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The study of galaxies

A galaxy is a massive, gravitationally bound system consisting of stars, gas and dust (that make up the interstellar medium), and a dynamically important but poorly understood component commonly called dark matter. The word galaxy is derived from the Greek galaxias (γαλαξίας), literally "milky", a reference to the Milky Way galaxy. Galaxies range from dwarfs with as few as ten million stars to giants with a hundred trillion stars, each orbiting the centre of mass of their host galaxy.

Galaxies vary in their relative amounts of stars and interstellar medium but the mass of most galaxies is dominated by dark matter, 90% being typical. It is now thought that most, if not all, galaxies contain a super-massive black hole at their centre.

As far as their optical appearance goes, galaxies have historically been classified into one of three broad classes. Elliptical galaxies have a smooth, elliptical light distribution that shows little or no detail and are characterised by having relatively little interstellar medium. Spiral galaxies are flattened disk-like systems showing beautiful, curving spiral arms, and have much more interstellar medium than the ellipticals. The third class is the irregular galaxies, generally less massive than either the ellipticals or spirals, and having an amorphous appearance. These galaxies are normally very rich in interstellar medium.

Galaxies sometimes collide and interact with each other and this can both induce very rapid bursts of star formation and transform galaxies from one type into another. Mergers of galaxies in the distant past are thought to have been fundamental in shaping their present-day appearance.

Most galaxies are 1,000 to 100,000 parsecs in diameter and usually separated by distances on the order of millions of parsecs (or megaparsecs). Intergalactic space is filled with a tenuous gas of an average density less than one atom per cubic meter. The majority of galaxies are organized into a hierarchy of associations known as groups and clusters, which, in turn usually form larger superclusters. At the largest scale, these associations are generally arranged into sheets and filaments, which are surrounded by immense voids.

INAF hosts the preliminary round to set up the Cherenkov Telescope Array Observatory-ERIC

Feb 14, 2018

INAF hosts the preliminary round to set up  the Cherenkov Telescope Array Observatory-ERIC At Headquarters of the Italian National Institute for Astrophysics INAF, the kick-off round of the multilateral negotiations to establish an ERIC organization to the manage the Cherenkov Telescope Array project as part of the EU’s ESFRI infrastructure roadmap had take place

Extrasolar planets: Italy to lead the construction of the SHARK instruments on the LBT

Jan 24, 2018

Extrasolar planets: Italy to lead the construction of the SHARK instruments on the LBT The Italian institutes involved in the construction of SHARK are the INAF Observatories of Padua and Rome, responsible for the two channels, together with the Observatories of Arcetri, Milan and Trieste and the Department of Physics and Astronomy of the University of Padua

INAF researcher wins a Consolidator Grant 2017

Dec 20, 2017

INAF researcher wins a Consolidator Grant 2017 Two black hole systems are the investigational topic of DEMOBLACK: one of the projects that have been granted the European Consolidator Grant, which was submitted by Michela Mapelli, a researcher of the National Institute for Astrophysics-INAF and Professor at the University of Innsbruck in Austria