I can see your halo, halo, halo (part II)
(I previously wrote an unrelated Picture Story with the same title here: https://www.nature.com/articles/s41550-017-0072, hence the 'part II'!)
Recently we published a paper by Frédéric Vogt and collaborators which had its observations turned into a Photo Release by the European Southern Observatory. The image above represents a nice bit of detective work that identified the neutron star remnant of a supernova explosion which occurred in the Small Magellanic Cloud some 2,000 years ago. It is a combination of data obtained with three different telescopes:
- The background image, together with the greenish wisps of gas that make up part of the supernova remnant, was obtained with the Hubble Space Telescope;
- The emission shown in purple and blue is due to X-rays, and was observed by the Chandra X-ray Observatory;
- The red ring surrounding the blue dot near the centre of the image was provided by the MUSE integral field spectrograph instrument on the Very Large Telescope.
This latter feature was key to the neutron star hunt. The ring is due to emission from neon and oxygen ions, and it perfectly circled what was previously an uninteresting X-ray source. However, now that this X-ray source had a target painted around it, Vogt et al. realised that it must be the high-density remnant from the supernova explosion, an isolated neutron star. Such objects are typically very hard to find, because they only shine at X-ray wavelengths. Indeed, this was the first (non-pulsar) neutron star to be found outside our Galaxy — they should be common. This supernova remnant, 1E 0102.2-7219, now joins the ranks of the well-known Galactic supernova remnants, Cassiopeia A and Puppis A, as remnants with an identified Central Compact Object.