Nov. 5 () –
astronomers led by the University of Warwick have identified the oldest star in the Milky Way that accumulates debris from orbiting planetesimals.
This makes her one of the oldest rocky and icy planetary systems discovered in the galaxy.
The findings, published this Saturday in the Monthly Notices of the Royal Astronomical Society, conclude that a faint white dwarf located 90 light-years from Earth, as well as the remains of its orbiting planetary system, They are over 10 billion years old.
The fate of most stars, including those like the Sun, is to become a white dwarf, which is a star that has used up all of its fuel and shed its outer layers. and now it is going through a shrinking and cooling process. During this process, the orbiting planets will be disrupted and, in some cases, destroyed, with their remains accumulating on the surface of the white dwarf.
For this study, the team of astronomers, led by the University of Warwick, modeled two unusual white dwarfs that were detected by the European Space Agency’s GAIA space observatory. Both stars are contaminated by planetary debris, and one was found to be unusually blue, while the other is the faintest and reddest found to date in the local galactic neighborhood; the team subjected both to further analysis.
Using spectroscopic and photometric data from GAIA, the Dark Energy Survey and the X-Shooter instrument at the European Southern Observatory to determine how long it has been cooling, astronomers found that the ‘red’ star WDJ2147-4035 is about 10.7 billion years old, of which 10.2 billion years have been spent cooling as a white dwarf.
Spectroscopy involves analyzing the star’s light at different wavelengths, which can detect when elements in the star’s atmosphere are absorbing light in different colors and help determine which elements are and how much is present. Analyzing the spectrum of WDJ2147-4035, the team found the presence of the metals sodium, lithium, potassium and carbon tentatively detected accreting in the star, making it the oldest metal-contaminated white dwarf yet discovered.
The second ‘blue’ star WDJ1922+0233 is only slightly younger than WDJ2147-4035 and was contaminated by planetary debris of a similar composition to Earth’s continental crust. The science team concluded that the blue color of WDJ1922+0233, despite its cool surface temperature, it is caused by its unusual mixed atmosphere of helium and hydrogen.
The remains found in the high-gravity, near-pure helium atmosphere of red star WDJ2147-4035 are from an ancient planetary system that survived the star’s evolution to a white dwarf, leading astronomers to conclude that this is the oldest planetary system around a white dwarf discovered in the Milky Way.
“THE EARTH IS NOT UNIQUE, THERE ARE SIMILAR PLANETARY BODIES”
Lead author Abbigail Elms, a PhD student in the Department of Physics at the University of Warwick, has said that these metal-contaminated stars “show that the Earth is not unique, there are other planetary systems with planetary bodies similar to Earth” and has highlighted that “97% of all stars will become white dwarfs and they are so ubiquitous throughout the universe that it is very important to understand them, especially you are extremely cool“.
“Formed from the oldest stars in our galaxy, cool white dwarfs provide insight into the formation and evolution of planetary systems around the oldest stars in the Milky Way,” said Elms, who stressed that they are finding “the oldest stellar remnants in the Milky Way that are contaminated by planets that were once similar to Earth.”
The main author of the study has pointed out that “it is surprising to think that this happened on the scale of ten billion years, and that these planets died long before the Earth formed.”
Astronomers can also use the star’s spectra to determine how fast those metals are sinking into the star’s core, allowing them to look back in time. and determine how abundant each of those metals were in the original planetary body.
“The red star WDJ2147-4035 is a mystery as the accumulated planetary debris is very rich in lithium and potassium and is unlike anything known in our own solar system. This is a very interesting white dwarf as its ultra-cold surface temperature, the metals that contaminate it, its age and the fact that it is magnetic, make it extremely rareElms explained.
For his part, Professor Pier-Emmanuel Tremblay, from the Department of Physics at the University of Warwick, has indicated that “when these old stars were formed more than 10,000 million years ago, the universe was less rich in metals than it is now, since that metals are formed in evolved stars and gigantic stellar explosions”.
“The two observed white dwarfs provide an exciting window into planet formation in a metal-poor, gas-rich environment that it was different from the conditions when the solar system formed“, the expert concluded.
