Thursday, 29 October 2020

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 3rd 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 3rd 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 14th 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.

Wednesday, 28 October 2020

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 18th 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.

Tuesday, 27 October 2020

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.

Monday, 26 October 2020

Comet Klinkerfues seen over Whitehaven

 

Comet Klinkerfues seen over Whitehaven

Comet Klinkerfues 1854 was seen from the Whitehaven Observatory on the night of October 7th 1854. The comet had been discovered by the German astronomer Ernest Klinkerfues on the night of September 12th 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.