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April 2011: Arriba! Arriba!

April 2011

In this episode we talk to 4 members of the Jodrell Bank Centre for Astrophysics: Dr Bob Watson tells us about the cosmic microwave background radiation, Dr Cristobal Espinoza tells us about pulsar glitches, Dr Jaime Pineda tells us about star formation and Matias Vidal tells us about cosmology. As usual, Megan has the latest astronomical news and Ian Morison and John Field tell us what's in the night sky.

The News

Interview with Dr Bob Watson

Dr. Bob Watson works at the Jodrell Bank Centre for Astrophysics investigating the cosmic microwave background (CMB). In this interview, he explains the techniques used to map the CMB and tells us about the QUIJOTE experiment and how data from this will help us to understand more about the formation of the Universe.

Interview with Dr Cristobal Espinoza

Dr. Cristobal Espinoza is part of the pulsar group at the Jodrell Bank Centre for Astrophysics. In this interview, he tells us about his research into how pulsars are slowing down. During this process, some pulsars present features called glitches, Cristobal explains how these glitches are measured and what they can tell us about the inner parts of a neutron star.

Interview with Dr Jaime Pineda

Dr Jaime Pineda is a COFUND ESO fellow for ALMA based at the Jodrell Bank Centre for Astrophysics. In this interview he tells us about star formation and how he observes the very beginning of this process in the Milky Way. Jaime talks about how he measure the dynamics inside the molecular clouds where stars are forming, the telescopes is he using at the moment, and how he plans to use ALMA in the near future.

Interview with Matias Vidal

Matias Vidal is a PhD student at the Jodrell Bank Centre for Astrophysics studying the cosmic microwave background radiation (CMB). In this interview, he tells us about his work trying to observe the CMB B-modes, a type of polarization of the CMB radiation, and how observing these B-modes would help our understanding of the inflation period at the beginning of the Universe.

The Night Sky

Northern Hemisphere

Ian Morison tells us what we can see in the northern hemisphere night sky during April 2011.

The winter constellations of Orion, Taurus and Gemini now set in the west in the evening, while Leo the Lion is in the south. His brightest star, Regulus, is the Lion's front knees, while the asterism of the Sickle is his mane and head. Several bright galaxies lie beneath him, east of Regulus, and can be seen with a telescope. Even more are to be found in 'the Realm of the Galaxies' behind Leo, between Virgo and Coma Berenices. The bright star Arcturus is nearby in Boötes, and Ursa Major, the Great Bear, lies to the north. It contains the asterism of the Plough, whose handle has a middle star which is actually a double named Alcor and Mizar. With binoculars, Mizar is revealed to be a double star itself. The constellations of Lyra and Cygnus rise later in the night, their bright stars Vega and Deneb forming the Summer Triangle with Altair in Aquila.

The Planets


Southern Hemisphere

John Field from the Carter Observatory in New Zealand speaks about the southern hemisphere night sky during April 2011.

Autumn has arrived in the southern hemisphere. Over the last month our daylight hours have continued to get shorter as we passed the autumnal equinox, and will continue to do so until the winter solstice in June. One advantage of the longer night-time hours is that we can start our star-gazing at a more reasonable hour. Low in the west after twilight, the head of Taurus the Bull is visible, marked by the V-shaped cluster called the Hyades, with the bright foreground star Aldeberan marking one of his eyes. The Pleiades Cluster, marking the back of Bull, will be lost in the twilight sky during April. They will not reappear in the morning sky until June, around the time of the southern hemisphere's winter solstice. One of the zodiacal constellations, Taurus, sits along the path of the Sun, the Moon, and the planets as observed from Earth. The Sun will move in front of the background stars of Taurus during a period from the 13th of May to the 21st of June. The less bright of the two eyes, Epsilon Tauri, was found in 2007 to have a planet 7 times the mass of Jupiter with an orbital period of 1.4 Earth years around it.

There are 20 stars brighter than magnitude 5 in our night sky known to have planets orbiting them. A number of these are visible in our southern sky. The neighbouring zodiacal constellation Gemini's second brightest star, Pollux, shining at magnitude 1.15, also hosts a planet estimated at 2.7 times the mass of Jupiter. Only slightly fainter than Pollux is the bright southern star Fomalhaut - 'the Mouth of the Fish' in Arabic - in the constellation Pisces Austranis, the Southern Fish. The star is known to have at least one planet orbiting it. This planet was the first to be directly imaged, by the Hubble Space Telescope in 2008. There is a disc of debris around the star and it is possible that other planets may be forming within the disc.

Gemini is home to the star cluster M35. This open cluster is about the same size as the full Moon and, at magnitude 5.3, should be visible to the unaided eye from a dark location and easily seen with binoculars or a small telescope. The cluster is estimated to be 2800 light years away and consists of over 300 stars covering an area about 24 light years across. Gemini represents the heavenly twins, Castor and Pollux, who travelled with Jason and the Argonauts on their quest to find the Golden Fleece in Greek mythology.

As Taurus sets in the west, our winter constellation, Scorpius, rises in the east. The brightest star in Scorpius is Antares - 'the Rival of Mars' in Greek - shining at magnitude 1. Depending on the list used, it is either the fifteenth- or sixteenth-brightest star in the night sky. Antares is a red supergiant star about 600 light years distant; it has a diameter 800 times that of our Sun and is estimated to be 65,000 times brighter, with a mass up to 18 times greater. Although the core of this star is many times hotter than that of our star, the Sun, the expansion of its atmosphere makes the surface temperature much cooler and gives it a reddish hue. This colour gave rise to its name as the Rival of Mars. Antares is part of a binary star system and the companion, although bright at magnitude 5.5, is difficult to observe due to the brightness of Antares. Normally a telescope greater than 150 mm (6 inches) is needed to observe the companion. But, occasionally, the Moon can occult Antares and this can allow smaller telescopes to observe this star whilst Antares is hidden. Some observers report it as having a green tint, but this due to an optical illusion as the star is actually a blue supergiant. To Māori in Aotearoa (New Zealand), Antares is known as Rehua, and it marks the eye of Te Matau a Māui (the Hook of Māui). The curve of the Scorpion's body and stinger are seen as the curve of the Hook, and the distinctive triangle made by the stinger becomes the tip of the Hook. In Māori mythology this was the hook that Māui, a great hero, used to pull the North Island of New Zealand out of the ocean. The North Island is known as Te Ika a Māui (the Fish of Māui).

The Hook crosses the a wide and bright part of the Milky Way, and it is in this region of the sky that we look toward the centre of our Galaxy, 30,000 light years away. With such a high concentration of stars, this region is a prime area for observing gravitational microlensing events. Microlensing is based on the gravitational lens effect. A massive object (the lens) will bend the light of a bright background object (the source). This can generate multiple distorted, magnified and brightened images of the background source. As the two objects move into alignment, a bell-shaped curve of light intensity with time is formed. If a planet orbits around the lensing star then an additional peak will appear on the curve. A collaborative team of astronomers from New Zealand and Japan are running a microlensing programme at Mount John Observatory above Lake Tekapo in the centre of the South Island of New Zealand. Using a 1.8-metre telescope and a wide-field CCD camera, they study dense regions of the sky on a regular basis to spot the slight change in brightness that may herald a lensing event. Once a potential event is observed, a wide group of amateur and professional astronomers are notified and can follow the light curve. This potentially allows 24 hours' observation of the event and means that the short-period peak of a planet can be observed. To date, planets have been discovered orbiting fourteen stars in Scorpius, but all that stars are fainter than 5th magnitude.

The Planets

Odds and Ends

April is the Global Astronomy Month run by Astronomers without Borders. Events are running throughout the month but highlights include a global star party on April 9 and lunar week running April 10 - 6.

April 12 marks the 50th anniversary of manned space flight. To celebrate, Yuri's Night is a collection of events across the world.

NASA's penultimate shuttle mission is scheduled to launch on the 19th of April. Endeavour will makes it final flight in order to deliver things to the International Space Station, including the Alpha Magnetic Spectrometer, which will look for evidence of unusual types of matter such as antihelium nuclei and theoretical supersymmetric particles called neutralinos.

The annual UK National Astronomy Meeting is being held in Llandudno in North Wales in mid-April. There are public events on the evenings of April 18 (in Welsh) and April 20 (in English).

The new Discovery Centre at the Jodrell Bank Observatory is nearly complete and scheduled to open to the public in mid-April. The staff have been keeping a development diary during the construction period.

Show Credits

News:Megan Argo
Interview:Dr Bob Watson, Liz Guzman and Paul Woods
Interview:Dr Cristobal Espinoza, Liz Guzman and Paul Woods
Interview:Dr Jaime Pineda and Liz Guzman
Interview:Matias Vidal, Liz Guzman and Paul Woods
Night sky:Ian Morison and John Field
Presenters:Adam Avison, Jen Gupta, Liz Guzman and Mark Purver
Editors:Jen Gupta, Megan Argo, Claire Bretherton, Liz Guzman and Mark Purver
Intro/outro script:David Ault
Speedy Gonzales:John Bell
Segment voice:Liz Guzman
Website:Jen Gupta, Mark Purver and Stuart Lowe
Producer:Jen Gupta and Liz Guzman
Cover art:An optical image of the spiral galaxy M104, commonly known as the Sombrero Galaxy, taken in 3 bands with the 1.5 metre Danish telescope at the ESO La Silla Observatory in Chile. Credit: ESO/IDA/Danish 1.5 m/R. Gendler and J.-E. Ovaldsen

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