Astrognome 100 Great Stars No. 17 Beta Cassiopeia

 

Beta Cassiopeia

One of the two most famous star patterns that can be seen all year round from Britain are the Plough and the 5 stars that form the letter ‘W’ of the constellation of Cassiopeia. These are what astronomers refer to as circumpolar stars.

Beta Cassiopeia or to give its proper name Caph which means ‘Palm’ is the right hand star of the five stars of Cassiopeia that forms the letter ‘W’. It has a magnitude of 2.3 and it is a F2 giant star with a temperature of 7,000 degrees which is hotter than the Sun. Caph lies at a distance of 55 light years.

Caph is in the process of evolving, it was once a much hotter A class star and has now become an F class star. It will end its life as a M class red giant star, eventually all of its gas will be pushed away into space. It will go through a stage referred to as a planetary nebula so named because when astronomers saw these nebula for the first time several hundred years ago they looked like planets. When all the gas has gone all that will be left will be a white dwarf. Our Sun will go through the same evolutionary stages as Caph in the future.

Caph is rotating very quickly in fact it is rotating at 92% what astronomers refer to as its critical speed. This causes the star to appear not as a sphere but as an oblate spheroid.

As far as astronomers are aware Caph is a single star. In 1889 astronomers discovered a 14^th magnitude companion star but since its discovery the two stars have become further apart suggesting that that are not connected in any way astronomers refer to these as optical rather than real double stars.

The Astronomy Show Monday 31st August 7.00 - 9.00 pm

 The Astronomy Show Monday 31st August 7.00 pm

Join me Martin Lunn tonight on Drystone Radio for the Astronomy Show between 7.00 pm and 9.,00 pm. I will be looking at the night sky for the next 7 nights including details of the full moon which in September is the Harvest Moon but this one is a micro harvest moon!! There will also be the lastest astronomy news, the A-Z of Constellations, The Messier Marathon and the astronomical anniversaries for this week.

The Astronomy Show every Monday evening between 7.00 pm and 9.00 pm only on Drystone Radio 103.5 FM, the show can  also be heard live on line at www.drystoneradio.com and you can hear the show  for the t 30 days on the Drystone Radio podcast.

Astrognome 100 Great Stars No.16 Beta Canis Majoris

 

Beta Canis Majoris

Think of Canis Major and everyone thinks of Sirius the Dog Star but the second star in the constellation beta or Mirzam is an extremely interesting star. The name Mirzam or Mirzim means ‘The Announcer’ and like many stars we see in the Orion, Canis Major area of sky its a B1 giant star with a surface temperature of about 22,000 degrees centigrade. The star lies at a distance of 500 light years.

Mirzam is the prototype star of a small group of Beta Canis Majoris variable stars. They are all B class giant stars and although there light variations are very slight, they cannot be seen by just the by the eye alone. Special equipment has to be used. The star was first identified as varying in brightness in 1902 by Edwin Brant Frost at Yerkes Observatory in America.

When Mirzam was born it had about 10 times the mass of our Sun but it is now dying. It will shortly and by shortly I mean a few million years use up its supply of hydrogen gas and pass into a red supergiant star and then possibly ending its life in a massive supernova explosion.

Mirzam can be seen on the flag of Brazil as this country’s flag shows the night sky over Rio de Janeiro on the night of November 15^th 1889 when Brazil became independent from Portugal.

1855 Thomas Cooke Becomes Known in Europe

 

1855 Thomas Cooke becomes known in Europe

The last French Monarch of France Napoleon III who was nephew to the Emperor Napoleon was rebuilding Paris in 1855 and wanted he Exposition of that year to be the most impressive. The Paris Expositions were begun in 1789.

Although Napoleon wanted it to be the greatest art and industrial event ever staged it had already been eclipsed by the Great Exhibition at Crystal Palace in Britain in 1851. The exposition would run from June to November 1855.

Among the exhibitors was Thomas Cooke of York who took the brave step of exhibiting a variety of optical equipment including a 7.5 inch equatorial with a clock work drive.

Cooke was exhibitor No. 392 and was described as selling astronomical and nautical instruments. He was in the 8^th section ‘Arts connected with Science and Education’.

For Cooke it was a great success not only because he won a First Class Medal for his 7.5 inch telescope he also made some very good contacts. He met the astronomer Warren De La Rue and Lt Gen Edward Sabine, astronomer, geophysicist and explorer and Lt Col Strange from the East India Company, the latter two would be very important in ensuring that Cooke theodolites being used in the great survey of India.

He also introduced himself to the astronomers of Europe and in the following years there would be orders for telescopes and observatories from countries such as Austria, Belgium, Denmark, Hungary, Italy, Russia and Sweden.

Astrognome 100 Great Stars No. 15 Bellatrix

 

Bellatrix

The third brightest star in the constellation of Orion the Hunter. Bellatrix marks the top right hand star of the fours stars that form the giant rectangle shape of Orion. Bellatrix is a B2 blue giant star with a magnitude of 1.6. It has a surface temperature of 21,000 degrees centigrade and lies at a distance of 250 light years. As far as is known at the moment Bellatrix is a single star.

The name Bellatrix means ‘The Amazon Star’ and possible comes from the Arabic Al Najid meaning the conqueror. It is one of the stars that is often used for celestial navigation.

The name Bellatrix has attracted a new audience in recent years as the name is of a character from the Harry Potter stories. Bellatrix Lestrange is a cousin of Sirius Black. Sirius is of course the name of the brightest star in the sky. Which makes one wonder if J.K. Rowling had an interest in astronomy as quite a few characters have star names.

Astrognome 100 Great Stars No. 14 Barnard's Star

 

Barnard's Star

As the stars go about the galaxy on slightly different orbits, they change their positions relative to each other. As a result the constellations we see every night are only temporary patterns. For us of course such motions are very slow and nothing seems to change. The constellations will however over a period of hundreds of thousands of years will change shape.

Barnard’s Star is a small red dwarf star lying about 6 light years away, it cannot be seen with the naked eye as it has a magnitude of 9.5, but what makes it so special is that as far as astronomers are concerned, it races across the sky. Although it is called Barnard’s Star it is actually located in the constellation of Ophiuchus the Serpent Bearer. In about 3,000 years time it will leave Ophiuchus and move into the constellation of Hercules.

It was discovered by Edward Barnard in 1916 through a comparison of photographs taken between 1894 and 1916 and next to the alpha Centauri system its the closest star to us in the galaxy.

If you placed a 5 pence piece one half of a kilometre away the apparent size of the 5 pence would be the distance that Barnard’s Star moves across the sky. It might not seem much to most people but to astronomers that is moving very fast.

As far back as the 1960s it was believed that an object was orbiting the star because it appeared to be wobbling slightly. In 2018 an object with about 3 times the mass of the Earth was discovered and is referred to as Barnard’s Star b.

Red dwarf’s like Barnard’s Star are the most common type of star in our galaxy and make up around 70% of all stars. They use their supply of fuel much slower than that of our Sun, which means that while the Sun is around 5 billion years old the age Barnard’s Star is between 7 to 12 billion years.

The Cooke Factory in York and Women Workers

 The Haxby Road Works, York

By the mid 1930s the various Thomas Cooke buildings in York were old and small and dispersed over different sites. It was decided to concentrate on one new site. In 1937 managers looked for a new site and decided on a site on Haxby Road about 1.6 miles from the railway station.

The new site opened n 1939 and quickly production turned from civilian to military optical products. Demand was such that by 1943 seven floors of the nearby Rowntree's factory was taken over and the original workforce of 995 increased to a peak number of employees of 3,036 of these 1,184 were women on August 27th 1943.

After World War 2, the Haxby Road works returned to producing microscopes and surveying equipment. In 1963 the firm was taken over by Vickers Instruments and in 1989 it had moved into the production of electronic and software equipment and was sold to the American firm Bio Rad Measurements.

With the downturn in work the Haxby Road works was closed and demolished in 2008.

Astrognome 100 Great Stars No. 13 Arcturus

 Arcturus

The 4^th brightest star in the sky, it is the brightest star in the constellation of Bootes the Herdsman. The name Arcturus means the ‘Bear Keeper’ or ‘Guardian of the Bear’ and can be seen in the spring and early summer skies.

Arcturus is an orange K0 giant star with a magnitude of -0.1 and because it is so bright it is easy to see the orange colour. Arcturus can be found by following the curve of the handle of the Plough around and down, 

Arcturus can be found by following the curve of the handle of the Plough around and down. Every star has its own story but some are more curious than others. 

Arcturus  has an electrifying story with a twist involving the 1933 ‘Chicago Century of Progress Exposition’ in America. Chicago had hosted its first big fair in 1893. At the time it was believed that Arcturus was forty light years away, so when the second Exposition was planned for 1933, forty years after the first, it was decided to use the light from Arcturus focusing it onto a photocell to switch on the lights to the exhibition.

A photocell is an electronic device that produces electricity when light falls upon it. On May 27^th 1933 the light which left Arcturus in 1893, taking 40 years to reach earth, was channelled through a powerful telescope and directed on to a photocell to switch on the lights for the Exposition. Everything worked perfectly, except that today we know that Arcturus is only 37 light years away, not 40. The light had left the star not in 1893 but in 1896!

The constellation of Bootes has one other point of note in that it absorbed the now defunct constellation of the Quadrans Muralis the Mural Quadrant which was an instrument used to measure the positions of the stars.. However there is a meteor shower called the Quadrantids which can be seen early each January and this is the only example of a meteor shower being named after a now defunct constellation.

Astrognome 100 Great Stars No. 12 Antares

 

Antares

Antares is the brightest star in the constellation of the Scorpion, the constellation is well named because it looks for all the world liked the feared arachnid, its curved deadly tail swooping downwards. Antares marks the heart of the scorpion. Antares can be seen in late spring and early summer evenings from Britain. It will always be seen low in the sky. If you travel down to the Mediterranean area Antares and the rest of the scorpion will be much higher in the sky.

Antares or the ‘Rival of Mars’ due to its very red colour is an M1 supergiant star with a surface temperature of only around 3,500 degrees centigrade, cooler that the Sun at 5,800 degrees. It lies at a distance of about 550 light years. Antares is so big that if it was placed where the Sun is all the planets out to Uranus would actually be inside Antares.

In ancient Greece the constellation of the scorpion was much larger and covered the area which is now occupied by the constellation of Libra. Alpha and Beta Librae are known respectively as the ‘southern claw’ and the ‘northern claw’ confirming their link with the scorpion. It was the Romans who separated the stars and formed Libra.

Antares appears as a single star but it does have a companion star with a magnitude 5.5 however Antares is so bright that its light drowns out that from its companion. It cannot be seen with the naked eye or even a small telescope. A star with a magnitude of 5.5 could just be seen with the naked eye if you are observing from a very dark site. The companion star is a B2 class star with a surface temperature of around 18,000 degrees.

Antares is one of the largest stars that can be seen with the naked eye, however things will change in the next few tens of thousands of years when Antares will destroy itself in a supernova explosion. This Antares supernova could become as bright as the full moon and even be visible in the day time sky.

Astrognome 100 Great Stars No. 11 Altair

 

Altair

Altair is the brightest star in one of the most prominent constellations, Aquila the Eagle. It is one of the few groups which may be said to give at least a vague impression of the object it is meant to represent. If you have sufficient imagination one can imagine the picture of an eagle in flight. The name Altair comes from the Arabic ‘Flying Eagle’

Mythologically it represented an eagle which was sent from Olympus to collect the shepherd boy Ganymede, who was destined to become the cup bearer of the gods in succession to Hebe who had tripped and fell during a very solemn ceremony.

Altair makes up a large triangle with the stars Vega in Lyra and Deneb in Cygnus. These three stars form what astronomers refer to as the ‘Summer Triangle’.

Altair has a magnitude of 0.7, making it the 12^th brightest star in the sky, and has is a spectral type of A7 star which means that it is hotter than the Sun. Altair lies at a distance of 17 light years. It is the closest of the summer triangle stars.

Altair is interesting because it spins very quickly, at its the equator Altair is rotating with a speed of 286 km per second which is a significant way to a speed of 400 km per second which is the sped at which astronomers would expect the star to break apart. Altair spins so fast that it is not spherical in shape but flattened at the poles due to the high rotation speed.

Altair does have a companion star however there is no real connection between the two, this is an optical double not a binary system.

The Astronomy Show, Drystone Radio Monday 24th August from 7.00 pm

 Astronomy Show Monday 24th August 7.00 pm - 9.00 pm

Tonight on the Astronomy Show I will be looking at the night sky this week including looking more closely at the large but faint constellations of Hercules, Ophiuchus and Serpens  that are in the southern sky at the moment. 

There will be the astronomy news, the A-Z of Constellations and the Messier Marathon plus the astronomical anniversaries this week. Join me as we go for our regular weekly stroll along the northern spiral arm of the galaxy

The Astronomy Show every Monday evening between 7.00 pm and 9.00 pm only on Drystone Radio 103.5FM, the show can be heard live on www.drystoneradio.com or you can hear the show for the next 30 days on the Drystone Radio podcast.

Astrognome 100 Great stars No.10 Alphard

 

Alphard

Alphard is the brightest star in the constellation of Hydra the Water Snake, this constellation is the largest in the night sky. Alphard is sometimes called Cor Hydrae a term first used by Tycho Brahe (who observed the supernova of 1572) which means ‘The Hydra’s Heart’. Sadly it is always seen very low in the sky from Britain. Hydra is a spring constellation. Alphard is a K3 orange giant star with a temperature less than that of the Sun, with a magnitude of 2.0, which is the same brightness as the North Star. Alphard is 177 light years away. Alphard is usually known as the ‘Solitary One’ because there are no bright stars anywhere near it.

The star would be of little interest except that it is one of a class of stars of rather peculiar stars referred to as ‘Barium Stars’. Barium is a naturally occurring element and is number 56 on the periodic table. Alphard is a star that is the wrong kind of star to make barium, and when a star is not able to make it itself its get the barium from a companion star, usually this is a small white dwarf.

A white dwarf star is a star approaching the end of its life and although in size it will be very small the material that makes up the star is very compact and dense. Astronomers describe this material as degenerate material. A teaspoon of white dwarf material would weigh many tons in weight! During its life time material would pass between itself and companion star.

At the moment Alphard does not appear to have a companion star which is causing astronomers many questions. So if there is no white dwarf companion star, where did Alphard get its barium from?

Astrognome 100 Great Stars No. 9 Alperatz

 

Alpheratz

Despite Alpheratz being the brightest star in the constellation of Andromeda it is in fact also rather confusingly the brightest star in the square of Pegasus! In 1930 the International Astronomical Union (IAU) decided to standardise the boundaries of the constellations which could be represented on various star charts in a very chaotic way. The boundaries they drew up in 1930 are still used today. They decided for some unknown reason the star would be transferred away from Pegasus to Andromeda. It is an example of an illogical parcelling out of the stars.

In defence of the IAU astronomers for over 2,000 years had been allocating the star to both Andromeda and Pegasus. In fact after 1603 when Johan Bayer allocated a Greek letter to the brightest 24 stars of each constellations there are examples of the star being labelled on various star charts as either alpha Andromeda or delta Pegasus!

The square of Pegasus once identified is used as a signpost during autumn evenings in order to find other stars. Once identified it will be easily seen on subsequent nights. One problem that many people have when using Apts and star charts is to underestimate the size of the square of Pegasus. It covers a larger area of sky that many people think it does.

Alpheratz which is sometimes also known as Sirrah means the ‘Horses Navel’ which clearly has nothing at all to do with a princess. This is another piece of evidence suggestion that it really should have been left in Pegasus. Apheratz is a B9 class star with a temperature of 13,500 degrees centigrade and lies 97 light years away.

There is a faint companion start nearby that was discovered by William Herschel in July 1781, this star is not a true companion star to Alpheratz it is a line of sight effect with the star lying at some distance from Alpheratz.

A Nova and a Cooke Telescope in Italy

 

August 23^rd 1920

N.V Ginori in Florence, Italy, visual observations of the spectrum of Nova Cygni 1920 were made with a McClean star spectroscope mounted on a 9 inch Cooke equatorial refractor. The spectrum was continuous with dark H/3 just visible. Subsequent observations on August 25^th, 26^th, 27^th, 28^th, September 1^st, 3^rd, 8^th, and 11^th record the changes in intensity of the hydrogen and enhanced metallic lines.

Nova Cygnus was discovered by William Denning in Bristol on August 20^th 1920 at magnitude 3.5.

Astrognome 100 Great Stars No.8 Alpha Centaurus

 

Alpha Centaurus

The third brightest star in the sky, with a magnitude of -0.3 and one of the pointers towards the Southern Cross. The brightness of the star is due to its closeness to us. Alpha is only 4.3 light years away. It appears as a single star but in fact it is a triple star system. The third and faintest star in the system is also the closest to the Earth. This is Proxima Centauri which is only 4.2 light years away.

Alpha does not seem to have an official name although it is sometimes called Rigel Kentarus or Hadar, this name is sometimes also used for beta Centaurus. In my 100 great star list I have used the name Agena for beta to hopefully avoid any confusion.

The distance to alpha was determined in 1839 by Thomas Henderson while working at the Cape Observatory in South Africa. Alpha is not visible from Britain.

Henderson used what is called the principle of the parallax to work out how far away the star is. Let me give you an example. Close one eye and hold up a finger at arm’s length and line it up with an object in the background, such as a tree. Now without moving your finger or your head use the other eye. Your finger will no longer lined up withy the tree, because you are observing it from a slightly different location, your two eyes are not in the same place. If you know the length of the baseline (i.e. the distance between your eyes) and you measure the angular shift of your finger, which defines the parallax, you can solve the triangle by means of simple mathematics. Then it is possible to find the real distance between your finger and your face. I am talking of course about very simple trigonometry which everyone would study while at school.

To solve the parallax of a star Thomas Henderson had to use the baseline of the orbit of the Earth which is 186,000 miles or 300,000 km. He made measurements over a six monthly interval. He found a slight but measurable parallax shift and this gave him a distance of 4 light years. Today astronomers can measure the parallax of stars to a distance of around 300 light years.

Proxima the closest star to us and the third and faintest component of the system was discovered by R T A Innes from South Africa in 1915.

The three stars that form alpha Centauri are alpha A which is a G2 class star with alpha B being a K1 class star. Alpha C or proxima is a small red dwarf star which appears to have at least two planets orbiting it.

AStrognome 100 Great Stars No.7 Algol

 

Algol

The most important star in the constellation of Perseus is Algol or to give its Greek letter designation beta. Perseus is of course our hero in the Cassiopeia/Andromeda legend. In the sky Perseus is depicted holding the head of the medusa after just having killed the creature rushing to rescue Andromeda from the sea monster. Algol marks the eye of the Medusa.

Algol, looks ordinary enough looking like a star of around magnitude 2.5 but every 2 days and 13 hours it fades in brightness and until it is below magnitude 3.0. It remains at this state for about 20 minutes after which it starts to brighten once more taking 3.5 hours to return to its former brightness . Nothing further happens for another 2 days and 13 hours when the slow fade in brightness begins again.

Algol behaves in fact like a rather odd sort of variable star. It was first noticed by the Italian astronomer Montanari in 1669, but it was not until over a century later that astronomers worked out what was happening to Algol.

The man responsible was John Goodricke who was based in York, he was deaf and unable to speak but there was absolutely nothing wrong with his brain. In fact between 1781 and 1786 he worked in York with another astronomer Edward Piggot, between them they laid the foundations for the study of variable stars. I christened them the ‘Fathers of Variable Star Astronomy’ a term that I think appears to have stuck.

Goodricke realised that Algol was not one but two stars and that they were eclipsing each other causing the light changes. We know today the Goodricke’s observations were very close to modern estimates, and of course he did not have any of the modern technology to help him. It would take astronomers over 100 years to prove that Goodricke was correct with his theories. In fact today when astronomers look at other stars for very faint changes in light to identity planets orbiting the stars they are using the same idea as suggested by Goodricke. In fact we might say that Goodricke and Piggot were over 200 years ahead of their time!!

Sadly John Goodricke died before his 22^nd birthday so we cannot even begin to imagine what other contributions he may have made to astronomy had he lived longer.

We now know that the stars that make up Algol are a B8 class hot star with a temperature of around 13,000’Centigrade and an orange K0 class star with a much lower temperature of about temperature of around about 4,500 degrees.

Today astronomers have discovered many stars similar to Algol. These stars are referred to as Algol type variable stars.

There is one mystery that has never been properly cleared up. We know that most star names are Arabic and were named over 1,200 years ago. The Algol means the ‘Winking Demon’, does this suggest that the Arab astronomers also notice the changes in brightness.

Astrognome 100 Great Star No. 6 Aldebaran

 

Aldebaran

Aldebaran is the lead star of Taurus the Bull one of the most important of the zodiacal constellations. The constellations of the zodiac are where will locate the planets in our solar system. Taurus in mythology is said to represent Zeus the king of the gods who changed himself into a bull in order to carry off Europa daughter of the king of Crete. (It is quite clear that the morals of some of the ancient gods were to put it mildly questionable!!)

Aldebaran which means the ‘The Follower’ marks of the eye of the bull. If you are trying to find Aldebaran and you know how to locate the three stars that form Orion’s Belt, draw a line through the three stars up and to the right and then you will reach Aldebaran.

Aldebaran is a red giant star with a cooler surface temperature than the Sun at around 3,800 degrees centigrade compared to that of the Sun which is 5,800 degrees. It lies about 65 light years away. Aldebaran is surrounded by a ‘V’ shaped cluster of stars called the Hyades.

In mythology the Hyades were the daughters of Atlas and Aethra and hence the half sisters of the Pleiades. The Pleiades or Seven Sisters is a famous star cluster that can also be seen in Taurus. If you remember finding Aldebaran by drawing a line from Orion’s Belt upwards and to the right by continuing this line you will reach the Seven Sisters which you can easily see with your eyes without using binoculars or telescopes.

I have said that Aldebaran appears to be surrounded by the Hyades but this is merely an optical illusion, we know Aldebaran is about 65 light years away, however the Hyades group which contains over 100 stars is about 150 light years away.

I have mentioned that Taurus is in the zodiac and the planets are found in this region of the sky. The same applies to the Moon and there will be occasions when the Moon can pass in front of Aldebaran. In fact Aldebaran is the brightest star that the Moon can pass in front of. This astronomical event is called an occultation. The last time this occurred was on July 6^th 2018, the next occasion will not be until 2033.

The Pioneer space probe that was launched in 1972 will reach the vicinity of Aldebaran in about 2 million years time.

Cookes to Australia for Transit of Venus

 

Cooke Telescopes for Transit of Venus

By August 20th 1874 two Cooke telescopes have just been completed for the Government of South Australia for the upcoming Transit of Venus in December 1874.

One telescope is an 8 inch telescope that will be used by the government astronomer at Adelaide. The telescope is based on the example exhibited by Cooke and Sons at the International Exhibition in London in 1871.

The instrument has been viewed by astronomers from the Royal Greenwich Observatory in London who were very much impressed by what they saw.

A second telescope is also being sent out to Australia, its destination will be Melbourne. It is a smaller 4 inch telescope.

Astrognome 100 Great Stars No.5 Albireo

 

Albireo

Albireo or beta Cygnus is often regarded as one of the most beautiful double stars in the sky for small telescopes. Interestingly it is the fifth brightest star in Cygnus, the Greek letter beta would normally mean that it should be the second brightest star in a constellation.

Albireo is around 415 light years away and to see the companion star you will need at least a small telescope. Albireo is an ordinary orange giant star cooler than the Sun with the companion being a blue/ white star and although it is a dwarf it is still much hotter than the Sun with a temperature of about 13,000 degrees centigrade compared to 5,800 degrees for the Sun. Everyone who observes Albireo agree that the colour contrasts are simply fantastic.

Observers in the 19^th century often described the pair of stars as having the colours of golden yellow and the companion appearing sapphire. Other descriptions refer to them as appearing golden and azure.

It is unclear if the two stars are a real double star or merely a line of sight effect. Observations from both the Hipparchus and Gaia satellites have been unable to solve the mystery.

The name Albireo seems to have come into use around 1515 with a mistranslation from Ptolemy’s catalogue of around 150 AD. The Arabic astronomers had always referred to the star as Al Minhar al Dajajah or Hen’s Beak which is still used as the translation of Albireo.

Serious Sccident at Mr Cook's Shop in York

 

Serious Accident at Mr Cook’s Shop in York August 18^th 1837

At about 4.00 pm Mr Noton, a plumber of little Stonegarte in this city and his son were preceding up Stonegate in their pony carriage when their horse took fright. The pony and carriage set off at full speed, Mr Noton was thrown clear into a shop and was seriously injured. Mr Noton jnr also fell out but held onto the reigns, the carriage righted itself and the pony took off again with young Mr Noton being dragged along the ground. The pony and carriage then crashed into several crates of crockery ware and then demolished several squares of glass in the window of the shop of Mr Cook the Optician.

Mr Cook was unhurt and apart from the damage to the windows there was no serious damage done to the scientific instrument in his shop. The history of telescope making in York could have taken a very different course has the damage caused by the runaway horse proved to be more serious to Cook’s shop.

The pony and carriage finally came to rest when it got stuck at a lamp post, the carriage was badly damaged the pony was seemed OK. It is believed that the injuries that were suffered by Mr Noton senior would not prove to be fatal.

The Vulcan Star seen from Australia

 The Vulcan Star

Dr. William Evan MacFarlane was born on the island of New Caledonia which is located in the Pacific Ocean between Australia and Fiji. He was born in 1866 the son of a missionary.

He was educated in England and entered the medical profession and after first practising in Edinburgh moved to China. However due to civil unrest and then the war with Japan MacFarlane returned to England. He then served with the British army during the Boer war as a medical officer.

In 1903 he obtained the appointment as Government Medical Officer to a large mining district in North Queensland, Australia where he remained to his death. Outside his medical career he was very keen on astronomy.

He took charge of the Walsh Hospital at Irvinebank, North Queensland in 1906 where he also installed on Hospital Hill an observatory which housed a Thomas Cooke of York 7in telescope.

He observed Nova Aquila 1918 which he named ‘The Vulcan Star’, which the nova is still known locally as. This was probably named after The Vulcan Mine, a tin mine adjacent to his home and observatory.

He died on August 18^th 1919 from influenza, he never married. It was reported in the Cairns Post that the funeral of William MacFarlane was the largest and most impressive ever seen in Irvinbank with 200 mourners.

Astrognome 100 Great Stars No. 4 Agena

 Agena

Beta Centaurus sometimes known as Agena which is a relatively modern name from the 17^th century, with no indication as to a meaning. The star is sometimes known as Hadar, however rather confusingly this name is also sometimes used to refer to alpha Centaurus as well as beta. So I will stick with Agena for now.

Agena is the second of the pointers to the Southern Cross the other being alpha Centaurus and although alpha appears brighter in the sky that is simply down to distances because alpha is just over 4 light years away while Agena is around 390 light years away.

Like many stars Agena is not a single star it is a triple star system, Agena the main star is a blue giant star much hotter than the Sun with a surface temperature of around 25,000 degrees centigrade. If Agena was as close as alpha it would be so bright that it would cast a shadow.

Agena with alpha Centaurus were known to the bushmen of South Africa as two men who were once lions, while the Australian Aborigines were regarded as two brothers.

Agena is not visible from Britain but from the southern hemisphere it is circumpolar from New Zealand which means from there it can be seen all year round.

Astrognome 100 Great Stars No. 3 Adhara

 

Adhara

Winter in the northern hemisphere and looking to the south, the sky is dominated by Orion the Hunter and Sirius the Great Dog Star in Canis Major, the brightest star in the sky. Although Sirius is the object everyone looks at Adhara or epsilon Canis Major is also worth seeking out, its name means ‘the Virgins’ which of course has nothing to do with the mythological dog in the sky. Adhara is in fact part of an old Arabic constellation.

Unfortunately as seen from Britain Adhara is very low in the sky meaning that any haze makes seeing the star difficult. It lies at a distance of around 430 light years away and can be seen as a star with a magnitude of + 1.5 it is in fact the brightest of the second magnitude stars. First magnitude stars are brighter than magnitude +1.5. Around 5 million years ago it would have been the brightest star in the sky with a magnitude of -3.9, Sirius by comparison has a magnitude of -1.4. No other star will appear as bright as Adhara in the sky for at least another 5 million years. It only appears fainter than Sirius because it is very much further away. Sirius is only about 8 light years away.

Adhara does have a companion star which was discovered at the Cape Observatory in South Africa in 1850 but can only be seen with fairly large telescopes because the light from Adhara is so bright that it drowns the fainter light from its companion which could be seen using binoculars if it was not so close to Adhara.

It is much hotter than the Sun with a temperature of around about 22,000 degrees centigrade compared to the Sun’s 5,800 degrees and if your eyes could see in ultra violet light then Adhara would be the brightest object you would see in the sky.

When people talk about the spectrum they are usually referring the optical spectrum the colours of the rainbow. Scientists study the electromagnetic spectrum which covers not only visible light, but also infra red, ultra violet and radio.

In winter while looking for Sirius and Canis Major and you have a really clear dark night try looking for Adhara low in the sky in the south.

Astrognome 100 Great Stars No. 2 Achernar

 

Achernar

Achernar is the brightest star in the long winding constellation of Eridanus the River which begins close to Orion and ends in the far south. Achernar is so far south that it cannot be seen from Britain.

Achernar lies around 140 light years away and is much hotter than the Sun, and is the 9^th brightest star in the sky. Its name is derived from Arabic and is referred to as the ‘Star at the end of the River’.

We normally think of a star as a sphere of hot spinning gas but Achernar spins so quickly that it is pushed out of shape so it appears more like an oblate spheroid. It is quite possible the least known spherical star in our galaxy.  Achernar is around 10 times the diameter bigger than our Sun.

There is something of a mystery here because the star Acamar which is also  in Eridanus and which lies north of Achernar was referred to as the Star at the end of the river by the Greeks. Ptolemy who is often regarded as one of the last Greek astronomers does not mention it suggesting that he never saw Achernar. He could have seen it from Alexandria which further suggests that Ptolemy’s star charts were based on those produced by Hipparchos who live on the Island of Rhodes further north from where Achernar was not visible.

Achernar lies in a very barren part of the sky which makes identifying it very easy and it does definetly mark the end of the river. It also does have the distinction of being the brightest close star to the south pole which is marked by the very faint star sigma octantis.

Astrognome 100 Great Stars No.1 Acrux

 Star 1

Acrux

Just as Ursa Major is the most famous constellation in the northern hemisphere then Crux or the Southern Cross is the most famous in the southern hemisphere. Yet surprisingly it is also the smallest of the 88 constellations in the night sky.

Acrux is the brightest star in the constellation of Crux, however the southern cross was actually part of the constellation of Centaurus. It is sometimes cited that it was in 1679 that the French astronomer Augustin Royer created Crux, however both the English astronomer Emery Mollineux in 1592 and the Dutch Flemish astronomer Petrus Plancius in 1598 had recorded Crux being a separate constellation.

Acrux is the 13^th brightest star in the sky but there is more to the star than meets the eye because there is not one but two stars here. They are both very hot blue / white stars with surface temperatures of around 23,000 degrees centigrade to 25,000 degrees centigrade. It is estimated that they take around 1,500 years to orbit each other. And there is more because Acrux 1 is itself also a double star and Acrux can be referred to as a triple star system.

Best of all Acrux leads us to one of the most glorious regions of our galaxy the Milky Way. To the east of the cross lies the ‘Coalsack’ a dense cloud of star forming interstellar gas and dust that blocks the background starlight. The coalsack is so dark and prominent that the Incas in South America made a constellation of it calling it the ‘Yutu’ a partridge like southern bird.

To the north east of Acrux is one of the finest star clusters the ‘Jewel Box’ it is so bright that it was named after the 10^th letter of the Greek alphabet kappa Crucis.

Acrux and the constellation of Crux is one of the few that is honoured in music with the tango by Richard Rogers “Beneath the Southern Cross” from the documentary ‘Victory at Sea’.

Acrux also appears on the national flags of Australia, New Zealand, Samoa and Papua New Guinea.

Once seen Acrux and its surroundings can never be forgotten.

Astrognome 100 Great Stars, Star 0 the Sun

 The 100 great stars will be presented alphabetically but I thought that I would make one exception and put the Sun as the first star.

The Sun

Our local star is the Sun, without it there would be no life on the Earth, so it is very important to us. The Sun is around 93 million miles away and is large enough to place around 1.3 million Earths inside it.

The Sun is around about 5 billion years old and formed out of a giant cloud of dust and gas, it was from that same cloud that the Earth and the other planets formed about 4.5 billion years ago. The Sun is made up of about 92% hydrogen, 8% helium and tiny amounts of everything else.

Astronomers classify the Sun as a yellow dwarf star, it is a fairly ordinary star, there are many stars smaller and some much larger than the Sun. The Sun has a surface temperature of about 5,800 degrees Centigrade, in the centre of the Sun this increases to an incredible 14 million degrees Centigrade.

The Sun is a stable star it is not what astronomers refer to as a variable star, that is a star that changes in brightness over a period of time. This is good for us as it has enabled life to evolve on Earth.

However it would be wrong to say that nothing happens on the Sun. Solar Flares come from features called sunspots which are cooler areas on the surface of the Sun. This causes them to appear darker compared to the disk of the Sun. These are areas of intense magnetic activity. If a flare from the Sun crashes into the Earth’s protective magnetic shield then we will see the Aurora Borealis or the Northern Lights. In the southern hemisphere this is the Aurora Australis or southern lights. The aurora can be seen at other times because there is a flow of particles from the Sun called the solar wind and when this become strong it can also cause aurora.

The sunspots have an 11 year cycle when large numbers are seen, however rather curiously when there are very few sunspots the Earth appears to become cooler. There was a period during the late middle ages when the Earth experienced a cooling down and is referred to as the Little Ice Age this also coincided with a lack of sunspots. The same thing happened in the early 19^th century when a young man called Charles Dickens was growing up and he used his experiences as a child in the very cold weather as a back drop to some of his stories. The latest sunspot cycle has very few sunspots and experts cannot agree what this means for the future.

Astronomers are only really beginning to understand what makes the Sun tick and with this in mind astronomers have recently been sending space craft to study the Sun in more detail to try to understand how it works.

Jupiter seen from Manchester in 1869

 

The Planet Jupiter seen in 1869 from Manchester

Mr H. Ormesher of Manchester witnessed the partial transit of the 3^rd satellite on the night of August 14^th 1869. The satellite was visible as a bright spot 15 minutes after first contact.

On the night of the 24^th August 1869 the 2^nd satellite was observed during its ingress.

Mr Ormesher says “After first contact the satellite appeared to linger for some time” A somewhat analogous phenomenon is noticed on page 141 of Webb’s Celestial Objects,

Astrognome 100 Great Stars Introduction

 Astrognome 100 Great Stars Introduction

Following on from the Astrognome A-Z of constellations I intend to present the Astrognome 100 Great Stars. Many people I am sure could suggest an alternative 100 stars but hey this is my selection. I have tried to stick with the brighter and better known stars.

I thought it would be useful to present a very short introduction to the stars.

Look into the night sky there appear to be millions of stars, however on any clear night from anywhere really dark site away from city lights it is possible to see around 3,000 stars without a pair of binoculars or telescopes. The stars appear to be randomly spread across the sky.

The stars are actually grouped into patterns or constellations these tell stories from ancient Greece. However although the star stories are Greek most of the star names we use today are Arabic.

There are 88 constellations in the sky, 48 date back to the times of ancient Greece while the other 40 constellations were added in more modern times, by modern I mean the 15^th and 16^th centuries. Most of the modern ones are in the southern hemisphere and were added when European explorers went there, while some were added in the northern hemisphere to fill gaps between the classical constellations.

If you look at a star map or an app on your phone or use a tablet you will see the stars have strange looking symbols besides them. These are letters from the Greek alphabet. In 1603 Johann Bayer allocated the 24 brightest stars of each constellation a Greek letter. In theory the brightest star is alpha followed by beta, gamma etc until omega. However we will discover that this system does not always work.

The brightness of a star is measure by its magnitude with the brightest stars having minus numbers and the larger the magnitude number the fainter the stars. Assuming you are in a very dark site and have good eyesight we can see stars to magnitude 6 with our eyes without using binoculars and telescopes. You will notice that some stars are much brighter than others this can be because they are fairly close to us, or because they are genuinely very bright stars. However appearances can be deceptive because some stars only appear faint because they are a very long way away.

Astronomers use the speed of light to measure the distance to the stars, although we use the mile to measure distances on Earth it is too small a unit in space. Astronomers use the speed of light to measure the distances to the stars. Light travels at a speed of 186,000 miles per second or 300,000 km per second. In one year a particle of light will travel around 6 million million miles that is a 6 followed by 12 zeroes. Stars can be 10s, 100s 1,000s or even millions of light years away!

When you look at the stars it is possible to see that they are different colours and rather surprisingly blue stars are hotter than red stars. I know we say that things are red hot, meaning that's very hot, but if you look at a flame around the edge it will appear reddish while in the middle it is blue. This is the hottest part of the flame. And although stars don’t burn like fire they produce their energy through atomic reactions the colour principle is the same. Therefore when you look at a blue star it is much hotter than a red star. Astronomers divide the stars into different classes by using a series of letters with O class stars the hottest and M class stars the coolest.

Stars do come in different sizes giants and dwarfs and although our the Sun is very big by our standards, it is about 900,000 miles across some stars are much bigger.

That’s it for this very brief introduction to the stars, I hope you found this short section helpful.