We might be wrong about the pace of star creation in the Milky Way,
according to a study of the most energetic light in the galaxy.
The radioactive disintegration of isotopes created during star formation
results in gamma radiation, which show that stars are developing at a rate
of four to eight times the Sun's mass per year. Even though that may not
seem like much, the fact that it is two to four times higher than current
projections indicates that our galaxy may not be as quiet as we first
believed.
And since the rate at which stars are formed and perish can change a
galaxy's general chemical makeup, this has significant consequences for our
knowledge of the development of our galaxy and those around us.
Astrophysicist Thomas Siegert of the University of Würzburg in Germany is
the lead author of an article outlining the discovery, which has been
approved for publishing in Astronomy & Astrophysics and is already
accessible on the preprint website arXiv.
The more complicated components in our universe are made in stars. Atoms
are forged into ever-larger atoms by being smashed together in their
centers, which act as nuclear furnaces. These heavier elements are violently
ejected into interplanetary space during their violent deaths, where they
float in clouds or are absorbed by newly forming stars. They too undergo
energetic supernova blasts that create even heavier elements than their
centers are able to sustain.
Star births are also lively like their funerals. They originate from
compact clusters in interstellar dust and gas clouds, compressing under
gravity and voraciously slurping up material until there is enough pressure
and heat in their centers to spark fusion. They begin to produce strong
stellar winds that discharge particles into space as they move in this
direction, and streams of particles propelled from their poles are
accelerated along the magnetic field of the young star.
An element named aluminum-26, a radioactive form of aluminum, is one that
can be produced after a star dies. In terms of the cosmos, aluminum-26 has a
short half-life of 717,000 years. Additionally, it generates beta radiation
with a particular frequency as it degrades.
But the material masses that encircle freshly forming stars also contain a
sizable amount of aluminum-26-2. When matter enters a supernova faster than
the speed of sound, a shock wave develops, which produces cosmic rays. The
atom aluminum-26 can be created when the electrons interact with dust-borne
isotopes like silicon-28 and aluminum-27.
Therefore, scientists can approximate the rate at which stars that create
the isotope form and perish in the Milky Way and use that to establish an
overall rate of star generation by looking at the budget of gamma radiation
in the Universe generated by the radioactive decay of aluminum-26.
The Milky Way galaxy is thought to create stars at a pace of about two
Suns' worth of material per year, according to current estimates. That's
believed to be on average six or seven stars per year because the majority
of Milky Way stars are much less dense than the Sun.
The aluminum-26 gamma radiation in the galaxy was counted by Siegert and
his coworkers, and modeling was done to determine the most probable
mechanism for this light's abundance. They discovered that a star creation
rate of four to eight solar masses annually, or up to 55 stars on average,
provides the best match.
This estimate can still be improved because the models did not accurately
replicate the Milky Way's gamma radiation as it is presently detected and
because it is difficult to determine the source's location. Because of this,
the scientists were only able to provide an estimate for the star creation
rate rather than a precise mass.
The team's approach, though, offers hope for a greater comprehension of how
the Milky Way creates new stars. Counting the gamma radiation that is
produced during star formation could be a useful method of peeping behind
the veil since star formation is typically shrouded in dense gas and dust
that makes it difficult to see into.
The team's research has been accepted for publication in Astronomy
& Astrophysics, and is available on
arXiv.
