Saturday 29 August 2015

Astrognome Scrapbook Novae Cygni 1975

Nova Cygni 1975

The constellation of Cygnus the Swan dominates the sky in the northern hemisphere during summer months, Cygnus is sometimes known as the Northern Cross. Deneb its brightest star is part of the summer triangle of bright stars overhead during the summer months. However on the night of August 29th 1975 the shape of Cygnus changed for a short period of time when a Nova appeared.

The term Nova comes from the Latin for New, a few hundred years ago when astronomers saw what we call Nova they thought they were new stars being created. Hence the name Nova.

A nova is a binary system where two stars orbit each other. Typically one will be a white dwarf, and the other a red giant, the white dwarf has a strong gravitational field and pulls gas from the larger though less massive red giant. When some of this less dense and cooler gas falls onto the hot surface of the white dwarf it is thrown off into space, the star will become brighter for a period of time before returning its normally brightness. This process can happen more than once.

Many independent discoveries were made of the Nova at magnitude 3, the following day it rose to magnitude 2, which is as bright as the North Star. This makes it very easy to see. It quickly faded, over the next three days it faded to magnitude 5 towards the edge of naked eye visibility. During the next few weeks it faded to magnitude 9 making it a difficult object to find in binoculars.

At the time of its discovery it was simply referred to as Nova Cygni 1975, today it has the designation nova V1500 Cyg, which means it was the 1500 variable star to have been discovered in the constellation of Cygnus.

It was the brightest novae since 1942 and there have been no novae as bright as this seen in our galaxy since Nova Cgyni 1975. Today a powerful telescope is needed to find.

Where have all the bright Novae gone? During the 20th century  6 novae were seen between 1900-1950 which were at least as bright as the North Star, from 1950-1999 there was only 1. In the 21st century so far there have been none.

I wonder when the next bright Nova will be seen, the next time you go out to observe take a few minutes to look at the bright stars that form the constellations to make sure there are no ‘new’ stars there before you go onto hunting those very faint objectives that attract all the attention today.

Friday 28 August 2015

Astrognome Astronomy The Free Transfer Star

Rho Aquila The Free Transfer Star

During the summer much time can be spent looking at the summer triangle of bright stars, Vega in the constellation of Lyra, Altair in Aquila and Deneb in Cygnus.
I would like to draw your attention to rho Aquila a 4.9 magnitude star in the constellation of Aquila the Eagle which is just visible to the naked eye on a clear dark night, although binoculars will show it easily.

It’s an unremarkable star,  but it has a remarkable claim. In 1992 it moved from Aquila to the neighbouring constellation of Delphinus the Dolphin.

Rho Aquila is about 160 light years away and it is moving very slowly across the sky at a rate of 0.06 of an arc second per year. Since the star was catalogued as rho in 1603 by Bayer it has moved about 24 arc seconds across the sky and now is in Delphinus.
Of course the constellation boundaries are quite arbitrary, it’s not really significant. However if you want a good pub quiz question, in which constellation will you find the star Rho Aquila?

The next naked eye star due to get a free transfer to another constellation is Gamma Caelum in the constellation of the Sculptor’s Tool which has a magnitude of 4.6 and will transfer to the constellation of Columba the Dove in around the year 2400!

Wednesday 26 August 2015

Astrognome Astronomy R Scuti

R Scuti

Edward Pigott, together with John Goodricke became  one of the fathers’ of variable star astronomy when they worked together in York 1781-86. Following the death of Goodricke in 1786 Pigott moved to the city of Bath where he continued to observe the sky. In 1795 he discovered another variable star which today is known as R Scuti and the summertime is a good time to look for it.

Close to Messier 11, the wild duck cluster which is in the small constellation of Scutum the Shield lies a very interesting variable star, R Scuti. At its brightest it can rise to magnitude 4.4 and be visible to the naked eye, but can drop to magnitude 8.6 when binoculars are needed to find it.

It belongs to the rare type of RV Tauri type variables which are yellow supergiant stars of immense size but of low mass and density. These stars pulsate and R Scuti varies and becomes bright over a period of about every 140 days.

It’s always good fun to replicate those early observations Goodricke and Pigott and by doing so it can help to learn your way around the sky using the naked eye or just simple  binoculars.

Tuesday 25 August 2015

Astrognome Scrapbook August 25th 1835 The Great moon Hoax

The Great Moon Hoax

If it is clear tonight you will see the familiar sight of the Moon in the sky, but on this day 180 years ago there were some amazing stories about the Moon appearing in American newspapers.

On August 25th 1835, the first in a series of six articles announcing the supposed discovery of life on the moon appeared in the New York Sun newspaper.
Known collectively as “The Great Moon Hoax,” the articles were supposedly reprinted from the Edinburgh Journal of Science by Dr Andrew Grant.  It was said that Sir John Herschel, a famous British astronomer of the day and son of Sir William Herschel who had discovered the planet Uranus in 1781 had made some amazing discoveries about the Moon.

Herschel travelled to Cape Town, South Africa, in January 1834 to set up an observatory with a powerful new telescope and map the southern skies. His father had catalogued the northern hemisphere and he wanted to complete the full sky survey by studying the southern sky.

The Sun said that Herschel had found evidence of life forms on the moon, including such fantastic animals as unicorns, two-legged beavers and furry, winged humanoids resembling bats. The articles also offered vivid description of the moon’s geography, complete with massive craters, enormous amethyst crystals, rushing rivers and lush vegetation.

These hoaxes were made when communications were very slow and information between continents only moved at the speed of sailing ships as they travelled around the world. It would take weeks for a ship to travel from South Africa to North America. Herschel of course was completely unaware of these stories. Herschel returned to England in 1838.

The New York Sun, founded in 1833 was one of the new “penny press” papers that appealed to a wider audience with a cheaper price.  From the day the first moon hoax article was released, sales of the paper shot up considerably. It was exciting stuff, and readers lapped it up. The only problem was that none of it was true. The Edinburgh Journal of Science had stopped publication years earlier, and Grant was a fictional character. The articles were most likely written by Richard Adams Locke, a Sun reporter educated at Cambridge University.

Readers were completely taken in by the story, and believed the hoax. The craze over Herschel’s supposed discoveries even fooled a committee of Yale University scientists, who travelled to New York in search of the Edinburgh Journal articles. After Sun employees sent them back and forth between the printing and editorial offices, hoping to discourage them, the scientists returned to New Haven without realizing they had been tricked.

On September 16, 1835, the Sun admitted the articles had been a hoax. Readers were generally amused by the whole thing, and sales of the paper didn’t suffer.
When Herschel heard of the hoax he laughed and said he "feared the actual results of his telescopic observations at the Cape would be very humble, in popular estimation, at least, in comparison with those ascribed to him in the American account."

The Sun continued operation until 1950, when it merged with the New York World-Telegram. The merger folded in 1967. A new New York Sun newspaper was founded in 2002, but it has no relation to the original.

Monday 24 August 2015

Astrognome Astronomy, P Cygni

P Cygnus, a very unstable star

Close to Gamma Cygni the central star of the northern cross lies a star which looks quite unremarkable, P Cygni. It is in fact a most fascinating star which varies in brightness. It was first observed in 1600 when it was of the 3rd magnitude, because it had not been noticed before it was classes as a nova which is Latin for new star.

It then slowly faded and by 1620 was no longer visible to the naked eye.  In 1655 it was seen again and reached magnitude 3.5, however by 1662 it had faded from naked eye view again.

Since about 1715 it has varied between magnitude 4.6 and 5.2. P Cygni appears to be a very massive and unstable star. It is around 6,000 light years away and is about one million times as luminous as the Sun.

John Goodricke and Edward Pigott the fathers of variable star astronomy would have observed this star while working together in York between 1781-1786.

Cygnus is a constellation seen during the summer months with its brightest star Deneb being a member of the summer triangle. If you have binoculars it is worthwhile looking for P Cygni because although it has not changed in brightness very much over the last 300 years it might suddenly flare up and then disappear in a supernova explosion.

 Although of course that might not happen for the next million years!

Friday 21 August 2015

Astrognome Astronomy Albireo The Coloured Double Star


Albireo or beta Cygni, is the faintest of the stars of the Northern Cross, part of the constellation of Cygnus the Swan. Deneb the brightest star is part of the 'Summer Triangle ' of stars. At the other end of the northern cross is Albireo is a target for anyone with a small telescope or binoculars. The contrast in colours with are wonderful.

To the naked eye Albireo  appears as a single star, however there are two stars there. The brighter star which is of the 3rd magnitude is golden yellow while the fainter which is of the 5th magnitude is a vivid blue.

The two components are a true double star but they are a long way apart around 500,000 million miles with Albireo being about 400 light years away.

Have a look at Albireo the colour contrasts mean that different people see different colours. What colours do you see? Albireo is probably the most beautiful double star in the sky.

Monday 17 August 2015

Astrognome Scrapbook August 17th 1958

Lunar Probe Able 1

The first attempt by America to send a probe to the Moon, Able 1 ended in failure. After just 77 seconds when Able 1 was 12 miles high the lower stage of the rocket exploded destroying the probe. It would not be until Ranger 7 in 1964 that the Americans successfully launched a Moon mission.

In those days the Americans were well behind the Russian who had already sent probes to the Moon by 1959.

All these early missions were unmanned.

Friday 14 August 2015

Astrognome Scrapbook August 14th 733 Solar Eclipse

Solar Eclipse 733 AD

The weather today is pretty miserable with lots of rain however on this day in 733 the weather must have been much better because an eclipse of the Sun was seen from England.

The Anglo Saxon chronicle tells us that on this day King Ethelbald of Mercia, which covers the modern day area of the midlands in England captured the manor at Somerton which is in south Somerset and all the disc of the Sun was like a black shield.

The eclipse was also seen in Europe, the Chronik der Seuchen tells us that "one year after the Arabs had been pushed back across the Pyrenees after the Battle of Tours the Sun was so diminished as to excite universal terror"

The eclipse was an annular eclipse and at maximum only 2.5% of the Sun was showing. An annular eclipse occurs when although the Moon is directly in front of the Sun it is a little bit further away from the Earth meaning it appears slightly smaller and therefore cannot block out all of the Sun. The tern Annular comes from the Latin Annulus meaning 'Ring'.

Thursday 13 August 2015

Astrognome Scrapbook August 13th 1596 Omicron Ceti 'Mira'

Mira the Wonderful Star

I often refer to John Goodricke and Edward Pigott of York as being the ‘Fathers of Variable Star Astronomy’ which they are, but the first variable star to be discovered was found nearly 200 years before them.

The Dutch astronomer David Fabricius saw a star in the constellation of Cetus the Whale he recorded it of being of the third magnitude, which means it is quite easy to be seen with the naked eye, this was of course was in the days before the telescope had been invented. A few weeks later he could not find it!

In 1603 the German astronomer Johann Bayer who was producing his Uranometria star atlas recorded it slightly fainter at the fourth magnitude and gave it the Greek Omicron. Bayer allotted the brightest star in each constellation the Greek letter alpha followed by beta the next brightest star  and so on until omega. We still use this system today.

It then vanished again, it was not until 1638 that the Dutch astronomer Johann Holwarda recognised that the star omicron ceti became bright every 331 or so days. Sometimes it can become as bright as  Polaris the North Star while at its faintest it drops sown to the ninth magnitude and is a test to find it in binoculars.

Omicron Ceti is the prototype star for a large class of these so called long period variable stars. These are large red giant stars approaching the end of their lives.

This was the first time astronomers had seen a star change in brightness and they were amazed.  They called omicron ceti, Mira which means “The Wonderful Star”. 

Astrognome Astronomy Perseid Meteor Shower

The Perseids

I observed the Perseids last night Aug 12th/13th and saw 81 meteors between 11.15 pm and 03.45 am. There were some fantastically bright meteors. I don't have a camera so I can't show you any pictures of the ones I saw.

There did appear to be some confusion when the night of maximum would occur and a few days running up to the maximum various press reports were saying that you could see the Perseids, It is true there would have been a few meteors either side of maximum but the night of 12th/13th was the night with the best chance of seeing the Perseids.

Tuesday 11 August 2015

Astrognome Astronomy Perseid Meteor Shower

Perseid Meteor Shower

On the night of August 12th/13th the Earth will pass through the stream of dust left by a comet, we will see lots of shooting stars or meteors. This is the Perseid Meteor shower.

Shooting stars have nothing at all to do with stars they are tiny grains of dust, which burn up as they enter the Earth's atmosphere. They can be seen on any clear night of the year. However when the Earth passes through a stream of material left by a comet we see lots of meteors this is a meteor shower.

The Perseid meteors are so called because they all appear to come from the constellation of Perseus. This  meteor shower is connected with comet Swift Tuttle, it was discovered in 1862. The comet was approaches the Earth every 130 years and was last close to the Earth in 1992 , it will return again in 2125.

comet swift tuttle in 1992

It is possible to see meteors a few days either side of Aug 12/13 but this is when most meteors will be seen. If you look up into the sky after 11.00 pm you will be unlucky not to see at least one Perseid. They only for a fraction of a second so you have to be quick, you can look in any direction, Perseids are usually bright and white in colour.

The Perseid meteor shower has a long history, having first been recorded by the Chinese in 36 AD.

 In 258 AD, a Christian called Lawrence promised the Roman emperor Valerian all the wealth of the Empire. Valerian thought he meant gold and silver, while Lawrence meant that the poor and sick people of the Empire were its wealth. Valerian took a dim view of this and had Lawrence roasted alive. The following night the Perseids came through exactly on schedule and people who saw this believed these were tears from heaven. Later Lawrence was made a Saint; hence the old name for the Perseids was ‘The Tears of St Lawrence’.   

In 1535 the French explorer Jacques Cartier was exploring the land we now call Canada. In August of that year he arrived at a very large river. The Perseids were coming through as usual, and as Cartier knew the story, he called the river after St Lawrence.

Jacques Cartier

Good Luck with your meteor watching!!

Monday 10 August 2015

Astrognome Scrapbook August 10th 1080 Bright Comet

Comet of 1080.

At present in the sky is comet  C/2014 Q1 PanSTARRS, it is low in the sky and most easily seen by people in the southern hemisphere. It is a spectacular sight in binoculars showing 3 tails. The comet at the moment is passing through the constellations of Crater and Hydra

However 935 years another comet was also observable in the same part of the sky. Discovered by the Chinese astronomers  on August 10th 1080 this comet which was discovered just south of Coma Berenices passed through Crater and Hydra. It was visible for 36 days. The two comets do have different paths.

The 1080 comet  was not visible as long as C/2014 Q1 but was almost certainly brighter.

Thursday 6 August 2015

Astrognome Scrapbook August 6th 1809 birth of Lord Tennyson and Astronomy

Lord Tennyson Aug 6th 1809- Oct 6th 1892

Alfred Tennyson, 1st Baron Tennyson was born on August 6th 1809. He would go on to become Poet Laureate during much of the reign of Queen Victoria. He is one of the most popular of British poets.

He also had an interest in astronomy!

Astronomy was a significant and positive muse for Tennyson that enabled him to explore questions of faith, doubt and immortality.  In his ‘Locksley Hall’ (1837-8), Tennyson describes his own experience of astronomical observation. He tells the reader how ‘Many a night from yonder ivied casement, ere I went to rest / Did I look on great Orion sloping slowly to the West’. He also writes ‘Many a night I saw the Pleiads, rising through the mellow shade.

He also owned  a small telescope that he used to look at the night sky. He knew many well known astronomers including Charles Pritchard, Savilian professor of Astronomy at Oxford University and Norman Lockyer who built a solar observatory, discovered Helium and was the first editor of the Nature magazine.