CoRoT
CNES / ESA | ||
COSPAR ID | 2006-063A | |
---|---|---|
SATCAT no. | 29678 | |
Website | corot | |
Mission duration | Planned: 2.5 + 4 years Final: 7 years, 5 months, 20 days | |
Spacecraft properties | ||
Manufacturer | CNES Thales Alenia Space | |
Launch mass | 630 kg (1,390 lb) | |
Payload mass | 300 kg (660 lb) | |
Dimensions | 2 m × 4 m (6.6 ft × 13.1 ft) | |
Power | ≈380 W | |
Start of mission | ||
Launch date | 27 December 2006, 14:24 Soyuz 2.1b Fregat | |
Launch site | Baikonur LC-31/6 | |
Contractor | Arianespace Starsem | |
End of mission | ||
Disposal | Decommissioned | |
Deactivated | 17 June 2014, 10:27[1] | UTC|
Orbital parameters | ||
Reference system | Semi-major axis 7,123 km (4,426 mi)[2] | |
Eccentricity | 0.0203702[2] | |
Perigee altitude | 607.8 km (377.7 mi)[2] | |
Apogee altitude | 898.1 km (558.1 mi)[2] | |
Inclination | 90.0336 degrees[2] | |
Period | 99.7 minutes[2] | |
RAAN | 13.64 degrees[2] | |
Argument of perigee | 148.21 degrees[2] | |
Mean anomaly | 213.16 degrees[2] | |
Mean motion | 14.44 rev/day[2] | |
Epoch | 8 March 2016, 11:58:39 UTC[2] | |
Revolution no. | 47715 | |
Main telescope | ||
Type | Visible light | |
CoRoT (French: Convection, Rotation et Transits planétaires; English: Convection, Rotation and planetary Transits) was a
Among the notable discoveries was CoRoT-7b, discovered in 2009 which became the first exoplanet shown to have a rock or metal-dominated composition.
CoRoT was launched at 14:28:00
Overview
Spacecraft design
The CoRoT optical design minimized stray light coming from the Earth and provided a
The four CCD detectors are model 4280 CCDs provided by E2V Technologies. These CCDs are frame-transfer, thinned, back-illuminated designs in a 2,048 by 2,048 pixel array. Each pixel is 13.5 μm × 13.5 μm in size which corresponds to an angular pixel size of 2.32 arcsec. The CCDs are cooled to −40 °C (233.2 K; −40.0 °F). These detectors are arranged in a square pattern with two each dedicated to the planetary detection and asteroseismology. The data output stream from the CCDs are connected in two chains. Each chain has one planetary detection CCD and one asteroseismology CCD. The field of view for planetary detection is 3.5°.[14] The satellite, built in the Cannes Mandelieu Space Center, had a launch mass of 630 kg, was 4.10 m long, 1.984 m in diameter and was powered by two solar panels.[10]
Mission design
This section needs to be updated.(May 2016) |
The satellite observed perpendicular to its orbital plane, meaning there were no Earth occultations, allowing up to 150 days of continuous observation. These observation sessions, called "Long Runs", allowed detection of smaller and long-period planets. During the remaining 30 days between the two main observation periods, CoRoT observed other patches of sky for a few weeks long "Short Runs", in order to analyze a larger number of stars for the asteroseismic program. After the loss of half the field of view due to failure of Data Processing Unit No. 1 in March 2009, the observation strategy changed to 3 months observing runs, in order to optimize the number of observed stars and detection efficiency.
In order to avoid the Sun entering in its field of view, during the northern summer CoRoT observed in an area around
- IRa01, from 18 January 2007 to 3 April 2007 – 9,879 stars observed;
- SRc01, from 3 April 2007 to 9 May 2007 – 6,975 stars observed;
- LRc01, from 9 May 2007 to 15 October 2007 – 11,408 stars observed;
- LRa01, from 15 October 2007 to 3 March 2008 – 11,408 stars observed;
- SRa01, from 3 March 2008 to 31 March 2008 – 8,150 stars observed;
- LRc02, from 31 March 2008 to 8 September 2008 – 11,408 stars observed;
- SRc02, from 8 September 2008 to 6 October 2008 – 11,408 stars observed;
- SRa02, from 6 October 2008 to 12 November 2008 – 10,265 stars observed;
- LRa02, from 12 November 2008 to 30 March 2009 – 11,408 stars observed;
- LRc03, from 30 March 2009 to 2 July 2009 – 5,661 stars observed;
- LRc04, from 2 July 2009 to 30 September 2009 – 5,716 stars observed;
- LRa03, from 30 September 2009 to 1 March 2010 – 5,289 stars observed;
- SRa03, from 1 March 2010 to 2 April 2010;
- LRc05, from 2 April 2010 to 5 July 2010;
- LRc06, from 5 July 2010 to 27 September 2010;
- LRa04, from 27 September 2010 to 16 December 2010;
- LRa05, from 16 December 2010 to 5 April 2011;
- LRc07, from 5 April 2011 to 30 June 2011;
- SRc03, from 1 July 2011 to 5 July 2011 – a run made to reobserve the transit of CoRoT-9b;
- LRc08, from 6 July 2011 to 30 September 2011;
- SRa04, from 30 September 2011 to 28 November 2011;
- SRa05, from 29 November 2011 to 9 January 2012;
- LRa06, from 10 January 2012 to 29 March 2012 – a run dedicated to reobservation of CoRoT-7b;
- LRc09, from 10 April 2012 to 5 July 2012;
- LRc10, from 6 July 2012 to 1 November 2012 - interrupted by the fatal failure which ended the mission.
The spacecraft monitored the brightness of stars over time, searching for the slight dimming that happens in regular intervals when planets
CoRoT also studied asteroseismology. It can detect luminosity variations associated with acoustic pulsations of stars. This phenomenon allows calculation of a star's precise mass, age and chemical composition and will aid in comparisons between the sun and other stars. For this program, in each field of view there was one main target star for asteroseismology as well as up to nine other targets. The number of observed targets have dropped to half after the loss of Data Processing Unit No. 1.
The mission began on 27 December 2006 when a Russian
The mission's cost amounted to €170 million, of which 75% was paid by the French space agency CNES and 25% was contributed by Austria, Belgium, Germany, Spain, Brazil and the European Space Agency (ESA).[21]
Development
The primary contractor for the construction of the CoRoT vehicle was CNES,
Potential
Before the beginning of the mission, the team stated with caution that CoRoT would only be able to detect planets few times larger than Earth or greater, and that it was not specifically designed to detect
CoRoT should be assumed to detect a small percentage of planets within the observed star fields, due to the low percentage of exoplanets that would transit from the angle of observation of the
Failure of Data Processing Unit No. 1
On 8 March 2009 the satellite suffered a loss of communication with Data Processing Unit No. 1, processing data from one of the two photo-detector chains on the spacecraft. Science operations resumed early April with Data Processing Unit No. 1 offline while Data Processing Unit No. 2 operating normally. The loss of photo-detector chain number 1 results in the loss of one CCD dedicated to asteroseismology and one CCD dedicated to planet detection. The field of view of the satellite is thus reduced by 50%, but without any degradation of the quality of the observations. The loss of channel 1 appears to be permanent.[23]
Follow-up program
The rate of discoveries of transiting planets is dictated by the need of ground-based, follow-up observations, needed to verify the planetary nature of the transit candidates. Candidate detections have been obtained for about 2.3% of all CoRoT targets, but finding
Interesting transiting planets could be further followed-up with the infrared Spitzer Space Telescope, to give an independent confirmation at a different wavelength and possibly detect reflected light from the planet or the atmospheric compositions. CoRoT-7b and CoRoT-9b have already been observed by Spitzer.
Papers presenting the results of follow-up operations of planetary candidates in the IRa01,[27] LRc01,[28] LRa01,[29] SRc01[30] fields have been published. In April 2019, a summary of the exoplanet search results have been published,[31] with 37 planets and brown dwarves confirmed, and a further one hundred planet candidates still to be verified. Sometimes the faintness of the target star or its characteristics, such as a high rotational velocity or strong stellar activity, do not allow to determine unambiguously the nature or the mass of the planetary candidate.
Discoveries
Asteroseismology and stellar physics
Stars vibrate according to many different pulsation modes in much the same way that musical instruments emit a variety of sounds. Listening to an air on the guitar does not leave any doubt as to the nature of the instrument, and an experienced musician can even deduce the cords' material and tension. Similarly, stellar pulsation modes are characteristic of global stellar properties and of the internal physical conditions. Analyzing these modes is thus a way of probing stellar interiors to infer stellar chemical composition, rotation profiles and internal physical properties such as temperatures and densities. Asteroseismology is the science which studies the vibration modes of a star. Each of these modes can be mathematically represented by a spherical harmonic of degree l and azimuthal order m. Some examples are presented here below with a color scheme in which blue (red) indicates contracting (expanding) material. The pulsation amplitudes are highly exaggerated.
When applied to the Sun, this science is called
At the beginning of the mission, two out of four CCDs were assigned to asteroseismic observations of bright stars (apparent magnitude 6 to 9) in the so-called seismo field while the other CCDs were reserved for exoplanet hunting in the so-called exo field. Albeit with a lower
Discoveries were numerous,
Extension of the chemically mixed zone in main sequence stars
Above the convective core where mixing of chemicals is instantaneous and efficient, some layers can be affected by partial or total mixing during the main sequence phase of evolution. The extent of this extra mixed zone as well as the mixing efficiency are, however, difficult to assess. This additional mixing has very important consequences since it involves longer time scales for nuclear burning phases and may in particular affect the value of the stellar mass at the transition between those stars which end up their life as white dwarfs and those which face a final supernova explosion. The impact on the chemical evolution of the galaxy is obvious. Physical reasons for this extra-mixing are various, either a mixing induced by internal rotation or a mixing resulting from convective bubbles crossing the convective core boundary to enter the radiative zone where they finally lose their identity (overshooting), or even some other poorly known processes.
- Solar-like stars: The solar-like star HD 49933 is illustrative of this extra-mixing problem.[41] Its convective envelope is responsible for the presence of solar-like oscillations. Comparing the observed frequency spectrum with that obtained from theoretical models of 1.19 Mʘ computed with and without additional mixing clearly excludes a model without extra mixing.
- Sub-giant stars: Such an additional mixing also affects the structure of more evolved
- SPB stars: More massive SPB (Slowly Pulsating B) stars show a frequency spectrum dominated by high order gravity modes excited by the κ mechanism at work in layers where ionizations of iron group elements produces an opacity peak. In such stars, the convective core is surrounded by a region of varying chemical composition, the so-called μ-gradient region, left by the progressive withdrawal of the convective core as hydrogen is transformed into helium. This region is rather thin and constitutes a sharp transition region, which induces a very subtle signature in the gravity modes frequency spectrum. Instead of a constant period spacing found in a homogeneous stellar model, periodic deviations from this constant value are expected in models affected by a sharp transition region. Moreover, the period of the deviations is directly related to the precise location of the sharp transition.[43] This phenomenon has been detected in two hybrid B stars (showing at the same time acoustic β Cephei and gravity SPB modes): (1) HD 50230[39] where an extra-mixing with a somewhat smooth shape is clearly required in the modeling and (2) HD 43317.[44]
Structure of the superficial stellar layers
- Transition layers in stellar envelopes: Transition layers such as the helium ionization region or the lower boundary of the convective envelope in low mass and red giant stars also affect frequency spectra. In a structure devoid of such discontinuities, high order acoustic modes obey some regularities in their frequency distribution (large frequency separation, second difference...). Transition zones introduce periodic deviations with respect to these regularities and the periods of the deviations are directly related to the precise location of the transition zones. These deviations were predicted by theory and were first observed in the Sun.[45] Thanks to CoRoT they were also detected in the solar-like star HD 49933[46] and also in the red giant star HD 181907.[47] In both cases the location of the helium ionization zone could be accurately derived.
- Amplitudes and line widths in solar-like oscillation spectra: One of the major successes of the CoRoT space mission has definitely been the detection of solar-like oscillations in stars slightly hotter than the Sun.[33] As was previously done for the Sun, measurements of amplitudes and line widths in their frequency spectra resulted in new constraints in the modeling of stochastic excitations of acoustic modes by turbulent convection. The frequency spectrum of HD 49933[48] was confronted to the stochastic excitation model developed by Samadi et al.[49][50] Except at high frequencies, a good agreement can be reached by adopting a metallicity ten times smaller than the solar metallicity. With the solar value on the contrary, disagreements in amplitudes can reach a factor 2 at low frequencies.
- Granulation: The presence of granulation was detected in the frequency spectrum of HD 49933. Analyses have been done with 3D hydrodynamical model atmospheres computed at solar and ten times smaller than solar metallicities.[51] Here again the model with the lowest metallicity shows up to be closer to the observations although significant disagreements still remain.
Red giants and chemical evolution of this galaxy
Following exhaustion of hydrogen in the core, the overall stellar structure drastically changes. Hydrogen burning now takes place in a narrow shell surrounding the newly processed helium core. While the helium core quickly contracts and heats up, the layers above the hydrogen-burning shell undergo important expansion and cooling. The star becomes a
Whether RGB or RC, these stars all have an extended convective envelope favorable to the excitation of solar-like oscillations. A major success of CoRoT has been the discovery of radial and long-lived non-radial oscillations in thousands of red giants in the exo field.[34] For each of them, the frequency at maximum power νmax in the frequency spectrum as well as the large frequency separation between consecutive modes Δν could be measured,[52][53] defining a sort of individual seismic passport.
- Red giant population in this galaxy: Introducing these seismic signatures, together with an estimation of the effective temperature, in the scaling laws relating them to the global stellar properties,Keplerobservations (green points).
- Age-metallicity relation in this galaxy: The age of a red giant is closely related to its former main sequence lifetime, which is in turn determined by its mass and metallicity. Knowing the mass of a red giant amounts to knowing its age. If the metallicity is known the uncertainty in age does not exceed 15%! Observational missions such as APOGEE (Apache Point Observatoty Galactic Evolution Environment) whose goal is to measure metallicities for 100 000 red giants in this galaxy, GALAH (Galactic Archaeology with HERMES) and GAIA (Global Astrometric Interferometer for Astrophysics) could of course widely benefit from these seismic gravities with the ultimate output of establishing the age-metallicity relation in this galaxy. Asteroseismology has crossed the doorstep of the structure and chemical evolution of this galaxy.[57]
- Seismic signatures and extension of mixed zones during central hydrogen and helium burning: Increasing even further the scrutiny in analyzing the CoRoT[58] and Kepler[59] frequency spectra of red giants brought new important discoveries. Small and subtle differences in seismic signatures allow us to distinguish RGB from RC stars notwithstanding their similar luminosities. This is now theoretically confirmed thanks to elaborate red giant modeling.[60] The period spacings of gravity-dominated modes are expected to be especially meaningful. Their detection for a large number of red giants could give us clues to establishing the extent of the extra-mixed region above the convective core during core hydrogen burning, but also the extent of the extra-mixed region during core helium burning, both mixing processes being a priori totally unrelated.[61]
Massive stars
Massive variable main sequence stars have frequency spectra dominated by acoustic modes excited by the
- β Cephei stars: Seismic analyses of ν Eridani.[71][72] It would be extremely interesting to establish a relation between the extent of this zone and the rotation velocity and/or the magnetic field of the star. Seismic analysis of V2052 Ophiuchi[73]shows that this star although rapidly rotating, which would favor extra-mixing, could be devoid of such a region. The magnetic field detected in this star could be the reason of this lack of extra-mixing.
- Be stars: Late Be type stars HD 181231 and HD 175869 are very rapid rotators, about 20 times more rapid than the Sun. Their seismic analysis seems to require a centrally mixed zone about 20% larger than what is expected from convection only.[74] Another Be star, HD 49330, had a very exciting surprise in store. Observed by CoRoT during an outburst of matter towards its circumstellar disk, which is typical of such stars, its frequency spectrum suffered drastic changes. Firstly dominated by acoustic modes the spectrum showed the appearance of gravity modes with amplitudes strictly in line with the outburst.[75] Such a link between the nature of the excited modes and a dynamical phenomenon is of course a gold mine in the quest for the internal structure of Be stars.
- O stars: Many O stars have been observed by CoRoT. Among them HD 46150 and HD 46223 (members of the galactic cluster NGC 2264) and HD 46966 (member of the OB association Mon OB2) do not seem to pulsate, which is in agreement with stellar modeling of stars with similar global parameters.Plaskett's star HD 47129 on the contrary shows a peak with six harmonics in the frequency range expected from theoretical modeling.[77]
Another unexpected CoRoT discovery was the presence of solar-like oscillations in massive stars. The small convective shell related to the opacity peak resulting from the ionization of iron group elements at about 200 000 K (iron opacity peak) could indeed be responsible for the stochastic excitation of acoustic modes like those observed in the Sun.
- V1449 Aquilae (HD 180642): This CoRoT target is a β Cephei star whose frequency spectrum reveals high frequency and very small amplitude acoustic modes. A careful analysis has shown that they were solar-like oscillations excited by turbulent bubbles origination from this convective iron opacity peak zone or even from the convective core.κ mechanism acting in the iron opacity peak zone were present side by side in the same star with pulsations stochastically excited by this very same zone. This is the reason why Kevin Belkacem, main discoverer of these solar-like oscillations in V1449 Aquilae, added a new baptismal certificate to this β Cephei star and named it Chimera. The figure illustrates the behavior of the frequency versus time for two modes in the frequency spectrum of Chimera, a solar-like mode (top) and a β Cephei mode (bottom). The stochastic nature of the solar-like mode reveals itself in the instability of its frequency as time goes on and in the spread in frequency on several μHz. The contrast with the stability in frequency and the narrow frequency range of the β Cephei mode is striking.
- HD 46149: Later on solar-like oscillations were even discovered in a more massive O star member of the binary system HD 46149.[36] Constraints coming from the binary nature of the system coupled with seismic constraints led to the determination of the orbital parameters of the system as well as to the global properties of its members.
The open cluster NGC 2264
During a 23-day observing run in March 2008, CoRoT observed 636 members of the young open cluster
The stellar births and the stars' childhoods remain mostly hidden from us in the optical light because the early stars are deeply embedded in the dense molecular cloud from which they are born. Observations in the infrared or X-ray enable us to look deeper into the cloud, and learn more about these earliest phases in stellar evolution. Therefore, in December 2011 and January 2012, CoRoT was part of a large international observing campaign involving four space telescopes and several ground-based observatories. All instruments observed about 4000 stars in the young cluster NGC 2264 simultaneously for about one month at different wavelengths. The Canadian space mission
The CoRoT observations led to the discovery of about a dozen pulsating
The investigation of
Binary systems
A large number of
The eclipse phenomenon plays a key role since global parameters can immediately follow, bringing invaluable constraints, in addition to the seismic ones, to stellar modeling.- AU Monocerotis: This semi-detached binary system contains a Be star interacting with its G star companion. Its observation by CoRoT provided an extremely high quality lightcurve. Global parameters could then be improved and new ephemeris for the orbital motion as well as for another long term variation were derived. This long period variation seems to originate from a periodic light attenuation by circumstellar dust.[85]
- HD 174884: Tidally induced pulsations have been detected in the high eccentricity (e=0.29) and short period binary system HD 174884 consisting of two B stars.[86] The upper panel of the figure shows the full light curve of the system. In the second panel tiny secondary eclipses are seen with a depth of about 1% of the depth of the primary eclipse. Actually the system is formed of stars of similar mass, size and temperature. Were the orbit circular, the eclipses would be similar in depth. However the orbit is highly eccentric and its orientation in space with respect to us is such that the secondary eclipse occurs when the stars are at a larger distance than at primary eclipse. The third panel of the figure shows the projection on the plane of the sky (i.e. the system as we see it) at different orbital phases.
- CoRoT 102918586 (alias CoRoT Sol 1): The relatively bright eclipsing system CoRoT 102918586 is a double-lined spectroscopic binary, observed by CoRoT, which revealed clear evidence of γ Doradus type pulsations. In addition to CoRoT photometry, a spectroscopic follow-up was performed which yielded the radial velocity curves, the component effective temperatures, the metallicity, and the line-of-sight projected rotational velocities. The eclipsing binary light curve analysis, combined with the spectroscopic results, provided system physical parameters with 1–2% accuracy while the comparison with evolutionary models led to constraints on the age of the system. After subtracting the best–fitting eclipsing binary model, the residuals were analyzed to determine the pulsation properties. The primary star pulsates with typical γ Dor frequencies and shows a period spacing consistent with high order g-modes of degree l=1.
- HR 6902: The binary system HR 6902 containing a red giant and a B star was observed by CoRoT during two runs, which allowed us to fully cover the primary as well as the secondary eclipses. This system is presently being analyzed with the ultimate goal of bringing new constraints on the internal structure of the red giant in particular.[87]
- A low mass binary: One of the binary system observed by CoRoT is of particular interest since the less massive component is a late M star of 0.23 M⊙ with an estimated effective temperature of about 3000 K.[88] The primary component is a 1.5 M⊙ star MS star.
- A beaming effect in a binary: A binary system observed by CoRoT showed out of eclipses variations which were interpreted as a beaming effect (also called Doppler boosting). This effect results from the variation in brightness of source approaching or moving away from the observer, with an amplitude proportional to the radial velocity divided by the speed of light.[89] The periodic variation in the velocity of an orbiting star will thus produce a periodic beaming variation in the light curve. Such an effect can confirm the binary nature of a system even without any detectable eclipses nor transits. One of the main advantages of the beaming effect is the possibility to determine the radial velocity directly from the light curve but very different luminosities of the binary components are required and a single radial velocity curve can only be obtained as in an SB1 binary system. The out of eclipse variations were modeled with the BEER (Beaming Ellipsoidal Reflection) algorithm.[90]
Exoplanets
To find extra solar planets, CoRoT uses the method of transits detection. The primary transit is the occultation of a fraction of the light from a star when a celestial object, such as a planet, passes between the star and the observer. Its detection is made possible by the sensitivity of CCD to very small changes in light flux. Corot is capable of detecting changes in brightness of about 1/10,000. Scientists can thus hope finding planets with a size of approximately 2 times that of the Earth with this method, a class of planet called Super-Earth; detection of Corot-7b, whose radius is 1.7 times that of the Earth has shown that these predictions were correct. CoRoT takes an exposure of 32 seconds duration, each 32 seconds, but the image is not fully transmitted to Earth because the data flow would be too large. The onboard computer performs an important work of data reduction: the field around each target star, previously selected by the exoplanets team, is defined on a certain number of pixels described by a particular mask, the sum all pixels within the mask is then performed and several exposures are added (usually 16, which amounts to an integration time of about 8 minutes) before sending this information to the ground. For some stars, considered particularly of interest, data of each exposure is transmitted every 32 seconds. Such a sampling of 32s or 512s is well suited to the detection of a planetary transit that lasts from a little less than an hour to several hours. A feature of this method is that it requires to detect at least three successive transits separated by two equal time intervals before one can consider a target as a serious candidate. A planet of orbital period T should at least be observed for a time interval between 2T and 3T to have a chance to detect three transits. The distance of the planet to the star ( which is characterized by a the semi-major axis of the elliptical orbit ) is linked to its orbital period by the second law of Kepler / Newton a3 = T2 Mstar, using respectively as units for a, M and T: the distance from the Earth to the Sun (150 million km), the mass of the Sun, the orbital period of the Earth (1 year); this implies that if the observing time is less a year, for example, the orbits of the detectable planets will be significantly smaller than that of the Earth. So, for CoRoT, due to the maximum duration of 6 months of observation for each star field, only planets closer to their stars than 0.3 Astronomic Units (less than the distance between the Sun and Mercury) can be detected, therefore generally not in the so-called habitable zone. The Kepler mission (NASA) has continuously observed the same field for many years and thus had the ability to detect Earth sized planets located farther from their stars.
The moderate number of exoplanets discovered by CoRoT (34 during the 6 years of operation), is explained by the fact that a confirmation should absolutely be provided by ground-based telescopes, before any announcement is made. Indeed, in the vast majority of cases, the detection of several transits does not mean the detection of a planet, but rather that of a binary star system, either one that corresponds to a grazing occultation of a star by the other, or that the system is close enough to a bright star (the CoRoT target) and the effect of transit is diluted by the light of this star; in both cases the decrease in brightness is low enough to be compatible with that of a planet passing in front of the stellar disk. To eliminate these cases, one performs observations from the ground using two methods: radial velocity spectroscopy and imaging photometry with a CCD camera. In the first case, the mass of the binary stars is immediately detected and in the second case one can expect to identify in the field the binary system near the target star responsible for the alert: the relative decline of brightness will be greater than the one seen by CoRoT which adds all the light in the mask defining the field of measurement. In consequence, the CoRoT exoplanet science team has decided to publish confirmed and fully characterized planets only and not simple candidate lists. This strategy, different from the one pursued by the
Timeline of planetary discoveries
CoRoT discovered its first two planets in 2007: the hot Jupiters CoRoT-1b and CoRoT-2b.[9][92] Results on asteroseismology were published in the same year.[93]
In May 2008, two new exoplanets of Jupiter size, CoRoT-4b and CoRoT-5b, as well as an unknown massive celestial object, CoRoT-3b, were announced by ESA.
In February 2009, during the First CoRoT Symposium, the super-Earth CoRoT-7b was announced, which at the time was the smallest exoplanet to have its diameter confirmed, at 1.58 Earth diameters. The discoveries of a second non-transiting planet in the same system, CoRoT-7c, and of a new Hot Jupiter, CoRoT-6b, were also announced at the Symposium.
In March 2010 CoRoT-9b was announced. It's a long period planet (95.3 days) in an orbit close to that of Mercury.[94]
In June 2010 the CoRoT team announced
In June 2011, during the Second CoRoT Symposium, the probe added ten new objects to the Exoplanet catalogue:[98] CoRoT-16b, CoRoT-17b, CoRoT-18b, CoRoT-19b, CoRoT-20b, CoRoT-21b, CoRoT-22b, CoRoT-23b, CoRoT-24b, CoRoT-24c.
As of November 2011, around 600 additional candidate exoplanets are being screened for confirmation.[99]
Main results
Among the exoplanets CoRoT detected, one can highlight a subset with the most original features :
- CoRot-1b, the first planet detected by CoRoT is a hot Jupiter. By further analysis, CoRoT-1b became the first exoplanets to have its secondary eclipse detected in the optical,[100] thanks to the high precision lightcurve delivered by CoRoT.
- CoRoT-3b, with a mass of 22 MJup, it appears to be "something between a brown dwarf and a planet." According to the definition of planet proposed by the owners of the exoplanet.eu database[101] three years later, CoRoT-3b, being less massive than 25 Jupiter masses, is classified as an exoplanet. In an August 2010 paper, CoRoT detected the ellipsoidal and the relativistic beaming effects in the CoRoT-3 lightcurve.[102]
- CoRot-7b, with a radius of 1.7 REarth and a mass of 7.3 MEarth, was the first confirmed rocky planet, with a density and composition which are close to those of the Earth. Its orbital period (i.e. its local year) is very short since it lasts just 20.5 h; because the planet is very close to its star (an almost solar type star), its orbit is a mere 6 stellar radii. As the planet must be in synchronous rotation with its orbital motion because of the huge tidal forces it undergoes, it always presents the same hemisphere to the star: as a consequence, the two hemispheres, the enlightened and the dark, exhibit an extreme contrast in temperature (2200K vs 50K) and a huge ocean of lava must occupy a large part of the hot side. A continent of water and nitrogen dioxide ices is probably occupying the dark side. CoRoT-7b was also the first case of a system discovered by CoRoT, with two super-Earths, one in transit the other not; radial velocity measurements have indeed led to the discovery of CoRoT-7c, a planet of 8.4 MEarth and a period of 3.79 days. A third planet is even suspected.
- CoRoT-8b, a planet of the same class as Neptune, with a mass of 0.22 MJup;
- CoRoT-9b, the first planet that has earned the epithet of a temperate planet. With 80% of Jupiter mass, and an orbit similar to the Mercury one, this is the first transiting temperate planet found known to be similar to those within the Solar System. At the time of the discovery, it was the second longest period exoplanet found in transit, after HD80606 b.
- CoRoT-11b and CoRoT-2b, two inflated planets, with radius 1.4 and 1.5 RJup respectively: the theory does not yet provide a consistent model for such objects;
- CoRoT-15b, a bona fide brown dwarf in orbit;
- CoRoT-10b, CoRoT-16b, CoRoT-20b, CoRoT-23b, four hot Jupiters which are on an eccentric orbits, despite circularization is theoretically predicted for such small orbits: this is a clear constraint on Qp, the parameter that quantifies the energy dissipation by tidal forces;
- CoRoT-22b, notable for its small size, having less than half the mass of Saturn.
- CoRoT-24b and c, the second planetary system discovered by CoRoT, with two small planets of 0.10 and 0.17 MJup. The two planets are of Neptune size, and orbit the same star and represent the first multiple transiting system detected by CoRoT.
List of exoplanets discovered
The following transiting planets have been announced by the mission.
Light green rows indicate that the planet orbits one of the stars in a binary star system.
Star | Constellation | Right ascension |
Declination | App. mag. |
ly )
|
Spectral type |
Planet | Mass (MJ) |
Radius (RJ) |
Orbital period (d) |
) | Orbital eccentricity |
Inclination )
(° |
Discovery year |
Ref |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
CoRoT-1 | Monoceros |
06h 48m 19s | −03° 06′ 08″ | 13.6 | 1,560 | G0V | b | 1.03 | 1.49 | 1.5089557 | 0.0254 | 0 | 85.1 | 2007 | [103] |
CoRoT-2 | Aquila | 19h 27m 07s | +01° 23′ 02″ | 12.57 | 930 | G7V | b | 3.31 | 1.465 | 1.7429964 | 0.0281 | 0 | 87.84 | 2007 | [104] |
CoRoT-3 | Aquila | 19h 28m 13.265s | +00° 07′ 18.62″ | 13.3 | 2,200 | F3V | b | 21.66 | 1.01 | 4.25680 | 0.057 | 0 | 85.9 | 2008 | [105] |
CoRoT-4 | Monoceros |
06h 48m 47s | −00° 40′ 22″ | 13.7 | F0V | b | 0.72 | 1.19 | 9.20205 | 0.090 | 0 | 90 | 2008 | [106] | |
CoRoT-5 | Monoceros |
06h 45mm 07ss | +00° 48′ 55″ | 14 | 1,304 | F9V | b | 0.459 | 1.28 | 4.0384 | 0.04947 | 0.09 | 85.83 | 2008 | [107] |
CoRoT-6 | Ophiuchus | 18h 44m 17.42s | +06° 39′ 47.95″ | 13.9 | F5V | b | 3.3 | 1.16 | 8.89 | 0.0855 | < 0.1 | 89.07 | 2009 | [108] | |
CoRoT-7 | Monoceros |
06h 43m 49.0s | −01° 03′ 46.0″ | 11.668 | 489 | G9V | b | 0.0151 | 0.150 | 0.853585 | 0.0172 | 0 | 80.1 | 2009 | [109] |
CoRoT-8 | Aquila | 19h 26m 21s | +01° 25′ 36″ | 14.8 | 1,239 | K1V | b | 0.22 | 0.57 | 6.21229 | 0.063 | 0 | 88.4 | 2010 | [110] |
CoRoT-9 |
Serpens | 18h 43m 09s | +06° 12′ 15″ | 13.7 | 1,500 | G3V | b | 0.84 | 1.05 | 95.2738 | 0.407 | 0.11 | >89.9 | 2010 | [111] |
CoRoT-10 |
Aquila | 19h 24m 15s | +00° 44 ′ 46″ | 15.22 | 1,125 | K1V | b | 2.75 | 0.97 | 13.2406 | 0.1055 | 0.53 | 88.55 | 2010 | [112] |
CoRoT-11 |
Serpens | 18h 42m 45s | +05° 56′ 16″ | 12.94 | 1,826 | F6V | b | 2.33 | 1.43 | 2.99433 | 0.0436 | 0 | 83.17 | 2010 | [113] |
CoRoT-12 |
Monoceros |
06h 43m 04s | −01° 17′ 47″ | 15.52 | 3,750 | G2V | b | 0.917 | 1.44 | 2.828042 | 0.04016 | 0.07 | 85.48 | 2010 | [114] |
CoRoT-13 |
Monoceros |
06h 50m 53s | −05° 05′ 11″ | 15.04 | 4,272 | G0V | b | 1.308 | 0.885 | 4.03519 | 0.051 | 0 | 88.02 | 2010 | [115] |
CoRoT-14 |
Monoceros |
06h 53m 42s | −05° 32′ 10″ | 16.03 | 4,370 | F9V | b | 7.58 | 1.09 | 1.51215 | 0.027 | 0 | 79.6 | 2010 | [116] |
CoRoT-16 | Scutum | 18h 34m 06s | −06° 00′ 09″ | 15.63 | 2,740 | G5V | b | 0.535 | 1.17 | 5.3523 | 0.0618 | 0.33 | 85.01 | 2011 | [117] |
CoRoT-17 |
Scutum | 18h 34m 47s | −06° 36′ 44 ″ | 15.46 | 3,001 | G2V | b | 2.43 | 1.02 | 3.768125 | 0.0461 | 0 | 88.34 | 2011 | [118] |
CoRoT-18 |
Monoceros |
06h 32m 41s | −00° 01′ 54″ | 14.99 | 2,838 | G9 | b | 3.47 | 1.31 | 1.9000693 | 0.0295 | <0.08 | 86.5 | 2011 | [119] |
CoRoT-19 |
Monoceros |
06h 28m 08s | −00° 01′ 01″ | 14.78 | 2,510 | F9V | b | 1.11 | 1.45 | 3.89713 | 0.0518 | 0.047 | 87.61 | 2011 | [120] |
CoRoT-20 | Monoceros |
06h 30m 53s | +00° 13′ 37″ | 14.66 | 4,012 | G2V | b | 4.24 | 0.84 | 9.24 | 0.0902 | 0.562 | 88.21 | 2011 | [121] |
CoRoT-21 |
Monoceros |
16 | F8IV | b | 2.26 | 1.30 | 2.72474 | 0.0417 | 0 | 86.8 | 2,011 | [122] | |||
CoRoT-22 |
Serpens | 18h 42m 40s | +06° 13′ 08″ | 11.93 | 2,052 | G0IV | b | < 0.15 | 0.52 | 9.7566 | 0.094 | < 0.6 | 89.4 | 2011 | |
CoRoT-23 | Serpens | 18h 39m 08s | +04° 21′ 28″ | 15.63 | 1,956 | G0V | b | 2.8 | 1.05 | 3.6314 | 0.0477 | 0.16 | 85.7 | 2011 | [123] |
CoRoT-24 | Monoceros |
06h 47m 41s | −03° 43′ 09″ | 4,413 | b | < 0.1 | 0.236 | 5.1134 | 2011 | ||||||
c | 0.173 | 0.38 | 11.749 | 2011 | |||||||||||
CoRoT-25 |
Ophiuchus | 18h 42m 31.120s | +06° 30′ 49.74″ | 15.02 | 3,711 | F9V | b | 0.27 | 1.08 | 4.86 | 0.0578 | 84.5 | 2011 | ||
CoRoT-26 | Ophiuchus | 18h 39m 00.0s | +06° 58′ 12.00″ | 15.76 | 5,446 | G8IV | b | 0.5 | 1.26 | 4.204 | 0.0526 | 0 | 86.8 | 2012 | |
CoRoT-27 |
Serpens | 18h 33m 59.00s | +05° 32′ 18.32″ | 15.77 | 4413 | G2 | b | 10.39±0.55 | 1.01±0.04 | 3.58 | 0.048 | <0.065 | 2013 | [124][125] | |
CoRoT-28 | Ophiuchus | 18h 34m 45.0s | +05° 34′ 26″ | 13.47 | 1826 | G8/9IV | b | 0.484±0.087 | 0.9550±0.0660 | ||||||
CoRoT-29 | Ophiuchus | 18h 35m 36.50s | +06° 28′ 46.68″ | 15.56 | 2,683 | K0V | b | 0.84 | 0.90 | 2.85 | 0.039 | <0.12 | 87.3 | 2015 | [126] |
CoRoT-30 | Ophiuchus | 18h 30m 24.28s | +06° 50′ 09.36″ | 15.65 | 3,461 | G3V | b | 0.84 (± 0.34) | 1.02 (± 0.08) | 9.06005 (± 0.00024) | 0.084 (± 0.001) | 0.007 (+0.031 -0.007) | 90.0 (± 0.56) | 2017 | [129] |
CoRoT-31 | Monoceros | 06h 19m 16.97s | −04° 25′ 20.16″ | 15.7 | 6,940 | G2IV | b | 2.84 (± 0.22) | 1.46 (± 0.3) | 4.62941 (± 0.00075) | 1.46 (± 0.3) | 0.02 (+0.16 -0.02) | 83.2 (± 2.3) | 2017 | [130] |
CoRoT-32 | Monoceros | 06h 40m 46.84s | +09° 15′ 26.69″ | 13.72 | 1,912 | G0VI | b | 0.15±0.1 | 0.57±0.06 | 6.72 |
Other discoveries
The following table illustrates brown dwarf detected by CoRoT as well as non-transiting planets detected in the follow-up program:
Star | Constellation | Right ascension |
Declination | App. mag. |
ly )
|
Spectral type |
Object | Type | Mass (MJ) |
Radius (RJ) |
Orbital period (d) |
) | Orbital eccentricity |
Inclination )
(° |
Discovery year |
Ref |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
CoRoT-7 | Monoceros |
06h 43m 49.0s | −01° 03′ 46.0″ | 11.668 | 489 | G9V | c | planet | 0.0264 | – | 3.69 | 0.046 | 0 | – | 2009 | [131] |
CoRoT-15 | Monoceros |
06h 28m 27.82s | +06° 11′ 10.47″ | 16 | 4,140 | F7V | b |
brown dwarf | 63.3 | 1.12 | 3.06 | 0.045 | 0 | 86.7 | 2010 | [132] |
Global properties of the exoplanets discovered by CoRoT
All CoRoT planets were detected during long runs i.e. of at least 70 days. The detection team found on average between 200 and 300 cases of periodic events for each run, corresponding to 2–3% of the stars monitored. Of these, only 530 in total were selected as candidate planets (223 in the direction of the galactic anti-center and 307 towards the center). Only 30 of them were finally found to be true planets, i.e. about 6%, other cases being eclipsing binaries ( 46%) or unresolved cases (48%).[133]
The detection capabilities of Corot are illustrated by the figure D showing the depth of the transits measured for all candidates, depending on the period and the brightness of the star: there is indeed a better ability to detect small planets (up to 1.5 R Earth ) for short periods (less than 5 days) and bright stars.
The CoRoT planets cover the wide range of properties and features found in the disparate family of exoplanets: for instance, the masses of CoRoT planets cover a range of almost four orders of magnitude, as shown on Figure.
Tracing the mass of the planet versus the mass of the star (Figure), one finds that the CoRoT data set, with its lower scatter than other experiments, indicates a clear trend that massive planets tend to orbit massive stars, which is consistent with the most commonly accepted models of planetary formation.
See also
- Automated Planet Finder – Robotic optical telescope searching for extrasolar planets
- Darwin – 2007 European study concept of an array of space observatories
- High Accuracy Radial Velocity Planet Searcher – high-precision echelle spectrograph
- Kepler space telescope – NASA spacecraft for exoplanetology (2009–2018)
- List of multiplanetary systems – A list of systems with multiple planets
- NASA Exoplanet Archive – Online astronomical exoplanet catalog and data service
- Space Interferometry Mission – Cancelled NASA space telescope
- Terrestrial Planet Finder – NASA concept study of an array of space telescopes
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External links
- Media related to COROT at Wikimedia Commons
- CoRoT on the CNES site
- CoRoT N2 Public archive