In the show we have an interview with John Sarkissian about the Parkes Radio Telescope in Australia. As ever we have the latest astronomical news, what you can see in the November night sky, and your feedback.
In the news this month: shaping the heliosphere, a record-breaking distant cluster, and another impressive exoplanet haul from HARPS
- Solar physicists thought they knew the shape of the Sun's heliosphere, but new results from the Interstellar Boundary Explorer have revealed a huge ribbon of intense emission that was completely unexpected. The space between stars is not empty, but filled with a very tenuous gas known as the interstellar medium. As the Sun moves through this gas it emits a fast moving plasma know as the solar wind. These charged particles spread out spherically creating the heliosphere, a cavity in the interstellar medium swept out by the solar wind.
Launched in October 2008, the Interstellar Boundary Explorer, IBEX, was designed to investigate the nature of the interactions between this solar wind and the interstellar medium at the edge of the solar system where the wind hits the ISM and slows down in a termination shock at what is known as the interstellar boundary. This boundary region emits no light so it cannot be detected by conventional telescopes. Models predicted that the shape of the heliosphere resembled a comet, a sphere that was swept back by the Sun's movement through the ISM, but what IBEX found was something different.
IBEX was designed to detect particles known as energetic neutral atoms. These start off as ionised atoms in the boundary region where they can pick up electrons and become neutral. Ionsed atoms have electrical charge and are affected by the charged plasma of the solar wind and the magnetic fields that are carried with it. Once they become neutral they are no longer affected by these magnetic fields and travel along straight trajectories. The detectors on IBEX were designed to pick up these energetic neutral atoms coming from the boundary region and over six months of observations, they mapped the whole sky.
What the results show is an unexpectedly bright ribbon of emission running almost 360 degrees around the sky, a feature that was not predicted by models of the heliosphere. This ribbon is thought to be where charged particles are becoming bunched at the boundary. The reason for this is not certain, although David McComas, IBEX's principle investigator, suggests that it could be caused by the magnetic fields of the Milky Way's own galactic wind interacting with the heliosphere.
The results, published in the journal Science during October, put the observations of the Voyager spacecraft in context. The two Voyager probes were launched in 1977 and are currently traveling through the interstellar boundary region where the energetic neutral atoms originate. While the results from IBEX match what the Voyager probes are encountering, the bright strip discovered by IBEX runs right between the positions of the two spacecraft. Eric Christian, IBEX deputy mission scientist at NASA's Goddard Spaceflight Centre likens this effect to having two weather stations which miss a big storm passing directly between them. The ribbon has also been detected in data from the Cassini spacecraft, although at different energies to the particles detected by IBEX. While it seems clear that the true shape of the heliosphere is somewhere between a comet and a perfect sphere, much more modeling is needed.
- Look deep enough with a sensitive telescope and a seemingly empty patch of sky is full of galaxies. Look closely and you'll see that they are often gathered together in clusters. These massive collections of galaxies are the largest gravitationally bound objects in the universe, but it is uncertain how long ago these clusters formed. Now, using a variety of instruments, a team led by Stefano Andreon of the National Institute for Astrophysics in Milan, Italy, has discovered the most distant galaxy cluster ever found.
The cluster, known as JKCS041, is located in the constellation of Cetus and lies about 10.2 billion light years away, beating the previous record holder by almost one billion light years. It is so far away that the light now arriving at Earth was produced by the cluster when the universe was only about a quarter of its current age.
The astronomers first discovered the galaxy in infra-red observations made with the UK Infra Red Telescope, UKIRT, in 2006. The optical light from galaxies this far away is shifted into the infra-red part of the spectrum due to the expansion of the universe, so old galaxies like these are often detected by infra-red telescopes. Further observations with both optical and infra-red telescopes confirmed the distance to the object, but could not rule out the possibility that, rather than being a genuine gravitationally bound cluster, the object could just be a chance alignment of galaxies along our line of sight. To test this, the team examined X-ray observations from the Chandra space telescope.
Nearby galaxy clusters have extended X-ray emission, caused by hot gas in the space between the galaxies. This gas, known as the hot intra-cluster medium, is only observed in genuine gravitationally bound clusters of galaxies and so is a good test of whether a group of galaxies just lie along the same line of sight by chance, or are physically associated. When the astronomers examined the Chandra observations of JKCS041, they found a significant amount of extended X-ray emission within the cluster coming from hot gas of the intra-cluster medium, showing that it is a physically connected group of galaxies.
This is an important discovery because this is close to the distance limit expected for a galaxy cluster based on how long it should take for them to assemble following the big bang, and studying its characteristics can reveal more about how the universe evolved
- 2009 has been a good year for exoplanets, and one team of astronomers have discovered most of them. Since the first planet was found orbiting a star other than the Sun, many more have been discovered using increasingly sensitive instruments and sophisticated techniques. Because they are so faint compared to their parent stars, most planets are discovered through indirect methods. One of the most successful has been the radial velocity method which uses the principle of the Doppler effect to detect the tiny changes in velocity of a star caused by an orbiting planet.
This is the technique used by the High Accuracy Radial Velocity Planet Searcher, or HARPS, instrument, mounted on the European Southern Observatory's 3.6-m telescope at La Silla in Chile which repeatedly measures the radial velocities of stars that might host planetary systems. On the 19th of October, members of the HARPS team presented their latest results: the discovery of another 32 new planets, bringing the total number of known exoplanets to more than 400. The radial velocity technique is most sensitive to large planets orbiting close to their parent star, but due to its high precision HARPS is capable of detecting smaller planets known as super-Earths. The new batch of exoplanets range in size from just five times the mass of the Earth to up to 10 times the mass of Jupiter.
HARPS has been largely responsible for the detection of 24 of the 28 known planets with masses below 20 times that of Earth and has now discovered more than 75 of the 400 known exoplanets, making it the most productive current planet finder. However, HARPS will soon have competition in the form of Kepler, a NASA satellite launched in March with the aim of detecting Earth-sized planets in the habitable zone, the region around a star where water can exist as a liquid. Rather than measuring the wobble of stars, Kepler will monitor their brightness looking for the tiny dips in intensity caused by planetary transits.
- October was another busy month of International Year of Astronomy events. On the 22nd to the 24th of October, the IYA Cornerstone Project, Galilean Nights, saw astronomers and enthusiasts taking to the streets all around the globe, pointing their telescopes at the same objects that Italian astronomer Galileo observed 400 years ago. Spread over three nights, the project saw hundreds of registered events take place with many people getting their first look through a telescope at Jupiter and the Moon.
Following on from Galilean Nights came the second MoonWatch event of the year. This UK-based event ran from October 24th to November 1st, encouraging people to go out and observe the Moon. As part of the event, Moonwatch was also held on Twitter on October 26th and 27th, turning it into a global event (see the trailer). Unfortunately, many observers saw nothing but clouds on both nights, but this didn't stop many twitter users joining in, tweeting and re-tweeting images, information and live video from across the world. Astronomy FM hosted a special Moonwatch show that went on for several hours including on the hour updates from Adrian West of Newbury Astronomical Society in the UK, and Elias Jordan, Tavi Greiner and Dr Ian O'Neill in the US. Despite the clouds, this second Moonwatch event was again an astounding success with twitter users from around the world joining in with a virtual star party of epic proportions. The team behind Twitter Moonwatch are already planning their next event, a Meteorwatch which will be held to coincide with the Geminid Meteor shower in December.
Neil talked to John Sarkissian (Operations Scientist, ATNF) about the history of the Parkes Radio Telescope in Australia from construction in 1961. We find out how it was involved in the Apollo 11 landings in 1969 as well as its astronomical research up to today. John curates a comprehensive website about the involvement of Parkes with Apollo.
The Night Sky
Ian Morison tells us what we can see in the night sky during November 2009.
The nights are getting longer. Due south after sunset is Pegasus, the Winged Horse, which you can use to find the Andromeda Galaxy. Below Pegasus is Pisces below which is Uranus. To the left of Pegasus and Andromeda are Perseus and Cassiopeia. Perseus contains the star Algol - an eclipsing binary which changes its brightness every few days or so. If you follow the line between Perseus and Cassiopeia with binoculars, you should spot the Perseus Double Cluster. Around to the east, Taurus the bull is rising with the Hyades and Pleiades clusters.
- Jupiter is in Capricornus and is easily visible in the evening sky in the south to south-west after sunset. Suring November, its magnitude drops very slightly; from -2.4 to -2.3.
- Saturn can now be seen in the pre-dawn sky when, as November begins and at magnitude +1.1, it will rise at about 03:30 UT, some three and a half hours before the Sun. By the end of the month it will be seen almost due south in the pre-dawn sky.
- Mercury passes behind the Sun on November 5th, so is hidden in the Sun's glare for all of November
- Mars is becoming more prominent in the morning sky, rising at about 21:00 UT in the middle of the month. It lies in the constellation Cancer, the Crab, and starts the month passing through the Beehive Cluster, M44! It will will rise at the end of the month at ~9pm and be due south around 4:45 am.
- Venus is now drawing ever closer to the Sun and can be seen low in the east rising an hour and 30 minutes (or less as the month progresses) before sunrise.
- A nice view of the last quarter Moon close to Mars will be seen around midnight on the 8th November. With binoculars, you should be able to see the stars of the Beehive Cluster as well!
- If it is clear on the morning of the 15th November and you have a very clear and low eastern horizon, you will have a chance to spot a waning crescent moon which is just 2% illuminated. Binoculars will almost certainly be required - but do not use them after the Sun has risen!
- Every year, on November 17th and 18th, the Earth passed close to the trails of cometry debris from Comet Temple-Tuttle which produce the annual Leonid Meteor shower.
- Cetus contains a very interesting variable star that was called Mira - meaning "wonderful" - so named by Johannes Helvelius in 1662. During its maximum this month (peak brighness is on November 18th) it could exceed the brightness of Menkar which has a magnitude of +2.5.
- At about 7-8pm on the 23rd November ,the Moon, a day before first quarter, is just over 2 degrees up to the right of Jupiter. Four degrees to the upper left of Jupiter is Neptune at 7.9th magnitude. It lies just to the left of a line of three stars, 42 Cap, the upper, at 5.1 magnitude, 44 and 45 Cap, below at ~ 6th magnitude. A pair of 8 x 40 binoculars should be able to encompass the field of view. Neptune will be easier to spot on the days before and after when the Moon is not so close in the sky - it will be just above Jupiter next month - one of that month's highlights!
The nights are getting shorter in the southern hemisphere. After sunset, in the north, you'll see the Square of Pegasus. Below that and to the right is Andromeda. Snaking around over to the north west is the Milky Way with Deneb in Cygnus and Aquila the Eagle above. High in the sky is the planet Jupiter with Neptune is down to the right. Towards the south, reasonably high, is the Small Magellanic Cloud with nearby globular cluster 47 Tucanae. Lower to the left is the Large Magellanic Cloud with the Tarantula Nebula below. The Southern Cross - Crux - can be found by using alpha and beta Centauri as pointers. The brightest star in Crux - Alpha Crucis - is actually a double star and they are separated by about 4 arcseconds. Just below Beta Crucis is the Jewel Box. Finally, below the Jewel Box cluster is the darkest region of the Milky Way known as the Coal Sack.
Odds and Ends
It looks as though NASA are getting ready to free the Spirit rover.
Galloway Forest Park in Scotland is making a bid to become a Dark Sky Park (the first in the UK). The decision is being made around the 14th Nov.
Jodatheoak has created a Flickr group for the Jodcast. Join up and add your astro images.
|Noticias en Español - Noviembre 2009:||Lizette Ramirez|
|Interview:||John Sarkissian and Neil Young|
|Night sky this month:||Ian Morison|
|Presenters:||Sarah Bryan, Jen Gupta, Stuart Lowe and Neil Young|
|Editors:||Stuart Lowe and Neil Young|
|Captain Sam Lovell:||Chris Montera|
|Number 1:||Steve Anderson|
|Educator 101:||Bruce Busby|
|Sarah Connor:||Gwendolyn Jensen-Woodard|
|Segment voice:||Cormac Purcell|
|Cover art:||Fox Mason at the control desk. This photo was taken in 1970. Credit: CSIRO|
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