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October 2011: Dusty

October 2011

In the show this time, we talk to Dr Greg Sloan about evolved stars and dust. As always, Megan rounds up the latest news and we hear what we can see in the October night sky from Ian Morison and John Field.

The News

In the news this month:

Interview with Dr Greg Sloan

Dr Greg Sloan studies the thick dust shells of ejected mass surrounding dying stars. He uses infrared spectra to investigate star mass loss and to understand how the accumulated dust can actively take part in the mass loss of its dying parent star. He has examined galaxies within our 'local' area, which, rather than being similar to our own Milky Way, are in fact closer in chemistry to the primordial Universe. In this interview, he discusses the difference between the Milky Way and our neighbouring galaxies, and we find out what astrophysicists can learn from dust shells and hear about stars dropping out of the visible night sky! Dr Sloan also talks about the data he accumulated from the Spitzer Space Telescope and the possibilities of using ALMA (a topical telescope at the moment) and the Planck satellite for his research.

The Night Sky

Northern Hemisphere

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

The Cygnus Rift, a dark band of dust in the Milky Way, can be seen cutting through the Summer Triangle made up of the stars Deneb, Vega and Altair. Brocchi's Cluster lies between Altair and Vega. In a dark sky, the constellation of Delphinus, the Dolphin, can be seen below and left of Cygnus the Swan, with the tiny constellation of Sagitta, the Arrow, above it. The planetary nebula known as the Dumbbell Nebula can be seen through binoculars or a small telescope above the tip of the Arrow. The Square of Pegasus is to the east, from which the Andromeda Galaxy can be located with binoculars or, if it is very dark, with the naked eye. The Triangulum Galaxy can also found nearby using binoculars. Further east, Taurus rises late in the evening, containing the Pleiades Cluster. The Double Cluster can be seen with the naked eye in Perseus, below the 'w' of Cassiopeia which sits almost overhead. Two distinct star clusters can be made out with binoculars. Orion the Hunter rises after midnight BST (British Summer Time, one hour ahead of Greenwich Mean Time), allowing the Orion Nebula to be seen below his famous Belt.

The Planets

Highlights

Southern Hemisphere

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

The constellations of Scorpius and Sagittarius lie in the west. The planets Mercury and Venus are below them, appearing close together at sunset at the end of the month. In a dark sky, the Zodiacal Light may be visible after twilight as a faint, broad column of light. It is the reflection of sunlight off meteoric dust in the plane of the Solar System, hence its presence in the zodiacal constellations through which the ecliptic plane passes. Jupiter rises in the east after sunset and is high in the northern sky by midnight. The planet's four largest moons can be seen through binoculars or a telescope, and move from night to night, sometimes disappearing behind or in front of their host. Canopus is the brightest star in the evening sky this month, climbing in the south as the evening progresses. It is later outshone by the brightest of all night-time stars in our sky, Sirius, which rises in the east after midnight. While Sirius is much closer to us than Canopus, Canopus is intrinsically far more luminous, shining some 13,000 more intensely than our Sun. The third-brightest star in the sky, Alpha Centauri, will also be visible, near the Milky Way. The constellation of Crux, the Southern Cross, skirts the southern horizon from west to east during the night but does not set, while the four stars forming the Great Square of Pegasus rise and move across the northern sky from east to west before setting again. The triple star Epsilon Pegasi is not in the Square but is the brightest star of the Pegasus constellation, and consists of a yellow supergiant at magnitude +2.9 (visible with the naked eye), a blue companion at magnitude +8 (visible using binoculars) and a further companion at magnitude +11 (visible through a telescope). Nearby is the globular cluster M15 at magnitude +6, with a bright centre and fainter rays scattering from its core. A larger telescope reveals a planetary nebula within the cluster. The constellation of Cetus, the Whale, is near to Aquarius, the Water Carrier, and Eridanus, the River. It is near to the edge of the ecliptic plane and planets sometimes move briefly through it. The asteroid Vesta was discovered there in 1807. Alpha Ceti, or Menkar (the Nose), is a red giant star of magnitude +2.5. Binoculars show an unconnected blue star of magnitude +5.6 nearby. Beta Ceti, or Deneb Kaitos (the Whale's Tail), is the constellation's brightest star, a yellow giant of magnitude +2.0. Gamma Ceti, or Kaffaljidhma, is a double star comprising individual stars of magnitudes +3.7 and +6.4. Omicron Ceti, or Mira, is a red star whose variable brightness was recognised by the Dutch astronomer David Fabricius in 1596. It swells and contracts with a period of between 320 and 370 days, giving it a magnitude range of +3 to +9. To the naked eye, this makes it appear and disappear over the course of a year. The flare star UV Ceti is a red dwarf star which undergoes sudden increases in brightness lasting only a few minutes, taking it from magnitude +13 to +7. Tau Ceti, at 11 light-years away, is the closest Sun-like star to our Solar System. It has a debris disc which may one day coalesce into planets.

Odds and Ends

The first part of the Chinese space station Tiangong 1 was launched on September 29.

NASA announced the beginning of development of the Space Launch System, an advanced heavy-lift launch vehicle that will provide an entirely new national capability for human exploration beyond Earth's orbit. The project will take advantage of technologies developed from the Space Shuttle Program and the Constellation Program. The first developmental flight, or mission, is targeted for the end of 2017.

October 4 - 10 is World Space Week.

At the end of September, the aurora was spotted in the south of England (photos tweeted by @scienceoxford). A spectacular display of the southern lights (aurora australis) was also snapped by astronauts on board the ISS.

New observations by NASA's Wide-field Infrared Survey Explorer (WISE) exonerate the family of asteroids some believed was responsible for the demise of the dinosaurs. The age of this asteroid family, remnants of a collision between giant asteroid Baptistina with another object in the main belt between Mars and Jupiter, was originally estimated to be about 160 million years ago. The debris of this collision would then have been reaching Earth about 80 million years ago, around the time dinosaurs disappeared. This age estimate, which was obtained by looking at the light reflected by the asteroid, has been revised by WISE, which uses direct infrared observation of the asteroids to determine their age. According to WISE, the original Baptistina asteroid actually broke up closer to 80 million years ago, meaning that the debris did not reach Earth in time to be the culprit in the extinction of dinosaurs.

Show Credits

News:Megan Argo
Interview:Dr Greg Sloan, Mel Irfan and Mark Purver
Night sky:Ian Morison and John Field
Presenters:Melanie Gendre and Jen Gupta
Editors:Adam Avison, Megan Argo, Claire Bretherton, Mel Irfan and Mark Purver
Segment Voice:Liz Guzman
Website:Jen Gupta and Stuart Lowe
Producer:Jen Gupta
Cover art:The Large Magellanic Cloud in the infrared. CREDIT:: NASA/JPL-Caltech/M. Meixner (STScI) & the SAGE Legacy Team

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