CoRoT

COROT

From Wikipedia, the free encyclopedia

COROT (COnvection ROtation and planetary Transits) is a space mission led by the French Space Agency (CNES) in conjunction with the European Space Agency (ESA) and other international partners. The mission's two objectives are to search for extrasolar planets with short orbital periods, particularly those of large terrestrial size, and to perform asteroseismology by measuring solar-like oscillations in stars.[1] It was launched at 14:28:00 UTC on 27 December 2006, atop a Soyuz 2.1b carrier rocket.[2][3][4] COROT subsequently reported first light on 18 January 2007.[5] COROT is the first spacecraft dedicated to extrasolar planet detection. It detected its first extrasolar planet, COROT-1b, in May 2007.[6] Mission flight operations were originally scheduled to end 2.5 years from launch but apparently flight operations were extended to January, 2010[7] and then to 2013[8].

Overview

Spacecraft Design

The COROT optical design minimizes stray light coming from the Earth and provides a field of view of 2.7° by 3.05°. The COROT optical path consists of a 27 cm (10.6 in) diameter off-axis afocal telescope housed in a two-stage opaque baffle specifically designed to block sunlight reflected by the Earth and a camera consisting of a dioptric objective and a focal box. Inside the focal box is an array of four CCD detectors protected against radiation by aluminum shielding 10mm thick. The asteroseismology CCDs are defocused by 760μm toward the dioptric objective to avoid saturation of the brightest stars. A prism in front of the planet detection CCDs gives a small spectrum designed to disperse more strongly in the blue wavelengths.[9]

The four CCD detectors are model 4280 CCDs provided by E2V Technologies. These CCDs are frame-transfer, thinned, back-illuminated designs in a 2048 pixel by 2048 pixel array. Each pixel is 13.5 × 13.5μm2 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°.[9]

The satellite, built in the Cannes Mandelieu Space Center, has a launch mass of 630 kg, is 4.10 m long, 1.984 m in diameter and is powered by two solar panels.[7]

Mission Design

Over its planned 2½ year mission it will observe perpendicular to its orbital plane, meaning there will be no Earth occultations, allowing 150 days of continuous observation. During the northern summer it will observe in an area around Serpens Cauda and during the winter it will observe in Monoceros. During the remaining 30 days between the two main observation periods, COROT will observe 5 other patches of sky. Four fixed areas of the sky have been identified for study:

The probe will monitor the brightness of stars, watching for the slight dimming that happens in regular intervals when planets transit their primary sun. COROT will be sensitive enough to detect rocky planets several times larger than Earth; it is also expected to discover new gas giants, which currently comprise almost all of the known extrasolar planets.[10]

COROT will also undertake 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.

In each field of view there will be one main target star for the asteroseismology as well as up to nine other targets. Simultaneously, it will be recording the brightness of 12,000 stars brighter than apparent magnitude 15.5 for the extrasolar planet study. It is expected that a few dozen planets will be found as a result of this project.

The mission began on 27 December 2006 when a Russian Soyuz 2-1b rocket lifted the satellite into a circular polar orbit with an altitude of 827 km . The first scientific observation campaign started on 3 February 2007.[11]

Development

This section requires expansion.

The primary contractor for the construction of the COROT vehicle was CNES,[12] to which individual components were delivered for vehicle assembly. The COROT equipment bay, which houses the data acquisition and pre-processing electronics, was constructed by the LESIA Laboratory at the Paris Observatory and took 60 person-years to complete.[12] The COROT camera, also constructed by the LESIA Laboratory, took 25 person-years to complete.[12]

Potential

Before the beginning of the mission, the team stated with caution that COROT would only be able to detect planets a few times to several times larger than Earth and that it was not specifically designed to detect habitable planets (it would instead assess their potential for habitability). According to the press release announcing the first results, COROT's instruments are performing with higher precision than had been predicted, and may be able to find planets down to the size of Earth.[6]

COROT should be assumed to only detect a small percentage of planets within its detection range due to the low percentage of existing planets that would likely make transits from the angle of observation from our Solar System. Expectations are that any planetary systems detected within a suitable range for further observations will be followed up by the future Darwin and Terrestrial Planet Finder spacecrafts or other projects like Kepler (NASA), New Worlds Mission, or Space Interferometry Mission.

Discoveries

On May 3, 2007, it was reported that COROT had discovered a hot Jupiter COROT-1b orbiting a sun-like star 1,500 light years away. This planet has a radius approximately 1.78 times that of Jupiter, a mass approximately 1.3 times that of Jupiter, and orbits its parent star once every 1.5 days.[6][13] On the 300th day of operations ESA reported that "CoRoT is discovering exo-planets at a rate only set by the available resources to follow up the detections".[14] On 20 December 2007, additional results were published, declaring that a second exoplanet, COROT-2b had been discovered, this time with a radius 1.4 times and a mass 3.5 times that of Jupiter. The orbital period is less than two days. Results on asteroseismology were published in the same press release.[15] Three papers describing the two exoplanets, with radial-velocity follow-up, appeared in Astronomy and Astrophysics in May 2008 (Barge 2008, Alonso 2008 and Bouchy 2008).

In May 2008, findings of two new exoplanets, as well as an unknown celestial object COROT-3b were announced by ESA. COROT-3b appears to be "something between a brown dwarf and a planet."

In February 2009, COROT-7b was announced. It is the smallest exoplanet to have its diameter confirmed at 1.7 Earth's diameter.

In March 2010 CoRoT-9b was announced. This is the first temperate planet found known to be similar to those within our own Solar System.[16]

COROT has found three far stars which show Sun-like seismology (oscillations and granulations), although hotter.[17]

Planets discovered by COROT

The following planetary objects have been announced by the mission.

Discovery

Ref

ascension

06h 48m 19s

19h 27m 07s

19h 28m 13.265s

06h 48m 47s

06h 45mm 07ss

18h 44m 17.42s

06h 43m 49.0s

19h 26m 21s

18h 43m 09s

–03° 06′ 08″

+01° 23′ 02″

+00° 07′ 18.62″

−00° 40′ 22″

+00° 48′ 55″

+6° 39′ 47.95″

−01° 03′ 46.0″

+01° 25′ 36″

+06° 12′ 15″

mag.

13.6

12.57

13.3

13.7

14

13.9

11.668

14.8

13.7

1560

930

2200

1304

489

1239

1500

type

G0V

G7V

F3V

F0V

F9V

F5V

G9V

K1V

G3V

(MJ)

1.03

3.31

21.66

0.72

0.459

3.3

0.0151

0.22

0.84

(RJ)

1.49

1.465

1.01

1.19

1.28

1.16

0.150

0.57

1.05

(d)

1.5089557

1.7429964

4.25680

9.20205

4.0384

8.89

0.853585

6.21229

95.2738

(AU)

0.0254

0.0281

0.057

0.090

0.04947

0.0855

0.0172

0.063

0.407

eccentricity

0

0

0

0

0.09

< 0.1

0

0

0.11

(°)

85.1

87.84

85.9

90

85.83

89.07

80.1

88.4

>89.9

year

2007

2007

2008

2008

2008

2009

2009

2010

2010

Failure of Data Processing Unit #1

On March 8, 2009 the satellite suffered a loss of communication with Data Processing Unit #1[not in citation given], processing data from one of the two photo-detector chains on the spacecraft. Science operations resumed early April with Data Processing Unit #1 offline while Data Processing Unit #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%. The loss of channel 1 appears to be permanent.[20]

See Also

References

External Links

News

v • d • e

Programmes

Related

Current

Active

Queued

Future

Previous

Cancelled

Failed

Retrieved from "http://en.wikipedia.org/wiki/COROT"

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From UniverseToday.com for June 14th, 2010

Weird Collection of Worlds in the Latest Cache of CoRoT Expoplanets

Written by Nancy Atkinson

Family portrait of the first 15 CoRoT planets. Credit: Patrice Amoyel (CNES)

The CoRoT (Convection, Rotation and Transits) spacecraft has been busy, and using this exoplanet-finding-machine astronomers recently found six new extrasolar planets, which contain an odd assortment of new worlds. They include shrunken-Saturns to bloated hot Jupiters, as well a rare brown dwarf with 60 times the mass of Jupiter. "Each of these planets is interesting in its own right, but what is really fascinating is how diverse they are," said co-investigator Dr Suzanne Aigrain from Oxford University’s Department of Physics. "Planets are intrinsically complex objects, and we have much to learn about them yet."

CoRoT is dedicated to looking for planets orbiting other stars, and finds them when they transit, or pass in front of their stars. CoRot now has found 15 of the total 453 exoplanets.

Once CoRoT detects a transit, additional observations are made from the ground, using a number of telescopes all over the world. Although astronomers cannot see the planets directly, they use the space- and ground-based data to measure the sizes, masses, and orbits of these new planets precisely. This is why, among all known exoplanets, those with transits yield the most complete information about planet formation and evolution.

‘Every discovery of an extrasolar planetary system is a new piece in the puzzle of how these systems do form and evolve. The more systems we uncover, the better we can hope to understand the processes at play,’ said Magali Deleuil, researcher at the Laboratoire d'Astrophysique de Marseille (LAM) and head of the CoRoT exoplanet program.

The six new planets are:

CoRoT-8b: the smallest in this batch: At about 70% of the size and mass of Saturn, CoRoT-8b is moderately small among the previously known transiting exoplanets. Its internal structure should be similar to that of ice giants, like Uranus and Neptune, in the Solar System. It is the smallest planet discovered by the CoRoT team so far after CoRoT-7b, the first transiting Super-Earth.

CoRoT-10b: the eccentric giant: The orbit of CoRoT-10b is so elongated that the planet passes both very close to and very far away from its star. The amount of radiation it receives from the star varies tenfold in intensity, and scientists estimate that its surface temperature

may increase from 250 to 600°C, all in the space of 13 Earth-days (the length of the year on CoRoT-10b).

CoRoT-11b: the planet whose star does the twist: CoRoT-11, the host star of CoRoT-11b, rotates around its axis in 40 hours. For comparison, the Sun’s rotation period is 26 days. It is particularly difficult to confirm planets around rapidly rotating stars, so this detection is a significant achievement for the CoRoT team.

CoRoT-12b, 13b and 14b: a trio of giants: These three planets all orbit close to their host star but have very different properties. Although CoRoT-13b is smaller than Jupiter

, it is twice as dense. This suggests the presence of a massive rocky core inside the planet. With a radius 50% large than Jupiter’s (or 16 times larger than the Earth’s), CoRoT-12b belongs to the family of `bloated hot Jupiters’, whose anomalously large sizes are due to the intense stellar radiation they receive. On the other hand, CoRoT-14b, which is even closer to its parent star, has a size similar to Jupiter’s. It is also massive, 7.5 times the mass of Jupiter, which may explain why it is less puffed up. Such very massive and very hot planets are rare, CoRoT-14b is only the second one discovered so far.

CoRoT-15b: the brown dwarf: CoRoT-15b’s mass is about 60 times that of Jupiter. This makes it incredibly dense, about 40 times more so than Jupiter. For that reason, it is classified as a brown dwarf, intermediate in nature between planets and stars. Brown dwarfs are much rarer than planets, which makes this discovery all the more exciting. ( Brown dwarfs are generally from about 14 - 72 Jupiters in mass.)

Source: Oxford University

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Categories: European Space Agency | Space exploration | Artificial satellites orbiting Earth | Space telescopes | French space program | Exoplanetology | 2006 in spaceflight