In a previous
thread, I stated that the number of detected exoplanets is increasing.
During this quest, astronomers have found odd planets, such as
PSO J318.5-22. Another planet that baffles astronomers, is Kepler-78b.
Measurements (
Sanchis-Ojeda, R. et al., 2013) have shown that Kepler-78b is an scorching exoplanet (surface temperatures of ca. 2700 K), with a radius of about 7400 km that orbits a Sun-like star in less than 9 hours.
Further analyses (
Pepe, F. et al., 2013) have indicated that Kepler-78b resembles Earth, because it weighs 1.86 times more than Earth and its density is estimated to be 5570 kg/m³, which is a bit more than the density of the Earth (5514 kg/m³).
What makes this planet so special, is explained by
ScienceDaily:
"Kepler-78b is a planet that shouldn't exist. This scorching lava world circles its star every eight and a half hours at a distance of less than one million miles -- one of the tightest known orbits. According to current theories of planet formation, it couldn't have formed so close to its star, nor could it have moved there."
The existence of this planet is a mystery, because when this planetary system was forming, the Sun-like star was larger than it is now.
As a result, the current orbit of Kepler-78b would have been inside the swollen star, which is impossible according to the current theories about planetary formation.
Yet, astronomers still have plenty of time to study the curious case of Kepler-78b, because predictions point out that it will be ripped apart by its star in about 3 billion years. Interestingly, the article states that it might be possible that, during the formation of the Solar System, a Kepler-like planet could have existed in our Solar System.
What do you think?
Sources:
Sanchis-Ojeda, R., et al. (2013), "Transits and occultations of an Earth-sized planet in an 8.5 hr orbit",
The Astrophysical Journal 774(1), pp. 54-62
Pepe, F., et al. (2013), "An Earth-sized planet with an Earth-like density",
Nature
Earth Fact Sheet
Lava world baffles astronomers: Planet Kepler-78b 'shouldn't exist'