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Searching for another planet Earth using QHY42
2019 / 02 / 15
Exoplanets have always been one of the hottest topics that astronomy enthusiasts talk about. In the past few years, the first suspected habitable planet Kepler 452b discovered by the Kepler Space Telescope triggered wide-spread discussion.
A brief introduction: several common methods of detecting exoplanets
  1. Astrometry
The presence of the planet causes the Centre of Mass (CoM) of the entire planet system to deviate from the CoM of the star, which in turn causes the star to revolve around the CoM of the whole system. Measuring periodic position changes of the star can reveal its planet.
  1. Radial velocity
Since orbits of planets around stars are elliptical, exoplanets take turns move toward and away from the Earth during one complete revolution around their host stars. Therefore, the radial velocity of the planet (the velocity component along our line of sight) changes and can be detected by the Doppler Effect.
  1. Transit
Many current large-scale exoplanet searching projects, such as Kepler and TESS use this method.
When a planet passes in front of the host star's disk and blocks part of the starlight, the star's brightness falls temporarily. The extent of this darkening depends on the size of the planet relative to the star. By performing photometry to the stars, darkening effects and hence exoplanets can be detected.
Courtesy: “Planetary transit” by Nikola Smolenski, licensed under CC BY-SA 3.0
Not long ago, Bruno Fontaine of the Pierrevert Observatory in France used QHYCCD's new scientific CCD, QHY42, to perform a high-quality transit observation.
After stacking 2,500 4-second exposures of the WASP 114b star, Bruno ran a regression algorithm to analyse the data and obtain the star's light curve. Stacking reduced the standard deviation of the data, making the trend in its light curve more obvious.
Light curve of WASP 114b taken by QHY42. Courtesy: Bruno Fontaine
By comparing this observation with Bruno using other CCDs under identical environment, we can see that stacking multiple short-exposure images using QHY42 is better than the conventional long-exposure method using other CCDs in that the standard deviation is smaller. This indicates that the analysis is more accurate. In addition, doing short exposures reduces the impact of other unexpected factors, such as aircrafts and artificial satellites. The S-indicator of the observation done by QHY42 reached 3.7mmag, indicating a higher accuracy than the other observation done by another CCD with an S-indicator of 6.7mmag.
Courtesy: Bruno Fontaine
This exceptional transition observation benefits from the extremely high quantum efficiency (QE) and low noise level of QHY42.
Back-illuminated design of QHY42 allows its quantum efficiency to reach 95% at 560 nm, greatly increasing the sensitivity of the CCD to photons. With readout noise as low as 1.7e-, only receiving few photons can generate a reasonably high SNR. Also, there is no microlens on each pixel ensuring that photometric measurements do not get interfered.
Quantum efficiency curve of QHY42 camera using TVSB anti-reflection film
Like other QHY cameras, the unique technology of QHYCCD significantly reduces the amplifier glow of QHY42.
This picture shows exposures with amp-glow control on/off.
In addition, the large pixels of ​​QHY42 increases its full-well capacity to 89 ke- which reduces the occurrence of blooming. Also, he large dimension of the sensor enables wide-field imaging on big telescopes.
All in all, these features of QHY42 make it ideal for a variety of scientific applications such as astronomical imaging, fluorescence imaging, spectroscopy, forensic identification, and high-voltage wire corona testing.
Please visit the official website of QHYCCD for further information about QHY42.
For more information on astronomical and products, please subscribe to the QHYCCD WeChat account and join the QHYCCD discussion QQ group (236692763).
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