April 2025 - Picture of the Month
Supernova remnant ESO 217-25 in Centaurus
I've chosen a supernova remnant (SNR) in the southern constellation of Centaurus this April. I think that this is a fascinating structure, and Martin's done well to catch so much detail. There are relatively few images of it around.
It's also an elusive target that isn't easy to tease out of many catalogue searches. As far as I can tell, ESO 217-25 designation is mainly used in amateur circles, alongside others like the Mermaid nebula or the Betta Fish nebula, whilst the designation of G296.5+10 more common for professional astronomers, with whom it also goes by PKS 1209-51/52.
Either way, there's been some recent research interest in this object that sits roughly halfway between δ Cen and ρ Cen. This image appears to show the northern half of the SNR. The whole SNR is axially symmetric in the radio band and contains a compact X-ray source within it's bounds, which is probably a neutron star formed in the supernova event.
The SNR and the neutron star lie around 14 kpc (4500 light-years) from us on the Carina Arm of the Milky Way. It's estimated to be about 14,000 years old given its mean diameter of 31 pc (101 light-years).
ESO 217-25 is a large object, at least in the radio it's 90'×65', but I couldn't find a good visual estimate as I'd guess it's not easy to see. The Digitized Sky Survey (DSS) shows it as barely a shadow, but based on that I'd estimate that this image has a width of about 26 arc-minutes.
James Whinfrey - Website Administrator.
