When the universe was just 100 million years old, or less than 1% of its present age, the very first stars may have formed. We must now look for hints regarding their presence in cosmic sources closer to Earth since the fast expansion of space has obscured their light since then.
Researchers from Japan, Australia, and the United States discovered that a "distinctive combination of heavy elements" in the light coming from clouds around a far-off quasar could have only originated from one source: the massive explosion of a first-generation star.
Depending on how old they are, every star that we can see is categorized as either Population I or Population II. While Population II stars are older with fewer heavy elements, Population I stars are younger and have more heavy elements.
The oldest stars, known as Population III stars, are considerably older, and even the most advanced technology cannot see them because of their great cosmic distances at the time of their birth. We can only speculate as to what they could have looked like at this time.
According to scientists, the first stars were very enormous, brilliant, and hot—possibly hundreds of times as massive as our Sun.
Population III stars would be solely composed of the lightest gases if there had never been a history of significant cosmic events to produce elements heavier than lithium. At that time, the only elements in the universe were hydrogen, helium, and a trace amount of lithium, which was discovered in the primordial gas that remained after the Big Bang. Heavier elements could only appear when the earliest stars themselves disintegrated in ferocious intensity.
Pair-instability supernovae, a speculative sort of super-supernova that is only feasible in such massive stars, are most likely how those initial stars ended their lives. Unlike earlier supernovae, this one would blow everything outward in an ever-expanding cloud rather than leaving behind stellar relics like a neutron star or black hole.
The overall impact is good because it may have provided ancient interstellar space with the heavy elements required for the development of rocky planets like our own, allowing life as we know it.
However, the light from those old mega-explosions has faded into the distance, leaving little more than a hazy cloud with a complicated mixture of materials for astronomers on Earth who are now trying to learn about Population III stars.
That material mixture could eventually disintegrate into something new. The authors of the current research utilized near-infrared spectrograph data from one of the most remote known quasars, a sort of active galactic nucleus or the very bright core of a young galaxy, to look for indications of such a concentration of star dust.
The researchers point out that this quasar's light had been hurdling through space for 13.1 billion years before it reached Earth, which means we are seeing the quasar as it appeared 700 million years ago.
A spectrograph is a device that collects and separates incoming light into its individual wavelengths, in this instance from a celestial object. This may be used to identify the components of an item in the distance, albeit it's not always simple to do so.
The authors note that the brightness of lines in astronomical spectra might depend on variables other than the amount of an element, which may make it more difficult to pinpoint certain elements.
But astronomers Yuzuru Yoshii and Hiroaki Sameshima, both from the University of Tokyo, who were two of the study's authors, already had a solution to this issue.
The study team's approach, which makes use of wavelength intensity to calculate the relative abundance of elements, enables them to examine the make-up of the clouds around this quasar.
Analysis of the clouds, which contained 10 times more iron than magnesium in comparison to our Sun, found an oddly low ratio of magnesium to iron. According to the researchers, it served as a signal that the material in question came from a first-generation star's catastrophic explosion.
According to co-author Yuzuru Yoshii, an astronomer at the University of Tokyo, "it seemed evident to me that the supernova candidate for this would be a pair-instability supernova of a Population III star, in which the whole star explodes without leaving any relic behind."
The discovery that a pair-instability supernova of a star with a mass around 300 times that of the Sun produces a magnesium to iron ratio that accords with the low value we calculated for the quasar made me happy and a little startled.
Yoshi and his colleagues point out that at least one other putative trace of a Population III star was discovered in 2014, but they contend that this latest discovery is the first to provide such solid evidence.
If what they discovered is accurate, this study may help to shed light on how matter changed over the course of the universe. More observations will be required to look for comparable characteristics in other celestial objects, they say, in order to be certain.
It's possible that not all of those observations need to originate from distant quasars. Even though Population III stars are extinct from the cosmos, evidence may still be there due to the lifetime of their supernova leftovers, which includes our own local universe.
According to co-author Timothy Beers, an astronomer at the University of Notre Dame, "We now know what to search for; we have a roadmap."
"We would expect to discover evidence for it if this occurred locally in the very early Universe, which it should have done."
The Astrophysical Journal reported the results.
Comments
Post a Comment