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Astronomers discover the oldest known planet

Posted on: Friday, 11 July 2003, 06:00 CDT

Astronomers discover the oldest known planet

WASHINGTON, July 10 (Xinhua) -- Astronomers Thursday announced the discovery of the farthest and oldest known planet, which was formed almost 13 billion years ago, long before the Sun and Earth ever existed.

The gaseous planet, 2.5 times the mass of Jupiter, lies near the core of an ancient globular star cluster called M4, located 5, 600 light-years away in the constellation Scorpius, a group of US and Canadian astronomers told a press conference held in Washington, DC.

The story of the planet's discovery began in 1988 when a pulsar was identified in M4, which consists of more than 100,000 stars. The pulsar is a neuron star spinning just under 100 times per second and emitting regular radio pulses like a lighthouse beam.

Later observations showed that the pulsar was companioned by a burned-out white dwarf star and a third object, whose identity was a mystery. The object was suspected to be a planet, but some researchers argued that it could also have been a brown dwarf or a low-mass star.

Thanks to measurements of the Hubble Space Telescope, the decade- long debate over the mystery object was now settled, the US- Canadian group said.

Hubble's observations of the dim white dwarf helped the astronomers to precisely measure the mass the object, confirming that it is a planet.

The very existence of the planet provides tantalizing evidence that the first planets formed rapidly, within a billion years of the Big Bang which created the universe about 13.7 billion years ago, implying that planet formation happened very early in the universe and that planets may be very abundant in our galaxy, the astronomers said.

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