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Newly discovered pink planet smallest to be photographed yet


Kevan Karanjia
Staff Writer

Saturday, August 10, 2013, 9:05 - Astronomers have photographed the smallest exoplanet to orbit a star very much like our own - and it's the colour pink.

GJ 504b was photographed using the Subaru Telescope in Hawaii, it is thought to be a magenta colour. (Photo courtesy of NASA’s Goddard Space Flight Center/S. Wiessinger)

GJ 504b was photographed using the Subaru Telescope in Hawaii, it is thought to be a magenta colour. (Photo courtesy of NASA’s Goddard Space Flight Center/S. Wiessinger)

NASA astronomers have photographed the smallest exoplanet (by mass) to orbit a star very much like our own. 

Using the Subaru telescope in Hawaii, infrared data shows planet GJ 504b is magenta in colour.

The discovery is significant because it is the lowest mass planet ever detected using direct imaging techniques. It's is one of around six exoplanets directly imaged by a telescope rather than construed from observing stars.  

Researchers believe the colour indicates less cloud cover than other exoplanets, meaning there's a possibility to view deeper into its atmosphere. 

"If we could travel to this giant planet, we would see a world still glowing from the heat of its formation with a color reminiscent of a dark cherry blossom, a dull magenta," said Michael McElwain, a member of the discovery team at NASA's Goddard Space Flight Center in a release. "Our near-infrared camera reveals that its color is much more blue than other imaged planets, which may indicate that its atmosphere has fewer clouds."

 GJ 504b revealed by combining Subaru images of GJ 504 using two near-infrared wavelengths (orange, 1.6 micrometers, taken in May 2011; blue, 1.2 micrometers, April 2012). (Photo courtesy of NASA’s Goddard Space Flight Center/NOAJ)

GJ 504b revealed by combining Subaru images of GJ 504 using two near-infrared wavelengths (orange, 1.6 micrometers, taken in May 2011; blue, 1.2 micrometers, April 2012). (Photo courtesy of NASA’s Goddard Space Flight Center/NOAJ)

GJ 504b has a mass four times larger than Jupiter but is around the same size. 

It orbits its star at nearly nine times the distance Jupiter orbits the sun, challenging theoretical ideas of how giant planets form. 

Scientists generally accept the core-accretion model, which dictates how gas giants form.

Planets like Jupiter begin to develop from the gas-rich debris disk that surrounds a young star. Collisions from asteroids and comets produce a core that once at sufficient mass, uses its gravitational pull to attract gas from the disk. 

This theory works for planets that orbit stars at a distance similar to Neptune's (30 times Earth's average distance from the sun, 30 Astronomical Units) but becomes more problematic at orbits much further away.

GJ 504b orbits its star around 43.5 Astronomical Units. The actual distance depends on how the star system tips to our line of sight. 

"This is among the hardest planets to explain in a traditional planet-formation framework," explained team member Markus Janson, a Hubble postdoctoral fellow at Princeton University in New Jersey in a release. "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."

GJ 504 can be found in the constellation Virgo and is visible to the naked eye. (Photo courtesy of NASA’s Goddard Space Flight Center)

GJ 504 can be found in the constellation Virgo and is visible to the naked eye. (Photo courtesy of NASA’s Goddard Space Flight Center)

This research is based on the Strategic Explorations of Exoplanets and Disks with Subaru (SEEDS), a plan to photograph as many extrasolar planets and protoplanetary disks around nearby stars using the Subaru Telescope in Mauna Kea, Hawaii. 

The project began in 2009, led by the National Astronomical Observatory of Japan. 

Its use of direct imaging is revolutionary, but extremely challenging.

Masayuki Kuzuhara at the Tokyo Institute of Technology led the research team and said in a release: "Imaging provides information about the planet’s luminosity, temperature, atmosphere and orbit, but because planets are so faint and so close to their host stars, it's like trying to take a picture of a firefly near a searchlight."

Scientists have found that GJ 504b has an effective temperature of about 237 degrees Celsius. It orbits the G0-type star GJ 504, which is slightly hotter than the sun and faintly visible to the naked eye around the constellation Virgo.   

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