The James Webb Space Telescope’s latest images are the most “cerebral” yet, capturing a dying star’s nebula that looks eerily like a brain inside a transparent skull.
Located around 5000 light years away in the constellation Vela, the sails, the fog is officially called PMR 1. It is named after the astronomers who discovered it – Parker, Morgan and Russell – while conducting a survey with the British 1.2m Schmidt Telescope at the Australian Astronomical Observatory in the late 1990s. When Spitzer Space Telescope observed PMR 1 in infrared light in 2013, the nebula’s appearance led to its unofficial nickname “Exposed Cranium Nebula”.
The outer shell is thought to have been ejected by the star at the center of the nebula first, and that shell has cooled considerably compared to the complex mixture of various ionized gases in the interior that was ejected later.
A strange split in the middle of the fog looks like it divides the brain into left and right lobes. This split could have been blown by polar jets from the dying star. This hypothesis is supported in the MIRI image where the ionized gas can be seen spewing out through the hydrogen envelope at the top of the image. If the splitting was produced by a jet, it gives some indication of the direction of the star relative to the nebula.
The big question, however, is the nature of the central, dying star. When it was discovered in the 1990s, the nebula’s emission features looked like they belonged to a Wolf-Rayet star, which is one of the more extreme breeds of massive star. Wolf-Rayet stars are so unstable that they emit mass at an enormous rate, blown away by a radiation wind many times stronger than sun‘s solar wind. This ejected matter then forms a Wolf-Rayet nebula before the star itself eventually explodes as one supernova.
However, the presence of a Wolf-Rayet star inside PMR 1, or indeed inside its cousin PMR 2 which was discovered at the same time, has yet to be confirmed.
This leaves the door open to the possibility that the exposed skull is actually just an ordinary planetary nebula produced by a less massive Sun-like star that has expanded into its red giant phase and now sheds its outer envelope to finally leave behind its inert core in the form of a white dwarf.
