Another key finding led by Kepler was that 20 percent to 50 percent of all the stars visible in the night sky may potentially have Earth-like planets orbiting in habitable zones
. The telescope stopped functioning in 2018 after losing its fuel.A
A Penn State team built the Habitable Zone
Planet Finder, an instrument to search for low-mass planets around cool stars, which recently began science operations at the Hobby-Eberly Telescope, of which Penn State is a founding partner.
As this happened, the (https://www.ibtimes.com/nasa-discovers-3-new-worlds-73-light-years-away-are-they-potentially-habitable-2809788) habitable zone
surrounding the Sun moved outward.
Diana Kossakowski, from the Max Planck Institute for Astronomy in Heidelberg - who co-authored the paper in Astronomy and Astrophysics - said: "GJ 357 d is located within the outer edge of its star's habitable zone
, where it receives about the same amount of stellar energy from its star as Mars does from the Sun.
"Mars is in the habitable zone
in our solar system, but its axial tilt has been very unstable - varying from zero to 60 degrees," said Georgia Tech Assistant Professor Gongjie Li, who led the study together with graduate student Yutong Shan from the Harvard-Smithsonian Center for Astrophysics.
"Now that we have created a database of the known giant planets in the habitable zone
of their star, observations of the best candidates for hosting potential exomoons will be made to help refine the expected exomoon properties," said Michelle Hill, an undergraduate student at the University of Southern Queensland.
"While in the majority of investigated systems the presence of the gas 'giants' shrank the habitable zone
, they still left sufficient room for habitable Earth-like planets to be there," said Georgakarakos.
This artist rendering provided by NASA/JPL-Caltech shows some of the 219 new planet candidates, 10 of which are near-Earth size and in the habitable zone
of their star identified by NASA's Kepler space telescope.
Not every planet tucked safely inside the habitable zone
is necessarily life-friendly.
"It's awe-inspiring to consider that this planet has spent six billion years in the habitable zone
of its star, longer than Earth.
Designed to survey a portion of the Milky Way to discover extrasolar planets in or near the habitable zone
, Kepler's sole instrument is a photometer.
But a new study indicates that "habitable zone
" planets with two to four times the Earth's mass may be even better at establishing and maintaining oceans.