Explanation: What celestial body wears the Necklace Nebula? First, analyses indicate that the Necklace is a planetary nebula, a gas cloud emitted by a star toward the end of its life. Also, what appears to be diamonds in the Necklace are actually bright knots of glowing gas. In the center of the Necklace Nebula are likely two stars orbiting so close together that they share a common atmosphere and appear as one in the featured image by the Hubble Space Telescope. The red-glowing gas clouds on the upper left and lower right are the results of jets from the center. Exactly when and how the bright jets formed remains a topic of research. The Necklace Nebula is only about 5,000 years old, spans about 5 light years, and can best be found with a large telescope toward the direction of the constellation of the Arrow (Sagitta).

Joli :-)

Dans le modèle standard de la cosmologie, la matière visible (classique) ne compte que pour environ 5% de la masse de l’Univers. Et pourtant, une partie de cette matière continue d’échapper aux astrophysiciens. En effet, la moitié de ces 5% reste invisible pour nos instruments de détection. Une hypothèse avance que cette matière manquante se trouverait au sein d’immenses nuages de gaz froid. Et grâce à une méthode de détection indirecte développée par une étudiante de l’université de Sydney, les astrophysiciens pourraient bien avoir trouvé la trace de ces nuages jusqu’alors demeurés invisibles.

Joli :-)

Have you ever seen a halo around the Moon? This fairly common sight occurs when high thin clouds containing millions of tiny ice crystals cover much of the sky. Each ice crystal acts like a miniature lens. Because most of the crystals have a similar elongated hexagonal shape, light entering one crystal face and exiting through the opposing face refracts 22 degrees, which corresponds to the radius of the Moon Halo. A similar Sun Halo may be visible during the day. Exactly how ice-crystals form in clouds remains a topic of research. In the featured image taken last week from Östersund, Sweden, a complete lunar halo was captured over snowy trees and rabbit tracks.

Si le crépuscule désigne indifféremment le coucher ou le lever du Soleil, l’aube désigne uniquement le moment où le ciel commence à s’éclaircir avant le lever du Soleil. L’aube s’achève avec l’aurore, le moment où le bord du disque solaire apparaît à l’horizon, qui prend alors une teinte jaune-orangé.

L’aube est divisée en trois phases, en fonction de la position du Soleil sous l’horizon : à 18°, l’aube astronomique, pas encore perceptible à l’œil nu, mais les étoiles de faible magnitude disparaissent, à 12°, l’aube nautique et à 6°, l’aube civile, l’ensemble des activités humaines peut se dérouler sans éclairage artificiel.

How far do magnetic fields extend up and out of spiral galaxies? For decades astronomers knew only that some spiral galaxies had magnetic fields. However, after NRAO's Very Large Array (VLA) radio telescope (popularized in the movie Contact) was upgraded in 2011, it was unexpectedly discovered that these fields could extend vertically away from the disk by several thousand light-years. The featured image of edge-on spiral galaxy NGC 5775, observed in the CHANG-ES (Continuum Halos in Nearby Galaxies) survey, also reveals spurs of magnetic field lines that may be common in spirals. Analogous to iron filings around a bar magnet, radiation from electrons trace galactic magnetic field lines by spiraling around these lines at almost the speed of light. The filaments in this image are constructed from those tracks in VLA data. The visible light image, constructed from Hubble Space Telescope data, shows pink gaseous regions where stars are born. It seems that winds from these regions help form the magnificently extended galactic magnetic fields.