Steve Gottlieb
October 6th, 2018, 02:51 AM
Many of the brightest globulars in M31 were discovered by Hubble back in 1932 (http://articles.adsabs.harvard.edu/pdf/1932ApJ....76...44H), but more recent surveys have discovered new outer halo globulars quite a distance out from the galaxy. If you enjoy tracking down these extragalactic globulars, here are a couple of unusual ones...
In 2014, 59 new halo globulars (https://arxiv.org/pdf/1404.5807.pdf) were announced from the Pan-Andromeda Archaeological Survey (PAndAS). Two of the brighter discoveries are PAndAS-53 and PAndAS-54, a globular pair separated by only 2'! Furthermore, this outer halo pair is located a full 7° ESE of the center of M31.
I observed both of these last September using my 24-inch. PAndAS-53 was easily seen (mag 15.5) as a faint, extremely small but non-stellar glow, perhaps 4" diameter. Occasionally a faint stellar nucleus (more obvious with direct vision) was visible. PAndAS-53 is close northwest [25"] of a 12th magnitude star and a distinctive square or diamond asterism [sides 0.8'-0.9'] is close NW.
PAndAS-54 is about a half-magnitude fainter (V~16.0), and just appeared as a very faint "soft" quasi-stellar object, perhaps 3"-4" diameter with a low even surface brightness (no hint of a stellar nucleus). Here are the positions if anyone is interested in tracking these down.
PAndAS-53 01 17 58.4 +39 14 53
PAndAS-54 01 18 00.1 +39 17 00
These two objects are part of an article I recently wrote on Local Group GCs in the current November issue of Sky & Tel ("In Search of Extragalactic Globulars"). It covers GCs in a number of galaxies from the LMC out to the edge of the Local Group (WLM Dwarf).
In 2014, 59 new halo globulars (https://arxiv.org/pdf/1404.5807.pdf) were announced from the Pan-Andromeda Archaeological Survey (PAndAS). Two of the brighter discoveries are PAndAS-53 and PAndAS-54, a globular pair separated by only 2'! Furthermore, this outer halo pair is located a full 7° ESE of the center of M31.
I observed both of these last September using my 24-inch. PAndAS-53 was easily seen (mag 15.5) as a faint, extremely small but non-stellar glow, perhaps 4" diameter. Occasionally a faint stellar nucleus (more obvious with direct vision) was visible. PAndAS-53 is close northwest [25"] of a 12th magnitude star and a distinctive square or diamond asterism [sides 0.8'-0.9'] is close NW.
PAndAS-54 is about a half-magnitude fainter (V~16.0), and just appeared as a very faint "soft" quasi-stellar object, perhaps 3"-4" diameter with a low even surface brightness (no hint of a stellar nucleus). Here are the positions if anyone is interested in tracking these down.
PAndAS-53 01 17 58.4 +39 14 53
PAndAS-54 01 18 00.1 +39 17 00
These two objects are part of an article I recently wrote on Local Group GCs in the current November issue of Sky & Tel ("In Search of Extragalactic Globulars"). It covers GCs in a number of galaxies from the LMC out to the edge of the Local Group (WLM Dwarf).