Five small planets for the ancient star Kepler-444

Artistic concept of the Kepler 444 system (Image Tiago Campante/Peter Devine)
Artistic concept of the Kepler 444 system (Image Tiago Campante/Peter Devine)

Using data collected by the Kepler space telescope, a group of researchers led by asteroseismologists from the University of Birmingham discovered five planets orbiting the star Kepler-444. They’re small rocky planets: the smallest has a size similar to Mercury, the largest has a diameter about three-quarters of the Earth. Another special feature is that the star Kepler-444 is very ancient, with an age estimated to around 11.2 billion years.

The star Kepler-444 was studied using the technique asteroseismology. In simple words, the researchers exploited the frequencies of the star’s natural oscillations that are caused by sound waves trapped inside it. A complex analysis of these frequencies allowed to calculate its size, its mass and its age. It’s a really old star, born when the universe was very young.

Last year came the announcement of the discovery of two super-Earths orbiting Kapteyn’s star, which has an age similar to Kepler-444. Kapteyn’s star is a red subdwarf, a really small star. Instead, Kepler-444 is an orange dwarf of spectral type K0 with a mass that is approximately three-quarters of the Sun. Its distance is around 117 light years from Earth.

The similarities of Kepler-444 with the Sun make the comparison between the two systems interesting. Dr. Tiago Campante of the University of Birmingham’s School of Physics, pointed out the implications of the discovery: the fact that Earth-sized planets were born so early in the history of the universe can give new perspectives regarding the possibility of existence of ancient life forms.

However, it seems unlikely that life emerged in the Kepler-444 system, or at least that’s what said Steve Howell, a scientist of the Kepler/K2 mission. The problem is that of the five planets even the one farthest from its star is closer to it than Mercury from the Sun. It’s too close to be within the habitable zone that would allow the birth of life forms similar to those on Earth with the right environmental conditions.

It’s possible that life forms completely different from those on Earth formed in very different conditions, unfortunately at this time we have no way to detect them. The discovery of the Kepler-444 planets is still very interesting. Professor Bill Chaplin, also of University of Birmingham’s School of Physics, pointed out that discoveries like this one are giving us the first glimpses of the variety of environments that can lead to the formation of small worlds. The patch to a more complete understanding of the formation of ancient planets in the galaxy is now unfolding.

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