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September 2012: Tranquility

September 2012

In the show this time, we have more interviews from the National Astronomy Meeting as Dr Simon Green tells us about collecting cometary dust with the Stardust-NExT mission and Dr Joseph Mottram talks about massive star formation. Stuart brings us the latest astronomy news and we find out about the September night sky from Ian Morison and John Field.

The News

In the news this month:

Interview with Dr Simon Green

Dr. Simon Green of the Open University is a member of the Stardust-NExT mission. Stardust collected samples of cometary dust during its close flyby of Comet Wild 2 in January 2004. Stardust-NExT is a follow-on mission for Stardust, in which it completed a flyby of comet Tempel-1 on the 14th of February 2011 to observe the crater left over from the Deep Impact mission.

Interview with Dr Joseph Mottram

Dr. Joseph Mottram from Leiden Observatory talks to us about massive star formation and how this differs from the formation of low- and intermediate-mass stars. He discusses the time scales of formation for stars and stellar clusters.

The Night Sky

Northern Hemisphere

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

As the nights lengthen, the turning of the year moves the stars eastward so they are seen earlier in the evening, resulting in a similar sky just after sunset for much of the month. Hercules is setting in the west after dark. Its four brightest stars comprise the Keystone, and about two thirds of the way up the right-hand side is the globular cluster M13. The Summer Triangle, consisting of the stars Vega, Deneb and Altair, dominates the southern sky. About a third of the way from Altair towards Vega lies the Cygnus Rift, a dark region containing the asterism Brocchi's Cluster. Up and to the left of this is Albireo, the faintest of the four stars making up the Northern Cross within Cygnus. It is a double star, and a telescope will show the two stars to be respectively golden and turquoise in colour. The tiny constellation of Delphinus, the Dolphin, is down and to the left of Cygnus. Pegasus, much larger, is over in the east, with Andromeda up to its left. Andromeda gives its name to both a constellation and our nearest neighbouring large galaxy, which lies beyond the stars in the same direction. You can find the Andromeda Galaxy by 'star-hopping': start at Alpheratz, the top-left-hand star in the Square of Pegasus, then go one bright star to the left and fork right to the next bright star. Go sharp right to the next bright star, then continue onwards the same distance again, and you should find the fuzzy glow of Andromeda using binoculars. In a very dark sky, it can be seen with the unaided eye. The W-shape of Cassiopeia is above Andromeda. Meanwhile, Perseus is rising in the east. In between Cassiopeia and Perseus, a pair of open star clusters called the Perseus Double Cluster lies on the Milky Way.

The Planets


Southern Hemisphere

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

At the spring equinox on the 23rd, day and night are of approximately equal length. The constellations of Scorpius and Sagittarius are in the west after sunset. The red giant Antares, the Scorpion's Heart, is the brightest star in Scorpius. Eventually, it will exhaust its fuel and collapse under its own gravity, exploding in a supernova and leaving behind a neutron star or black hole, as well as scattering heavy elements into space. In Māori star lore, the line of stars from Antares to the Scorpion's tail is called Te Matau a Maui - the Hook of Maui. The Milky Way is broad and bright in this part of the sky, because we are looking towards to centre of the Galaxy. Clouds of interstellar dust make dark patches in the Milky Way and obscure the Galactic centre. They consist of ancient hydrogen and helium, as well as heavy elements produced by stars, and some will form new stars and planets one day. At the right-angle in the Scorpion's tail lies the open star cluster NGC 6231, with seven relatively bright stars. The cluster M7 is visible with the naked eye to the right of the tail, and is beautiful when viewed through binoculars or a telescope. M6, the Butterfly Cluster, is nearby but is fainter. Long-exposure photographs will reveal the colours and details of a number of star clusters in this region, along with nebulae and the Milky Way itself. Sagittarius, the Archer, is also sometimes called the Teapot, and the centre of our Galaxy lies below its spout. Infrared telescopes allow astronomers to see through the dust to the stars in the centre, whose orbits give away the presence of a black hole of over 4 million times the mass of the Sun. Below Sagittarius is M8, the Lagoon Nebula. It is a cloud of gas heated by young stars and containing dark dust lanes. Not far away is M20, the Trifid Nebula, a bright cloud dissected by three dark lines. As well as nebulae and open star clusters, this region of the sky contains globular clusters, which look like fuzzy spots. These collections of old stars are relics of the early ages of galaxies.

The Corona Australis, or Southern Crown, is near to Sagittarius. Travelling down the Milky Way towards the northern horizon, we reach Cygnus the Swan, a large cross-shaped constellation. Its brightest star, Deneb, marks the tail. Above and to the right is Aquila, the brightest star in Altair, while to its left is Vega, Lyra's brightest star and the fifth-brightest in the night sky. The three form the Winter Triangle for those in the southern hemisphere - the Summer Triangle for those in the north. By midnight NZST (New Zealand Standard Time, 12 hours ahead of Universal Time), Orion the Hunter and Canis Major, the larger of his dogs, are rising in the east as Scorpius and Sagittarius set in the west.

The Planets


Odds and Ends

Neil Armstrong, the first person to walk on the Moon, died on the 25th of August. Jodrell Bank recorded signals from Apollo 11's Eagle lander during its descent to the Moon in 1969, and were able to measure its velocity using the Doppler shift in the frequency of the signal. The graph, produced using a 50-foot radio dish, shows where Neil Armstrong took manual control before landing. His family suggest that people give him a wink in tribute the next time they look up at the Moon.

Palaeontologists have uncovered dinosaur footprints in the unlikely location of the grounds of NASA's Goddard Space Flight Center. In a place where futuristic spacecraft are now developed, two nodosaurs walked 110 million years ago, and they may have been a mother and baby.

Show Credits

News:Stuart Harper
Interview:Dr Simon Green and Libby Jones
Interview:Dr Joseph Mottram and Libby Jones
Night sky:Ian Morison and John Field
Presenters:Libby Jones and Mark Purver
Editors:Mark Purver, Claire Bretherton, Liz Guzman and Christina Smith
Segment Voice:Cormac Purcell
Website:Mark Purver and Stuart Lowe
Producer:Mark Purver
Cover art:Neil Armstrong, photographed on the surface of the Moon by Buzz Aldrin. CREDIT: NASA

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