Like the mythical Phoenix Bird rising from the ashes of its own funeral pyre to soar again by the sky, a pulsar rises from the wreckage of its enormous progenitor star–that has recently perished in the fiery blast of a supernova. A pulsar is a newborn neutron star; a thick, rapidly rotating city-sized relic of an erstwhile enormous star that has collapsed under the stupendous weight of its own crushing gravity–to the fatal point that its component protons and electrons have merged together to form neutrons. Indeed, the fiery explosions of doomed stars as supernovae are sometimes so bright that they out-dazzle–for one fleeting shining moment–their complete home galaxy. In September 2018, a team of astronomers announced that they are the first to have witnessed the birth of a pulsar emerging from the funeral pyre of its dead parent-star. This came at the very same time that the Selection Committee of the Breakthrough Prize in basic Physics recognized the British astrophysicist Dr. Jocelyn Bell Burnell for her discovery of pulsars–a detection first announced in February 1968.
This Special Breakthrough Prize was given to Dr. Bell Burnell “for basic contributions to the discovery of pulsars, and a lifetime of inspiring leadership in the scientific community.” Her discovery of pulsars half a century ago proved to be one of the biggest surprises in the history of astronomy. This discovery elevated neutron stars right out of the vicinity of science fiction to reach the position of scientific reality in a very emotional way. Among a large number of later important ramifications, it resulted in several strong tests of Albert Einstein’s General Theory of Relativity (1915), and also led to a new understanding of the origin of heavy elements in the Universe. Called metals by astronomers, heavy atomic elements are all those that are heavier than helium.
The supernovae that give birth to pulsars can take months or already years to fade away. Sometimes, the gaseous leftovers of the fierce stellar explosion itself crash into hydrogen-high gas and–for a short time–regain their former radiance. However, the question that needs to be answered is this: could they keep luminous without this sort of interference, resulting in their bright encore performance?
In an effort to answer this nagging question, Dr. Dan Milisavljevic, an assistant professor of physics and astronomy at Purdue University in West Lafayette, Indiana, announced that he had witnessed such an event six years after a supernova–dubbed SN 2012au–had blasted its progenitor star to smithereens.
“We haven’t seen an explosion of this kind, at such a late timescale, keep visible unless it had some kind of interaction with hydrogen gas left behind by the star prior to explosion. But there’s no spectral spike of hydrogen in the data–something else was energizing this thing,” Dr. Milisavljevic explained in a September 12, 2018 Purdue University Press Release.
If a newborn pulsar sports a magnetic field and turns rapidly enough, it is able to speed-up nearby charged particles and evolve into what astronomers term a pulsar wind nebula. This is probably what happened to SN 2012au, according to the new study published in The Astrophysical Journal Letters.
“We know that supernova explosions produce these types of rapidly rotating neutron stars, but we never saw direct evidence of it at this rare time frame. This is a meaningful moment when the pulsar wind nebula is bright enough to act like a lighbulb illuminating the explosions outer ejecta,” Dr. Milisavlievic continued to explain in the Purdue University Press Release.
Lighthouses In The Sky
Pulsars shoot out a regular beam of electromagnetic radiation, and weigh-in at approximately double our Sun’s mass, as they spin wildly about 7 times each second! The beams emanating from bright pulsars are so extremely regular that they are frequently likened to lighthouse beams on Earth, and this beam of radiation is detectable when it sweeps our way. The radiation streaming out from a pulsar can only be seen when the light is targeted in the direction of our planet–and it is also responsible for the pulsed turn up of the emission. Neutron stars are extremely thick, and they have fleeting, regular rotational periods. This creates a very precise interval between the pulses that range approximately from milliseconds to seconds for any individual pulsar. Astronomers discover most pulsars by their radio emissions.
Neutron stars can wander around space either as lone “oddballs” or as members of a binary system in close contact with another nevertheless “living” main-ordern (hydrogen-burning) star–or already in the company of another stellar-corpse just like itself. Neutron stars have also been observed nesting within bright, beautiful, and multicolored supernova remnants. Some neutron stars can already be orbited by a system of doomed planets that are utterly and completely inhospitable spheres that suffer a continued shower of deadly radiation screaming out from their murderous stellar parent. Indeed, the first bundle of exoplanets, discovered in 1992, were the tragic planetary offspring of a deadly parent-pulsar. Pulsars switch off and on brilliantly, hurling their regular beams of light by the space between stars. Certain pulsars already competitor atomic clocks in their accuracy at keeping time.
The first observation of a pulsar was made on November 28, 1967, by Dr. Bell Burnell and Dr. Antony Hewish. The newly-spotted pulses were separated by 1.35 second intervals that originated from precisely the same location in space, and kept to sidereal time. Sidereal time is determined from the movement of Earth (or a planet) relative to the distant stars (instead of in respect to our Sun).
In their efforts to explain these exotic pulses, Dr. Bell Burnell and Dr. Hewish came to the realization that the extremely fleeting period of the pulses ruled out most known astrophysical supplies of radiation, such as stars. Indeed, because the pulses followed sidereal time, they could not be explained by radio frequency interference originating from intelligent aliens living in other places in the Cosmos. When more observations were conducted, using a different telescope, they confirmed the existence of this truly strange and mysterious emission, and also ruled out any sort of instrumental effects. The two astronomers nicknamed their discovery LGM-1, for “little green men”. It was not until a second similarly pulsating source was discovered in a different vicinity of the sky that the playful “LGM” theory was completely ruled out. The information “pulsar” itself is a contraction of “pulsating star”, that first appeared in print in 1968.
All stars are immense spheres composed of fiery, roiling searing-hot gas. These enormous glaring stellar objects are mostly composed of hydrogen gas that has been pulled into a sphere very firmly as the consequence of the relentless squeeze of the star’s own gravity. This is the reason why a star’s chief becomes so hot and thick. Stars are so extremely hot because their raging stellar fires have been lit as a consequence of nuclear fusion, which causes the atoms of lighter elements (such as hydrogen and helium) to fuse together to form increasingly heavier and heavier atomic elements. The production of heavier atomic elements from lighter ones, occurring thorough within the searing-hot heart of a star, is termed stellar nucleosynthesis. the time of action of stellar nucleosynthesis begins with the fusion of hydrogen, which is both the lightest and most abundant atomic component in the Cosmos. the time of action ends with iron and nickel, that are fused only by the most enormous stars. This is because smaller stars like our Sun are not hot enough to manufacture atomic elements heavier than carbon. The heaviest atomic elements–such as uranium and gold–are produced in the supernovae explosions that end the “lives” of enormous stars. Smaller stars go gentle into that good night and puff off their beautiful multicolored outer gaseous layers into the space between stars. These lovely objects, called planetary nebulae, are so beautiful that astronomers call them the “butterflies of the Universe”. Literally all of the atomic elements heavier than helium–the metals–were made in the hot hearts of the Universe’s myriad stars.
the time of action of nuclear fusion churns out a monumental amount of energy. This is the reason why stars shine. This energy is also responsible for creating a star’s radiation pressure. This pressure creates a necessary and delicate balance that battles against the relentless squeeze of a star’s gravity. Gravity tries to pull all of a stars material in, while pressure tries to push everything out. This eternal battle keeps a star bouncy against its unavoidable collapse that will come when it runs out of its necessary supply of nuclear-fusing fuel. At that tragic point, gravity wins the battle and the star collapses. The progenitor star has reached the end of that long stellar road, and if it is sufficiently enormous, it goes supernova. This powerful, relentless, merciless gravitational pulling speeds up the nuclear fusion responses in the doomed star. Where once a star existed, a star exists no more.
Before they meet their unavoidable decline, enormous stars succeed in fusing a chief of iron in their searing-hot hearts. Iron cannot be used for fuel, and at this point the progenitor star-that-was makes its sparkling farewell performance to the Cosmos–sometimes leaving behind a wildly spinning pulsar.
Before the new study, astronomers already knew that SN 2012au was an uncommon beast inhabiting the celestial zoo. The weird relic was extraordinary and strange in a number of ways. already though the supernova blast wasn’t bright enough to be termed a “superluminous supernova”, it was bright enough to be quite vigorous and last for a long time. It finally dimmed in a similarly slow light curve.
Dr. Milisavljevic predicts that if astronomers continue to observe the sites of extremely bright supernovae, they might see similar sea-changes.
“If there truly is a pulsar or magnetar wind nebula at the center of the exploded star, it could push from the inside out and already accelerate the gas. If we return to some of these events a few years later and take careful measurements, we might observe the oxygen-high gas racing away from the explosion already faster,” Dr. Milisavljevic commented in the September 12, 2018 Purdue University Press Release.
Superluminous supernovae are transient celestial objects of great interest in the astronomical community. This is because they are possible supplies of gravitational groups and black holes, and many astronomers also theorize that they might be related to other forms of celestial blasts, such as gamma-ray bursts and fast radio bursts. Astronomers are trying to understand the basic physics that is the basis for them, but they are hard to observe. This is because they are comparatively scarce and are located very far from Earth.
The next generation of telescopes, which astronomers call Extremely Large Telescopes, will have the technological ability to observe these mysterious events in greater detail.
This new study aligns with one of Purdue University’s Giant Leaps, space, which is a part of Purdue’s Sesquicentennial 150 Years of Giant Leaps.
Dr. Milisavljevic continued to observe that “This is a basic course of action in the Universe. We wouldn’t be here unless this was happening. Many of the elements basic to life come from supernova explosions–calcium in our bones, oxygen we breathe, iron in our blood–I think it’s crucial for us, as citizens of the Universe to understand this course of action.”