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Transit Timing Variation Exoplanets

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Exoplanetary Scratchpad

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Discovered With TTV, Confirmed with Dopplar SpectrometryEdit

  • Kepler-88 System (Dec 2013) - Brightest star to host a transiting planet. A blue star a 385 ly away. The transiting planet had the nickname "The King of Transit Variations", a Neptune sized planet that is half as dense (sub-Saturnian?). The second is the first planet discovered by the transit variation timing technique to be confirmed by dopplar spectrometry, and is a Jovian. The planets are near the 1:2 resonance.

High Confidence TTV, Unconfirmed with Other TechniqueEdit

  • Kepler-19 System (Sep 2011) - System with two exoplanets discovered by Kepler, 690ly away. Planet b is a small Neptunian about 20 Earth masses and 2 Earth radii. It takes about 9 days to go around its star and has a surface temperature of 480C. Outer Planet c was discovered based on differences in transit timing (5 minutes) that it caused for Planet b. It is tilted relative to 'b', so it itself never transits. It is not massive enough to have its mass estimated. It could be a rocky planet on a circular 5-day orbit or a gas giant in an oblong 100 day orbit. First TTV detected planet confirmed that doesn't transit due to the fact that Kepler continuously observes the planet's transits, rather than stitches together several observations. Future observations with HARPs using radial velocity method will be used to pinpoint planet c's mass.
  • Kepler-46 System (May 2012) - System previously known as KOI-872. System that has three planets, the latter two which were discovered while searching for a moon around the first one with the HEK project (Hunt for Exomoons with Kepler). The motion of the first planet (34 day period) was being affected by the second one and detected using Transit Timing Variation technique. The second planet is Saturn sized in a 57 day orbit. A third hidden planet identified may be an interior Super-Earth with an 8 day period.

TTV Detected, Planet UnconfirmedEdit

  • WASP-3 System (Jul 2010) - One of three systems discovered by Super WASP containing a transiting very hot jupiter so close to its star that it is evaporating. Like the other two, WASP-4 and 5, it is incapable of radiating away heat from its star and instead swells up to significantly larger than Jupiter. This is a planet 81% more massive than Jupiter with 13% larger radius going around in just less day 2 days. Its transit time varies by up to 3 minutes, which indicates that a further planet may be in this system. This would be a further Neptunian planet and would be the first exoplanet detected by measuring eclipse timing deviations of an earlier discovered planet (Transit Timing Variation method). Further observations are needed to confirm the planet, but the best fit is that it is in 2:1 resonance with the larger planet. Planet b found to be in a low inclination prograde orbit with respect to its star's equator.
  • WASP-5 System - One of three systems discovered by Super WASP containing a transiting planet so close to its star that it is evaporating. A dense very hot jupiter, the densest known Jupiter mass planet at the time of its discovery (Mass is 63% more than Jupiter, Radius is 17% more). Found to orbit in the same manner as its star's rotation, while 6 out of 27 planets analyzed by the WASP team were found to orbit backwards around its star in 2010. Has a candidate planet detected by the Transit Timing Variation method.
  • WASP-10 System - System that contains a super Jupiter around an orange star. At first believed to be inflated, but later found to be smaller. Has a density similar to the moon. Has a candidate planet detected by the Transit Timing Variation method.

Discovered with Transit, Confirmed with TTVEdit

  • Kepler-11 System - System containing 6 transiting planets around a sunlike star. The system is too far away to be confirmed with dopplar spectrometry. Instead, the planets are close enough together that they were confirmed with Transit Timing Variation, which offered measurements for their mass and densities and compositions. The innermost five are Super-Earths and Neptunians and are compact and within Mercury-like distances, and are b (0.09 AU, 4 ME), c (0.10 AU, 13.5 ME), d (0.16 AU, 6.1 ME), e (0.19 AU, 8.4 ME), f (0.25 AU, 2.3 ME). The planets have surprisingly low density for such small planets and not likely rocky. The inner ones are likely mixture of rock/ice or rock/gas, while the outer three are so large for their mass that they have to have a lot of hydrogen/helium. Their outer shells are probably fluffy, while cores are rock hard. The outermost giant g is just outside Mercury's distance (0.46 AU, 1 MJ) and doesn't perturb neighbors enough for its mass to be calculated. They are all coplanar and have low eccentricities, none are in resonance, and the system is more compact than any other known system. Systems discovery prompted a briefing of Kepler's overall status.
  • NN Serpentis System - Old binary star system with two planets. The binary star consists of a white dwarf and a red dwarf star that orbit each other very closely and transit each other. Variations in transit times have confirmed that two planets, inner planet (1.6 MJ, 7.7 years) and outer planet (6.6 MJ, 15.5 years) in 1:2 resonance (?), orbit both stars. A red, white, and two colored objects all around reminds astronomers of a game of Snooker. The stars originally orbited each other every two years. After the primary star became a Red Giant, it swelled up and enveloped the Red Dwarf in its outer envelope. This friction caused the primary star to lose 75% of its mass and the stars were drawn inwards to form a tight binary. The primary star then became a white dwarf star about a million years ago. The gravity lost by this star might have destabilized any planets orbiting them. It's possible that the planets were formed after the primary star sluffed off much of its mass. An earlier planet was announced, but disproven.

Systems Containing Planets Detected with TTVEdit

  • Kepler-9 System (Sep 2010) - Contains the 6th planet found by Kepler and the first star containing multiple transiting planets. The first system where transit times noted to vary due to interaction between planets, pioneering the transit timing variations method of confirmation. Has a hot Super-Earth that could be used to test the core accretion theory and two Saturn-sized planets. The two giant planets could have pushed the super Earth towards the star, which was unable to get the gasses needed form a Jupiter sized planet as the dust near the star rapidly dispersed.

Other Systems with TTVEdit

  • Kepler-36 System - A star with two planets that get extremely close to each other. The inner planet b is a rocky super Earth at 0.115 AU, while the outer c is a mini Neptunian at 0.128 AU. C gets close enough to b that it can appear twice as large as the full moon. Their gravitational effects are large, causing large transit timing variations. They are in near 7:6 resonance. They approach each other every 97 days. The tidal effects are much greater than the Moon's on Earth, and might trigger volcanism. One question is if they formed on opposite sides of the snow line and how they might have drifted so close together. The pair have the largest density contrast of any measured system, with b being a rocky planet 8 times as dense as c. It's iron core likely has 30 percent of its mass, surrounded an atmosphere of % water and no more than 15% water. C may also have a rocky core, but surrounded by a much larger atmosphere of Hydrogen and Helium.

Systems with Transit TimingsEdit

  • OGLE-TR-113 System - A binary orange dwarf star 1800 ly away in a crowded star field in Carina. It contains the second discovered Very Hot Jupiter (34 hours, 0.023 au, 1.3 MJ) and one of the first discovered transiting planets. At one time it was the only known transiting Hot Jupiter with a surface gravity greater than Jupiter's. Between 2002 and 2009, its transit times were found to shorten by 60 ms per earth year. This indicates that it is slowly spiraling towards its sun, the first exoplanet found to be doing this, and may get ripped apart by its star in 1.4 million years, when its period is reduced to 10.8 hours. An alternate explanation may be that an unseen planetary companion is causing the timing differences.

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