Analysis of the most energetic light in the galaxy has shown that we may be wrong about the rate of star formation in the Milky Way. Gamma rays produced by the radioactive decay of isotopes produced during star formation indicate that stars form at a rate of four to eight times the mass of the Sun per year. This may not seem like much, but it is two to four times more than current estimates, suggesting that our galaxy is not as peaceful as we thought.

And this is important for our understanding of the evolution of our galaxy and those around us, because the rates at which stars are born and die can change the overall chemical composition of the galaxy.

Stars are factories that produce the more complex elements of our universe. Their nuclei are nuclear furnaces that split atoms into larger atoms. When they die, the throes of death hurl these heavy elements into interstellar space to be engulfed in clouds or absorbed by new stars forming. Supernova explosions are also energetic and produce elements that are too heavy for their nuclei to lift.

Like their death, the birth of stars is energetic. They form in dense clumps in clouds of interstellar dust and gas, collapse under the influence of gravity and greedily absorb material from the space around them until their cores have enough pressure and heat to ignite fusion. In doing so, they begin to emit powerful stellar winds that blow particles into space, and jets ejected from the particle poles accelerate through the baby star’s magnetic field.

One element known to result from the death of a star is a radioactive isotope of aluminum called aluminum-26. Aluminum-26 does not last long cosmically; It has a half-life of 717,000 years. And when it decays, it produces gamma radiation of a certain wavelength.

But aluminum-26 is also found in significant amounts in clouds of material surrounding newly formed stars. If the velocity of the material falling on the star exceeds the speed of sound, a shock wave is produced that produces cosmic rays. When the rays collide with isotopes such as aluminum-27 and silicon-28 in the powder, they can produce the aluminum-26 isotope. By looking at the gamma-ray budget in the universe from 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 this to determine the overall rate. star formation.

Current estimates of the rate of star formation in the Milky Way galaxy are that about two solar masses of material transform into stars each year. Since most of the stars in the Milky Way are much smaller than the mass of the Sun, it is estimated that there are an average of six or seven stars per year. Siegert and his colleagues did a count of aluminum-26 gamma-ray emission in the galaxy and ran simulations to see the most likely mechanism for producing the observed excess of this light. They found that a star formation rate of about four to eight solar masses per year is optimal; or up to about 55 stars per year.

This score can still be improved; the models did not exactly reproduce the Milky Way’s gamma radiation as currently observed; and the distance to the gamma-ray source can change the final estimate, but are difficult to predict. Therefore, researchers can only give a range of star formation rates, not an exact mass. Still, the team’s method holds promise for better understanding how the Milky Way creates new stars. Star formations are often obscured by dense gas and dust that is difficult to see; Counting the gamma radiation it produces can be an effective way of looking behind the curtain.