Football Shaped Dark Halos and Spiral Structure

The central bars in spiral galaxies are known to be very efficient mechanisms for driving spiral structure, much like a rotating rod of steel in water. If indeed more conspicuous (stronger) spirals are driven by more conspicuous (stronger) bars, the intriguing question arises as to what drives a spiral arm pattern in a galaxy without a central oval or elongated bar. Admittedly these situations are not that common, but such galaxies certainly do exist the beautiful spiral NGC 2997 discussed in...

Info

Prior to the dawning of the photographic era, astute and careful observers produced some of the most exquisite drawings of objects in our night sky, by eye and by hand. One of our favorite drawings of the Milky Way Galaxy comes from the work of the French born artist and amateur astronomer Etienne Leopold Trouvelot (1827-1895), who emigrated from France to the United States in 1855. In 1882, Trouvelot clearly stated his intentions in a volume entitled The Trouvelot Astronomical Drawing Manual...

Juvat ire jugis qua nulla priorum Castaliam molli devertitur orbita clivo

The lines are from Virgil, and freely translated read as follows Joyous it is to cross mountain ridges where there are no wheels ruts of earlier comers, and follow the gentle slope to Castalia. Niepce-Daguerre and Talbot had indeed walked along roads where no wheels before had gone, using entirely different methods. To Talbot belongs the distinction of being the first person to publish a workable photographic system which could be adopted worldwide. One of Talbot's early photographs is...

E7

We followed some intriguing historical leads, by traveling to the United States and to the United Kingdom, and our findings below are based on our detailed readings of archival material at the Lowell Observatory in Arizona and the Royal Astronomical Society's archives at Burlington House in London. The history of the International Astronomical Union's Commission on Nebulae and Star Clusters (Commission Number 28) spanning the period 1922-1925 is particularly rich and archival material is on...

Grand Puzzle What Triggers the Formation of Stars

Star formation is a very important part of modern astrophysics. One of the great quests is to understand how the rate of star formation in the Universe has changed from the very early Universe to the present epoch. This is still a controversial subject. It does seem clear that the rate at which stars formed in the Universe was much higher 6-8 billion years ago, mostly in the more massive galaxies, than it is now. Just how large the star formation rate was at even earlier times is still...

Act 2611

Cover Photo Figure 202 secured with the Hubble Space Telescope, courtesy NASA, ESA, Natan Smith at the University of California, Berkeley, and his collaborators, together with the Hubble Heritage Team at the space Telescope Science Institute, Baltimore. ISBN 978-0-387-78974-3 e-ISBN 978-0-387-78975-0 Library of Congress Control Number 2008931168 2008 Springer Science+Business Media, LLC All rights reserved. This work may not be translated or copied in whole or in part without the written...

Drawing in the dark at Birr Castle

Exactly what sort of illumination did Lord Rosse use, to make his exquisite drawings of the nebulae The crucial point is that, in order to see a galaxy through the eyepiece of Lord Rosse's giant telescope (whose speculum mirror weighed over 3 tons), the eye of the observer first has to be dark adapted. In simple terms, the retina contains two types of receptors rods and cones. There are approximately 120 million rods compared with 6-7 million cones. Our daylight vision (cone vision) readily...