Innholdsfortegnelse for April 2023 i Australian Sky & Telescope

RESULTS FROM A COMPLEX new analysis support cosmologists' suspicions that something is missing from our understanding of the universe. For the most part, our standard theory of cosmology fits observations like a glove. With just a handful of ingredients, scientists can explain the patchy pattern of the cosmic microwave background (CMB) — the relic radiation from the universe's primordial age — and how the nearly uniform soup it came from transformed into the Swiss cheese of galaxy clusters and cosmic voids we see today. But some nagging problems remain. The most touted is the Hubble tension, a discrepancy between how fast the universe appears to be expanding today and how fast it ‘should' be expanding, based on what we see in the early universe. But there's another, more subtle discrepancy:…

SCIENCE & SOCIETY THE BOEING 747 LIFTED TOWARD THE SKY, taking off at a hefty pitch and shoving Jim De Buizer back in his seat. The goal was to reach 35,000 feet — and fast. At that altitude, the pilots would ease up on the throttle and open a 4-metre-wide door in the side of the fuselage. It wasn't a death wish: They were exposing a 19-tonne, 2.5-metre telescope to the starry sky. It was May 26, 2010, the first night observing with the world's largest airborne telescope — otherwise known as the Stratospheric Observatory for Infrared Astronomy, or SOFIA — and De Buizer had goosebumps. “You're taking off to get the first photons for an observatory ever,” De Buizer says. “And that's just pure adrenaline that whole entire time.”…

EVENINGS WITH THE STARS Corvus, the Crow, is one of the classic signs of autumn for evening skywatchers. What the constellation lacks in brightness, it makes up for with a compact and eye-catching geometric shape delineated by four 3rd-magnitude stars. The boxy formation is rendered even more noticeable by its proximity to Virgo's 1st-magnitude Spica, which is roughly 15° northeast of the Crow. The main pattern of Corvus is shown on our centrespread map (pages 42 and 43), positioned in centre, just west of the meridian — the imaginary line that connects north to south and passes directly overhead. The constellation's main pattern is formed (working clockwise from upper left) by connecting the stars Algorab, Gienah, Minkar and Kraz. These are also known as Delta (δ), Gamma (γ), Epsilon (ε)…

COMETS Although fading rapidly now, comet C/2022 E3 (ZTF) became an easy binocular, and marginal naked-eye, object during February and even briefly became a news item. Fortunately, the news coverage of its appearance was quite modest, unlike some of the earlier comet mass media coverage fiascos such as Kohoutek way back in 1973 or ISON just ten years ago. Nevertheless, it is a little unfortunate that it was promoted as the “green comet” and even described in places as “a rare green comet”. If novice observers expected to see something a bit like a celestial traffic light, I fear that they would have been disappointed! The green hue of this object — seen so dramatically displayed in photographs — was not apparent to the naked eye through the eyepieces of…

AFTER AN AMATEUR ASTRONOMER has been observing for a while, setting up their telescope each night and tearing it back down in the wee hours, their mind often turns to building a permanent observatory. One of the most common types is the shed with a roll-off roof, wherein the top of the building slides on rails onto a support structure at the end of the building, leaving the sky open for astronomy. Not surprisingly, rolling off the roof leads to several difficulties. First off, the building needs to be custom-made with a detachable roof. The outside support structure has to be strong enough to hold that roof, which means a pretty robust framework that's equal in size to the building. Then there's sealing it against the elements and against intrusive…

PUBLIC ASTRONOMY READERS' GALLERY A few years ago a group of residents in Orange, NSW, had a vision to create an eduvtion and tourist faciltiy to comp;ement and enhance the astronomical heritage of the region. The Central West of NSW was already well represented with telescopes, clear dark skies and a longstanding astronomical society, so they proposed establishing a digital planetarium within the town. Although the proposed project concept has changed quite a few times over the years — sometimes growing in size, sometimes shrinking — it has now finally become part of a joint facility with the Orange Regional Conservatorium of Music. It turns out the Conservatorium was also looking for a new home, as its current premises are not purpose built and are in need of repairs. Both projects…

NEWS NOTES THE DISTANT DWARF planet 50000 Quaoar appears to have a ring that spans far beyond where it ought to be stable. “That is not where it was supposed to be,” says Bruno Morgado (Federal University of Rio de Janeiro), lead author of a team of 59 professional and amateur astronomers who have reported the discovery. At 1,110 km in diameter, Quaoar is one of the largest objects known in the outer Solar System. Its single moon, named Weywot, spans about 160 km and was discovered in Hubble images in 2007. But the first signs of material around Quaoar didn't come until 2018; even then, evidence was insufficient to call it a ring, says Morgado. He began studying Quaoar in 2020 with the European Space Agency's CHEOPS space telescopes.…

ASTRONOMERS USING the James Webb Space Telescope (JWST) have confirmed the most distant galaxies ever observed. Some formed when the universe was just 2% of its current age. The results, based on detailed spectroscopic measurements, provide concrete distances to galaxies first revealed in Webb images. “It was crucial to prove that these galaxies do, indeed, inhabit the early universe,” says Emma Curtis-Lake (University of Hertfordshire, UK). “It's very possible for closer galaxies to masquerade as very distant galaxies.” Curtis-Lake is part of the JWST Advanced Deep Extragalactic Survey (JADES) group, which has been given a month's observing time spread over two years to take spectra of distant galaxies. The first part of this effort saw them observe an area of the sky in and around the famous Hubble Ultra Deep…

THE BLUE MARBLE 0.2% Fraction of Earth's mass that is water ON DECEMBER 6, 2020, dozens of scientists and technicians from the Japanese space agency, JAXA, roamed the South Australian desert, waiting for a sign from above. They were looking for a bright streak of light that would cross the sky, bringing with it new knowledge about the origins of our Solar System. It arrived just before dawn, accompanied by a radio signal that revealed the location of the treasure left behind: a capsule filled with about 5 grams of the near-Earth asteroid 162173 Ryugu, recovered by the Hayabusa2 robotic spacecraft more than one year earlier and dropped as the craft whizzed by Earth. Ryugu itself might only be 9 million years old, but it's made of debris from a much…

BINOCULAR HIGHLIGHT Our targets this month are the open clusters M46 and M47 in the constellation Puppis, the Stern of the celestial ship Argo Navis. There are several ways to get to the clusters: my favourite is to go east from the Great Dog, Canis Major. Starting at Gamma (γ) Canis Majoris at the back of the Dog's head, look for a long, flat parallelogram formed by it and HD 56405, HD 57478 and HD 60414 — it'll point you to M46 and M47. The two Messier clusters are a classic study in contrasts: the 6.1-magnitude M46 is a dense swarm of faint lights that blend into a misty glow at magnifications less than 15x, whereas 4.4-magnitude M47 presents itself as a splashy, irregular blast of brighter stars, like a…

Variable star observers use standardised star charts to estimate stellar brightness, for many reasons. For one, it gives consistent measures. And secondly, if the sequence of comparison star magnitudes used is identified, a data point can be re-worked if better photometry becomes available… even after centuries. Indeed, a comparison star may itself turn out to be variable. For instance, Stan Walker of the Variable Stars South (VSS) group, along with B. Marino of the Auckland Astronomical Society, discovered the variability of this issue's target, QZ Carinae, while investigating discordant observations of Eta Carinae. In 1972, Walker and Marino classified it as an Algol-type eclipsing binary that ranged from magnitude 6.2 to 6.49 over a period of almost exactly six days. So, give it its own observing program and the case…

With its dense clustering of bright galaxies, sprinkled with multiple Messier objects, the central part of the Virgo Cluster (sometimes called the VirgoComa Cluster) is familiar territory for most deep sky observers. Less travelled, perhaps, are the rich galaxy-hunting grounds of southern Virgo. Bracketed between M61 in the north and M104 in the south is a patch of sky that, while less densely packed than ‘downtown Virgo,' is still chock-full of worthy targets. Most of the galaxies here belong to the Virgo II Groups, which are alternately called the Virgo II Cloud, the Virgo Southern Extension or the Virgo S Cloud. This vast region of space, off the southern edge of the Virgo Cluster, contains about 100 galaxy groups and individual galaxies. At least 50 of them are brighter than…

NEWS NOTES THE GRAVITATIONAL-WAVE signal known as GW190521 represents the collision of a roughly 90-solar-mass black hole with a 65-solar-mass one. The event has long excited astronomers, because exploding stars shouldn't create black holes with masses between roughly 50 to 120 Suns. With only about 0.1 second of data, researchers have fit a whole slew of solutions to GW190521's signal. Astronomers initially settled on describing GW190521 as the merger of a pair of big black holes orbiting each other at wonky angles, causing the plane of their nearly circular orbit to wobble around. But others have instead considered highly elongated orbits, head-on collisions, or proposed that the mass estimates are just wrong. Publishing in Nature Astronomy, Rossella Gamba (Friedrich Schiller University Jena, Germany) and colleagues threw their hats into the…

THE BIGGEST PLANET in the Solar System now has the largest family of moons. Since December 20, the Minor Planet Center (MPC) has published orbits for 12 previously unreported moons of Jupiter. More publications are expected, says Scott Sheppard (Carnegie Institute for Science), who recently submitted observations of the Jovian system taken between 2021 and 2022. The discoveries bring the list of Jovian moons to 92, a hefty 15% increase on the previous tally of 80. The MPC's orbital calculations confirm the new objects are in orbit around Jupiter. Other data from Sheppard's observations even enabled recovery of the last ‘missing' Jovian moon, S/2003 J 10; the newest observations extended the track of its orbit to 18 years. The new finds put Jupiter's lunar family count well ahead of Saturn's…

As with so many of the pioneering Greek astronomers, we do not know much about the life of Eudoxus. We have only fragments of his story, though we know he lived in the fourth century BCE, being born and eventually dying in the city of Cnidus on the southwest cost of Asia Minor, now in Turkey. His name means ‘being of good reputation,' and he certainly made major contributions in astronomy, mathematics and ethics in his time. None of his own writings have survived; we know of his work only through the writings of others, including Aristotle. In astronomy, his reputation came through his explanation of the complex motions of the ‘planets' (which then included the Sun and the Moon) against the background of the ‘fixed stars'. For example, astronomers…

GALACTIC PINWHEELS SEEN THROUGH A TELESCOPE, spiral galaxies are surprisingly subtle — faint and fuzzy things. Yet the structure they possess captures the viewer's imagination. Whether you glimpse the grand swirls of the Whirlpool (M51) or the frizzy petals of the Sunflower (M63), the patterns become all the more incredible when you realise they're shaped by the multitudinous tugs and nudges among billions of stars. These simple individual interactions add up to farreaching forces that have proven difficult to untangle. Astronomers noticed galactic spirals even before they knew what galaxies were, but sound ideas explaining the pattern's origin have come only in recent decades. Now, even though astronomers agree on the primary mechanism that propagates a spiral pattern, they still argue about what sets it all in motion. What is…

A poorly focused lens can ruin an otherwise perfect astrophoto. Stars become bloated blobs (often surrounded by unsightly colour fringes) and fine details are lost. Imprecise focus also means longer exposures are required to record faint objects. And none of these problems can be easily fixed during post-processing — that's why it's important to get everything right under the night sky. Your camera's autofocus system works well in bright daylight but will struggle to lock in focus in dim conditions. In fact, some excellent lenses are fully manual and lack autofocus capabilities. For best results, you need to manually focus with the aid of a feature called Live View. It's included in almost every digital camera sold these days. This option enables you to zoom in and examine a highly…

The 2023 Central West Astronomical Society (CWAS) AstroFest will be held over the weekend of July 22–23, comprising a one-day conference and a program of associated activities. The conference will be held at the Parkes Services Club (in the Starlight Room, no less!) on the 22nd and will feature a series of lectures from guest speakers who will provide insights into various aspects of modern astronomy. On the 23rd, the action will move to the CSIRO Parkes Observatory Visitors Centre for a program of daytime astronomy and talks. Visit cwas.org.au/astrofest for more details. Along with the AstroFest comes the annual CWAS David Malin Awards, an astrophotography competition open to all astrophotographers in Australia. The 2023 Awards will be presented at a special ceremony held during the conference on July 22.…