Innholdsfortegnelse for November/December 2019 i Australian Sky & Telescope

NASA’S LATEST exoplanet hunter, the Transiting Exoplanet Survey Satellite (TESS), has found more than two dozen new worlds that have been confirmed in follow-up observations. Scientists shared their findings late July at the mission’s first science conference since the spacecraft’s launch in April 2018. TESS’s goal is to find planets circling bright stars within 200 light-years of Earth. The spacecraft has scanned all 13 sectors of the Southern Hemisphere sky during its first year of operations. So far, TESS scientists have identified 993 planet candidates in 12 of the 13 southern sectors; 271 of them are smaller than Neptune. A total of 28 of these exoplanets have been confirmed as real via follow-up observations. One of the newest systems, anchored by a small, M dwarf star called GJ 357, hosts…

“THERE’S NO SUCH THING AS A GRAVITATIONAL time machine!” belted out a voice across the hall. “You can’t just reverse gravity!” One of us (NIL) was lecturing on work that we and our collaborators had been developing, in which we tried to answer two simple questions: How did the Milky Way form, and why does it look the way it does? Our approach was rooted in observations of what’s termed the local neighbourhood — the immediate (relatively speaking) vicinity of our galaxy, out to some 100 million light-years. But instead of using telescopes, we were building galaxies in computers and then running time forwards and backwards to see how their appearance changed. The lecture was in Tallinn, Estonia, at a meeting dedicated to the 100th birthday of Yakov Zeldovich, a…

This November and December the main meteor showers will be hampered by rather poor lunar conditions. The Leonids’ peak on November 18 will be under a waning gibbous moon, while the Geminids, usually the most productive shower, will reach its peak just after full Moon. That peak will be on December 14, at which time the Moon will located in the constellation Gemini itself, only a few degrees south of the radiant. Nonetheless, thanks to increased activity seen in recent years, observations are encouraged irrespective of lunar interference. On the mornings of the 14th and 15th you might see around 20-plus Geminids if you can shield yourself from the Moon’s light (eg. place yourself in the shadow of a house, with the Moon obscured). With the Leonids and Geminids washed…

If you undertake an observing commitment of some sort you will get more from your hobby. This month’s proposed commitment is regular observation of the bright semi-regular variable star W Orionis, and the payoff will be enjoying this famous and ancient constellation more often. However masculine the myth of Orion the Hunter may be, as has so often been the case in variable star astronomy, it has been women who have done the science. One of Scottish astronomer Williamina Fleming’s many papers published in 1895 announced the discovery by Evelyn Leland — a US astronomer and one of the famous ‘Harvard computers’ — that the star known as BD–00°939 is variable. The variable star designation ‘W’ followed almost immediately. Visually, W Ori varies from magnitude 5.5 to 6.9 over a…

Amateur astronomers on each side of the Tasman Sea will have a solar spectacle of their own over the next couple of months. In November, New Zealanders will be treated to a transit of Mercury across the face of the Sun, while observers in much of Australia will witness a partial solar eclipse in December. Before going any further, it is incumbent upon me to reiterate the standard warning about solar observations — staring at the Sun with the naked eye can damage your eyesight; using optical aid such as a telescope can instantly blind you. There are only two safe ways to observe the Sun — the first is to the use the projection method; the second is to use a professionally manufactured solar filter or solar telescope. Homemade…

MY BEST CHANCE TO OBSERVE the remarkable Messier 77 came in October 2016 when I had four nights to observe it through one of the largest amateur telescopes in the world, Jimi Lowrey’s 1.2-metre (48-inch) f/4. It was the next object on my observing list after Arp 284 and the quasar 2333+019. Jimi and fellow observer Steve Gottlieb had graciously stepped aside to give me 30 minutes of uninterrupted observing and sketching time on the 1.2-m, and to repeat this privilege for three more nights. Thanks to them, I was like a kid in a lolly shop! That makes M77 the only object I’ve had more than a few minutes to sketch with the 1.2-m. The detail I was able to see with a combined two hours of eyepiece time…

AMATEUR ASTRONOMERS NEED dark skies and a minimum of stray light. Yet many of us live in metropolitan areas with their light-polluted skies. Observing closer than one might wish to people and their homes can produce extra safety concerns for the stargazer. As we’re all aware, unfamiliar noises or suspicious figures in the dark can result in calls for the police to investigate. Amateur astronomers pose a special challenge to law enforcement because they work at night and engage in practices that might be unexpected and unclear to non-astronomers. No human being is really good at rapidly assessing ambiguous situations in the dark, not even a police officer. I might best sum up the following pointers for amateurs with this overall recommendation: Make your activity as clear as possible. Some…

ON AUGUST 30, 2019, Ukrainian amateur astronomer Gennady Borisov, using a newly built 0.65-metre telescope, discovered a rather inauspicious-looking 18th-magnitude comet that has actually turned out to be of remarkable interest. Orbital computations reveal it to be travelling through the Solar System on a strongly hyperbolic orbit, having an eccentricity of around 3.4. Eccentricity indicates whether an orbit is circular, elliptical, parabolic or hyperbolic. C/2019 Q4 (Borisov) thus becomes the second interstellar visitor to have been found during the past two years. The first such object of interstellar origin found — given the name ‘Oumuamua and a catalogue number 1I/2017 U1 — did not reveal any cometary activity, but mysteriously displayed clear non-gravitational acceleration as it moved away from the Sun. According to cometary expert Zdenek Sekanina, the most reasonable…

A NEW STUDY of a special class of red giant stars fuels a dispute about the rate at which today’s universe is expanding. The universe’s expansion rate has changed throughout time. However, the crux of an ongoing debate is that observations of the early universe predict a current expansion rate that doesn’t match measurements of galaxy recession speeds. Observations of the cosmic microwave background (CMB) pin today’s expansion rate, also called the Hubble constant (H0 ), between 66.9 and 67.9 km s-1 Mpc-1 . However, measurements of galaxies’ recession speeds — based on so-called standard candles such as Cepheid variable stars — find H0 to be significantly higher, between 73 and 76 km s-1 Mpc-1 . Now, Wendy Freedman (University of Chicago) and colleagues have employed red giant stars —…

FOR ALL THE TIME THAT HUMANITY has spent gazing at the stars, we still know shockingly little about what they actually look like. Even with the biggest telescopes, nearly every star except our Sun appears as a speck of light, their surfaces hidden from view. Some stars, however, are ready for their close-up. At the southern tip of the constellation Andromeda sits Zeta Andromedae, a moderately bright orange giant that is now part of an elite club: It is one of a handful of stars to have its surface mapped by astronomers. In 2016, Rachael Roettenbacher (Yale University) and colleagues revealed the star’s portrait in new detail: a patchy orb 15 times as wide as the Sun and slathered in gargantuan dark spots. Zeta’s portrait isn’t like the gorgeous space…

ASTRONOMY 2020 YEARBOOK Every astronomer needs the Astronomy 2020 yearbook. Australian-produced, it is packed full of essential information to plan your observing sessions. Included is a complete guide to what’s visible in the night sky, including Moon phases, planets, comets, eclipses and meteor showers, plus star maps and a month-by-month viewing guide. Available mid-October — pre-order now. $29.95 plus postage & handling 2020 AUSTRALASIAN SKY GUIDE An ideal yearbook for beginners, the easy-to-read 2020 Australasian Sky Guide provides a month-by-month guide to what can be seen with the naked eye, along with lots of interesting facts and figures, detailed descriptions of special astronomical events, and planetary data. $16.95 plus postage & handling ASTRONOMY 2020 CALENDAR Featuring amazing celestial photography from the annual David Malin Awards, the Astronomy 2020 Calendar provides…

To see a World in a Grain of Sand And a Heaven in a Wild Flower Hold Infinity in the palm of your hand And Eternity in an hour —William Blake, Auguries of Innocence, c. 1807 Avery small meteoroid could be considered both a “Grain of Sand” and a “World” (it has its own orbit around the Sun). The purple I saw in one of the components of a double star once leaped out at me the following day from a wild violet I saw blooming by the roadside — a hue of “Heaven” in a “Wild Flower”. But if we’re looking for astronomical validations of Blake’s lines above, what about “Eternity in an hour”? That’s what I’ll be canvassing in this issue’s column — along with an astronomical connection…

On the night of September 23, 1846, German astronomer Johann Gottfried Galle called out the configurations of stars in the field of view of the 9-inch refractor at the Berlin Observatory, while an assistant, Heinrich Louis d’Arrest, checked them on a map. Just after midnight, Galle called out that a star of 8th magnitude was in a particular location. D’Arrest immediately exclaimed: “That star is not on the map!” That “star,” of course, was a new planet, Neptune. Although a giant planet with an equatorial diameter almost four times larger than Earth’s, it appears almost starlike through small telescopes. It takes a magnification of 200x or so to clearly resolve its pale blue disk. The smallness of its disk, so discouraging to the casual viewer, proved an asset to a…

AUSTRALIA HAS HAD ITS SHARE of total solar eclipses, arguably the most spectacular of all natural phenomena. There was one in the far south west of Western Australia in 1974; Mt Gambier, across Victoria and into far southern New South Wales in 1976; Ceduna and the South Australian desert in 2002; and Arnhem Land and far North Queensland in 2012. A forthcoming eclipse will clip the North West Cape area in Western Australia on April 20, 2023, and the much-awaited eclipse of July 22, 2028, will race diagonally across Australia from the Kimberley to Sydney. Medium rare Total solar eclipses occur roughly every 18 months. Why are they relatively rare? Well firstly, the Earth, Moon and Sun have to line up. But the Moon’s orbit is inclined by five degrees,…

John Drummond is one of New Zealand’s best-known amateur astronomers. A past president of the Royal Astronomical Society of New Zealand (RASNZ), he has long been active in scientific work, including astrometry of newly discovered asteroids and comets. In recent years he has helped discover around 20 exoplanets for the Ohio State University MicroFUN research team. At the end of 2019 he will be starting an astrotourism business, Gisborne Astro Tours. What got you into astronomy? When I was about 10, my mother and I were walking home from the swimming pool at dusk. Mum looked up and saw the Pot (in Orion) and said, “Look John, there’s the Pot,” and pointed it out to me. Once I saw it, something went off inside me — the universe poured into…

THE SPEKTRUM-RÖNTGEN-GAMMA (Spektr-RG) satellite, a long-delayed and much-modified X-ray astronomy package, launched successfully from the Baikonur Cosmodrome in Kazakhstan on July 13. Once Spektr-RG reaches a stable solar orbit 1.5 million kilometres from Earth, at Lagrangian point L2 , two telescopes aboard will commence mapping the X-ray sky. The first is the German space agency’s Extended Röntgen Survey with an Imaging Telescope Array (EROSITA); the second is the Russian-built Astronomical Röntgen Telescope – X-ray Concentrator (ART-XC). Each telescope contains multiple modules of concentric mirror pairs. X-rays will skip off these mirrors at grazing incidence angles, like smooth pebbles off a pond, before coming to a focus on the detectors. EROSITA’s vision is the sharper, with 18-arcsecond resolution, and its wide field of view will enable it to survey the full…

The Milky Way has a few main arms and several smaller ones. Since this diagram’s creation in 2008, astronomers have detected the New Arm, probably an extension of the Scutum-Centaurus Arm. The Perseus Arm has proved patchier (sparse sections hazed out) and the Local Arm brighter and longer — observers suspect it might hook up with Perseus near 70° galactic longitude (dotted line). Locations of familiar citizens of the Perseus, Local, Sagittarius and Scutum-Centaurus arms are highlighted.…

Instead of snapping photos of stars, an interferometer records the interference pattern created by combining the light received by two or more telescopes. But this process only works if the light has travelled the same distance. 1. Star Light waves travel from the star to the telescopes. 2. Geometric delay The light has to travel farther to reach one telescope than the other. The distance depends on the star’s location in the sky. 3. Adjustable delay lines Astronomers send the starlight through delay lines whose lengths are continuously adjusted to compensate for the arrival delay. 4. Wavelengths aligned Having now traveled the same distance, the starlight is combined, creating interference fringes. The fringes’ amplitude encodes information about the star’s size, shape, and surface patterns.…

I can still remember my first binocular views of the sky. As a young teenager I would set up a chair in the front yard of our family home, and I would scan the skies with my mother’s 8×30s. I didn’t have much of a clue of what I was looking at, other than there were stars and what looked like groups of stars and some other fuzzy stuff scattered across the sky. At first, I mainly concentrated on the view to the south, as I had just learned how to find south using the Cross. But when I pointed the binoculars to the north, I discovered all sorts of new things. It was coming into summer, and some pretty speccy constellations seemed to be up and about. I didn’t…

The finest dark nebulae for telescopes are those that are silhouetted against a bright background, such as the striking, chevron-shaped dark lane within the high surface brightness Carina Nebula, or those silhouetted against the Milky Way’s brightest star clouds. One example of the latter is Barnard 92, a foreground object in front of distant M24 (the Small Sagittarius Star Cloud). Dark nebulae are also detectable in much fainter portions of the Milky Way, but while they may look obvious on images, they’re fairly challenging at the eyepiece. Since the Milky Way background is too faint visually to silhouette the dust clouds, they can only be detected by the paucity of faint stars in comparison with the rest of the field or surrounding fields. But note that there may not be…

MANY AMATEUR ASTRONOMERS devote themselves to semi-professional astronomical research, and in some cases collaborate with professional astronomers in investigations of great importance. Often, standard backyard astronomical equipment is perfectly adequate for the job. But sometimes, higher-quality (and expensive) equipment is needed, or access to professional facilities might be required. There are several funds available to help amateurs cover the costs of this work. One of them is the Edward Corbould Research Fund (ECRF) of the Astronomical Association of Queensland (AAQ). History of the fund The AAQ is a Brisbane-based organisation of amateur astronomers that has a long history of astronomical research, including: visual and photometric studies of variable stars; visual and photometric lunar and asteroid occultation observations; studies of double and multiple stars; spectroscopy of long-period variable stars; and astrophysical…

As described on page 55 of this issue, Australasian observers will be treated to some solar spectacles in the last two months of 2019 — a transit of Mercury on November 12 (visible from New Zealand but not Australia) and a partial solar eclipse on December 26 (visible from parts of Australia but not New Zealand). If you intend to catch either of these events, please remember to use safe solar observing methods. Around the region there are plenty of star parties and astronomy conferences coming up, as listed on this page. One of them is the VicSouth Desert Spring Star Party, held at the Little Desert Nature Lodge in the Little Desert National Park approximately 4.5 hours from both Melbourne and Adelaide. This is a very dark site about…

BRIDGING THE SKY Eugene D’Orsogna & Richard Triglavcanin Eugene and Richard travelled to the Ringa Railway Bridge, 1.5 hours’ drive north-east of Perth, to produce this shot… which is a composite of 20 frames, each of which comprised multiple shots of their own. The lights of Perth can be seen behind the trees on the left. A YOUNG STAR Allegra Kennedy-Scott This image showing the International Space Station and the Moon (with Saturn, top, and Altair, lower left, just visible) was taken by Allegra, who is six years old, with only a little help from dad, Daniel. Allegra chose the 4-second exposure time, aimed the Panasonic DMC FZ5 camera and took the photo. NEBULA NEIGHBOURS Justin Young The Lagoon Nebula and Trifid Nebula float among the stars of Sagittarius. For…