current newsGermany – Astronomers in Germany have seen the fiery ‘nova explosion’ of a white dwarf (old star) for the first time.
Reported from Dailymail.co.ukon May 21, researchers observed the event, thanks to data from the German-Russian cooperation eROSITA X-ray telescope, which is placed in space about 900,000 miles away.
–
The X-ray flash, dubbed the YZ Reticuli, fully exposes the central detector of the eROSITA telescope, which records the energy of the emitted photons.
White dwarfs are the very dense remnants of sun-sized stars after they have exhausted their nuclear fuel, shrinking to roughly the size of Earth.
Sometimes such dead stars re-ignite in superheated explosions and produce fireballs of X-ray radiation.
Related news :
The “Blood Red” Super Moon Eclipse Will Look Bigger This Week
–
This nova explosion occurs from a white dwarf in a binary system, or a system consisting of two stars that are gravitationally bound.
Researchers are now able to observe such bursts of X-ray light for the first time, coming from a white dwarf in the constellation Reticulum.
Although the observations were made by eROSITA in July 2020, they were just detailed in a new study, led by astronomers at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) in Erlangen, Germany.
“It was a lucky coincidence, really.” said study author Ole König at FAU. “We were really lucky.”
“These X-ray flashes only last a few hours and are nearly impossible to predict, but the observation instruments must be pointed directly at the explosion at the right time.”
eROSITA floats in space in the Lagrange Point 2 (L2) zone, a gravitationally balanced area between the Sun and Earth some 900,000 miles (1.5 million km) away.
eROSITA has been observing the sky for soft X-rays since 2019, although due to the breakdown of cooperation between Germany and Russia following the invasion of Ukraine, the instrument stopped collecting data on February 26, 2022.
Less than a year after starting operations, on July 7, 2020, eROSITA measured intense X-ray radiation in a completely inconspicuous area of the sky just four hours earlier.
Related news :
Mysterious Radio Bursts Tracked from Space Galaxy
–
When the X-ray telescope observed the same position in the sky four hours later, the radiation had disappeared. Therefore, the X-ray flash should last less than eight hours.
X-ray bursts like this were predicted by theoretical research in a 1990 study but had never been observed directly until now.
This X-ray fireball appears on the surface of a white dwarf, or star that is initially comparable in size to the sun before depleting most of its hydrogen fuel and then helium deep in its core and shrinking.
White dwarfs, composed mostly of oxygen and carbon, are similar in size to Earth but contain a mass that can be similar to our sun.
“One way to describe these proportions is to imagine the Sun is the same size as an apple, which means the Earth would be the same size as a pinhead orbiting an apple at a distance of 10 meters,” said Professor Jörn Wilms, also at FAU.
Trying to explain white dwarfs, the researchers say you should imagine shrinking an apple to the size of a pinhead. These tiny particles will hold the relatively large weight of the apple.
Just a teaspoon of matter from inside a white dwarf easily has the same mass as a large truck.
Related news :
Scientists “Cast” These Tough Animals Into Space
–
A white dwarf is so hot that it glows white, but the radiation from it is so weak that it is difficult to detect it from Earth.
In binary star systems (solar systems with two stars), white dwarfs can be accompanied by other stars that are still burning.
In this case, the enormous gravitational pull of the white dwarf pulls hydrogen from the shell of the accompanying star.
In time, this hydrogen can collect to form a layer several meters thick on the surface of the white dwarf.
In this layer, the immense gravitational pull creates enormous pressure that causes the star to re-ignite, causing a massive explosion in which the hydrogen layer explodes.
Explosive X-ray radiation like this hitting the eROSITA detector on July 7, 2020 produces an overexposed image.
“Using model calculations we originally made while supporting the development of X-ray instruments, we were able to analyze the overexposed image in greater detail during a complex process to obtain a behind-the-scenes view of a white dwarf or nova explosion,” said Professor Wilms.
The explosion produced a fireball with a temperature of about 327,000 degrees Kelvin, making it about sixty times hotter than the Sun.
Because these novae run out of fuel fairly quickly, they cool quickly and the X-ray radiation becomes weaker until it eventually becomes visible light.
This visible light reached Earth half a day after the detection of eROSITA and was observed by optical telescopes.
“A star that appears bright then appears, which is actually the visible light from the explosion, and is so bright that it can be seen in the night sky with the naked eye,” said König.
It seems that a ‘new star’ like this has been observed in the past and is given the name ‘nova stella’, or ‘new star’ because of its unexpected appearance.
Because these novae are only visible after flashes of X-rays, it is very difficult to predict such outbreaks and is mostly just a coincidence when they hit X-ray detectors.
/data/photo/2022/05/22/6289797602f12.jpg?resize=150%2C150&ssl=1)