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Astronomers Spot Oldest Known Planetary System In The Galaxy

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Lisa Winter

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707 Astronomers Spot Oldest Known Planetary System In The Galaxy
Peter Devine/Tiago Campante/University of Birmingham

Data obtained over a period of four years using NASA’s Kepler Space Telescope has revealed the oldest known planetary system in the galaxy, and it is fairly nearby. Kepler-444 is orbited by five planets and is estimated to be an astonishing 11.2 billion years old. Tiago Campante of the University of Birmingham in the U.K. is lead author of the paper, which was published in The Astrophysical Journal.

Kepler-444 is an orange dwarf star, slightly cooler and 25% smaller than our sun, located about 117 light-years away in the constellation Cygnus. Cosmically speaking, that isn’t very far, and it can be viewed with a pair of binoculars. It is also the primary member in a triple star system, with a binary system of red dwarf stars orbiting one another as they orbit Kepler-444. Its age of 11.2 billion puts its formation closer to the dawn of the universe (13.8 billion years ago) than the formation of our solar system (4.5 billion years ago).


The five planets in the system were observed by Kepler as they transited their star. The planets are on the small side, as their diameters range from 0.403-0.741 times that of Earth. However, they are all much too close to the star to reside in the habitable zone, so they are not capable of supporting life. All five planets have an orbit that is about one-tenth of Earth’s; even closer than the relative distance from Mercury to the sun. They are believed to be rocky, but their exact composition has not yet been determined.

The existence of this system is fairly impressive, given the amount of raw materials available to work with at the time. In the beginning, the universe was pretty much just hydrogen and helium. Stars formed, forged heavier elements like carbon and iron within their cores, spewed those elements out as they died. The cycle continued, with each generation of star producing more of the heavier elements necessary for planetary formation. The fact that a system could have had five planets at a time when these ingredients weren’t incredibly abundant is remarkable.

“This is one of the oldest systems in the galaxy,” co-author Steve Kawaler from Iowa State University said in a press release. “Kepler-444 came from the first generation of stars. This system tells us that planets were forming around stars nearly 7 billion years before our own solar system. Planetary systems around stars have been a common feature of our galaxy for a long, long time.”

Details of the system were learned by interpreting the sound waves of the star’s vibrations in what is known as astroseismology. Detecting minute changes in these vibrations yielded information regarding the star’s age, size, mass, density, and even surface gravity. As the planets transited the star and blocked the signal of the vibrations, the researchers were able to determine the planets’ size as well.


“There are far-reaching implications for this discovery,” added Campante. “We now know that Earth-sized planets have formed throughout most of the universe’s 13.8-billion-year history, which could provide scope for the existence of ancient life in the galaxy.”



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