... Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. 2013 April 16 . Grand Spiral Galaxy M81 and Arp's Loop . ... Studied in the 1960s, Arp's loop has been thought to be a tidal tail , material pulled out of M81 by gravitational interaction with its large neighboring galaxy M82 . But a subsequent investigation demonstrates that at least some of Arp's loop likely lies within our own galaxy . ...

... Credit Copyright: Bernard Miller Explanation: One of the brightest galaxies in planet Earth's sky is similar in size to our Milky Way Galaxy: big, beautiful M81 . ... The deep image of the region reveals details in the bright yellow core, but at the same time follows fainter features along the galaxy's gorgeous blue spiral arms and sweeping dust lanes. It also follows the expansive, arcing feature, known as Arp's loop, that seems to rise from the galaxy's disk at the upper right. ...

... 2000, ApJ, 537, L49 . ... F. Palla . Invited Talk at the IAU Symposium 200 "The formation of binary stars" eds. R.D. Mathieu and H. Zinnecker (ASP Conf. Ser.) in press . Optical follow-up of ROSAT discovered candidate members of the open cluster Coma Berenices . ... 2000, A , in press . ... 2000, ApJ, in press . ... 2000, ApJ, in press (Sept. ... 2000, ApJ Lett., in press . ... Click to examine publications from other years . ... Star Formation Group . ... Arcetri Home Page . ...

In this gallery are many images of Low Surface Brightness Galaxies which have recently been discovered and analyzed. ... The central surface brightness of this galaxy is 24.28 . Malin 2 This galaxy is another huge disk galaxy with a scale length of 15 kpc and a redshift of 15000 km/a. The high surface brightness knot in one of its spiral arms actually has the same color, luminosity and H-alpha equivalent width as the entire Large Magellanic Cloud . ... Truly it is a Low Surface Brightness Galaxy. ...

... Team . ... GRB mini-workshop 2006 . ... On April 8, 2005, an optical afterglow of the GRB 050408 was discovered with the SAO's telescopes (the 1-meter telescope Zeiss and 6-meter telescope BTA) within the framework of a joint BTA request (SAO RAS + IAA CSIC, Granada, Spain) on optical identification of gamma-ray bursts. We first detected a variable object only by our own data in the localization error-box reported by the space observatory HETE and then it was confirmed by our observations in SAO. ...

... Armagh Observatory, College Hill, Armagh BT61 9DG, +44 (0)28 3752 2928 . ... This takes you past the village of Killylea (about 5 miles from Armagh), and then across the River Blackwater past the entrance to the Caledon Estate and into the architecturally attractive village of Caledon, approximately nine miles from Armagh. ... View of the Knockmany Chambered Cairn from the south, showing the modern enclosure. ... In its present state the cairn is an almost circular mound approximately 25m in...

... The double star 54 Leonis, spiral galaxy NGC 3198, and emission nebula NGC 3199 . ... Astronomy for Kids . ... The Horsehead Nebula in Orion . ... Astronomy 101 . ... Astronomy Day . ... NASAт??s Hubble sees a horsehead of a different color . ... Looking like an apparition rising from whitecaps of interstellar foam, the iconic Horsehead Nebula has graced astronomy books ever since its discovery over a century ago. ... Only registered members of Astronomy.com are allowed to comment on this article. ...

... Research . ... The major problem in HVC research is the unknown distance towards most of the HVCs. ... Thilker et al. (2004) used the Green Bank Telescope (GBT) to map an area of $7^{\circ} \times 7^{\circ}$ around M31 in H i . They discovered a population of HVCs located within a projected distance of about $50~\mathrm{kpc}$ from M31. ... 2004). ... The remaining HVCs around M31 are isolated in position and velocity and may represent primordial, dark-matter-dominated clouds. ...