The Potato Planet
Space is always fascinating. Scientists are making fascinating discoveries every day. One such recent discovery by ESA’s [European Space Agency] Cheops Mission found a Potato Shaped Exoplanet in the realm of WASP 103, the planet’s host star. Want to know why the planet’s got its nickname as Potato? and some more interesting facts on how they found such a planet. Let’s dive deeper into it.
Note: Cheops — CHaracterising ExOplanet Satellite is an ESA mission to get to know about exoplanets whose sizes range from that of Earth to Neptune.
Before getting to the exciting stuff, let’s cover some basic things like size, shape, and other properties.
- Name of the planet: WASP 103b
- Size: 2 times larger than Jupiter
- Mass: 1.5 times the mass of Jupiter
- Host Star: WASP 103, this star is 1.7 times larger and 200 degrees hotter than the Sun.
- Distance between WASP 103b and its host star: 50 times closer compared to our Earth and the Sun.
- It’s in the Hercules Constellation.
TIDAL TUG? WHAT IS THAT?
The Tidal force is a gravitational effect that stretches a body along the line towards the centre of mass of another body due to a difference in the strength of the gravitational field from the other body. Newton’s famous “Law of Gravitation” is the main governing factor for the deformation of the planet.
“Every particle attracts every other particle in the universe with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centres.”
Yep, Tidal Tug is the force that the earth experiences from the Sun and the Moon (not the Pokémon series), causing tides in the sea. The tidal tug that we experience is less significant — only a few inches from ground level due to the considerable distance between the Sun and earth. Therefore, there is no significant effect on the earth’s shape, and the tidal forces from the moon cause the ocean tides on earth. However, that is not the case for WASP 103b. Since it is 50 times closer to its host star than Earth, the tidal tug has a significant impact (around 125,000 times greater force than Sun’s effect on earth) on the planet’s shape, thus stretching it into potato/rugby shape.
ANOTHER REASON?
The centrifugal force also causes WASP 103b to deform for two reasons. The first is due to the planet’s composition. Since WASP 103b is similar to Jupiter, the deformation due to centrifugal force is much larger than that of the rocky earth. The second reason is that the planet’s velocity is so enormous due to its proximity to the host star, giving it a revolution period of 22 hours. Additionally, WASP-103b doesn’t revolve around its axis. This results in it being baked on one side and frozen on the other.
This begs the question: how did they find that the planet’s composition is similar to Jupiter?
LOVE NUMBER
How did they find that there is a planet deformed to this extent? As mentioned before, Cheops is on a mission to study exoplanets. The satellite collects the data of various exoplanets in the form of DIP IN LIGHT. When the planet comes in front of the host star, there will be a dip in the received light. This transit light curve that is collected is used to find the parameter the Love Number.
“The Love numbers (h, k, and l) are dimensionless parameters that measure the rigidity of a planetary body and the susceptibility of its shape to change in response to a tidal potential.”
Through the analysis of data from Cheops, HST — Hubble Space Telescope and Spitzer, scientists found the Love Number of WASP- 103b
which is similar to the Love number of Jupiter. Therefore, the planet’s internal structure and composition are similar to gas giant Jupiter.
MYSTERY MOTION?
There is a mystery in the motion of WASP 103b. Since the planet is very close to its host star, the orbital distance usually decreases. But, the recorded information shows that the orbital distance is increasing. Scientists are studying this mystery motion. A possible explanation is that it might be an Applegate effect.
The Applegate mechanism (Applegate’s mechanism or Applegate effect) explains long term orbital period variations seen in certain eclipsing binaries.
You can learn more about the mathematical model on LOVE Number, Applegate effect and about the Cheops mission from ESA’s website and the research paper from the journal Astronomy and Astrophysics.
Question to Ponder: What are the factors that account for the deformation of a planet in various scenarios?
