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March 2011: Llama

March 2011

In the show this time we find out about quasars from Dr Alejo Martinez-Sansigre, and Dr Alastair Edge tells us about the gas between clusters of galaxies. Megan rounds up the latest news and we hear what we can see in the March night sky from Ian Morison and John Field.

The News

Interview with Dr Alejo Martinez-Sansigre

Dr Alejo Martinez-Sansigre (Institute of Cosmology and Gravitation at the University of Portsmouth) tells us about quasars, the most luminous objects in the universe. In this interview, Alejo explains exactly what a quasar is and why they are more common in the early universe.

Interview with Dr Alastair Edge

Dr Alastair Edge (Durham University) is an extragalactic astronomer researching the gas between clusters of galaxies from an X-ray perspective. In this interview, Alastair explains how this hot gas made its way into the intracluster medium, and discusses how ALMA can be used to detect and study this gas and its role in active galactic nuclei feedback.

The Night Sky

Northern Hemisphere

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

Constellations such as Orion and Taurus become visible as the Sun sets, but are themselves beginning to set in the west. Other constellations are more easily seen now, such as Gemini, the Twins. Gemini is up and to the left of Orion, in the south-west in the mid-evening. Its two main stars are Castor and Pollux. Looking to the feet of the uppermost twin, which has Castor at its head, the open cluster M35 can be seen to the right using binoculars. Moving east, Cancer, the Crab, lies in a relatively empty patch of sky. At its heart is the wide open cluster M44, known as the Beehive Cluster or Praesepe. Continuing in the same direction leads to the Sickle, an asterism forming the head of the constellation of Leo, the Lion. Its brightest star is Regulus, or Alpha Leonis, part of its front knees. Denebola marks the Lion's tail. Moving horizontally from Regulus, a small telescope allows a number of galaxies to be seen: M95, M96 and, further over, M65 and M66. Virgo rises to the lower left of Leo in the evening, with its brightest star Spica, or Alpha Virginis. Between Leo and Virgo, beneath the small constellation of Coma Berenices, lies the "Realm of the Galaxies", which is in the direction of the Virgo Cluster. Comprising over 1000 galaxies, this cluster is home to a number of the galaxies in the Messier Catalogue, which are visible through a small telescope in a clear sky. Ursa Major, the Great Bear, makes its best appearance at this time of year, high overhead. Within this is the asterism of the Plough, or Big Dipper (named after the soup ladle used on farms in North America). The line between the rightmost two stars of the Plough, from Merak up to Dubhe, points towards Polaris, the Pole Star or Northern Star. Alcor and Mizar are in the centre of the Plough's handle, a multiple star system that can just be discerned as two objects with the naked eye. A small telescope shows that Mizar is itself a double star, and a redder companion star can also be seen.

The Planets


Southern Hemisphere

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

March sees our summer constellations of Taurus, Orion and Gemini sliding towards the western sky a little more each night. Our nights are quickly becoming longer and this means the opportunity for more observing! In the west the Pleiades/Matariki set earlier each evening and will soon be lost in the twilight, returning, in our morning sky, at the time of our winter solstice. One version of the Waka of Tamarereti has the Pleiades forming the carved prow of a Māori canoe, the 'V' of stars in Taurus forming the sail and Orion's Belt and Sword forming the stern and carved stern-post of the canoe. This was the canoe in which Tamarereti sailed across the heavens placing Nga Whetu - the stars - across the heavens. The 'V'-shaped head of Taurus consists of the more distant Hyades Cluster, which contains the half-sisters of the Pleiades, along with the much closer and brighter star Aldeberan, which forms one of the Bull's eyes. The name Aldebaran originates from the Arabic for "the follower", as this star follows the Pleiades across the sky. Aldebaran has a distinct orange hue and is a K5 type star that is 65 light years away and 150 times brighter than the Sun. It has used up the hydrogen fuel in its core and is now fusing hydrogen in a shell around the core. The star's radius has increased to 44 times that of the Sun, and as a result has a cooler surface temperature of around 4000 degrees Celsius. The spectral type of a star is based on its spectral lines and temperatures. Today they fall into the following sequence: O,B,A,F,G,K, M (going from hottest to coolest). The moniker "Oh Be A Fine Guy/Girl Kiss Me" is often used to remember it.

Sirius, the brightest star in the sky, is an A type star, while our Sun is a G type and Proxima Centauri, the closest star to our Solar System, is a faint M type red dwarf. Aldebaran is slightly variable in brightness, but the change is imperceptible to the human eye. It is also one of the few very bright stars that can be occulted (hidden) by the Moon. One of these events was observed from Athens in 509, and during his tenure in the 1700s Astronomer Royal Edmond Halley realised that Alderbaran could not have remained in the same position for this to have happened. This meant that Alderbaran must have moved over the intervening 1200 years by one quarter the diameter of the Moon. Halley went onto discover that a number of other stars had also moved in their positions over recorded history. This shifting of star positions is due to the fact that all the stars, including the Sun, are moving in their orbits around the Galaxy. The nearby stars show the greatest amount of angular movement. Every 50 years, updated star atlas are released to account for this motion. From our Solar System, we see, over many millennia, the shifting of the stars. The constellations we see today will look very different in one hundred thousand or a million years time.

The Hyades Cluster is about 150 light years distant and consists of at least 130 stars brighter than 9th magnitude. It also contains a number of double, or multiple, stars. It has used up or lost the interstellar material from which it formed, and now travels as a loose open cluster that is estimated to be 700 million years old. Almost due north is the zodiacal constellation of Cancer, the Crab, which appears as four stars with the Beehive Cluster at the centre. Rising up in the eastern evening sky is the planet Saturn, appearing as a bright yellow 'star' in the constellation of Virgo. Through a telescope, the rings will appear as a thin disc around the planet as the rings are almost edge-on to us.

In the southern sky, the Cross and the star Achernar appear opposite each other and about halfway up the sky. The midway point between the two marks the South Celestial Pole. A third of the way back from Achernar we find the two Magellanic Clouds, two dwarf galaxies orbiting the Milky Way. There are 14 known dwarf galaxies that orbit our Galaxy. It is thought that suc galaxies are formed during the birth of their parent galaxy or following interactions with other large galaxies. The tidal forces in these interactions stimulate the collapse of material in the halo of galaxy and this leads to dwarf galaxies forming. One of the local dwarf galaxies is located in the constellation of Canis Major, about 25000 light years from our Solar System. It is being torn apart by the gravitational pull of the Milky Way. Recent studies of the globular clusters M79, NGC 1851 and NGC 2808 suggest they may have been 'stolen' from this dwarf galaxy. Another disrupted dwarf galaxy was discovered by a team led by New Zealander Mary Williams. This galaxy is in the direction of the constellation of Aquarius. The region with the greatest number of globular clusters is the Scorpius/Sagittarius region which rises after midnight.

For those up in the early morning, the planet Venus rises in the east around 04:00 NZDT (New Zealand Daylight Time) in New Zealand. On the 1st of March the crescent Moon is close to Venus. Mercury, Mars and Jupiter are too close to the Sun to be observed.

Odds and Ends

Recently there has been speculation from two scientists from the University of Louisiana about the existence of a ninth planet called Tyche in the far reaches of our solar system, on the outer edge of the Oort Cloud. According to John Matese and Daniel Whitmire, the presence of a planet with up to four times the mass of Jupiter, would explain the odd behaviour of some comets in that region. Whilst the planet has yet to be observed, it is believed that evidence for its existence could be found by the NASA space telescope, WISE, which will release its data some time in April.

The Stardust spacecraft successfully flew by Comet Tempel-1 in early February 2011, and researchers are extremely pleased with the results. The mission principle investigator was even quoted saying that it was "1000 percent successful!". The comet had previously been imaged by the Deep Impact spacecraft in 2005, which also flung a probe into the nucleus. This time, scientists have been to observe the resulting impact crater and learn about the composition of the comet. Other scientific goals included identifying changes since Tempel-1 looped around the Sun, imaging areas not previously seen before, and analysing the dust and debris surrounding the comet.

With the ramping up of solar activity towards the solar maximum in 2013 there will be an increase in solar flares and coronal mass ejections caused by the sudden release of magnetic energy stored in the Sun's atmosphere. The waves of charged particles interact with the Earth's magnetic field and could result in the northern lights (Aurora Borealis) being visible in northern parts of the UK. Space Physicists at Lancaster University have set up email alerts and a twitter account @aurorawatchuk to keep you updated on when the aurora may be visible from the UK.

Show Credits

News:Megan Argo
Interview:Dr Alejo Martinez-Sansigre and Libby Jones
Interview:Dr Alastair Edge, Libby Jones and Mark Purver
Night sky:Ian Morison and John Field
Presenters:Melanie Gendre, Jen Gupta, Scot Hickinbottom and Libby Jones
Editors:Mark Purver, Megan Argo, Claire Bretherton, Melanie Gendre and Cat McGuire
Intro/outro:Brian Cox
Segment voice:Lizette Ramirez
Website:Libby Jones and Stuart Lowe
Producer:Libby Jones
Cover art:Composite image of the Hydra A galaxy cluster showing hot gas in X-ray (blue), radio jets (pink) and galaxies in the cluster in optical (yellow). Credit: NASA/CXC/U.Waterloo/C.Kirkpatrick et al./NSF/NRAO/VLA/CFH-Telescope/DSS

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