In the show this time we have interviews from two conferences - .astronomy and the National Astronomy Meeting. Megan rounds up the latest news and we hear what we can see in the May night sky from Ian Morison and John Field.
In the news this month: a round up of some stories from the 2011 National Astronomy Meeting, held in the town of Llandudno in North Wales during April where almost 500 astronomers from around the UK came together for a week to present and discuss their latest results.
Of all the planets so far discovered orbiting other stars, most are large gas giants orbiting close to their hosts, since these are the easiest to detect with current observational techniques. But a team at the university of Leicester have found a way of potentially spotting planets orbiting at far larger distances from their parent stars. Gas giants in our own solar system orbit further from the Sun than rocky planets like the Earth. While such planets have big surface areas and reflect large amounts of sunlight, making them bright in the visual part of the spectrum, they also emit strongly at radio wavelengths. Both Jupiter and Saturn have been detected by radio telescopes. Each planet hosts many moons, some of which are volcanicaly active, such as Io orbiting Jupiter and Saturn's moon Enceladus. Ionised gas escaping from these active moons is drawn towards the parent planets and produces aurora, much like that seen on the Earth at high latitudes. These aurora emit radio waves which can be detected here on Earth. At the National Astronomy Meeting, Dr Jonathan Nichols, from the University of Leicester, presented the results of a study which predicts that radio emission from similar auroral activity on extrasolar planets should be detectable by low frequency radio telescopes such as LOFAR, currently under construction in the Netherlands and due to be completed later this year. Nichols predicts that the technique could detect Jupiter-like planets orbiting a parent star at up to 50 times the distance between the Earth and the Sun, for stars up to 150 light years from the Earth, and may help find solar systems which resemble our own.
While Pluto may now be classified as a dwarf planet, it is still massive enough to have an atmosphere. Although less dense than the Earth's, Pluto's atmosphere was already known to be over 100 kilometres thick, but new results from a team led by Dr Jane Greaves at the University of St Andrews in Scotland have not only discovered carbon monoxide for the first time, but have also found that the atmosphere stretches as high as 3000 kilometres, a quarter of the way out to Pluto's largest moon, Charon. At such large distance from Pluto, the outer layers of the atmosphere are easily stipped away by the solar wind. Located in the far reaches of the solar system, Pluto's atmosphere is very cold, about -220 degrees Centigrade, and much of the dwarf planet's surface is covered in ice, essentially frozen out from what atmosphere there is. The signal of carbon monoxide has been searched for before, but this is the first time it has been detected. These new results, from observations made with the 15-metre James Clerk Maxwell Telescope in Hawaii, show the signal due to carbon monoxide gas is twice as strong as the previous upper limit obtained by another team using the 30-metre IRAM telescope eleven years ago. The only other gas to have been identified in Pluto's atmosphere is methane, which has also been seen to vary over timescales of several years. The changes seen in the carbon monoxide signal may be because the atmosphere has grown, or there may have been an increase in the amount of CO in the atmosphere, due to an increase in temperature as Pluto made a close approach to the Sun in 1989.
Science fiction stories are often set on planets with twin suns, but how might this kind of environment affect life on such a planet? A UK-based team, including PhD student Jack O'Malley-James from the University of St Andrews, have studied what plants might look like on an Earth-like planet with two or three suns. The temperature of a star determines its colour and therefore the light available for photosynthesis. But in a binary star system, the two stars may well have different temperatures and hence colours. Small, dim, red dwarf stars are the most common type of star in our Galaxy and are often found in binary or multiple systems with other red dwarfs, or with stars more like our Sun. The team looked at what kind of plants might evolve on planets in a variety of binary or triple star systems and found that plants in a system containing a red dwarf star may appear black to our eyes, absorbing across the entire visible wavelength range in order to use as much of the available light as possible.
And finally: High school students have been helping uncover the peculiar behaviour of a rare type of X-ray binary system. A team of astronomers based in Wales and the Netherlands have used eight telescopes simultaneously to study an X-ray binary known as IGR J00291+5934, a system containing an ordinary star and a pulsar, a neutron star spinning several hundred times a second. Only twelve examples of such a binary system are currently known. While they are often observed to go through outbursts where they increase dramatically in brightness both optically and in the X-ray part of the spectrum for between a few months and a few years, this particular binary has displayed a more unusual type of outburst. Having been in outburst for 20 days, 00291 faded back to its original brightness, before re-brightening again within a month. As well as using space-based X-ray telescopes and large optical telescopes, the team had the help of several school groups who made observations of the system using the Faulkes telescopes, a pair of 2-metre optical telescopes set up for use by school groups. In X-ray binary systems, material from the star spirals in towards the pulsar, forming an accretion disc. Friction and gravity heat this material until it reaches temperature of millions of degrees and emits X-rays. Outbursts are thought to be driven by the 'emptying' of the accretion disc, so the time between outbursts indicates the time that it takes to fill the disc, and the size of the disc itself. But for a system the size of 00291 it is unlikely that the disk could be refilled in as little as 30 days. The suggestion is that the outburst is all one event that was interrupted halfway through by a propeller effect, ejecting material from the system and stopping the outburst. Once the propeller switches off, material begins to fall inwards again, and the outburst continues. These results are part of a larger project involving optical monitoring of 32 low mass X-ray binaries by groups using the Faulkes telescopes, located in Hawaii and Australia.
Stuart brings us a round-up of some of the topics discussed at this year's .Astronomy conference which was held at New College in Oxford.
Interview with Dr Jill Tarter
Dr Jill Tarter is the Director of the Centre for SETI Research. Jill talks about SETI Quest - a new project that aims to get the world's software developers, signal engineers and anyone else to help look for patterns in the data the SETI Institute are collecting with the Allen Telescope Array. Unfortunately the array is being closed down due to funding issues although members of the public can donate to help keep it going. You can also help look for patterns in the data or help improve their software.
Interview with Professor David Hogg
Dr David Hogg (NYU) is a cosmologist who is also one of the people behind astrometry.net. The project consists of software that can analyse optical astronomical images and identify where on the sky they are. David tells us about the astrometry.net robot that analyses images in the Flickr astrometry group as well as a recent project that automatically recovered the orbit of Comet Holmes by using results from a Yahoo! image search.
Interview with Dr Megan Schwamb
Dr Megan Schwamb (Yale University) is the Project Scientist for one of the latest Zooniverse projects - Planet Hunters. The project uses data from NASA's Kepler spacecraft to allow the public to search for planets around other stars that nobody has yet discovered.
Interview with Rob Hollow
Rob Hollow (CSIRO Astronomy & Space Science) talked about "Eavesdropping from Parkes" - a project created during the .Astronomy hack day. The project turned some of the data from the Parkes radio telescope into sounds as an alternative way to investigate data. Other projects from hack day included Chromotone which converts multiwavelength astronomical images into sound, as well as the Pluto the Previous Planet song and website.
Interview with Jonathan Fay
Jonathan Fay (Microsoft Research) demonstrated the increasing capabilities of Microsoft's World Wide Telescope. Jonathan also showed how it is possible to control World Wide Telescope using a Kinect controller.
National Astronomy Meeting
The annual National Astronomy Meeting was held in mid-April in Llandudno in north Wales. In this show we have the first of many interviews recorded there.
Interview with John Womersley
John Womersley is the STFC Director of Science Programmes and was recently appointed chair of the SKA Founding Board. In this interview, John gives us an update on the status of the Square Kilometer Array, including the decision to host the SKA Project Office at the Jodrell Bank Observatory and the status of the pathfinder instruments at the two candidate sites - ASKAP in Australia and MeerKAT in South Africa.
Interview with Dr Bob Forsyth
Dr Bob Forsyth is part of the Space and Atmospheric Physics group at Imperial College in London. In this interview, he tells us about the solar cycle and how counting sunspots tells us how active the Sun is. He also explains how looking at the amounts of radioactive isotopes in ice from cosmic rays can help us to study solar cycles looking back over 9000 years. Solar cycle 23 has recently ended and was unusual because it lasted for 13 years, not 11 and also because the overall activity levels were lower than average. Bob tells us that there have been similar low levels of activity in the 1800s known as the Dalton minimum and in the 1700s (Maunder minimum) where sunspots disappeared altogether, so it is possible that there is an overlying long term trend in solar activity.
The Night Sky
Ian Morison tells us what we can see in the northern hemisphere night sky during May 2011.
Gemini sets in the south-west after sunset, while Leo rules the southern sky with its bright star, Regulus. Between these two constellations, the Beehive Cluster resides near the centre of Cancer. Below Gemini lies Canis Minor, the Smaller Dog, with its bright star, Procyon. Virgo rises in the south-east in the evening, containing its bright star, Spica, and currently playing host to the planet Saturn. `The Realm of the Galaxies', between Virgo and Leo, is home to many galaxies that are visible through a small telescope. The high density of galaxies is due to the Virgo Supercluster, a vast collection of galaxy clusters including the Virgo Cluster and our own Local Group. Ursa Major is high in the north, with the asterism of the Plough as part of it. The middle star in the handle of the Plough is a double star, Mizar and Alcor; a telescope shows that Mizar is itself a double.
- Jupiter has emerged from behind the sun (superior conjunction) and is now visible in the pre-dawn sky, rising earlier as the month progresses. It has a magnitude of -3.1 and an angular size of 33", but its position just above the horizon makes atmospheric seeing relatively poor.
- Saturn is high in the south in the late evening, ideal for observations. Its magnitude decreases from +0.5 to +0.7 during the month as it moves away from Earth. The rings are opening out and have now reached 8° from edge-on, making the planet brighter than it was a year ago. The angular diameter of the ring system is 43", compared to 19" for the planet, and a small telescope reveals the dark Cassini Division between the A ring and the bright B ring. Saturn's largest moon, Titan, is also apparent through a telescope at magnitude +8, while smaller moons can also be seen under good conditions.
- Mercury is low in the east just before dawn, and you may require binoculars to see it through the atmosphere.
- Mars appears alongside Jupiter, Mercury and Venus in the early morning. The ecliptic - the plane in which the planets orbit - makes a shallow angle with the horizon at dawn, resulting in the low elevation of these three planets. Mercury has a small angular size of 4" and a magnitude of +1.3, slightly dimmer than last month.
- Venus is a morning object, but is getting closer to the Sun in the sky. At magnitude -3.8, it is the brightest object in the sky apart from the Sun and Moon. Its angular size drops from 11.6 to 10.6" this month as it moves away from us, but the illumination of its disc rises from 88 to 93% in the manner of a waxing Moon, keeping its brightness constant.
- Saturn is in a good position to be observed this month, and will continue to become more visible until 2016 as its rings open out. Surface detail on the planet, such as a dark band in the northern hemisphere, can be made out with a small telescope.
- Saturn appears just to the left of Porrima (Gamma Virginis), a double star, towards the end of the month. The two stars, each of magnitude +3.5, are currently 1.7" apart, and separable using a small telescope.
- The Eta Aquariid meteor shower peaks early on the 6th, three days after new Moon, when the sky is dark. The radiant (apparent origin) of the meteors is in Aquarius, so the meteors are best seen low to the east-south-east around 04:00 BST (British Summer Time, one hour ahead of Greenwich Mean Time), when you should be able to see around 25 per hour if the sky is clear. This shower is composed of dust from Halley's Comet, released when it passed near the Sun and now spreading out across the Earth's orbit.
- The waning crescent Moon passes among the pre-dawn planets Mercury, Venus, Mars and Jupiter each morning from the 29th to the 31st. If the sky is not too hazy, look to the eastern horizon around 04:30 BST to see the planets in a line from Jupiter, highest in the east, to Mercury, lowest in the east-north-east.
John Field from the Carter Observatory in New Zealand speaks about the southern hemisphere night sky during April 2011.
May is a great month to observe galaxies, the most distant objects to be found in the night sky. The band of our own galaxy, the Milky Way, runs east to west in the evening sky, leaving the north and south comparatively sparsely populated with bright stars. For many years, the Milky Way was believed to encompass the entire Universe. Astronomers tried to plot the shape and size of this universe by measuring the number of stars and estimating their distances using their brightnesses. William Herschel (1738-1822) was one such astrononomer who, along with others, noticed fuzzy shapes that were termed `nebulae'. They believed them to be either unresolved star clusters or, in the case of spiral structures, nascent solar systems. As telescopes became more powerful, many clusters along the Milky Way were found to be star clusters embedded in clouds of luminous material, but other clusters, mostly away from the galactic plane, still could not be resolved into individual stars. In the twentieth century, Edwin Hubble (1889-1953) used the changing luminosities of Cepheid variable stars in the Great Andromeda Nebula to show that it was millions of light years away - a separate galaxy much more distant than the stars of the Milky Way. A large number of amateur astronomers are today involved in long-term observation programmes of variable stars and in supernova hunts, both of which help to refine the measured distances to other galaxies. The two closest galaxies visible in the southern hemisphere sky are the Large and Small Magellanic Clouds. Both are circumpolar as seen from Aotearoa (New Zealand), and can be seen even where there is moderate light pollution. Galaxies are classified by their shapes. An interesting elliptical galaxy that can be found with a small telescope is Centaurus A, also known as NGC 5128, 15 million light-years away. The fifth-brightest external galaxy in the sky, it lies 4° north of the naked-eye globular cluster Omega Centauri and is itself just visible to the naked eye of a sharp observer. Through a telescope, it appears as an oval with a dark band running lengthways. The galaxy NGC 253, 11 million light-years away, is at 8th magnitude and can be seen with binoculars. A small telescope shows it to be an oval bulge with a bright nucleus, while a larger telescope reveals a disc containing dark bands. Nearby is the globular cluster NGC 288, visible through a telescope. In the northern sky, M104, the Sombrero Galaxy, is in the constellation of Virgo. It is visible with binoculars, while a medium-sized telescope allows you to see the dark lane that makes it resemble a sombrero. Virgo is rich in galaxies, as it contains the Virgo Cluster of 1300 galaxies. The largest of these is M87, which is up to 200 times the mass of the Milky Way and shines at magnitude +10. Long-exposure images reveal jets of material escaping from its core, which are believed to be the ejecta of a supermassive black hole. Virgo is one of the zodiacal constellations through which the Sun moves, and is associated with the goddess of wheat in Greek and Roman mythology. Her brightest star is Spica, the 15th brightest in the night sky, which is a variable blue giant in a binary system 260 light-years away. The constellation of Capricorn, the Goat, rises later in the evening. Vesta, the brightest asteroid in the Solar System, currently resides there. Crux, the Southern Cross, is high overhead in the evening sky. The constellations of Carina, the Keel, and Vela, the Sails, are home to a number of bright stars, clusters and nebulae. Scorpius and Sagittarius rise in the east after sunset.
- Saturn currently appears in Virgo.
- Venus is still the brilliant `Morning Star', appearing alongside Mars, Mercury and Jupiter.
- Jupiter and Mars are close together on the 2nd.
- Jupiter, Venus and Mercury are in close proximity (conjunction) on the 12th.
- Mercury, Venus, Mars and Jupiter all congregate on the 22nd, much higher in the morning sky than earlier in the month.
Odds and Ends
The Hubble Space Telescope celebrated its 21st birthday in April. An optical telescope with a mirror 2.4 metres in diameter, Hubble's position orbiting the Earth has allowed it to capture stunning and scientifically valuable images without the hindrance of the Earth's atmosphere. An image of two interacting galaxies forming a rose shape, captured by Hubble in December 2010, was released to mark the anniversary.
At the time of recording this episode, Endeavour's final mission was scheduled for launch on April 29, delayed from April 19. However, it was again delayed and as of May 1 is delayed until at least May 8.
|Interview:||Dr Jill Tarter and Stuart Lowe|
|Interview:||Dr David Hogg and Stuart Lowe|
|Interview:||Dr Megan Schwamb and Stuart Lowe|
|Interview:||Robert Hollow and Stuart Lowe|
|Interview:||Jonathan Fay and Stuart Lowe|
|Interview:||John Womersley and Megan Argo|
|Interview:||Dr Bob Forsyth and Jen Gupta|
|Night sky:||Ian Morison and John Field|
|Presenters:||Jen Gupta, Melanie Gendre, Cat McGuire and Mark Purver|
|Editors:||Jen Gupta, Megan Argo, Claire Bretherton, Melanie Gendre, Cat McGuire and Mark Purver|
|Segment Voice:||Liz Guzman|
|Website:||Jen Gupta and Stuart Lowe|
|Cover art:||The Jodcast team on Llandudno beach at NAM 2011 CREDIT:: Mike Peel|