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2010 September 16 00:27 SAST

A team of astronomers from Australia, the UK, the USA and France have discovered the first planetary nebula known to be associated with a galactic open cluster.
The nebula, designated PHR 1315-6555, is associated with the dim cluster Andrews-Lindsay 1 (Cl VDBH 144, ESO 96-4) in Musca.
According to the authors it is "currently the only known 'confirmed' example of a PN physically associated with a Galactic open cluster."
The announcement appears in the August 2010 edition of the AAO Observer, the newsletter of the Australian Astronomical Observatory.
The authors write: "The PN was found during systematic searches for new Galactic PNe for the original MASH survey ... on the AAO/UKST Ha survey ... The PN had been missed in earlier broadband surveys, including CCD studies of the host cluster ... Here we present original discovery images and CTIO 4m MOSAIC-II camera follow-up narrow-band images that reveal its bipolar morphology. We also present confirmatory spectroscopy and provide preliminary estimates of basic PN properties and abundance estimates from deeper spectra that show it to be of Type I chemistry consistent with that of the cluster and its estimated turn-off mass."

The nebula is about 16,000 years old and spans some 0.4 parsecs. On the sky it measures 18 x 14 arcseconds and lies just north-east of the central region of the cluster.
The cluster AL1 was discovered on photographic plates exposed at Boyden Observatory (Bloemfontein, South Africa) with the ADH telescope. In the discovery paper it is described as being 75 arcsec across, circular, and comprised of faint stars.
The accompanying star chart, adapted from Millenium Star Atlas chart 1001, shows the approximate position of the cluster as a red rhombus. The brightest star at top-right is theta Muscae.
Parker, Q.A. (et al.) PHR1315-6555: a bipolar Type I planetary nebula (PN) in the compact Hyades-age open cluster ESO 96-SC04. AAO Observer, 118, August 2010