Indholdsfortegnelse for September 2020 i BBC Sky at Night

Visit www.skyatnightmagazine.com/bonus-content/R4PLDQF/ to access this month’s selection of exclusive Bonus Content SEPTEMBER HIGHLIGHTS Interview: a new mission to Triton Planetary scientist Louise Prockter reveals her proposed mission to send a spacecraft to Neptune’s largest moon. Watch July’s episode of The Sky at Night The team explore the life and death of stars, including the latest news on Betelgeuse and how to do safe solar astronomy. Audiobook preview: The Science of Sci-Fi Are artificial gravity and time travel possible? Listen to two lectures from a new audio book on the science of sci-fi. The Virtual Planetarium Pete Lawrence and Paul Abel guide us through the best sights to see in the night sky this month.…

As several nations begin journeys to the Red Planet, The Sky at Night’s producer Simon Winchcombe looks back through the BBC archives to see how our perception of Mars has changed in the last 50 years Prompted by the upcoming missions to Mars, a chance conversation in the office led us to wonder how many past Sky at Night episodes had focused on the Red Planet. It turns out to be over 50, with the first broadcast in 1961. A further trawl through the BBC archive revealed more than 10 Horizon programmes on the same subject. Now, we thought, this was bound to be a treasure trove of images, ideas and discoveries – perfect for creating The Sky at Night’s August episode. For the next fortnight all I did was…

Email us at inbox@skyatnightmagazine.com MESSAGE OF THE MONTH Catching Comet NEOWISE I have always found everything to do with astrophotography to be the ‘here be dragons’ part of amateur astronomy. I always read the articles in the magazine but never seemed to have the time to dive in and figure it out. I did finally learn all the settings on my camera last year for an aurora trip, but my long exposures still suffered from star trails. The review of the wind-up mini-tracker in the magazine a little while ago (the Omegon Mini Track LX2, October 2018 issue) – an ideal piece of equipment for someone like me, without batteries or laptops – encouraged me to get one. Then along came Comet NEOWISE and my initial photos had blurring even…

Hubble’s free public lectures The Space Telescope Public Lecture Series goes online The Space Telescope Science Institute (STScI), the science operations centre for the Hubble and James Webb Space Telescopes, has been serving up free public lectures from its HQ at Johns Hopkins University since 2002. That sadly came to a halt when COVID-19 struck, but they’re now back in an online-only format for the rest of the year. Each event features a noted scientist discussing a different cosmic topic, usually taking Hubble’s observations as a jumping- off point. Streamed live on YouTube, there’s the chance to ask your own questions via the live chat feature. If you don’t catch the broadcast at the time, you can find a host of archived talks on their YouTube channel. Find one on…

Although many of the objects featured here are visible to the naked eye, you’ll need some help to see others. A pair of 10x50 binoculars will show you the Orion Nebula as a small haze in the centre of Orion’s Sword, the Ring Nebula as an out-of-focus star just beneath icy blue Vega, and the Crab Nebula as a tiny, smoky smudge a hand’s width from garnet red Aldebaran. A small telescope on a steady tripod will show more detail in these objects, and observing on a Moon-free night from an observing site unaffected by light pollution will improve your views even more.…

There’s an often-overlooked number that cosmologists believe holds the key to unlocking some of the deepest mysteries in the Universe. According to Richard Feynman: “All good theoretical physicists put this number up on their wall and worry about it.” Equal to approximately 1/137, it’s called the ‘fine structure constant’ and it describes the way light interacts with atoms. Except, according to new research, it might not be so constant after all. That in turn could help us to explain why the expansion of the Universe appears to be speeding up, and to predict the ultimate fate of the cosmos. It was 1998 when our understanding of the Universe began to turn upside down. The cosmos has been expanding since its creation in the Big Bang nearly 14 billion years ago.…

KEY TO STAR CHARTS When to use this chart 1 September at 01:00 BST15 September at 00:00 BST30 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 Sunrise/sunset in September* Moonrise in September* *Times correct for the centre of the UK Lunar phases in September MORE ONLINE Paul and Pete’s night-sky highlightsSouthern Hemisphere sky guide…

The Great Square of Pegasus is a cornerstone of autumn skies. It’s a large pattern, not especially bright, formed from three stars in Pegasus and one from Andromeda. The star Scheat (Beta (β) Pegasi) marks the square’s northwest corner. Scheat’s colour makes it stand out from the other corner stars, which are all hot and blue. Scheat is a red star with a spectral classification of M2.5II-llle. M2.5 indicates its spectral class, M-stars being cool and orange-red in colour. The Il-Ill indicates that it lies between a bright giant (II) and a normal giant (III). The ‘e’ tells us emission lines are present in its spectrum. Scheat is 196 lightyears away and at that distance, in order to appear as bright as it does in the night sky, it must…

1 NGC 6891 The plane of the Milky Way is a great place to locate planetary nebulae, and this month we’re hunting down six examples. We start with NGC 6891, which sits on the Delphinus-Aquila border. It lies 2.5˚ south of the star Rho (l) Aquilae. As an aside, despite being an Aquila star, Rho technically sits within Delphinus. NGC 6891 shines with an integrated magnitude of +10.5 and is around one-third of an arcminute across. A 150mm scope will show it, although it’s easy to mistake as a star. As ever with planetary nebulae, carefully increased magnification works best. The central star for this object is mag. +12.4 and is easy to see with a 250mm scope. ◻ SEEN IT 2 IC 4997 Return to Rho Aquilae and look…

When it’s close to a favourable opposition, Mars is a great imaging target. For best results you need a planetary camera that can record many still frames in rapid succession. These can then be processed using freeware programs such as AutoStakkert! or RegiStax. The larger aperture of telescope you can use, the better. Allow your scope time to cool before use, typically 1-2 hours (large scopes may need longer). When imaging, re-focus after each filter change and ensure focus is accurate. A colour camera or monochrome camera with filters, eg, RGB (Red, Green, Blue), is ideal. However, colour can suffer from atmospheric dispersion, an effect that chromatically blurs detail. This worsens the closer you get to the horizon, fine detail becoming less distinct and colour fringes appearing, but these effects…

Using Photoshop masks to enhance a nebula Discover how masks can help you apply enhancements to specific areas of your astro images Masks can be found in many image processing and editing software apps. Here we take a look at how they can be used in Adobe Photoshop to improve an image of the Heart Nebula, IC 1805. Photoshop masks allow us to cover an adjustment we make to an image with a screen and control the areas in our final image where the adjustment shows through. By using masks, we can be specific with our image enhancements. Two popular masks for astro-processing are ‘Hide AH’ and ‘Reveal AH’ masks. These are found in the ‘Layer’ menu (‘Layer > Layer Mask’) or accessed via shortcuts, which is covered later in…

Nikon Action EX 7x50 C Price £169 • Field of view 6.4° • Weight 1kg • Extras Multi-click adjustable eyecups, front and back lens covers, wide strap, rubber armouring, nitrogen-filled waterproof optics, tripod mounting, carry case • Supplier Opticron UK • Tel 01582 726522 www.opticron.co.uk At just 1kg, the Nikon Action EX 7x50 CF binoculars are light and can be used for long periods of observing without overly tiring your arms. They come with a soft padded case, but surprisingly this doesn’t have its own strap. The binoculars feature multi-click turn-and-slide eyecups that work well with and without spectacles, and a good range of adjustment for interpupillary distance (the distance between the pupils of your eyes) at 56-72mm. Like many popular binoculars, these are centre focusing (alluded to in their…

HUBBLE SPACE TELESCOPE, 2 JULY 2020 The fluffy spiral arms and the curiously large empty region at its heart are the signs of a sleepy galaxy in repose. NGC 2775, located 67 million lightyears away in the constellation of Cancer, has its furious period of star production long behind it, leaving a vacant centre where its concentrated reserves of gas were converted to stars long ago. The woolly, ill-defined spiral arms, across which are scattered millions of blue stars, are what give ‘flocculent’ type galaxies their name; in contrast to the distinct, continuous arms of grand design spirals. On the rocks CURIOSITY MARS ROVER, 6 JULY 2020 Curiosity captured this image with its Mastcam on a summer road trip that involved driving up its steepest incline yet. The rover has…

InSight’s heat probe woes In June, after 18 months, NASA’s Martian InSight lander managed to bury the head of its heat probe, HP3. HP3 was meant to hammer itself 5m into the ground last year, but couldn’t gain purchase on the loose soil. Using the lander’s robot arm, the InSight team have pushed the probe into the ground, but are now struggling to dig any deeper. Heavyweight singularity A black hole which devours a solar mass of material per day has had its mass measured. J2157 weighs 34 billion solar masses – one of the heaviest black holes known. “If the Milky Way’s black hole wanted to grow that fat, it would have to swallow two-thirds of all our Galaxy’s stars,” says Christopher Onken from the Australian National University, who…

Astronomy in times of crisis In light of the COVID-19 lockdown we look back and see that many scientific advances have occurred during periods of hardship, at times of war or plague The science of the stars is one of the great survivors in the COVID-19 emergency. People are facing real hardships, but there is an appetite for astronomy and space news to lighten the gloom. Astronomy clubs are reporting a growing interest in the hobby. And although many of the world’s observatories are closed, and universities are struggling to keep their heads above water, researchers continue to make spectacular discoveries. We shouldn’t be surprised at the resilience of our science in difficult times. History is full of examples of its survival against the odds. Indeed, modern astronomy had its…

You can photograph every stage of a star’s life with a DSLR camera and no telescope is needed. To do so you’ll need to be somewhere away from light pollution, on a clear night with no Moon in the sky. The Pleiades and Betelgeuse can be photographed with just the camera mounted on a tripod. Fitted with a standard 50mm lens, set it to take exposures of six seconds, with an ISO setting of 400 or 800. Being smaller and fainter, the Orion, Ring and Crab Nebulae will need a longer lens. You’ll need to keep the exposures short to avoid trailing, so use a higher ISO. To take more detailed photos, using longer exposures, you’ll need to mount your camera on a ‘star tracker’, a motorised mount that allows…

How do we know that the expansion of the Universe has been getting quicker of late? It’s based on a type of exploding star known as a Type Ia supernova. They detonate when a small, dead star called a white dwarf gorges on a nearby star until it becomes unstable. As this always happens at a similar stage, all supernovae of this type should explode with a similar brightness. This makes them great cosmic rulers, as dimmer ones must be further away. In 1998, two teams of astronomers were racing to measure the distances to these stellar explosions. They found that Type Ia supernovae were consistently further away than they should be, suggesting the Universe had expanded more than we’d previously believed. The search for the culprit behind this accelerated…

Purbach is a large and quite ancient crater. If you’re a fan of the shadow and light play which produces clair-obscur effects, you may be familiar with at least part of Purbach as its eastern rim forms part of the Lunar X. The other craters involved are 68km La Caille to the northeast and 68km Blanchinus to the east. Purbach is a fairly battered crater, although its eroded rim is largely intact, appearing best defined to the east. The crater’s floor sits at a depth of 3km and is largely flat in appearance apart from a series of flooded ghost craters in the northwest quadrant. The best defined of these is 20km Purbach W, slightly west of the centre of Purbach. To the south of Purbach W is Purbach A,…

1. M29 Although you can easily see this open cluster in small binoculars, this little object (7 arcminutes diameter) really lends itself to more magnification. Put Sadr (Gamma (γ) Cygni) at the north of the field of view and the cluster will be near the centre. Depending on your sky conditions, you should see up to 20 stars, including two arcs of brighter ones that form a ‘power station cooling tower’ shape. ◻ SEEN IT 2. NGC 6871 Our next open cluster is brighter and much larger, and contains a lovely variety of star colours. The brightest of these, orange 27 Cygni, is a foreground star however. At 5,100 lightyears, the young blue and white stars of the cluster are more than 60 times as distant. Notice how the brighter…

Making an observation of Mars isn’t hard. Make it useful for wider reference by recording the date and time (in Universal Time, UT). Include your name, location and conditions, making a seeing estimate through the eyepiece. The five-point Antoniadi scale (see table, right) is useful for this. Record the observing instrument along with details of magnifications used. Also record whether filters were used. Images and drawings are normally (but not exclusively) presented south-up with the following (F) and preceding (P) limb directions indicated. Features rotate into view around the F limb, disappearing behind the P limb. It’s optional but useful to include values for solar longitude (Ls) and the planet’s central meridian longitude (CM). Get these from a program such as the freeware WinJUPOS, Once completed, submit your efforts to…

Lacerta MGEN-3 stand-alone autoguider Guiding can be a daunting step in astrophotography and progressing to a laptop-controlled setup can introduce frustrations with new software and hardware. It’s worthwhile though, as guiding can lead to longer exposure times, which becomes increasingly important as you embark on deep-sky photography. So the Lacerta MGEN-3’s simpler alternative to ‘full-on’ guiding, one where a laptop and additional software isn’t needed, is exciting. Opening the MGEN-3’s box we were surprised by the lack of components. There’s the autoguider control box (a lightweight 40g), a 1.2MP guide camera, two USB leads and an ST4 guiding cable. Adaptors for different setups are also provided with the camera, providing up to 26mm backfocus for different configurations. No paper instructions are provided but there’s an easy-to-follow manual on the website.…

1 Orion filter wheel package Price £631.99 • Supplier Orion Tel 0800 041 8146 • https://uk.telescope.com ADVANCED This motorised filter wheel lets you flip between colours with ease. The USB connection allows you to automate changes, speeding up your astrophotography. Threaded for 2-inch optics, it comes with a set of luminance, red, green and blue filters. 2 Ladies heated bodywarmer Price £155 • Supplier Keis Apparel Tel 01256 704909 • www.keisapparel.co.uk Maintain your core body temperature with this bodywarmer, which has heating panels in the chest, back and collar. It operates from a 12V connection or battery pack (sold separately). Men’s version also available. 3 Teleskop Service Bahtinov focusing masks Price from £18 • Supplier Widescreen Centre Tel 01353 776199 • www.widescreen-centre.co.uk Reach the best focus possible with the help of these…

Gamma-ray burst afterglow seen across the Universe It’s the most distant optical indication of a short burst ever detected The afterglow of one of the most intense explosions in the Universe – a short gamma-ray burst (SGRB) – has been spotted further away than ever before. A recent article announced the explosion was 10 billion lightyears away, meaning the blast occurred when the Universe was just 3.8 billion years old. SGRBs are intense bursts of gamma radiation which flash across the Universe, believed to be produced by two neutron stars merging. They earn their ‘short’ moniker, however, as the optical component lasts only a few hours, leaving astronomers little time to catch this part of the outbursts before they fade away from view. When astronomers received word on 22 November…

Detecting distant moons Unseen moons may be revealed by their gravitational tug on exoplanets Astronomy entered the golden age of detecting alien worlds in the early 1990s. In the three decades since, we’ve found almost 4,300. Now, as technology advances, we are able to delve deeper into these systems, including the ability to detect unseen moons orbiting these worlds. In October 2018, using observations from the Hubble Space Telescope, astronomers announced gas giant planet Kepler-1625b could have a smaller companion orbiting it, although this detection is as yet unconfirmed and remains controversial. Discovering dark planets orbiting dazzlingly bright stars across lightyears of space is itself impressive enough; but detecting the presence of even tinier, unseen moons around these remote worlds is truly formidable. The trick is to scrutinise the data…

Beyond the Visible The team find out how astronomers are learning about the Universe by looking beyond visible light. Exploring radio astronomy, the unusual sounds that space missions have captured of the cosmos and the detection of ripples in space-time known as gravitational waves, this episode is about how so much more can be detected by studying the unseen. BBC Four, 13 September, 10pm (first repeat BBC Four, 17 September, 7:30pm) Check www.bbc.co.uk/skyatnight for more up-to-date information…

PODCASTS 13 Minutes to the Moon Live and breathe every moment of the successful Apollo 11 lunar mission (Series 1) and the fateful Apollo 13 flight (Series 2) with this atmospheric BBC World Service podcast. bbc.in/2W2ePWu Reach: A Space Podcast for Kids A weekly podcast co-created by Sandy Marshall (Solar System ambassador for NASA JPL), Reach answers kids’ questions and includes fun at-home experiments. Available on most podcast platforms. PHOTO COMP Capture the Moon Enter Jodrell Bank’s #CapturetheMoon competition by taking a Moon photo and sharing it on social media, tagging @JodrellBank and using the hashtag #CaptureTheMoon. Be sure to include your location. RADIO The Privatisation of Space Travel The Real Story’s Ritula Shah discusses the private sector’s designs on space with former astronaut Charlie Bolden and others. bbc.in/31ZtXIf CITIZEN…

For years I’ve been doing astronomy outreach in schools and have heard many questions, but there was one where my own answer surprised me. While explaining how stars live and die, a youngster asked me, “How do we know that?”. Looking out of the window at a nearby field, the answer came to me: “Because stars are like the sheep out there,” I said. “Look… there’s a young lamb jumping about, a grown-up sheep eating grass, and over there by the wall there’s a dead sheep. We can see stars being born, stars that are grown up, and stars that are dying or dead, too.” The comparison works well. We know how stars are formed, live and eventually perish because the sky is strewn with stars at different stages of…

Although astronomers could use only the nearby stars and nebulae in our own Galaxy to learn about the life cycles of stars, it’s very helpful for them to look at others much further away to confirm their observations and refine their results. Using the world’s largest telescopes and orbiting observatories, they have studied nebulae, star clusters and dying or dead stars out in the depths of space, in other galaxies far beyond our own. They have found fascinating examples of all these types of objects in the Magellanic Clouds, two of the Milky Way’s many satellite galaxies, and M31, the stunning Andromeda Galaxy, which is 2.5 million lightyears from Earth and much larger than our own Milky Way. These observations have helped improve our understanding of how stars are born,…

The most widely held answer is something called the cosmological constant (known by the Greek letter lambda, Λ). It originally appeared in Einstein’s general theory of relativity as a way to counteract gravity and keep his notion of a static Universe that isn’t expanding. Once Edwin Hubble showed the Universe was indeed expanding in 1929, Einstein labelled his cosmological constant “the greatest blunder of my life”. Yet the idea gained renewed traction after the discoveries of 1998 hinted at the presence of dark energy. At its heart is the idea that even empty space contains energy and the more that space expands the more this energy dominates. It has had the same value everywhere in space throughout the Universe’s history. Quintessence is the other leading dark energy contender. It says…

PICK OF THE MONTH Mars Best time to see: 30 September, 02:00 BST (01:00 UT)Altitude: 43˚Location: PiscesDirection: SouthFeatures: Dark ‘albedo’ features, polar caps, weatherRecommended equipment: 150mm or larger Mars now dominates the night sky, its gorgeous salmon-pink colour glowing like an ember within the constellation of Pisces. Fast approaching a favourable opposition in the middle of next month, Mars can be seen doing several remarkable things during September. On 10 September the planet’s apparent eastward motion against the background stars stops as Mars reaches what’s known as a stationary point. After this Mars will appear to move west until it reaches its next stationary point in mid-November. In reality, Mars hasn’t changed direction at all, the effect is simply a consequence of Earth’s own orbital motion relative to that of…

Minor planet 19 Fortuna reaches opposition on 11 September in the constellation of Pisces, south of the faint asterism of the Circlet. Shining at mag. +9.2 it should be a relatively easy target for a small scope. It tracks southwest throughout September, pushing Fortuna into the neighbouring constellation of Aquarius by the month’s end. Fortuna’s track location also keeps it relatively close to the Solar System’s outermost planet Neptune throughout the month. Medium wide images of the area taken several days apart should reveal the motion of both bodies. Neptune will appear brighter than Fortuna at mag. +7.9. 19 Fortuna is a large main belt asteroid, with a diameter of 225km. It’s quite dark in appearance with an albedo – how much light it reflects – of just 3.7%. Its…

Get to know the constellations of autumn Join our easy, naked-eye tour of the brighter, recognisable constellations that are visible in the September night sky Although it’s hard to believe, we’re only a matter of weeks from the equinox, on 22 September, and the start of autumn. As the seasons change let’s take a tour of this month’s skies and we’ll see spring and summer’s stars making way for the stars of the dark-sky season. Just take this article with you as you head out and keep turning to your left, from your starting point facing northwest, hopping from star to star as you read along. As you do, you’ll see the seasons’ stars change before your eyes. This constellations guide is accurate for the UK at about 22:00 BST…

Catch a month of beautiful conjunctions Make the most of these wonderful photo opportunities with a smartphone or a camera Conjunctions occur when two or more heavenly bodies appear close to each other in the night sky. It could be a conjunction of two or more planets, or planets and the Moon, or Solar System objects near deep-sky objects. This month several conjunctions take place, and we’re looking at the best ways to capture them. Solar System conjunctions are great targets for astrophotography because they often involve bright subjects. The planets Mercury, Venus, Mars, Jupiter and Saturn fall into this category. Add the Moon and you have objects which are bright enough to be captured on a smartphone or a more sophisticated camera. The Moon is a great conjunction maker;…

What is a gamma-ray burst (GRB)? When a massive star exhausts all of its fuel, it collapses under its own weight and dies in a supernova. When the star is very, very massive and is spinning rapidly at the same time as collapsing, it forms a black hole at its core and sends out jets of energy. A gamma-ray burst occurs when a very massive star collapses like this and we are looking along the line of the jet. We’ve got this beam of radiation pointing directly at us. It is tens or hundreds of times brighter than a normal supernova. GRBs can outshine entire galaxies. What are the main questions about how GRBs are formed? The big question has been how you get a star that is that big…