Observing Alert: Z Canis Major In Outburst

by Tammy Plotner on February 4, 2011

Z Canis Major - Credit: Palomar Observatory, courtesy of Caltech

Heads up, weekend warriors! With very little Moon to contend with, it would be a great time to observe the bright outburst of the pre-main sequence variable star, Z Canis Major. It has gained more than two magnitudes and is well within binocular and small telescope range.

From the AAVSO Special Notice compiled by Elizabeth O. Waagen: “John Bortle, Stormville, NY, reports that the pre-main sequence binary variable Z CMa is in outburst, according to his observation of 2011 February 4.0 UT at visual magnitude 8.5. Observations in the AAVSO International Database confirm this outburst, which may have begun as long ago as April 2010, when it began brightening slightly from visual magnitude 10.7. When Z CMa emerged from its seasonal gap in November 2010, it was already 9th magnitude.

Locator Chart Courtesy of AAVSO

The current outburst is as bright as the one that occurred in 2008, the brightest in the star’s known history. Z CMa is a very interesting object, a binary composed of a Herbig Be star and an FU Ori star. The Herbig star is embedded in nebulosity. The system is an x-ray source and has an x-ray jet. According to Stelzer et al. (2009, Astronomy & Astrophysics v.499, p.529, and astro-ph arXiv:0903.4060), the FU Ori star is the source of both the optical outbursts and the x-ray emission. Observations of Z CMa (RA 07:03:43.16 Dec -11:33:06.2) are strongly encouraged, both during the current outburst and throughout the observing season. With its range of visual magnitude ~8.0 – 10.5, it is an excellent visual observing target.”

Our thanks to John Bortle and the American Association of Variable Star Observers (AAVSO) for drawing our attention to the current outburst of this interesting system!


Tammy is a professional astronomy author, President Emeritus of Warren Rupp Observatory and retired Astronomical League Executive Secretary. She’s received a vast number of astronomy achievement and observing awards, including the Great Lakes Astronomy Achievement Award, RG Wright Service Award and the first woman astronomer to achieve Comet Hunter's Gold Status.

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