Friday, August 23, 2013

A Spectrum of Nova Delphini

When a new star appeared in the constellation Delphinus late last week,astronomers found its spectrum hinted at the apparition's true nature. Now known as Nova Delphini, its visible light spectrumnear maximum brightness is centered in this image of the nearby star field captured withprism and telescope on the night of August 16/17 at the Sternwarte B├╝lach, Switzerland. Strong absorption lines due to hydrogen atoms are seen as the darkest bands in the nova's spectrum, but the strong absorption lines are bordered along their redward edge by bright bands of emission. That pattern is the spectral signature of material blasted from a catalysmic binary system known as a classical nova. Other stars in field are fainter, identified by theirHipparcus catalog numbers, brightness inmagnitudes, and spectral types. By chance, the faint emission line from planetary nebula NGC 6905 was also included, indicated at the lower right.

Wednesday, August 21, 2013

Hubble Peers at a Cosmic Optical Illusion

At first glance, this Hubble picture appears to capture two space giants entangled in a fierce celestial battle, with two galaxies entwined and merging to form one. But this shows just how easy it is to misinterpret the jumble of sparkling stars and get the wrong impression — as it’s all down to a trick of perspective. 

By chance, these galaxies appear to be aligned from our point of view. In the foreground, the irregular dwarf galaxy PGC 16389 — seen here as a cloud of stars — covers its neighboring galaxy APMBGC 252+125-117, which appears edge-on as a streak. This wide-field image also captures many other more distant galaxies, including a quite prominent face-on spiral towards the right of the picture. 

Credit: ESA/Hubble and NASA, Acknowledgement: Luca Limatola Mission: Hubble