Greenhouse Effect Could Extend Habitable Zone Planets near their
suns reap the benefits of light and heat, while those further
away must endure colder temperatures. But the new research
indicates that planets with hydrogen-rich atmospheres could
contain liquid at their surface even out to fifteen times the
distance between the Earth and the Sun. With a hydrogen
atmosphere, the greenhouse effect these planets could experience
would be sufficient to allow for liquid water on their surfaces,
despite their distant orbits. The area around a star in which
water can be liquid rather than ice is known as the habitable
zone. Sometimes called the "Goldilocks zone," it's just right -
not too hot (so the water doesn't evaporate) and not too cold
(so it won’t freeze). Typically, the distance calculated takes
into account a rocky body having an atmosphere made up of water
and carbon dioxide, the same greenhouse gases found on Earth.
"This is the kind of planet we know is habitable," explains
Raymond Pierrehumbert of the Un