The last moments when scientists saw the wreckage of a planet for the first time | White Dwarf / Epoch Times

[Epoch Times, February 10, 2022]Astronomers from the University of Warwick in the United Kingdom observed for the first time that it was torn apart.planetThe impact of debrisWhite dwarfOn the surface of the moment, this isplanetThe last time of the wreckage. Scientists estimate that this planetary system has existed for billions of years.

The research team uses X-rays to detect rock-like and gaseous material impactsWhite dwarfAnd the process of being swallowed by a white dwarf. These substances are the remains of planetary systems that were destroyed after their stars died. This is the first direct measurement of the accretion of rocky material onto a white dwarf.

The research results confirm the circumstantial evidence in more than a thousand stars accumulated over the past few decades.

Most stars, including the sun, will eventually become white dwarfs. More than 300,000 white dwarfs have been discovered in our Milky Way, and many of them are believed to be accreting debris from planets and other objects that once orbited them.

For decades, astronomers have been using optical and ultraviolet wavelength spectra to measure the abundance of elements on the surface of stars and calculate its source. There is circumstantial evidence in the spectrum that stars are accreting surrounding matter. These observations show that about 25-50% of white dwarfs contain heavy elements such as iron, calcium, and magnesium mixed in their atmospheres.

However, until now, astronomers have not seen rocky substances being pulled into stars.

“We have finally seen that matter actually enters the atmosphere of a star,” Dr. Tim Cunningham of the University of Warwick said in a statement. This is the first time we have been able to derive the accretion rate of a detailed model that does not depend on the atmosphere of a white dwarf. Interestingly, it is very consistent with the previous theory. 」

“Previously, the measurement of accretion rate used spectroscopy and relied on the white dwarf model. These are numerical models that calculate the speed at which elements sink from the atmosphere into the star, and tell you how much is the accretion rate of falling into the atmosphere. Then you can push back and calculate how many elements are in the original celestial body, whether the celestial body is a planet, a satellite, or an asteroid. “Dr. Cunningham added.

A white dwarf is a star that burns all fuel and sheds its outer material. In the process, it may interfere with or destroy any celestial body orbiting it. When material from these celestial bodies is pulled into the star at a sufficiently high speed, it will violently hit the surface of the star, forming a plasma heated by a shock wave.

The temperature of this plasma is between 100,000 and 1 million kelvins, and then deposited on the surface of the white dwarf. When it cools, it emits observable X-rays. X-rays are radiation with higher energy than the light that we can see with the naked eye. In astronomy, X-rays are the key high-energy signals for matter to fall into strange celestial bodies such as black holes and neutron stars.

Observing these X-rays is very challenging. Therefore, astronomers used the Chandra X-Ray Observatory to analyze the neighboring white dwarf G29-38.

This new research also confirms that many mysteries in the universe are not visible to the naked eye, but require other means, such as high-energy radiation like X-rays, to be seen.

Dr. Cunningham said in the above statement: “What is really exciting about this result is that we are using different wavelengths, that is, X-rays, to help us explore completely different types of physical mechanisms. This discovery provides the first direct evidence that white dwarfs are currently accreting the remnants of old planetary systems. Detecting accretion in this way provides a new technology through which we can study these systems, giving us a glimpse of thousands of known exoplanet systems and the fate of the solar system. 」

The paper of this new research was published in the journal Nature on February 9, 2022.

Responsible Editor: Lin Yan#

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