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"Two huge planets found orbiting a star 375 light-years away are the oldest alien worlds yet discovered, scientists say.

With an estimated age of 12.8 billion years, the host star—and thus the planets—most likely formed at the dawn of the universe, less than a billion years after the big bang.

"The Milky Way itself was not completely formed yet," said study leader Johny Setiawan, who conducted the research while at the Max-Planck Institute for Astronomy in Heidelberg, Germany.

During a recent survey, Setiawan and colleagues found the signatures of the two planets orbiting the star, dubbed HIP 11952.

Based on the team's calculations, one world is almost as massive as Jupiter and completes an orbit in roughly seven days. The other planet is nearly three times Jupiter's mass and has an orbital period of nine and a half months.

It's possible the planets are much younger than they seem if the worlds formed long after their star was born—but such a scenario is unlikely, the team says.

"Usually planets form just shortly after the star formation," Setiawan said. "Second-generation planets might also form after a star has died, but this is still under debate.""
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Now we need an FTL driven spaceship with a speed factor of 375, so a mission can be viable :P
orrr you can do what I do. And that is not give a damn for far away unreachable places which probably are not there anymore since the time needed for light to travel all the way through the galaxy is so loooonnngggg that for all we know the fourth big bang has already started and blow the place out of the sky! :D
The Milky Way Galaxy is about 100000 light-years in diameter, so these planets are only a stone's throw away. Very strange that they are older than the galaxy. Perhaps a measurement mistake?
In short they don't they can only approximate the age of star and by star then they approximate the age of the planets orbiting the star.
In length star ages are determined by a number of ways. Stars life span is generally separated into three categories. Youth, Middle age and old age. If the star is young then there are relative numbers to look at (dust cloud from which star is formed, temperature - determined by color, neighbours of stars, etc), Old stars are also easily to determinate since they burned out much of their fuel or entered a "giant" phase. The most difficult one is to determinate the age of middle aged stars.
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