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HIGHLIGHTS by Tony Flanders
Bright Nova in Delphinus
|Update: Nova Delphini 2013 was discovered on August 14th, peaked two days later at magnitude 4.4, and by November 10th was down to magnitude 11.2. It has been quite red. See this preliminary light curve from the AAVSO.|
Use the chart at right, or download this printable, full-page chart, which is a slightly modified version of page 64 from Sky & Telescope's Pocket Sky Atlas.
Here's a 10°-wide comparison-star chart from the American Association of Variable Star Observers (AAVSO). The nova is the cross at center. As the nova dims, make an appropriate new chart with the comparison-chart maker starting on the a href="http://www.aavso.org/" target="new_window">AAVSO home page. The AAVSO's comparison-star magnitudes are the ones to use, so that everyone's estimates will be made consistently.
The nova was discovered by Koichi Itagaki of Yamagata, Japan, in an image taken at 14hh Universal Time (2 p.m. EDT) on August 14th. It was not present in a photo that he took the previous day. Here is the announcement from the IAU's Central Bureau for Astronomical Telegrams. The star was apparently 17th magnitude before erupting, so it brightened roughly 100,000-fold to its peak on August 16th.
A classical nova happens in a special kind of tightly-orbiting binary star system: one where a relatively normal star pours a stream of hydrogen onto the surface of a companion white dwarf. When the layer of fresh hydrogen on the white dwarf's surface grows thick and dense enough, the bottom of the layer explodes in a runaway hydrogen-fusion reaction — a hydrogen bomb in the shape of a thin shell roughly the size of Earth. The underlying white dwarf remains intact, and as new hydrogen builds up, the process may repeat in a few years to tens of thousands of years.
Posted by Tony Flanders, August 14, 2013