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The nights are getting much better in terms of astronomy, twilight ends at a reasonable hour and so now would be a good time for novices to familiarise themselves with some important and prominent constellations such as Pegasus, Perseus, Andromeda, Cygnus and Lyra. Get yourself a star map and get out there! The so called “Summer Triangle” of Deneb, Altair and Vega is still prominent, despite the fact that it is now autumn! It is worth scanning the area of Cygnus to marvel at the milky way and also to see if you can spot any of the dark nebulae that are visible (or invisible I suppose) in the area. Find some of the many Messier objects such as the Andromeda Galaxy (easily visible through binoculars even from Derby itself) or M15, a globular cluster. Instead of looking at the main constellations, why not focus on some less well known ones, for example, Vulpecula. You will find a pair of binoculars helpful since this relatively modern constellation (invented in the 17th century by Hevelius) is faint and small. Let your eyes become fully dark adapted before starting your search. It lies between Cygnus and Aquila. Check out alpha, it is an orange-red double star. See if you can find M27 – the Dumbell Nebula, a planetary nebula. There have been two navae discovered in Vulpecula, keep your eyes peeled, you never know when the next one will occur…
Mercury and Venus are not well placed, they set in the twilight, shortly after the Sun. Neptune and Uranus are in the South, mid evening, in Capricorn. Saturn and Jupiter are well placed for observation by midnight.
Jupiter and Saturn are visible all night by the middle of the month. Also by the middle of the month, Mars rises in the small hours. Mercury is a difficult morning object, make sure that the Sun has not risen if you are searching for it using binoculars. By the end of the month, it will rise about 1 hr 20 min. before the Sun. us and Neptune are now setting by 9 p.m. In the Eastern sky, the familiar and bright winter constellations of Taurus and Orion are rising. Enough is known about these from previous “sky scenes” so I will turn to the northern skies for the constellation focus for this month. Draco, the dragon, is large in area but faint in stars. It is sprawled between the two bears and is said to represent the guardian of the golden apples in the garden of Hesperides. The main star is called Thuban and was the pole star around 4700 years ago. It is a binary star but you need a spectroscope to discover this since the components are too close together to see as separate entities. Gamma Draconis, named Eltamin, Was a highly important star to the ancient Egyptians. Apparently, in the period around 3500 BC it rose in line with the centre passages of some major temples and is thought to have been used to align one of Ramesses’ temples in about 2500 BC. It lies almost exactly at the zenith of the original Greenwich observatory and was extensively observed by James Bradley, the third Astronomer Royal, leading him to the discovery of the aberration of light. There are several meteor showers in Draco, the best known are the Quadrantids (max on 2-3 Jan, normal range 28 Dec. – 4 Jan.).
The best placed planets this month are Jupiter and Saturn, their bright discs dominating the southern view. Mars is still an object for insomniacs, dedicated observers or those on night shift! Venus will be shining bright in the western sky , setting about 3 hours after the Sun. Taurus and Orion will be conspicuous in the south, with Pegasus slipping further to the west with each passing day. Lepus, the Hare, is a little known constellation below Orion. Its origins as a constellation are a little vague, there are several suggestions. In early Egyptian astronomy, it was part of the boat of Osiris and was a shed to the ancient Chinese! Julius Schiller portrayed it as Gideon’s Fleece. The main star is called Arneb and is just brighter than magnitude 3. It is yellow-white and has a faint companion – you would need at least a 6” telescope to see it convincingly. Beta, called Nihal, is also a binary, needing a decent sized telescope however gamma is a wide double star, just within binocular range. The colour contrast for this one is good, the primary is yellow-white, the companion is orange-white. R is a long period variable star also known as “Hind’s Crimson Star”. Hind described it as “… resembling a blood drop on the background of the sky.” It is easy to see in binoculars when at maximum brightness (sorry, I do not have details about whether or not it will be at maximum at this time, see if you can find it anyway). The other object of interest is M79, a globular cluster. It should just be visible in 10X50 binoculars as a hazy patch but its proximity to the Southern horizon makes it a difficult object for us here in Derby.
Facing southwards, the most prominent constellation is Orion. It is easily recognisable because of the 3 distinctive bright stars which for the asterism of Orion‘s belt. Orion is also easy to spot because it is the only one in the northern hemisphere to contain two first magnitude stars. Top left is Betelgeuse, a red giant star whilst bottom right is Rigel, which is much whiter in colour. Down and to the left of Orion lies the unmistakable Sirius - the dog star. This is reasonably close to us, a mere 26 LY away. It has a white dwarf companion, the Pup, which is hard to spot owing to the glare of Sirius. Sirius is the brightest star we see, apart from the Sun. Since it is always rather low in our skies, the thickness of atmosphere through which the light must travel, causes Sirius to twinkle violently on most nights, changing colour rapidly. North east of Orion lies Gemini, with the two bright stars of Castor and Pollux, the twins of mythology. Search out M35, an open star cluster at the feet of the Twins.
The arrival of February sees the constellation of Cancer high in the sky. This gives an excellent opportunity to observe Praesepe, the Beehive cluster, object no. 44 in Messier‘s catalogue of fuzzy blobs in the sky! From a dark site it is visible to the naked eye. It is also known as the manger (from which the asses - gamma and delta Cancri feed). Galileo observed this with his telescope and counted 36 stars in the cluster. Using 10 X 50 binoculars, around 75 are visible. It was well known in ancient times and was used as a means of weather forecasting:
A murky manger with both stars [g and d] shining unaltered is a sign of rain - Aratus. A further object, M67, is visible as a nebulous spot in binoculars. It is an open star cluster and a red and orange star can be resolved using a small telescope. Between Cancer and Orion lies Canis Minor, the lesser dog. Its main feature is Procyon, the 8th brightest star in the sky. This, like Sirius, is a difficult double, it has a magnitude 9.5 companion. It took the 36" Lick telescope to see this in 1896. Also becoming visible this month is Leo, on of the classic spring constellations. Insomniacs could spend some time observing the large number of deep sky objects associated with this constellation in the clear winter sky.
Taurus and Orion are sinking low in the west by 10 p.m. this month. Castor and Pollux in Gemini are still noticeable whilst Capella is prominent in the north-west. Regulus and the ‘Sickle’ asterism of Leo are obvious in the south and below it is the constellation of Hydra, with no bright stars. The ‘Plough’ of Ursa Major is well placed for observing the galaxies in this part of the sky. In the east, Spica and Arcturus are rising, always a sign that Spring is on its way. Jupiter and Saturn are sinking lower in the west and will set around midnight by the middle of the month. Mars is a morning object, together with the elusive Mercury and Neptune. The latter two will not be easy to spot. The second half of this month will be good for deep sky observers – the Leo/Virgo galaxies are high in the sky and the Moon will be out of the way by midnight after the 18th. In Leo, the brightest of the galaxies are M65 and M66, both about magnitude 9. They are spiral galaxies but M65 is actually edgeways on to our line of sight and thus appears as an elliptical galaxy. They will, however, appear as little more than misty patches of light in small telescopes. If you relish a more difficult challenge, try to find M95 and M96. In terms of double stars, find gamma Leonis and use a high power magnification. You should see that it is a magnificent pair of orange-yellow stars. But, how about a sextuple star! Castor, the brightest star in Gemini, appears as a single bright star to the naked eye. Using a moderate size telescope and a high power, you find that it is in fact two blue-white stars. Looking carefully with a larger telescope, it is possible to see a third star in the system – orange-red, faint at magnitude 9. Using a spectroscope, all three stars are found to be doubles, too close together to be separated using even the largest of telescopes.
The two bears, Ursa Major and Minor stand high in the sky on April evenings. The 7 brightest stars of Ursa Major form one of the best known asterisms in the sky – the Plough. Unlike most stars in asterisms and constellations, five of the seven stars are related, moving at the same speed and in the same direction through space. As a result, in 100,000 years, the plough shape will be unrecognisable. In the pan handle, you can observe the double star of Alcor and Mizar. The two are actually about 30 light years apart in space and so are not physically related as a binary. Closer inspection of Mizar does however reveal a 4th magnitude companion, orbiting in a 10,000 year cycle. This companion was discovered in 1650 by Italian astronomer Giovanni Riccioli. Mizar was thus the first double star to be discovered by telescope. Another first for Mizar was that it was the first double star to be photographed, by Harvard’s George Bond in 1867. Furthermore, it was the first star to be discovered to be a spectroscopic binary by another Harvard astronomer, Edward Pickering. Subsequently, both the companion of Mizar and also Alcor, were found to be spectroscopic binaries. A remarkable stellar grouping indeed! Major is also home to several notable galaxies. The elusive M101 lies on the border of Ursa Major and Bootes. It is large but has a low surface brightness and it is that which makes it hard to see – just ask John Holmes! M109 lies close to Phecda, the bottom left of the plough blade whilst M 108 lies near Merak. M 81 and M82 are two related galaxies, at a distance of about 10 million light years from Earth, north and west of the blade. Just over the border from the handle of the plough lie the galaxies of M51 and M 106.
M51 is still visible this month, it lies in the constellation of Canes Venatici – the hunting dogs. Its popular name is the whirlpool galaxy. This is because it was the first galaxy in which the spiral structure was observed. In 1845, Lord Rosse turned his 72 inch reflector on this galaxy and drew a diagram that distinctly showed structure in the galaxy. It has an interesting feature of a small satellite galaxy at the end of one of the spiral arms, this is visible in moderate size telescopes. Follow the curve of the Plough’s handle and you will see a very bright star. This is Arcturus, the fourth brightest star in the sky. It is much bigger (about 27 times bigger) and gives out about 100 times more light. Despite this, it is more or less the same mass as the Sun. Arcturus is a red giant (orange in fact). A red giant is a star in its last stages. The nuclear fuel in its core runs out and so the next layer begins to ‘burn’. The effect of this is to cause the star to swell in size and lowers the surface temperature. What you are seeing is a picture of our Sun about 5,000 million years into the future. The Earth will be destroyed when this happens, it will actually end being swallowed by the Sun as it becomes a red giant.
I hope that you enjoy clear skies during spring.
The Summer months - June to August.
During the months of June, July and August, although the hours of darkness are fewer, at least we will not be as cold as earlier in the year! Almost overhead you will see the brilliant white star, Vega. It is a first magnitude star and is the main one in the constellation of Lyra, the lyre. Although it is a very small constellation, it is very obvious. Vega has the distinction of being the first star that was photographed. At one time, Vega was the pole star but, owing to precession of the polar axis of the Earth, will be the pole star again in about 11,500 years from now. Whilst looking at Lyra, spend some time observing beta Lyrae, a magnitude 3.4 star with a blue-white colour. Its brightness changes periodically, dropping to 4.3 every 13 days or so. Careful observers will note that half way through the cycle, the brightness fades to 3.8 and rises again to 3.4, before dropping to the 4.3 minimum. This star is in fact a binary star, the two components are so close together that they cannot be seen separately. Both stars are distorted into egg shapes by their mutual gravitational attraction. The variations in brightness are caused by eclipses. It is possible that there may be more bodies in this system. The variable nature was first recorded by John Goodricke in 1784, by simple naked eye observation. Since then, the period of light variation has been lengthening by about 2 minutes per year and it is this that suggests the presence of at least one further, unobserved member of the system. Scan some of the other main stars in Lyra, you will see that several of these are wide and easy to spot double stars. The most famous double of the constellation is probably epsilon Lyrae. This is a ‘double double’ star. Some keen eyed observers with clear skies claim to have seen the principal pair with the naked eye, however the majority of us will need to use some kind of optical aid. A pair of binoculars will split the pair. In order to see the two components as doubles themselves, you will need at least a 60 mm telescope and a high power. Under good conditions, up in Scotland, I have resolved this quadruple star using my 60 mm bird spotting telescope with a magnification of about X 40. There are a couple of Messier objects in Lyra, M56, a globular cluster and the better known M57, the Ring Nebula. You will probably be disappointed with your view of M57 because you will not see any of the beautiful colours that are shown in photographs, our eyes are just not sensitive enough to see colour under such low light conditions. The ring is easily noticeable in instruments of 60 mm and above, with a moderate to high magnification.
See also The Aries on line (Derby and District Astronomical Society magazine) at http://go.to/Ariesonline
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for rising and setting times.
I have not included any star charts here because there are plenty of astronomy books and places on the web that you can get them.