Innholdsfortegnelse for July 2023 i Australian Sky & Telescope

NEWS NOTES FOR DECADES, scientists have both suspected the existence of and searched for active volcanoes on Venus. Its surface is geologically young, perhaps only tens of millions of years old, meaning that lava flowed recently on our sister planet. Now, a new analysis of three-decade-old radar images from NASA's Magellan orbiter has resulted in a definitive detection: In 1991, there was volcanic activity on the surface. “We've never had evidence as strong as this,” says Paul Byrne (Washington University in St. Louis), who was not involved with the study. Magellan orbited Venus from 1990 until 1994, when it plunged into the hellish atmosphere. But before the mission's end, the spacecraft's synthetic aperture radar mapped almost all of the Venusian surface, showing features as small as 120 metres across. These…

STELLAR HISTORY SEE ANYTHING AMISS in this century-old excerpt from the July 1923 issue of this magazine? As many of us finish work on our farms, dusk summons a stellar ruby to the southern sky: beautiful Antares, the ruddy heart of Scorpius, shining over fields and farmhouses. A red giant, Antares is young, a large cool star that has recently emerged from the frigid depths of space. When you gaze at this brilliant red star, you're seeing our own Sun as it looked long ago, shortly after its birth. Three problems: First, this magazine didn't exist in the 1920s; the excerpt is fictitious even though it reflects the thinking of the time. Second, astronomers now classify Antares not as a red giant but as a red supergiant, a word that…

While I was reading our feature article ‘The little stars that can’ (AS&T: May/Jun 2023, p.18) — which tells the story of novae and their importance to our world — an email alert arrived with news of a bright transient in Scorpius. Discovered by Andrew Pearce from Perth, it was later confirmed as Nova Scorpius 2023 (aka V1716 Sco). How did he discover it, and can we still see it? Pearce started his ‘nova patrol’ in 2021 using a second-hand Canon EOS 800D DSLR camera with an 85mm f/1.2 lens, mounted on a nontracking tripod. Even though he has light polluted skies, on most clear nights he surveys the Milky Way from Canis Major to Aquila, and can detect transients down to magnitude 10.5 or so. He has found four…

REMOTE GLOBULARS WHILE OUR UNDERSTANDING of the origin of the Milky Way's globular clusters is still shrouded in mystery, that's not the case with their knowing distances from Earth. In fact, thanks to the most recent data from the European Space Agency's Gaia spacecraft, we know how far away they are to within an accuracy of a few percent. The data reveal that roughly three-quarters of all known globulars in our galaxy are less than 50,000 light-years from us. In our last issue, Contributing Editor Ted Forte took readers on an extensive tour of these ‘star cities’ (AS&T: May/Jun 2023, p. 56). He visited a bunch globular clusters, with the most distant being about 50,000 light-years away. This month's tour is going to be different since the nearest ones we'll…

BIG DETECTOR Camera manufacturer QHYCCD announces a new medium-format model for deep sky imaging. The QHY461 PH camera (US$10,800) is designed around the extremely sensitive Sony IMX461 BSI CMOS detector, which has a 11,760 x 8,896 array of 3.76-micron-square pixels measuring 44 x 33 mm. This 102-megapixel, back-illuminated sensor provides native 16-bit A-to-D conversion on chip. Its dual-stage, thermoelectric cooling produces stable operating temperatures of as much as 35°C below ambient temperature. The camera body has a built-in dew heater around the optical window to prevent condensation. Its 77mm aperture mates directly with the company's CFW3XL filter wheel. Each camera comes with a 2-metre USB 3 cable and CD containing the camera drivers and control software. QHYCCD qhyccd.com AUSTRALIAN-MADE ASTROGRAPH Astroworx has released a 25cm (10-inch) f/4 carbon-fibre Newtonian astrograph…

PRO-AM COLLABORATION We know that rings encircle the giant planets in our Solar System — Jupiter, Saturn, Uranus and Neptune all orbit the Sun accompanied by an entourage of rings. We also know of more than 5,000 confirmed exoplanets today, many of which are giants. It follows that they'd have rings, too. But exoplanets are many lightyears away and hard to find in their own right. If they're so tough to spot, how can we go about finding their rings? Matthew Kenworthy (Leiden University) is taking a unique approach to this task. And he has called upon the amateur community to help him out. Big, big rings. While examining archival data of the young star J1407 (short for 1SWASP J140747.93394542.6), Erik Mamajek (University of Rochester) and his graduate student at…

IN 2019 ASTRONOMERS found something strange — a gas giant orbiting a star with only a tenth the mass of the Sun, an M dwarf dubbed GJ 3512. The discovery was an anomaly, because there shouldn't have been enough material around the star to form such a big planet in the first place. Now, Edward Bryant (University College London) and collaborators have identified other possible gas giants orbiting low-mass stars. The 2019 discovery, it appears, is not unique and instead calls standard planet-formation theories into question. In the core accretion scenario, planetesimals first collide and stick together, becoming rocky cores the size of a few Earth masses, then they start to gather large amounts of gas around themselves. This theory works well in simulations of most star systems, including our…

When SpaceX launched its first Starlink satellites in 2019, and astronomers realised just how bright they would be, CEO Elon Musk glibly tweeted that telescopes would simply have to go to space. Only it turns out that, depending on their orbits, space observatories aren't safe from light pollution either. A new accounting of satellite trails in Hubble Space Telescope images, published in the journal Nature, shows that the chance of satellites affecting an image has doubled to 6% over the past two decades, largely before the Starlink era. The study serves as a baseline for comparison against future studies, in which the impacts of Starlink and other satellites will become more noticeable. The team, led by Sandor Kruk (Max Planck Institute for Extraterrestrial Physics, Germany), started with comments on an…

Even though totality was to last for only about 60 seconds, April 20's hybrid solar eclipse was witnessed by thousands of intrepid eclipse chasers who travelled to view the event under the remote but clear skies on Western Australia's coast near Exmouth. Here, we've compiled some of the best shots taken by a number of Aussie astrophotographers who were lucky enough to be there. “When totality arrived, the light seemed to go like someone pressed a switch,” said Michael Goh, who took this sequence from close to Exmouth.…

Late July always brings two fine meteor showers for southern, observers; the Southern DeltaAquariids and the Alpha Capricornids. Unfortunately, this year both showers will be affected by the Full Moon on August 1, with the lunar light drowning out the fainter meteors. The Southern Delta-Aquariids is active from July 12 to August 23, with the maximum overnight on July 30/31. The declination of the shower's radiant (-16°) makes it well placed for viewing from Australasia. The zenithal hourly rate (ZHR) is usually listed as being 25, but brief outbursts have been known. This shower's meteors are generally on the faint side, which makes it all the more disappointing that moonlight will interfere. Still, it's definitely worth a try. Alpha Capricornids, on the other hand, are often quite bright, and are…

Nothing screams minor planet like having a number in front of your name. We rarely think about it, but Pluto's complete astronomical designation is 134340 Pluto. Although some still prefer to consider it a planet, since 2006 the distant world has been categorised as a dwarf planet. The International Astronomical Union (IAU) defines a dwarf planet as a “an object in orbit around the Sun that is large enough to pull itself into a nearly round shape but has not been able to clear its orbit of debris”. When Clyde Tombaugh discovered Pluto in 1930, it stood alone. Calling it a planet made sense then, but now it has plenty of company in the outer Solar System's Kuiper Belt, where maybe up to 200 dwarf planets reside. In similar fashion,…

IMAGE PROCESSING Deep sky astrophotography is a hobby that requires mastering several skillsets. The mechanical knowhow needed to record good deep sky data doesn't necessarily overlap with the skills required to turn all those data into beautiful images. In fact, these days, you don't even need to acquire your own image data — you can buy time on a finely tuned telescope located under dark skies. You can even work with images acquired by NASA observatories like the James Webb Space Telescope. But regardless of where and how our photons are gathered, it takes powerful image-processing software — and an understanding of how to use it — to turn those ones and zeroes into dazzling portraits of nebulae, star clusters, galaxies and the occasional bright comet. I have some good…

ONE OF THE MOST FRUSTRATING aspects of wearing glasses is that you have to take them off to look through most eyepieces, yet you have to put them back on to look through a Telradstyle finder. On-off, on-off all night until you want to throw the glasses away and scan the sky at random. Retired optical research engineer Bob Schalck reasoned that if he could put the correction on the Telrad instead of on his face, he could eliminate the swapping on and off and enjoy observing without distraction. Bob is nearsighted by 3 diopters. Diopters are how opticians measure a lens’ focal length, and it's a simple conversion to more astronomer-friendly units: Divide diopters into 1,000 mm to get the focal length in mm. So 3 diopters of nearsightedness…

Seven planets circling a red dwarf star 40 light-years away might offer one of our best shots at observing potentially habitable worlds. But the innermost planet, TRAPPIST-1b, has shown its true colours to the James Webb Space Telescope (JWST): Astronomers already knew it was located too close to the star to be habitable, but new observations reveal that TRAPPIST-1b is too hot to even have an atmosphere. Thomas Greene (NASA Ames Research Center) and colleagues report in the journal Nature that a series of observations that caught the planet as it passed behind its star from our point of view. During five such secondary eclipses, JWST measured light both from the star itself and from starlight reflected off the planet's dayside, giving a measure of the planet's temperature: between 480…

Astronomers have discovered that some of Earth's water could predate the Sun. Observing a planet-forming disk around the infant star V883 Orionis, John Tobin (National Radio Astronomy Observatory) and colleagues report in the journal Nature the chemical composition of its water vapour. Water is arguably Earth's most distinctive feature, but where and how it formed is still up for debate. The team's observations — made with the Atacama Large Millimeter/submillimeter Array in Chile — provide a missing link, showing that habitable planets can inherit a portion of their water chemically unchanged from the interstellar medium. Most water molecules are a marriage of two hydrogen atoms and one oxygen atom. Yet sometimes one of the hydrogen atoms is replaced by an atom of deuterium — an isotope of hydrogen that contains…

We commonly call the period of Western European history from the fall of the Roman Empire in the 5th century CE to the first stirring of the Renaissance in the 15th century, the Dark Ages, as if nothing of interest was going on in science or in other intellectual pursuits. Knowledge, of astronomy and other sciences, was certainly growing elsewhere, such as in India and the Middle East, but what about in Western Europe itself? Wasn't anybody asking questions at all? Yes, they were. The light was not entirely out, though it was much dimmed. The people who pursued such interests were mostly monks, living in monasteries. They were the only ones with any significant education. While mostly concerned with theological matters, they had time to pursue more philosophical issues,…

UNEXPECTED TAILS WHAT'S THE DIFFERENCE between a comet and an asteroid? This seems like a simple question. Comets are familiar to most people as celestial objects with a fuzzy head and often one or more long, sweeping tails — features that astronomers collectively describe as ‘activity’. Even those who have never seen a comet with their own eyes have probably seen this activity in glossy photos of comets in magazines such as the one you're reading right now, or in popular media and movies. In 1950, Fred Whipple described comets as “dirty snowballs,” referring to the mixture of icy and non-icy material that makes them up — which still largely captures how astronomers view comets today. This view naturally and intuitively explains the ‘active’ appearance of comets, which arises when,…

EVENINGS WITH THE STARS Which version of Scorpius will you see tonight? Of course, there's only one Scorpius, the Scorpion, but it presents several different appearances. It's well known as a magnificent constellation with its heart afire with red supergiant Antares, and its long double-twisted length marked with numerous bright stars. But how much of Scorpius can be seen depends on how high it rises in your sky. Southern observers it all. The fishhook pattern of Scorpius encompasses a vast, north-to-south swath of the celestial sphere. Its main stars are arrayed from a declination of about -20° all the way down to -43°. For observers at the populous latitude of 35° south, the constellation's stars reach high into the sky on winter nights. But for the many observers in Canada,…

COMETS Two comets that were expected to come within the magnitude range of backyard telescopes in June, will continue their brightening trend during July. Emerging from the morning twilight as it recedes from its May 8 perihelion (at 2.23 AU), C/2020 V2 (ZTF) will be found in Aries during the first half of the month before passing into neighbouring Cetus. From early estimates obtained by northern observers, the comet will probably be in the range of magnitude 10 to 10.5 at the beginning of July, but will brighten slightly as the month progresses as it continues to approach our planet. This decrease in Earthcomet distance is expected to slightly compensate for the comet's increasing distance from the Sun. The second comet of potential interest in July is C/2021 T4 (Lemmon),…

NIGHT LIFE National Science Week is coming up in August, and the federal government has allocated nearly $500,000 in grants to a range of public science outreach activities across the nation… a number of which have an astronomical focus. The National Quantum and Dark Matter Road Trip will be an interactive travelling science and art show, bringing quantum physics, dark matter particle physics and ‘creative expression’ to capital cities, regional and remote areas. Scientists from two ARC Centres of Excellence will visit community hubs in regional Queensland and Victoria, and run public events in other states’ capital cities. Indigenous Science Experience @ Redfern, organised by Macquarie University, will showcase the value of traditional and contemporary Indigenous knowledge in science and technology — including astronomy — and the relevance of science…

THERE WAS A PROBLEM… a big one. At 68 I retired from a busy private practice in psychology. I enjoyed my work, and it was with mixed emotions that after more than 34 years I decided to leave to focus on other interests. In April 2018 my 80th birthday rolled around. That landmark event prompted my wife and me to begin serious discussions about where we wanted to live in our final years. We decided the best path for us was to move into a retirement village near our home. And the problem? I'd been using our backyard for imaging with my new 28cm (11-inch) Celestron EdgeHD scope. Moving to the village presented me with the serious issue of where to use my telescope. The staff made it clear there…