Comparison of performances of CoRoT, Kepler and PLATO
These previous space missions will
leave a strong needfor a further mission aiming at establishing a
complete and unbiased statistical knowledge of exoplanetary systems.
Such is the goal of PLATO.
In particular, in its survey of more than 100,000 stars brighter than mV=11, PLATO will bring us the essential capability to characterize completely the stars orbited by the detected planets. This characterization will involve ground-based follow-up observations, but also asteroseismic analysis of these stars, using PLATO data. Such characterization will allow us to measure accurately the radii and masses of the detected planets, and will provide a reliable estimate of their ages.This is one of the most important advances of PLATO compared to CoRoT and Kepler, whose observing strategies are such that they will find planets mainly around faint and distant objects, making it very challenging -- if not impossible -- to study in detail the characteristics of the exoplanet's host stars. Also, due to the large distances to these stars, there is no hope for future direct imaging and spectroscopic investigation of the planets discovered by these missions, whereas PLATO should identify potential targets for future interferometric and coronographic space- and ground-based instruments.
Moreover, for this sample of 100,000 stars, similar in size as that of Kepler, PLATO will reach a noise level at least three times lower than the average level of noise of Kepler, and will therefore allow us to detect smaller planets in front of cool dwarf stars, or terrestrial planets in front of hotter and larger stars, thus significantly extending our knowledge of the statistics of exoplanetary systems.
In addition, PLATO is designed to detect terrestrial planets in the habitable zone down to about mV = 14, a performance very similar to that of Kepler. Due to the larger size of the surveyed field, PLATO will monitor about 400,000 stars down to this magnitude, extending by approximately a factor of four the sample of detected planetary systems over Kepler.
Also, the seismological observations of the proposed concept will give us the possibility to study stellar oscillations down to solar-like level for more than 100,000 stars, of all masses and ages. This is a considerable step forward compared to currently planned missions: it represents 1,000 times the stellar sample monitored by CoRoT, about 200 times that planned for the seismology programme of Kepler, and more than five times the sample that was planned for the Eddington mission.
This star sample represents a significant fraction of the targets to be observed by Gaia/RVS, and for which PLATO will provide an estimate of their age. The age determination, missing from the Gaia/RVS science, will nicely complete the space and velocity-space coordinates provided by Gaia, and bring us a full characterization of the surveyed galactic populations.
PLATO, by largely extending the results of CoRoT and Kepler in the area of exoplanet search and characterization, and in that of stellar structure and evolution, represents a natural step in our investigation of stellar and planetary system evolution. Filling and extending the important place in the European strategy that was left vacant by the cancellation of Eddington, PLATO will complete our knowledge of the statistics of extrasolar systems and stellar evolution. Hence, flying a mission like PLATO after CoRoT, Kepler and Gaia is a requirement for our understanding of stellar and planetary formation and evolution.
Finally, PLATO observation of bright and nearby stars will make the well-known problem of false alarms for planetary transit search techniques less severe. For instance, background eclipsing binaries, which usually dominate the false alarm problem, will constitute a much smaller difficulty: an eclipsing binary mimicking a planetary transit in front of a star with mV = 11 will need to be 100 times brighter than that mimicking a transit with the same depth for a mV = 16 star, and it can be shown that the probability of false alarm due to such an event will be 100 times lower.
In particular, in its survey of more than 100,000 stars brighter than mV=11, PLATO will bring us the essential capability to characterize completely the stars orbited by the detected planets. This characterization will involve ground-based follow-up observations, but also asteroseismic analysis of these stars, using PLATO data. Such characterization will allow us to measure accurately the radii and masses of the detected planets, and will provide a reliable estimate of their ages.This is one of the most important advances of PLATO compared to CoRoT and Kepler, whose observing strategies are such that they will find planets mainly around faint and distant objects, making it very challenging -- if not impossible -- to study in detail the characteristics of the exoplanet's host stars. Also, due to the large distances to these stars, there is no hope for future direct imaging and spectroscopic investigation of the planets discovered by these missions, whereas PLATO should identify potential targets for future interferometric and coronographic space- and ground-based instruments.
Moreover, for this sample of 100,000 stars, similar in size as that of Kepler, PLATO will reach a noise level at least three times lower than the average level of noise of Kepler, and will therefore allow us to detect smaller planets in front of cool dwarf stars, or terrestrial planets in front of hotter and larger stars, thus significantly extending our knowledge of the statistics of exoplanetary systems.
In addition, PLATO is designed to detect terrestrial planets in the habitable zone down to about mV = 14, a performance very similar to that of Kepler. Due to the larger size of the surveyed field, PLATO will monitor about 400,000 stars down to this magnitude, extending by approximately a factor of four the sample of detected planetary systems over Kepler.
Also, the seismological observations of the proposed concept will give us the possibility to study stellar oscillations down to solar-like level for more than 100,000 stars, of all masses and ages. This is a considerable step forward compared to currently planned missions: it represents 1,000 times the stellar sample monitored by CoRoT, about 200 times that planned for the seismology programme of Kepler, and more than five times the sample that was planned for the Eddington mission.
This star sample represents a significant fraction of the targets to be observed by Gaia/RVS, and for which PLATO will provide an estimate of their age. The age determination, missing from the Gaia/RVS science, will nicely complete the space and velocity-space coordinates provided by Gaia, and bring us a full characterization of the surveyed galactic populations.
PLATO, by largely extending the results of CoRoT and Kepler in the area of exoplanet search and characterization, and in that of stellar structure and evolution, represents a natural step in our investigation of stellar and planetary system evolution. Filling and extending the important place in the European strategy that was left vacant by the cancellation of Eddington, PLATO will complete our knowledge of the statistics of extrasolar systems and stellar evolution. Hence, flying a mission like PLATO after CoRoT, Kepler and Gaia is a requirement for our understanding of stellar and planetary formation and evolution.
Finally, PLATO observation of bright and nearby stars will make the well-known problem of false alarms for planetary transit search techniques less severe. For instance, background eclipsing binaries, which usually dominate the false alarm problem, will constitute a much smaller difficulty: an eclipsing binary mimicking a planetary transit in front of a star with mV = 11 will need to be 100 times brighter than that mimicking a transit with the same depth for a mV = 16 star, and it can be shown that the probability of false alarm due to such an event will be 100 times lower.