The Alien Observatory –Odd White-Dwarf Star System Harbors a 13-Billion-Year-Old Planet (WATCH VIDEO)


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"In the quest for extraterrestrial biological signatures, the first stars we study should be white dwarfs," said Avi Loeb, theorist at the Harvard-Smithsonian Center for Astrophysics (CfA) and director of the Institute for Theory and Computation. Even dying stars could host planets with life – and if such life exists, we might be able to detect it within the next decade.

"A globular cluster might be the first place in which intelligent life is identified in our galaxy," observed Loeb's collague, Rosanne DiStefano at the CfA in January, 2016. Globular star clusters are extraordinary in almost every way. The globulars, which are found in the halo of a galaxy, contain considerably more stars than the less dense galactic, or open clusters, which are found in the disk. They're densely packed, holding a million stars in a ball only about 100 light-years across on average. They're old, dating back almost to the birth of the Milky Way. And according to new research, they also could be extraordinarily good places to look for space-faring civilizations, according to DiStefano.


In July 2003, Hubble helped make the astounding discovery of a planet called PSR B1620-26b, 2.5 times the mass of Jupiter, which is located in globular cluster M4 shown in the NASA animation below. It contains several tens of thousands stars and is noteworthy in being home to many white dwarfs—the cores of ancient, dying stars whose outer layers have drifted away into space.



The PSR B1620-26 system lies around 5,600 light years away in the globular cluster M4 shown in the video above, directly west of red supergiant star Antares in Constellation Scorpius. Its age is estimated to be around 13 billion years—almost three times as old as the Solar System. It is also unusual in that it orbits a binary system of a white dwarf and a pulsar (a neutron star).



The existence of a 13-billion year old planet, if in fact it still exists, highlights the fact that our Solar System exits in a universe that is estimated to be between 13.5 and 14 billion years old. A few intrepid astronomers have concluded that the most productive to look for planets that can support life is around dim, dying stars white dwarfs so prevalent in globular cluster M4 shown above.

This encouraging result comes from a new theoretical study of Earth-like planets orbiting white dwarf stars. Researchers found that we could detect oxygen in the atmosphere of a white dwarf's planet much more easily than for an Earth-like planet orbiting a Sun-like star.

When a star like the Sun dies, it puffs off its outer layers, leaving behind a hot core called a white dwarf.

A typical white dwarf is about the size of Earth. It slowly cools and fades over time, but it can retain heat long enough to warm a nearby world for billions of years. Since a white dwarf is much smaller and fainter than the Sun, a planet would have to be much closer in to be habitable with liquid water on its surface.

A habitable planet would circle the white dwarf once every 10 hours at a distance of about a million miles. Before a star becomes a white dwarf it swells into a red giant, engulfing and destroying any nearby planets.

Therefore, a planet would have to arrive in the habitable zone after the star evolved into a white dwarf. A planet could form from leftover dust and gas (making it a second-generation world), or migrate inward from a larger distance.

If planets exist in the habitable zones of white dwarfs, we would need to find them before we could study them. The abundance of heavy elements on the surface of white dwarfs suggests that a significant fraction of them have rocky planets.

"Although the closest habitable planet might orbit a red dwarf star, the closest one we can easily prove to be life-bearing might orbit a white dwarf," said Loeb.

The Daily Galaxy via Arxiv, and Harvard-Smithsonian CfA




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