German astronomers have discovered a planetary system deemed a survivor of the very early universe. The ancient system is an astonishing 13 billion years old, and raises the question of how such early stars and planets might have formed.
At an age three times greater than Earth's, and a distance of 375 light-years away, the planetary system is a relic of the universe how it once was. Two planets, HIP 11952b and HIP 11952c, circle the star HIP 11952. The star is scarce in metals, made mostly of hydrogen and helium.
The low metal content is in stark contrast to the metal-rich stars that are usually associated with forming planets in large swirls of heavy elements, such as our own sun with 90 percent more heavy elements. As Johny Setiawan of the Max Planck Institute for Astronomy states, “So far there are only very few planetary companions detected around stars with low stellar metallicity.”
Setiawan is currently leading the study of this new planetary system.
The star HIP 11952 was formed when the universe was less than a billion years old itself at its dawn, still in a very primitive and alien state to how we know it today. Most of the elements now present, including the ones necessary for life on Earth, were forged over billions of years in stars, and spread across the universe when those stars' lives came to an end in the form of an explosive supernova. As the late Carl Sagan once put it, "We're made of star-stuff."
Astronomers were observing the star in the Cetus constellation when they noticed a wobble in the star's movement, only to find that the wobble was caused by the gravitational heave-ho of two orbiting exoplanets. The planet HIP 11952b, the larger of the two at about three times the size of Jupiter, circles the star every 290 days, while the smaller HIP 11952c, just under Jupiter's size, circles it every 7 days.
"This is an archaeological find in our own backyard. These planets probably formed when our Galaxy itself was still a baby.", continued Johny Setiawan in the journal of Astronomy and Astrophysics.
The knowledge of metal-poor planetary systems is nothing new to astronomers, however. Another system was discovered in 2010. It was seen as a purely unique occurrence, but this new finding shows that metal-poor systems may not be such a rare happening after all.
Artist’s conception of HIP 13044 and its exoplanet. A previously discovered metal-poor planetary system, it was formed in another galaxy that our own galaxy engulfed.
"In 2010 we found the first example of such a metal-poor system, HIP 13044. Back then, we thought it might be a unique case; now, it seems as if there might be more planets around metal-poor stars than expected.", states Veronica Roccatagliata, the principal investigator in the survey for metal-poor stars that led to the previous discovery. HIP 13044 is speculated to have been part of a galaxy formed when the universe was very young, that was eventually absorbed by our own galaxy.
This discovery raises many questions to the scientific community about how planets form, breaking old rules and ringing in new understandings of the early cosmos, and what it may teach us about the the universe we live in today.