Ever since the first exo-planet, 51 Pegasi B, was detected in 1995, 770 exo-planets have been spotted. It is now time to study the environment of these planets. One of the proposed missions is ECHO, a space probe slated for launch between 2020 and 2022, reports Kalyan Ray
Are we indeed the only ones in the universe? This question remains the underlying objective of space explorations for gathering information about the solar system, earth's neighbours and the Milky Way. Many look-outs were aimed at finding a planet with conditions favourable to life as we know on earth.
The Goldilocks planet is yet to be found. Meanwhile, the explorations received a major thrust in 1995, with the discovery of the first exo-planet, 51 Pegasi B, in the constellation of Pegasus.
Since then, 770 exo-planets have been spotted, many of them in the last couple of years thanks to NASA's Kepler and Europe's CoROT space probe. Scientists feel the time has now come to take the next step - examining the environment of these exo-planets to check if life can thrive there.
"It is time to investigate the nature of the planets we find to understand how planets form and how they evolve. Many unexpected planets have questioned the view we had from the solar system alone. We need to understand what these planets are now, to be able to get a better understanding of planet formation and evolution," said Heike Rauer, a German Aerospace Centre scientist, who is putting together a mission to look at the atmosphere and interior composition of exo-planets around.
The first mission to study the atmosphere and composition of an exo-planet is off the drawing board. Named ECHO (extra-planet characterisation observatory), it is one of the proposed medium class missions, which the European Space Agency may fund in the next decade. If it receives the final nod from the ESA, the space probe carrying a 1.2 mt telescope would be launched between 2020 and 2022. A decision on the approval is expected by 2014 end.
"We want to see what exo-planets are made of and study the energy budget. New information will help us understand planetary evolution. We have identified 50-100 targets," Giovanna Tinetti, an astrophysicist at University College, London and principal scientist of ECHO told Deccan Herald on the sidelines of the recently concluded European Open Science Forum, 2012 at Dublin.
Tough task
Detection of exo-planets is an extremely difficult task. Because of very poor contrast, no image can be taken directly. "It is like capturing a candle placed next to a floodlit football stadium," said Don Pollacco, an astrophysicist at Queen's University, Belfast flagging the difficulties.
Nonetheless, few of them have been captured using techniques and instruments developed in the last two decades, providing new observational evidences that the Milky Way is rich with planetary systems. They provide scientists with an opportunity to determine if the solar system is unique and examine theories on the formation of planetary systems.
Broadly, three techniques - Doppler, transiting and micro-lensing - are used. The first one (Doppler) is the most successful one as 715 exo-planets out of 770 were either first spotted or their existence was corroborated using this technique.
Used by many observatories including Kepler, transiting came in handy for 239 cases while micro-lensing in which light from background stars is gravitationally bent by the planet, was useful only in 16 cases. There is a change in philosophy in exo-planet search, explained Rauer, one of the key scientists involved with PLATO - a planned mission that may replace COROT in future.
"Exo-planets surveys so far were optimised to detect them, but their individual parameters, like mass, radius, mean density, interior and atmospheric composition was not in the minds of people when designing these surveys. We now propose new detection surveys aiming at these investigations," she said.
A rich haul
There is simply no stopping exo-planet discovery. Last week, NASA's Spitzer Space Telescope detected what they believed is a planet two-thirds the size of earth. The exo-planet candidate, UCF-1.01, is located a mere 33 light-years away, making it possibly the nearest world to our solar system that is smaller than our home planet.
The hot new planetary candidate was found unexpectedly. While studying a Neptune-sized exo-planet GJ 436b, already known to exist around a red-dwarf star, astronomers noticed slight dips in the amount of infrared light streaming from the star, separate from dips caused by GJ 436b. A review showed dips were periodic, suggesting a second planet might be blocking out a small fraction of the star's light.
This technique relies on planetary transits to detect exo-planets. The duration of a transit and the small decrease in the amount of light registered reveals basic properties of an exo-planet, such as its size and distance from its star. In UCF-1.01's case, its diameter would be approximately 8,400 kilometers, or two-thirds that of earth. UCF-1.01 would revolve quite tightly around GJ 436, at about seven times the distance of the earth from the moon, with its "year" lasting only 1.4 earth days. Given this proximity to its star, far closer than the planet Mercury is to our Sun, the exo-planet's surface temperature would be almost 600 degrees Celsius.
Ground based telescopes are also being used to investigate extra-solar planets. Last month, an international team used a Very Large Telescope to catch the faint glow from the planet Tau Boötis b, one of the first exo-planets discovered in 1996. They studied the planet's atmosphere and found that the planet's atmosphere seems to be cooler higher up, the opposite of what was expected.
"This study shows potential of current and future ground-based telescopes. One day we may even find evidence for biological activity on earth-like planets in this way," said Ignas Snellen at Leiden Observatory, the Netherlands. The search for biological markers is on the radar of future space-probes too.
Are we indeed the only ones in the universe? This question remains the underlying objective of space explorations for gathering information about the solar system, earth's neighbours and the Milky Way. Many look-outs were aimed at finding a planet with conditions favourable to life as we know on earth.
The Goldilocks planet is yet to be found. Meanwhile, the explorations received a major thrust in 1995, with the discovery of the first exo-planet, 51 Pegasi B, in the constellation of Pegasus.
Since then, 770 exo-planets have been spotted, many of them in the last couple of years thanks to NASA's Kepler and Europe's CoROT space probe. Scientists feel the time has now come to take the next step - examining the environment of these exo-planets to check if life can thrive there.
"It is time to investigate the nature of the planets we find to understand how planets form and how they evolve. Many unexpected planets have questioned the view we had from the solar system alone. We need to understand what these planets are now, to be able to get a better understanding of planet formation and evolution," said Heike Rauer, a German Aerospace Centre scientist, who is putting together a mission to look at the atmosphere and interior composition of exo-planets around.
The first mission to study the atmosphere and composition of an exo-planet is off the drawing board. Named ECHO (extra-planet characterisation observatory), it is one of the proposed medium class missions, which the European Space Agency may fund in the next decade. If it receives the final nod from the ESA, the space probe carrying a 1.2 mt telescope would be launched between 2020 and 2022. A decision on the approval is expected by 2014 end.
"We want to see what exo-planets are made of and study the energy budget. New information will help us understand planetary evolution. We have identified 50-100 targets," Giovanna Tinetti, an astrophysicist at University College, London and principal scientist of ECHO told Deccan Herald on the sidelines of the recently concluded European Open Science Forum, 2012 at Dublin.
Tough task
Detection of exo-planets is an extremely difficult task. Because of very poor contrast, no image can be taken directly. "It is like capturing a candle placed next to a floodlit football stadium," said Don Pollacco, an astrophysicist at Queen's University, Belfast flagging the difficulties.
Nonetheless, few of them have been captured using techniques and instruments developed in the last two decades, providing new observational evidences that the Milky Way is rich with planetary systems. They provide scientists with an opportunity to determine if the solar system is unique and examine theories on the formation of planetary systems.
Broadly, three techniques - Doppler, transiting and micro-lensing - are used. The first one (Doppler) is the most successful one as 715 exo-planets out of 770 were either first spotted or their existence was corroborated using this technique.
Used by many observatories including Kepler, transiting came in handy for 239 cases while micro-lensing in which light from background stars is gravitationally bent by the planet, was useful only in 16 cases. There is a change in philosophy in exo-planet search, explained Rauer, one of the key scientists involved with PLATO - a planned mission that may replace COROT in future.
"Exo-planets surveys so far were optimised to detect them, but their individual parameters, like mass, radius, mean density, interior and atmospheric composition was not in the minds of people when designing these surveys. We now propose new detection surveys aiming at these investigations," she said.
A rich haul
There is simply no stopping exo-planet discovery. Last week, NASA's Spitzer Space Telescope detected what they believed is a planet two-thirds the size of earth. The exo-planet candidate, UCF-1.01, is located a mere 33 light-years away, making it possibly the nearest world to our solar system that is smaller than our home planet.
The hot new planetary candidate was found unexpectedly. While studying a Neptune-sized exo-planet GJ 436b, already known to exist around a red-dwarf star, astronomers noticed slight dips in the amount of infrared light streaming from the star, separate from dips caused by GJ 436b. A review showed dips were periodic, suggesting a second planet might be blocking out a small fraction of the star's light.
This technique relies on planetary transits to detect exo-planets. The duration of a transit and the small decrease in the amount of light registered reveals basic properties of an exo-planet, such as its size and distance from its star. In UCF-1.01's case, its diameter would be approximately 8,400 kilometers, or two-thirds that of earth. UCF-1.01 would revolve quite tightly around GJ 436, at about seven times the distance of the earth from the moon, with its "year" lasting only 1.4 earth days. Given this proximity to its star, far closer than the planet Mercury is to our Sun, the exo-planet's surface temperature would be almost 600 degrees Celsius.
Ground based telescopes are also being used to investigate extra-solar planets. Last month, an international team used a Very Large Telescope to catch the faint glow from the planet Tau Boötis b, one of the first exo-planets discovered in 1996. They studied the planet's atmosphere and found that the planet's atmosphere seems to be cooler higher up, the opposite of what was expected.
"This study shows potential of current and future ground-based telescopes. One day we may even find evidence for biological activity on earth-like planets in this way," said Ignas Snellen at Leiden Observatory, the Netherlands. The search for biological markers is on the radar of future space-probes too.