Astronomers have discovered a star that is extremely poor in chemical elements and likely formed shortly after the first generation of stars.
Billions of years ago, the universe was shrouded in darkness. It was only with the appearance of the first stars—known as Population III—that space became transparent and light began to spread. However, none of these earliest stars have been observed to date.
Astronomers have now discovered the closest possible analogue—a star extremely poor in chemical elements that likely formed immediately after the first generation, reports the website “Science Alert.” It belongs to the so-called Population II stars and is extremely rare.
The object, named PicII-503, is the most iron-poor star ever discovered outside the Milky Way. It is located in the ancient galaxy Pictor II, which is more than 10 billion years old.
“The discovery of a star that clearly preserves the heavy elements from the first stars is at the very limit of what is possible, given the extreme rarity of such objects,” says astrophysicist Anirudh Chitti of Stanford University.
In the early universe, there was almost no variety of elements—mainly hydrogen and helium. The first stars began to create heavier elements through nuclear fusion, and when they exploded as supernovae, they scattered them throughout space. This is how subsequent generations of stars are formed.
The older a star is, the fewer “metals” (as astronomers call all elements heavier than helium) it contains.
PicII-503 is located about 150,000 light-years away in a small, faint galaxy orbiting the Milky Way. Pictor II is a so-called “fossil” galaxy—all of its stars are very old, and no new stars have formed there for billions of years.
Analysis shows that the star contains about 43,000 times less iron and 160,000 times less calcium than the Sun, but surprisingly high levels of carbon.
This chemical “signature” suggests that it formed from the remnants of an unusually weak supernova, in which the heavy elements remained in the core while the lighter ones were ejected into space.
The discovery offers a rare glimpse into the earliest processes of element formation in the universe and may help shed light on the origin of the oldest stars in the Milky Way’s halo.
“The most exciting thing is that we are observing the result of the earliest element formation in a primordial galaxy. This is a fundamental discovery,” Chiti emphasized. “It links the origin of the most metal-poor stars in the Milky Way to the influence of the first generation of stars.” | BGNES