Eye on the sky
Amateur astronomers are making a unique contribution to science’s understanding of the universe, reports Marilyn Moore a Melbourne geologist and writer.
CHRIS MORLEY’s Sandy Ridge Observatory sits astride a prominent ridge in Victoria’s Strzelecki Ranges. Morley belongs to the Latrobe Valley Astronomical Society, a small group of enthusiasts based some 150 kilometres east of Melbourne, and he enjoys hosting occasional viewing nights. Only a short walk from his house, the observatory is home to a Meade 14-inch Schmidt Cassegrain telescope as well as smaller refractor and finder scopes. These are not huge telescopes – deep space telescopes are measured in metres rather than inches or millimetres – but they are far bigger than those that most people would typically look through.
It’s 9.30 pm and moonrise is still several hours away. We cross the lawn in complete darkness, assisting the slow process of allowing our eyes to adjust. An engineer by day and stargazer by night, Morley built this observatory himself. The building, set on a heavily reinforced concrete foundation, is cylindrical, 3.6 metres in diameter and two storeys high to the base of the dome, which rotates on a pair of custom-made steel rings fitted with heavy-duty rollers. A sliding roof panel opens the dome to the sky.
Morley unlocks the observatory and we step inside. An almost impenetrable darkness smothers a brief impression of computers, bookcase, desk and whiteboard. Barely illuminated, an elegant timber staircase spirals upward. We tread cautiously to the upper level, where the dome has already opened to reveal a narrow slice of star-studded sky. I begin to make out the main telescope, locked into position on its heavy computer-controlled mount, with piggybacked refractor and finder scopes. The setup fills centre-stage, leaving only a narrow ring of standing room for onlookers. Morley picks up a remote control device and enters a code that identifies our first target object. “Watch out!” he calls. From out of the gloom, like the massive arm of a giant deep-sea creature, the forty-six-kilogram counterweight swings past my ear as the telescope rotates smoothly into position.
Now I, too, am about to witness the magic that has transfixed stargazers throughout history as Chris Morley takes me on a beginner’s tour of the night sky. I put my eye to the eyepiece and am almost immediately mesmerised. Our first object is Pleiades, better known as the Seven Sisters. It’s an “open star” cluster, one of the closest to Earth, consisting of an exquisite “little dipper” among an array of other stars. Most people see at least six of Pleiades’s stars with the naked eye, but up to one hundred are visible through the refractor scope tonight. It’s as stunning as a giant explosion of fireworks during that brief eternity when they seem to hang in the sky. This cluster of predominantly hot blue stars is relatively young and lies about 400 light years from Earth, so we are looking at it as it was 400 years ago – while Shakespeare was writing his plays and Galileo convincing himself of the merit of Copernicus’s heliocentric theories.
Reluctantly we leave Pleiades to travel to the great star Aldebaran. With a luminosity 425 times that of the Sun and a diameter forty-four times as great, it’s classified as a Red Giant and is the fourteenth-brightest star in the sky. It sits in the constellation Taurus, easily visible between Pleiades and the nearby constellation Orion (“The Saucepan”). The name is Arabic: Al Debaran, the follower. Pleiades’s little friend. It’s humbling to realise that the ancients knew these stars so much better than I do.
The big counterweight swings again as the telescope repositions its focus on Jupiter low in the northern sky. We can easily pick out all four Galilean moons and the latitudinal banding on the giant gas planet. I am impressed: for the first time in my life, I am beginning to see the night sky in three dimensions. It’s no exaggeration to say that this is a life-changing experience.
PETER NELSON’s Ellinbank Observatory has a particularly impressive dome: it’s fully electronic and rotates automatically as the telescope tracks across the night sky. Nelson himself is impressive, too: an engaging man with a quiet twinkle, he’s a physicist-turned-radiographer by day. He’s also an excellent communicator, the sort of person people listen to. It’s no surprise to find that he was the early driving force behind the contributions made to world astronomy by members of the Latrobe Valley Astronomical Society. A member himself since 1987, Nelson is also director of the Variable Star Section of the Astronomical Society of Victoria. It was at the 1987 Victorian Astronomy Convention that Nelson first met Chris Stockdale, a lifelong enthusiast who’d built his own observatory and joined the Latrobe Valley group in 1972. Stockdale, whose background was in IT and electronics, proved an eager colleague for Nelson, adept at building and adapting software and gadgetry to make observing simpler, faster and more accurate.
At first glance, Stockdale’s Latrobe Valley observatory appears more primitive – you have to stoop quite low to get inside and the computers are far from new – but it’s a serious workplace. Noticeably, both Stockdale’s 11-inch Schmidt Cassegrain and Nelson’s 12.5-inch Corrected Dall Kirkham telescopes have no eyepieces fitted. They are set up for scientific work and have cylindrical CCD detectors (effectively digital cameras) mounted behind the lenses and connected to various computers. Nelson and Stockdale are both internationally recognised experts in the art of high-precision photometry.
Because the tracking capability of the telescope allows long exposures to be made, photometry is especially useful when the target object is only faintly detectable. The fainter the object, the higher the absolute value of the star’s brightness (or “magnitude”). The naked eye detects objects up to magnitude 6, or magnitude 9 with binoculars. Nelson’s and Stockdale’s CCD/telescope combinations usually detect to magnitude 17 or 18, especially when images are combined to improve signal-to-noise ratios. “A lot of useful science can be done with small telescopes,” says Nelson. “Off the shelf stuff can reach magnitudes that Palomar” – Caltech’s much-lauded 200-inch telescope, still used by researchers today – “did in the fifties.”
To investigate changes in the brightness of an object – a star, planet or moon – telescopes set up for photometry take repeated snapshots over a period of time. The data is corrected for background noise, colour bias and uneven illumination, and then graphed, resulting in a curve that describes the variation in brightness over time for the event being observed. This could be an eclipse or occultation (when an apparently larger body passes in front of, and blocks light from, an apparently smaller body) or any other event that causes the amount of light reaching Earth from a particular source to change. Eclipses of moons by their planets provide important data for deducing precise orbits, essential for navigating interplanetary spacecraft, among other things.
Peter Nelson started working on the Jupiter project with US mathematician and software engineer Tony Mallama and a couple of others. Between 1990 and 2000 the group, which Stockdale joined around 1996, made over 200 measurements of the occultations of Jupiter’s moons. The results were impressive. “The exact moment that the moon exits Jupiter’s shadow is taken to be the halfway point between it being in full shadow and full light,” says Stockdale, “and every pixel of each CCD image is analysed to determine those points as accurately as possible. By taking many measurements over a number of years, a precise story gradually emerges.” Countless observations of these eclipses had, of course, been previously made, but the use of CCDs and Nelson’s and Stockdale’s meticulous observations served to significantly refine existing models. “We found that Io was in a different place in its orbit by sixty-two kilometres,” says Stockdale. “Europa was out by 267 kilometres, Ganymede by 142 kilometres and Callisto by 146 kilometres. That’s quite a lot, really.”
According to Morley, it’s a discovery that “would have been of particular interest to an organisation like NASA.” The more precisely the locations of Jupiter’s moons can be predicted, the less likely it is that interplanetary spacecraft will interact with them in an unexpected manner. Close-range work like remote sensing and gravity-assisted spacecraft navigation is critically dependent on knowing exactly where the moons will be at any given moment. “The Galileo space probe used our data,” recalls Nelson with satisfaction. The probe, launched on 18 October 1989, monitored the Shoemaker-Levy 9 comet’s collision with Jupiter in 1994, observed Io’s volcanism, and discovered not only liquid oceans under the icy surfaces of Europa, Ganymede and Callisto but also Ganymede’s magnetic field. These discoveries all owe something to Nelson’s painstaking early work.
Stockdale quickly got used to setting his alarm for the wee hours and was soon monitoring every eclipse by a Jovian moon that was visible from his observatory. By 2010, Tony Mallama at the University of Baltimore had analysed 548 data points spanning two decades and produced a precise data set with an almost continuous distribution. “The new data set allowed measurement of regular oscillations in the orbits of the Galilean moons,” explains Stockdale, “something which could never have been achieved before.” As with the earlier work, a number of anomalies showed up between the predicted and observed locations of the moons – anomalies so fine-scale they’d previously been unrecognised.
Such far-reaching results seem a far cry from the discoveries arising from Rømer’s first occultation measurements in 1671, but the basis for well-supported research has never changed – it has always required dedicated, accurate and reliable observation. When Stockdale and Nelson independently record the same event, the tight coincidence of their data presents an unassailable story. “We’re usually the same to within 0.3 seconds or better,” says Stockdale. “Most curves are virtually on top of one another.” Even using only a “primitive” time standard – the two observatories are about 45 kilometres apart as the crow flies – agreement to within a fraction of a second is pretty amazing given the relatively imprecise definition of some of the events they monitor.
An international focal point for variable star research is Arne Henden, director of the American Association of Variable Star Observers, or AAVSO. Henden, a professional astronomer and software/instrument specialist, has done much to upgrade the calibre of (and respect for) amateur observations. “Previously things were a bit patchy,” says Nelson, who has been on one of Henden’s courses in Boston and has now “officially” notched up over 100,000 observations. “You had to establish credibility over time.” Despite their modesty, observations conducted by Nelson and Stockdale are clearly up there with the best. Recognition brings rewards in the shape of exciting collaborations – Nelson babysits an AAVSO research telescope in a second observatory on his property – and a significant proportion of their work focuses on requests from professional organisations. “There’s a project happening with Hubble and the Cosmic Origin Spectroscope,” Nelson later reveals. “They’re studying a white dwarf at the hub of a binary pair, and they need to do some far-UV spectrometry. They can only look at this variable star when it’s dull, or the satellite’s delicate spectroscope sensors would be irretrievably damaged. ” The project relies on a small group of amateurs, including Nelson, to provide this vital information. There’s no shortage of motivation to keep up the good work.
Are there other amateur observers doing this sort of work? Not too many, it seems. Nelson mentions Tom Richards at the Woodridge Observatory near Eltham in Victoria, whom both he and Stockdale have collaborated with from time to time. “He does his own thing (with variable stars) and he does it very well.” Richards, a former professor of computer science, is the current director of the Variable Star Section of the Royal Astronomical Society of New Zealand, or RASNZ, (now called Variable Stars South) and, like Stockdale and Nelson, is also a regular contributor to New York’s Centre for Backyard Astrophysics, a global network of small telescopes dedicated to photometry of cataclysmic variables. There are, of course, quite a few private observatories run by amateurs not known to the ASV, as well as a large number of telescopes not necessarily being used in an observatory. According to the Australian Astronomical Society, there are ten registered private observatories in Victoria, forty-two in Australia. The list doesn’t include Nelson’s, Richards’s or Morley’s, although all would meet the strict registration conditions.
Registered or not, individual backyard astronomers who contribute significantly to the professional research effort generally become well-known within the fraternity. And it’s not necessary to own a lot of expensive gear. Many important discoveries have been made (or contributed to) by amateurs using relatively basic equipment. “Amateur astronomers are usually best placed to make discoveries that require long-term detailed observations,” confirms Chris Morley. “They have relatively unlimited viewing opportunities. Professional astronomers usually have limited access to large telescopes – there is a lot of competition.” Nelson agrees. “As an amateur, you can contribute significantly,” he says. As a professional, he adds, “you might book three nights on Mauna Kea two years ahead. When you get there your target might not perform, or it might be cloudy, or you might have equipment problems … As equipment improves, astronomers look further and further into space for fainter and fainter objects. However there is still much to be learned from studying brighter objects closer to home. We shouldn’t forget that.”
DEEP in Gippsland’s Strzelecki Ranges, another dedicated enthusiast shows just how much can be achieved with a minimum of equipment. Rod Stubbings, a plumber by trade and self-confessed “variable star” junkie, has made more than 214,000 observations of the changing brightness of variable stars over the past nineteen years. This feat alone elevates him to the ranks of a small handful of observers worldwide. Along the way his humble observations have led to a string of significant discoveries.
Stubbings, who looks pretty good for a bloke who didn’t get to bed until 4 am, tells me his life changed dramatically after he attended his first meeting of the Latrobe Valley Astronomical Society in 1992 or 1993, where he was introduced to Peter Nelson. Nelson was clearly angling to recruit new blood, and Stubbings, on his own admission, took the bait. He realised that he could make a real contribution to astronomy if he were to accurately record changes in brightness of variable stars and send them on to the proper organisations.
The Royal Astronomical Society of New Zealand had become the recognised centre for variable star research in the southern hemisphere, so Stubbings contacted then director, Sir Frank Bateson. Armed with the society’s beginner’s manual, he made his first observation in May 1993. After a month he’d made ten. He took to it like a duck to water, and Nelson kept him supplied with charts of additional variable stars to monitor. By 1997 he realised he was observing more outbursts than the “official” ones appearing on the network, so he decided to submit his as well. “There was no point in keeping my outbursts in my logbook,” he says logically. About two months after he had begun to send off his data, he received the following email from Bateson: “You will be pleased to know that your alert notices are being well regarded world wide. Keep up the good work.” The former director of the AAVSO, Janet Mattei, also encouraged him, requesting that the association be copied into all his alerts. Stubbings suddenly found himself centre-stage in a global network.
Rod Stubbings’s biggest asset is his extraordinary memory – the sort of memory that leaves mere mortals dumbfounded. Nelson confirms that Stubbings has “rock-star” status in astronomy circles, but you’d never realise this in meeting him; he’s just an easy-to-talk-to chap who’s as proud of his family, the new paint job on the house and his pedigree black-faced Dorper sheep as he is of his astronomical achievements.
What is it, exactly, that he does so well? Stubbings has memorised some 500 different groupings of stars that he observes during the course of a year. Not only has he memorised their locations, but also their magnitudes. If one star is even 0.1 brighter than before, he notices. Experienced observers can estimate the brightness of a variable star by comparing it with nearby reference stars of known (and constant) magnitude. He insists that it’s not difficult. “I ‘star hop’ with the finder first,” he explains, pointing to the refractor that’s piggybacked onto his Meade DS-16 400 mm Newtonian reflector, “and I see angles and patterns that lead directly to my various star fields. That’s all done from memory. Then I transfer to the big telescope.” The locations and magnitudes of countless guide stars, along with hundreds of variable stars and their associated reference stars, are all in his head, although he admits he does occasionally double-check with a set of star charts before sending out an important alert. No computers, no complicated analysis or calibration, no worries about temperature fluctuations and shifting focus or tracking… just an astoundingly accurate memory.
Stubbings studies about 150 stars on a single night. “I don’t follow the guidelines for observing,” he admits. It seems that once observers understand a star’s activity pattern, they usually concentrate on observing it only when it’s expected to flare. “I’d rather look at all of mine every couple of days, even several times per night,” says Stubbings. That’s how I pick things up.” It’s a system that’s certainly worked well for him. Stubbings is responsible for a large number of first-ever visual outburst detections, along with many others that have revealed the true nature and reclassification of variable stars. A list of his publications, awards and most notable observations was recently compiled for a forthcoming AAVSO newsletter. It’s a huge body of work, a significant achievement by any standard. And he’s still a youngish man.
Over time, Stubbings’s attention has progressively shifted from regularly variable stars like Eta Carinae to “cataclysmic” variable stars, whose shifts in brightness were unpredictable but often explosive and nova-like. He likes to recall one of his first such observations, on the eclipsing-type dwarf nova OY Carinae, which occurred around 2 am. “Do I ring somebody at this hour?” he wondered. Would Frank Bateson be awake? Stubbings made the call. Bateson answered immediately – typically, as Stubbings was later to learn. “He was very appreciative,” recalls Stubbings. “The alert triggered [all the necessary] satellite observations.”
Development of the internet during the 1990s streamlined the notification process considerably. The Variable Star Network was set up to create a global professional-amateur network of researchers observing not only cataclysmic variables but also things like black-hole binaries, supernovae and gamma-ray bursts. Stubbings, now recording more than 1400 observations (including thirty to sixty dwarf nova outbursts) each month, emails notifications of outbursts to the American Association of Variable Star Observers, the Variable Star Network and the Royal Astronomical Society of New Zealand each night. Photometrists Nelson and Stockdale would also be alerted by this process and leap into action.
“Last year T Pyxis went off,” says Nelson. “It’s a recurrent nova that goes off every thirty years or so. And that’s the beauty of the network: Rod alerted us and within half an hour we were all onto it.” Nelson recorded some 10,000 observations of this event, including three hours of data taken over the time that the star brightened. The professionals need as much data as possible, says Nelson, covering “the brightening, the maximum, the decay so they can look at pulsations and orbital humps.” As with most of his work, Nelson’s detailed observations were conveyed to AAVSO as well as to the Centre for Backyard Astrophysics in New York and Taichi Kato in Japan.
ON STUBBINGS’s long list of “firsts,” one particular date stands out in his memory: 15 September 1999. An abnormally bright flare-up of variable star V4641 Sgr (in the constellation Sagittarius) caused him to send out an alert that attracted immediate attention around the world. Information consequently collected from large radio telescopes revealed that V4641 Sgr is a black-hole binary system, a fact previously unrecognised, and at 1600 light years away, one of the nearest black holes to Earth. “This emphasises the scientific value of visual observations in variable star astronomy,” Stubbings firmly points out. He is adamant that amateurs are best-placed to make them. “Professionals have to schedule observing time at large observatories a year or so in advance. These (important) outbursts would go unobserved.”
Stubbings received the prestigious AAVSO Director’s Award in 2002. On 24 January 2012 he clocked up his 200,000th observation. As well as conducting his own observations, he regularly receives requests from astronomers and professional organisations around the globe to monitor specific stars for them, usually to assist with scientific research programs. Perhaps the most poignant request came from New Zealand astronomy legend, Albert Jones, now aged ninety-two. Realising that he didn’t have a lot of observing time left, Jones wrote to Stubbings a couple of years ago and asked him to take over the regular monitoring of a number of “his” variable stars. “He was worried that nobody would keep a proper eye on them,’ says Stubbings.
Stubbings has been compared with another amateur astronomer noted for his exceptional memory, Reverend Robert Evans of Hazelbrook in the Blue Mountains of New South Wales. Evans, who has received numerous prestigious international awards and been written about by Bill Bryson (in The Short History of Nearly Everything) and Oliver Sacks (in An Anthropologist on Mars), regularly scans more than 1500 galaxies by eye through his portable twelve-inch telescope, and can immediately tell if a new brighter star appears. Since 1980 he has single-handedly discovered more than forty supernovae (giant stars that collapse and brilliantly explode as they die, visible as such for only a few days or weeks); prior to his discoveries, fewer than sixty supernovae had been discovered worldwide. When interviewed, Evans inadvertently (but beautifully) summed up the improbability of one man’s ever achieving such a feat: “There’s something satisfying, I think,” he told Bill Bryson, “about the idea of light travelling for millions of years through space and just at the right moment as it reaches Earth someone looks at the right bit of sky and sees it.” I’m sure Stubbings would feel this way too.
Evans’s world record is likely to remain unchallenged as traditional techniques are superseded by technology. Stubbings is concerned that the move towards automation and digital processing might affect the usefulness of his own work. “Dunno if you’ll get observers like me any more,” he says pensively. “We live in a gadget world now.” Will astronomers stop listening to his alerts? It doesn’t seem likely, not in the short term, anyway. Evans and Stubbings are both delighted by the occasional failures of modern technology. “Automatic detectors can’t always distinguish binary stars,” says Stubbings. “And occasionally they are simply wrong! I believe you cannot undervalue the contribution of visual observing compared to CCD imaging. A CCD camera cannot make instant judgments on a star’s state, or call upon experience the way a visual observer can when directly viewing the stars.” A massive new CCD array being built in South America “will minimise bleeps like the ones Rod mentioned,” says Peter Nelson, “but people like Rod will always be needed. The new array will be programmed to immediately latch onto important alerts. There are lots of smarts happening.”
Of course Nelson, Stockdale and Stubbings are not the only Australian amateurs to have made a significant contribution to global astronomy. There is a long tradition here of noteworthy observations, and the achievements of two early amateurs in particular have been famously recognised: Gale Crater on Mars, the touchdown site of NASA’s probe Curiosity in August 2012, was named after renowned planetary observer Walter Frederick Gale (1865–1945); and the Australian $100 note bears a portrait of legendary astronomer John Tebbutt, who between 1880 and 1889 continually outperformed the state observatories. Exciting achievements continue to this day in backyards across the country: since 1973, the Astronomical Society of Australia has awarded its Page Medal seventeen times for outstanding feats of amateur research. “Amateur” in no way implies second-rate when referring to such distinguished researchers – it’s just that nobody pays them to undertake their work.
BACK at the Sandy Ridge Observatory, we have been admiring Alnitak (a hot blue supergiant) and Rigel (the brightest star in Orion, a blue-white supergiant with a luminosity 130,000 times that of the Sun). Now Morley has bumped up magnification of the Schmidt Cassegrain telescope so that we can have a closer look at that most intensively studied of celestial features, the Great Orion Nebula. If you could spend the rest of your life looking at only one thing, this magnificent nebula might be it. Some 1320 light years distant, Orion has revealed much to scientists about the process of how stars and planet systems are formed from collapsing clouds of hydrogen gas and dust. It’s an engrossing sight, often referred to as a stellar nursery.
But perhaps the best is yet to come. The roof opening is rearranged so that we can take a look at the southern sky. The telescope zooms in on a large, low-density cloud of partially ionized gas sitting on the leading edge of the Large Magellanic Cloud, itself a well-known galaxy easily visible to the naked eye. And what a sight: the Tarantula nebula, a mere 160,000 light years away, looms immediately into sharp focus, revealing events that happened at the time when modern man – Homo sapiens sapiens – first walked on Earth. Fabulously beautiful swirling arms of cloud surround a brilliant star cluster. Morley describes the core as an “extremely bright compact star cluster some thirty-five light years in diameter.” His words are technical and precise but the enthusiasm shines through. “It’s by far the most active starburst region within the realm of ‘nearby’ galaxies,” he says. “Tarantula Nebula would cast shadows on Earth were it as close as Orion.”
With the imminent rise of a gibbous moon over Sandy Ridge, our evening’s viewing comes to an end. We shut down the observatory and trail blindly back across the lawn, eyes watering from the unaccustomed brightness of household lights. My brain’s simply buzzing. It’s been such an experience. Such a privilege, too, to have been allowed a glimpse into this hidden community of dedicated observers, driven by a passion for their subject and an unbounded sense of adventure. A touch of technical genius hasn’t gone astray, either. They say they do it for relaxation, for the excitement of discovery and for the sheer enjoyment, but there’s no doubt whatsoever that the extraordinary commitment of these unpaid astronomers and their meticulously obtained (and generously shared) observations are germane to many of the successes of professional astronomy.
“It’s more than excitement,” confirms Peter Nelson. “It’s really worth doing. We do have an impact.” So next time you read that a black hole has been discovered, or an especially bright supernova, or a new comet – spare more than a passing thought for the observers whose countless hours of nighttime effort may well have triggered that discovery. In the cut-throat world of scientific research, this example of ongoing cooperation and respect between amateur and professional astronomers is a circumstance almost as wondrous as the heavens themselves. •
Marilyn Moore is a Melbourne geologist and writer who happens to number Chris Morley amongst her siblings. This is an edited version of a longer essay which can be downloaded here as a PDF.