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November 2012: Gigapixel

November 2012

In the show this time, Dr Martin Stringer talks to Liz about the principles of supernova driven winds. Ian Morison and John Field tell us what not to miss in the November night sky and Megan gives us a round up of the latest astronomy news.

The News

In the news this month:

Interview with Dr Martin Stringer

Dr Martin Stringer from the l'Observatoire de Paris talks about supernova driven winds. He explains how to calculate the energy produced by these winds and what affect this energy has on the galaxies in which they occur. He also describes and compares the analytical and numerical approaches he and his collaborators have used to simulate these winds. They find that while analytical analysis will give the general properties of all of the supernova driven winds in a galaxy, numerical simulations are sensitive enough to resolve individual supernovae.

The Night Sky

Northern Hemisphere

Ian Morison tells us what we can see in the northern hemisphere night sky during November 2012.

The summer triangle of Deneb in Cygnus, Vega in Lyra and Altair in Aquila is still visible in the west after sunset. Pegasus, the Winged Horse, is upside-down and high in the south. The number of stars visible within the four stars making up the Square of Pegasus is a good test of the darkness of the night sky, with more than 5 being reasonable. Pisces is below Pegasus, while Andromeda is up to the left, and the Andromeda and Triangulum galaxies can be located in this region by 'star-hopping'. Cassiopeia is almost overhead, while Perseus is lower to the east. The Double Cluster is a nice feature to spot along the Milky Way between these two constellations, and can be seen using binoculars or a small telescope. Algol, the Demon Star, is an occulting binary star in Perseus whose brightness varies every few days as a result of its eclipses. Auriga, also along the Milky Way, rises in the east and contains the bright star Capella, as well as a number of open star clusters which can be seen through binoculars. One of our nearest open clusters, the Pleiades, is in Taurus, as is the very nearest, the Hyades. Aldebaran, the brightest star in Taurus, appears to be in this cluster but is actually much closer to us. The planet Jupiter is also moving across the cluster this month. Orion rises later in the evening, with the three stars of his Belt pointing down towards Sirius, the brightest star in the night sky. The Orion Nebula is a fuzzy glow beneath the Belt, and is a region in which stars are being formed. Gemini rises just to the north of Orion, with its bright stars Castor and Pollux, the Twins.

The Planets


Southern Hemisphere

John Field from the Carter Observatory in New Zealand speaks about the southern hemisphere night sky during November 2012.

The winter constellations of Scorpius and Sagittarius are disappearing in the twilight sky, heralding the approach of summer. Early in the month, the planet Mercury is below the star Antares in the west, but by the middle of the month it sets with the Sun and can no longer be seen. Mars is higher up in Ophiuchus, the Serpent Bearer, a constellation which is sometimes called 'the Coffin' due to the shape made by its brightest stars. The globular clusters M10 and M12 lie within 3° of each other in Ophiuchus. With respective magnitudes of +6.4 and +7.6, they are visible in binoculars, although spotting M12 requires a dark sky.

On the opposite side of the sky, Taurus, Orion and Canis Major are rising in the east during the evening, and these summer constellations will become visible earlier as the month progresses. Sirius, Canopus and Alpha Centauri, the three brightest stars in the night sky, skirt the southern horizon. Sirius, to the east, marks the top of Canis Major, the Large Dog, which is inverted in the southern hemisphere sky. Taurus and Orion lie to the its north-east. The face of Taurus is outlined by the V-shaped asterism known as the Hyades Cluster. In Greek mythology, the Hyades were five daughters of Atlas whose half-sisters were the Pleiades, and so the Pleiades star cluster is nearby. The orange star Aldebaran - 'the Follower' in Arabic, in reference to the way it follows the Pleiades across the sky - is the brightest star among the Hyades, but is not actually part of the cluster as it lies much closer to us. The Horns of Taurus extend down towards the northern horizon, and the planet Jupiter sits between them, rising high in the sky by midnight. Jupiter will be at its closest point to Earth around the time of its opposition (furthest point from the Sun in the sky) in December, so it will be at its brightest in this part of the year. Binoculars and small telescopes reveal its four brightest moons, which change position relative to the planet from night to night. M1, the Crab Nebula, is near the fainter of the two horn tips, and is an expanding cloud of gas and dust created when a star exploded in a supernova - an event recorded in the year 1054. Visible as a dim haze through binoculars, the Crab Nebula shows shape and detail to telescopes of over 100mm in aperture size. The Pleiades Cluster, by constrast, is a group of blue stars which are significant to many cultures, being variously named the Seven Sisters, Matariki and Subaru in different parts of the World. At around 100 million years old, its stars are comparatively youthful. The planets pass through or near to the Pleiades as it lies along the ecliptic.

East of Taurus is Orion, upside-down, with three aligned stars marking his Belt and a fainter line of stars forming his Sword. A faint haze in the Sword is visible to the naked eye and is called the Great Nebula in Orion, a vast star-forming region. Binoculars and small telescopes reveal some detail, while larger telescopes show tendrils of gas. The Belt and Sword make up the asterism known in the southern hemisphere as the Pot or the Saucepan, while the Māori call the Belt 'Tautoru'. Further south, Canopus is beside the Milky Way, with Alpha Centauri further along still. Alpha and Beta Centauri points towards Crux, the Southern Cross, a diamond-shaped constellation which appears in the south-west after sunset. With a declination of -60°, Crux never sets over New Zealand, but dips towards the southern horizon before ascending again in the south-east after midnight. Nearby are the similarly shaped asterisms of the Diamond Cross and the False Cross.


Odds and Ends

With solar maximum approaching next year, you can check the three-day aurora forecast and find out whether the northern lights are likely to be visible in your area. The information is based on observations of solar activity and the strength of the solar wind at the Earth. Viewers looking for the southern lights can get updates from the Australian government's Ionospheric Prediction Service.

Astrobiologists have found that an exoplanet's capacity to sustain microbial life could be evaluated using its colour. By filtering the recieved light into different colour bands and plotting the colour intensities against each other, it would be possible to distinguish planets with surfaces favourable to 'extremophile' bacteria such as rock, snow or water. Planets flagged in this way could then be followed up with precise spectroscopic measurements.

The European Southern Observatory (ESO) has released one of the biggest-ever astronomical images, weighing in at a whopping 9 gigapixels. The image was created by stitching together thousands of smaller images taken in the infrared by the VISTA telescope at the Paranal observatory in Chile. Click here to access the original, zoomable image on the ESO website.

Researchers at the Centre for Astrophysics in Cambridge Massachusetts have discovered spiral arms at the centre of the elliptical galaxy Centaurus A, which is thought to have swallowed a spiral galaxy about 300million years ago. Although Centaurus A is the first elliptical galaxy found to have spiral arms, the advent of more sensitive technologies, such as the Atacama Large Millimetre Array (ALMA), may result in the discovery of many more.

Show Credits

News:Megan Argo
Interview:Dr Martin Stringer and Liz Guzman
Night sky:Ian Morison and John Field
Presenters:Cat McGuire, Indy Leclercq and Mark Purver
Editors:Dan Thornton, Megan Argo, Liz Guzman, Cat McGuire and Mark Purver
Segment Voice:Cormac Purcell
Website:Cat McGuire and Stuart Lowe
Producer:Cat McGuire
Cover art:VISTA gigapixel mosaic of the central parts of the Milky Way. CREDIT: ESO/VVV Consortium

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