Indholdsfortegnelse for September 2019 i BBC Sky at Night

CHANDRA X-RAY OBSERVATORY, MEERKAT TELESCOPE, 23 JULY 2019 A beautiful composite image of X-ray (shown in green) and radio data (shown in red) exposes the very heart of the Milky Way. The brightest part on the far right of the image is a supermassive black hole – Sagittarius A* – four million times the mass of the Sun. The turmoil of the cosmos is evident in this scene. Clouds of gas billow over neutron stars; white dwarf stars strip material away from companion stars and tendrils of radio emissions lash out and coil around the galactic heart. Despite the apparent chaos at the centre of our galaxy, Sagittarius A* is considered to be a relatively ‘quiet’ resident, compared to the black holes in other galaxies. The strong magnetic fields surrounding…

The Indian Space Research Organisation (ISRO) successfully launched its second mission to the Moon, Chandrayaan-2, on 22 July. The spacecraft is due to enter lunar orbit by mid-August. Once there, it will put down a lander, named Vikram, near the Moon’s South Pole on 7 September 2019. A rover, Pragyan, will then explore the terrain up to 500m away from the lander, searching for water and minerals which may be useful to future space missions. The mission cost just £116m, continuing India’s legacy of providing ambitious space missions on a modest budget. It’s also India’s first space mission to be spearheaded by two women. “Today is the beginning of the historical journey of India towards the Moon and to land at a place near the South Pole to carry out…

Huge amounts of ‘missing’ iron, which astronomers have been looking for for decades, could be hiding in plain sight in the space between stars, according to a new study. Iron is one of the most abundant heavy elements in the Universe and is commonly found around stars. However, when astronomers pull back to look at interstellar space, there seems to be hardly any. This doesn’t necessarily mean that there is no iron in interstellar space, only that it’s in a form we can’t detect. The identity of this exotic form of iron has evaded astronomers for decades. Now, a team from Arizona State University (ASU) might have found the culprit – clumps of iron atoms bonded onto chains of carbon atoms known as iron pseudocarbynes. “We are proposing a new…

A disc of debris has been found around an infant exoplanet for the first time. “Planets form from discs of gas and dust around newly forming stars, and if a planet is large enough, it can form its own disc as it gathers material in its orbit around the star,” says Andrea Isella from Rice University, who led the study. The discovery could help give insight into how moons grow around planets like Jupiter. However, these discs only last around 10 million years, so they are only found around young planets. Isella’s team observed the infant gas giant PDS70b with the Atacama Large Millimeter/submillimeter Array (ALMA), and discovered that it was surrounded by dust ring. “There’s much that we don’t understand about how planets form, and we now finally have…

Early in the Solar System’s history, the disc of gas and dust surrounding the young Sun had coalesced into countless bodies of different shapes and sizes. Those objects created far from the Sun contained numerous ices, such as water and carbon dioxide, mixed with grains of more stable material. Many of these icy rubble piles came together to form the planets, but others were scattered outwards, up to halfway to the nearest star. When these ancient objects return to the Sun’s vicinity, we can see them, as comets. All previous comet missions have, by necessity, been to periodic comets whose orbits were already well-known prior to launch. Data from these missions has been scientifically invaluable. However, during each passage past the Sun, nucleus ices are altered, the terrain modified, and…

For the past month Jupiter has been hard to miss in the night sky. Shining brightly, the gas giant has been one of the first objects to appear to the naked eye as darkness falls, and it will continue to be visible throughout September, low in the southwest in the early evening. Our best view of the planet right now, however, comes not from Earth, but from the spacecraft Juno. Since 5 July 2016, the NASA probe has been orbiting Jupiter, swooping past the planet once every 53 days. The spacecraft is two thirds of the way through its primary mission and, at the time of writing, has completed 21 close passes (or ‘perijoves’), with the next one due on 12 September. By combining the data collected on these passes,…

Lunar clair obscur (optical) effects are tricks of the light which are seen when observing the Moon. They take many forms, the best known being the lunar X and lunar V visible around the time of the first-quarter Moon. Portions of the rims of craters La Caille (68km), Blanchinus (68km) and Purbach (118km) catch the early lunar dawn to form a giant letter X floating in a sea of dark shadow. Similarly, features near the 23km lunar crater Ukert appear to produce the letter V. Some effects last for ages while others are time critical. Phase is not a precise enough measure to predict visibility and instead, a value known as co-longitude is used. This marks the position of the morning terminator measured in degrees west from the Moon’s prime…

Lacus Felicitatis Type: Lunar lake Size: L-shaped, each leg approximately 90km long Longitude/latitude: 5.4º E, 18.5º N Age: Between 3.2–3.9 billion years Best time to see: First quarter (7–9 August) and six days after full Moon (20–22 August) Minimum equipment: 50mm refractor Images show the hills to look like drops of dark liquid poured onto the brighter surface below For a barren dry world, it’s interesting just how many water terms are used to describe features on the Moon. There are the giant lava filled seas of course, visible as dark patches even with the naked eye. Then there are bays such as Sinus Iridum and Sinus Medii. Smaller water-related features include marshes and lakes. This month’s Moonwatch feature is a lunar lake named Lacus Felicitatis, the Lake of Happiness.…

1. Kemble's Cascade 10 x 50 Late summer evenings are among the best times to see Kemble’s Cascade: it is approximately vertical in the sky so you get the full effect of a ribbon waterfall falling into a splash-pool, the open cluster NGC 1502. To find it, extend a line from Caph (Beta (b) Cassiopeiae) to Segin (Epsilon (e) Cassiopeiae the same distance to the 5th magnitude star in the middle of a line of 8th magnitude stars. □ SEEN IT 2. Kemble's Kite 10 x 50 Another asterism brought to light by Lucian Kemble is his eponymous Kite. Take a line from Segin through Iota (i) Cassiopeiae and extend it another 7 ˚ to V805 Cassiopeiae, which looks deep yellow in binoculars. It is the brightest of a 1.5…

Around 21,000 years ago, the star-filled patch of sky we call the constellation Cygnus changed forever. Amid the band of the Milky Way, a brilliant point of light appeared as the first photons of a colossal explosion began to rain onto Earth. They had arrived from the cataclysmic death throes of a massive star: a supernova explosion so violent and so energetic that even now the shock wave from the blast is still expanding at breakneck pace. If you have a large enough telescope you can see its effect today: astronomers call it the Veil Nebula or, sometimes, the Cygnus Loop. For stargazers the Veil Nebula offers a beguiling, window into the process of stellar death. But though it has been studied for decades, there is still a stack of…

Follow the stars Because it’s relatively faint, you’ll need to mount any camera and optics you use to image the Veil Nebula Complex on a tracking platform that enables long-exposure imaging. How good a mount you’ll need will depend on the focal length of the optics you’re using, but a basic motorised equatorial model that’s been properly polar-aligned should be fine for capturing several-minute exposures using a short focal-length refractor or telephoto camera lens. Gather stacks of data The key to acquiring high-quality deep-sky images – especially of faint, nebulous targets like those in the Veil Complex – is to capture many individual sub-exposures and then calibrate and stack them. This will create a final image that has a better signal-to-noise ratio with a ‘smoother’ (less noisy) background. And it’ll…

Getting ready for the new astronomy season is a two-part process, as you must prepare both your equipment and yourself for the adventure ahead. Good observations start with a solid foundation, so begin by spanner checking all the hinges on your tripod, tightening up where necessary and lubricating metal and plastic joints with silicone lubricant. Carefully check your mount to ensure both axes move smoothly with the clutches disengaged and, if the mount is powered, carry out a dummy run to make sure there are no unusual noises emanating from the motor drive. Check that the dovetail clamp bolts move smoothly and lubricate if necessary. If your mount is a Go-To, visit the manufacturer’s website and update the software if needed. Carefully examine your telescope’s optical surfaces and use a…

Step 1 Print out the downloadable plans and use them to carefully mark out and cut the wooden strips, then sand the ends and surfaces smooth. Mark the positions of the holes with a sharp pencil. A sawing board or block can help keep the ends square. Step 2 Use a 6mm bit to drill the dowel holes. It’s a good idea to tape pairs of strips together, so the holes align. Some pieces require you to file or sand the ends to round them off. A pillar drill helps keep the holes vertical. Step 3 Some of the strips are glued together. We used temporary dowels to keep holes aligned and small clamps to apply some light pressure. We used a plane to form a dovetail from an offcut…

More ONLINE A gallery containing these and more of your images The Pleiades Kees Scherer, Castelo Novo, Tomar, Portugal, 5–10 October 2018 Kees says: “I wanted to bring out the detail in the blue, cirrus-like reflection nebulae and cover the dynamic range needed for this target with one exposure time. The QHY16200 CCD camera that I used has a much higher dynamic range than the DSLR camera I’ve used before and a set of test exposures showed that 300 seconds was a perfect match for my red, green and blue filters. The total of 221 sub-exposures helped to make the image cleaner, but I needed six clear nights to acquire the data. I only shoot in the sky’s eastern part due to light pollution in the west and only when…

The wish-list for astrophotographers who want to capture large objects, or areas of the sky with multiple targets, always includes large format cameras. Moravian Instruments has introduced its G4-16000 MK II full-frame camera that houses the KAF 16803 CCD mono sensor and, looking at the specs, it should tick quite a few boxes on anyone’s list. The G4-16000 camera model we tested in this review was the EC (enhanced cooling) version. It came with the Moravian 7 position filter wheel pre-loaded with Baader 50x50mm LRGB and narrowband filters that are all optional extras, but necessary to make the most of the camera. The G4 16000 is supplied in an aluminium carry case and includes a power supply, USB 2 cable, printed instruction booklets and software and drivers on a USB…

Scientists have spent decades pondering one of the biggest mysteries of modern astronomy: how fast is the Universe expanding? Now a novel set of measurements, meant to clear up the issue, has instead confused matters further. The conundrum stems from the fact that two different methods to calculate the Hubble Constant – the number astronomers use to measure the expansion – give two answers. Looking at Cepheid variable stars in the local Universe, astronomers get a value of 74.0km/s/Mpc (megaparsec) for the Hubble Constant. But observations of the cosmic microwave background (CMB) give a conflicting 67.4km/s/Mpc. “Questions arise as to whether the discrepancy is coming from some aspect that astronomers don’t yet understand about the stars we’re measuring, or whether our cosmological model of the Universe is still incomplete,” says…

Building work on the Thirty-Metre Telescope (TMT) in Hawaii has been held up by activists. The telescope was due to begin construction on 15 July 2019, but protesters created a roadblock preventing construction vehicles from accessing the mountain. As of writing, an estimated 2,000 people have taken part, with additional protests across the state and continental US. The $1.4 billion observatory will be one of the largest mirrored telescopes in the world and is due to be built on the summit of Hawaii’s Mauna Kea. The site is sacred to the native Hawaiian people and opponents fear the project will damage and desecrate the mountain. However, there are many who support the telescope's construction. “[Supporters] say things like TMT is important to education, to high quality jobs and to inspire…

Many of the ocean worlds in habitable orbits throughout the Galaxy could in fact be snowball worlds Earth has kept a remarkable stable climate over its four-billion-year history, despite the fact that the Sun has been getting steadily brighter over time. This is because of a naturally operating thermostat, called the carbonate-silicate cycle, which acts to regulate the amount of carbon dioxide in our atmosphere and therefore the amount of insulation from the greenhouse effect. Silicate rocks on the land get weathered, soaking up the carbon dioxide from the atmosphere and becoming carbonate rocks in the process. Over time, plate tectonics drag these back into the mantel. Eventually the carbon dioxide gets rereleased into the atmosphere through volcanoes. Crucially, the rate of erosion on land is dependent on the temperature,…

The Great Red Spot has been a familiar fixture on Jupiter for centuries. The swirling maelstrom is caught between the South Equatorial Belt to its north, and a white zone to its south, and spans a distance 1.3 times Earth’s diameter. Juno has spent several of its passes looking at the Spot. The team hopes its gravitational maps will eventually reveal how far down the storm extends, giving an insight into how the storm has been raging for so long. But could the storm be about to blow itself out? The Spot has been getting smaller for many years, but this shrinking sped up dramatically in May 2019. By mid-June, analysis of amateur images showed the Spot’s size had reduced by 3,000km – around 20 per cent of its overall…

Neptune Best time to see: 10 September, 01:00 BST (00:00 UT) Altitude: 31° Location: Aquarius Direction: South Features: Small disc, colour, Triton Recommended equipment: Binoculars, 75mm telescope and larger Neptune, the eighth and farthest planet from the Sun in our Solar System, is at opposition on 10 September and will be visible for the entire night. The mag. +7.8 planet requires at least binoculars to see, as there is not the faintest chance of seeing it without. Currently, the blue ice giant is in the constellation of Aquarius located in close proximity to the star Phi (φ) Aquarii. As darkness falls on the evening of 5 September, Neptune is just over 1 arcminute from mag. +4.2 Phi Aquarii, on the eastern side of the star. On 6 September, Neptune swaps…

Asteroid 21 Lutetia is an irregularly shaped asteroid with dimensions of 121x101x75km. It’s one of a small number of asteroids that has had its surface imaged in close-up. This took place on 10 July 2010 when the comet probe Rosetta did a flyby of Lutetia, passing the object at a distance of 3,170km at a relative speed of 15km/s. For us on the ground the view isn’t quite as spectacular. Lutetia typically appears no different to a tenth magnitude star, save for the fact that it appears to move against its starry background. It’s a main belt asteroid discovered in 1852 by Hermann Goldschmidt, a German-French astronomer who is immortalised by a 120km crater on the Moon named after him. Lutetia is the Latin name for Paris. This month Lutetia…

The Veil Nebula Complex is a large supernova remnant located under the eastern wing of Cygnus the Swan. It occupies a significant portion of the triangular area defined by Gienah (Epsilon ( e )), Zeta ( z ) and 52 Cygni. The overall shape of the Veil is circular, with most of the light being found in a broken 2.5˚ diameter ring which defines the outer- edge of the circle. Actually, the ring is so broken that the brightest portions look more like two ghostly brackets. Inside the brackets is further nebulosity but it is here that the challenge ramps up, as this region has a very low surface brightness. The two ‘brackets’ are arranged east and west of the Veil’s centre. The brightest and easiest to see component is…

The Veil Nebula Complex lies in the constellation of Cygnus, which you’ll find sitting high in the south at around 10pm (BST) this month. The brighter nebulae comprising the supernova remnant fill an area around 3° across on the sky, with the Eastern Veil lying roughly 3° to the southeast of the 2nd-magnitude star Epsilon Cygni and the Witch’s Broom Nebula a similar distance due south. Even the brighter Eastern Veil and Witch’s Broom will require a large-aperture scope under dark skies to see clearly, while the use of either a UHC or OIII visual filter can sometimes help improve the view at the eyepiece.…

Have you often wished that you could spot a nebula or star cluster but didn’t know where to start? It may come as a surprise to some beginners, but observing these faint deep-sky objects is not as tricky as you may think. You can view them from the comfort of your garden or local dark-sky site and you needn’t spend a fortune on the latest equipment. A deep-sky object is an astronomical object which is outside our Solar System and includes galaxies, nebulae and clusters. Understanding the classification and naming of objects can be daunting, let alone locating and observing them, but once you know Orion from Andromeda you will find that deep-sky targets are not as elusive as you first thought. For starters, it’s worth buying a good observing…

This month’s project is a mount to enable your smartphone to be used as a ‘finderscope’. There are several planetarium apps that display a detailed view of the sky relative to the direction in which you point your phone. By mounting the phone and aligning it to your scope you can slew around while also displaying information about the objects you can expect to see. We found it enjoyable to move the scope until an object of interest appeared on the screen, a planet for example. You can zoom in on screen and move the scope to centre the target. A traditional finderscope can be used to refine the pointing but when using a wide-angled eyepiece at low magnifications, we found the object was often within the field of view…

Although it’s annoying when you’re observing deep-sky objects, the sight of a big, bright, almost-full Moon is still pretty impressive. When it’s low in the sky, the ’Moon Illusion’ makes our nearest neighbour look much larger than normal and this is where nature plays a cruel trick on photographers. With the full Moon having just risen and looking enormous, an average camera shot of it will show that it’s actually pretty tiny. To see any detail on it, you’ll need at least a 200mm or longer focal length lens or telescope. This month’s Harvest Moon presents the perfect opportunity to catch that detail. The easiest way to do this is to use a long focal length lens or telescope with a DSLR fitted. Alternatively, if you have a steady hand,…

Whether you’re a seasoned astrophotographer or a beginner, we’d love to see your images. Email them to contactus@skyatnightmagazine. com. Ts&Cs: www.immediate.co.uk/ terms-and-conditions We’ve teamed up with Altair Astro UK to offer the winner of next month’s Gallery an Altair Astro Planet-Killer 685nm Premium IR Pass Filter with AR coating, designed to deliver sharper lunar and planetary images with mono CCD or CMOS cameras. For more info visit: www.altairastro.com • 01263 731505…

NASA has taken another small step towards the giant leap of returning to the Moon by finishing construction of the Orion capsule that will take part in an uncrewed test flight Artemis 1. Vice President Mike Pence announced the milestone on 20 July as part of the celebrations surrounding the 50th anniversary of Apollo 11. “Similar to the 1960s, we too have an opportunity to take a giant leap forward for all of humanity,” says NASA Administrator Jim Bridenstine. Meanwhile, preparations are already being made for Artemis 2, which aims to repeat the mission in 2023, only this time with a crew on board. The heat shield which will protect the crew during re-entry was delivered to the Kennedy Space Center on 11 July. This second test will confirm that…

For a number of years I have been physically disabled and I’m no longer able to enjoy my astronomy hobby outside. In the past year I have re-evaluated my observing to take account of my health and have found ways to work around the problems. Most people who can no longer get outside to do their astronomy feel they have only one option – automation, but for many that can be too expensive. However, there is an alternative: by using your existing setup within your home, and with a little thought and modification, it can be fairly easy to achieve. Here are a few pointers to help you. If you use a reflector or Dobsonian the chances are you’re going to need a different scope; it’s just not practical to…

Though Juno is expected to survive beyond the end of its nominal mission in 2021, the spacecraft can’t last forever. Fortunately, the European Space Agency (ESA) is already designing the follow up mission – the Jupiter Icy Moons Explorer (JUICE). As the name suggests, this mission’s priority is to look at Jupiter’s satellites, but it will still examine the gas giant. “They are two very different missions,” says Dr Leigh Fletcher, a member of the Juno team. “But JUICE is designed to be complementary to Juno. JUICE will be looking at the cloud tops and upwards, whereas Juno focuses on the cloud tops downwards.” It does mean that if Juno does make a discovery, there’s already a mission in development that should be able to take over from Juno when…

Return of the EVENING STAR BEST TIME TO SEE: Venus is best at the end of the month, with highlights near Mercury on 13 and 29 September Venus is the brightest planet due to its proximity to the Sun and reflective cloud covered globe. Its orbit is around 70 per cent the size of Earth’s and from our perspective it never strays too far from the Sun in the sky. It takes Venus 224 days to orbit the Sun and its day is –243 Earth days long, minus because it’s retrograde or backwards. From Earth we see Venus pass the Sun twice per orbit; once on the inward part closest to Earth known as inferior conjunction, and once on the distant part known as superior conjunction. On rare occasions inferior…

KEY TO STAR CHARTS When to use this chart 1 September at 01:00 BST 15 September at 00:00 BST 30 September at 23:00 BST On other dates, stars will be in slightly different positions because of Earth’s orbital motion. Stars that cross the sky will set in the west four minutes earlier each night. How to use this chart 1. Hold the chart so the direction you’re facing is at the bottom. 2. The lower half of the chart shows the sky ahead of you. 3. The centre of the chart is the point directly over your head. Sunrise/sunset in September* Moonrise in September* Lunar phases in September More ONLINE Paul and Pete’s Virtual Planetarium…

Alpheratz (Alpha (a) Andromedae), is the star which marks the northeast corner of the Great Square of Pegasus. An apparent interloper, it used to be known as Delta (ð) Pegasi but was reassigned to Andromeda after a change of constellation boundaries in 1930. Its equine origins are laid bare in the translation of the name, which means ‘the horse’s shoulder’. An alternative name for the star was Sirrah, meaning ‘the navel of the mare’. Although it’s the brightest star in Andromeda, it shares this accolade with Mirach (Beta (b) Andromedae) and Almach (Gamma (g) Andromedae) which all shine at mag +2.1. Despite being of matched brightness, the appearance of the stars is different. Almach and Mirach have orange hues while Alpheratz is blue-white with spectral classification B8. This is a…

1 NGC 7789 Cassiopeia and Cepheus are both easily identifiable constellations because their main forms are both asterisms, Cassiopeia a letter ‘W’ and Cepheus the shape of a house. This month’s targets lie in the boundary between them. We start 2.9˚ southwest of Caph (Beta (b) Cassiopeiae) where you will locate the open cluster NGC 7789. Discovered by Caroline Herschel in 1783, it's also known as the White Rose or Caroline’s Rose. It’s an impressive object through any size of scope. At mag. +7.5 NGC 7789 presents an easy and rewarding start to this month’s tour. □ SEEN IT 2 M52 Next is fifth magnitude M52, an open cluster mid-way between Cassopeia and Cepheus. Locate it by drawing an imaginary line from Schedar (Alpha (a) Cassiopeiae) through Caph and extending…

1. The Eastern Veil The Eastern Veil, as the name suggests, lies on the eastern side of the Veil Complex and is catalogued as NGC 6992. The nebula’s spectacular form – which resembles a fish hook – is composed of bright tendrils, making it popular for astrophotographers. 2. Pickering’s Triangle Lying about 1° northeast of the Witch’s Broom Nebula, Pickering’s Triangle is a wedge-shaped network of filaments covering roughly half a degree on the sky. Surrounding it are numerous other fainter, glowing scraps of remnant material. 3. The Witch’s Broom Nebula Perhaps the most famous component of the Veil Nebula Complex, the Witch’s Broom Nebula, or Western Veil, sits practically on top of the 4th-magnitude star 52 Cygni. In the New General Catalogue it is listed as object NGC 6960.…

With the entire Universe in front of you, one of the biggest dilemmas of any observing session is deciding what to look at, so here’s our top selection of deep-sky objects you can see visually. The sketches below show what you should hope to see at the eyepiece of a scope in the 6 to 8 inch aperture range. M45 is shown as seen through binoculars due to its size. The Pleiades, M45 What A fantastic open star cluster, easily found in the night sky. Commonly known as the Seven Sisters, this sparkling cluster contains hot blue stars formed within the last 100 million years. Where Located within the constellation of Taurus, star hop from Orion to locate the red star Aldebaran. Further on from Aldebaran, your eyes will fall…

A slender and perfect crescent hanging in the fading evening sky can be a hauntingly beautiful sight. Whether it’s a naked eye view of the young Moon a few days from new, or the planet Venus spied in the eyepiece of a telescope, there is something about these sights that stirs the soul. My image entitled The Grace of Venus was of such a view; seen through the eyepiece of my 444mm Dobsonian reflector on 15 March 2017. It was 10 days prior to inferior conjunction, when Venus was lit from behind by the Sun. In order to properly convey the beauty of that view, two aspects of the image had to be just right – the geometric perfection of the crescent and the composition within the surrounding space. The…

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What do we know about the deaths of stars like our Sun? When stars like the Sun die they eventually run out of the hydrogen burning in their cores and expand into red giants. If they have planets, they can engulf part of their own solar systems. After this stage they blow off their outer layers and become white dwarfs. We have evidence that 25–50 per cent of white dwarves host planetary systems. We detect these by looking at evidence that the white dwarfs are ripping apart asteroids with their immense gravity, that then form an accretion disc around them, akin to Saturn’s rings. Dust then falls onto the white dwarf, and we can observe it within the star’s light using spectroscopy. What will happen when our own Sun dies?…