Friday, 4 December 2020

The Crossley Telescope discovers Asteroid 718 Erida

 

Asteroid 718 Erida discovered by Crossley Telescope

On December 3rd 1910 Dr Curtiss and Miss Young using the 36 inch Crossley telescope discovered the asteroid 718 Erida. Dr Curtiss took the photograph and it was then discovered by Miss Young checking the photograph. The asteroid has a diameter of about 70 km, with an orbital period of 5.3 years.




The 36 inch reflector had been owned by Edward Crossley of Halifax, Yorkshire who owned Crossley Carpets the largest carpet manufacturer in the world in the 19th century. He purchased it in the 1880s from A. A. Common of Ealing, London. Although it was at the time the largest reflector in England due to the poor observing conditions in the skies over Halifax which was due to the pollution from the many factories in Halifax it was impossible to use the telescope to its best.

In the mid 1890s he donated the telescope to the new Lick Observatory in California. During the late 19th and early 20th centuries the Crossley reflector at Lick proved to be a real trail blazing telescope leading in astronomical research in many different areas. It was also the largest reflector in America until the building of the 100 inch telescope at Mount Hamilton.

Astrognome 100 Great Stars No 91 U Gemini

 



U Gemini

A remarkable variable star discovered by J R Hind in 1855. U Gemini can be found in the constellation of Gemini the Twins. It is a classic example of a dwarf nova. It is referred to as an irruptive variable and might sometimes be known as a cataclysmic variable.



Normally shinning at a magnitude of around 14 every few months it brightens to magnitude 9. The period between brightening on average every 102 days. Having said that it is its average, U Gemini can vary in brightness between 62 and 257 days.

Being a dwarf nova the U Gemini system is composed of a white dwarf and a red dwarf. A classic nova system will have a white dwarf and a giant star. U Gemini and SS Cygni are the two brightest memebers of the dwarf nova that astronomers know of.



Thursday, 3 December 2020

The Crossley Telescope discovers Jupiter's Moon Himalia

 

The Crossley Telescope discovers Jupiter’s Moon Himalia

On December 3rd 1904 Charles Perrine using the 36 inch Crossley reflector at the Lick Observatory in California discovered the 6th moon of Jupiter, Himalia. The moon was named after a nymph on the island of Rhodes and according to Greek mythology she was one of the lovers of Zeus.




Himalia is the 5th largest moon of Jupiter it has a radius of 85 km and lies at a distance of 11.5 million km for Jupiter and takes 251 Earth days to complete one orbit of Jupiter.

The 36 inch reflector had been owned by Edward Crossley of Halifax, Yorkshire who owned Crossley Carpets the largest carpet manufacturer in the world in the 19th century. He purchased it in the 1880s from A. A. Common of Ealing, London. Although it was at the time the largest reflector in England due to the poor observing conditions in the skies over Halifax which was due to the pollution from the many factories in Halifax it was impossible to use the telescope to its best.

In the mid 1890s he donated the telescope to the new Lick Observatory in California. During the late 19th and early 20th centuries the Crossley reflector at Lick proved to be a real trail blazing telescope leading in astronomical research in many different areas. It was also the largest reflector in America until the building of the 100 inch telescope at Mount Hamilton.

Astrognome 100 Great Stars No 90 Tycho's Star

 

Tycho’s Star

On November 6th 1572, W Schuler of Wittenberg witnessed a brilliant glowing star in Cassiopeia, one that outshone all the stars around it. Five days later, probably caused by poor autumn cloudy weather which is a problem in northern Europe, Tycho Brahe in Denmark also discovered this new star, or nova stellarum as it was described and the courses of astronomy and human thought changed forever.



The nova stellarum that Tycho saw was a supernova and it is referred to as Tycho’s Star because although he was the not the first to see it and indeed not the only one to observe it Tycho produced the most extensive reports on the event. At this time in history it was believed that the heavens were unchanging. This was the message sent from the church which was still very powerful in the middle ages.



Tycho’s Satr reached a maximum brightness of around -4 which is around the same brightness as the planet Venus. It was not until March 1574 that it dropped below naked eye visibility. It is believed that Tycho’s Star was a type 1 supernova which occurs when a white dwarf star pulls material from a companion star or even merges with the companion and a massive explosion is the result



Wednesday, 2 December 2020

Astrognome 100 Great Stars No 89 Tejat Posterior

 

Tejat Posterior

Tejat Posterior is probably better known as the star Mu Gemini. The meaning of the name Tejat Posterior is unknown but some Arabic sources suggest the name refers to the asterism formed by the stars mu, gamma, nu, eta and xi. Mu lies at a distance of about 230 light years.




Mu is a red giant star with a spectrum of M3 and having a surface temperature of only around 3,500 degrees compared to our Sun which has a temperature of 5,800 degrees.

With a listed magnitude of 2.9 it is the 4th brightest star in Gemini. It varies slightly in brightness between magnitude 2.7 and 3.0 and is classified as an irregular variable star with a period ranging between 72 and 2,000 days.



The Crossley Reflector and Nebula

 

The Crossley Reflector and Nebulae

The 36 inch Crossley Reflector which had been used by Edward Crossly in Halifax, Yorkshire and was at the time the largest reflecting telescope in England was donated in the 1890s to Lick Observatory in California. The night sky conditions over Halifax in the latter of the 19th century were very poor due to the pollution from all the factories in the town.

The Crossley telescope although not able to be used to its fullest in Halifax was a trail blazer in the early part of the 20th century at Lick. It was at he time the largest reflector in America, not being surpassed until 1916 when the 100 inch reflector was introduced at Mount Hamilton.


In 1912 H D Curtiss made descriptions of 132 nebulae that had been photographed by the Crossley telescope. Curtiss describes the importance of photography to astronomers. He says that in catalogues, NGC 83 has thirteen nebulae listed while using the Crossley he saw at least fifty small nebulae and nebulous stars.

Today we know that NGC 83 is an elliptical galaxy in Andromeda but at that time all nebulae were assumed to be in our galaxy.


Later in 1918 Curtiss used the Crossley to study the forms of 50 planetary nebulae on photographs that had been taken with various exposure times in order to get more detail of the structure of the planetary nebulae. The majority showed a more or less regular ring or shell structure.

Tuesday, 1 December 2020

Astrognome 100 Great Stars No 88 Thuban

 

Thuban

Thuban in the constellation of Draco the Dragon which is formed of a curve of stars that twist around the North Star shines with a magnitude of 3.6. It is one of the fainter stars to have a name allocated to it. This is the result of its position in the sky. Around 4,000 years ago when the great pyramids were being built Thuban was the North Star.



The position of the North Star changes due to a wobbling effect on the Earth. The Earth spins on its axis once a day and takes a year to orbit the Sun but as it travels around the Sun it is wobbling very slightly like a spinning top about to stop. However while a spinning top takes only a second to spin once the Earth takes around 26,000 years to wobble once. This is called precession by astronomers.



At the moment Polaris in the constellation of Ursa Minor is the North Star, in 9,000 years time it will be the bright star Vega in Lyra that will be the North Star.

Thuban its name means Serpent lies at a distance of around 300 light years and is an A0 class star which means it is hotter than our Sun. Thuban will be the North Star again around the year 25,300!!

Any Harry Potter fans might recognise Draco as Draco Malfoy one of the characters in the stories. Maybe JK Rowling had an interest in astronomy as a lot of her characters have star names.