In 1987, humanity observed the closest supernova since 1604.
In 1604, the last naked-eye supernova occurred in the Milky Way, known today as the Kepler supernova. Although the supernova faded from naked eye view by 1605, its remnants are still visible today, shown here in a composite X-ray/optical/infrared image. The bright yellow “lines” are the only element still visible in the visual field, more than 400 years later.
From 165,000 light-years away, the core of a giant blue star collapsed.
This optical image, captured by the Hubble Space Telescope in 2017, shows the remnants of supernova SN 1987a exactly 30 years after its explosion was observed. Located about 165,000 light-years away in the Large Magellanic Cloud, on the outskirts of the Tarantula Nebula, this supernova is the first and only supernova discovered within our Local Group in more than 100 years.
The first signals detected were neutrinos: they arrived in a burst lasting about 12 seconds.
Three different detectors have detected neutrinos from SN 1987A, with KamiokaNDE being the most powerful and successful. The shift from a nucleon decay experiment to a neutrino detector experiment would pave the way for the development of neutrino astronomy. The light from the supernova will not arrive for hours later.
Hours later, light arrived, indicating a supernova collapse.
Next, we carefully observed the expanding and developing remnants.
This image shows the supernova remnant SN 1987a in six different wavelengths of light. Even though it’s been 36 years since that explosion, and even though it’s right here in our backyard, the material around the central engine has not been cleared enough to reveal stellar remnants. In contrast, cow-like objects (also known as fast blue optical transients) have their nuclei exposed almost immediately.
In the suburbs, gas shells that exploded centuries ago continue to expand.
The remnant of Supernova 1987a, located in the Large Magellanic Cloud about 165,000 light-years away. It was the closest supernova observed to Earth in more than three centuries, with a maximum magnitude of +2.8, clearly visible to the naked eye and significantly brighter than the host galaxy containing it.
Inside, supernova shock waves heat a spherical halo of matter.
Hubble’s optical observations of Supernova 1987A become even more valuable when combined with observations from telescopes that can measure other types of radiation from the exploding star. The image shows evolving images of the hotspots from the Hubble Telescope along with images taken around the same time from the Chandra X-ray Observatory and the Australian Telescope Compact Array (ATCA) radio observatory. X-ray images show an expanding ring of gas, hotter than a million degrees, that clearly reached the optical ring at the same time as the hotspots. Radio images show a similar expanding ring of radio emission, caused by electrons moving through the magnetized material at nearly the speed of light.
Energy injection causes irregular changes in brightness and X-ray and radio emission.
Combined observations at long wavelengths show that the remnant continues to expand, and interstellar luminosity continues to rise in the vicinity of the initial explosion. Brightness in a variety of wavelengths of light continues to evolve as different shapes of projectiles collide with the surrounding matter and heat it, causing it to radiate.
But the inner region of this explosion remains mysterious.
The outward-moving shock wave of material from the 1987 explosion continues to collide with previous ejecta from the previous massive star, heating and lighting up the material as the collisions occur. A wide range of observatories continue to image supernova remnants to this day, tracking its evolution. However, the interior area remains heavily covered in dust, preventing us from knowing what’s really going on inside.
The collapsed core should create a massive remnant: a neutron star.
Together, five different wavelengths show the true magnificence and diversity of phenomena occurring in the Crab Nebula. The X-ray data, in purple, shows the hot gas/plasma created by the central pulsar, which is clearly recognizable in both the individual and composite images. This nebula originated from a massive star that died in a supernova that collapsed in its core in 1054, with bright light appearing across the globe, allowing us, in the present, to reconstruct this historic event.
A similar supernova in 1054 gave rise to the Crab pulsar that exists today.
A combination of X-ray, optical and infrared data reveals the central pulsar at the heart of the Crab Nebula, including winds and outflows carried by the pulsars into the surrounding material. The bright purple-white central spot is actually the Crab pulsar, which itself rotates about 30 times per second. The material shown here is about 5 light-years across, and originated from a star that went supernova about 1,000 years ago, which tells us that the typical speed of ejecta is about 1,500 kilometers per second. The neutron star originally reached a temperature of about 1 trillion Kelvin, but so far it has actually cooled to “only” about 600,000 Kelvin.
However, there is no neutron star associated with SN 1987a.
This image shows an illustration of a massive neutron star, along with the distorting gravitational effects that an observer would see if they were able to see this neutron star up close. While neutron stars are famous for pulsing, not every neutron star is a pulsar. It is currently unknown whether the remnant of SN 1987a will evolve into one.
However, there are two pieces of evidence that suggest one of them may be developing.
As the core region of SN 1987A continues to evolve, the central dust region will cool and much of the radiation obscured by it will become visible, while the central remnant will continue to cool and evolve as well. It is possible that, when this happens, periodic radio pulses could become observable, revealing whether the central neutron star is a pulsar or not.
ALMA observations reveal huge amounts of gas and internal dust.
High-resolution ALMA images have revealed a hot “bubble” in the dusty core of Supernova 1987A (inset), which could be the location of the expected neutron star. The red color shows the dust and cold gas at the center of the supernova remnant, captured at radio wavelengths with ALMA. The green and blue colors reveal where the expanding shock wave from the exploding star collided with a ring of material around the supernova. An observatory such as the James Webb Space Telescope is ideal for detecting matter in the “dark” regions of this image.
The central “hot spot” indicates the presence of a newborn neutron star.
At the center of the remnant of SN 1987a, ALMA, thanks to its amazing resolution and long-wavelength capabilities, was able to observe a particularly hot spot within the gas and dust contained in SN 1987a. Many believe the excess heat is an indication of a young neutron star, making this the smallest neutron star ever discovered.
Now, the James Webb Space Telescope has joined in, offering its unique views.
The Webb NIRCam (near infrared camera) captured this detailed image of SN 1987A (Supernova 1987A), which has been annotated to highlight key structures. In the center, the material ejected from the supernova forms a keyhole shape. To its left and right are faint crescents recently discovered by Webb. Behind them is an equatorial ring, made of material ejected tens of thousands of years before the supernova explosion, containing bright hotspots. Outside of that there is diffuse emission and two faint outer rings.
Newly revealed features include the appearance of “crescents” in the gas.
The innermost region of the remnant of SN 1987a, as revealed by the James Webb Space Telescope, shows light-blocking gas and dust at the center, and crescent-like shapes, all within the spherical region of hot gas affected by the supernova’s ejections. The features of the crescent, in particular, have not been seen by any telescope before the James Webb Space Telescope, and its nature has not yet been revealed.
Are they regular projectiles or shapes sculpted by magnetic fields?
The supernova explosion enriches the surrounding interstellar medium with heavy elements. This illustration of the remnant of SN 1987a shows how material is recycled from a dead star into the interstellar medium. However, what exactly is happening at the center of the remnant remains a mystery, as even JWST’s powerful NIRCam imager cannot fully penetrate the light-blocking dust to see what’s inside.
The evolution of the supernova remnant will eventually reveal the object contained within.
A small, dense object only twelve miles in diameter is responsible for the X-ray nebula that extends about 150 light-years across. This pulsar rotates approximately 7 times per second, and has a magnetic field on its surface estimated to be 15 trillion times stronger than Earth’s magnetic field. Perhaps, within what remains of SN 1987a, a modern version of this phenomenon is occurring.
We may be witnessing the formation of the newest pulsar of our local cluster.
This computer simulation of a neutron star shows charged particles orbited by the neutron star’s extremely strong electric and magnetic fields. A neutron star may have formed within the remnants of SN 1987a, but the region is still too dusty and gas-rich for “pulses” to escape.
Mostly Mute Monday tells an astronomical story with pictures, visuals, and no more than 200 words.