Birth of a Star

Crab Nebula, Supernova Remnant

Like the mythical Phoenix Bird rising from the ashes of its own funeral pyre to soar again through the skies, a pulsar rises from the wreckage of its massive progenitor star–which has recently perished in the fiery blast of a supernova. In September 2018, a team of astronomers announced that they are the first to have observed the arrival of a pulsar emerging from the funeral pyre of its dead parent-star. This came at the same time that the Selection Committee of the Breakthrough Prize in Fundamental Physics recognized the British astrophysicist Dr. Jocelyn Bell Burnell for her discovery of pulsars–a detection first announced in February 1968.

This discovery elevated neutron stars right from the realm of science fiction to get to the status of virtual reality at a very dramatic way. Among a significant number of later important ramifications, it led to several powerful tests of Albert Einstein’s General Theory of Relativity (1915), and also led to a new comprehension of the origin of heavy elements in the Universe. Called metals by astronomers, heavy atomic elements are those that are heavier than helium.

The supernovae that provide birth to pulsars can take months or even years to fade away. Sometimes, the gaseous leftovers of the fierce stellar explosion itself wreck into hydrogen-rich gas and–for a brief time–regain their former brilliance. However, the question that needs to be answered is this: could they remain luminous without this sort of interference, resulting in their glowing encore performance?

In an effort to answer this nagging question, Dr. Dan Milisavljevic, an assistant professor of physics and astronomy at Purdue University in Wildlife Removal New York NY, declared that he had witnessed such an event six years following a supernova–dubbed SN 2012au–had blasted its progenitor star to smithereens.

“We haven’t seen an explosion of the kind, at this late timescale, remain visible unless it had some sort of interaction with hydrogen gas left behind by the star prior to explosion. But there’s no spectral spike of hydrogen from the information –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 melts quickly enough, it’s in a position to speed-up nearby charged particles and evolve to what astronomers term a pulsar wind nebula. This is likely what happened to SN 2012au, according to the new study published in The Astrophysical Journal Letters.

“We all know that supernova explosions produce these types of rapidly rotating neutron stars, but we never saw direct evidence of it in this exceptional time frame. This is a key moment once the pulsar wind nebula is bright enough to act as a lighbulb illuminating the explosions outer ejecta,” Dr. Milisavlievic continued to describe in the Purdue University Press Release.

Pulsars shoot out a regular beam of electromagnetic radiation, and weigh-in at roughly twice our Sun’s mass, since they spin wildly about 7 times each second! The beams emanating from brilliant pulsars are so extremely regular that they are frequently likened to lighthouse beams on Earth, and this beam of radiation is detectable as it sweeps our way. The radiation streaming out from a pulsar can only be seen when the light is targeted at the direction of the planet–and it’s also responsible for the pulsed look of the emission. Neutron stars are really compact, and they have short, regular rotational periods. This creates an extremely precise interval between the pulses ranging roughly from milliseconds to seconds for any individual pulsar. Astronomers find most pulsars through their radio emissions.

Neutron stars can roam around space either as solitary”oddballs” or as members of a binary system in close contact with another still”living” main-sequence (hydrogen-burning) star–or perhaps in the business of another stellar-corpse like itself. Neutron stars have also been observed nesting in brilliant, beautiful, and multicolored supernova remnants. Some neutron stars can even be orbited by a system of doomed planets that are utterly and completely inhospitable spheres which suffer a constant shower of deadly radiation crying out of their murderous leading parent. Indeed, the first package 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 through the space between stars. Particular pulsars even rival atomic clocks in their precision at keeping time.

The first observation of a pulsar was created on November 28, 1967, by Dr. Bell Burnell and Dr. Antony Hewish. The newly-spotted pulses were separated from 1.35 second intervals that originated from the same place 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 attempts to describe these exotic pulses, Dr. Bell Burnell and Dr. Hewish came to the realization that the extremely brief period of the pulses ruled out many known astrophysical sources of radiation, such as stars. Indeed, because the pulses followed sidereal time, they couldn’t be explained by radio frequency interference originating from intelligent aliens residing elsewhere in the Cosmos. When more observations were conducted, with a different telescope, they confirmed the presence of this truly odd and mysterious emission, and also ruled out any sort of instrumental effects. It was not until a second similarly pulsating origin was discovered in another area of the sky the playful”LGM” theory was completely ruled out.

All celebrities are immense spheres composed of fiery, roiling searing-hot gas. These monumental glaring stellar objects are mostly composed of hydrogen gas that has been pulled into a world very closely as the consequence of the relentless squeeze of the star’s own gravity. This is why a star’s core becomes so hot and dense. 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 components. The production of heavier atomic elements from lighter ones, occurring deep within the searing-hot center of a star, is termed stellar nucleosynthesis. The process of stellar nucleosynthesis begins with the fusion of hydrogen, which is both the lightest and most abundant atomic element in the Cosmos. The method ends with nickel and iron, that are fused only by the most massive 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 created from the supernovae explosions that end the”lives” of massive stars. Smaller stars go gentle into that good night and puff their beautiful multicolored outer gaseous layers into the distance between stars. Literally all of the nuclear elements heavier than helium–the metals–were created from the hearts of the Universe’s myriad stars.

The procedure for atomic fusion churns out a massive amount of energy. This is why stars shine. This energy is also responsible for creating a celebrity’s radiation pressure. This pressure produces a necessary and delicate balance that fights against the relentless squeeze of a star’s gravity. Gravity tries to pull all of a celebrities material in, while pressure attempts to push everything out. This ceaseless battle keeps a superstar bouncy against its inevitable collapse that will come as it runs out of its necessary supply of nuclear-fusing fuel. At that tragic stage, gravity wins the conflict and the star collapses. The progenitor star has reached the end of that long stellar street, and if it’s sufficiently massive, it goes supernova. This strong, relentless, merciless gravitational pulling speeds up the nuclear fusion reactions in the doomed star. Where once a star existed, a celebrity exists no more.

Before they meet their inevitable death, massive stars triumph in fusing a core of iron within their searing-hot hearts. Iron can’t 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 understood that SN 2012au was an unusual beast inhabiting the celestial zoo. The weird relic was odd and extraordinary in a number of ways. Even though the supernova blast wasn’t brilliant enough to be termed a “superluminous supernova”, it was bright enough to be quite energetic and last for quite a long time.

Dr. Milisavljevic forecasts that if astronomers continue to observe the sites of exceptionally bright supernovae, they may see similar sea-changes.

“If there is a pulsar or magnetar end nebula at the center of the exploded star, it may push from the inside out and even accelerate the gas. If we return to some of those events a couple of years after and take careful measurements, we might observe the oxygen-rich gas racing away from the explosion even faster,” Dr. Milisavljevic commented in the September 12, 2018 Purdue University Press Release.

Superluminous supernovae are passing celestial objects of great interest in the astronomical community. This is because they are potential sources of gravitational waves and black holes, and lots of astronomers also theorize that they may be related to other forms of celestial blasts, such as gamma-ray bursts and fast radio bursts. Astronomers are attempting to understand the fundamental physics that is the basis for them, but they are hard to observe. This is as they are relatively rare and are situated very far from Earth.

This new study aligns with one of Purdue University’s Giant Leaps, space, which is a part of Purdue’s Sesquicentennial 150 Decades of Giant Leaps.

Dr. Milisavljevic continued to note that”This is a fundamental process in the Universe. We wouldn’t be here unless this was occurring.

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