Indholdsfortegnelse for October 2020 i BBC Sky at Night

Betelgeuse’s dimming explained The star’s exceptional dimness earlier this year was observed during a Hubble study A stellar ‘sneeze’ was responsible for Betelgeuse’s unprecedented period of dimming at the beginning of the year, according to a recent update from astronomers who had been monitoring the star. They revealed that it had experienced an outburst of a huge cloud of material just before it began to dim, hiding a quarter of the star from view. Betelgeuse is a red giant and a favourite for astronomers, partly due to its prominence in the constellation of Orion and partly because it’s expected to go supernova at any time in the next 100,000 years. Its brightness is known to vary slightly, but in October 2019 it dimmed dramatically and by mid-February it was around…

The winds of Mars To continue exploring the surface of Mars we must first understand its atmosphere The film The Martian saw astronaut Mark Watney marooned on Mars after a dust-storm threatened to topple his crew’s ascent craft. Although the film (and the book it’s based on by Andy Weir) is pretty true to the science and technology that will be needed for a human mission to Mars, this opening scene played with dramatic licence. Even though Martian winds can peak at over 100kph, the atmosphere is so thin you would barely notice this buffeting a space suit. That’s not to say that a more complete understanding of Martian winds is not needed. Scott Guzewich of NASA’s Goddard Space Flight Center has led the publication of a White Paper -…

Beyond the Visible This episode was originally scheduled for September but will now run in October Astronomy is perceived to be a visual science, but should we really believe our eyes when we see beautiful images of celestial objects? The team visit Jodrell Bank Observatory to investigate how we explore the Universe using the light our eyes can’t see. And what of our other senses? By using all our senses can we expand our capacity for new discoveries? BBC Four, 11 October, 10pm (first repeat BBC Four, date and time to be confirmed) Check www.bbc.co.uk/skyatnight for more up-to-date information…

Kielder Forest Star Camp Kielder Forest Park, Northumberland, 14-19 October This autumn’s informal meet-up is planned to go ahead, with reduced numbers and no indoor talks. For up-to-date info and bookings, check kielderforeststarcamp.org Stargazing break Dunster, Somerset, 23-25 October Enjoy astronomy talks, Exmoor’s dark skies and two nights’ dinner, with bed and breakfast for £200 per person. Numbers are restricted and social distancing is in place. Contact hotel@yarnmarkethotel.co.uk. Check bit.ly/exmoordarkskies for other events in this year’s slimmed-down Exmoor Dark Skies Festival (16-31 October). Group stargazing Libanus, Brecon, throughout October An evening of stargazing for beginners, with an expert guide to show you around the night sky. Equipment is provided and COVID-19 restrictions mean that poor weather will force cancellation (instead of the usual indoor talk). Tickets are £20. bit.ly/darkskywales WHAT’S…

Interesting observations have been made in the past of transient brightening events - flares on the Martian disc. The most plausible explanation for these is that they are caused by spectacular reflections from ice, possibly in fissures or craters on the surface or from hydrated mineral areas. Observing these fascinating events requires a 150mm or larger scope, high magnification and preferably good seeing. It also helps to know the general period when they may occur. Two reported sites are at Tithonius Lacus and Edom Promontorium, a region between Sinus Sabaeus and Sinus Meridiani corresponding to Schiaparelli crater. Our analysis suggests Tithonius Lacus and a site north of Solis Lacus may produce glints this apparition. There is no guarantee that these ‘ice glints’ will be observable using predictions and they have…

KEY TO STAR CHARTS When to use this chart 1 October at 01:00 BST 15 October at 00:00 BST 31 October at 22:00 UT 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 October* Moonrise in October* *Times correct for the centre of the UK Lunar phases in October MORE ONLINE Paul and Pete’s night-sky highlights Southern Hemisphere sky guide…

Rho (r) Cassiopeiae is a mag. +4.5 star located 2.5˚ southwest of Caph (beta (b) Cassiopeiae). This verging-on-dim star appears similar to the multitude of stars around it, but it is different. All of the stars we can see in the night sky belong to our Milky Way. This gravitationally bound system contains several hundred billion suns but only those in a ‘bubble’ around the Sun, about 10,000 lightyears in diameter with the Sun at the centre, can be seen individually with the naked eye as points of light. At 8,100 lightyears distant, Rho Cas pushes that envelope. To appear this bright at this distance Rho Cas has to be around 550,000 times more luminous than the Sun, making it one of the most luminous stars known. As it’s so…

1 M103 This month’s ‘Deep-Sky Tour’ takes us through some of the wonders found in eastern Cassiopeia, a rich part of the sky thanks to the background presence of the Milky Way. M103 is an open cluster located a degree east-northeast of Ruchbah (Delta (ẟ) Cassiopeiae). At mag. +7.4 this is an easy find with any size instrument, but may look a bit underwhelming. The reason for this is that M103 is a sparse open cluster, 6 arcminutes in size, arranged with a triangular shape among a rich star background. Three brighter stars dominate the scene, the one in the middle looking orange compared to the two blue stars either side. The northern most star is a double named Struve 131. □ SEEN IT. 2 Trumpler 1 Open cluster Trumpler…

Whenever the subject of observing comets comes up, there’s always one thing that every astronomer wants to know: when’s the next bright one going to appear in our skies. Professor Laura Woodney suggests C/2017 K2 (PANSTARRS) could be one to keep an eye on. “Given the way it has been increasing in brightness since its discovery, it is currently on track to be a sixth magnitude object in 2023. While that’s not nearly as bright as C/2020 F3 (NEOWISE) is now, 2017 K2 is still at [roughly] 8.5 AU, so lots of things could happen as it nears the Sun and water sublimation [begins] in a few years,” she says. “Maybe it will break up or fizzle, maybe it will only be interesting for telescope observations – or maybe it…

How to collimate a Newtonian telescope Discover how to optically align your Newtonian and avoid distorted views Newtonian reflector telescopes are perennially popular for amateurs for their relatively low cost for any given aperture and their naturally good colour correction. But due to the loose way in which a Newtonian’s two mirrors are typically held, this design of telescope can lose its optical alignment relatively easily, especially when compared with more robust telescope designs like refractors. The process of bringing the mirrors back into optical alignment is referred to as collimation. Collimation is about getting a Newtonian’s ‘sweet spot’ in the centre of the view through the eyepiece. This sweet spot is where stars appear sharpest: it’s the circular area on a Newtonian’s main mirror where light is focused to…

The Statue of Liberty Nebula, NGC 3576 Nicolas Rolland, via El Sauce Observatory, Rio Hurtado, Chile, January and February 2020 Nicolas says: “I like this image because it represents a real pareidolia game, without good or bad answers; as well as the distinctive shape of theStatue of Liberty, you can also make out a dragon head and a crocodile side. You can let your imagination run wild. From a scientific point of view, it showcases dense knots of dark interstellar dust, bright stars formed afew million years ago and huge fields of glowing hydrogen gas ionized by these stars.” Equipment: SBIG STXL-11002 camera, PlaneWave 17” CDK astrograph, Paramount ME mount Exposure: Ha, SII, OIII 20 x 1,800” each, RGB stars 8 x 1,200” each: 36.6h total Software: CCDstack, PixInsight, Photoshop…

OCTOBER HIGHLIGHTS Interview: stratosphere observatory NASA’s Jose Siles on the 2.5m telescope attached to a helium balloon that will study galactic star formation. Watch August’s The Sky at Night The team look back over 50 years of the BBC’s Mars coverage and explore our fascination with the Red Planet. Audiobook preview: Astronomical Listen to two chapters from a new audiobook revealing some of most the incredible discoveries made in astronomy. The Virtual Planetarium Pete Lawrence and Paul Abel guide us through the best sights to see in the night sky this month.…

As The Sky at Night marks the 75th anniversary of Jodrell Bank Observatory, its Associate Director Tim O’Brien looks at how radio astronomy has changed our view of the Universe One of the more frustrating things about being an astronomer is that we can’t go and have a close look at our favourite objects. Instead, we have to gather as much information as we can while we’re stuck here on Earth. That means collecting radiation across the electromagnetic spectrum (as well as particles and gravitational waves where we can). I think of it as resembling a jigsaw - where each bit of information we collect, whether it’s visible light, radio waves or X-rays, is like a separate piece. Only when you put them all together do you get a complete…

DON’T MISS OCTOBER METEORS BEST TIME TO SEE: 20/21 October for the Orionids, 6/7 and 7/8 October for the Draconids, 10 October for the Southern Taurids October is a good month for meteor activity. The main event is the Orionid shower, named because its peak activity has the shower radiant in Orion. A meteor shower’s radiant is the position in the sky from where the shower meteors appear to emanate. In this case the Orionid radiant is near the star Betelgeuse in Orion. Orionid activity tends to start around 2 October, building slowly to a peak, which this year occurs on the night of 20/21 October. The Moon will be largely out of the way this year, leaving the night sky good and dark for meteor watching. On the night…

Located deep in the southern lunar highlands, few lunar craters are as majestically commanding as mighty Clavius. It’s a familiar feature because of its size, characteristic appearance and because it’s prominently on view between the first and last quarter phases. The start of this phase period is popular because it represents a time when viewing can be done at a relatively civilised time in the evening. The crater is massive, with a diameter of 225km. For comparison, this makes its diameter roughly equivalent to the straight line distance between Cardiff and Manchester. From Earth, Clavius has an elliptical appearance, which is a direct result of its southerly lunar latitude. The elliptical shape is due to an effect called foreshortening; if we were able to hover directly over it, Clavius would…

1. Pleiades The Pleiades, also known as the Seven Sisters and M45, are easy to see with the naked-eye, even in suburban skies, but it takes binoculars to reveal the glory of this celestial delight. In the words of Tennyson, these young, hot, blue-white stars “glitter like a swarm of fireflies tangled in a silver braid”. Compare the view as the evening progresses; as this lovely open cluster rises, more and more stars become visible. □ SEEN IT 2. Davis’s Dog From the Pleiades, navigate 7.5° eastward (down) where, in a region spanning about 3.5° by 1.5°, you will find this celestial canine. Three of the brighter stars form its head, and a string of four make its tail, including the wide double star mag. +4.2 and +5.1 Kappa-1 (g1)…

We used to think we lived in an ‘island universe’ consisting only of our Milky Way. However, many of the faint smudges once called nebulae turned out to be other ‘island universes’ too, our view of the Universe being fundamentally altered in 1924 when Edwin Hubble proved they were galaxies much like our own. As time went by, we found these galaxies liked to form groups and it was quickly observed that we were part of one, which was imaginatively named the ‘Local Group’. Our galactic neighbourhood includes two spiral galaxies (the Andromeda Galaxy, M31, and the Triangulum Galaxy, M33); two satellites of our Milky Way (the Large and Small Magellanic Clouds); the companion galaxies to M31; and several outlying galaxies (NGC 185 and 147), along with dozens of dwarf…

Back in the early months of 2020, a comet - formally catalogued as C/2019 Y4 (ATLAS) – was beginning to brighten as it drew ever closer to the Sun. The headlines had all the usual excitable language you’d expect, while enthusiastic social media posts spoke of possible naked-eye wonders to come. Out in the depths of space, though, the icy wanderer had other ideas. As it raced towards the Sun, astronomers started to notice ominous changes in its appearance; rather than brightening steadily as it neared perihelion in May this year – when it would be at the closest point to the Sun in its orbit – the comet’s glow was faltering. Soon, close-up images by astrophotographers showed the head of ATLAS – ordinarily where a solid, icy nucleus would…

Make more of the season of dark skies The new astronomy season this autumn and winter has some lovely lesser-known targets As we move into darker skies, the winter constellations hold a treasure trove of beautiful objects. Although we are often drawn to the more familiar targets (see Old favourites, opposite), it pays to seek out some lesser-known night-sky jewels that are just as rewarding. First, two highlights of the year. Mars reaches opposition on 13 October, when its apparent size is at its greatest. The Red Planet is visible for months after opposition, so observe it regularly to see its apparent diameter changing. Venus is blazing in the pre-dawn eastern sky during October, and on 14 October is joined by a waning crescent Moon. Then Jupiter and Saturn will…

Imaging lunar libration Capture contrasting images that reveal the ‘extra’ areas at the Moon’s edges The Moon is gravitationally locked to Earth, rotating once on its axis in the same period of time that it takes to orbit our planet. For us on the ground, this means we see the same familiar face of the Moon all the time. There is, however, a small variation in the Moon’s appearance over time, due to an effect called ‘libration’. This describes the cumulative effects introduced by the elliptical nature of the Moon’s orbit and its tilt relative to the orbit of Earth. The Moon’s elliptical orbit means that its orbital speed around Earth varies over time; when it’s closest to our planet at perigee its speed is highest, and when it’s furthest…

What’s so unusual about the orbit of Mars’s moon Deimos? Both Phobos and Deimos are orbiting close to the equatorial plane of Mars; most satellites of Jupiter and Saturn do that and it’s a strong indicator that the moons formed together with the planet. What’s really interesting though is that Deimos’s orbit is not exactly in the equatorial plane but a bit off, by about two degrees. That doesn’t sound much, but for orbital scientists it’s a significant amount, so we have to figure out a way to see why it’s tilted so much. Is there anything else unusual about this moon’s orbit? The tilt of the orbit is only half the story because its shape is also atypical. All orbits are elliptical, but some are more elliptical than others;…

“As soon as we saw how close it would come to the Sun, we had hopes that it would put on a good show,” said Amy Mainzer, NEOWISE principal investigator at the University of Arizona. And indeed it did. First spotted by NASA’s Near-Earth Object Wide-held Infrared Survey Explorer (NEOWISE) mission on 27 March, the icy visitor Comet C/2020 F3 NEOWISE survived the roasting of its close journey past our Sun to put on a stunning show. Through much of July we were wowed by nightly views of it streaking across from Capella to below the Plough, its twin tails stretching for millions of kilometres behind it. Glowing as bright as mag. -2 at its peak, it was seen easily with the naked eye, but was an unalloyed joy when…

Asteroids jumped Jupiter A meteorite investigation reveals that asteroids in the early Solar System may have jumped the planetary gap created by Jupiter. Previously, scientists believed Jupiter cleared out an impassable gap in the disc of dust which formed the planets, but they have now found meteorites dating from this time which contain a mix of material from inner and outer regions. Sun wasn’t born alone A new theory suggests the Sun may once have been part of a binary pair. The model could help explain the layout of icy objects in our outer Solar System, as a stellar companion would make our Sun more likely to steal outlying space rocks from other stars. The partner star would then itself have been stolen away by the pull of other nearby…

OVERALL WINNER / GALAXIES Andromeda Galaxy at Arm’s Length? Nicolas Lefaudeux (France) Photo location: Forges-les-Bains, Île-de-France, France, 2-3 September 2019 Equipment: Sky-Watcher Black Diamond 100mm apochromatic refractor telescope at f/9, iOptron iEQ30 mount, Sony ILCE-7S camera (modified), ISO 2000, 2 hours 30 minutes total exposure Judge’s verdict: “To most of us, our closest neighbouring galaxy, Andromeda, can also feel so distant and out of reach. Yet to create a photograph that gives us the impression that it is just within our physical grasp is truly magical. It’s a masterful image of the Andromeda Galaxy with a fine consideration to colour, detail and composition that makes this photograph such a worthy overall winner. I also commend the technical commitment of the photographer to capture the authentic ‘tilt-shift focus’ effect by creating…

Mars has two tiny moons. The largest is Phobos, which is 17 x 22 x 18km in size and orbits the Red Planet at a distance of 6,000km, taking 7 hours and 39 minutes to complete each orbit. Deimos is smaller, at 15 x 12 x 11km, and orbits Mars once every 1.26 days at a distance of 23,460km. Both moons are dim but well within amateur observing range, Phobos appearing at mag. +10.7, Deimos at +11.8. The problem with seeing or imaging them is Mars itself, which is very bright. That said, the best time to try is when the Red Planet appears greater than 20 arcseconds across. The best strategy is to wait for the moon you are after to be close to an elongation - its furthest…

PICK OF THE MONTH Mars Best time to see: 6 October, around 00:30 BST (5 October, around 23:30 UT) Altitude: 43˚ Location: Pisces Direction: South Features: Dark ‘albedo’ features, polar caps, weather Recommended equipment: 150mm or larger Mars is at opposition this month, a time when the planet presents its best appearance through a telescope, and due to its brilliance, to the naked eye as well. Opposition occurs on 13 October, this being the time when the ecliptic longitude of the planet is 180˚ different to that of the Sun – in other words, Mars is in the opposite part of the sky to the Sun. However, technically the best views are to be had when Mars is closest to Earth, a position which is reached on 6 October. In…

Minor planet 11 Parthenope is a large body that orbits within the main asteroid belt between Mars and Jupiter. This year Parthenope has an opposition on 23 October when it will reach mag. +9.4 in Pisces. It starts the month off in Cetus, the Whale, immediately to the west of the small misshapen pentagon that represents its head. Then, during October it slowly tracks to the southwest, ending up just inside the pointed part of the portion of Pisces which is supposed to represent the rope tying two fish together. The rope is in two parts and is ‘knotted’ at the star Alrescha (Alpha (α) Piscium). Parthenope’s brightness varies over the month, but only slightly. On the 1st it shines at mag. +9.8, and brightens to reach a peak of…

This month’s challenge is to record the current meeting between bright planets Jupiter and Saturn, and the very dim dwarf planet Pluto. Where Jupiter and Saturn are easy to spot with the naked eye, to see Pluto visually requires a large aperture instrument. There are reports of it having been seen with quite modest scopes, but from the UK at least, it’s rather low and affected by atmospheric haze. To be honest, even a large instrument might struggle with it currently. Shining around 14th magnitude, Pluto does fall within range of a camera. In fact, modern imaging equipment is pretty adept at capturing objects this faint. Light pollution may cause problems, but for this challenge at least finding the dwarf planet will be straightforward: It lies just south of the…

Our Local Group tour can begin with the naked eye which, depending on how dark your sky is, can show M31 and possibly M33. A humble pair of binoculars – 7x50s to 15x70s - will reveal the galactic disc of M31, show M33 as a hazy glow and bring out M31’s two primary companions. A wide-field telescope will improve the discs of both galaxies and make the dust lanes of M31 apparent. We used a 100mm spotting scope to track down the galaxies NGC 185 and the fainter smudge of NGC 147. Larger scopes - 10-inch reflectors and above - will make short work of these two, but won’t reveal more detail. Turning such scopes on M33 reveals some of its nebulae, like NGC 604. With a 10-inch reflector, M31’s…

Comets are thought to be among the oldest objects that exist in our Solar System. Many spend the vast majority of their lives slowly drifting through the darkness towards the edges of our planetary neighbourhood. While they’re most famous for their tails, these are only transitory features that develop as they briefly swing into the inner Solar System. Here we’ve broken down the main components of a ‘typical’ comet as it approaches the Sun 1 TAILS Occasionally a comet will develop a tail consisting of countless dust particles which have been sprayed from the nucleus as it gets heated in the light of the Sun. Sometimes a second ‘ion’ tail - composed of gases released from the nucleus - can form too. 2 NUCLEUS A comet’s nucleus is its irregularly-shaped…

IIAPY Masterclass The wonder of the Northern Lights How to construct a panorama that captures the mystery of an aurora display When my image entitled ‘The Watcher’ won the ‘Aurora’ section of the 2019 Insight Investment Astrophotographer of the Year competition I was delighted. The final image (above) shows a view looking down on Norway’s Lofoten archipelago from OffersØykammen mountain. I chose the location because I like mountains and there aren’t many photos taken from this viewpoint. During the day I climbed the peak with a friend - he’s the person standing in the picture - and took pictures of the sunset, before waiting until it got dark. I took multiple images with the aim of creating a panorama of the wonderful aurora display that was taking place. When I…

A pair of 15x70 binoculars occupies a useful astronomical niche. When they are mounted they show substantially more detail and depth than smaller handheld binoculars, but they can also, if necessary, be handheld for short periods as well. Naturally, as the Bresser Spezial Astro SF 15x70 binoculars are a new entrant to that niche, they grabbed our attention. The Spezial Astro SF 15x70s come in a rugged woven nylon case, with a padded neoprene neck strap, tethered objective lens caps, attachable rain guard-type eyepiece covers, microfibre cleaning cloth and an instruction leaflet. The aluminium body is covered with a ribbed rubber armour and has a converter bush for a tripod adaptor (not included) at the objective end of the hinge. The hinge moves smoothly, with enough resistance to prevent it…

1 Baader flip mirror II Price £175 • Supplier DHinds Tel 01525 852696 • www.dhinds.co.uk ADVANCED The constant switching between an eyepiece and camera can use up valuable imaging time, but this flip mirror reduces that delay to the turn of a knob. It has a third port to attach an autoguider and make your setup more versatile. 2 Kendrick solar filters Price from £62 • Supplier Widescreen Centre Tel 01353 776199 • www.widescreen-centre.co.uk When you’re solar observing, it’s sometimes difficult to centre the Sun in your eyepiece, but this filter’s built-in finder makes it a doddle. The filter is made from Baader AstroSolar film to ensure safe solar viewing and is available in a range of sizes. 3 Stars pinhole constellation cards Price from £14.99 • Supplier Books etc…