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Discovery: The Great Pink Planet

Pink Planet  GJ 504b

I’m well aware of what today is.  Believe me, I debated on whether or not to make a fake April Fools Day blog posting along the lines of “NASA announces the discovery of intelligent life on planet Eps Eri 04-01a,” or “50,000 year old space ship discovered in Antarctica.”  However, there’s stuff out there in space that’s real and strange enough to bring to light without having to result in phoney gags.  For example, a couple of days back I heard about the discovery of a pink planet way out in space.  So here’s the rundown on the lowest-mass planet ever detected around a star like the sun, GJ 504b that just happens to be pink.

The projected distance that GJ 504b presides away from us is 43.5 Astronomical Units.  What’s an astronomical unit?  It’s about 93 million miles and is essentially the length from the Earth to the Sun.  And GJ 504b is 43.5 of those astronomical units away from us.  So, yeah, it’s pretty far away.

Pink Planet in the sky

This chart locates the fifth-magnitude star GJ 504, also known as 59 Virginis, which is visible to the unaided eye from suburban skies

GJ 504b is about four times more massive than Jupiter and has an effective temperature of about 460 degrees Fahrenheit.  It orbits star GJ 504, which is slightly hotter than the sun, and is faintly visible to the unaided eye in the constellation Virgo. The star lies 57 light-years away and is estimated to be about 160 million years old, based on methods that link the star’s color and rotation period to its age.

This information was obtained by infrared data from the Subaru Telescope in Hawaii.  This is the lowest-mass planet ever detected by using direct imaging, and it challenges the current model on how gas giants are born.

According to the core-accretion model, gas giants like Jupiter get their start in the gaseous debris disk that surrounds a young star.  First a core is produced by collisions among asteroids and comets, and when this core gains enough mass its gravitational pull rapidly attracts gas from the disk to form the planet.

This model works fine for planets out to where Neptune orbits, about 30 times Earth’s average distance from the sun (30 astronomical units, or AU); however, it’s more problematic for worlds located farther from their stars.  GJ 504b, for example, has an orbit 9 times greater than Jupiter orbits our own sun.

Markus Janson at Princeton University in New Jersey says, “This is among the hardest planets to explain in a traditional planet-formation framework.  Its discovery implies that we need to seriously consider alternative formation theories, or perhaps to reassess some of the basic assumptions in the core-accretion theory.”

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