Indholdsfortegnelse for November 2019 i BBC Sky at Night

VISTA, EUROPEAN SOUTHERN OBSERVATORY, 13 SEPTEMBER 2019 There’s a lot going on in the Large Magellanic Cloud (LMC), one of our nearest galactic neighbours. And the astronomers at the European Southern Observatory have been tasked with figuring out exactly what’s happening. They’re using the Visible and Infrared Survey Telescope for Astronomy, or VISTA (a modified Ritchey-Chrétien telescope with a 4.1m-wide main mirror, at the Cerro Paranal site in Chile), to keep a close eye on the LMC and, in the process, have captured this magnificent image. The LMC floats around 200,000 lightyears from the Milky Way and the constant activity inside is due to it being home to vast clouds of dust and gas that are combining and collapsing to form new stars. VISTA allows astronomers to observe the LMC,…

Water has been found in the atmosphere of a planet in the habitable zone of another star. K2-18b is a super-Earth eight times the mass of our planet and is currently the only other known world to have both water and the temperatures needed to support life. “Finding water on a potentially habitable world other than Earth is incredibly exciting,” says Angelos Tsiaras from University College London, who led the study. “K2-18b is not ‘Earth 2.0’ as it is significantly heavier and has a different atmospheric composition. However, it brings us closer to answering the fundamental question: Is the Earth unique?” Tsiaras’s team took a look back at archived images of the planet and its host star – a red dwarf named K2-18 – taken by the Hubble Space Telescope.…

It’s the first time a two-dimensional surface map of a planet has been derived from single-point observations Astronomers have now discovered around 4,000 extrasolar planets, a number of which are believed to be small, rocky worlds like Earth; some of these like TRAPPIST-1e may even be habitable. The usual detection methods – radial velocity and transit – can give bulk measurements such as mass, diameter and orbital distance from the star. From this information, astronomers can begin to make estimations about a world’s climate and whether it would be able to host oceans of liquid water on the surface. But what we’d really want to do is to actually see such a terrestrial exoplanet – to make out its swirling clouds and continental features in the way even modest amateur…

A supernova remnant is the material of a star that’s ejected into space when it explodes. There are two main ways in which a star can become a supernova. One is when a big star nearing the end of its life, having burned all its fuel, collapses in on itself, with the inrush of material rebounding off the star causing it to explode. The same process can happen in a binary star system when a high-mass, white dwarf star collects material from a companion red giant star. Once a critical mass is attained, the white dwarf becomes a supernova. When the star explodes all the material that made it up is expelled into interstellar space at high speed. It heats up and the shockwaves end up creating the structures we…

Venus Best time to see: 24 November, 30 minutes after sunset Altitude: 4º (low) Location: Sagittarius Direction: Southwest Features: Phase, faint atmospheric markings Venus is currently an evening object, which appears to be slowly pulling away from the Sun. On 1 November it shines at mag. –3.8 and sets approximately 50 minutes after the Sun goes down. Through a telescope the planet appears to show a 93%-lit gibbous disc which is 10 arcseconds across on 1 November. As Venus slowly moves further around its orbit on the distant side of the Sun, the angle between Earth, the Sun and Venus changes. As a result, by the end of November, Venus shows a marginally reduced phase of 89% and a fractionally larger disc, 11 arcseconds across. The position of Venus deteriorates…

Asteroid 4 Vesta was discovered by Heinrich Olbers on 29 March 1807, the last of the so-called ‘Big Four’ asteroids discovered in the six-year period between 1801 and 1807. The previous discoveries were 1 Ceres, 2 Pallas and 3 Juno. The next discovery, 5 Astraea, didn’t occur until 1845. Vesta is the second most massive and second largest body in the asteroid belt, only being surpassed by Ceres. A lot of information is known about Vesta thanks to the highly successful Dawn mission that entered orbit around the asteroid on 16 July 2011. In addition, collisions which formed large craters on the object have resulted in debris which has fallen to Earth. Known as Howardite-Eucrite-Diogenite (HED) meteorites, these have augmented our knowledge of this fascinating world significantly. It takes Vesta…

Few can resist the natural beauty of a sunset and the beautiful colours appearing at this time of year are truly sublime; deep blue vignetting into yellow, orange and red. Viewing the setting Sun without filters is not recommended as harmful radiation can still cause eye damage. A camera however, can fare better. This month’s challenge is simply to produce a spectacular image of the Sun’s last moments before it slips beneath the horizon. And of course, there’s a special sunset on 11 November as Mercury will still be in transit at sunset (see page 46) As ever it pays to show caution. When the Sun is less than a degree above the horizon, the thicker layer of atmosphere its light has to pass through attenuates its output. It also…

The overview effect is a term used to describe the profound cognitive shift in awareness and worldview as a result of seeing the Earth from and in space. It was first coined by Frank White in his 1987 book The Overview Effect: Space Exploration and Human Evolution. White undertook interviews with 25 astronauts and cosmonauts, and discovered a similar response that came from their experience in space. His interviewees described the beauty and fragility of the planet and, with their view of our planet as a whole, the concept of nations and conflicts were in turn minimised. What’s more, this change in perspective remained with astronauts and cosmonauts during their life. Although he died before the term was coined, the words of the first human in space, Yuri Gagarin, provide…

A few days before or after New Moon, the beautiful crescent Moon is visible. Look more carefully and you soon realise that the ‘dark’ part of the Moon can just be seen feebly illuminated. This is known as earthshine and it’s due to light reflecting off the bright Earth back onto the Moon and gently illuminating it. The glorious naked-eye view of the Moon’s crescent – with the dark portion of the disc illuminated by earthshine – looks absolutely spectacular, but capturing that moment on camera is much more problematic. The box of three images (right) illustrates the point quite clearly. A short exposure, like the first image on the left, captures the detail in the bright crescent while the earthshine is too faint to be seen. The middle image…

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An interstellar interloper has been spotted entering our Solar System, the second time such a distant visitor has been discovered. The space rock, now named 2I/Borisov was discovered on 30 August 2019 by astronomer Gennady Borisov at the MARGO observatory in Nauchnij, Crimea. As the object was observed coming in at an extreme angle to the plane of the planets – later measurements would put it at around 40° – the space rock was quickly flagged as a potential interstellar visitor. A bulletin was soon sent round, urging the world’s telescopes to take a closer look. “The comet’s current velocity is high, about 150,000 km/h, which is well above the typical velocities of objects orbiting the Sun at that distance,” says Davide Farnocchia of NASA’s Center for Near-Earth Object Studies…

The mysterious mechanisms behind the aurora could soon be revealed, as NASA has now awarded a $1.7 million grant for a set of rocket-borne experiments, run by Clemson University in South Carolina. Its Ion-neutral Coupling during Active Aurora (INCAA) project will launch a series of rockets in 2021 and 2022, each containing a suite of instruments that will directly investigate the region of the upper atmosphere where aurorae form. “One of the things my group will look at, in particular, is how the flow of energy from distant space enters the atmosphere and where it goes from there,” says Stephen Kaeppler of Clemson University and principal investigator of INCAA. “Our research will probe deeper into how the Earth’s atmosphere regulates this energy transfer and also what effects this energy input…

Astrophotography is an expensive hobby, especially for students. Having returned to university later than planned, I have acquired a decent setup on a budget, thanks to second-hand equipment. The urge to spend my student loan on a CCD and triplet apochromatic refractor remains, however I am generally happy with my DSLR camera and ED80 telescope. I know that there’ll be 30 years between me and the ‘dream’ kit I’m saving for. I could afford it sooner, but only if I move into the cardboard box it arrives in. In the meantime, I had been thinking of ‘astromodding’ my Canon 700D – that is, removing the infrared (IR) blocking filter to allow the full spectrum of light to be captured. Seduced by the beautiful images posted in various social media groups,…

Transits of both Mercury and Venus can be used to measure the distance between Earth and the Sun; the Astronomical Unit (AU). The mathematical basis for this is the solar parallax effect you get from observing a transit of one of the planets from different locations on Earth’s surface and seeing how much the planet’s position appears to vary against Sun’s disc at a particular moment. Then, using some simple triangulation trigonometry, you can calculate the distance from Earth to the Sun. The Citizen Transit of Mercury (ToM) project is an attempt to do the same during Mercury’s transit this month, ostensibly to teach school kids how to calculate the size of the Solar System using observations and some fairly basic maths. “We’re going to have about 20 observing sites…

KEY TO STAR CHARTS When to use this chart 1 November at 00:00 UT 15 November at 23:00 UT 30 November 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 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 November* Moonrise in November* Lunar phases in November MORE ONLINE Paul and Pete’s night-sky highlights Southern Hemisphere sky guide…

Menkar (Alpha (a) Ceti) is the second brightest star in the constellation of Cetus the Whale or Sea Monster. (The brightest is Deneb Kaitos). From the UK, Cetus is best seen in the autumn or winter months. Menkar translates as ‘nostril’ and it’s located in the head of Cetus. The head resembles a distorted pentagon formed from Menkar, Kaffaljidhma (Gamma (g) Ceti), Nu (n), Mu (m) and Lambda (l) Ceti. Menkar has the spectral classification M1.5 IIIa indicating that it’s a cool, luminous red giant star with a ‘surface’ temperature of around 3,522˚C. Its distance from the Sun is 250 lightyears and its luminosity is around 1,450 times that of the Sun, much of its output being in the infrared part of its spectrum. In visual wavelengths it’s around 380…

1 NGC 1535 Our Deep-Sky Tour takes us along the banks of the river Po, mythologically represented by the constellation Eridanus. Our first stop is planetary nebula NGC 1535 which lies 4˚ east and 1˚ north of mag. +3.0 Zaurak (Gamma (g) Eridani). This is a lovely object that shines at mag. +9.6. A 150mm (6-inch) scope will show it as a bright inner disc surrounded by a broken dimmer outer ring. A 250mm (9-inch) scope shows a structure over half an arcminute across with the central disc measuring 20 arcseconds. The central star is evident through a 250mm scope. The object has a blue-green hue and is informally titled the Ghost of Neptune. □ SEEN IT 2 NGC 1407 Next is galaxy NGC 1407. Head back from NGC 1535…

In spite of overwhelming evidence, climate sceptics continue to question the role of humanity in global warming. As scientists, astronomers need to reiterate the strong findings on climate change from the scientific community. Astronomers have a history of advocating for science at personal risk, and we can take a lesson from this history. In the 17th century, Galileo Galilei’s observations of the phases of Venus and Jupiter’s moons provided evidence that contradicted prevailing religious thought about man and God, and our place in the Universe. In 1616 the Roman Catholic Inquisition ruled that the heliocentric idea that Earth orbited the Sun (as proposed by Copernicus in 1543) was heretical, a ruling which held until 1835. While Galileo first complied with the Church’s orders, in 1632 he published a book showing…

Step 1 Cover your work area with something in case of spills. Next, ensure your container is on a level surface and pour some liquid latex into it so that the whole base is covered with a thin layer. Allow this to dry to provide the base layer before continuing. Step 2 Decide how big your crater will be in relation to the base so you can fit all its details on it. Cut out a paper circle and gently draw round it on the latex with a marker pen to act as your guide. Step 3 Pour some liquid latex into a bowl. Then mix in some of the flour, a little at a time, until you have a paste which can hold its own shape without being too…

Chasing the Moon Alessio Vaccaro, Cefalù, Sicily, Italy, 26–27 August 2019 Alessio says: “It took 100 shots, taken over the course of 90 minutes, to capture the movement of the Moon against the stars in the background. It was a real challenge but the end result was more than worth it. I had to make sure that the telescope was perfectly tracking the Moon at each shot and, because of the unusual star trails, I had to align the frames manually rather than with automatic tools.” Equipment: Canon EOS 5D camera, TS Optics 80/480mm apo refractor, Sky-Watcher HEQ5 mount Exposure: ISO 1600, f/6, 4”, no filters Software: Python, Photoshop Alessio’s top tips: “Images like this are obtained through a lot of practice, patience and resistance to the cold. This photo…

For many telescope enthusiasts, a long focal length, 6-inch (150mm) refractor like the Altair 150EDF represents the ultimate piece of equipment, perhaps offering the largest sensible aperture that is practical for dedicated amateurs. The proportions of the 150EDF are impressive, an f/8 lens giving a focal length of 1,200mm, making it a long scope, especially with the dew shield extended. We mounted it onto our permanent pier (post) in a compact observatory and it quickly dominated the observing area. Long refractors make for some interesting observing positions, so it’s prudent to think about how and where you might mount and use one. After allowing a couple of hours for the scope to adjust to the ambient temperature we performed a star test to make sure the optics had survived the…

What did your study look at? We analysed 500kg of Antarctic snow, looking for an isotope called iron-60, a radioactive form of iron which contains four extra neutrons. This is mostly produced in supernovae, so finding iron-60 means there’s direct evidence we have interstellar material falling onto Earth. Why did you use Antarctic snow? Antarctic snow is one of the purest materials you can find on Earth. There are almost no contaminants from terrestrial sources in the snow. The snow fall rate is also very low, with only a few events a year that precipitate snow. That means the dust is concentrated, so we don’t need large amounts of snow to find the elements we are looking for. How did you get the snow? We have colleagues in Antarctica from…

A rapid transition is sweeping through six formerly sedate galaxies as their cores burst into life, according to a recent set of observations. The galaxies are LINER (Low-ionisation nuclear emission line region) galaxies which are partially active, meaning some of their light comes from glowing hot gas around their central black holes, as well as the stars. During just nine months of observations with the Zwicky Transient Facility in California, astronomers spotted six LINER galaxies that appear to be on the cusp of transforming into the most energetic of all active galaxies, quasars. “Observing six of these transitions, all in relatively quiet LINER galaxies, suggests that we’ve identified a totally new class of active galactic nucleus,” says Sara Frederick from the University of Maryland, who led the research. “Theory suggests…

Astronomers have just discovered what our neighbouring galaxy Andromeda last had for lunch. Andromeda has been snacking on dwarf galaxies for billions of years, and recent observations have now tracked down the stellar leftovers of its previous meals. “By tracing the faint remains of these smaller galaxies with embedded star clusters, we’ve been able to recreate the way Andromeda drew them in and ultimately enveloped them at different times,” says Dougal Mackey from the Australian National University, who co-led the study. These traces show that Andromeda was recently feeding from its plane of satellite galaxies (see yellow orbit in the images, right). This surprised astronomers, as these galaxies are at right angles to those it fed on over 10 billion years ago (see pink orbit in the images, right). However,…

My research is on the formation of planets, and I use a variety of techniques to investigate how they grow. I get asked a lot about my methods, so here are a few of the most commonly asked questions. Where do planets form? Planets form in discs made of gas and dust — called protoplanetary discs — that swirl around their central star. 4.6 billion years ago our own Sun would have had one of these discs, which went on to form the planets. How does the formation process work? There are two ways we think planets form. The main way is via core accretion — where the dust in a disc collides, sticks together and grows to form a planetary core. As this core becomes more massive, its gravity…

A new perspective The community of amateur astronomers will not need reminding of the frustrations of this great hobby but we will always return to the telescope because of one awe-inspiring view. As a young boy, two simple lenses, some postal tubes and a cotton reel enabled me to build a rather crude refractor with which to observe Jupiter and the Medici moons just as my hero, Galileo, had done. Following this revelatory experience, a series of second- hand refractor, reflector and Cassegrain telescopes have provided a lifetime of astronomical interest. While these instruments gave me satisfactory views of the Moon and planets, the majority of deep-sky objects remained invisible or at best faint smudges of light. This long-standing frustration has been alleviated through my ownership of a new Stellina…

To the Romans, the planet Mercury was Mercurius, the messenger of the gods. To modern astronomers, it’s the smallest, hottest and fastest-moving planet in the Solar System, and the one that’s nearest to the Sun. Rarely glimpsed by sky-watchers because it’s usually lost in the Sun’s glare, Mercury will nevertheless provide one of the most arresting celestial sights of 2019 when, on Monday 11 November, it will pass across the face of the Sun. It’s an event that’s among the rarest of predictable astronomical phenomena. From Earth, only Mercury and Venus, the two innermost planets in the Solar System, can be seen to transit the Sun’s disc. For observers in the UK the event will begin around 12.35pm and continue past sunset, at around 16.22pm. Even though the UK won’t…

As Bonfire Night approaches it’s a great time to take a look at some of the biggest bangs in the Universe – supernovae. There hasn’t been a visible supernova in our Galaxy since 1680, but we can see their remnants – the gas and dust left behind in their wake. Often diffuse, with wispy strands of nebulosity, supernovae remnants can be among the most challenging targets for the visual observer. The 5 November itself is probably not the best time to chase after these targets, as the smoke from bonfires and firework displays will fill the sky with haze. This year, the Moon will be around its first quarter, making these faint objects even more difficult to see, so you will have to wait until after it sets at around…

2 Saturday This evening’s 37%-lit waxing crescent Moon lies 5.5° to the east of mag. +0.9 Saturn. 5 Tuesday The crater Lalande, the subject of this month’s Moonwatch (see page 52), is visible this evening. 8 Friday This evening presents an opportunity to see the clair-obscur effect known as Cassini’s Moon Maiden. The Maiden is formed within the headland at the southern edge of Sinus Iridum, a feature known as Promontorium Heraclides. 9 Saturday Ganymede’s shadow begins to transit across Jupiter’s disc from 15:10 UT. This tricky observation takes place in daylight. 10 Sunday The Northern Taurid meteor shower reaches peak activity. Although the shower has a weak ZHR (Zenithal Hourly Rate) of just 4 meteors per hour, the peak is broad, lasting for several days. 11 Monday The planet…

Transit of MERCURY BEST TIME TO SEE: Observe on 11 November from 12:00 UT, first contact occurs at 12:35 UT November plays host to an exciting event known as a transit of Mercury. This involves the planet appearing to cross the disc of the Sun as seen from Earth. We look at the general aspects of a Mercury transit on page 30. Here, we’ll concentrate on the observational aspects. The transit circumstances are shown on the diagram (right). This provides times for the key stages – first, second, third and fourth contacts – together with the point of greatest transit. Observing the transit requires a scope fitted with safety filters. The scope’s finder will need to be capped or removed for safety. Safety filters include those for viewing in white…

1. Honores Friderici 10 x 50 Before the IAU formalised the 88 modern constellations, several astronomers invented their own. Johann Bode created Honores Friderici (Frederick’s Glory) in 1787 to honour Frederick the Great of Prussia. It takes the form of a ceremonial sword and writing quill, wreathed in laurel. Binoculars allow you to appreciate the varied colours of the stars in this region, ranging from ruddy 8 Andromedae to blue-white Omicron (o) Andromedae. □ SEEN IT 2. NGC 7662 15 x 70 Identify Iota (ι) Andromedae, part of the hilt of Frederick’s sword, and scan 2° west to 13 Andromedae. You’ll find NGC 7662 half a degree to the south-southwest. It looks like an 8th magnitude star, but 70mm binoculars should help to bring out the blue-green tint that distinguishes…

On 14 November 1969, the skies were grey over Florida as the crew of Apollo 12 readied to launch to the Moon. It was raining, it was windy, and the weather was getting worse. Though the crowd that had gathered on the coast was far smaller than the one for Apollo 11, there was one vital person in the audience – President Richard Nixon. Whether his presence or the threat of a month-long delay until the next launch window pushed them on, the mission controllers decided to launch despite the bad weather. At 11:22am local time, the Saturn V bearing Charles ‘Pete’ Conrad, Alan Bean and Richard Gordon launched and began to climb into the overcast sky. Thirty-six seconds later, a flash of white light surrounded the rocket. Inside the…

Studying the shadows cast by features on the Moon can reveal so much about the structure of the lunar landscape. From the shadows we can see differences in wall height along crater rims and infer the height of crater walls themselves; details that are not apparent under a high Sun angle. If you know the exact angle of the Sun, you can even use basic trigonometry to calculate the height of a feature based on the shadow that is being cast. Building a model crater can become a fantastic teaching tool for outreach sessions and makes a great school project. It is important to study these features at different Sun angles as the length of the shadows change as the Sun angle changes in association with the changing phases of…

This month’s transit of Mercury is an infrequent enough event to make it worth pushing the boat out for. It’s weather-dependent, but assuming you do get some clear skies on the afternoon of 11 November, imaging the transit is going to be a high priority. Bear in mind that the next one doesn’t occur until 13 November 2032. If you do get suitable weather conditions, the good news is that the event isn’t too hard to image. To do so you’ll need a telescope which has been prepared for solar imaging. For white light imaging this will necessitate covering the scope’s front aperture with a white light solar filter. This is constructed from inexpensive solar safety film, but pre-made versions are also commercially available. If your scope has too large…

With the advent of modern smartphones it wasn’t long before Celestron brought out its Astro Fi range where, using Celestron’s free SkyPortal app, you can fully control an altazimuth Go-To computerised telescope without the need for the traditional handset. The range went up to the Astro Fi 5 Schmidt-Cassegrain telescope (SCT), which we reviewed in June 2018, but now Celestron has added a 6-inch (150mm) SCT to the range and we’ve been eager to test this new model. The Astro Fi 6 is an SCT with a focal length of 1,500mm that gives a focal ratio of f/10. The optics have Celestron’s proprietary StarBright XLT coatings, giving better contrast for planetary and lunar observations, along with higher light transmission for deep-sky targets. The long focal length fits neatly into a…