When stars like our sun die, only an open nucleus remains – a white dwarf. A planet orbiting a white dwarf is a promising opportunity to determine whether life can survive the death of its star, according to researchers at Cornell University.
In a study published in Astrophysical Journal Letters, they show how NASA’s upcoming James Webb Space Telescope could find signatures of life on Earth-like planets orbiting white dwarfs.
A planet orbiting a small star produces strong atmospheric signals when its host star passes in front or “passes”. White dwarfs push this to the limit: they are 100 times smaller than our sun, almost as small as Earth, giving astronomers a rare opportunity to characterize rocky planets.
“If there are rocky planets around the white dwarfs, we could see signs of life on them over the next few years,” said correspondent Lisa Kalteneger, an associate professor of astronomy at the College of Arts and Sciences and director of the Carl Sagan Institute.
Co-author Ryan MacDonald, a research fellow at the institute, said the James Webb Space Telescope, due to launch in October 2021, is uniquely placed to find signatures on the life of rocky exoplanets.
“When it observes Earth-like planets orbiting white dwarfs, the James Webb Space Telescope can detect water and carbon dioxide within hours,” MacDonald said. “Two days of weather observation with this powerful telescope would allow the detection of gases with biosignatures, such as ozone and methane.”
The discovery of the first giant transiting planet orbiting a white dwarf (WD 1856 + 534b), announced in a separate article by co-author Andrew Vanderburg, an assistant professor at the University of Wisconsin, Madison, proves the existence of planets around the white dwarf. Kalteneger is the 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 that could sustain life could also exist in the inhabited areas of white dwarfs.
“We already know that giant planets can exist around white dwarfs, and evidence stretches for more than 100 years, showing rocky material polluting light from white dwarfs. There are certainly small rocks in white dwarfs,” MacDonald said. “The logical leap is to imagine a rocky planet like Earth orbiting a white dwarf.”
The researchers combined modern analysis techniques routinely used to detect gases in giant exoplanetary atmospheres with the Hubble Space Telescope with model atmospheres of white dwarf planets from previous Cornell research.
NASA’s exoplanet transit satellite is now looking for such rocky planets around white dwarfs. If and when one of these worlds is discovered, Kalteneger and her team have developed models and tools to identify signs of life in the planet’s atmosphere. The Webb Telescope may soon begin this search.
The consequences of finding signatures on the life of a planet orbiting a white dwarf are profound, Kalteneger said. Most stars, including our sun, will one day turn out to be white dwarfs.
“What if the star’s death isn’t the end of a lifetime?” she said. “Can life go on even after the sun dies? The signs of life on the planets orbiting white dwarfs will not only show the incredible tenacity of life, but perhaps a glimpse into our future.”
Astronomers could spot living signs orbiting long-dead stars
Lisa Kalteneger et al. The possibility of a white dwarf: Strong discoveries of molecules in exoplanetary atmospheres similar to Earth with the James Webb Space Telescope. Astrophysical Journal Letters, Volume 901, Number 1. DOI: 10.3847 / 2041-8213 / aba9d3
Provided by Cornell University
Quote: Can life survive after the death of a star? The web telescope can reveal the answer (2020, September 16), extracted on September 16, 2020 from https://phys.org/news/2020-09-life-survive-star-death-webb.html
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