A little ramble through the winter sky - Auriga the Charioteer

 A striking constellation in the northern skies, Auriga lies above the horns of Taurus the Bull and forms the shape of a kite. Auriga is named after the son of Vulcan who invented the four horse chariot. Its brightest star Capella is the 6^th brightest star in the sky.

In 1899 astronomers discovered that Capella was not a single star but a double star. Like so many stars that appear single to the eye, Capella actually consists of two stars. But there's more going on with Capella as there is another component to this system, a pair of small red stars, meaning that where we see just one star there are actually 6!!

Capella whose name means the ‘Little She Goat’ has a magnitude of 0.1 and its a  G class giant slightly cooler than our Sun which is a G class dwarf and is 43 light years distant.

In brightness it is virtually equal to Vega in the constellation of Lyra the Lyre but it is of a very different colour, its yellowish tinge contrast sharply with the steely blue of Vega. Both are circumpolar from Britain, they can be seen all year round. They lie on opposite sides of the north pole star and at roughly the same distance from it. This mean that when Capella is high up Vega is low down and vice versa. From Britain Capella is overhead during winter evenings while in summer it is Vega that occupies that position. When at their lowest they are very low just above the horizon.

Slightly to the right and just below Capella is a little but quite distinct triangle of stars called the Haedi or the kids. They are referred to as the Kids because where the she goat goes the kids will always follow!! The top star in the triangle is epsilon, bottom left star is eta and the bottom right is zeta.

Epsilon is a F class supergiant white star its distance in not known with any great certainty but it could be about 2,000 light years away. It normally it shines at around magnitude 3.0 but every 27 years it fades to magnitude 3.8 where it remains for between 640–730 days – about two years. Epsilon is eclipsed by an unseen and unknown very large companion star.  The star’s last dimming was from 2009 to 2011.  The next should begin around 2038!

Zeta is another eclipsing binary where the companion star cannot be seen with the naked eye and varies between magnitude 3.7-4.1 over a period of 972 days.  Zeta is a K class giant star lying 790 light years away.

The third component eta which is 243 light years away. It is a B class star making it much hotter than the Sun, and has a brightness of magnitude 3.2.

Beta or Menkalinan which means ‘Shoulder of the Charioteer’, is the second brightest star in Auriga and is found to the left of Capella with a magnitude of 2.0 the same brightness as the North Star. It is an A class star with a surface temperature of around 9,000` C much hotter than our Sun. It lies at a distance of 82 light years.

A line drawn down from beta will reach the star theta or Mahasin with means the ‘Wrist of the Charioteer’. Theta has a magnitude of 2.6 and is an A class star 166 light years away. 

From eta which is the top star of the Haedi or kids a line drawn down and past zeta will come across iota or Al Kab which means the ‘Shoulder of the Rein holder’ at a distance of 490 light years we see iota as a star of magnitude 2.7. It is a K class giant being cooler than our Sun.

In 1930 for some reason the star that was originally classified as gamma Aurigae was transferred to the constellation of Taurus the Bull and re labelled at beta Tauri. It makes no sense at all as it is the bottom of the kite shape which used to form Auriga.

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A little ramble through 19th century astronomy - Red Stars in 1874

 Academy, Saturday 7^th February 1874 

Mr. Birmingham, of Tuam, has lately been examining the red stars comprised in the list formed by Schjellerup some years ago, and has already communicated some interesting results to the Astronomische Nachrichten and Monthly Notices. He finds curious changes of brightness in some stars, whilst others have disappeared altogether; and his results are confirmed by observations made at the Royal Observatory, Greenwich.

The connection between colour and variability in stars is very curious. It would appear that the red stars are in the condition of a fire dying out, and that the embers are sometimes raised to a white heat by some unknown causes only to die down again in an equally mysterious, manner. We are much in the dark as to the how and the when of many of these changes, but this much we do know, that solid bodies become brighter as they become hotter, and in doing so pass from red through yellow to bluish white. But what is the behaviour of gases under such conditions, is a problem of the immediate future, and it must be remembered that the changes in stars are probably due to gases; so that we are hardly yet in a position to speculate.

 The interesting question remains, whether we can justify a division of variable stars into two classes, the one of short period (a few days), showing the phenomena of rotation or of the interposition of a dark satellite; the other of periods ranging from a month to many years, in which the change has a physical origin. The stars of the latter class are generally red.

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The Astronomy Show on Drystone Radio

 Join me, Martin Lunn MBE every Monday evening from 7.00 pm-9.00 pm on the award-winning Astronomy Show on Drystone Radio, probably the only regular astronomy show on any radio station in the country. 

I will take my weekly look at the night sky and look at all the latest news in astronomy. There will be the astronomical anniversaries this week plus the latest news from the astronomical societies in the north of England.

The Astronomy Show every Monday evening only on Drystone Radio live online at www.drystoneradio.com DAB radio in Bradford and East Lancashire, or 102 and 103.5 FM and can also be heard later on the Drystone Radio Podcast.

 

Cooke Telescope Tales - telescope for Cambridge

 In 1867 William Henry Mandeville Ellis of St John’s College, Cambridge purchased a 4 inch Thomas Cooke & Sons telescope. I think that William Ellis was an architect. 

The telescope came with six astronomical, one comet, one eclipse and one terrestrial eyepieces. All the eyepieces had to be packed in a mahogany box.

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A little ramble through Hydrus the Lesser water Snake

 Hydrus the Lesser water snake is located near the south pole and therefore cannot be seen from Britain. It was one of twelve constellations created by Petrus Plancius from the observations of Pieter Dirkszoon Keyser and Frederick de Houtman on their explorations of what would become the Dutch East Indies and today is Indonesia. The constellation first appeared on a 35-cm (14 in) diameter celestial globe published in late 1597 (or early 1598) in Amsterdam by Plancius and Jodocus Hondius. The first depiction of this constellation in a celestial atlas was in Johann Bayer's Uranometria of 1603.

This is a smaller southern hemisphere version of the great water snake, Hydra. Hydrus is sandwiched between the two Magellanic clouds and almost bridges the gap between Eridanus and the south celestial pole. The Magellanic clouds are two nearby galaxies that can be seen with the naked eye from the southern hemisphere.  As Hydrus is so far south it was not known to astronomers in Europe or the Middle East and therefore has no old myths or legends attached to it.  Unfortunately, Hydrus is not a very bright constellation.

The brightest star is beta with a magnitude of magnitude 2.8 lying at a distance of only 25 light years. Beta is a G class star.

Alpha is the second brightest star with a magnitude of 2.9, its a F class star lying at a distance of 72 light years.

Located mostly in Dorado the Goldfish, the Large Magellanic Cloud also extends into Hydrus.

There are no bright deep sky objects in Hydrus

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A little ramble through Yorkshire Astronomy - The Devils Arrows at Boroughbridge

We stay with pre historic sites but move from features in the earth to standing stones. Keeping the North Yorkshire theme we travel to a site near Boroughbridge in the Harrogate district. We move forward in time to about 2,000 BCE to discover the Devils Arrows a line of three huge stones sometimes called ‘the three sisters’ there are suggestions that originally there were four stones.

The stones which are made from millstone grit which is  believed to have been quarried at Knaresborough which is around seven miles away and then dragged to their present positions. The stones each weigh around 25 tons so moving them using the technology available 4,000 years ago was no mean feat.

The stones that are still standing are aligned southeast to northwest and they form a line 374 metres long. The stones are between five to six metres high and are sunk into the ground to a depth of about 1.5 metres. The Devils Arrows today are actually less than 200 metres from the A1M motorway.

The name the Devils Arrows only dates back to the 1700s when according to legend the devil threw the stones at the next town which is Aldborough however much to the annoyance of the devil the stones fell short of their intended target and landed near Boroughbridge instead! I am not sure what a town in Yorkshire did to get the devil so annoyed?

As with many of these standing stones across the country there almost certainly was an astronomical connection. I am not sure if anybody is certain just what the connection might be. It certainly is not as clear cut as with the Thornborough Henges and the link with Orion. The fact that they align southeast to northwest suggests a possible link with the Sun and Moon. If as astro-archaeologists believe that there were originally four stones at this site it  could suggest a connection  with the position of the Sun and Moon during the four seasons during the course of the year. I am afraid that as with many of the stone circles and standing stones we will probably never know for certain.

The Devils Arrows like Thornborogh Henges are also listed as Scheduled Ancient Monuments.

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A little ramble through the winter sky - Canis Minor the Lesser Dog

 In mythology it is the smaller of the dogs that follows Orion the Hunter.

 It has only one bright star alpha or Procyon which means ‘Before the Dog’, this is because it rises before Sirius. Procyon is the 8^th brightest star in the sky with a magnitude of 0.3. It is close to the Earth being only 11.5 light years away. It is an F class star meaning its slightly hotter than our Sun.

Procyon forms a very prominent and large triangle with Sirius in Canis Major and Betelgeuse in Orion. This is often referred to as the Winter Triangle.

By a remarkable coincidence both of the dog stars are accompanied by white dwarfs. The pup orbiting Sirius was discovered by Alvan Clark in 1862 when he was testing a new telescope. The white dwarf orbiting Procyon was discovered in 1896 at the Lick observatory using the 36 inch refractor.

White dwarfs are the remains of a star that has used up all its hydrogen fuel and what remains is mostly helium, this makes them super dense objects with a tea spoon weighing many tons.

The only other notable star is beta or Gomeisa which means the ‘Bleary Eyed One’ It is of magnitude 2.9 and is 160 light years away, its a B class star which means it is hotter than the sun.

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