[dropcap]A[/dropcap]t the end of one part of a star’s life, if it’s not massive enough to become a neutron star or black hole – which is the vast majority of stars – it will shed mass and eventually become a very dense type of star known as a white dwarf.
White dwarves are no longer capable of the nuclear fusion that sustains our Sun and most other stars. However, its residual thermal energy is enough to sustain heat for billions of years as it slowly dissipates.
Even white dwarves that are close in age to that of the universe still retain their heat.
It’s around these slowly dying stars that astronomers now think may show the first signs of life. At least, given the limits of our current technology. That’s the conclusion of researchers at the Harvard-Smithsonian Center for Astrophysics.
“In the quest for extraterrestrial biological signatures, the first stars we study should be white dwarfs,” said theorist Avi Loeb in a CfA press release.
So far, no planets have been found in the “habitable zone” of a white dwarf star – an orbit where liquid water could exist on the surface of the planet. However, the researchers believe that a survey of 500 or so dwarf stars could discover such a planet.
Once such a planet is discovered, the next step belongs to the James Webb Space Telescope, which will launch in 2018. The JWST will have equipment on it capable of determining the chemistry of the atmospheres of alien worlds based on the how the light of its star changes as it passes through.
The benefit of studying white dwarfs, though, is that they give off less light than other types of stars.
As a result, the astronomers demonstrated in their research that the JWST should be able to detect the presence of water vapor and oxygen in an atmosphere in just a few hours of observation.
For planets around other types of stars, such as red dwarfs, observation might take hundreds of hours.
“Although the closest habitable planet might orbit a red dwarf star, the closest one we can easily prove to be life-bearing might orbit a white dwarf,” said Loeb.
SOURCE: TEHRAN TIMES