the International Year of Astronomy. Iceland has 3 months with no dark skies during the summer. During the winter Iceland is affected by clouds but also the aurora.
Mponda Malozo tells us about IYA2009 activities in Tanzania.
Cameron Hummels is the Director of the public outreach programme for astronomy at Columbia University in New York city. During IYA2009 they organised a series of public talks and also took telescopes into Harlem to show passers-by the Moon and planets. Cameron also tells us about guerilla astronomy on subway trains in the New York Metro.
Pedro Russo talks about the huge global success of the International Year of Astronomy.
National Astronomy Meeting 2010
Jen and Stuart attended the UK's National Astronomy Meeting; an annual astronomy meeting that brings together the UK's astronomers, solar and terrestrial physicists. This year it was held in Glasgow to celebrate the 250th anniversary of the founding of the Regis Chair of Astronomy at Glasgow. Dr Lyndsay Fletcher tells us about NAM, Astronomer Royal for Scotland John Brown, astronomy in Glasgow, and the conference ceilidh. We'll be bringing interviews from NAM to you over the next few episodes but you can hear more interviews by Ben of the Naked Scientists and watch some video interviews from Astronomy Now.
Professor Andrew Cameron tells us about the SuperWASP project. The project is aimed at finding large numbers of planets orbiting other stars whose orbits take them between us and their star. At NAM the SuperWASP team announced the discovery of nine new planets. Two of the new planet discoveries orbit their stars in the opposite direction to their star's spin and bring the total number of "backwards planets" to six. These planets provide a challenge to the understanding of how planets are formed.
Biochemist Dr William Bains tells us about his interests in astrobiology and he studies the possibility of life forming from basic chemical principles. He investigates the chemistry available in extremely non-Earth-like environments, such as the surface of Saturn's moon Titan, for life to start.
The Night Sky
Ian Morison tells us what we can see in the night sky during May 2010.
The nights are getting rather short in the northern hemisphere. After sunset Gemini is setting in the west with Leo the Lion in the south or south west. Over to the left of Leo is the constellation of Virgo which currently contains the planet Saturn. Between the tail of Leo and the brightest star in Virgo is the Realm of the Galaxies - the Virgo supercluster of galaxies. High overhead we have Ursa Major with a group of stars forming the Plough. Looking at the three stars making up the tail of the bear (the handle of the Plough) you can easily see with binoculars that the middle of those three is actually a double star. As the night continues you'll see the bright star Arcturus over in the east. The brightest stars of Hercules make the keystone where you can find the globular cluster M13 which looks nice in binoculars. Below Hercules is the constellation of Ophiuchus.
- Jupiter, having passed behind the Sun on the 28th February, has now reappeared in the pre-dawn sky. At the beginning of May it will rise in the east as morning twilight begins and, at magnitude -2.1, could be seen in binoculars given a clear low eastern horizon.
- Saturn may now be easily seen in the south after sunset lying in Virgo down to the lower left of the constellation Leo. It can then be seen for much of the night with a magnitude +0.8 rising (which means getting fainter) to +1 during the month.
- Mercury passed in front of the Sun on April 28th and will appear in the morning twilight sky during the latter part of May reaching its greatest elongation from the Sun on the 26th. However, the ecliptic is at a very shallow angle to the horizon and so Mercury will only lie about 5 degrees above the horizon half an hour before sunrise. You might just be able to pick it out with binoculars given a very low eastern horizon. Remember not to look directly at the Sun.
- Mars remains visible in the south-west after sunset. It is now moving ~1/2 degree a day eastwards from Cancer into Leo. On the 31st May, it will lie just 3.5 degrees to the right of Regulus.
- Venus is now prominent in the evening sky after sunset in the west north-west. At magnitude -3.9, it will be easily spotted - the brightest object in the night sky after the Moon.
- At around 05:00 am, on the 9th and 10th of May, a waning crescent Moon will lie close to Jupiter in the pre-dawn sky.
- On Sunday 16th May, the Moon passes just below the planet Venus. Its closest approach is at 10:00 BST when the Moon's northern edge is just 0.25 degrees below the planet. They lie around 30 degrees away from the Sun, but still be VERY careful when searching for them and keep your binoculars well away form the Sun!!
- These are two good nights to observe an interesting feature on the Moon if you have a small telescope. Close to the limb (on the 25th May) is the bright crater Aristachus, some 41km in diameter. It is a young crater, some 450 million year old and shows some rays projecting from it. It lies close to the 36km diameter crater Herodotus which is close to the starting point for the very interesting "Schroter's Valley".
- In the early hours of the morning on the 28th of May the full Moon, seen low in the south, will occult the star Sigma Scorpii.
- In the early hours of the morning at the end of May, binocuars should help you spot a comet. During May, Comet McNaught passes low in the north-east below the constellations of, first, Pegasus and then Andromeda. It will be easiest to spot at the very end of the month when it should have reached magnitude 8, so fairly obvious in binoculars. On the 31st May, it will lie just below the star Beta Andromedae. This star is on the "star hop" route to M31: starting at the top left star (Alpha Andromedae) of the Square of Pegasus, go left and a touch down to a star and then continue left by the same amount but a touch up to reach Beta Andromedae. Here one normally turns sharp right past one star to get to M31, but instead just drop below Beta Andromedae to find the comet appearing as a "fuzzy" object.
The Milky Way is arcing over from the east to the west fairly high in the south. Almost straight up above you is the little constellation of Crux - the Southern Cross. On the way to Crux, from the pointers, you turn left and go up a bit you might spot another fuzzy object named Omega Centauri. Omega Centauri may be the core of a small galaxy rather than a globular cluster as previously thought. Down towards the east is Scorpius with the Southern Jewelbox at the bottom. Sagittarius is rising in the east and rises higher later in the evening.
Odds and Ends
The European Southern Observatory have announced that they've chosen a site for the future European Extremely Large Telescope (E-ELT). The site will be Cerro Armazones in the Chilean Andes.
We also mentioned Under British Skies which you can hear on Astronomy.FM.
|Noticias en Español - Mayo 2010:||Lizette Ramirez|
|Interview:||Prof George Miley and Megan Argo|
|Interview:||Kevin Govender and Megan Argo|
|Interview:||Dr Carolina Odman and Megan Argo|
|Interview:||Dr Pamela Gay and Megan Argo|
|Interview:||Prospery Simpemba and Megan Argo|
|Interview:||Avivah Yamani and Megan Argo|
|Interview:||Saevar Bragason and Megan Argo|
|Interview:||Mponda Malozo and Megan Argo|
|Interview:||Cameron Hummels and Megan Argo|
|Interview:||Pedro Russo and Megan Argo|
|Interview:||Dr Lyndsay Fletcher and Stuart Lowe|
|Interview:||Prof Andrew Cameron and Jen Gupta|
|Interview:||Dr William Bains and Jen Gupta|
|Night sky this month:||Ian Morison|
|Presenters:||David Ault, Jen Gupta and Stuart Lowe|
|Editors:||Adam Avison, Iain McDonald, Mark Purver and Chris Tibbs.|
|Intro/Outro voices:||Julia Linthicum, Chip Joel, Gwendolyn Jensen-Woodard, Fiona Thraille and David Ault|
|Segment voice:||Nadya Kunawicz|
|Cover art:||CAP2010 Credit: IAU Commission 55|