Astronomers continue to hunt for alien life by pinpointing promising “Goldilocks zones,” or habitable zones, around host stars. Science Daily reports that scientists have analyzed different types of stars and modeled the different locations where life-hosting planets would have to sit and how long the planets could stay habitable for.
To host alien life, a planet would have to sit a perfect distance from its host star. It cannot be too hot or too cold — liquid water must be able to exist on the surface of the planet.
The “not too hot, not too cold” requirement led scientists to dub the habitable zone the “Goldilocks Zone.” Earth itself sits in such a zone, at a perfect distance from our own sun.
Earth sits in the habitable zone from our sun – not too hot like Mercury or Venus, and not too cold like Jupiter and Saturn.
Once our sun becomes a Red Giant…could a new habitable zone foster life? https://t.co/y8VXm0QEXN
— AGU's Eos (@AGU_Eos) May 16, 2016
The habitable zone is not set at the same distance around each host star in the universe. For example, if a star burns brighter and hotter than our sun, the habitable zone around that star would be further away than our earth’s distance to our sun.
Scientists also note that the position of the habitable zone can change as a star ages.
“When a star ages and brightens, the habitable zone moves outward and you’re basically giving a second wind to a planetary system.”
Researchers point out that in just a few billion years, the habitable zone around the Earth will change. Earth will no longer be able to host life, and Jupiter, Saturn, and Neptune potentially could.
“Earth, for example, has been in our sun’s habitable zone so far for about 4.5 billion years, and it has teemed with changing iterations of life. However, in a few billion years our sun will become a red giant, engulfing Mercury and Venus, turning Earth and Mars into sizzling rocky planets, and warming distant worlds like Jupiter, Saturn and Neptune — and their moons — in a newly established red giant habitable zone.”
Researchers explained that as a host star becomes a red giant and the habitable zone moves out slowly, “any initially frozen worlds would melt.” Scientists were optimistic about the possibility of “pre-existing subsurface life” becoming exposed to the atmosphere, where scientists could potentially detect it.
Thus, it is the “red giant stage” — the stage when a star transitions to a red giant — that many scientists are now excited about, according to Daily Mail.
“[T]he red giant stage may be akin to giving a ‘second wind’ to life in the stellar system.”
This type of life has been dubbed “alien life hiding in red giants.”
“With our new work, astronomers can compile a list of known red giants and use our model predictions, assuming that the stellar ages are approximately known.”
The red giant work was done by Ramses M. Ramirez and Lisa Kaltenegger of the Carl Sagan Institute. Their research, “Habitable Zones of Post-Main Sequence Stars,” was published in the Astrophysical Journal May 16.
Ramirez and Kaltinegger admitted to reporters that as the habitable zone moves outward, other developments can occur “that are not good for habitability.”
The researchers said that intense stellar winds can erode planetary atmospheres. They also pointed out that planets will move outward as the red giant star loses mass.
Nevertheless, Kaltinegger, and Ramirez were optimistic about the potential for thawed planets to host life, especially because they will remain thawed for a very long time as the habitable zone moves outward.
“Even with all of these things happening [stellar winds, etc.], we show that some planets can at least partially retain (if not completely retain) their atmospheres during the entirety of the red giant stage of stellar evolution…. Such thawed planets could stay warm up to half a billion years in the red giant habitable zone. That’s no small amount of time.”
— Do You Even Science? (@DoYouScience) May 16, 2016
[Image by Nasa/Getty Images]