Astrognome 100 Great Stars No 57 Mu Cephei

 

Mu Cephei

Those who think that the stars are not highly coloured need only look at Mu Cephei the star that William Herschel called the Garnet Star due to its red colour. The star is a M2 supergiant with a temperature of around 3,500 degrees much cooler than our Sun. Mu lies at a distance of about 940 light years although there some doubt as to how accurate that measurement is.

Mu is a variable star it varies between magnitude 3.4 to 5.1 and can be followed by the naked eye if the sky is very clear or more easily by using binoculars. Mu is a semi regular variable star with a period of between 860 to 4,400 days.

Like all stars of its size Mu is unstable its blowing gas away and has created a huge surrounding shell that is a third of a light year across. It does appear that Mu is large enough to become a supernova in the future.

Maria Mitchell Observatory and a Cook

 

Maria Mitchell Observatory and a Cooke

The Maria Mitchell Observatory was founded in 1908 in Vestal Street Nantucket Massachusetts. The observatory was named after Maria Mitchell America’s (181-1889) first professional woman astronomer.

In 1952 the observatory housed a 5 inch clark telescope which was given to Maria Mitchell in 1859 by the women of America and used as a guide scope for a Cooke photographic triplet telescope of 7.5 inches aperture.

I do not know when the observatory acquired the Cooke and how long it was used there if it indeed is still there today?

Astrognome 100 Great Stars No 56 Mizar and Alcor

 

Mizar and Alcor

You would think that one of the best known stars in the sky would be completely understood. Think again. The most famous of double stars is Ursa Major’s naked eye pair Mizar and Alcor the only double for which each member has a name. Mizar has a magnitude of 2.0 while Alcor has a magnitude of 4.0.

It is said that the Arab astronomers of 1,000 years ago used the Mizar/Alcor system as a way of testing people’s eyesight. Haze in the sky can it make it difficult to see Alcor.

However there is a slight mystery because some astronomers wonder if they are they a true double system, Mizar lies at a distance of 78 light years while Alcor lies at a distance of 81 light years. If these results are suspect to doubt and they are a true pair then their separation from each other is about 0.27 light years meaning that they take around 0.75 million years to orbit each other.

A Partial Eclipse from Manchester and a Victoria Shilling

 

A Partial Eclipse and a Victoria Shilling

On May 17^th 1863 there was a partial eclipse of the Sun visible over Britain and this interesting account from the Manchester Literary and Philosophical Society shows how you could relate what was happening to a Victoria Shilling!

Suppose a Victoria Shilling to represent the Sun, the Moon will appear to touch it first on the right side, at the last R in the word BRITANNIAR and to leave it at the left side of the letter I in the word GRATIA.

A portion of the right hand side of the upper part of the Sun will therefore be concealed.

When the next partial eclipse occurs over Manchester it might be interesting to note if the Manchester Astronomical Society might repeat this advice but using a modern coin!

Astrognome 100 Great Stars No 55 Mira

 

Mira

The first known variable star Omicron Ceti or Mira which means the Wonderful. It was discovered by the Dutch astronomer David Fabricius who incidently was a friend of Tycho Brahe the last great pre telescopic astronomer in 1596, he saw it as star of the 3^rd magnitude. It then disappeared and was seen a few weeks later. Then in 1603 Johannes Bayer who gave the 24 brightest stars of each constellation a letter from the Greek alphabet staring with the brightest being alpha then beta down finally to omega. Bayer saw it as 3^rd magnitude stars and allocated the it the letter omicron. Shortly afterwards it disappeared again.

Astronomers then noted that Mira returned to its brightest every 331 days and varied in brightness from magnitude 2 when it can easily been with the naked eye down to magnitude 10 when a small telescope is needed to see it. Mira lies at a distance of about 300 light years and is a red giant with a spectral class of M7.

Mira is the prototype of a very large class of red giant variable stars, the Mira type variables. These stars pulsate over semi regular period of time, they are approaching the last phase of their lives. Eventually Mira will loose all its gases into space and will become a planetary nebula. When the star passes through that stage all that will be left will be the core of the star which will be a white dwarf. This is what eventually will happen to our Sun.

Manchester wants to know if stars can be seen from a coal mine

 

Manchester wants to know if stars can be seen from a coal mine

On the 14^th January 1865 Lydia Beaufort was asking astronomers in Manchester if it was possible to see stars from the bottom of a coal mine. Lydia Beaufort continues that she has read somewhere recently that this is true but asks if this is a popular myth.

I am afraid that I cannot provide an answer from any astronomers from Manchester as no records of any replies appear to exist.

Astrognome 100 Great Stars No 54 Merope

 

Merope

Little in the sky is more attractive than the delightful seven sisters or Pleiades in the constellation of Taurus the Bull. Its an open cluster, 7 stars in order of brightness are Alcyone, Electra, Maia, Merope, Taygeta, Caleno and Sterope. They are named after the daughters of the god atlas and the mortal Pleione. Only Alcyione has a Greek letter and that is eta. All the seven sisters have Flamsteed number Merope is 23 Flamsteed.

Although there is nebulosity all around the Pleiades Merope is enmeshed in a cloud of dusty gas, the stars in the Pleiades are not hotter enough to ionize the gas and make it glow. Instead the tiny dust grains embedded in the cloud scatter and reflect the starlight to make the Pleiades Reflection Nebula. The reflection nebula is at its best around Merope.

Merope and the other Pleiades which form this open cluster are young star being at most only around 100 million years old, and lie at a distance of around 400 light years. The Pleiades are also known as Messier or M45.

R C Johnson Observatory

 

R C Johnson Observatory

This neat and compact observatory of Mr R C Johnson at Bebington, Cheshire was described at the Literary and Philosophical Society of Liverpool on March 18^th 1878. It is of two stories the lower one is circular, made of bricks and enables the telescope to be raised above surrounding objects and is utilised as a laboratory or photographic room. The upper equatorial room is of the drum dome form, also circular; all but the lowest foot being a continuation of the wall of the lower room, and is made of timber covered with corrugated zinc.

The telescope is an equatorial reflector by Mr John Browning with silvered glass speculum of 9.25 inch diameter. The pier which supports it rises from a firm foundation and is carried through without touching either floors. It is hollow in the centre and open down one side, so that a well ventilated space is allowed for the fall of the weight of the driving clock.

R C Johnson would go onto become a president of the Liverpool Astronomical Society between 1882-1884.

Astrognome 100 Great Stars No 53 Megrez

 

Megrez

Delta Ursa Majoris or Megrez which means the base of the bear’s tail is the faintest of the stars that make up the part of Ursa Major that is referred to as The Plough. Its probably the one group of stars that is most easily recognised even by non astronomers. Megrez lies at a distance of 80 light years and is an A3 class star with a magnitude of 3.1.

There are however some mysteries connected with Megrez astronomers in ancient Greece ranked it as the same brightness as the other stars in the Plough, which clearly it is not now. Either the astronomers of 2,000 years ago were wrong or something else is going on.

Over the past 40 years or so I have seen Megrez change in brightness by over a magnitude. It is possible that Megrez is one of what astronomers call a secular variable star. This is a star that changes in brightness over a very long period of time.

The next time you look at the Plough make a note of how bright Megrez appears and then do it again in a few months time.

Lectures on Astronomy

 

Lectures on Astronomy,

During April and May 1841 a course of 6 popular lectures on astronomy were give at the mechanics Institute at Driffield in the East Riding of Yorkshire by Dr Henderson of the Liverpool Observatory. 

Dr Henderson was the author of various works on astronomy, geography and navigation.

Comet Klinkerfues seen over Whitehaven

 

Comet Klinkerfues seen over Whitehaven

Comet Klinkerfues 1854 was seen from the Whitehaven Observatory on the night of October 7^th 1854. The comet had been discovered by the German astronomer Ernest Klinkerfues on the night of September 12^th 1854 at the Berlin observatory. From Whitehaven it was described as looking like a round nebulous body without any appearance of a tail. The comet was seen in Ursa Major the Great Bear.

There were very few observations of the comet and it is therefore classed as a near parabolic comet with no certainty when it will come close to the Sun next.

Astrognome 100 Great Stars No 52 Lambda Bootes

 

Lanbda Bootes

19^th century astronomers found the spectra of stars so varied that it seemed obvious that stars had to made of different substances. But not so fast it now appears that there are many different types of stars that a grouped together into different groups.

And then there is lambda Bootes a dwarf star. It lies at a distance of 99 light years and shines with a magnitude of 4.2 it’s surface temperature is between 8700 to 8900 degrees and is an A0 peculiar type spectrum. This temperature is a bit cool for its class. Lambda is the lead star of a small group of similar stars whose spectra does not match up with its temperature.

Astronomers are studying stars like Lambda Bootes to try to work out why there is an abundance of metals in the spectra. The star is trying to tell us something. The problem is astronomers are not quite sure what yet.

The Astronomy show

 

The Astronomy Show 

On the Astronomy Show today the night sky for the next 7 nights, the latest astronomy news,  the A-Z of constellations , the Messier Marathon plus the astronomical anniversaries. The Astronomy Show Monday evenings between 7.00 pm and 9.00 pm  only on Drystone radio 103.5 FM, you can hear the show live on line at www.drystoneradio.com or listen to the programme later on the Drystone Radio podcast.

Astrognome 100 Great Stars No 51 Kepler's Star

 

Kepler’s Star

We know that the brilliant star that was studied by Johannes Kepler in 1604 was a supernova in the constellation of Ophiuchus the Serpent Bearer. It reaches a maximum brightness of -2 making it brighter than Sirius the brightest star in the sky. It was the last supernova that was easily seen in our galaxy. However by studying supernova in other galaxies astronomers have been able to group supernova in two groups. These are type 1 and type 2. 

Kepler’s star was believed to be a type 1 supernova these are stars that have a lack of hydrogen in the spectra and can be found anywhere in galaxies. Where as type 2 supernova show hydrogen in their spectra and can only be seen in the disks of galaxies and are caused by the collapse of the core of the star.

In 1604 when Kepler’s star was seen none of the modern technology that astronomers use today existed it appeared around 2,000 light years above the galactic disk suggesting that it was a type 1 but observations of the expanding gas shell tend to suggest it was a type 2 supernova.

Over 400 years after its discovery Kepler’s Star is still wrapped in mystery.

New Sun Spot Group over Manchester

 

New Sun Spot Group over Manchester

Thursday 25^th October 1905

To the Editor of the Manchester Courier, Sir- There is another naked eye group of stars now on the visible surface of the Sun. The portion which is visible through the smoke and cloud is an immense spot.

Yours &c William C Jenskins

Observer

Godlee Observatory

Manchester

Astrognome 100 Great Stars No 50 Kapteyn's Star

 

Kapteyn’s Star

Kapteyn’s Star a class M1 red sub dwarf lies at a distance of only 12.76 light years in the constellation of Pictor the Easel. Due to its closeness it moves across the sky at a very speedy 8.7 seconds of arc per year. Kapteyn’s Star is second only to Barnard’s Star for its speed across the sky. It is presently headed southwards towards the constellation of Dorado the Goldfish It was named after the prominent Dutch astronomer J C Kapteyn (1851-1922).

The star came within just 7 light years of the Sun 10,800 years ago and has been moving away ever since. Kapteyn’s Star shines with a magnitude of 8.8 meaning its just visible in binoculars. Its surface temperature is 3,500 degrees, much cooler than our Sun.

In 2014 it was announced that Kapteyn’s Star plays host to two planets, one of them is considered to be the oldest possible habitable planet with an age of around 11 billion years. The possibility of life on either one must be considered low as most red dwarf stars produce very powerful solar flares.

Mr Baxendell and Z Delphinus

 

Mr Baxendell and Z Delphinus

On October 24^th 1863 Mr Baxendell in Manchester announced the discovery of a new variable star in Delphinus with a magnitude of 8.6. By December it had fallen to magnitude 12. After conjunction with the Sun it was found again on July 29^th 1864 as a magnitude 13 object. From then until September 5^th it rose to magnitude 8.4.

 Although not given a variable star designation at the time I believe this star is Z Delphinus a long period variable star with a period of 304 days and varying between 8.3 and 15.3

Astrognome 100 Great Stars No 49 IRC +10 216

 

IRC +10 216

The first variable star to be discovered was omicron ceti or Mira in the constellation of Cetus the Whale in 1596. We know today that there are many red giant stars that fall into the class of variable stars that astronomer refer to as Mira type variables. IRC + 10 216 is an extreme member of this class.

It is effectively invisible to the eye no one even knew it was there until 1969 when it was found to be a very bright infrared source in the sky. Its actually a huge cloud of dusty gas abut 1.5 light years across lying at a distance of about 500 light years. Buried within it is the variable star CW Leonis a cool Mira star with a temperature of only about 2,300 degrees. However where Mira has a period of 331 days CW Leonis has a much longer period of 649 days.

IRC +10 216 is studied by infra red astronomers rather than optical astronomers and the star is loosing its mass at a rate of 0.00002 solar mass per year. The star will eventually loose all of its gas, form a planetary nebula and end its life as a small white dwarf star.

John Goodricke, Delta Cepheus and the Distance to the Galaxies

 

John Goodricke, Delta Cepheus and the Distance to the Galaxies

John Goodricke who was deaf was on one the fathers of variable star astronomy. He worked with Edward Pigott in the city of York between 1781 and 1786 when he died at the tragically young age of 21.

Goodricke and Pigott explored the sky they explained that the variations of the star Algol in the constellation of Perseus were caused by an unseen body eclipsing Algol. The same principal is used by astronomers today to look for planets orbiting other stars. They then went on to both discover a new variable star on the same night, the 10^th September 1784, Pigott discovered eta Aquila and Goodricke discovered beta Lyra. I described this as a night to remember in york.

The indefatigable Goodricke then went onto to discover the variability of the star delta Cephei in the constellation of Cepheus the King on the night of October 23^rd 1784. This was to prove to be one of the most important astronomical discoveries.

Delta Cepheus is of tremendous value to astronomers today, Goodricke could not know the importance of his discovery. Cepheid variable stars are used to work out the distance to other galaxies. It was in 1912 that Henrietta Leavitt working at Harvard realised that there is a relationship between the Cepheid variable stars a pattern was seen that the brighter ones seem to have longer periods and that Cepheids were very luminous stars and there was a relationship between the periods and distance.

If Cepheids could be found in other galaxies the distances could be worked out. They were and this allowed astronomers to work out how far away the galaxies were. This was down to the discovery of delta Cepheus in 1784 by the deaf astronomer John Goodricke the discovery of this relation with the cepheids in 1912 by Henrietta Leavitt who was also partially deaf. This relationship is known today as the Period Luminosity Relationship.

Astrognome 100 Great Stars No 48 Gamma 2 Velorum

 

Gamma 2 Velorum

The gamma Velorum system in the constellation of Vela the Sails is actually made up of 4 stars. With a combined magnitude of 1.7 and contain the closest and brightest example of the rare type of star known as a Wolf Rayet star.

It is gamma Velorum 2 we will be looking at as it is a wolf rayet star. These are named after the 2 French 19^th century astronomers Charles Wolf and Georges Rayet who first discovered this class of star. These stars have a spectral class of either WC or WN, WC stars have helium and carbon in their spectra while WN stars have helium and nitrogen in theirs.

Wolf Rayet stars are massive stars and because they loose their mass at an incredible rate they have very short lives in astronomical terms. Gamma 2 Velorum which is over 1,000 light years away is a WC8 star and is accompanied by an 07 giant star, many wolf rayets are double stars. Gamma 2 has a temperature of an eye watering 55,000 degrees its companion a mere 35,000 degrees!!! Our Sun by comparison is a mere 5,800 degrees. Gamma 2 will almost certainly end its life as a supernova.

The Disc of Venus seen with a Cooke

 

The Disc of Venus seen with a Cooke

ON October 22nd 1863 on turning my 6 inch Cooke telescope upon Venus I was much surprised to see almost the whole of the unilluminated disc pf the planet; it was so striking I appearance, that I thought it must be the resemblance of the Moon, which made me fancy that I could see the unilluminated portion. My sister in law, whom I called to witness the planet, but without telling her what to look for, said she instantly saw the whole disc. The atmosphere was beautifully clear, but still the planet was so far past conjunction, that I should scarcely have imagined the phenomena would be visible.

J F Barber Stanton by Dale Nottingham

AStrognome 100 Great Stars No 47 Gamma Draconis

 

Gamma Draconis

The claim to fame for Gamma Draconis or Eltanin which means the Great Serpent and is a star lying at a distance of 150 light years and shines with a magnitude of 2.2 is in its position.

Eltanin is the closest star to the ‘winter side’ of the ‘solsittial colure’, (this is the circle in the sky that passes through the celestial poles and the solstices) lying almost 75 degrees north of the winter solstice in Sagittarius. Eltanin’s high northerly position of 51.5 degrees north of the celestial equator takes it through the zenith, the point overhead as seen from London.

In the 1700s London was a centre for the measure of precise stellar positions. One of the major problems in establishing them is the refraction of light caused by the Earth’s atmosphere. A star that passed overhead was required hence Eltanin. The star seemed ideal to use in the search for parallax and therefore distance.

The observations made in 1728 by James Bradley showed that the star was shifting as a result of the movement of the Earth. Bradleys observations showed that there was a 26,000 year axial wobble or precession on the Earth and that changes to the pole star and the visibility of the constellations.

A Cloudy Eclipse in Manchester with a Grubb and a Cooke

 

A Cloudy Eclipse in Manchester with a Grubb and a Cooke.

On Wednesday 30^th August 1905 a partial eclipse of the Sun was visible over Britain and plans were put in place to observe the event in Manchester.

Sadly the weather was cloudy and at 11.15 am just 16 minutes before the eclipse was due to begin would be observers watched in vain as the sky became cloudy.. It was true that at about one o’clock there were signs of the passing of the Moon’s dark shadow, the sky being overcast as if there was about to be a heavy downpour of rain. But beyond this there was nothing visible.

At the Godlee Observatory in the Manchester Municipal School of Technology arrangements were made to observe the eclipse. Mr W C Jenkins, secretary of the Manchester Astronomical Society who is also Curator of the Observatory had intended by means of the projection method, which shows the progress of the Moon on the screen attached to the Grubb 8 inch telescope to make notes of the period of contact and other interesting details. Photographic apparatus had been fixed, so the negatives of the various phases could be obtained, but as already stated the preparations were in vain.

Though on a less elaborate scale, some arrangements had also been made at the physics’ laboratories at the Victoria University of Manchester. The solar eyepiece had been fixed to the 10 inch Cooke telescope in the dome roofed observatory. Half an hour before the eclipse was due a glimpse of the Sun was obtained, but shortly afterwards the sky became completely clouded over and not another view of the Sun was obtained during the whole progress of the phenomenon

Aurora Over Halifax

 

Aurora over Halifax

On October 20th 1870 Joseph Gledhill who was the assistant astronomer to Edward Crossley at his observatory at Park Road, Halifax and who normally used the 9.3 inch Cooke telescope saw a fine display of Aurora.

At 7.30 pm a bright red magnetic cloud lay in Auriga, a little later it was in Lynx. The large stars in the back of Ursa Major and the Northern Crown in the West marked the upper limit of the bright segment to the westward.

At 10.00 pm the arch of fiery red magnetic clouds was well seen, it extended from N E to W.

No bright columns were seen this evening

Astrognome 100 Great Stars No 46 Gamma Cassiiopiea

 

Gamma Cassiopeia

Like opposing hands of a clock the Plough and the letter ‘W’ of Cassiopeia wheel about the North Star. Both can be seen all year round from Britain meaning they are both circumpolar., They never set and are visible in the sky throughout the year.

The letter ‘W’ of Cassiopeia is formed from five stars. Beginning at the western end, or the right hand end, we see the star Beta whose proper name is Caph which means ‘palm’. Next comes alpha or Shedar which means ‘breast’, gamma which has no name marks the middle star, then comes delta whose name is Ruchbah, which means ‘knee’ and finally epsilon, which again has no name and is quite noticeably the faintest of the five stars.

Probably the most interesting of the stars of the ‘W’ of Cassiopeia is gamma, the middle star, which is one of the brightest stars to have no proper name. Gamma is a star that sometimes changes in brightness. Stars that do this are called variable stars. It is a rare type of variable star, it varies between magnitude 1.6 to magnitude 3.0 and is the prototype star for the small group of Gamma Cassiopeia type variables. It lies at a distance of 550 light years. These are massive B0 class stars with temperatures of around 25,000 degrees.

Gamma Cassiopeia is normally about the same brightness as the other stars of Cassiopeia, apart from the fainter epsilon, but between 1932 and 1942 it became noticeably brighter than the other stars and was even brighter than the North Star.

This changed the appearance of Cassiopeia considerably. It is therefore well worth keeping an eye on gamma as it is very capable of springing a surprise on us.

Astrognome 100 Great Stars No 45, 83 Ursa Majoris

 

83 Ursa Majoris

An interesting star 83 Ursa Majoris is a star that I have watched for over 40 years, it normally shines at magnitude 4.6 and lies at a distance of around 520 light years. Its a red giant star with a spectral class of M2 with a surface temperature of 3,600 degrees much cooler than the Sun.

83 Uma is officially listed as a semi regular star with a magnitude varying between 4.6 to 4.7. I have seen it beyond those limits, however on August 6^th 1868 the Irish astronomer John Birmingham saw the star rise to magnitude 3.3, the following night it had returned to its usual magnitude 4.6.

It is a star that is certainly worth while having a look at if at any time you happen to be looking at the handle of the Plough.

Astrognome 100 Great Stars No 44 FU Orionis

FU Orionis

Stars that do something are fun to watch. In 1939 a ‘new star’ erupted in northern Orion out of nowhere. It reached a photographic magnitude of 9.0 making it easily visible in small telescopes. Searches of old photographs showed the perpetrator to be a faint 16^th magnitude star.

FU Orionis is the prototype of a small group of less than 20 or so stars of similar nature. Unlike a normal nova which remains bright for a relatively short period of time measured in days, weeks or occasionally months FU Ori stayed bright for around 60 years before slowly fading.

Its a nova but not as we know it. None of the FU Ori type variables have been seen to return to their normal pre outburst brightness. One suggestion is that FU Ori stars are extreme examples of a class of variable stars known as T Tauri stars. These are young stars usually being less than 10 million years old and are located near star forming clouds.

A Cooke at the Republic Observatory

 

Occultation of Iapetus Observed from the Republic Observatory in Johannesburg.

On October 17^th 1963 using the 6 inch Cooke telescope at x300 magnification at the Republic Observatory in Johannesburg, South Africa astronomers saw the Saturnian moon Iapteus occulted by Saturn. Iapetus was discovered by Cassini in 1671,

The first dimming occurred at 18h 58 m UT the light was finally extinguished at 19h 07m. These observations were confirmed by the Astronomical Observatory at Madrid.

The Union Observatory was originally the Meteorological Observatory built in 1905, it became the Union Observatory in 1912, until 1961 and finally the republic Observatory until it closed in 1971.

Astrognome 100 Great Stars No 43, 47 Tucanae

 

47 Tucanae

A globular cluster in the constellation of Tucana the Toucan a southern hemisphere constellation. It can be seen with the naked eye as a magnitude 4.1 object. It lies at a distance of 13,000 light years and is 120 light years across. It is the 2^nd brightest globular in the sky after omega cenaturi, 47 Tuc contains millions of stars.

It was first seen by the French astronomer Nicolas Louis de Lacaille in 1751 while he was observing the sky from South Africa. However it was the German astronomer Johann Elert Bode who gave it the number 47 in his star catalogue published in 1801.

There have been surveys by the Hubble Space Telescope to look for planets orbiting stars, but none have been found yet. There are however 100s of x ray sources in 47 Tuc and some astronomers believe that there is a black hole in the centre of the cluster. This has been reinforced by astronomers who in 2017 may have located a massive black hole in the cluster.

Astrognome 100 Great Stars No 42, 40 Eridani

 

40 Eridani

Beid and Keid, unrelated stars meaning ‘the egg’ and ‘egg shells’ in Arabic carry the same Greek name omicron Eridani. We call Beid omicron 1 and Keid omicron 2 though astronomers know them better as John Flamsteed’s 38 and 40 Eridani. We don’t need to worry about 38 Eridani our target is 40 Eridani.

40 Eridani shines with a magnitude of 4.4 and is a K0 class star cooler than the Sun and lies at a distance of 16 light years. There are two companion stars Eridani 40 B and C which were discovered by William Herschel in 1783. Eridani 40 B is a relatively unimportant K class star with a magnitude of 9.5 meaning that you would need a good pair of binocular or more likely a small telescope to see it.

40 Eridani C on the other hand is far more interesting. It is a magnitude 11.2 white dwarf star. Although Sirius the brightest star in the sky has a while dwarf companion star often referred to a ‘the pup’ is closer than 40 Eridani it is much brighter than the pup making it very difficult to study. This is not he situation with Eridani 40 C. It is the easiest white dwarf star to study.

At one time this white dwarf star would have dominated this triple star system before evolving into a giant star before ending up as we see it now as a small white dwarf star at the end of its life.

Astrognome 100 Great Stars No 41 Fomalhaut

 

Fomalhaut

The southern most of the first magnitude stars that can be seen from Britain, if you can locate the Square of Pegasus which can be found in the autumn sky and then use the two right hand stars of the square, draw a line downwards and you will reach Fomalhaut, which is the brightest star in the rather obscure constellation of Piscis Austrinus the Southern Fish. The constellation can be best seen from the southern hemisphere.

Fomalhaut shines with a brightness of 1.2 and lies at a distance of 25 light years. It is an A3 class star meaning that it is hotter than our Sun. It is not a single star but a triple system, Fomalhaut B is a variable star TW Piscis Austrini which is a red dwarf star lying nearly 1 light years away, while Fomalhaut C or LP 876- 10 which was catalogued by the Dutch American astronomer Willem Luyten is another red dwarf lying around 2.5 light years from Fomalhaut.

It should have been one of the four royal stars, together with, Aldebaran, Antares and Regulus, since 4,000 years ago it almost marked the winter solstice; but, as its position was well south of the celestial equator it was replaced by the more accessible Altair.

1881 BA meeting in York and Cookes

 

1881 BA meeting in York and Cookes

Messrs Thomas Cooke and Sons of York had a display of scientific instruments for the meeting of the British Association for the Advancement of Science. It was the 50th anniversary meeting in York. The first was held in York in 1831.

Cookes had on display an achromatic telescope OG of 15.5 inches in a brass cell. In addition there was a transit instrument and a large fixed equatorial telescope for the Spanish Transit of Venus expedition in 1882.

There was also an electrically controlled chronograph for recording astronomical observations. In addition a solar spectroscope with 5 prisms and double ray reversion equal to 20 prisms.

Astrognome 100 Great Stars No 40, 51 Pegasi

 

51 Pegasi

We speculate about life in the universe and today using giant telescopes on Earth and orbiting satellites we know of over 4,000 planets orbiting around other stars.

On October 6^th 1995 two Swiss astronomers observing the star 51 Pegasi discovered the first planet to be found orbiting a star. The star 51 Pegasi is a 5^th magnitude star in the constellation of Pegasus, The Flying Horse. 51 Pegasi is a G2 dwarf star with a surface temperature of 5,600 degrees only slightly cooler than the Sun and lies at a distance of around 50 light years.

The planet which is known as 51 Pegasi b orbits very close to its parent star being only around 7.5 million miles away, (by comparison Mercury the closest planet to the Sun is 36 million miles away). 51 Pegasi b and is believed to have a surface temperature of around 1,200 degrees and takes just over 4 days to orbit.

Cookes and Romania

 

Cookes and Romania

In early 1927 Cookes was contacted by the Resita Company in Romania with reference to their geodetic equipment.

Literature from Cooke Troughton and Simms through their representative Captain Boxshall were sent to the company and secured a very respectable order and it was hoped that this with be the first of many with Romania.

The image shows a share from the Resita works in 1926

Astrognome 100 Great Stars No 39 FG Sagittae

 

FG Sagittae

Most stars do not change over a human lifetime. Though they may vary they do not fundamentally alter their natures. To learn how stars age we use theory to string the various kinds together. It is therefore interesting to see a star transform itself as we watch. Such a star is FR Sagittae.

FG Sagittae lies at a distance of around 4,000 light years away in the small constellation of Sagitta the Arrow. When first recorded in 1896 it was the centre of the planetary nebula Henize 1-5. It appeared blue and had a magnitude of 13.6. It slowly brightened until in 1969 it was brighter by 4 magnitudes and in 1991 it was at magnitude 9.0.

The brightness changes was a bit of a sham because the star was cooling, changing from a B4 supergiant in 1955 with a temperature of around 15,000 degrees to a G2 star today with a temperature of 6,500 degrees.

As the central star of a planetary nebula FG Sagittae was once a huge red giant star like the Mira type variable stars.

In 1992 the star suddenly faded by nearly 5 magnitudes then recovered to around magnitude 10. FG Sagittae is losing carbon rich matter that condenses into carbon dust which will hide the star until the soot dissipates. Interestingly this is what happens to a small group of variable stars, the R Corona Borealis stars.

R Corona Borealis was discovered in 1795 by Edwarde Piggot while living in the city of Bath. Piggot has worked with the death astronomer John Goodricke in York from 1781-1786

Astronomers have wondered for decades where these weird R Corona Borealis stars came from, maybe FG Sagittae is giving us the answer.