Astronomers have made an exciting discovery of the remnants of planets with Earth-like crusts discovered in the atmospheres of four nearby white dwarf stars. The discovery was made by researchers from the University of Warwick, and they say the crust remnants offer a glimpse at planets that may have orbited the stars up to billions of years ago. The crust remnants found are from the outer layers of rocky planets similar to Earth and Mars.

Astronomers believe the discovery could give insight into the chemistry of planets dying stars once hosted. Another interesting tidbit about the discovery reported this week is that it includes one of the oldest planetary systems seen by astronomers so far. The team of researchers made the discovery by analyzing data from the European Space Agency Gaia telescope covering more than 1000 nearby white dwarf stars.

The team discovered an unusual signal from one white dwarf in particular and used spectroscopy to analyze the star’s light in different wavelengths. That technique allows scientists to detect when elements in the star’s atmosphere absorb light at different colors and determine what elements are present and in what quantity. Researchers on the project also inspected 30,000 white dwarf spectra gathered by the Sloan Digital Sky Survey over the last two decades.

The signal discovered matched the wavelength of lithium, and further observations of data discovered three additional white dwarf stars with the same signal. One of those stars also had potassium in its atmosphere. When the amounts of lithium and potassium were compared with other elements detected, including sodium and calcium, they found the ratio of elements matched the chemical composition of the crust for rocky planets like Earth and Mars. Assuming the crusts were vaporized and mixed with the star’s gaseous outer layers for 2 million years.

The outer layers of the white dwarf stars contain up to 300,000 gigatons of rocky debris, including up to 60 gigatons of lithium and 3000 gigatons of potassium. Those elements are equivalent to a 60 kilometers sphere of similar density to the Earth’s crust. Scientists believe what they’re observing around all four stars is material broken off from the planet rather than an entire planet.



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