Size Gallery

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

Market Reports - English Country Squire carves the beef

Market Reports illustrated (Postcard series):
MEAT: "English beef was in fine condition."
This report on English beef (as a commodity traded on the Stock Exchange) is illustrated by a ruddy and rotund Eglish Country Squire taking great delight in the serving of probably the largest joint of beef you can imagine! Thankfully it does not appear it is all destined for his luncheon as there are other plates to be filled...!
1903

© Mary Evans Picture Library 2015 - https://copyrighthub.org/s0/hub1/creation/maryevans/MaryEvansPictureID/10546905

Millau viaduct spanning the Tarn Gorge, southern France

MAB-72
Millau viaduct spanning the Tarn Gorge, southern France
At 336 metres the cable-stayed Viaduc de Millau is the highest bridge in the world and 2.5 kms long. Designed by British architect Sir Norman Foster the viaduct is higher than the Eiffel Tower. Costing 400 millions euros it was completed in December 2004 in 39 months.
Mark Boulton
Please note that prints are for personal display purposes only and may not be reproduced in any way

© Mark Boulton/ardea.com