By Andy Tomaswick
May 19, 2025
The pursuit of exoplanet via orbital mechanics is not easy. Many variables can have an impact on how a planet moves around its star, and to determine that affect a specific exoplanet requires a lot of data and a lot of modeling. A work of researchers recently managed by the Kaviya Parthasarathy of the National Tsing Hua University in Taiwan is trying to break through and determine what the transit timing variations (TTVS) causes from HAT-P-12B, which are generally known as puli.
Puli is a “Sub-Saturn” Exoplanet, which the Stern-Hat-P-12, also known as a comondor. Both the star and its planet are named after dog breeds when they are in the Venatici star cups and about 463 light years are from the earth. Nothing is particularly special about the star or planet, except that you have collected a lot of data on you.
The paper analyzed 46 light curves that watch Puli in front of Komondor. Some were previously published, while others, including some ground-based observations and some new data from the transit exoplanet survey satellite, have never been analyzed.
Fraser discusses transits, the exoplanet hunting technique with which puli was found.
The most striking characteristic of Pulis Transits was its variability. This feature, which was known in the literature as a transit -timing variations, was quite significant and came in a “amplitude” of 156 seconds variability, which means that the planet occasionally passed in front of the star over two minutes earlier or two minutes later, given a “normal” orbital period. That doesn't seem much to be, but the orbital mechanics are very precise, so that a lot of variation was definitely a sign of something else that affects the orbit of Pulis.
To find out what, the researchers used statistical analyzes. They tried four different orbital models to see which was the best. First, they looked at a “linear” model that represents a perfectly periodic transit. In view of the variability of the transit times, this model did not fit well with the data.
An orbital decay model that represents whether the planet's orbit slows down because it is pulled in the taverns was not particularly good. It was a slow but constant change rate that consistently changed in one direction in one direction during the observations.
Exoplanet research is shortly before the heating, as Fraser explains.
Another model, the APSIDAL model, tried to understand what would happen with a slightly eccentric orbit that could be reflected in different start and end times of the Pulis transit. This fit better than the other two models, but was not the best for the data.
This title goes to a sinus -shaped model that represents the gravitational influence of another planet on Puli's transit. This model has recorded a periodic signal in the TTVS, which was translated into an accompanying planet and a mass of around 2% of the Jupiter size over a period of 6.24 orbital days. The output of the sinus -shaped model estimated a TTV amplitude of 2.6 minutes, almost exactly on what it was actually.
In order to rule out other factors, the authors looked at the Applegate Mechanism, whereby changes in the star themselves could influence TTV measurements. This mechanism includes factors such as the magnetic activity of the star or a change in its “boss” or how much it can be expanded in its center, which could have a dramatic effect on the orbital timing of a continuous exoplanet. However, the predicted amplitude from this effect was only about 0.4 seconds, not approximately enough to explain the more than two -minute deviations in the data.
Fortunately, Komondor had collected enough data so that the authors could do this type of deep dive to discover a potential new planet – not every exoplanetary system is so happy. However, if we start collecting more data about exoplanet systems, there will undoubtedly be invisible accompanying planets that lurk in them. The more we can carry out the type of analysis described in work, the more we will probably find.
Learn more:
K. Parthasarathy et al.
UT – temperamental stars play with our exoplanet efforts
Ut – what is the transit method?
Ut – what are extrasolar planets?
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