1) Run a search and identify all planet detection techniques that have successfu
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Question
1) Run a search and identify all planet detection techniques that have successfully found planets. Include Pulsar timing, Radial velocity, and transit photometry in your answer to this question.
2) Except for the three techniques above, explain each of the other techniques in one paragraph.
3) Radial velocity technique is stronger in detecting close-in and massive planets, and transit photometry is more effective in detecting planets around smaller stars. Determine the strong capability of each of the other detection techniques. What type of planet is each technique sensitive to?
4) For each technique, name two planets that have been detected by that technique and name one survey or telescope.
Explanation / Answer
1) In addition to Pulsar timing, Radial velocity, and transit photometry, other planet detection techniques that have successfully found planets are Reflection/Emission modulations, Transit timing and duration variation, Relativistic beaming, Gravitational microlensing, Astrometry, and Direct Imaging.
2)
Reflection/Emission modulations: A relatively new method of planet detection, Reflection/Emission modulations uses visible reflection and thermal emissions to detect a planet. The brightness of the host star appears to vary in orbital time as the telescopes cannot differentiate the planet from the star. Similar to the transit method, using this method it is easier to detect large planets closer to host star who receive more light than far away planets. The higher albedo planets are detected in visible range while darker planets are detected in infrared range with this method.
Transit timing and duration variation: Once a planet is detected using the transit method, additional non-transit planets can be detected using variation in timing and duration. However, apart from detecting the planets, arriving at other details of the planet is difficult with these techniques except for the mass. Similar to transit method, this method too is more reliable for closer orbiting planets.
Relativistic beaming: Also, called as Doppler beaming this recent method of planet detection employs light variations with relativistic beaming of the observed flux from the star due to its motion. This method can be used to determine various characteristics such as the orbital eccentricity and mass of the planet. As the host star is tugged by the planet the gravity acts and the density of the photons change from the observer's viewpoint. This apparent change in photons and resulting brightness of the star can be used to detect the presence of the planet.
Gravitational Microlensing: In this method, the planet is detected as the light from the host star is bent and focused by gravity as the planet passes right in between the star and the observer. Based on the Einstein’s concept of gravity and the fabric of space, in this method, the light levels are lensed by the gravitational field of the planet and continued microlensing enables detection of the planet. The microlensing observations are usually performed by networks of robotic telescopes.
Astrometry: In this method, the planets are detected by precisely measuring stars positions in the sky and tracing the changes over time. Being one of the oldest methods of planet detection, this method has been modernised to improve the accuracy significantly. The gravitational influence that a star and the planet have on each other results in a mutual center of mass also called the pericenter. Therefore, detecting planets around brown dwarfs having low mass is easier with this method.
Direct imaging: The photos of light blockers obtained by rapidly advancing technologies make it easier to detect planets by the direct image. When especially large planets like Jupiter passes in greater orbits the direct imaging detection becomes easier. The images at multiple wavelengths enable better detection and clearer understanding of the planet’s characteristics.
3)
Pulsar timing: Capable of detecting very small planets even with a size less than 10th the mass of Earth.
Reflection/Emission modulations: Easier to detect large planets that are having low orbital radius.
Transit timing and duration variation: Easier to detect planets if at least one of the planet is massive, unsettling orbital period of lesser size planets.
Relativistic beaming: Easier to detect massive planets that are close to their host stars.
Gravitational Microlensing: This method is highly useful to detect planets between Earth and the center of our galaxy.
Astrometry: Most sensitive to planets with higher orbital radius.
Direct imaging: Easier to detect planets in the systems relatively nearer to Sun and the planet size is big.
4)
Method Survey/Telescope Planets Radial velocity ARPS (High Accuracy Radial Velocity Planet Searcher) spectrometer at the ESO 3.6 meter telescope in La Silla Observatory Gliese 876 d and GJ 3634 b Transit photometry MEarth Project, SuperWASP, KELT, and HATNet Kepler-42c and 55 Cancri e Pulsar timing Pulsar timing array (PTA) PSR B1257+12 b and PSR B1257+12 c Reflection/Emission modulations Kepler Space Observatory Kepler-70b and Kepler-70c Transit timing and duration variation Kepler Space Observatory Kepler-19c and Kepler-9d Relativistic beaming BEER algorithm Kepler-76b Gravitational Microlensing OGLE (the Optical Gravitational Lensing Experiment) MOA-2007-BLG-192Lb and MOA-2007-BLG-400Lb Astrometry Hubble Space Telescope VB 10b and HD 176051 Direct imaging H alpha survey Beta Pictoris b and HR 8799 eRelated Questions
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