Innholdsfortegnelse for May/June 2023 i Australian Sky & Telescope

LINED UP ALONG THE WET and slippery deck of the landing craft Castor 02 are four great spheres, each about 2.5 metres across. Wrapped in silver-coloured material, they resemble the EVA pods in Stanley Kubrick’s science fiction movie 2001: A Space Odyssey. But these Launchers of Optical Modules (LOMs) will not take off into deep space. Instead, they are bound for the bottom of the Mediterranean Sea, some 2,450 metres below the ship. Paschal Coyle, director of research at the Center for Particle Physics of Marseille, peels away part of the protective wrapping on one of the giant spheres, to reveal some of the 18 shiny Digital Optical Modules (DOMs) that are hidden inside. As large as a typical beach ball, each spherical DOM is outfitted with 31 photomultiplier tubes,…

GO TO MOUNTS, autoguiders and narrowband filters are all wonderful inventions — but a minimalist approach has its advantages. And taking astrophotos with just a camera mounted on a tripod is about as minimalist as it gets. If you’re travelling, this may be the only option available given airline baggage restrictions, and it might represent the limit of what you can carry in a backpack on a hike to a remote location. It’s coincidentally the most budget-friendly approach. But there’s also real joy in capturing compelling images using the absolute minimum amount of equipment. Gearing down A basic setup actually requires careful planning and employing a few ‘best practices’ to ensure you can wring out every drop of your gear’s potential. To begin, let’s consider your camera and lens settings.…

STELLAR CONGLOMERATES GLOBULAR CLUSTERS ARE impressively dense, spherical collections of stars typically found in the halos of spiral galaxies. We inherit the term from William Herschel’s paper ‘On the Construction of the Heavens,’ published in 1785 in the Philosophical Transactions of the Royal Society of London, in which he described a group of objects that “form themselves into a cluster of stars of almost a globular figure”. Of the roughly 190 globular clusters associated with our galaxy, about 40% are found in some of the richest parts of the winter Milky Way. In 1918, the American astronomer Harlow Shapley mapped the distribution of globular clusters to determine the Sun’s position within the galaxy. He correctly deduced the location of the galactic centre — pinpointing it in Sagittarius — based on…

ANYBODY FAMILIAR with my column knows that I’m a bit of a binocular nut. The view through two eyes impresses me much more than the view with one eye closed. But I’m not normally a fan of binoviewers. The designs I’ve seen all use beam splitters to divide the incoming light cone in two and send a half-strength copy off to either eye. The result is exactly the same view in both eyes, which doesn’t provide the dynamic integration that happens in your brain when each eye is seeing a slightly different image. Plus, the contrast always seems to suffer, and often the extended light path requires a Barlow to bring it to focus. That means you can’t get a wide-angle view, which is where binocular scopes really shine. But…

PRO-AM COLLABORATION For most of astronomy’s history, observers recorded what they saw at the eyepiece by jotting down notes, sketching, or both. These methods can be subjective, leading to eclectic interpretations of the science of the skies. Nonetheless they afforded us the only view of the universe until the early 19th century, when a new technique of recording celestial phenomena arrived on the scene: photography. Glass plates and women computers. By the time Edward Charles Pickering became the fourth director of Harvard College Observatory (HCO) in 1877, astronomical photography with the famed 38cm (15-inch) Great Refractor had practically become routine. Pickering launched ambitious projects dedicated to observing the sky, both photometrically and spectroscopically. So ambitious was he, in fact, that he established an observatory in Arequipa, Peru, to cover the…

NEWS NOTES ASTRONOMERS DESIGNED the CARMENES program to find Earth-size planets in their stars’ habitable zones. And it has delivered. Since it came online in 2016, it has resulted in a flurry of exciting results The CARMENES consortium is celebrating its first five years of operations with the publication of visible-light measurements for more than 350 stars. In these results, the collaboration announced 33 new planets, 26 confirmed from previous transit surveys and a re-analysis of 17 known planets. Six of the planets are described as “potentially habitable,” an optimistic shorthand meaning they are rocky planets that could host liquid water on their surfaces. All of the planets in the CARMENES sample are within 60 light-years of Earth. The CARMENES instrument itself sits on the 3.5-metre telescope at the Calar…

A SUPERNOVA EXPLOSION recorded by astronomes in East Asia almost 850 years ago has produced an unusual remnant. “I’ve worked on supernovae for [decades], and I’ve never seen anything like this,” says Robert Fesen (Dartmouth College). Fesen presented his observations at the 241st meeting of the American Astronomical Society. In other work presented at the meeting, Bradley Schaefer (Louisiana State University) suggested a possible origin for the centuries-old explosion. Both studies have been submitted for publication. Amateur astronomer (and Fesen’s second co-author) Dana Patchick discovered the nebula in August 2013 in archived images from NASA’s Widefield Infrared Survey Explorer (WISE). Originally, Patchick believed he had found a planetary nebula — his 30th find, hence the name Pa 30 — but later spectroscopic observations revealed that it’s more likely a supernova…

Long after it had taken place, astronomers discovered that a distant Milky Way star had dimmed for seven years. Between 2012 and 2018, the bloated red giant star, located some 26,000 light-years away in the constellation Sagitta, the Arrow, had become more than 60 times fainter (a drop of 4.5 magnitudes) than before. “Stars typically don’t do this,” says Anastasios Tzanidakis (University of Washington), who reported the find at the 241st meeting of the American Astronomical Society. He and colleagues think that the extremely long and deep dimming happened when a slowly orbiting companion, surrounded by a huge disk of absorbing dust, blocked the red giant’s light. The European Space Agency’s Gaia mission first detected the star’s strange behaviour. In 2017, Gaia saw the star (now known as Gaia17bpp) begin…

The beginning of winter this year will see two rather distant comets, discovered as very faint objects in earlier years, coming within visual range of small telescopes. The first of these to have been discovered is C/2020 V2 (ZTF), which was found as long ago as November 2, 2020 by the Zwicky Transient Facility at Palomar Mountain as an object of magnitude 19. It will pass perihelion on March 8 at a distance of 2.23 AU from the Sun, and will become visible from southern latitudes as it emerges from the morning twilight during the latter days of June, drifting slowly southward through Aries. From brightness estimates made by northern observers, it is expected to be about magnitude 10 at that time. October 7, 2021, saw the discovery of a…

OVER THE LAST DECADE, the deep sky astrophotography industry has undergone rapid changes. The growth in the size and sensitivity of digital detectors, dominated until recently by charge-coupled devices (CCDs), fueled the rising popularity of fast, well-corrected astrographs that take advantage of these new detectors. This in turn helped to drive the development of computerised mounts and software to enable these scopes to record deep, colourful images of the universe around us. CCDs had a good run, but inevitably a newer detector emerged and quickly rose to prominence. Complementary metal-oxide-semiconductor (CMOS) detectors, which are less expensive and easier to manufacture, became the dominant detector in popular consumer electronics such as digital cameras and smartphones. The explosive growth in these markets drove trends in the much smaller astronomical community. So, it…

NIGHT LIFE Did you know that on June 30 every year since 2016, the world has celebrated the official UN-sanctioned international Asteroid Day? Yes, it’s true. The aim of Asteroid Day is to raise public awareness of the potential risks posed by an asteroidal collision with Earth — a very worthy cause (look at what happened to the dinosaurs). The special day was initiated some years back by a handful of high profile people, including Apollo 9 astronaut Rusty Schweickart and Brian May (himself an astrophysicist) of the rock group Queen. June 30 was chosen to mark the date of the Tunguska event in Siberia in 1908, the largest asteroid impact with Earth in recorded history. If you’d like to get involved, head to asteroidday.org for lists of events and…

NEWS NOTES HOW MANY STARS can you see at night? According to results from a study appearing in the January 20 issue of the professional journal Science, that number is likely less than it was just a few years ago. To arrive at that conclusion, Christopher Kyba (GFZ German Research Centre for Geosciences) and his collaborators looked to the Globe at Night citizen-science project. Using data reported from users on the ground, the researchers found that the average brightness of the night sky around the globe increased by 9.6% every year between 2011 and 2022. Until now, our best global view of light pollution came from satellite measurements, which had indicated that scattered light was growing on average 2.2% per year between 2012 and 2016. The new result from citizen…

French and German amateur astronomers have discovered a mysterious nebulous arc close to the Andromeda Galaxy (M31), radiating solely the green light of doubly ionised oxygen ([OIII]). Xavier Strottner and Marcel Drechsler analysed images obtained by Yann Sainty and stumbled upon a structure 1.2° southeast of the nucleus of M31. The arc extends over 1.5° and ends close to the nakedeye star Nu (v) Andromedae (the blue star at the top of the photo at left). Sainty used a 107mm Takahashi refractor and a large-format ZWO CMOS camera outfitted with a narrowband [OIII] filter. His wide-angle images added up to a total exposure time of 50 hours. Subsequent images, made with five different setups in France and the United States, have confirmed the arc, now known as Strottner-DrechslerSainty Object 1…

Once we became used to the idea that the Earth orbited the Sun rather than the other way ’round, a way was opened up to measure how far away the stars were… distances that could barely be guessed at. The hunt was on to determine ‘stellar parallax’. The concept was as follows: Every six months, the Earth changed its position by one width of its orbit, thereby shifting the point from which we view the stars. Provided that those stars were not all at the same distance from us, the perspective change would make the nearer ones seem to change position compared to the more distant ones. You can check the method for yourself. Hold a finger upright at arm’s length and compare its alignment with an object in the…

NOVAE EVERY WEEK OR TWO, somewhere in our vast galaxy, an Earth-size star erupts in a nuclear blast. The tiny star’s outer layers explode, unleashing a flash of light we might see as a ‘new star,’ or nova, that shines with the visual luminosity of some 100,000 Suns. Yet the much rarer supernovae get all the press. “Nobody cares about novae, and this is a mistake,” says Francesca Matteucci (University of Trieste, Italy), who studies how stars enrich the cosmos with chemical elements. “I’m convinced that novae are very important” for the creation of new elements, she says. Predictions of nova nucleosynthesis go back nearly half a century. In the 1970s, scientists calculated that novae could mint notable amounts of lithium, a scarce element that’s now critical for modern technology.…

ASTRONOMY HISTORY SIRIUS, BETELGEUSE, Vega and Altair — these names are familiar to anyone interested in astronomy. Yet they had no official status until the 21st century, when the International Astronomical Union (IAU) stepped in. At the end of 2022 the IAU had approved colloquial names for 450 stars, from Absolutno and Acamar through Zubenelgenubi and Zubeneschamali, and 20 more are expected in 2023. Where do these IAU names come from? Only about 20 of the recently approved names are widely used both by professional and amateur astronomers. Professionals denote most other stars with a constellation or catalogue name, plus a somewhat arbitrary sequence of numbers and/or letters. The majority of bright stars are covered by the Greek-letter designations that Johannes Bayer introduced in his 1603 star atlas, Uranometria. Academic…

For a small constellation with no stars brighter than 4th magnitude, Coma Berenices, or Berenice’s Hair, has a lot to offer: one of the finest nearby open clusters; galaxies galore in the Coma-Virgo Cluster; and an easy-to-find globular cluster, Messier 53. First locate 4.3-magnitude Alpha (α) Comae Berenices, the star also known by the beautiful name of Diadem. Almost exactly 1° to the northeast you should spot 8th-magnitude M53 as a round, fuzzy glow. Like all globular clusters, it’s just a blob of fluff, even through my 15× binos. As usual with such objects, the romance is in the mind: taking in the combined light of hundreds of thousands of stars that shine back at us across a distance of 58,000 light-years from the diffuse galactic halo of the Milky…

Most of the carbon atoms in your body were formed deep in the heart of stars two to five times the mass of the Sun. Those atoms are transported by convection up into the stars’ pulsating outer envelopes and then are lost into space. (By contrast, lower-mass stars will hoard the carbon in the core, and those of higher mass will transform it into nitrogen and other atoms.) The presence of carbon-rich molecules and grains in the stars’ gassy envelopes and surrounds is what makes them appear red. The brightness of red stars can be difficult to gauge (due to our eyes’ response to light), but type ‘Sky & Telescope, observing carbon stars’ into a search engine and you’ll find out how. This issue’s stellar target is SS Virginis, a…

Star Adventurer GTi Australian price, mount only: $1,249.99 With optional tripod kit (no pier extension): $1,349.99 skywatcheraustralia.com.au What we like Extremely portable Built-in, illuminated polaralignment scope. What we don't like Camera trigger requires constant wireless connection. Daytime alignment routine difficult to locate. IN RECENT YEARS, Sky-Watcher has rolled out several portable, light-duty mounts for observers on the go. I’ve used a few of them, including the original Star Adventurer mount. I’ve taken it along on several astrophotography adventures, and while it’s a good tracking platform, it’s not suited to carrying small telescopes for astrophotography. Additionally, I often wished it had the Go To control included in the company’s AZ-GTi Alt-azimuth mount. Fast-forward a few years and it seems that Sky-Watcher has listened to its customers with the introduction of a…

FOCAL POINT FIVE YEARS AGO this month, my wife Suanna and I visited the Riviera Maya, a stretch of Caribbean coastline in Mexico’s Yucatán Peninsula. This was our second trip to a Spanish-speaking destination. In fact, it was our 2015 vacation to Puerto Rico that inspired me a aprender un poco de español, or to learn a little Spanish — thank goodness, as it turns out. I brought along binoculars and a tripod to take in various wonders of the sky. To deter mosquitos and avoid airport security issues with liquid repellents, I purchased a keffiyeh, the traditional Arab headdress, to cover my head. Long-sleeved shirts and long pants completed my observing attire. We arrived in Tulum, on the northeast Yucatán shore. After lunch at our ‘luxuriously rustic’ beachfront resort,…