Rocky planets could have formed since the very beginning of the universe. Researchers report on April 24 in Nature Astronomy magazine which is a stellar nursery in a nearby galaxy has the necessary materials for such planetary formation .
The overall chemical composition of the tiny galaxy called the Small Magellanic Cloud is similar to that of the early universe. The finding suggests that rocky planets could have developed in the relatively pristine chemical environment that permeated space just a couple of billion years after the Big Bang.
The Small Magellanic Cloud is one of the Milky Way’s closest galactic neighbors, although it is very different from our galaxy. The tiny galaxy is much lower in heavy metals such as iron, magnesium and aluminum, which are crucial for the formation of rocky planets. This low-metal environment also mimics that of the early universe, an era before stars had enough time to forge heavy elements and eject them into space.
Because of the lack of these elements, astronomers were not sure whether rocky planets could form in the Small Magellanic Cloud. And previous telescopes did not have the ability to really study young stars with a mass less than or equal to the mass of the Sun, so astronomers could not measure the dust content in star systems, which is necessary to conclude whether planets can be born. But thanks to the sensitivity of the James Webb Space Telescope, or JWST, astronomers can now collect more light and see smaller, dimmer stars in greater detail.
Astrophysicist Olivia Jones and her colleagues used JWST’s infrared camera to examine a region of the Small Magellanic Cloud called NGC 346 where young stars form. “This is the first time we’ve actually been able to watch solar-sized stars form in an environment similar to the early universe,” says Jones of the Royal Observatory in Edinburgh.
The team found signs that a lot of dust is swirling around and falling on hundreds of stars in the region. As these dust particles orbit, they can begin to stick together and eventually coalesce to form rocky planets.
“One of the things we’d like to understand better is how the environmental context affects star formation and then, later, the population of the planet around these young, forming stars,” says Michael Meyer, an astronomer at the University of Michigan in Ann Arbor, which was not involved in the study.
Because the Small Magellanic Cloud is the closest example of a region of space with a significantly different chemical composition than the Milky Way, he says, it is the first touchstone for studying how star and planet formation depends on the stellar environment.
The metal-poor stellar environment in the Small Magellanic Cloud is comparable to that of distant galaxies that evolved about 11 billion years ago. During this period, which is called “cosmic noon”, there was a burst of star formation throughout the cosmos. If rocky planets could accumulate around stars in the Small Magellanic Cloud, the researchers suggest, such worlds could also form in the early years of the universe.
The young stars in NGC 346 are also relatively light. One reason scientists are interested in studying the possibility of planets forming around low-mass stars is that they are the most common type of star in the universe and the longest-lived, said Pennsylvania State astronomer Kevin Luhmann, who was not involved in the study. .
“They offer the longest timescale for life to form and survive on any planet around them,” says Luhmann. “If the most common star in the universe lived for only a million years and then exploded, that would be bad for life.” The fact that these types of stars can potentially form rocky planets, he says, bodes well for the development of life elsewhere in the universe.
Further research will focus on determining what chemical signatures can be found around the stars, Jones says. This could tell researchers what chemical elements any rocky planets are made of.
