NASA’s James Webb Space Telescope is studying one of the most well-known supernovae, SN 1987A (Supernova 1987A), which is located 168,000 light-years away in the Large Magellanic Cloud. For almost 40 years, since its discovery in February of 1987, SN 1987A has been intensely observed at various wavelengths from gamma rays to radio. The new observations made by Webb’s NIRCam (Near-Infrared Camera) offer a crucial piece of information that helps us understand how a supernova evolves over time to form its remnants.
The image indicates a central structure that resembles a keyhole, consisting of clumpy gas and dust that were ejected by the supernova explosion. The dust is so dense that even the near-infrared light detected by Webb cannot penetrate it, creating the dark “hole” in the keyhole.
A bright ring surrounds the inner keyhole and connects two faint arms of hourglass-shaped outer rings. It was formed from material ejected tens of thousands of years before the supernova explosion and contains hot spots. The spots are found even exterior to the ring, with diffuse emission surrounding it. These are the locations of supernova shocks hitting more exterior material. NASA’s Hubble and Spitzer Space Telescopes and Chandra X-ray Observatory have observed these structures, but Webb revealed a new feature – small crescent-like structures. These crescents are thought to be a part of the outer layers of gas shot out from the supernova explosion. Their brightness may be an indication of limb brightening, an optical phenomenon that results from viewing the expanding material in three dimensions. In other words, our viewing angle makes it appear that there is more material in these two crescents than there actually may be.
The resolution of these images is also noteworthy. Before Webb, the now-retired Spitzer telescope observed this supernova in infrared throughout its entire lifespan, yielding key data about how its emissions evolved over time. However, it was never able to observe the supernova with such clarity and detail.
Despite the decades of study since the supernova’s initial discovery, there are several mysteries that remain, particularly surrounding the neutron star that should have been formed in the aftermath of the supernova explosion. Like Spitzer, Webb will continue to observe the supernova over time. Its NIRSpec (Near-Infrared Spectrograph) and MIRI (Mid-Infrared Instrument) instruments will offer astronomers the ability to capture new, high-fidelity infrared data over time and gain new insights into the newly identified crescent structures. Further, Webb will continue to collaborate with Hubble, Chandra, and other observatories to provide new insights into the past and future of this legendary supernova.
SN 1987A was a type II supernova that occurred in the Large Magellanic Cloud, a dwarf satellite galaxy of the Milky Way. It happened about 168,000 light-years from Earth and was the closest supernova observed since Kepler’s Supernova. The light of 1987A reached Earth on February 23, 1987, and it was labeled “1987A” as it was the earliest supernova discovered that year. Its brightness peaked in May, with an apparent magnitude of about 3.
1987A was the first supernova that modern astronomers studied in great detail. Its observations have provided much insight into core-collapse supernovae.
