Go to the archives
Eyes Up - September 2009
The monthly guide to what's in the sky over Perth for September 2009, written for the Scouts WA newsletter.
During September the days continue to get longer. By the 30th, the Sun rises at 5.56am and sets at 6.18pm. The Moon is full on the 5th and new on the 19th. Jupiter continues to be the most obvious of the planets, rising before dark and clearly visible high in the sky all evening, setting in the early hours of the morning. During the first half of the month Mercury is visible in the western sky for an hour or so after sunset; it will be faint so look carefully! Venus continues to be a morning object, visible in the east before sunrise.
A rare event happens this month: for a short time, the rings of Saturn will apparently disappear! The rings are 280,000km across but only 20km in thickness and are not solid but are made up of lumps of ice and rock. While they might appear to vanish, the rings do still exist, but they are so thin that when they are viewed exactly edge-on from Earth they cannot be seen. Imagine how hard it would be to see a CD held edge-on from several kilometres away! This phenomenon happens roughly every 14 or 15 years and only lasts a short time. If you have access to a telescope, try and take a look at Saturn - you can find it low in the western sky in the early evening. The rings will disappear on September 4th, and reappear on the 5th.
August saw one of the best meteor showers in the Northern hemisphere, the Perseids. The next good shower visible from the Southern hemisphere is known as the Orionids, so-named because they appear to travel outwards from the constellation of Orion. This shower peaks in October, but begins at the very end of September, so keep your eyes peeled for shooting stars if you are camping towards the end of the month.
The timings are correct for metro areas and will be slightly different for country observers and those in other states.
Posted by Megan on Thursday 27th Aug 2009 (04:12 UTC
) | Add a comment
Yalgoo lookout CREDIT:
It's National Science Week here in Australia, and it's been busy. I'd originally been going to do some talks at Como Science Fair, but they got the dates mixed up and told me it was on Saturday, rather than Tuesday. This was a problem as there was also a trip to do a viewing night at the primary school in Yalgoo (a few hours inland from Geraldton) on the Wednesday, which meant leaving Perth on Tuesday. I couldn't persuade any of my colleagues to go to Yalgoo, being the middle of semester most people had teaching commitments and didn't want to take three days out to head north, but I did get a volunteer to take over the astronomy talks at Como Science Fair. So, I ended up going to Yalgoo. Not that I minded really, Como would have been fun, but I do enjoy going north.
So, on Tuesday morning I picked up the four wheel drive, collected one of our students and his wife, loaded up with telescopes, and headed for Geraldton in the rain. We took a radio dipole and the digital projector, just in case it rained at Yalgoo.
We arrived in Geraldton at 5pm and headed for Nagle Catholic College where the science department were hosting a teacher PD night on astronomy presented by Rob Hollow, the education officer for the Australia Telescope National Facility in Sydney. He had planned to get out a telescope and do a viewing night, but the sky was covered in thick cloud so we spent the evening doing classroom activities instead. It was a fun evening and I came away with a few ideas myself! My favourite was the expanding solar system model, using a large piece of elastic, several pegs and some galaxy pictures. It's a bit more effort than the balloon model, but it's much more useful and less misleading.
The next morning we filled up with diesel and headed for Yalgoo at about 10am. After the cloud of Tuesday and the rain overnight, the sky was looking better but still not very promising. We arrived in Yalgoo at about lunchtime and found the school deserted. All the kids were off somewhere else, so we wandered around Yalgoo for a bit. After the rain over the winter, the area was looking amazingly green. I've only been up there a few times, but it was the greenest I've seen it. Some parts of the wheatbelt were actually reminiscent of Cheshire!
As the afternoon wore on and we assembled the telescopes, the kids from the other schools arrived and the clouds began to thin out. By sunset the sky had cleared completely and we were in for a good evening. After the kids had eaten dinner, they all wandered over the street to the oval where we had set up. Once again, I had an argument with the 5-inch, resulting in it going back in its box and not getting used. That telescope and I have issues
. The two Dobs, on the other hand, were superb. Rob manned one, showing off the Jewel Box, η Carina and ω Centauri, while Kevin looked after the other one, pointing at Jupiter. I wandered round with the laser pointer and tried to keep the kids from wandering off!
After about an hour, the kids had had enough and disappeared. We took the opportunity to take some photos - the sky really was the best I've ever seen. By this point though, it was half nine and I was absolutely exhausted after a week and a half of non-stop rushing around - Science Week is great, and the fact that stuff actually happens here without an argument is just so refreshing. I was tired though, so after taking a few pictures and packing away the scopes, I went off to catch some Z's. I would have loved to stay longer, just enjoying the view, but I also didn't want to fall asleep driving home! Rob suggested we should have a trip north sometime where we don't actually do any outreach, we just come up with any other astronomers that want to come, and just enjoy the sky! It sounds like a great idea to me.
The Milky Way from Yalgoo, M7 just below centre, taken with a Fujifilm Finepix S1000 (a single 8s exposure using the highest ISO setting the camera has) CREDIT:
Posted by Megan on Friday 21st Aug 2009 (10:02 UTC
) | Add a comment
Here in Perth, the 11th of August was a day like any other. The Sun came up, the lorikeets screeched, the gibbons in the zoo howled at each other, there was a bit of cloud, people got up and went to work. For some of us, though, it was a bit of a strange day.
In 2006, I began experimenting with radios trying to pick up the reflections of distant radio transmissions from the ionised trails of meteors in the upper atmosphere, with help from Eddie Blackhurst, an engineer at Jodrell. Eventually we got a working system together, and for the last year or so it has been recording data 24 hours a day. I accidentally broke the machine when I was home in June, but thanks to the efforts of the guys back at Jodrell we had a new machine up and running by 5pm Perth time on the 11th, just hours before the predicted peak of the annual Perseid meteor shower. I spent the entire evening trying to get a working system back up and running. It was a long night.
Meanwhile, something big was stirring in the Twitterverse. Masterminded by @NewburyAS, #meteorwatch was a global star party utilising Twitter to link astronomers around the world, all observing the same event, tweeting their observations and answering questions. It started off with a few keen enthusiasts, many people re-tweeted the initial announcement, and by the 11th it had gone truly global. At the height of the event, the list of Twitter's trending topics contained not one, but two references to the event: #meteorwatch and "meteor shower". This meant, of course, that many people who had never heard of meteor showers or the Perseids got curious and actually went outside and had a look at the sky. Many people who would probably never have looked up at the sky otherwise, went outside and saw shooting stars for the first time, then came back inside and tweeted about it. As the topics moved up the trending list, more and more people got curious what it was all about and there was a snowball sort of effect.
From where I live, the Perseids are not really visible as the radiant is too far north. I did have the radio receiver at Jodrell though, and through Twitter I could watch reports come in from all around the northern hemisphere. Watching tweets from people who had just seen their first ever shooting star was great, this was direct public outreach on an unexpectedly large scale. Between them, @NewburyAS, @ksastro and @astronomy2009uk answered questions from all over, and people kept them pretty busy over the course of a couple of days through the height of this year's Perseid activity.
All in all a great success, thanks to @NewburyAS and @ksastro who did a superb job keeping up with it all. If you're on Twitter, follow these two and watch out for future events. Even if you're not, you can always check out the new AstroTwitter blog for upcoming events.
Posted by Megan on Tuesday 18th Aug 2009 (15:27 UTC
) | 1 Comment
Happy Birthday Scitech!
Today was Scitech's 21st birthday. On August 13th, 1988, the first incarnation of the exhibition was launched. Since then, the staff and volunteers have taken the excitement of science and engineering to more than five million West Australians. That's pretty impressive. Much of that has been through the frequently changing exhibition at their location in Perth's West, but a significant amount has been through their outreach programmes, taking fun demos and science shows out to science fairs, schools, and community events all around WA. This also included a number of highly successful star parties earlier this year for the 100 Hour of Astronomy.
Not only do they run a large exhibition and modern planetarium, they also have an impressive workshop which has created numerous exhibitions over the years (it was open, so I went to have a nosy - there was a display on the human body with some rather graphic intestines, and a spacesuit!). Many of these have toured science museums around the world - two are currently touring Europe, two are in New Zealand, and one is over in Melbourne (they also created the "meteorite" that fell on Cottesloe beach back in April). In the main floor of the exhibition there are long-running displays, as well as a large space for temporary exhibitions which are either created in their workshop or on tour from elsewhere. The temporary exhibitions change regularly, so there's always something new to play with, and it's always very interactive. The place gets very noisy during the holidays!
As well as all this, Scitech are involved in numerous other projects as either active participants or coordinators. They host a CSIRO lab, manage the Scientists in Schools programme in WA, and are a big part of the AstronomyWA collaboration (and probably heaps of stuff I don't know about!).
This evening was something of a reunion for past staff members, as well as a celebration of 21 years of public engagement. The staff, both regulars and casuals, are a very enthusiastic bunch of people. As well as a large number of paid staff, they have a small army of volunteers who also take time to act as explainers in the exhibition in their own time. I met a few of them at the birthday bash this evening and they are an enthusiastic lot.
They've achieved a lot, but of course there's always more to do. If Australia gets the SKA, then WA is going to need plenty of bright young things with a strong interest in science and engineering. Scitech can play a big role in that, and I've no doubt that it will.
So, here's hoping that Scitech's next 21 years will be as successful. Happy Birthday!
Posted by Megan on Thursday 13th Aug 2009 (15:25 UTC
) | Add a comment
Here's to amateurs
Amateur astronomers enjoying the stars over Hardraw in the Yorkshire Dales CREDIT:
While recording the Jodcast
news for August
, I realised that I'd written about three discoveries by amateur astronomers in the one month. Firstly there was the start of the long-awaited eclipse of ε Aurigae
discovered by Robin Leadbeater
in the UK, then the impact feature
on Jupiter spotted by Anthony Wesley
in NSW Australia, and finally the mysterious white spot on Venus observed by Frank Melillo in the USA. This is a rather nice illustration of how amateur astronomers can contribute to real science. How many other fields of endeavor can you think of where this is the case?
This is something I've written about before. Back in August 2005, the magazine Astronomy Now
published a letter from a reader asking what the point of amateur astronomy was, given the huge surveys now being undertaken by professional facilities. The writer wondered whether it was worth the effort since there wasn't much left to be discovered with small backyard telescopes and the growing blight of light pollution was growing ever worse. Working on supernovae, a field where new discoveries are often made by amateur astronomers, I wrote a response
pointing out that amateurs can (and do) play a vital role in modern astronomy. Here's the gist of it:
"Many supernovae, comets and asteroids are discovered by amateurs as they scan the skies from their backyards. One easy example is the discovery of supernova 2005cs
in M51 (as reported in AN August, p19) which was discovered by Wolfgang Kloehr, a German amateur. Discoveries like these are reported to the whole community through IAU circulars, allowing researchers with access to larger telescopes to rapidly make follow-up observations. In the case of SN2005cs this is exactly what happened: we observed 2005cs with MERLIN
, the UK's radio telescope array, within a few days of its discovery. Amateurs also provide valuable data on meteor showers
, variable stars
and the fading of supernovae
, all events which are labour intensive to observe, but which can be measured accurately with modest equipment. The problem with large facilities is that there is huge demand on the time available, and many have small fields of view or are otherwise not set up for all sky surveys. As for observing from a city, two of our students managed to observe and estimate the magnitude of 2005cs using a 10-inch Meade from Manchester city centre so (as I said in AN), although it requires some perseverance it is far from a dead loss!"
It seems pretty obvious to me that amateur astronomers do a lot of really valuable work. Many of them are highly dedicated observers, building their own observatories, making the most of clear evenings and often traveling large distances to find a dark observing site. Their discoveries are numerous, they are using increasingly sophisticated equipment and techniques, and are producing some pretty impressive results. Some of their images are truly spectacular - just check out any issue of the popular astronomy magazines to see reader's pictures. Just as important though, amateur astronomers run astronomical societies who run or help out at public observing events and encourage newcomers to take their interests further. I know several societies who actively talk to school groups and run popular public events. This encourages an interest not just in astronomy, but more generally in science, engineering and the world around us.
So, here's to you amateur astronomers. Keep it up.
Posted by Megan on Monday 03rd Aug 2009 (13:05 UTC
) | Add a comment
In the news this month... and finally
Jupiter on July 24th by Anthony Wesley, Murrumbateman NSW Australia CREDIT:
Almost exactly 15 years after astronomers around the world watched as fragments of the comet Shoemaker-Levi 9 hit Jupiter, leaving black scars on the planet's cloudy surface, an amateur astronomer caught images of another impact
on the gas giant. First imaged on July 19th by Anthony Wesley
in New South Wales, Australia, news of the impact rapidly spread around the world. Within hours, several observers had confirmed the new black blemish on Jupiter's surface, and within days it had been imaged by the Keck telescope
and NASA's Infrared Telescope Facility
in Hawaii. The infra red observations showed that the scar was warm, indicating as upwelling of material in the planet's atmosphere, probably caused by an impact. Even the recently upgraded Hubble Space Telescope was used to image the event, despite commissioning of the new instruments not being complete. The Hubble image
was the first science observation carried out with the newly installed Wide Field Camera 3 and shows the instrument is performing well. The most recent images of the impact site show that the black spot is evolving and now contains two nuclei, probably due to the high winds and complex dynamics in Jupiter's dense atmosphere.
By coincidence, another amateur astronomer, Frank Melillo of New York in the USA, spotted a new feature in the atmosphere of Venus
on the same day. The Venus Express
spacecraft in orbit around the planet confirmed that the spot had first appeared four days earlier
. Observations in the ultra violet suggest that this feature was not caused by a meteorite impact and various suggestions have been put forward, such as a volcanic eruption, or a concentration of charged particles from the Sun, but as yet it is not known exactly what caused it.
Posted by Megan on Saturday 01st Aug 2009 (12:07 UTC
) | Add a comment
In the news this month... bubbles on Betelgeuse
An artist’s impression of the supergiant star Betelgeuse CREDIT:
Using state of the art techniques, two teams of astronomers have obtained the sharpest ever images of the supergiant star Betelgeuse. The second brightest star in the constellation of Orion, Betelgeuse
appears red even to the naked eye, and is one of the largest stars known, almost 1000 times larger than the Sun. It is a type of star known as a red supergiant and is so enormous that if it were placed at the centre of the solar system, its surface would lie almost at the orbit of Jupiter. Stars this massive run out of fuel much quicker than smaller stars like the Sun, and eventually explode as supernovae.
There are still some unanswered questions about red supergiants, one of which is how they shed material. These stars can lose as much material as is contained in the entire Sun in just 10,000 years, but the mechanism by which this occurs is not well understood. But in work accepted for publication in the journal Astronomy and Astrophysics, two independent teams using ESO's VLT
have made observations which might provide some answers.
The first team used adaptive optics which attempts to correct for the fluctuations in the Earth's atmosphere which make stars appear to twinkle. They combined this with another technique known as "lucky imaging
" where only the sharpest exposures are combined to produce a high resolution image in a similar way to imaging with a webcam through a backyard telescope. The resulting images are so sharp that they could detect a tennis ball at the distance of the International Space Station. The team's images of Betelgeuse show a large plume of gas extending out from the star to more than six times the radius of the star itself, showing that it is not shedding material evenly in all directions.
Meanwhile, the other team used the VLT interferometer, which combines the light from three telescopes to produce results with much greater resolution. Using this technique, the second team were able to indirectly detect features up to four times smaller than the other teams images, allowing them to study the surface of Betelgeuse. They found that the gas in the star's atmosphere is moving up and down in giant bubbles like huge convections cells almost as large as the star itself. Together, these two superbly detailed observations
suggest that it is these large scale motions in Betelgeuse's atmosphere which are responsible for producing the giant plumes of material.
Posted by Megan on Saturday 01st Aug 2009 (11:46 UTC
) | Add a comment
In the news this month... probing the black hole in M87
The inner jet of M87 as imaged by the VLBA at a wavelength of 2cm CREDIT:
NRAO/AUI and Y. Y. Kovalev, MPIfR and ASC Lebedev
Among the brightest and most energetic objects in the universe are so-called Active Galactic Nuclei (AGN
). These are objects outside the Milky Way, thought to be powered by material falling onto supermassive black holes in the centre of other galaxies. The process can create powerful jets which can accelerate particles up to very high speeds and generate very high energy gamma-ray emission. Although astronomers have known for some time that these AGN are bright sources of gamma-rays, they did not know exactly where in these galaxies the high energy emission originated. But in research published in the online edition of Science magazine
on the 2nd July, a collaboration of more than 350 scientists has finally narrowed it down.
High energy emission from the nucleus of the active galaxy M87
was first detected in 1998, and gamma-ray outbursts have since been confirmed by the HESS
telescopes located in Namibia, Arizona and La Palma respectively. All of these experiments are gamma-ray detectors which pick up this high energy emission, but do not have sufficient resolving power to accurately determine the location of the outburst within M87's core. Located 50 million light years away, M87 is the largest galaxy in the Virgo cluster and contains a central black hole six billion times as massive as the Sun.
In order to determine the source of the gamma-rays, the HESS, VERITAS and MAGIC collaborations teamed up with astronomers using the Very Long Baseline Array
- a collection of ten radio telescopes spread across North America from Hawaii to the Caribbean. By linking widely separated radio telescopes together, astronomers can synthesise a much larger telescope, resulting in images with much finer detail. Using all four instruments, HESS, VERITAS, MAGIC and the VLBA, the team monitored M87 over 50 nights between January and May 2008. As well as detecting gamma ray flares, the observers also detected large flares of radio waves from M87. Using the VLBA's high resolution they determined that these flares were occurring at the same time as the gamma ray flares and were being generated in a region very close to the black hole where material falling in forms a tightly rotating torus known as an accretion disk. The observations show that the high energy emission is coming from an area no larger than 50 times the size of the black hole's event horizon - the area within which matter cannot escape from the black hole. For the black hole in M87, this is a region roughly twice the size of the solar system.
Posted by Megan on Saturday 01st Aug 2009 (11:20 UTC
) | Add a comment
In the news this month... new method detects ancient stellar explosions
This image was taken with CFHT as part of the telescope’s Legacy Survey and shows one of the deep fields used to find the most distant supernovae to date. CREDIT:
Jeff Cooke / CFHT
Using telescopes high on the islands of Hawaii, astronomers have detected
light from supernovae which occurred roughly 11 billion years ago, smashing the previous distance record for such objects. Led by Jeff Cooke
, a cosmologist at the University of California, the team used a new technique to look for the tiny change in brightness of a distant galaxy due to a stellar explosion. They were looking for the signatures of a class of explosion known as type IIn supernovae
, caused by stars between 50 and 100 times as massive as the Sun. These stars are different because they shed a large amount of material before they die. When the final catastrophic explosion occurs, the remaining material and the resulting shock wave plough into the surrounding gas previously expelled from the star, resulting in a remnant so bright that it is still visible many years after the event. Because these type IIn supernovae are the brightest class of stellar explosion, they are the most likely to be detected at large distances.
The normal method of searching for supernovae is to compare two images of the same galaxy taken on different nights and look for new objects in the image. While this technique works well for nearby galaxies where supernovae will appear relatively bright, it becomes increasingly difficult in more distant galaxies. Rather than looking at individual images taken on single nights, Cooke's team took five years of images covering four separate patches of sky and stacked them together creating one composite image per field for each year of observation. By comparing the brightnesses of each galaxy in the stacked images, the astronomers identified four potential supernovae. They then used the Keck telescope
to observe the spectra of each of the candidates, using the light collected to determine the object's composition and distance. This follow-up work showed that three of the candidates were supernovae, two of which occurred more than 11 billion years ago, beating the previous record by 2 billion years.
The results were published in the 9th July issue of the journal Nature
where the authors suggest that using this method with planned synoptic surveys on 8-m class telescopes could identify an estimated 40,000 type IIn supernovae at this distance, as well as even older explosions caused by some of the first stars created following the Big Bang, probing stellar processes all the way back to the very early universe.
Posted by Megan on Saturday 01st Aug 2009 (10:58 UTC
) | Add a comment
In the news this month.... breaking news
The location of the star epsilon Aurigae CREDIT:
Stellarium / Megan
In breaking news it has been reported
that the long-awaited eclipse of the star ε Aurigae
has begun (S&T
). Most eclipsing variables are caused by two stars in orbit, periodically blocking each other's light, but in the case of epsilon Aurigae the eclipsing object is thought to be a long thick disk of gas, possibly containing stars hidden in the dense material. Spectroscopic observations by Robin Leadbeater
, an amateur astronomer in the UK, have shown changes in the spectrum which could be due to the leading edge of the eclipsing cloud as it crosses in front of the star. If this is the case, then as the eclipse progresses, the star will begin to fade as thicker parts of the cloud move across our line of sight. Eclipses in this system occur every 27.1 years, and the star is predicted to fade from its normal magnitude of 3.0 down to 3.8 by the end of the year. Amateur astronomers interested in variable stars are encouraged to make their own observations and send their results to the AAVSO
Posted by Megan on Saturday 01st Aug 2009 (10:34 UTC
) | Add a comment
Powered by Marzipan!
Last updated: Sunday, 22-Jun-2014 23:32:13 BST