A Globular Cluster in Saggita
Sagitta is the third smallest of the eighty-eight constellations, with just eighty square degrees of sky – and M71 is its only notable deep sky object. While it is listed as one of the closest globular clusters which orbit the Milky Way at a mere 13,000 light years, it is not one of the brightest. It checks in at only magnitude +8 and appears relatively small.
It certainly is small and its apparent diameter of only 3.3 arc-minutes indicates a true diameter of only about 12 light years, very small for a globular cluster.
Exposure: 30 minutes.
Field of view: 48 x 48 arcmin
I thought I would mention some news from the guest speaker we had at MAS last Monday night, Dr Emil Lenc. He is a radio astronomer here in Sydney with the Australian National Science Agency (CSIRO), where he is a Senior Research Scientist. He has the skill and good fortune to be working on the spanking new ASKAP radio telescope 36 dish array located in Western Australia, as it transitions from the commissioning phase into full science operations.
ASKAP has the capacity to simultaneously cover large areas of the sky using wide field cameras in a wide field dish array.
After giving us an insiders perspective of the ASKAP Telescope operations, Emil recounted two exciting new classes of object which the ASKAP science team has recently discovered.
Did you read that correctly? Not two new ‘objects‘ discovered; but two new ‘classes of object‘ – and right now no-one knows what they are!
Odd Radio Circles
So far at least five ORCs have been discovered. These are huge circular objects, about 1 arc-minute in diameter and have been detected only in the radio spectrum. Some of them have galaxies located in the centre (so they may be quite remote) but a robust theory of how these mysterious new objects were formed has not yet been proposed.
You can read a scientific paper about the ORC discovery here. or if you are really interested you can watch this YouTube video from the paper’s lead author, Prof. Ray Norris (WSU). (it’s a 41 minute video which I have set to begin at 2 minutes. Just watch to about 11 minutes).🙂
In another fantastic discovery for ASKAP, they conducted multiple ten-hour observations across a 30° field, searching for new radio variables on timescales of hours. They anticipated they might observe something new but didn’t really know what to expect. The speculation paid off. They found multiple rapid scintillators or intra-day variables (IDV).
Then they found more.
They discovered six unusual linear scintillating arrangements on the radio sky with angular widths ∼1 arcmin and length ∼2°. Two of them are extreme intra-hour variables with timescales as short as tens of minutes.
Again, there is no explanation** for the objects, other than that it appears that they are distant background radio signals caused to scintillate by an otherwise invisible foreground filament of gas or dust.
** No, it is not @#$%^&* aliens!
Thanks for reading 🙃
Cosmic Focus Observatory
Above us only sky….
|Telescope:||SkyWatcher Esprit 120 mm apochromatic 3-element refractor; 840 mm f/l @ f/7.|
|Optics:||Field flattener; ZWO duo narrowband Ha + [OIII] filter.|
|Mount:||SkyWatcher EQ6-R Pro mount.|
|Imaging camera:||ZWO ASI 071 MC cooled.|
Images © Roger Powell
I’m one of the founder members of Macarthur Astronomical Society and current webmaster.