A new catalogue of the visible part of the northern part of the Milky Way galaxy has been assembled and it includes no fewer than 219 million stars. Geert Barentsen of the University of Hertfordshire in the UK led the team who assembled the catalogue in a ten year program using the Isaac Newton Telescope on La Palma in the Canary Islands.
Because we live within the Milky Way Galaxy, it is impossible for us to take a picture of its spiral structure from the outside. But we do know that our Milky Way has a spiral nature from observations made from within our Galaxy. This image of the real Milky Way was taken by the COBE satellite. The disk and center region of our Galaxy are readily recognizable. This image makes the Milky Way appear much more galaxy-like and less like the smudge of stars we see stretching across our night sky. (Image Credit: The COBE Project, DIRBE, NASA)
From dark sky sites on Earth, the Milky Way appears as a glowing band stretching across the sky. To astronomers, it is a disk stretching across 100,000 light years seen edge on from our vantage point. The disk contains the majority of the stars in the galaxy, including the Sun, and the densest concentrations of dust and gas.
The unaided human eye struggles to distinguish individual objects in this crowded region of the sky, but the 2.5 meter mirror of the INT enabled the scientists to resolve and chart 219 million separate stars. The INT program charted all the stars brighter than 20th magnitude, or 1 million times fainter than can be seen with the human eye.
Using the catalogue, the scientists have put together an extraordinarily detailed map of the disk of the Galaxy that shows how the density of stars varies, giving them a new and vivid insight into the structure of this vast system of stars, gas and dust.
The production of the catalogue, IPHAS DR2 (the second data release from the survey program The INT Photometric H-alpha Survey of the Northern Galactic Plane, IPHAS), is an example of modern astronomy’s exploitation of “Big Data.” It contains information on 219 million detected objects, each of which is summarized in 99 different attributes.
With this catalogue release, the team are offering the world community free access to measurements taken through two broad band filters capturing light at the red end of the visible spectrum, and in a narrow band capturing the brightest hydrogen emission line, H-alpha. The inclusion of H-alpha also enables exquisite imaging of the nebulae found in greatest number within the disk of the Milky Way.
The Isaac Newton Group of Telescopes consists of the 4.2 meter William Herschel Telescope and the 2.5 meter Isaac Newton Telescope. The facility is owned by the Science and Technology Facilities Council (STFC) of the United Kingdom, and it is operated jointly with the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) of the Netherlands and the Instituto de Astrofisica de Canarias (IAC) of Spain. The telescopes are located in the Spanish Observatorio del Roque de los Muchachos on La Palma, Canary Islands, which is operated by the IAC.
For more information:
http://www.ras.org.uk/news-and-press/2507-219-million-stars