An international team of astronomers led by Guillem Anglada-Escudé from Queen Mary University of London has discovered two new planets around a nearby red dwarf star. Named for the Dutch astronomer who discovered it, Kapteyn’s Star is about 13 light years away in the southern constellation of Pictor, which makes it the 25th closest star to our own. Both of the new planets are “Super Earths” with at least five times the mass of Earth.
While newly discovered Kapteyn c is considered to be too cold for life because of its distance from the star, Kapteyn b is within the habitable zone where liquid water would be stable on the planet’s surface. If its atmosphere were like Earth’s, surface temperatures would be slightly cooler than ours. But given that it is more massive than Earth, it probably has a thicker atmosphere, and thus would likely be at least as warm as our own planet.
That isn’t the most interesting thing about the new discovery, however. Kapteyn’s Star and its planetary system are estimated to be 11.5 billion years old—two and a half times older than Earth and only about two billion years younger than the Universe itself. That makes Kapteyn b the oldest planet in the Habitable Exoplanets Catalog. It currently ranks 16th on the Earth Similarity Index.
Why is Kapteyn b so old? Although it’s only 13 light years away from Earth, it is thought to be part of a dwarf galaxy that was disrupted and absorbed by the Milky Way. The remnant of this dwarf galaxy is likely Omega Centauri, a globular cluster 16,000 light years from Earth that contains many similarly old stars.
One can only imagine life on a planet many billions of years older than Earth. How advanced might it be? Would we expect super-intelligent beings whose actions would appear like magic to us? Can we even be sure that life would have advanced beyond the microbial stage, let alone to a technologically advanced state? The longevity of a planet will positively impact its Biological Complexity Index, but we have no way of knowing for sure whether biological complexity actually exists on this planet.
And there’s a downside to old planets. The metallicity content, meaning the concentration of elements other than hydrogen and helium, was very low in the early days of the universe. The enrichment with heavier elements took place mostly through supernova explosions. Thus, Kapteyn b may not have the elementary chemistry needed for the origin of life. Either way, it will be an intriguing place to study further.