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Calendar of astronomy, June sky

Constellation Virgo

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Updated January 21, 2013

In the spring, a triangle formed by the characteristic star Arcturus (α Bootis) of the constellation Bootes, Spica (α Virginis) of the Virgin and Regulus (α Regulus) Leo, help the observer to spot in the night sky. This celestial triangle is called by astronomers the triangle orientation spring. The vast constellation Virgo is easily observable in our northern hemisphere and serves as a marker for the identification of other constellations. It lies between Leo to the west and Libra to the east. To locate the Virgin must seek its main star, Spica. In the Northern Hemisphere, Spica is following the tail of the Great Bear (or the handle of the saucepan), following the great circle arc we arrive to Arcturus in the Bootes and in the continuation is Spica (look on the enlarged image). The Virgin contains a large number of distant galaxies which several are visible in a small telescopes, especially the Sombrero Galaxy. These galaxies are combined in a cluster called the Virgo cluster containing over 3000 galaxies.


nota: A constellation is a group of stars that sufficiently close to the celestial vault are gave the appearance of an imaginary figure drawn in the sky.

nota: By convention, the names of the stars in a constellation are prefixed by a Greek letter followed by the first 3 letters of the constellation, for example:
α  Ori, β Ori,... (Greek letters: α β γ δ ε ζ η θ ι κ λ μ ν ξ ο π ρ ς σ τ υ φ χ ψ ω).

nota: a light year is exactly 9 460 895 288 762 850 meters.

nota: M is the mark of the Messier catalog, a catalog of astronomical objects look like diffuse nebulae or galaxies.

Image: Constellation Virgo. Image reworked from the Open Source software Stellarium.

 Constellation Virgo

Sombrero Galaxy, M104 or NGC 4594


The Sombrero Galaxy M104 or NGC 4594 is located or in the Virgo cluster. This brilliant galaxy Sombrero has an appearance in the shape of hat. We see here, leaning 6 degrees relative to the equatorial plane, indicated by a thick dark band of dust opaque. His disk is 100,000 light years in diameter, such as our Galaxy. In 1914, Vesto Slipher discovered that the spectrum of this galaxy is red shifted and estimates his speed 1000 km/s, much too fast to be a nebula in our Milky Way as we thought then. M104 permitted to discover the existence of systems of stars (galaxies). It was only much later, in 1924, Edwin Hubble proposed the idea of a universe in constant expansion. His observations with the Hooker telescope of 250 cm, confirm that the diffuse objects, as some nebulae are not part of our Galaxy, but in distant galaxies to our own.


nota: M is the mark of the Messier catalog, a catalog of astronomical objects look like diffuse nebulae or galaxies.

nota: NGC (New General Catalogue) is one of the most popular catalogs in the field of astronomy with the Messier catalog.

Image: This image is a composite of three images taken by the camera FORS1 VLT Antu Telescope (European 8.2 m ESO based in Chile). It was obtained after exposure of 6:20, January 30, 2000.

 Sombrero Galaxy, M104 or NGC 4594
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