Friday 31 July 2015

Astrognome Scrapbook 31st July 1964 Ranger 7 sends close up photos of the Moon

Ranger 7

In the early 1960s NASA was attempting to obtain good close up photos of the lunar surface in preparation for the Apollo manned missions. Project Ranger was a series of unmanned probes that were designed to fly to the Moon then crash into the surface sending back photos right up until the moment of impact.

The first 6 missions which had started in 1961 were all failures. The first successful crash landing was Ranger 7 on 31st July 1964. The photographs were the best close up views of the Moon that scientists had received.

This is the Mare Nubium area of the Moon

There was so much concern over the failure of earlier Ranger missions that the project had been dubbed project 'shoot and hope'. Following Ranger 7 two further successful ranger missions were launched to the Moon.

Tuesday 28 July 2015

Astrognome Scrapbook 28th July 705 Mars occult's a star

An occultation of a star by Mars.

The ancient Chinese made extensive observations of the night sky during the last 4,000 years. Since the 1950s western astronomers have been able to research those records. Their observations tell us that on July 28th 705, 1310 years ago Mars occulted the star we now refer to as 1 Libra.

 An occultation occurs when one body passes in front of another. Therefore a planet can pass in front of or occult a star or even another planet. This means that the star would appear to disappear for a period of time.

Saturn about to be occulted by the Moon as seen through a telescope

This observation is one of 59 well determined occultations or very close to occultations that were recorded by the Chinese. At this time there were no telescopes, certainly none that we were aware of, so in some cases the two objects may have been so close together that they could not be separated by the eye alone and were therefore recorded as an occultation, but a telescope would have shown that an occultation did not occur.  

An eclipse of the Sun by the Moon is also an example of an occultation. 

Monday 27 July 2015

Astrognome Astronomy The Centre of the Galaxy

The Centre of the Galaxy

In the south in the summer skies low down is the bright red star Antares brightest star in the constellation of the Scorpion.  

To the left and just as low down in the sky is the rather faint constellation of Sagittarius the Archer. On a clear night it is possible to see a faint ribbon of stars passing from directly overhead and leading down to the horizon passing through Sagittarius, this is the Milky Way, our galaxy.

If you can locate Sagittarius, and you don`t need a telescope, you will be looking towards the centre of our galaxy. This is always a wonderful if scientifically unremarkable thing to do during summer evenings.

Friday 24 July 2015

Astrognome Astronomy Poniatowski’s Bull

Poniatowski’s Bull

Some distance south of the brightest star in Ophiuchus the serpent bearer it is easy to find the stars beta and gamma Ophiuchi. Close to gamma is a little group of stars none of which have Greek letters.

These stars are labelled 66 Ophiuchi, 67, 68, and 70. These once formed a little constellation called Poniatowski’ Bull. It was placed in the heavens by Abbe Poczobut of Wilna in 1777 to honour Stanislaus Poniatowski, King of Poland.  He was the last King and Grand Duke of the Polish–Lithuanian Commonwealth.

Alas similar to that commonwealth the constellation also no longer survives today and cannot be found on any modern star map.

If you want to find a constellation with Polish connections move slightly to the left and look for the small and faint constellation of Scutum the shield.  It was originally known as Scutum Sobiescianum (Shield of Sobieski), today it is shortened to Scutum.

Scutum was named in 1684 by Polish astronomer Johannes Hevelius to commemorate the victory of the Christian forces led by Polish King John III Sobieski in the Battle of Vienna in 1683. Later, the name was shortened to Scutum.

Thursday 23 July 2015

Astrognome Scrapbook 23rd July 1995 discovery of comet Hale Bopp

Comet Hale Bopp
Twenty years ago on June 23rd 1995 possibly the most observed comet of the 20th century was discovered. Comet Hale Bopp would go on to become a comet everyone knew about. The co discoverers Alan Hale and Thomas Bopp were both American astronomers.

When discovered it was about 700 million miles away in between the orbits of Jupiter and Saturn. At its brightest in early 1997 it was so bright that it could even be seen by people who lived in cities. 

In March 1997 there was an eclipse of the Sun visible from China, Mongolia and Siberia; it was even seen then in broad daylight.

It has been calculated that the comet last visited the Earth in 2315 BC. It would have been as bright then, sadly no observations exists to confirm this. Its next return will be around 4385 AD.

Comets have always had a reputation for being the bringers of fear and doom. With Hale Bopp some people believed there was a UFO following it. On March 26, 1997, police in California discovered the bodies of 39 members of the Heavens Gate group who had committed mass suicide in order to reach what they believed was that alien space craft following the comet.

The nucleus or centre of the comet was about 50 miles across. Hale Bopp attracted so much interest and was so widely followed by the press that it had a much greater impact on the general public than the return of Halley’s Comet in 1986. It’s believed that over 80% of all Americans saw the comet!

Wednesday 22 July 2015

Astrognome Scrapbook July 22nd 1784 birth of Friedrich Bessel

Birth of Friedrich Bessel
On July 22nd 1784 the German astronomer Friedrich Wilhelm Bessel was born. He was the first person to measure the distance to a star. He worked out the distance to the star 61 Cygni in 1838.

This star is not bright enough to have been given a Greek letter. In a constellation the brightest stars are labelled using the Greek alphabet with alpha being the brightest followed by beta, gamma and so on through too omega. However this will only give us 24 letters.

John Flamsteed made a thorough catalogue of the naked stars in the sky, that is to say stars that can be seen without needing a telescope. This was published in 1725 after his death. All these bright stars including those with a Greek letter would have a number preceded by the letters FL. The FL letters standing for Flamsteed. Today astronomers don’t normally add the FL but just use the number of the star. Hence FL 61 Cygni is usually referred to as 61 Cygni.

61 Cygni is sometimes called the ‘Flying Star’ because it moves quickly across the sky is only 11 light years away. Its distance was measured by using what is known as the parallax method.

The parallax angle p is illustrated in the following figure.

If this angle, which corresponds to a small shift in apparent position of the star when observed from different points of the Earth’s orbit around the Sun, can be measured accurately, the distance can then be determined from simple trigonometry.
Although not a bright star 61 Cygni has its place in astronomical history.

Bessel was director of the Konigsberg observatory in Germany when he made this discovery he held this position from 1810 until his death in 1846.
He worked out the position of about 75,000 stars and predicted the positions of the then unknown companion stars of Sirius and Procyon.

Astrognome Astronomy The Summer Triangle part 3 Deneb

The Summer Triangle part 3 Deneb

Deneb is the faintest of the summer triangle of stars. It is in the constellation of Cygnus the Swan but it is sometimes known as the Northern Cross for obvious reasons. The name Deneb comes from the Arabic ‘The Hen’s Tail’ In mythology Cygnus was always associated with a bird, the most celebrated legend concerns one of the many dubious adventures of Jupiter or Zeus.

Deneb although appearing fainter than Altair or Vega is much further away. It is about 1,500 light years away. The light that reaches us this summer left around the time ‘dark ages’ began in Europe around 500 AD. Deneb is about 70,000 times as luminous as the Sun. It is of course much hotter than the Sun.   If Altair, Deneb and Vega were all the same distance away Deneb would appear like a searchlight in the sky.

Cygnus lies in a part of the Milky Way which is our galaxy and even without a telescope and away from city lights it is possible to see the many faint stars that form the Milky Way.

Tuesday 21 July 2015

Astrognome Astronomy The Summer Triangle part 2 Altair

The Summer Triangle Part 2 Altair

Altair is the lowest of the three stars that make up the summer triangle. It is quite easy to find as it has a fainter star either side of it. Aquila is the brightest star in the constellation of Aquila the Eagle.

In mythology the eagle was sent from Olympus to collect the shepherd by Ganymede, who was destined to become the cup bearer of the gods.

Altair is about 16 light years away meaning that light left the star in 1999. If you were born in that year light that left Altair will be entering your eye this summer. It is also the closest of the summer triangle stars. It is white in colour which means that like Vega it is hotter than our Sun.

South of Altair there is a line of three stars; the centre one eta which looks like a letter ‘n’ is the most interesting. It is another of the so called variable stars. It was discovered in York in 1784 by Edward Pigott who worked with John Goodricke who discovered the variability of several stars including that of beta Lyra. Both Beta Lyra and eta 

Edward Pigott

Aquila were discovered on the same night September 12th 1784. Goodricke and Pigott are the fathers of variable star astronomy.

Eta Aquila can be seen to vary in brightness around every 7 days. 

Monday 20 July 2015

Astrognome Astronomy The Summer Triangle Part 1

The Summer Triangle Part 1: Vega

If you look directly overhead during summer evenings you will see a bright blue/white star. This is Vega the brightest star in the constellation of Lyra the Lyre or Harp, which according to Greek legend Apollo gave to the great musician Orpheus.

Vega is about 26 light years away, this means that the light entering our eyes this summer left Vega in 1989. Anyone born in 1989 the light from Vega left the star the year you were born!

It is blue/white in colour, this means that Vega is hotter than our Sun. The colours of stars tell astronomers which stars are hot and which are cool. Surprisingly blue/white stars are much hotter than orange/red stars.

Although Lyra is a small constellation there is a lot that can be seen without the help of a telescope.

Just below Vega you will see a small rectangle of stars the bottom right is beta Lyre or to give its proper name Sheliak. This star varies in brightness and is referred to as a variable star.  It is quite easy to watch it change in brightness every 13 days. There are many different kinds of variable stars. Beta however was first identified as variable by the English astronomer John Goodricke in 1784. Goodricke was deaf and unable to speak. He is however one of the fathers of variable star astronomy.  

To the left and slightly above Vega is the star is epsilon, it is marked as e2, this star is in fact double and if you look carefully you will see there are two stars  rather than one.

Vega was once our North Star but because the Earth wobbles very slowly the position of the North Star changes. It takes the Earth 26,000 years to wobble once. Vega will be the North Star again in about 12,000 years!

Astronomy Scrapbook July 20th 1976 Viking 1 lands on Mars

Viking 1

Viking 1 was the first successful mission to land on Mars.

The lander gave us our first views of Mars from the actual Martian surface. No definite signs of life were found.

Wednesday 15 July 2015

Astronomy Scrapbook July 15th 1965 Mariner 4 reaches Mars

Mariner 4

Yesterday the New Horizons probe became the first space craft to reach Pluto. However 50 years ago on July 15th 1965 Mariner 4 became the first space craft to reach Mars.

Although scientists knew that there were no canals or intelligent life on the red planet, many assumed that there would be tundra like plants and lichens there.

The photographs that Mariner 4 sent back although very grainy and of poor quality compared to those that are sent back from modern space craft showed that Mars rather than being covered in simple plant life looked far more hostile and resembled the surface of the Moon.

In one moment in time Mariner 4 changed all the old fashioned romantic views of Mars. Today with rovers on the surface and space craft orbiting Mars, scientists are still trying to answer questions set by the first probe to visit Mars 50 years ago, Mariner 4.

Friday 10 July 2015

Astronomy Scrapbook July 10th 1962 Launch of Telstar

On July 10th 1962 Telstar the world`s first telecommunications satellite was launched from Cape Canaveral. Telstar which was built by the American Bell AT&T company and it allowed `live` pictures to be beamed around the world for the first time.

The first picture beamed from the UK to the USA was of a young couple sitting in a river bank, the image appeared in the Daily Mail on July 13th. The couple were the young actor Richard Thorp who would go on to play Alan Turner in Emmerdale and a young model called Chloe Brown.
The idea of using satellites to provide worldwide communications was suggested in an article written in 1945 by Arthur C Clarke.

Britain received transatlantic pictures from American at 01.01 on July 11th; the image was of Mr Frederick Kappel, president of AT&T. It was received in Britain at the Post Office run Goonhilly Down tracking station in Cornwall. Due to its low orbit, transmissions could only last for about 20 minutes while Telstar was above the horizon.

It had been agreed that the first real TV programme would be bounced of Telstar on July 22nd; however on July 12th the French broadcast a French cabaret singer singing songs. This broadcast was described in the UK press as being of a pirate nature and this caused a row. The French described the broadcast as a communications experiment.

In the early 1960s radios using valve technology were unreliable; many people therefore believed that there had to be people on board Telstar changing the valves regularly.

Telstar ceased to function on Feb 12th 1963 only 7 months after its launch, this was partly caused by Atomic bomb tests, a day before the launch of Telstar the Americans launched the Starfish Prime atomic bomb which exploded at a height of 400km and was the largest man made nuclear explosion in space. Telstar will orbit the Earth as a dead satellite for about another 100,000 years.

In October 1962 the instrumental pop group the Tornados made the hit record Telstar which reached number 1 in the UK and US record charts.

Sunday 5 July 2015

Astronomy Scrapbook July 5th 2015 York and The Forth Bridge

York and the Forth Bridge

Scientific instruments made in York played a major role in the building of the Forth Bridge. Now that the bridge has been declared a World Heritage Site, it is worth remembering that the surveyors who worked out exactly where the bridge was to be built were using theodolites made in York by Thomas Cooke and Sons.

courtesy Borthwick Institute, York

The contractors who were building the bridge wanted only the best, and Cooke theodolites were the finest in the world at that time. Mr Reginald Middleton, the engineer who determined the exact location of the bridge, described the theodolites as being ‘excellent’ and ‘practically indestructible’.