Recent scientific advances have made discovering life on other planets outside our solar system a likely possibility.
Chris Impey, a University Distinguished Professor of Astronomy at the University of Arizona, was the keynote speaker at the LSU Undergraduate Research Conference on Oct. 14. His talk, “Water Worlds: The Search for Habitable Exoplanets,” detailed the probability of finding life elsewhere in the universe.
To find life on distant planets, scientists use spectroscopy to analyze light. The light’s wavelengths reflect the world’s physical properties, like which gases make up the planet’s atmosphere and if biomarkers are present. Scientists are looking for a few things when determining the likelihood of life: water, oxygen and ozone.
“Within five to 10 years, you will hear the announcement of life beyond Earth, and it will be by this method on an Earth-like exoplanet,” Impey said.
Once an exoplanet is discovered, scientists attempt to characterize it to determine if life can be sustained there. The planet must be found within the habitable zone of a star, meaning within an appropriate distance where liquid water can form and remain liquid.
Although there is no direct evidence of life existing on other planets, Impey said he is confident of the possibility due to a number of factors that favor a microorganism’s ability to survive. The ability of microbial life on Earth to withstand extreme conditions shows that if life could thrive here, before the Earth was fully formed, it could exist elsewhere in similar conditions.
Life began on Earth almost as soon as one imagines — about four billion years ago, when the planet was a heavily volcanic world. The places where life could be are abundant, Impey said.
“We think of the solar system as being the Earth and that’s it, but in the true inventory of possible habitability in locations, it’s actually a much larger thing than that,” he said.
Today, there are nearly 3,400 confirmed exoplanets. According to a simulation of inventory of water on terrestrial planets, most of them have more liquid water than Earth. People are limited in thinking of Earth as the only planet containing water, and therefore, life, Impey said.
“Earth as a water world is simply not special,” he said.
To find an exoplanet, scientists observe the planet’s host star and use doppler measurements of the star to look for a periodic wobble.
Since the first exoplanet was discovered in 1995, there’s been an “unprecedented rate of progress in detection limit,” which is due to the instrumentation and experimental design of equipment, Impey said. Scientists went from finding a handful of exoplanets to over 1,000 habitable planets.
Since the Kepler mission was launched in 2008, it has discovered thousands of previously unknown exoplanets. Kepler finds Earth-like transmitting planets by finding sun-like stars.
Scientists formulate the number of possible civilizations using the Drake Equation, which estimates the odds of finding intelligent life in the universe. The equation requires seven factors for computation, and the only one scientists remain unsure of is the biology, or how many planets have environments that could support life.
“I’m not going to take it as a given that life exists elsewhere, I’m just going to take it as a statistically probable statement,” Impey said.