Usually in astronomy, the telescope detects a strange object and then leaves the work to the researchers. But sometimes the opposite happens.
In 1975, two physicists proposed the concept of a very strange type of object: a red giant star containing an inner neutron star called the Thorne-Zytko object.
In June 2014, a team of scientists using telescopes at the Las Campanas Observatory in Chile discovered numerous red giants which they believe to be strange objects thought to have been around for almost 40 years previously.
Scientists have spent years wondering what the first stars looked like and what will become of the last ones, billions of years from now.
Thorne-Zytkow object. Source: Curiosity.com
Some, like the Thorne-Zytkow object, were hypothesized and confirmed in practice decades later. There were also certain types of stars that were thought to exist elsewhere, but as we learned more about the laws that govern the entire universe, these stars turned out to be non-existent.
Others are completely transformed into a new domain. In 1784 it was suggested that some stars were so massive that they might have enough gravity to keep light from escaping.
This went unnoticed until Einstein formulated the general theory of relativity in 1915, which asserted that such stars could exist but under a new name – black holes.
With increasingly powerful telescopes and rapidly advancing technology, we may one day be able to confirm the existence of one of these types of singularities. Below we take a look at some of the candidates.
The early universe was largely devoid of heavy elements, which means that the first stars would be composed of only hydrogen and helium.
These “Population III” stars must be several hundred times more massive than the Sun, which means they will quickly burn up their fuel and become a Supernova.
Traces can be left by Population III stars. Photo: Spitzer Telescope, NASA
This process would cause the surrounding space to contain heavier elements (than hydrogen and helium), so we don’t know for sure if any Population III stars still exist.
However, the GRB 130925A- gamma-ray burst observed in 2013, would be the collapse of one of these stars, whose light has just reached us.
DARK STAR (DARK STAR)
There was another type of star in the early universe that was even weirder. When galaxies begin to form, dark matter gathers in their center and stars born in this region can be made up of 10% dark matter.
This amount of dark matter allows stars to be several million times more massive than the Sun and a billion times brighter, but of course in return for a very short lifespan. As soon as the dark matter fuel is exhausted, the star collapses. This is probably exactly how supermassive black holes form.
The James Webb Space Telescope will be responsible for finding evidence of this type of star.
Even in the current universe, there are stars waiting to be discovered, including Blitzar.
Dying stars will only become supernovae and collapse into black holes when they exceed a certain mass. Otherwise, they will become neutron stars.
Blitzar – illustration. Source: arstechnica
Blitzar is a neutron star with a mass above supernova threshold, but spinning very rapidly. Over time they slow down and eventually the star will collapse into a black hole, releasing an incredibly large amount of energy.
This type of collapse is thought to be responsible for many “fast radio bursts (FRBs)” which are so powerful but only last a few milliseconds.
There is another type of star that lies between the boundary of a neutron star and a black hole, the Quark star.
If the neutron star’s mass isn’t enough to collapse into a black hole, but it’s still massive enough to turn a neutron into a quark, it becomes a quark star. In this case, the quark can only exist under extreme pressure and temperature.
However, if quarks can be transformed into heavier strange quarks, they will become more stable. Over the years, potential candidates for quark stars have been found, but none have been confirmed.
BIG BLACK STAR
The ultimate fate of the Sun is a question that many astronomers are trying to answer.
In about 5 billion years, the Sun will run out of fuel and shrink into a white dwarf, like many other stars in the universe. Instead of generating energy through a fusion reaction, all the light will come from intense thermal radiation.
Black dwarf – Illustration. Source: Google Sites
Over time, the white dwarf will fade and cool, until what remains is a cool black dwarf that emits no radiation and is almost unobservable. The duration of this process is uncertain, but estimates are for at least a quadrillion years (one billion million million years).