What is a galaxy?
|Automatic translation||Updated June 01, 2013|
A galaxy is an assembly of stars, interstellar matter and possibly large amounts of dark matter, whose cohesion is ensured by the forces of gravity.
The Milky Way Galaxy or with a capital G, is also the name given to our galaxy is a spiral of stars huge wheel with a diameter of approximately 100 000 light years. What appears from Earth, is a continuous white band of the Milky Way.
Image: Our galaxy is a spiral galaxy like the M83 (NGC 5236) on the image below cons.
Center of the Milky Way
The Milky Way is the central region of our galaxy. Infrared image below shows the cons exact center of our galaxy, known as the Central Molecular Zone and purple, the radio arc of the galactic center.
It can occur at that time, a reaction in which neutral meson decays, produce gamma photons. These photons when they collide with atoms in Earth's atmosphere, producing an avalanche of particles of various kinds are known as cosmic ray showers.
Image: In this picture we see the exact center of our galaxy, known as the Central Molecular Zone and purple, the radio arc of the galactic center. Besides its scientific interest, this image won first prize in the photographic AUI / NRAO in 2008. Credit: A. Ginsburg (U. Colorado - Boulder) et al. SPMO team, team GLIMPSE II.
Infrared image of our Galaxy
This color infrared composite image from the center of the Milky Way reveals a new population of massive stars and new details in the complex structures in the hot ionized gas that swirls over a distance of 300 light years. This broad view is the clearest picture taken in infrared light on the galactic nucleus. It is a laboratory for understanding how massive stars shape and influence the environment of the nuclear regions, often violent, other galaxies. This image combines the NICMOS imaging (Hubble Space Telescope's Near Infrared Camera and Multi-Object Spectrometer) imaging with IRAC (Spitzer Space Telescope Infrared Camera). The galactic nucleus is obscured in the spectrum of visible light, but infrared light penetrates dust. NICMOS shows a large number of massive stars spread throughout the region. This view allows astronomers to see that massive stars are not confined to the three known groups of massive stars in the Galactic center (the core, the Arches cluster and the cluster of Quintuplet). In the NICMOS image, these three groups are seen as tight concentrations of massive stars.
The stars were scattered or formed individually or originate in clusters that have been disturbed by strong gravitational tidal forces. Winds and radiation from these stars form the complex structures observed in the nucleus, which in some cases, may trigger new generations of stars.
Image: Infrared view of the center of our Galaxy. The NICMOS mosaic was made from pictures of 2304 which required 144 rotations of the Hubble telescope around its orbit, between February 22 and June 5, 2008. Image Credits: Hubble: NASA, ESA, and QD Wang (University of Massachusetts, Amherst); Spitzer: NASA, Jet Propulsion Laboratory, and S. Stolovy (Spitzer Science Center / Caltech).NB: The Hubble Space Telescope (Hubble Space Telescope or HST) is in orbit 560 kilometers above sea level, it performs a full rotation of the Earth every 100 minutes.
Dust in the Milky Way
Intertwined structures visible from the cold dust in our galaxy have been resolved on this image, infrared with a fineness of detail never reached by the European satellite Planck.
Image: In this picture, we see the details of the cold dust in our galaxy, the Milky Way.