When stars like our sun die, all that’s left is an exposed core, a white dwarf. A planet orbiting a white dwarf represents a promising opportunity to determine whether life can survive the death of its star, according to Cornell University researchers.
In a study published in Letters from astrophysics journals, show how NASA’s upcoming James Webb Space Telescope could find traces of life on Earth-like planets orbiting white dwarfs.
A planet orbiting a small star produces strong atmospheric signals when it passes in front of, or “transits,” its host star. White dwarfs push this to the extreme: they are 100 times smaller than our Sun, almost as large as the Earth, giving astronomers a rare opportunity to characterize rocky planets.
“If rocky planets exist around white dwarfs, we could spot signs of life on them in the next few years,” said corresponding author Lisa Kaltenegger, associate professor of astronomy at the College of Arts and Sciences and director of the Carl Sagan Institute.
Lead co-author Ryan MacDonald, a research associate at the institute, said the James Webb Space Telescope, scheduled to launch in October 2021, is in a unique position to find the signatures of life on rocky exoplanets.
“When Earth-like planets are observed orbiting white dwarfs, the James Webb Space Telescope can detect water and carbon dioxide in a matter of hours,” MacDonald said. “Two days of observation with this powerful telescope would allow the discovery of bio-signature gases, such as ozone and methane.”
The discovery of the first transiting giant planet orbiting a white dwarf (WD 1856 + 534b), announced in a separate paper, led by co-author Andrew Vanderburg, assistant professor at the University of Wisconsin, Madison, proves the existence of planets around the white dwarfs. Kaltenegger is also a co-author of this article.
This planet is a gas giant and therefore unable to sustain life. But its existence suggests that smaller rocky planets, which could support life, could also exist in the habitable zones of white dwarfs.
“We now know that giant planets may exist around white dwarfs, and evidence goes back over 100 years that shows light-polluting rock material from white dwarfs. There are certainly small rocks in white dwarf systems,” MacDonald said. . “It is a logical leap to imagine a rocky planet like Earth orbiting a white dwarf.”
The researchers combined state-of-the-art analysis techniques routinely used to detect gas in the atmospheres of giant exoplanets with the Hubble Space Telescope with model atmospheres of white dwarf planets from previous Cornell research.
NASA’s Transiting Exoplanet Survey Satellite is now looking for such rocky planets around white dwarfs. If and when one of these worlds is found, Kaltenegger and his team have developed the models and tools to identify signs of life in the planet’s atmosphere. The Webb telescope may soon begin this search.
The implications of finding traces of life on a planet orbiting a white dwarf are profound, Kaltenegger said. Most stars, including our sun, will one day end up as white dwarfs.
“What if the star’s death wasn’t the end of life?” she said. “Could life continue, even once our sun is dead? The signs of life on the planets orbiting white dwarfs would not only show the incredible tenacity of life, but perhaps also a glimpse into our future.”
Astronomers could spot signs of life orbiting long-dead stars
Lisa Kaltenegger et al. The White Dwarf Opportunity: Robust Detection of Molecules in Earth-Like Atmospheres of Exoplanets with the James Webb Space Telescope. The Astrophysical Journal Letters, Volume 901, number 1. DOI: 10.3847 / 2041-8213 / aba9d3
Can life survive the death of a star? Webb Telescope May Reveal Answer (2020, September 16)
recovered on September 17, 2020
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