Caldwell 107

NGC 6101

73 light years.
50,000 light years.
Apparent size:
5.0 arc min.


Location maps for the constellation of Apus (above) and C107 (right) created using

Image Details

60 minutes.
Field of View:
77.4 x 51.6 arcmin.
Image date:

A Distant Globular Cluster in Apus

A globular cluster peers eerily from behind thousands of twinkling foreground stars. This is Caldwell 107, one of the most southerly Caldwell objects. At a distance of 50,000 light years, it is also one of the more distant globular clusters orbiting the Milky Way galaxy. It’s brightest stars shine at a feeble fourteenth magnitude.

I’ve imaged quite a few globular clusters and some might say one is much the same as another – but hey, globular clusters have been in the news lately…

Fast Radio Burst Discovery

A few days ago I read about an international study which had discovered a Fast Radio Burst (FRB) emanating from a globular cluster. (It was not the object in my image above). It was an unexpected discovery, because……eerrrm… one expected it.

We still don’t know what causes FRBs. They are rare energetic radio pulses, of extragalactic origin, which last no more than a few milliseconds. Until now, FRBs had always been associated with distant galaxies and never before in a globular cluster.

I was alerted to the new discovery by an excited tweet from a member of the discovery team, Professor Bryan Gaensler, an Australian astronomer based at the University of Toronto:

What made it even more intriguing was that the object in question was not one of the 150 globular clusters which orbit the Milky Way galaxy. It was a globular cluster orbiting the galaxy M81, 12 million light years away!

FRB’s can have been found all over the sky:

NASA’s Goddard Space Flight Center, Public domain, via Wikimedia Commons

Thanks for reading 🙃

Telescope & Imaging Details

Telescope:SkyWatcher Esprit 120 mm apochromatic 3-element refractor; 840 mm f/l @ f/7.
Optics:Field flattener; ZWO Duo-band Hα (656nm) and [OIII] (500nm) filter.
Mount & Guiding:SkyWatcher EQ6-R Pro mount; ZWO ASI120 guide camera.
Imaging camera: ZWO ASI 071 MC Pro (CMOS 28.4mm 16 Mpx).
Software:Control: Cartes du Ciel, ASCOM, EQMOD, PHD2. Imaging: SharpCap, Gimp.
Observatory:34° South.

Images © Roger Powell

I’m one of the founder members of Macarthur Astronomical Society and current webmaster.
Prof. Bryan Gaensler was our Patron for many years.


  1. Aren’t FRBs from something like the magnet on my refrigerator? Only, you know, a bit more powerful.

    I’d read they’d identified them as coming from the arms of spiral galaxies.

    Say, aren’t we in an arm of a spiral galaxy? Maybe my refrigerator magnet is also being registered by the equivalent of a Hubble telescope millions of light-years away.

    Liked by 1 person

    1. Yes, spiral arms of galaxies. That’s what made this discovery stand out. The stars in globular clusters are much older than most stars in the spiral arms, so it’s hard to know what is going on, except magnestism is involved.
      But I don’t blame your fridge.

      Liked by 2 people

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