Tag Archives: Supernova

Stellar Evolution Part 3: Supergiant and Supernova

Most stars on the main sequence are relatively average: not too big and not too small. But every so often, a star begins its life as an absolute monster: a supergiant.

Supergiant

These supergiants do join the main sequence, but due to the sheer amount of gravitational force and pressure, they burn through the hydrogen in their cores in a fraction of the time that smaller stars do. They quickly leave the main sequence and expand in size to become thousands of times larger than the sun. Like smaller stars, these supergiants begin helium fusion in their cores and begin hydrogen fusion in shells around the core. But unlike smaller stars, which stop their fusion at this point, supergiants form several layers throughout the star of differently fusing gases, giving it an onion-type look.

Supergiant stellar evolution

Fusion in the core will eventually reach iron. At this point, nuclear fusion no longer produces energy, and so it stops. Without outward radiation pressure, the intense gravity causes the star to collapse. Protons and electrons get forced together in the core, turning it into a rigid sphere of neutrons. As the outer layers reach the limits of the neutron core, they rebound off and get propelled outward with huge amounts of energy. These shockwaves tear the star apart in a supernova.

Supergiant stellar

Credit: NASA, ESA, and G. Bacon (STScI) 

All that remains is the rigid sphere of neutrons, known as a neutron star. However, some supergiants are so massive that even the neutron star continues to collapse, creating an object so dense that it creates a singularity, also known as a black hole. Supergiants are rare in our universe, but their existence is crucial. Supernovas are so energetic that they create all of the elements heavier than iron, and many star systems, including our own, are made from the remnants of these explosions. Without them, life itself wouldn’t exist.

Written By: Scott Yarbrough

Additional Resource: Mouser

Supernovas!

Believe it or not, supernovas have been known to humans for thousands of years. That’s not to say that ancient civilizations knew exactly what was happening when they saw them, but they were witnesses to some of the most powerful events in our universe. When certain stars reach the end of their lifetime, they explode in a spectacular way. These stars are most commonly very large, anywhere from a few times as massive as our sun to a few hundred times as large. These supernovas emit an incredible amount of light, the brightest of which can be billions of times more luminous than our sun.Supernovas

However, these explosions occur fairly rarely. Scientists believe that only a handful happen in the Milky Way every thousand years. But when they do, they are bright enough to be seen from Earth. In the year 1054, Chinese astronomers observed a new star near the constellation of Taurus. It quickly grew, until it appeared even brighter than the planets in our solar system. This visitor star lasted for about two years, eventually dimming until it could no longer be seen.

Supernovas 1In the 1700s, astronomer John Bevis discovered the Crab Nebula in the Taurus constellation, and it was later recorded by Charles Messier as the first object in his 110-object catalogue. Two hundred years later in 1928, another astronomer named Edwin Hubble connected the records of the Chinese astronomers and the object known as the Crab Nebula to be the same thing, separated by almost a thousand years. His theory was that the nebula was the remnants of a supernova, which was the source of the visitor star.

This turned out to be correct, and later it was determined that at the center of the nebula was a pulsar – a very quickly spinning neutron star left over by the explosion. This revelation led to the discovery of dozens of other supernova remnants. Over the past few decades, research into supernovas has greatly expanded our knowledge of astronomy and stellar evolution. We haven’t seen a supernova in our galaxy for a long time, and we’re due one in the near future. Astronomers have identified several stellar candidates that may explode sometime soon – and when one of them does, we’ll get to experience another visitor star for the first time in hundreds of years.

Written by Scott Yarbrough

The Life and Death of Stars

Did you know that stars live and die just like other living things?…Okay, maybe not just like them. But they do have a beginning, middle, and end. All stars start out the same way, from a nebula. A nebula, otherwise known as a “star nursery”, is a cloud of gas and dust out in space. Nebulae will then start to clump up due to the massive amounts of gravitational pull. This clumping creates protostars, which are basically spherical masses of the gas and dust that are collecting even more gas and dust from the nebula.

stars 5

Once the gravity of the protostars becomes great enough, the process of fusion will begin, turning the protostar into a star. A star is defined to be a self-luminous gaseous spheroidal celestial body of great mass which produces energy by means of nuclear fusion reactions. Fusion is the act of turning lighter elements into heavier ones which can only occur under great pressures.

Depending on the original mass of the nebula and protostar, a star can be of any number of sizes. For our purposes, let’s stick with an average sized star (like our Sun),  a massive star, and a supermassive star.

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stars 3

For a Sun-like star, once it has completed fusing hydrogen into helium it will become unstable and swell in size, becoming a red giant. As a red giant, it will have a thin outer shell of some hydrogen gas, and an inner core of mostly helium. Once the helium runs out, it will become extremely unstable and puff out it’s shells of hydrogen and helium, becoming a planetary nebula. One example of this is the Ring Nebula (M57). Left in the center is a white dwarf star, which is named so due to how hot and luminous it is. When the white dwarf radiates its energy away, it will fade, becoming a brown (or black) dwarf star.

stars 1

stars

For a massive and supermassive star: they will go through the fusion process, become unstable, puff out a shell, swell to a red supergiant, start the next round of fusion, and so on and so forth, creating heavier and heavier elements. Once the massive and supermassive star become extremely unstable they will go supernova. A supernova is the largest explosion in space, which is very bright and ejects most of its mass.

stars 6When this happens for a massive star, a neutron star will be left behind. A neutron star is a celestial object with very small radius (typically 18 miles/30 km) and very high density, composed mostly of closely packed neutrons. Neutron stars also tend to rotate extremely quickly and emit regular pulses of radio waves and other electromagnetic radiation, earning them another name, pulsars.For a supermassive star, it will follow the same path of a massive star, but with one key difference. Instead of leaving a neutron star behind after the supernova, it will leave behind a black hole. A black hole is simply a region of space having a gravitational field so intense that no matter or radiation can escape.

Supernovae create the heaviest elements in our universe, which are the building blocks to life as we know it. Without this constant cycle of creation and destruction, we would have nothing. So the next time you look up in the sky, be thankful to that glowing orb of incandescent gas and all of the gas and dust that came before it.

A Supernova For Breakfast (Almost)

Iron makes up less than one one-hundredth of one percent of the human body. Most adults contain just a few grams of this micronutrient. Despite its small presence in humans, it’s essential to our lives. Without it, oxygen can’t get from the lungs to the rest of the body. Iron also plays a key role in energy production and DNA synthesis.

The human body can’t produce all the materials it needs to function, so we get vitamins and minerals from food and supplements. We don’t often directly observe substances like iron, calcium, or vitamin A in our food because they’re present in such tiny amounts. Iron, however, has an unusual property. It’s magnetic, so it’s relatively easy to sort out from other ingredients!

IronCerealGif

Trace amounts of magnetic material in a whole food item aren’t strong enough to break free from the larger structure, even in the presence of a strong magnetic field, so it helps to start with something that can be broken down into small parts. Breakfast cereal is one food that’s commonly fortified with iron and is also easy to crush into a powder. Bring a powerful magnet near the powdered cereal, and iron-rich fragments jump out.

Supernova remnant 1E0102.2-7219

Supernova remnant 1E0102.2-7219, visible near nebula M76 in the Southern Hemisphere, is an approximately 1,000-year-old leftover from the explosion of a huge star. Credit: NASA/JPL/Spitzer Space Telescope

Iron plays an important part in the lives of stars, too, as the end product of stellar fusion. After lighter elements in a very massive star’s core have fused into iron, the core begins to cool and condense. Central cooling causes outer layers of plasma to fall violently inwards, collide with the iron core, and blast back out into space. This incredibly energetic explosion is where all elements heavier than iron come from, including calcium, which is also essential to human biological function. (Lighter elements, including oxygen, come from fusion inside smaller stars.) From hydrogen to carbon to iron and beyond, you are literally made of star-stuff!

Written By: Caela Barry

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