In the late 16th century, astronomers Tycho Brahe and Johaness Kepler introduced the term “nova stella,” which means “new star” in Latin, to describe the transient appearance of new stars in the night sky. In 1572, when Tycho Brahe and his contemporaries discovered what appeared to be a new star in the constellation of Cassiopeia, brighter than Venus and with an apparent magnitude of -4, they quickly realized that what we now call SN 1572 (or Tycho’s Nova) must be farther from Earth than a planet, as during the months it remained visible, no movement or parallax was observed compared to fixed stars, unlike planets.
With an apparent magnitude of 8.4 and located 6,500 light-years away from Earth in the Taurus constellation, the Crab Nebula can be spotted with a small telescope, and the best time to observe it is in January. The nebula was discovered by the English astronomer John Bevis in 1731, then observed by Charles Messier, who initially mistook it for Halley’s Comet. Messier’s observation of the nebula inspired him to create a catalog of celestial objects that could be mistaken for comets. In this video, Dr. Padi Boyd takes us on a journey through the nebula, teaching us about some of the fascinating science behind this famous Hubble image. For a fairly accurate translation in French, click on the white rectangle at the bottom right. English subtitles should then appear. Click on the gear icon to the right of the rectangle, then on “Subtitles,” and finally on “Auto-translate.” Choose “French.” © NASA Goddard
Supernova Remnants in the Sight of Space Telescopes in Orbit
But neither Brahe nor Kepler had the means to know what it really was. It would take the discovery of nuclear physics and general relativity and their development.In the 1930s, Oppenheimer’s work shed light on cataclysmic star explosions known as supernovae. Nowadays, we can observe the remnants of these explosive stellar events, such as supernovae, which are short-lived hot plasma streams compared to the lifespan of stars. These phenomena are believed to be the source of many cosmic rays that hit Earth at energies far superior to what can be created on our planet. The study of supernova remnants can be done using X-rays, including the famous Chandra X-ray Observatory by NASA, as well as telescopes like Hubble and James Webb.
Over the years, by compiling images taken at different times, it has even become possible to create movies showing the movement of matter in certain supernova remnants.
The video shows the NIRCam (Near-Infrared Camera) image from Webb of the Cassiopeia A (Cas A) supernova remnant. The high resolution of NIRCam detects tiny gas knots resulting from the star’s explosion, as well as scattered light echoes in the field of view.
Recently, NASA released images captured over two decades of the famous Crab Nebula and Cassiopeia A supernova remnants. The Crab Nebula, a result of a brilliant supernova explosion observed by Chinese astronomers and others in 1054, is located 6,500 light-years away from Earth.Light-years away from Earth lies a neutron star, an ultra-dense compact object created by a supernova. Spinning around 30 times per second, its radiation beam passes through Earth with each rotation, resembling a cosmic lighthouse.
As the young pulsar slows down, large amounts of energy are injected into its environment. Particularly, a high-speed stream of matter and antimatter particles hits the surrounding nebula, creating a shockwave that forms the ring seen in the film. Jets from the pulsar’s poles eject matter and antimatter particles emitting X-rays in a direction perpendicular to the ring.
New films showcasing two of the most famous celestial objects – the Crab Nebula and Cassiopeia A – are being released by NASA’s Chandra X-ray Observatory. Each film includes X-ray data collected by Chandra over approximately two decades, revealing dramatic changes in the debris and radiation remaining after the explosion of two massive stars in our Galaxy.
A second film features Cassiopeia A (Cas A), the remnant of a supernova that supposedly exploded around 340 years ago in the Earth’s sky. The NASA press release explains that the film depicts the outer region of Cas A and the expanding shockwave from the explosion, similar to sonic booms generated by a supersonic aircraft.
As the shockwave moves outward, it encounters surrounding materials and slows down, generating a second shockwave that trails behind the first one, similar to a traffic jam moving away from the site of an accident on a highway. Cas A has been one of Chandra mission’s most observed and published targets, with the first official image captured by Chandra in 1999 after its launch into orbit aboard the space shuttle.Columbia, the observatory quickly discovered the first point source of X-rays in the center of Cas A, later confirmed to be a neutron star.
Over the years, astronomers have used Chandra to find evidence of the presence of a “superfluid” inside the neutron star of Cas A, revealing that the original massive star may have flipped during its explosion, and to make significant progress in determining precisely how giant stars explode. Chandra has also mapped the elements forged inside the star, which are now moving through space to help seed the next generation of stars and planets. More recently, Chandra’s data has been combined with that of NASA’s James Webb Space Telescope to help determine the origin of mysterious structures within the remnants.