Scientists are trying to detect extraterrestrial life in dying stars. Even dying stars could host planets with life - and if such life exists, we might be able to detect it within the next decade. This encouraging result comes from a new theoretical study of Earth-like planets orbiting white dwarf stars.
Researchers found that we could detect oxygen in the atmosphere of a white dwarf's planet much more easily than for an Earth-like planet orbiting a Sun-like star. Future evidence for extraterrestrial life might come from dying stars rather than "vying stars."
"In the quest for extraterrestrial biological signatures, the first stars we study should be white dwarfs," said Avi Loeb, theorist at the Harvard-Smithsonian Center for Astrophysics (CfA) and director of the Institute for Theory and Computation, according to the February 25, 2013 news release from the Harvard-Smithsonian Center for Astrophysics, "Future evidence for extraterrestrial life might come from dying stars."
When a star like the Sun dies, it puffs off its outer layers, leaving behind a hot core called a white dwarf. A typical white dwarf is about the size of Earth. It slowly cools and fades over time, but it can retain heat long enough to warm a nearby world for billions of years.
Since a white dwarf is much smaller and fainter than the Sun, a planet would have to be much closer in to be habitable with liquid water on its surface. A habitable planet would circle the white dwarf once every 10 hours at a distance of about a million miles.
Stars eventually swell and engulf their orbiting planets
Every object in the universe is subject to entropy, growing old and swelling up, engulfing nearby objects. If people are on a planet orbiting a sun at the end of its lifespan, they had better get off and inhabit a planet with a young star, if they're technically advanced enough and have the energy and time. It's all about time to develop the technology.
What happens is that before a star becomes a white dwarf it swells into a red giant, engulfing and destroying any nearby planets. Therefore, a planet would have to arrive in the habitable zone after the star evolved into a white dwarf. A planet could form from leftover dust and gas (making it a second-generation world), or migrate inward from a larger distance.
If planets exist in the habitable zones of white dwarfs, we would need to find them before we could study them. The abundance of heavy elements on the surface of white dwarfs suggests that a significant fraction of them have rocky planets. Loeb and his colleague Dan Maoz (Tel Aviv University) estimate that a survey of the 500 closest white dwarfs could spot one or more habitable Earths.
A transit search is the best way to find planets with life
The best method for finding such planets is a transit search - looking for a star that dims as an orbiting planet crosses in front of it. Since a white dwarf is about the same size as Earth, an Earth-sized planet would block a large fraction of its light and create an obvious signal.
More importantly, we can only study the atmospheres of transiting planets. When the white dwarf's light shines through the ring of air that surrounds the planet's silhouetted disk, the atmosphere absorbs some starlight. This leaves chemical fingerprints showing whether that air contains water vapor, or even signatures of life, such as oxygen.
Astronomers are particularly interested in finding oxygen because the oxygen in the Earth's atmosphere is continuously replenished, through photosynthesis, by plant life. Were all life to cease on Earth, our atmosphere would quickly become devoid of oxygen, which would dissolve in the oceans and oxidize the surface. Thus, the presence of large quantities of oxygen in the atmosphere of a distant planet would signal the likely presence of life there.
The media is touting the latest of NASA's James Webb Space Telescope (JWST), scheduled for launch by the end of this decade
NASA's James Webb Space Telescope (JWST), scheduled for launch by the end of this decade, promises to sniff out the gases of these alien worlds. Loeb and Maoz created a synthetic spectrum, replicating what JWST would see if it examined a habitable planet orbiting a white dwarf. They found that both oxygen and water vapor would be detectable with only a few hours of total observation time.
"JWST offers the best hope of finding an inhabited planet in the near future," explained Maoz in the February 25, 2013 news release, "Future evidence for extraterrestrial life might come from dying stars." Recent research by CfA astronomers Courtney Dressing and David Charbonneau showed that the closest habitable planet is likely to orbit a red dwarf star (a cool, low-mass star undergoing nuclear fusion).
Since a red dwarf, although smaller and fainter than the Sun, is much larger and brighter than a white dwarf, its glare would overwhelm the faint signal from an orbiting planet's atmosphere. The James Webb Space Telescope (JWST) would have to observe hundreds of hours of transits to have any hope of analyzing the atmosphere's composition. "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, according to the news release.
The scientists' paper has been accepted for publication in the Monthly Notices of the Royal Astronomical Society and is available online. Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe. Also check out the news, Supermassive black hole spins super-fast and The birth of a giant planet?
Is a new planet in the process of forming as Earth scientists watch its 'embryology'?
Astronomers using ESO's Very Large Telescope recently have obtained what is likely the first direct observation of a forming planet still embedded in a thick disc of gas and dust. If confirmed, this discovery will greatly improve our understanding of how planets form and allow astronomers to test the current theories against an observable target. Space seems to be continuously 'pregnant' with new planets and stars forming and black holes that process them down and spit them out to form new planets and stars all over again.
Researchers were surprised to find what seems to be a planet in the process of being formed, still embedded in the disc of material around the young star. An international team led by Sascha Quanz (ETH Zurich, Switzerland) observed the still-forming planet. The candidate planet would be a gas giant similar to Jupiter. “So far, planet formation has mostly been a topic tackled by computer simulations,” says Sascha Quanz in the February 28, 2013 news release, The birth of a giant planet? “If our discovery is indeed a forming planet, then for the first time scientists will be able to study the planet formation process and the interaction of a forming planet and its natal environment empirically at a very early stage.”
On another note, people want to know more news about what the U.S. Naval Research laboratory physicists are doing in the Earth's upper atmosphere with clouds. Check out the latest news on HAARP, "NRL scientists produce densest artificial ionospheric plasma clouds using HAARP."