Exoplanet TrES-4b
Size comparison of TrES-4 with Jupiter. Image source: [1]
TrES-4b is located 1,400 light-years in the constellation of Hercules. It orbits around the star GSC02620-00648. The curious thing about this exoplanet is that although it is larger than Jupiter, it turns out to be less massive, so its density is very low, only 230 kg/m³ (kilograms per cubic meter). That is why some have described TrES-4b as the spongy exoplanet. The least dense planet in the solar system is Saturn which has a specific density of 690 kg/m³ being the only planet in our planetary system with a density lower than that of water (1000 kg/m³).
TrES-4b is what is known as a transient exoplanet, ie it passes directly in front of its host star, from Earth's line of sight. When a planet of that class passes between its star and Earth, the planet blocks some of the light from the star in a similar way to what happens when the Moon passes between the Sun and Earth during a solar eclipse. In the case of TrES-4b, this reduces starlight by 1%, a tiny but perceptible effect, even with the small telescopes of the TrES program.
The TrES-4b exoplanet performs a complete revolution around its parent star every 3.55 days. It is about 7 million kilometers from its star, the eighth part of the distance that separates Mercury from the Sun, so this unique gaseous planet is warmed by the intense light of its star to temperatures much higher than those supported by Mercury. It is believed that TrES-4b reaches about 1,300 degrees Celsius.
More details here: TrES-4b
