NGC 6487 in Hercules

July 2021 - Galaxy of the Month

This interactive image of the NGC 6487 and was provided by the Pan-STARRS1 Surveys using Aladin Sky Atlas. We also have a finder chart should help you locate these galaxies, as will this link for NGC 6487 on the Stellarium Web planetarium.

Following on from the June GOM, July is also a poor month for galaxy observing from the UK with summer twilight in full swing. My choice this month is the galaxy NGC 6487 in Hercules as it will hopefully be in the darker part of the sky.

Both NGC 6487 and its fainter companion NGC 6486 were discovered by Edouard Stephan using the 31” (80cm) silver on glass reflector at Marseilles. NGC 6487 was discovered in 1871 and NGC 6486 6 years later in 1877.

I find it interesting coming from the UK that the 31” was mounted outside without any form of cover, building wise anyway. Just shows the quality of the weather in Marseilles. This was one of the first large silver on glass reflectors made by Foucault.

Both the galaxies are elliptical with the classifications just showing a generic E so they have not had more detailed classifications done on them. NGC 6487 would appear to be a head-tail radio source which suggests an AGN of some form, at least in the past. The two galaxies appear to be part of the poor galaxy group WBL 648. The group contains only three galaxies and includes the face on spiral UGC 11017 as part of the trio with NGC 6486 and 6487. NGC 6487 does show a bright core in the UV which suggests some form of activity. UGC 11017 does show a lot of activity in the UV suggesting lots of star formation going on. Otherwise, perhaps not unsurprisingly, there is not much research done on these galaxies. So many galaxies so little time 😊 The group is at a distance of about 120 Mpc so quite a distance out.

All the galaxies in the group are very close together so using a high-power eyepiece, perhaps of the order of 340x if your telescope will take it, will help when trying to split it. I suspect that NGC 6487 may not be that hard to see but at 15th magnitude NGC 6486 is going to be much more difficult to see, especially in the summer twilight. The other galaxy in the trio, UGC 11017, is nearer to 16th magnitude and close to face on so it is going to be a challenge I think for all but the largest telescopes, and even then only the core will be seen. Perhaps not unsurprisingly the pair does not make the Night Sky Observer's Guide (NSOG) or other standard observing guides.

Owen Brazell - Galaxy Section Director