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June 2011: Spirit

June 2011

In the show this time we have interviews about dark matter and evolved stars from the National Astronomy Meeting. Megan rounds up the latest news and we hear what we can see in the June night sky from Ian Morison and John Field.

The News

In the news this month:

National Astronomy Meeting

The annual National Astronomy Meeting was held in mid-April in Llandudno, north Wales. In this show we have three more interviews recorded at the conference.

Interview with Professor Gianfranco Bertone

Professor Gianfranco Bertone is a member of the Theoretical Physics group of the Institut d'Astrophysique de Paris, currently visiting the Institute for Theoretical Physics of the University of Zurich. In this interview, Professor Bertone talks about dark matter and various ways of detecting it, including direct detection techniques with the Large Hadron Collider (LHC).

Interview with Professor Mike Edmunds

Professor Mike Edmunds of Cardiff University studies dust and the chemical evolution of galaxies, and also leads a project investigating the Antikythera Mechanism. Here he discusses the unsolved mysteries of stars in the later stages of their lives. Although the outline of stellar evolution is understood, the finer details are important for an understanding the role of stars in dictating the chemistry of the Universe. Professor Edmunds talks about the advances in observational instrumentation and computer modelling that are allowing astronomers to uncover the more subtle aspects of stars' lives, which in turn underpin our picture of galactic evolution. His particular interest at the National Astronomy Meeting was the apparent over-abundance of intstellar dust in the early Universe, as determined from its absorption and chemical spectra. Since dust is often thought to be released by supernovae, how can so much have been created so early on? He speculates that giant stars may produce the initial grains during their later life, before they explode as supernovae.

Interview with Dr Rob Izzard

Dr Rob Izzard is an astrophysicist in the Stellar Astrophysics group at the Argelander Institute for Astronomy, part of the University of Bonn. Here he tells us about barium (Ba) stars, giant stars that are in binary systems and have very strong barium lines in their spectra. He and his group have been trying to model the orbits of the two stars and other dynamics of the system.

The Night Sky

Northern Hemisphere

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

As it gets dark - around 10pm in northern England - Leo is setting in the west. Ursa Major lies above and contains the stars Merak and Dubhe, which are aligned with Polaris, the North Star. It also includes the asterism of the Plough, the middle star of whose handle is actually a double, Mizar and Alcor, which can be resolved with the naked eye. Using a telescope, Mizar itself can be seen to be a double, and the entire system is now known to consist of six stars. Looking down and left from Leo, Virgo is in the south-west, and the planet Saturn currently resides there. Above it is Arcturus in the constellation of Boötes. Up and to the left of this is the arclet of stars known as Corona Borealis, the Northern Crown. Cygnus the Swan, Lyra the Lyre and Aquila the Eagle rise in the east around sunset. Their three brightest stars - Deneb, Vega and Altair respectively - mark out the Summer Triangle. Between Vega and Arcturus is the constellation Hercules, whose four brightest stars make up the quadrilateral shape of the Keystone. Binoculars or a telescope reveal the globular cluster M13 about two thirds of the way up its right-hand side. A spherical mass of up to a million stars almost as old as the Galaxy itself (and not much younger than the Universe), it is the most visible globular cluster in the northern hemisphere. The less prominent globular cluster M92 is above and left of M13. In Cygnus, Albireo is the head of the Swan, and a telescope shows that the main orange star is accompanied by a dimmer, bluer partner. The brighter star is orange because it has finished its main hydrogen-burning phase and become a giant. To the lower left of Cygnus is the small, diamond-shaped constellation of Delphinus, the Dolphin.

The Planets

Highlights

Southern Hemisphere

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

The southern hemisphere is in the grip of winter, with long nights allowing over 15 hours of observing per day in some locations. This means that some stars which set in the evening can be seen rising again the morning. The 22nd of June marks the winter solstice, and the dawn rising of the Matariki (Pleiades Cluster) and Puanga (the star Rigel in Orion) were used by Māori in some parts of New Zealand to mark the changing of the year in the calendar, Te Maramataka. Scorpius, the Scorpion, dominates the south-eastern sky, followed by Sagittarius, the Archer. Scorpius is marked by the red giant star Antares - the Rival of Mars - which is around 600 light-years away and is the sixteenth-brightest star in the night sky. It is about 800 times larger in diameter than our Sun, and intrinsically 10,000 times brighter. It has a fainter companion, but a medium-sized telescope is needed to distinguish it from the glare of Antares. Scorpius is seen as a fishing hook by Māori and many Polynesian cultures, and Antares is known to some Māori as Rehua, marking the eye of the hook. The Milky Way passes through Scorpius, so the constellation is host to a number of star clusters and nebulae which are easily observed. Near to Antares is the bright globular cluster M4, which is one of the closest to us at a distance of 7200 light-years. Observations with the Hubble Space Telescope in 1995 showed that some of its stars are among the oldest in our Galaxy, formed around 13 billion years ago. The faint globular cluster NGC 6144 is also near Antares, and long-exposure photographs of the region around the star reveal tendrils of dark material and glowing nebulosity. A number of double stars under the body of Scorpius can be observed with the unaided eye, binoculars or a telescope. NGC 6231. is a naked-eye star cluster near the stinger of the Scorpion, similar in size to the Pleiades but much more distant at 6000 light-years away. Another open cluster, M7, appears below the stinger as a haze to the eye but can be easily made out with binoculars or a wide-field telescope. The Butterfly Cluster, M6, is nearby but fainter, and is 1300 light-years away. Binoculars can also be used to observe M21, M23, NGC 6167 and NGC 6193.

The spectacular Lagoon and Trifid Nebulae reside in Sagittarius, along with many globular clusters. The Lagoon Nebula, M8, appears as a compact cluster of stars surrounded by a circle of nebulosity with a dark rift. It contains a number of dark globules that are protostars, and is one of the few star-forming nebulae visible to the unaided eye, at a distance of 4000-6000 light-years. The Trifid Nebula, M20, is a smaller region of nebulosity close by, and a telescope of at least 200mm in aperture allows dark lanes to be discerned. Long-exposure photographs show that it consists of red emission and blue reflected light. It is 7600 light-years away and shines at magnitude +6.3. Sagittarius is a centaur in Babylonian mythology, but its brightest stars form an asterism called the Teapot. Lambda Sagitarii marks its top, and nearby are the globular clusters M22 and M28. M22 is one of the brightest in the sky, at magnitude +6, as well as being one of the closest and largest in our Galaxy. Charles Messier did not observe individual stars in it; William Herschel was the first to do so, and you can do the same using a small telescope. It would be brighter, but for the quantity of intervening interstellar dust between it and the Earth. Sagittarius contains a wealth of other clusters: M23 is an open cluster of over 100 stars forming curving arcs and chains, 2000 light-years away; M24 is a bright region of stars known as the Sagittarius Star Cloud, which includes a number of dark nebulae; M25 is a bright open cluster, 2000 light-years away, containing a number of deep yellow stars; M55 is a globular cluster of magnitude +7.4, 16,000 light years away, which was discovered in the 18th century - along with many others - as telescopes became larger. The north-eastern part of Sagittarius is also home to a much more distant object: Barnard's Galaxy, NGC 6822, an irregular dwarf galaxy that is best viewed through a wide-field telescope. The Milky Way is at its brightest, widest and densest in Sagittarius, and has been seen variously as a river, a sky road and a bridge between the Heavens and the Earth. To ancient Arabs it was Al Nahr - the river - and it is the River of Heaven (Tien Ho) to the Chinese. The Māori called it Te Ika Roa, the Long Fish. Today we know that is the plane of our own Galaxy, and that the region of Sagittarius is in the direction of the Galactic Centre, some 30,000 light-years away. Astronomers have determined that the stars in the very centre - a region known as Sagittarius A* - are orbiting a supermassive black hole around 3 million times the mass of the Sun.

The Planets

Highlights

Odds and Ends

On May 25, NASA sent its last transmission to the Mars rover Spirit, ending attempts to make contact with the rover which last sent a communication in March 2010. Spirit has been on Mars since January 2004 but became stuck in May 2009. While it continued to take data from its stationary position, it is unlikely that the rover survived the Martian winter.

The Atacama Large Millimetre/sub-mm Array (ALMA) is growing all the time on its way to becoming a 66 antenna interferometer. In the past two months the first European built 12-m antenna was handed over to the observatory, as was the first of the Japanese built 7-m antennae. ALMA will begin its Early Science observations at the end of this year using a total of 16 12-m antennae located 5000m above sea-level in the Atacama Desert in Chile. For more on ALMA see the Feb Extra show.

An evening astronomy event is being held at the Museum of Science and Industry in Manchester on June 15 to conincide with the lunar eclipse. See the MOSI website for more details.

Show Credits

News:Megan Argo
Interview:Professor Gianfranco Bertone and Melanie Gendre
Interview:Professor Mike Edmunds and Mark Purver
Interview:Dr Rob Izzard and Liz Guzman
Night sky:Ian Morison and John Field
Presenters:Adam Avison, Jen Gupta, Leo Huckvale and Libby Jones
Editors:Adam Avison, Megan Argo, Claire Bretherton, Melanie Gendre, Liz Guzman and Mark Purver
Intro/outro:Professor Martin Rees
Segment Voice:Liz Guzman
Website:Jen Gupta, Mark Purver and Stuart Lowe
Producer:Jen Gupta
Cover art:Last panorama taken by the Spirit rover on Mars. CREDIT:: Marco Di Lorenzo, Kenneth Kremer, NASA/JPL/Cornell

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