Diagram showing the spectral class and luminosity of stars
Diagram showing the spectral class and luminosity of stars. The diagram was named The Hertzsprung-Russell Diagram, or the H-R diagram for short. At the beginning of the 20th century two astronomers found that if stars were plotted on a diagram with their luminosity (brightness) on one axis, and their spectral class on the other, that stars formed three distinct groups. The largest group, the Main Sequence Stars, is where 90% of the stars are found. These stars are fusing hydrogen into helium in their cores. This group propagates diagonally from the upper left corner, down to the right corner. The group below the main sequence is the White Dwarfs, which is a group of small, earth-sized stellar remnants. The third group, which is found above the main sequence is that of the giants.
Stars appear on a specific place on the main sequence depending on their mass and age. The mass determines when it will leave the main sequence.The H-R diagram is a significant tool for astronomers, when it comes to understanding stellar evolution.
© Fahad Sulehria/Stocktrek Images
Aucklands advance from its battalion headquarters
This drawing relates to an incident on the 14th/15th September 1916 and is described in a book entitled 'A Saga of the Sword' by Austin F. Britten, published by Arrowsmith, London 1928. The chapter, entitled 'The End of an Epoch', contains the following map reference : S11 b4.9. This is right in the middle of the area of the 2nd Battalion Auckland Regiment which was in No-Man's Land, just a shade short by 50 yards or so of the German Front Line in Coffee Lane. And, no doubt, Matania is attempting to portray an incident in the initial phase of the Auckland's advance from its battalion headquarters, slightly on the right of the fork (La Forche) which is where the New Zealand memorial now stands. It would also appear that four tanks were allocated to the New Zealand Division and all four passed this way towards the fork before spreading out. They were from D Company and were numbered D8, D10, D11 and D12. The actual image was never used in the book (which in the end did not have any illustrations) but no doubt Matania was asked by Austin Britten to produce this incident at the above map reference. The name of the book was written on the back of the picture. Fortunino Matania, Ri (1881-1963). One of the most accomplished realistic illustrators and artists of his time, his wartime work was immensely popular and appeared in nearly every major news magazine, Allied, Neutral and Central Powers alike. Date: 1916
© David Cohen Fine Art/Mary Evans Picture Library
An eclipse is seen in Tokyo
An eclipse (clockwise from top L) is seen in Tokyo May 21, 2012 in this combination picture. The sun and moon aligned over the earth in a rare astronomical event - an annular eclipse that dimmed the skies over parts of Asia and North America, briefly turning the sun into a blazing ring of fire. REUTERS/Kim Kyung-Hoon (JAPAN - Tags: ENVIRONMENT TPX IMAGES OF THE DAY)