Indholdsfortegnelse for June/July 2018 i Australian Sky & Telescope

NASA OFFICIALS HAVE announced that the launch of the James Webb Space Telescope will be delayed until approximately May 2020, slipping more than a year from its previous goal between March and June 2019. To date, the agency has spent $7.3 billion on Webb’s development. If the mission’s development costs go over the $8 billion maximum that Congress set in 2011, Congress will need to reauthorise the project. An independent review will nail down the changes in cost and schedule, and NASA will report its assessment to Congress in late June. This 2017 image shows all five tennis-court-size, membranous layers of Webb’s sunshield, displayed in Northrop Grumman’s clean room in Redondo Beach, California. These will have to fold into the Ariane 5 rocket fairing. The pieces of Webb are all…

In July 1994, Comet Shoemaker-Levy 9 spectacularly riddled Jupiter with immense chunks of its erstwhile self — a never-before-seen pummeling that grabbed the attention of astronomers and the public worldwide. By that time, most scientists had bought into the notion, first advanced in 1980, that an impact from another huge space object had wiped out the dinosaurs 65 million years ago. But the 1994 comet crash was a stark reminder that massive collisions still happen in our Solar System today. After first asking NASA to assess the threat, in 1996 Congress tasked the space agency with finding, within a decade, 90% of the estimated 1,000 near-Earth asteroids at least 1 kilometre in diameter. NEAs are those asteroids with a perihelion of less than 1.3 astronomical units… that is, an orbit…

We’ve been to asteroids before. Several of them, in fact — flybys, orbital rendezvous . . . we’ve even touched down on two asteroids and brought back samples from one of them. But this winter, two robotic emissaries will usher in a new era of exploration when it comes to these small Solar System bodies. That’s because these spacecraft, the Japanese space agency’s Hayabusa 2 and NASA’s Osiris-REX, will study two dark, primitive, near-Earth asteroids unlike any we’ve explored before. Many of the asteroids we’ve examined close up have been of just one type — the so-called S-type asteroids (S stands for silicaceous). These dominate the inner asteroid belt and may be the source of the most common stony meteorites we have in our museum collections, known as ordinary chondrites.…

These images captured during the planet’s 2012 apparition show many of Mars’ dark albedo markings. The planet rotates every 24 hours, 38 minutes. Since that’s very similar to Earth’s rotation, we view nearly the same hemisphere from night to night. If you observe Mars at 11 p.m. from the same place night after night, the planet will appear to rotate in retrograde (backward) over a period of about six weeks. If you see Syrtis Major front and centre at 11 p.m. the first night, you will see it in that same spot about six weeks later. To see a different side of the planet, you need to observe Mars at a different time of night or from a different longitude. South is up.…

Maria are the most conspicuous large features on the Moon. They have smooth surfaces, dark hues and a general paucity of superposed impact craters. Most maria lavas erupted between about 3.8 and 2.5 billion years ago, lying within large impact basins whose rims are best seen at the curved Apennine and Altai mountain ranges. The ages of formation of the basins themselves are poorly known, but all are from earlier than about 3.8 billion years ago. The interval between basin excavation and the last lava flows in them is as much as 1.5 billion years. During that time, numerous impact craters must have formed on the basin floors and on the various individual flows of lavas that accumulated to form the maria we see today. Craters on top of the…

The arrival of NASA’s Dawn spacecraft at Vesta revealed intensive scarring on the asteroid’s surface. Vesta’s not-quite-spheroid shape is the result of a massive impact event about 1 billion years ago. The collision produced an approximately 500-km-wide crater, now named Rheasilvia, at Vesta’s south pole. About 1% of Vesta’s volume was displaced, with ejecta deposited in a 100-km ring around the impact basin and 2 million cubic kilometres of material sent into space. About 5% of all meteorites we find on Earth come from the Rheasilvian impact. The mineralogy of Howardite-Eucrite-Diogenite (HED) meteorites, which resemble terrestrial igneous rocks, places them in this group. HED meteorites were first connected with Vesta in the 1970s, when scientists noted that their infrared and visible spectra were similar to the asteroid’s. The image above…

As a child on car trips with my family, I often heard my parents ask this question about car colours: Is that blue or green? While driving my parents to a restaurant nearly 40 years later, from the back seat came the same question, “Is that blue or green?” I turned to my wife and said, “I can’t believe they’re still doing that.” Today I engage in discussions about colour as it relates to stars, galaxies and nebulae instead of cars. Several years ago, I shared an image of the open cluster M67 on an online imaging forum. A more experienced astrophotographer commented that the stars in the photo were too yellow, as open clusters usually have younger bluish stars. As the discussion continued, another imager, Wolfgang Renz, noted that…

ASTRONOMERS HAVE LONG thought you couldn’t have galaxies without dark matter, just as you can’t have a cup of coffee without the cup. But the fluffy galaxy NGC 1052-DF2 contradicts this picture. Combining ground- and space-based observations, Pieter van Dokkum (Yale University) and colleagues have found that this diffuse galaxy has 400 times less dark matter compared to other systems of similar mass. In fact, it might not have any dark matter at all. The peculiar object is part of a group of galaxies 65 million light-years away that’s dominated by the beefy elliptical NGC 1052. Astronomers already knew NGC 1052-DF2 existed, but its appearance in images from the team’s Dragonfly Telephoto Array puzzled the researchers. Follow-up revealed the galaxy is so sparse that it’s see-through. Ten strangely big and…

A $2.5 MILLION instrument developed by CSIRO and a consortium of Australian universities will give the Parkes radio telescope the ability to cover more frequencies as it listens for faint radio waves from space. The new receiver covers the spectrum from 700 MHz to 4 GHz and does the work of several extant receivers, as well as covering extra frequencies. “Stars and galaxies ‘sing’ with different voices, some high, some low,” said CSIRO astronomer Dr George Hobbs said. “Until now we’ve had receivers that heard just one part of the choir at a time. This new one lets us listen to the whole choir at once.” Continuous upgrades have given Parkes 10,000 times more sensitivity that it had when it was commissioned in 1961. And the beauty of the new…

It’s hard to think of a time when the landscape of astronomical research in Australia was changing as rapidly as it is at present. While radio astronomy maintains a steady-as-she-goes approach, with innovative new facilities paving the way for the Square Kilometre Array, the optical community is undergoing epochal transformation — bringing both opportunities and challenges. At the heart of the changes is infrastructure — which, for astronomers, of course, means telescopes and instrumentation. Every ten years, Australian astronomers present to government their aspirations for the future in a Decadal Plan. All recent Plans — including the current one (Australia in the Era of Global Astronomy, 2016-2025) — have highlighted the need for significant amounts of time on optical telescopes in the 8-metre class. And it is no secret that…

Short-period comets originate in the Kuiper Belt out beyond Neptune’s orbit and usually take 200 years or less to orbit the Sun. Long-period comets lie in the Oort Cloud, an extremely distant region hosting billions of comets. A single trip around our star could take a long-period comet 30 million years.…

We’ve waited 15 long years and now it’s time to party. Mars reaches perihelic opposition — an opposition when a planet is at its closest point to the Sun — on July 27. This is the first perihelic opposition of Mars since August 2003, meaning that it’s bigger and bolder in the night sky than it’s been in more than a decade. Are you as eager as I am to roam its deserts and poles with a telescope? Maybe even track a dust storm or catch sight of clouds capping mighty Olympus Mons? Mars, a planet that requires the patience of marble, has a more eccentric orbit than most denizens of our Solar System. At approximately two-year intervals, Earth lines up with Mars at opposition, but a majority of those…

When I was young the title of a science fiction story that I hadn’t even read caught my attention: ‘All the Last Wars at Once’. Now, with Mars closer to us than at any other time in the 32 years between 2003 and 2035, I’d like to share a concentrated account of memorable Mars moments — mostly observational — from my lifetime. Like mine, your sights of mighty Mars this winter will be grounded in whatever past experiences you’ve had with this most fascinating of our Solar System’s planets, the world most like Earth. My earliest Mars. I can’t recall the very first time I knowingly saw Mars, but it was probably before I was 8 years old. Carl Sagan said he was 8 when he stared imploringly at what…

Last year we visited part of Hercules, with some doubles from Lyra thrown in. This time our selection is from southwest Hercules, not as far above the Celestial Equator. First up is the easy, bright Kappa Herculis, a 5th-and 6th-magnitude pair of yellow stars that shows well through 8-cm scopes. An optical pair with no gravitational connection, it’s nevertheless an attractive object, although merely a result of our line of sight. About 3.5 degrees south-southeast from Kappa is STF 2021 (S 2021 on star charts), sometimes labelled 49 Ser. A gravitational binary in a very large orbit, its uncertain orbital period is estimated as 1350 years. With my 14-cm refractor at 80× it was a neat orange and yellowish pair, in a scattering of moderate and faint stars. Using an…

By the time this issue hits the newsstands, the third anniversary of NASA’s New Horizons flyby of Pluto will be upon us. What have we learned about our tiny, distant neighbour in the past 36 months? Before New Horizons, scientists didn’t know much about Pluto’s surface, but data and images sent back by the spacecraft have helped transform Pluto from an astronomical object into a geological world. What appeared as a mottled orb through the eyes of the Hubble Space Telescope has resolved into a dynamic planet with faulted terrains, immense and active surface flows of nitrogen ice, glacially eroded highlands, jumbled mountains of water ice blocks, and possibly even a cryovolcano or two. The jury’s still out as to the source of internal heat driving Pluto’s geological activity, but…

This month we’ll witness a partial solar eclipse and a total lunar eclipse, although how much you get to see will depend strongly on where you live or observe from. Only those in or near Perth will see the lunar eclipse in its entirety; everywhere else will see only portions of each eclipse or nothing at all. If you live in Tasmania or the southern coastal regions of Victoria, you’ll get a chance to see the partial solar eclipse on the afternoon of July 13. It will also be visible if you happen to be in Bass Strait or the Southern Ocean, but it won’t be visible anywhere else, nor will it be the best eclipse ever seen even if you are in the right place at the right time.…

115mm Series 6000 ED Triplet APO US price: $1,899 tasco.com.au What We Like Sharp, well-corrected optics Colour-free views Attractive finish What We Don’t Like Visual back locking system can be awkward Focuser backlash THIS IS A GREAT TIME to be in the market for a premium refracting telescope. The price for high-quality refractors has fallen dramatically in recent years, and you can now purchase a 100- to-115-mm extra-low dispersion (ED) apochromatic (APO) telescope that’s almost entirely free of the false colour that plagues achromats for a fraction of the cost commonly seen a decade ago. I’ve had a ball with my own recently purchased apochromat after using almost nothing but Schmidt-Cassegrain telescopes for many years. However, I still consider myself a refractor novice and was eager to see how others…

One of the world’s largest astronomical lenses has been made in New Zealand, destined for the William Herschel Telescope in the Canary Islands. The 1.1-metre-diameter lens is one of six being fabricated for the 6-element prime focus corrector for the telescope’s new WEAVE multi-object survey spectrograph. WEAVE will be used to conduct a large-scale survey over five years of 10 million objects, such as galactic stars and distant extragalactic sources. The lenses are the work of Wellington-based KiwiStar Optics, a unit of Callaghan Innovation, New Zealand’s innovation agency, which specialises in precision astronomical optics. “We bring the glass over from the USA, Japan or Germany and then it is milled into shape using our 5-axis CNC mill. Once in shape the lens goes through a series of shaping and polishing…

“The foundational principle of planetary defense is FIND THEM EARLY,” says Lindley Johnson, NASA’s Planetary Defense Officer. Depending on the scenario and warning time, we have at least three methods we could consider to redirect or destroy a hazardous object heading our way. With significant lead time, we might use a gravity tractor. This is a spacecraft that would use the gravitational force created by its own mass to nudge an object off its Earth-targeting path. This method has not been tested, however, and we would need decades to build, launch and undertake this type of mitigation. A kinetic impactor would smash into the interloper at a high speed, transferring its momentum to the object. Ideally, this would change the object’s velocity, causing its course to deviate enough for it…

There is such a wealth of celestial richness in Scorpius for the binocular user that it’s sometimes hard to know where to begin. The constellation’s star clusters, nebulae (bright and dark) and overall background star-field hold the promise of many hours of enjoyable viewing. One of the standout objects in Scorpius is number 7 on Charles Messier’s famous list of deep sky objects. (It is, in fact, the southernmost object on his list.) Messier 7 is also catalogued as NGC 6475, but its common name is the Ptolemy Cluster, named after the 2nd century CE astronomer Claudius Ptolemy. Every astronomer worth their salt has remarked upon the sparkling gems that make up M7. Ptolemy himself in CE 130 mentioned the “nebula following the sting of Scorpius,” while John Herschel described…

Messier 7 in Scorpius is also known as Ptolemy’s Cluster, named for the 2nd century European astronomer. This cluster is found in a rich field — in addition to the globular cluster NGC 6453 far in the background, there are also a couple of Barnard’s dark nebulae and many double stars. And there are hundreds of variable stars within the 1.3 degree field of M7, although most of them are not suitable for visual observers. But let’s look at three very different long-period variables that most certainly are suitable. BN Sco is a rare example of a Mira-type variable with a double maxima. It is very red, and has a period of 620 days with a magnitude range from 9.8 to less than 14.5. Nearby is SY Sco, a Mira-type…

Atop our grassy hill, green fields turn obsidian as night sweeps her cloak across the world. A telescope is waiting, the stars appear, and I’m where I belong. Winter nights are an ideal time for those of us who feel at home among the stars to lose ourselves in some of the most beautiful wonders of the deep sky. Planetary nebulae are shining baubles on the dome of the sky that come in an amazing wealth of guises. One of the most famous is the Ring Nebula (M57) in Lyra, which Antoine Darquier independently discovered with a small refractor while observing the Comet of 1779. He claimed it resembles a planet that’s fading away. Although Darquier may have been the first to compare this type of nebula to a planet,…

Vesta, the fourth-discovered asteroid, reaches opposition (opposite the Sun in the sky when viewed from Earth) on June 19. Though neither the largest nor the most massive of the main belt asteroids, Vesta is the brightest of them all when it is at opposition. This year it shines in Sagittarius at magnitude 5.3 and will be visible without optical aid under reasonably dark skies. It’ll be a bit dimmer for the rest of June and into July, ranging from magnitude 5.6 to 5.9, but still within reach of the naked eye under good skies. There’s something intrinsically interesting about observing asteroids — they’re giant space rocks, after all — but the success of NASA’s Dawn mission turned Vesta into a particularly compelling target. While the Hubble Space Telescope had resolved…

Saturn arrives at opposition on June 27, very close to the time of full Moon. On the night of June 27–28, the Moon and Saturn will only be about 1° apart. It’s a pleasant scene, but to get the best binocular or telescopic view of the ringed planet, make plans to observe on the nights (weeks!) before and after opposition. Last quarter Moon falls on June 7 (and again on July 6), when Saturn rises at 6:30pm, about 1¼ hours after the Sun sets. Saturn’s –22° declination means it is very well placed for observers at southerly latitudes. This present declination is about ½° farther south than it was when the planet was at opposition last year. This southerly crawl will continue until 2021, so we have plenty of good…

IN MARCH I ATTENDED a SETI Institute workshop, where a multidisciplinary group of astronomers, neuroscientists, anthropologists, philosophers and historians pondered new approaches to expanding the search for extraterrestrial intelligence. Discussions ranged from the physics of planet formation, through the origin and evolution of life and the prospects for complex life and intelligence, to forthcoming hunts for both biosignatures and ‘technosignatures’ on exoplanets. To me, the way these topics flowed together at the meeting served as a reminder that the distinction between astrobiology and SETI is completely artificial. It might exist in terms of bureaucracies and funding streams, but intellectually the quest to know how we — and living things in general — fit into the universe is all part of the same nested series of questions. How does matter turn…