5 of the most unusual, amazing and interesting stars we've discovered in our universe.
Red giants, supernovas, hybrid stars, orbiting binaries, large stars, old stars, small stars, we've discovered thousands of stars within our milky way galaxy. Astronomers use incredible tools to figure out the characteristics of a star. These are 5 of the most amazing stars we've ever discovered in our galaxy.
“I’ve loved the stars too fondly to be fearful of the night. —— galileo“
A star, is a sphere of gas held together by its own gravity. The closest star to Earth is our very own Sun, so we have an example nearby that astronomers can study in detail. The lessons we learn about the Sun can be applied to other stars.
A star’s life is a constant struggle against the force of gravity. Gravity constantly works to try and cause the star to collapse. The star’s core, however is very hot which creates pressure within the gas. This pressure couteracts the force of gravity, putting the star into what is called hydrostatic equiliburum. A star is okay as long as the star has this equilibrium between gravity pulling the star inwards and pressure pushing the star outwards.
Before the advent of telescopes, stars just appeared to be twinkling specks in the sky, but all looked kind of similar. But when we started attaching cameras to our telescopes, a zoo of unusual suns with orbiting planets and sister stars and lives ending in black holes began to appear.
1- UY SCUTI:
UY Scuti is the largest star ever discovered. This red giant spans a width 1,700 times the diameter of our sun. You wouldn’t even be able to see the sun at this scale. So if we place the UY Scuti at the center of our solar system, it would engulf the entirety of Jupiter’s orbit, including the inner planets, the asteroid belt, the Earth. It’s that enormous. Though it’s the largest known star by volume, its density is 3,000 times less than Mars’s thin atmosphere. It’s not the brightest nor most massive nor hottest known star.
In fact, red giants are typically pretty cool as star temperatures go. UY Scuti was discovered in 1860, but when astronomers reexamined it in 2012, it set the record for largest known diameter.
UY Scuti was first cataloged in 1860 by German astronomers at the Bonn Observatory during the first sky survey of stars for the Bonner Durchmusterung Stellar Catalogue. It was named BD -12 5055, the 5,055th star between 12°S and 13°S counting from 0h right ascension.
Based on current models of stellar evolution, UY Scuti has begun to fuse helium and continues to fuse hydrogen in a shell around the core. The location of UY Scuti deep within the Milky Way disc suggests that it is a metal-rich star.
UY Scuti should fuse lithium, carbon, oxygen, neon, and silicon in its core within the next million years.After this, its core will begin to produce iron, disrupting the balance of gravity and radiation in its core and resulting in a core collapse supernova. It is expected that stars like UY Scuti should evolve back to hotter temperatures to become a yellow hypergiant, luminous blue variable, or a Wolf–Rayet star, creating a strong stellar wind that will eject its outer layers and expose the core, before exploding as a type IIb, IIn, or type Ib/Ic supernova.
Is the smallest star ever discovered and possibly the smallest star in existence. This red dwarf star is located 40 light years away in the southern constellation of Lepus, which is pretty close. But it’s so small and dim that you still need a telescope to see it.
Shining a mere 8,000th the luminosity of the sun, this star is smaller than Jupiter.
“J0523 appears to be at the limit of fusion”
It doesn’t have enough mass to ignite the core and start fusion. That’s what separates a star from the objects just lighter than it– the brown dwarfs. J0523 appears to be at the limit of fusion, which we think is around 1/13 the mass of the sun, making it theoretically the smallest possible star.
Members of the RECONS group have recently identified 2MASS J0523-1403 as representative of the smallest possible stars. Its small radius is at local minimums of the radius-luminosity and radius-temperature trends. This local minimum is predicted to occur at the hydrogen burning limit due to differences in the radius-mass relationships of stars and brown dwarfs. Unlike stars, brown dwarfs decrease in radius as mass increases due to their cores being supported by degeneracy pressure. As the mass increases an increasing fraction of the brown dwarf is degenerate causing the radius to shrink as mass increases.
3- PSRJ 1311-3430:
Nicknamed the Black Widow Pulsar, this unusual star was discovered in 2012. A pulsar is a special type of neutron star. That is a star that has collapsed under its own gravity after a supernova explosion until it is so dense that the neutrons it’s composed of are basically touching. But there’s more to a pulsar like J1311. They are spinning very fast. When you blinked just now, J1311 spun around 150 times.
What makes this pulsar so special is that it’s not alone. Orbiting at a distance of less than a round trip to the moon is a small companion star 10 times the mass of Jupiter. This pulsar is called a black widow binary, because the pulsar is killing off its companion.
J1311 blasts away material from the smaller start as it orbits every 93 minutes. That’s less time than you’ll probably spend on email today. And as it does so, the companion star get smaller and smaller, until eventually, J1311 will be alone.
This is the oldest star ever discovered. It is located in the halo of the Milky Way and thought to be close to the age of the universe itself.
How do we know that it’s so old? Well, the very first generation of stars were made out of the only elements that were around after the Big Bang— hydrogen, helium, and lithium.
These stars where massive, tens or hundreds of times the sun’s mass, and the bigger a star, the shorter it lives. So they exploded in supernovas spewing heavy metals into the universe.
The second generation of stars incorporated some of these heavy elements when they formed, and they were likely smaller, so they could live to the present day.
Later generations of stars would contain even more heavy metals as more stars went supernova. SM0313 has the lowest abundance of heavy metals of any star we’ve ever discovered.
But according to Professor Anna Frebel, we don’t know exactly how old it is.
She’s been searching for these relic stars throughout her career and was able to age a previous record holder, HE1523, to about 13.2 billion years old, because it has uranium, which astronomers can use to date stars. But SM0313 has little to no uranium, making it currently impossible to age. All we know is that the star likely formed only a few hundred million years after the Big Bang.
5- HV 2112:
Imagine this. A giant star explodes, leaving behind a super dense neutron star. Then this neutron core collides with a super giant star, which absorbs the core to form a hybrid star. It’s a star packed into the shell of another star like the turducken of stars.
This unusual object is called a ThorneZytkow Object and was hypothesized in 1977 by Kip Thorne and Anna Zytkow.
In 2014, astronomers discovered HV2112 in the small Magellanic cloud. It’s the strongest candidate yet for this type of object. ThorneZytkow objects could form either when in a binary star pair, one star goes supernova and throws off the balance, or in a crowded super cluster of stars.
On the outside, the star would look the same as a bright red super giant, but the inner signature would have other heavy elements like rubidium, strontium, yttrium, zirconium, molybdenum, and lithium.
Sure enough, HV2112 has this chemical signature. We can’t say for sure that it’s a hybrid star, because new models are needed. But it’s a very promising candidate.
A summary of today’s lesson
UY Scuti is the largest star ever discovered, though It’s not the brightest nor most massive nor hottest known star.
-Every star you see in the night sky is bigger and brighter than our sun.
-There are no green stars.
-The Sun is the closest star.
-Most stars are red dwarfs.
-Our sun is a dwarf star.
-Stars don’t twinkle.
-Black holes don’t suck.
-The most massive stars are the shortest lived.