The Kepler telescope has already detected hundreds of new planets

Apparts of one of the original documents that explain the facts

We report the detection of three transiting planets around a Sunlike star, which we designate Kepler-18. 

The transit signals were detected in photometric data from the Kepler satellite, and were confirmed to arise from planets using a combination of large transit-timing variations, radial-velocity variations,Warm-Spitzer observations, and statistical analysis of false-positive probabilities. 

The Kepler-18 star has a mass of 0.97M⊙, radius 1.1R⊙, effective temperature 5345 K, and iron abundance [Fe/H]= +0.19.

The planets have orbital periods of approximately 3.5, 7.6 and 14.9 days. 

The innermost planet “b” is a “super-Earth” with mass 6.9 ± 3.4M⊕, radius 2.00 ± 0.10R⊕, and mean density 4.9 ± 2.4 g cm3

.

The two outer planets “c” and “d” are both low-density Neptune-mass planets. 

Kepler-18c has a mass of 17.3 ± 1.9M⊕, radius 5.49 ± 0.26R⊕, and mean density 0.59 ± 0.07 g cm3, while Kepler-18d has a mass of 16.4 ± 1.4M⊕, radius 6.98 ± 0.33R⊕, and mean density 0.27 ± 0.03 g cm3. 

Kepler-18c and Kepler-18d have orbital periods near a 2:1 mean-motion resonance, leading to large and readily detected transit timing variations.

Subject headings : planetary systems — stars: individual (Kepler-18, KIC 8644288, 2MASS J19521906 +4444467) — techniques: photometric — techniques: spectroscopic

Introduction : 

Kepler is a NASA Mission designed to detect the transits of exoplanets across the disks of their stars. 

The ultimate mission goal is to detect the transits of potentially habitable Earth-size planets. 

To achieve this goal requires a telescope in a very stable space environment with a large (0.95-meter) effective aperture monitoring the brightness of about 150,000 stars simultaneously and continuously for over three years. 

The Kepler Mission design and performance are summarized by Borucki et al. (2010b) and by Koch et al. (2010b),and a discussion of the commissioning and first quarter data are given by Borucki et al. (2011a). 

Borucki et al.(2011b) reported 1235 planet candidates that were discovered during the first four months of the Mission.

Batalha et al. (2010b) discuss the selection and characteristics of the Kepler target stars.

(Kepler 4-8) were reported in January 2010 (Borucki et al. 2010a; Koch et al. 2010a; Dunham et al. 2010; Latham et al. 2010; Jenkins et al. 2010a). 

Kepler has detected an abundance of multi-planet systems.

Borucki et al. (2011b) reported a total of 170 candidate multi-planet systems among the 997 planet candidate host stars from the February 2011 data release.

Steffen et al. (2010) presented five of these systems in detail. 

The Kepler-9b and c system (Holman et al. 2010) was the first transiting multi-planet system confirmed by transit timing variations. Kepler-10 (Batalha et al. 2011) was the first rocky planet found by Kepler. 

Kepler- 11 (Lissauer et al. 2011a) is a transiting system of six planets.

Not all Kepler planets can be directly confirmed by supporting reflex radial velocity measurements of the parent star, or by detection and modeling of transit timing variations. Instead, some planets must be validated by analyzing all possible possible astrophysical falsepositive scenarios and comparing their a priori likelihood to that of a planet. 

The Kepler project has been able to utilize the BLENDER technique developed by Torres et al.(2004) to validate a third planet in the Kepler-9 system (Torres et al. 2011), a second planet in the Kepler-10 (Fressin et al. 2011) and the outer planet in the Kepler-11 system (Lissauer et al. 2011a).

Here we present the Kepler-18 system, containing two Neptune-mass transiting planets near a 2:1 mean motion resonance which show significant gravitational interactions which are observed via measurements of transit timing variations (TTVs), as well as a small, inner superEarth size transiting planet. 

This system is remarkably similar to the Kepler-9 system in its overall architecture.

Kepler Photometry

The Kepler spacecraft carries a photometer with a wide-field (∼ 115 deg 2) Schmidt camera of 0.95-m effective aperture. 

The spacecraft was launched in March 2.009, and is now in an Earth-trailing heliocentric orbit which allows nearly continuous photometric coverage of its field-of-view in Cygnus and Lyra. Caldwell et al.

(2010) discuss the early instrumental performance of the Kepler photometer system. 

The primary data for detection of transiting planets are the Long Cadence (LC) “Pre-search Data Conditioned” (PDC) time series data, in which 270 consecutive CCD readouts are binned, giving an effective sampling interval of 29.4244 minutes (Jenkins et al. 2010b). 

A small selected subset of Kepler targets is sampled at the Short Cadence (SC) rate of 9 consecutive reads for a sampling interval of 58.85 seconds (Gilliland et al. 2.010). 

Thus, one LC sample is the sum of 30 SC samples. 

The data from the spacecraft are processed through the Kepler Science Operations Center pipeline (Jenkins et al. 2010c) to perform standard CCD processing and to remove instrumental artifacts. 

The LC PDC time series data are searched for possible planetary transits using a wavelet-based adaptive matched filter (Jenkins et al. 2.010d). 

Possible planetary transit events with amplitude greater than 7.1σ are flagged and are then subjected to intensive validation efforts using the Kepler data (Batalha et al. 2010a; Wu et al. 2010).

Objects that pass this level of vetting are designated as a “Kepler Object of Interest” (KOI) and are sent to the Follow-up Observing Program (FOP) for further study.

Light Curves and Data Validation

One of the objects identified with possible transiting planets is the Kp 13.549 magnitude (where Kp is the magnitude in the Kepler passband) star KIC 8644288 (2MASS J19521906+4444467, K00137). 

After a possible transiting planet has been detected, the Kepler data are subjected to a set of statistical tests to search for possible astrophysical false-positive origin of the observed signal.

These data validation tests for the first five Kepler planet discoveries are described by Batalha et al. (2010a). 

Additional tests, including measurement of the image centroid motion during a transit (Wu et al. 2010) all gave a high probability that the signals seen were real. 

The application of these techniques to Kepler-10b is described in detail by Batalha et al. (2011).

Two separate transiting objects were immediately obvious in the LC data. K00137.01 has a transit ephemeris of T0[BJD] = (2455167.0883 ± 0.0023) + N ∗ (7.64159 ± 0.00003) days and a transit depth of 2287 ± 9 ppm. 

(All transit times and ephemerides in this paper are based on UTC.) 

K00137.02 has an ephemeris of T0[BJD] =(2455169.1776 ± 0.0013) + N ∗ (14.85888 ± 0.00004) days and a transit depth of 3265 ± 12 ppm. 

It was noted that the orbits of these two objects were very near a period ratio of 2:1. 

After filtering these transits of K00137.01 and K00137.02 from the lightcurve, we searched again for transiting objects, and found a third planet candidate in the system, K00137.03, which has a shorter orbital period than the other two transiting planets. K00137.03 has the ephemeris T0[BJD] = (2454966.5068 ± 0.0021) +N ∗ (3.504725 ± 0.000028) days, and a transit depth of only 254 ± 8 ppm. 

The two transit events that look significantly deeper than the others, near BJD 2454976.0 and BJD 2455243.5 are simultaneous transits of K00137.01 and K00137.02.

Follow up observations :

After the possible transiting planets were found, and the KOIs passed the Data Validation tests for false positive signals, K00137 was sent on to the Kepler Follow-up

Observing Program (FOP) for ground-based telescopic

Observations designed either to find any additional indication that these KOIs might be an astrophysical falsepositive signal, or to verify the planetary nature of the transit events.