Indholdsfortegnelse for April 2021 i BBC Sky at Night

Perseverance lands on Mars The rover will collect rocks that will one day be returned to Earth At 20:55pm UT on 18 February NASA’s Perseverance rover landed on Mars. As well as being the most advanced robotic geologist and astrobiologist ever created, it marks the first stage of one of NASA’s most ambitious plans ever. Perseverance will create caches of Mars rock that a future mission, currently being planned by both NASA and the European Space Agency (ESA), will collect and return to Earth. “What they could tell us is monumental – including that life might have once existed beyond Earth,” says Thomas Zurbuchen, associate administrator for science at NASA. The rover used the same sky crane landing system that was developed for the Curiosity rover, touching down just north…

Measuring Saturn’s twinkling rings The light diffracting through the particles of Saturn’s rings helps astronomers measure their size Diffraction is more often than not the bane of any observational astronomer’s life. This wave property of light means that light entering the aperture of a telescope spreads out slightly – just like water waves passing through the opening in a harbour wall. For an astronomer, diffraction acts to limit the maximum resolution that can be achieved with a telescope, and a point source like a star appears surrounded by a series of rings. Exactly the same phenomenon also occurs when light waves pass and interact with a small particle. And it turns out that this effect can be exploited to do some very nifty astronomical science. Stephanie Eckert, at the Department…

DOCUMENTARY The Jupiter Enigma As Juno approaches the end of its 10-year mission, it’s a good time to catch this short but fact-packed documentary based on NASA’s latest findings about the behemoth planet that shaped our Solar System.Available on Amazon Prime ONLINE TALKS Great Comets and Great Disappointments Hampshire Astronomical Group hosts this public lecture by Nick James on comets: unpredictable and sometimes spectacular, what makes some comets ‘great’? The free event takes place on 9 April at 7.30pm. Book your place in good time and contactlindy.bryant@hantsastro.org.uk. Exploring Astronomy through Philately Join Katrin Raynor-Evans on 10 April at 7pm for an enlightening talk on stamps from around the world and how they have celebrated milestones in astronomy and spaceflight. Newtown Astronomy Society hosts the event via Zoom, which is free…

How do astronomers measure distances in space? We’re yet to send anything beyond the outskirts of the Solar System and yet we regularly talk with confidence about how far away distant stars and galaxies are. Charting celestial distances relies on a tool called, the ‘cosmic distance ladder’, which is actually a range of different interconnected techniques (see box, page 34). One of the main methods is to use standard candles – astronomical objects that have a consistent inherent brightness.’ The dimmer they appear to us compared to this true brightness, the further away they must be. Among the most common standard candles is a type of exploding star called a Type la supernova. Back in the 1930s, 19-year-old physicist Subrahmanyan Chandrasekhar was travelling by boat from his home in India…

STEP 1 Mount your tracker on a sturdy tripod that’s able to hold its weight without sagging, then level it and set it to your latitude. Make sure everything is tightened up with no slippage. STEP 2 Using its finderscope or device, align the tracker on the Pole Star. You can use a phone app to help you polar align even more accurately, which will give sharper images. STEP 3 With your target selected and focused sharply, set your camera to take a sequence of images and begin the exposures using a cable release to reduce vibrations. STEP 4 Review your images – if any are trailed check your tracker is level and aligned properly. Keep checking your camera lens has not misted over in between exposures too.…

Thuban, the alpha star of Draco, the Dragon, is perhaps a strange choice to carry this prime position title. It shines at mag. +3.7, making it a medium brightness star erring on the dimmer side. In terms of Draco, it’s easily outshone by some of the other stars that form this long curving constellation, which appears to wrap around Ursa Minor, the Little Bear, and of course the Pole Star, Polaris (Alpha (α) Ursae Minoris). Eltanin (Gamma (γ) Draconis) is 3.7 times brighter than Thuban at mag. +2.2. Thuban’s elevated status comes from the fact that Earth’s rotational axis wobbles over time. It takes 26,000 years for the axis to complete one orbital wobble and as it does so, the star which carries that important celestial position – the marker…

1 M51 Our first target is M51, the Whirlpool Galaxy, a bright spiral galaxy located close to Alkaid (Eta (ε) Ursae Majoris) at the end of the Plough’s handle. The best way to locate it is to find mag. +1.8 Alkaid (Eta (η) Ursae Majoris) and mag. +4.7 24 Canum Venaticorum as two vertices of a squat isosceles triangle with M51 located at the remaining vertice. There are two tidally interacting galaxies here, mag. +8.4 M51a (NGC 5194) and mag. +9.6 M51b (NGC 5195). They appear similarly bright through a small scope although M51a is larger. A 250mm instrument will reveal the whirlpool arms of the larger galaxy. Presented face on to us, this is an amazing sight. □ SEEN IT 2 M63 To locate M63, the Sunflower Galaxy, imagine…

After his historic flight, governments around the world invited Gagarin to visit – but not the UK. The cabinet of the day feared upsetting their US allies, so instead it was the trade unions who took it upon themselves to invite the Soviet hero to visit from 11 to 15 July 1961. Knowing Gagarin was a former foundryman, the Amalgamated Union of Foundry Workers took him on a tour of an engineering plant in Manchester. During his car ride from the airport, Gagarin was greeted by packed crowds, braving the rain to see him. He quickly ordered the roof of his convertible be put down, telling the driver, “If these people can stand in the rain, so can I.” Though he ended up soaked through, Gagarin never stopped smiling as…

Astrophotography and nightscape photography often require long imaging sessions, and with that comes a risk of your lens dewing up. If the temperature of the glass on the front of the camera lens cools to a few degrees below the dew point, then water vapour in the air will begin to condense onto the glass, causing the lens to become misted over. Any subsequent images that are taken through the lens will be useless. People often think this is only an issue during winter, but because the dew point is related to humidity levels, lenses can fog or dew up even more rapidly on a warm and humid summer evening. Preventing problems Keeping the lens glass warmer than the dew point will prevent it from fogging up, and a simple…

Astrophotography processing is about bringing out details by stretching data. This is achieved via two main editing functions: ‘Levels’ and ‘Curves’. Both are available in Adobe Photoshop and the free editing software GIMP, and it’s often necessary to perform a Levels adjustment before using Curves. Levels is used to balance the ‘Red’, ‘Green’ and ‘Blue’ (RGB) channels; this process draws out detail by brightening the image. Using Curves then manipulates the tones in your image, allowing greater contrast between light, dark and mid-tone areas. To demonstrate how the Levels function can be applied, we are using Photoshop to process a wide-field image of the Sadr Region, an emission nebula (see right). We start with a TIFF file that comprises five hours of data taken with a DSLR camera and then…

Visit www.skyatnightmagazine.com/bonus-content/CBMUG3U/ to access this month’s selection of exclusive Bonus Content APRIL HIGHLIGHTS Interview: imaging exoplanets Astronomer Beth Biller discusses the instrument she’ll use to photograph planets around distant stars. Download observing guides and charts Access planet observing forms, binocular and deep-sky tours and our guide to Southern Hemisphere stargazing. Audiobook preview: Helgoland Download and listen to an extract from physicist Carlo Rovelli’s new book about Heisenberg’s quantum revolution. The Virtual Planetarium Pete Lawrence and Paul Abel guide us through the best sights to see in the night sky this month.…

As three missions reach Mars, we look back at what Patrick Moore said about the planet and the first mission to orbit it, Mariner 9 Although I cannot remember the time when Mars was believed to be inhabited, my memory does go back to when our ideas about it were very different. The dark areas were vegetation tracts; the white polar caps were due to a thin layer of solid carbon dioxide; the surface was fairly uniform, with no high mountains or valleys; the atmosphere was made up chiefly of nitrogen; the red regions were deserts, covered with sand of the type you find at Bognor Regis. In fact, all these assumptions were wrong. The great breakthrough in our understanding of Mars was due to two spacecraft, Mariner 4 and…

My eight-year-old granddaughter, Freya, loves getting involved with my astrophotography. Remotely, she helps me to control the mount during setup, then sits back and stares intently at the screen as the mount automatically moves into position and the images start to come in. However, like many children during lockdown she is suffering from not seeing her friends, her grandparents and not being able to help me with my imaging. So she decided to keep up her astronomy skills by making a model of the Sun and planets of our Solar System. I especially love the addition of Earth’s Moon, Jupiter’s Great Red Spot and the fact that, correctly, Pluto doesn’t make an appearance.Jim Hunt, Poynton, Cheshire What fantastically detailed, fun planets those are, Jim! Let’s hope Freya can assist you…

Don’t let the child-friendly cartoon style fool you; Kurzgesagt – In a Nutshell is a YouTube channel tackling some deep scientific questions, with dozens of videos on space themes. Carefully and widely-researched, with witty scripts that owe no small debt to Douglas Adams, they’ve attracted over 14 million subscribers. Sidestepping well-worn topics in favour of a more original slant, videos include: Building a Marsbase is a Horrible Idea; Let’s Do It; Could Solar Storms Destroy Civilisation?; What if Earth got Kicked Out of the Solar System?; and Why Black Holes Could Delete the Universe.www.youtube.com…

Step 1 Two stars are orbiting one another in a binary star system. One dies to become a dense white dwarf star. Its strong gravity allows it to steal material from its neighbour, increasing its own mass in the process. Step 2 As the white dwarf’s mass nears the Chandrasekhar Limit, the star shrinks under the new material’s weight. As the pressure and temperature inside both rise, the white dwarf’s carbon and oxygen fuse into iron. Step 3 This turns the white dwarf into a fusion bomb, which soon detonates as a Type la supernovae. It’s a cataclysm so bright that it can be seen halfway across the Universe and it will briefly outshine the entire galaxy it resides in. Step 4 After the explosion, the supernova will fade over…

One of the main reasons astrophotographers buy a star tracker is to enable them to ‘stack’ images. Many beginners think this is too complicated to get to grips with, but all stacking means is taking lots of short exposures of the same object, then combining them to make a single image – the equivalent of a much longer single exposure. This can then be processed further to remove noise (unwanted artefacts), and bring out details and colours that can’t be captured in a single image. Stacking is primarily used for high-resolution images of deep-sky objects such as galaxies and nebulae, or to capture faint details hiding within the feathery tails of comets, but it can also be used to make stunning images of the Milky Way’s frothy star clouds and…

1. Melotte 111 10x50 If there is a celestial object that seems to have been ‘made for binoculars’ it’s this one. Look midway between Cor Caroli (Alpha (α) Canem Venaticorum) and Denebola (Beta (β) Leonis) and you should be able to see, with the naked eye, a misty patch of sky about 6° across. Your 10x50 binoculars will reveal 30 or so stars filling the field of view, all mag. +10.5 or brighter; there are no fainter stars, due to a phenomenon called mass segregation. □ SEEN IT 2. FS Comae 10x50 Identify Beta (β) Comae and Diadem (Alpha (α) Comae), go to a point midway between them and navigate a degree to the west. There you will find the orange star FS Comae shining around mag. +6. The magnitude…

1961. Less than four years after it had launched the satellite Sputnik, the Soviet Union was locked in a tense race with the US. The Soviets had bagged every major milestone to this point – first satellite, first living creature, first lunar impact – but they knew that if they could launch a human before the US, it would cement their reputation as the space superpower. It was the most closely run leg of the entire Space Race. Though the Soviets gave away little in public, the US were ensuring the entire world knew that their astronaut, Alan Shephard, was on course to triumph over their Space Race competitors. On 12 April 1961, Shepard’s flight was just three short weeks away when the announcement sounded out across the Soviet Union…

All times in Moscow Time (UTC +3) 5:30am: Yuri Gagarin and Gherman Titov wake. up, eat breakfast and put on their space suits.. 5:45am: The cosmonauts board the transport bus and drive to the launch site. 6:50am: The bus reaches the launchpad. A worker writes CCCP on Gagarin’s helmet so he isn’t mistaken for an enemy pilot on his return to Earth. 7:07am: Gagarin boards Vostok-1. 9:07am: Lift-off. After a few minutes the g-forces prevent Gagarin from speaking. 9:12am: Radio contact resumes. 10:02am: Radio Moscow announces the launch. 10:25am: Vostok-1 returns to the atmosphere. Shortly after, the instrument module fails to detach fully, sending the descent module into a spin. 10:35am: The craft stabilises after the connecting cord burns through. 10:49am: Gagarin ejects at 7km altitude and begins parachuting to…

April will see the first of three consecutive supermoons in 2021, making this an ideal time to discuss this often-misunderstood phenomenon and to separate the facts from the fiction. A supermoon occurs whenever a full Moon coincides with the Moon’s closest approach to Earth along its orbit. The Moon takes just over 27 days to orbit Earth on an elliptical path that takes it from its most distant point from Earth at apogee, to its closest approach at perigee. These distances can vary between 406,712km (apogee) and 356,445km (perigee). It also takes just over 29 days to cycle from one full Moon to the next. Meanwhile, Earth takes 365 days to orbit the Sun and this means it takes 14 lunar cycles (411 days) to go from one full perigee…

The Orion and Running Man Nebulae David Wills, Castillejar, Spain, 14-20 January 2021 David says: “This is a composite of two images, one for the nebula’s main part and one for core detail. I’m pleased as it wasn’t captured in the best conditions. I spent time gathering data with the luminance Alter, but it didn’t add anything so I ended up using Ha data (hydrogen alpha) as the luminance layer.” Equipment: Starlight Xpress Trius SX 694 Pro mono camera, Takahashi FSQ-85ED f/5.3 quad apo refractor, iOptron CEM60 mount Exposure: Main: Ha 62x 600”, R 56x 180”, G 41x 180”, B 50x 180”; core: R 85x 30”, G 216x 30”, B 231x 30”. Total: 22 hours 7 minutes Software: PixInsight, Photoshop David’s top tips: “Spend more time gathering Ha data for…

HOPE PROBE, 10 FEBRUARY 2021 Three Mars-bound spacecraft set off within days of each other in February – the Emirates Mars Mission, China’s Tianwen-1 and NASA’s Mars 2020 – but it was the UAE (United Arab Emirates) that first successfully entered the Red Planet’s orbit, returning this moody shot encapsulating the mysteries waiting to be unwrapped by all three. The new kids on the planetary spaceflight block, the Emirates took just six years from initial feasibility studies to sending up their atmospheric probe Hope (Al-Amal), the first step in their ambitious 100-year plan, announced in 2017, to ultimately build a city on Mars. Hot on Hope’s heels was China’s Tianwen-1, which arrived in Martian orbit on the same day that this image was taken, although it will be May before…

Most distant space rock confirmed Farfarout is now officially the Solar System’s most distant known object – at least for now. Astronomers recently confirmed the orbit of the planetoid, discovered in 2018, finding it is currently 132 times the Earth-Sun distance from the Sun. There are other objects such as Sedna, which have orbits that will travel further away in the future, however. Fireball over UK A bright ‘fireball’ meteor – one brighter than the planet Venus – was seen across the UK from Scotland to Somerset on 28 February 2021, at around 21:45 UT. Unusually, many people reported hearing a rumbling boom along with the slow-moving bright light in the sky. UK and Australia sign space deal The UK and Australia have signed a new ‘Space Bridge’ partnership, to…

The story of RMS Titanic is one that has been retold countless times following the fateful night of its sinking. During the early hours of 15 April 1912, White Star Line’s new ‘Olympic’ class liner ploughed into an iceberg with tragic consequences. In the hours that followed, more than 1,500 souls were lost. The Titanic continues to generate an unprecedented level of interest, with newly discovered evidence giving more insight into the tragedy. Many factors seem to have conspired to seal its eventual doom: consider the fire that blazed uncontrollably in one of its coal bunkers before and after it left Southampton, which could have compromised the integrity of one of the watertight compartments; or the disappearance of binoculars that were supposed to be at the disposal of the two-man…

PICK OF THE MONTH Venus Best time to see: 30 April, from 20 minutes after sunset Altitude: 3.5° (very low) Location: Aries Direction: West-northwest Features: Phase, subtle cloud shadings Recommended equipment: Binoculars Venus slowly re-emerges into the evening twilight during April, but being on the far side of its orbit from Earth, slow is indeed the word! On 12 April, it sits 3.7° northwest of a less than 1%-lit thin Moon which, at just 7.8° from the Sun, itself may be a tricky spot. Things improve as we head towards the end of April, Venus’s brightness helping the planet stand out so that it can confidently be seen against the evening twilight. Currently Venus shines at mag. –3.8. On 25 April, Venus lies 1.1° south of mag. –1.5 Mercury, Venus…

Asteroid 9 Metis reaches opposition in Virgo on 4 April, before it drifts into the large Bowl of Virgo asterism towards the end of the month. On 1 April, Metis shines at mag. +9.5 and is located 4° southeast of mag. +3.4 Delta (6) Virginis. Its apparent movement drifts it westward, arcing slightly north as it goes. Metis remains at mag. +9.5 when it reaches opposition, slowly dimming over the rest of the month to reach mag. +10.1 by the 30th. As a result, Metis is an object that should be relatively straightforward to locate and track with a small telescope over the month. During a favourable opposition Metis is able to reach mag. +8.1, putting it within binocular range. During 2021 average binoculars may struggle to see its star-like…

There are two Suns in our sky – one is real and one conceptual. The conceptual or ‘mean’ Sun is important because it allows us to stabilise the length of our days. The real or apparent Sun oscillates in position either side of the mean Sun, and this is what we are attempting to reveal for this month’s challenge. Actually, this will take more than a month – it’ll take a year! The apparent speed of the real Sun in the sky varies over the course of a year due to two effects – the axial tilt (obliquity) and orbital ellipticity of Earth. These affect the apparent position of the Sun, their combined effects generating a value known as the ‘Equation of Time’. This oddly named commodity varies in value…

Small, short focal length refractors are extremely popular and – with a weight of 2.5kg and length of 32.5cm – the Altair 72mm EDF is marketed as a travel scope. It’s no one-trick pony, however, as the 72mm EDF is sold in two different configurations. Here we review the ‘Deluxe’ version, which is supplied with a CNC-machined dual-speed focuser, rear camera rotator and extra height tube rings. The ‘Standard’ version, meanwhile, is tailored for visual use and is fitted with a white powder – coated aluminium focuser that doesn’t include the rear camera rotator. The telescope arrived in a single box, with its tube rings and a dovetail bar already in place. We noted that a carry case is not supplied. Our first impressions of the Altair 72mm EDF Deluxe…

1 Explore Scientific two-room observatory tent Price £233 • Supplier Telescope House Tel 01342 837098 • www.telescopehouse.com This pop-up tent is a great observatory solution – whether you’re looking for something to take with you into the field or a cheap home option. Set your equipment up in one of the two roofless rooms to observe at night and put a cover on for day protection. 2 Astronomik OIII MaxFR narrowband filters Price £150 • Supplier Widescreen Centre Tel 01353 776199 • www.widescreen-centre.co.uk Ideal for fast focal ratio scopes, this narrowband filter series creates clean frames for your astro imaging by cutting out all light apart from that produced by key molecules. Available in hydrogen-alpha, OIII and SII. 3 Fjallraven Byron hat Price £35 • Supplier Cotswold Outdoor Tel 01666…

What are fast radio bursts (FRBs) and why are they of interest? The name itself is a fairly good description of the phenomenon: it’s ‘fast’, a millisecond to a fraction long, it’s detected at ‘radio’ wavelengths of light, and it’s a ‘burst’ – meaning it lasts a short time and then it turns off. Some fast radio bursts (FRBs) are seen once, but we are detecting more and more that repeat. They are exciting because they are a mystery, and because they are so short in duration and yet so bright, which means they come from a very extreme environment – we think it’s likely to be around a magnetised neutron star or magnetar. These are some of the most extreme environments in the Universe, so they are scientifically interesting.…