Indholdsfortegnelse for July 2019 i Australian Sky & Telescope

FOR THOSE OF US of a certain age, it’s sort of hard to believe that 50 years have passed since Neil Armstrong uttered those famous words: “That’s one small step for [a] man… one giant leap for mankind”. Yet half a century has indeed come and gone. And crewed spaceflight beyond Earth orbit seems to have come and gone too. No-one has travelled further than 620 kilometres from Earth’s surface since 1997, when the space shuttle Discovery boosted the Hubble Space Telescope to a higher orbit. Why haven’t we been back to the Moon? Politics and money, essentially. The ‘space race’ is long gone, and there is little political will for expensive Moon ventures. That said, there has been something of a resurgence in lunar exploration in recent years, with…

2020 NASA budget boosts exploration, not science The US president’s FY2020 budget request puts US$21.019 billion toward NASA — a drop of a half billion dollars from the just-approved 2019 budget. The proposal doubles funding for NASA’s return to the Moon via the Lunar Gateway, which aims to put a crewed outpost in lunar orbit. The budget request also initiates a Mars sample-return mission. At the same time, the proposal decreases funding for astrophysics (-20%), planetary science (-5%) and Earth science (-8%). And while the James Webb Space Telescope gains $46.6 million in funding, the Wide-Field Infrared Space Telescope (WFIRST) is cancelled. The request also zeroes out funding for NASA’s Office of STEM Engagement. However, the FY2019 budget request likewise cancelled WFIRST, STEM outreach and several Earth science missions, but…

The expansion of the universe cannot be expressed as a simple velocity. Galaxies are not receding from each other through some imaginary static space. Instead, space itself is expanding, thereby pushing the galaxies away from one another. As a result, the distance between two galaxies increases over time. The more space there is between the two galaxies, the faster their mutual distance is growing, in kilometres per second. In other words, there’s no single ‘velocity value’ for the expansion of the whole universe – it all depends on the scale you consider. It’s like monetary inflation: The inflation rate for 2018 cannot be expressed in dollars (that would only work for a particular sum of money), but must always be given as a percentage, or a proportionality constant. Not that…

There are various ways to determine the distance to another galaxy: VARIABLE STARS The pulsation period of Cepheids – a particular and easy-to-recognise type of variable star – is related to their peak luminosity. Measuring a Cepheid’s period reveals its luminosity; comparing that to its apparent brightness reveals its distance. Similar period-luminosity relationships hold for other types of variable stars, most notably RR Lyrae stars. The relationships need to be calibrated by measuring distances to Milky Way variables by means of the parallax method. ECLIPSING BINARIES By spectroscopically measuring the orbital speeds of the two components of an eclipsing binary star (a close binary in which the stars mutually eclipse each other), and combining this information with the observed light curve, it is possible to geometrically calculate the physical dimensions…

SEPTEMBER 17, 1969, found me in one of many white buildings on the campus of NASA’s Manned Spacecraft Center in Houston, Texas. I had been summoned there by a telegram. It had been nearly two months since astronauts first stepped onto the lunar surface, and while the world was still enchanted, NASA had called scientists to get to work on an often-underappreciated aspect of the Apollo missions: the rock and dust samples. In response to President Kennedy’s 1961 challenge to the USA to land a man on the Moon and return him safely to Earth by the end of the decade, NASA had designed and implemented an audacious and dangerous space program. The pinnacle of this program was the Apollo 11 mission, which on July 20th (the 21st in Australia)…

PETER NUGENT KNEW HE HAD TO ACT FAST. It was a little past noon on August 24, 2011, and he was sifting through images of the previous night’s sky when he discovered a new point of light: a young supernova explosion. While the explosion was only 12½ hours old, it was already so bright that it outshone the nearby stars in its galaxy and so large that its ballooning debris cloud would easily fill a volume equal to the orbit of Saturn. Nugent checked the time of the image and saw that another 16 hours had already passed. He dashed to the phone. Some 20 minutes later, a colleague swung a telescope in the Canary Islands toward the blast and shot a spectrum. The speedy observations told Nugent (University of…

WHEN Early June 10 p.m. Late June 9 p.m. Early July 8 p.m. Late July 7 p.m. These are standard times. HOW Go outside within an hour or so of a time listed above. Hold the map out in front of you and turn it around so the label for the direction you’re facing (such as west or northeast) is right-side up. The curved edge represents the horizon, and the stars above it on the map now match the stars in front of you in the sky. The centre of the map is the zenith, the point in the sky directly overhead. FOR EXAMPLE: Turn the map so the label ‘Facing North’ is right-side up. About halfway from there to the map’s centre is the bright star Arcturus. Go out…

Meteor activity in the Southern Hemisphere is generally at its best during the winter months, with the Southern Delta Aquariids being the pick of the bunch of meteor showers from a numbers point of view. This shower is active from July to August, peaking on the morning of July 30 when you can expect to see from 5 to 8 meteors per hour from a dark sky. They are usually faint and swift. Another shower, the Alpha Capricornids, also is active from July to August, peaking on the morning of July 29. This shower is rich in bright meteors and fireball activity, but low in numbers. The meteors are usually yellow in colour, and many leave trains that last for minutes. For both of these showers it’s best to start…

Asteroid Day June 30 A global day of education to help protect Earth from asteroids. asteroidday.org Queensland Astrofest July 26–August 4 Observing under dark Queensland skies. Held every year since 1993. qldastrofest.org.au National Science Week August 10–18 Includes lots of astro events. Keep visiting the website for the latest info. scienceweek.net.au Astro Rocks Fest September 20–22 Family weekend of both astro and geo fun at Mt Magnet, WA. mtmagnet-astrorocks.com International Observe the Moon Night October 5 Annual event to encourage observation and understanding of our Moon. facebook.com/observethemoon/ NZ Starlight Conference October 20–23 A theme is ‘Towards a Dark Sky Nation’. starlightconference.org NZ Starlight Festival October 24–25 Held at the Aoraki Mackenzie International Dark Sky Reserve. starlightconference.org NACAA XXIX April 10–13, 2020 Biennial amateur astronomy convention. nacaa.org.au…

Rethinking red light The conventional wisdom of using red light at night needs to be revisited, according to tests of a number of colours. The nebulae of Ophiuchus Snare a collection of dark and bright nebulae with just a few sweeps of your scope through the Serpent Holder. Shoot the Moon Getting started in lunar photography can be a simple as grabbing your smartphone and having a go. We show you how. Test Report: Lumicon’s OIII filter Every serious deep sky observer needs an oxygen III filter. We put Lumicon’s latest model to the test. FIND US ON FACEBOOK…

DISTANCE: Astronomers spot a ‘standard candle’ star or supernova in a distant galaxy. They calculate how far away the galaxy has to be in order for the star to look as faint as it does. VELOCITY: The expansion of the universe shifts the standard candle’s light to longer, redder wavelengths. The amount of redshift tells astronomers the galaxy’s apparent recession velocity. RATE: A plot of the galaxies’ distances versus redshifts shows that farther galaxies recede faster. (Simulated data shown.) The slope of the line is the universe’s expansion rate.…

Investigators’ tests indicated that basaltic rocks collected by Apollo 11 astronauts had an age of more than 3½ billion years; the crust was about a billion years older. Samples brought back in November 1969 by the Apollo 12 team, on the other hand, were about 500 million years younger. These rocks all formed at extremely high temperatures. The findings suggested that, in the words of a New York Times report from the conference, “the moon had a history of fiery, cataclysmic upheavals.” WEBLINK: Listen to the Apollo 11 mission recordings at https://archive.org/details/Apollo11Audio.…

Astronomers often speak of Type Ia supernovae as the explosions of white dwarfs that hit a specific mass limit of 1.4 Suns, called the Chandrasekhar mass. But in fact the dwarf never reaches that limit: If it did, gravity would force it to collapse, not explode. Instead, as the dwarf approaches the Chandrasekhar mass, it contracts, causing the internal temperature and density to spike. At a certain point — which is incredibly close to the Chandrasekhar mass — carbon fusion ignites and blows the white dwarf apart.…

“Everything that lives strives for color.” — Johann Wolfgang von Goethe, as translated in the Dover Publications edition of Minnaert’s The Nature of Light and Colour in the Open Air Winter is always just a few kilometres from us. By that I mean a few kilometres upward, in the cirrus clouds where ice crystals can project the circles, arcs, pillars and patches of often vividly and variedly coloured halo phenomena. Winter is also the season for rain. But sometimes that rain is mixed with sunlight to give us the multi-hued pleasure of the rainbow. At night, however, beginning amateur astronomers soon learn that the colours seen in visual astronomy are far less intense than those that appear in the images of astrophotography. Even so, there’s great beauty in the subtle tints…

Throughout its life, a star keeps an extraordinary balance between energy pushing out from its core and gravity pulling in. As long as the star burns elements lighter than iron at its centre, this hydrostatic equilibrium will hold steady. But once only iron remains in the core, its demise is imminent. Until this moment, the star could generate the energy needed to hold gravity at bay by fusing elements lighter than iron. Energy can also be produced by fissioning, or splitting, elements heavier than iron. But to transform iron into something else, you need an input of energy. Without that, a star that has wound up with an iron heart keeps it together for only a fraction of a second. Suddenly, the long-restrained gravity becomes unleashed and the star implodes,…

WHEN ROBERT ASUMENDI looked through a binocular telescope, he realised several things at once: • Binocular vision is vastly more comfortable and pleasurable than monovision. (So much so that Hans Lippershey had to build a binocular before the patent office would even consider his patent application for the telescope in 1608.) • Binocular vision helps to compensate for Robert’s severe astigmatism. • Despite wanting a binocular scope, he also wanted grab-and-go portability, wide fields and enough aperture to provide satisfying views of deep sky objects. Robert searched for a scope that would satisfy all his requirements but came up empty. “There’s no commercial scope that delivers all those things,” he reports. “So I made it.” Robert faced two simple challenges: He had never built a telescope before, and he didn’t…

A stalwart of the amateur astronomy scene in Australia for many decades, Col Bembrick was the 2004 recipient of the prestigious Berenice Page Medal awarded by the Astronomical Society of Australia. What got you into astronomy? A small paperback book by Patrick Moore, probably a Christmas present, on how to observe the Moon. This was closely followed by the excitement and publicity of the Sputnik I era (yes, that was back in 1957) when I was in high school. Following the coverage in the newspapers, neighbours rushed out into their backyards to witness the passage of the satellite overhead. Many chatted over the back fence to people they had never spoken to before — this was ‘social media’ before the term was invented. At this time I was learning my…

TWO STUDIES ARE FINDING conflicting results about whether methane exists on Mars. Its presence would point to certain geochemical processes or, less likely, biological activity. Researchers using the Planetary Fourier Spectrometer (PFS) aboard Europe’s Mars Express orbiter spotted 15.5 parts per billion by volume (ppbv) of methane in 2013, a day after NASA’s Curiosity rover measured a spike of 5.78 ppbv. Atmospheric simulations and geological analysis helped track the emission’s origin to a fault area southeast of Gale Crater, Marco Giuranna (National Institute of Astrophysics, Italy) and colleagues report April 1 in Nature Geoscience. However, the European-Russian ExoMars Trace Gas Orbiter (TGO), a spacecraft designed to measure vanishingly small amounts of gases in the carbon dioxide–based atmosphere, has failed to find any methane during the first months of its science…

ASTRONOMERS HAVE DISCOVERED a second galaxy without dark matter. This ultra-diffuse galaxy is one of thousands of large, star-poor objects discovered in recent years. Most of these galaxies have more than the usual amount of dark matter — it’s all that keeps their sparse stars from disbanding. But last year, Pieter van Dokkum (Yale) and colleagues discovered one without much dark matter at all, dubbed NGC 1052-DF2. Now the team has discovered a second one in the same region, suggesting more might be present. Van Dokkum and colleagues found NGC 1052-DF4 in images taken with the lenses of the Dragonfly Telephoto Array. They followed up with Hubble Space Telescope imaging and spectroscopy through the Keck I telescope on Mauna Kea, Hawai‘i. The observations appear in the March 20 issue of…

IN THE 1980S, when people in East and West Berlin still lived in two very different universes, politically speaking, Checkpoint Charlie was an intimidating and heavily guarded crossing point between communist oppression and liberal democracy. Today, it is one of the most popular tourist attractions in the capital of united Germany. But 29 years after the Berlin Wall opened in 1989, another insuperable barrier, this time scientific in nature, manifested itself just 600 metres eastward of Checkpoint Charlie, in the Auditorium Friedrichstrasse. On a drizzly Saturday in November 2018, this unadorned Soviet-style building served as the intellectual battleground for a cosmological Cold War. Some 130 scientists flocked to a one-day symposium here to discuss an unnerving crisis in our understanding of the universe. It was a diverse bunch from all…

TELRAD ANTI-DEW HEATER Apache-Sitgreaves Research Center now offers an integrated Telrad Dew Heater (US$30). The device fits snugly at the base of your Telrad unit-finder’s optical window and is powered with any standard dew controller on the market today that connects using an RCA-style plug. Each purchase includes a cable clip that attaches to one screw on your Telrad. A 1.8-metre RCA extension cable is also available for an additional US$10. apache-sitgreaves.org PORTABLE PRECISION iOptron introduces the latest addition to its series of portable, center-balanced, equatorial Go To mounts, the CEM40 (US$1,998). The mount head weighs just 7.2 kg yet can support loads of up to 18 kg. It features precision stepper motors and 216-tooth aluminium in both axes. The CEM40 advertises permanent periodic error correction (PPEC) to produce smooth…

July 2019 is a special month for space enthusiasts as we celebrate the 50th anniversary of the Apollo 11 mission and the first crewed landing on the Moon. There will be plenty of celebratory activities going on around the country. In Brisbane there is the fabulous NASA – A Human Adventure exhibition, which features real and replica spaceflight items. Check it out at qm.qld.gov.au/space. In the nation’s capital, the Australian National University will have a four-day Moon Festival with lots of public events and tours. Questacon and the National Museum of Australia have lunar exhibits, while a 45-minute drive outside of Canberra will bring you to the amazing Canberra Deep Space Communication Complex (cdscc.nasa. gov) at Tidbinbilla — one of NASA’s three worldwide tracking stations — with its huge 70-metre…

HOW TO SUBMIT YOUR IMAGES Images should be sent electronically and in high-resolution (up to 10MB per email) to contributions@ skyandtelescope.com.au. Please provide full details for each image, eg. date and time taken; telescope and/or lens; mount; imaging equipment type and model; filter (if used); exposure or integration time; and any software processing employed. If your image is published in this Gallery, you'll receive a 3-issue subscription or renewal to the magazine.…