spaceSpace and Physics

This Neptune-Sized Exoplanet Has A Blue Sky Like Earth


Dr. Alfredo Carpineti

Senior Staff Writer & Space Correspondent

clockNov 26 2015, 20:07 UTC
4017 This Neptune-Sized Exoplanet Has A Blue Sky Like Earth
Artists impression of GJ 3470b and its host star, by NAOJ.

Astronomers can learn a lot about a planet using very little. In this specific case, a team of researchers was able to find out that the sky of an exoplanet 100 light-years from Earth is blue. The planet, which is about the size of Neptune, is the smallest on which Rayleigh scattering – the same effect responsible for the blue sky on Earth – has been detected.

The discovery was possible thanks to the Las Cumbres Observatory Global Telescope network. Astronomers observed light scattering on tiny particles in the exoplanet atmosphere, and they saw that those molecules scattered blue light more. 


Unfortunately, blue skies don’t equate to an atmosphere like ours. According to the study, published in the Astrophysical Journal, the exoplanet is likely have a hydrogen/helium-dominated atmosphere with high-altitude clouds and hazes. The researchers admit that it’s possible the planet has an atmosphere rich in molecules such water and methane, but they are not confident that the features they see in the light spectrum are real.

The team is planning follow-up observations to determine the atmosphere’s composition with more confidence. They plan to look at the planet again using an infrared telescope, which should allow them to assess if water and methane are there or not.

The planet, called GJ 3470b, orbits a red dwarf half the mass of the Sun. The star has a surface temperature of about 3,300°C (6,000°F) and the planet orbits around its star every three Earth days. Being so close to the star, the planet is quite hot and it is referred to as a warm-Neptune.


Dr Diana Dragomir, lead author of the research, said in a statement that “this detection brings us closer to understanding the nature of increasingly smaller exoplanets through the use of a novel approach which allows us to probe the atmospheres of exoplanets even if they are cloudy.” 

The study is the first high-confidence detection of an exoplanet atmosphere features using observations taken with only 1 meter (3.3 foot) and 2 meter (6.6 foot) telescopes, highlighting the importance of meter-class astronomy in increasing our understanding of the universe. 

spaceSpace and Physics
  • tag
  • atmosphere,

  • exoplanet,

  • rayleigh scattering.