(ORDO NEWS) — Gamma rays, produced by the radioactive decay of isotopes produced during star formation, show that stars in the Milky Way are formed at a rate of 4-8 solar masses per year. This is 2-4 times faster than astronomers thought.
More than 50 stars are formed in the Milky Way every year, according to new estimates.
It is known that one of the elements formed as a result of the death of stars is the radioactive isotope aluminum-26.
The life of aluminum-26 is short, from a cosmic point of view: its half-life is 717,000 years. And when it decays, it produces gamma radiation with a certain wavelength.
But aluminum-26 is also present in significant amounts in the clouds of material that surround newly forming stars.
If the speed at which matter enters the star exceeds the speed of sound, a shock wave is formed that generates cosmic rays.
When the beams collide with isotopes in the dust, such as aluminum-27 and silicon-28, they can produce an isotope of aluminum-26.
Star formation rate in the Milky Way
So, by studying the amount of gamma radiation in the universe created by the radioactive decay of aluminum-26, astronomers can estimate the rate at which isotope-producing stars form and die in the Milky Way, and use that to determine the overall rate of star formation.
Current estimates of the rate of star formation in the Milky Way galaxy are the equivalent of the masses of about two Suns turning into stars each year.
Since most of the stars in the Milky Way are much less massive than the Sun, it is estimated that on average, about six or seven stars a year form in our galaxy.
The authors of the new work analyzed the amount of aluminum-26 gamma radiation in the galaxy and ran simulations to see what star formation rate corresponds to the amount of this isotope.
Astronomers have found that the data best fits a star formation rate of four to eight solar masses per year, or up to about 55 stars per year.
This estimate can still be improved because computer models did not quite reproduce the Milky Way’s gamma rays as they are currently observed, and the distance to the source of the gamma rays may change the final estimate.
However, it is difficult to measure it. This is why the researchers only published the star formation rate range and not the exact mass.
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