Sunday, October 18, 2015

The Curious Case of 'Young Jupiter' Exoplanet

An artistic conception of the Jupiter-like exoplanet, 51 Eridani b, seen in the near-infrared light that shows the hot layers deep in its atmosphere glowing through clouds. Because of its young age, this young cousin of our own Jupiter is still hot and carries information on the way it was formed 20 million years ago. Credit: Danielle Futselaar & Franck Marchis, SETI Institute.

The newly discovered exoplanet 51 Eridani b, located about 100 light years from our planet in the constellation Eridanus is a curious example of a young Jupiter-like planet, only 20 million years old. The exoplanet looks like an infant in its cradle when compared to our solar system’s biggest gas giant that was formed about 4.5 billion years ago. “Although many Jupiter analogs have been detected this is the closest Jupiter analog that has been directly imaged,” Fredrik Rantakyro, Gemini Planet Imager (GPI) scientist and one of the co-discoverers of 51 Eridani b, told

The planet is two times the mass of Jupiter, and the most solar system-like planet ever directly imaged around another star. It orbits its parent star 51 Eridani at about 13 times the Earth-sun distance. Besides being what is likely the lowest-mass planet ever imaged, its atmosphere is also very cool – 430 degrees Celsius (800 degrees Fahrenheit). The exoplanet also features the strongest spectroscopic atmospheric methane signal, similar to the heavy methane dominated atmospheres of the gas giant planets in our solar system.

“Earlier directly imaged Jupiter analogs have been more like 5-10 times Jupiter mass and they don't have that strong methane signal that 51 Eridani b shows, it really looks like a planet spectra rather than a brown dwarf. The detection also shows that it is possible that these Jupiter analogs exist at these distances from its parent star, all the indirectly detected ones are much closer to its parent star. If we start finding very similar Jupiter analogs at Jupiter distances from its parent star it is suggestive of similar planet systems like our solar system,” Rantakyro noted.

51 Eridani b could provide us clues as to how solar systems form. Astronomers believe that the gas giants in our solar system formed by building up a large core over a few million years and then pulling in a huge amount of hydrogen and other gases to form an atmosphere.

Rantakyro underlines that the formation of the solar system is not well known. One of the most essential questions is about the birth of gas giants, are they formed by a seed 5-10 Earth mass body accreting the gas or is the planet formed by a collapsing a gas cloud directly to a planet.

“The formation of gas giants is very important as it is from models and local conditions clear that Jupiter been critical in the formation and conditions for life on Earth. Jupiter has cleared out the inner solar system of comets and asteroids and thus making the asteroid impacts on Earth less likely. It is believed that Jupiter had a role in making the size of Earth as it stopped earth from accreting and becoming bigger and ending up as one of the super earths that has been seen with Kepler [NASA’s exoplanet-hunting spacecraft],” he said.

The discovery is part of a broader effort to find and characterize new planets called the GPI Exoplanet Survey (GPIES). The survey expects to explore over 600 stars that could host planetary systems. GPIES is currently less than 20 percent through the targets slated for observations during the 3-year campaign. The targets were selected because of their youth and relatively close proximity to our solar system - within about 300 light years.

One more question that arises next is does 51 Eridani b could host alien life? According to Rantakyro it is possible, but very unlikely.

“The only two gas-giants that we have studied in detail - Jupiter and Saturn - there is no indication of life on those two planets. One should also remember that 51 Eridani b is very young and it is highly improbable that life could develop in a few millions years. So to conclude one could say almost with certainty that there is no life on 51 Eridani b,” Rantakyro concluded.

The team plans to conduct further observations of this young gassy exoplanet. However, the only instruments capable of detecting this planet is GPI and possibly also the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) at the Paranal Observatory in Chile. The astronomers have planned follow-up observations of the planet with GPI to obtain further details of its spectra and orbit as this will yield higher accuracy it the mass and temperature and composition.

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