An isolated neutron star discovered in the Small Magellanic Cloud

The supernova remnants 1E 0102.2-7219
The supernova remnants 1E 0102.2-7219

An article published in the journal “Nature Astronomy” describes the study of the supernova remnants identified as 1E 0102.2-7219 in the Small Magellanic Cloud. A team of researchers led by Frédéric Vogt used the MUSE instrument installed on ESO’s VLT to observe a large ring of gas in that system that is slowly expanding into the depths of several other gas filaments that are quickly moving away, leaving behind a neutron star in the center.

The Small Magellanic Cloud is one of the satellite dwarf galaxies of the Milky Way and is about 200,000 light years from Earth. Years ago an X-ray source was discovered within it and simply labeled as p1 but the researchers couldn’t establish its nature. The presence of supernova remnants was recognized but it wasn’t clear whether they were inside them or behind them.

The MUSE (Multi Unit Spectroscopic Explorer) instrument installed on ESO’ VLT (Very Large Telescope) in Chile came into operation in 2014 and was upgraded in 2017 to enable 3D images of the observed objects to be obtained. Its use revealed the presence of a large gas ring in the 1E 0102.2-7219 system.

The researchers led by ESO fellow Frédéric Vogt realized that the ring coincided perfectly with the source p1 discovered years ago. This indicated that p1 was inside the supernova remnants. At that point, the researchers used data from the archive of observations made with NASA’s Chandra X-ray observatory to establish that it was an isolated neutron star with a low magnetic field.

The neutron star is what remained after the supernova, a sphere with a diameter of about 10 kilometers but with a mass greater than the Sun’s. These strange objects may have extremely powerful magnetic fields but the ones with low magnetic fields should be common. The problem is to detect them because they shine only at X-rays. The confirmation that p1 is an object of that type arrived thanks to observations at optical frequencies.

The image (ESO/NASA, ESA and the Hubble Heritage Team (STScI/AURA)/F. Vogt et al.) Is a composition that combines observations made with different telescopes. The reddish background comes from the Hubble Space Telescope and reveals the puffs of gas that form the supernova remnants 1E 0102.2-7219 in green. The red object with a dark center comes from the MUSE instrument and the blue and purple components come from the Chandra space observatory. The blue spot at the center of the red ring is the neutron star.

Liz Bartlett, another author of the article and also an ESO fellow in Chile, pointed out that the discovered object is the first to be confirmed beyond the Milky Way, a result that’s possible thanks to the use of MUSE. According to the researcher this can open new possibilities of discovery and study for these star remnants. Basically, the p1 source was under observation but they needed the help of a new instrument to establish its nature and allow a good step forward in research.

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