Melbourne: Scientists may have found a new tool to trace the Sun’s journey through our galaxy, the Milky Way.
It takes the Sun and its family of planets about 220 million years to complete each orbit of the galaxy, but it can be quite difficult to detect the local interstellar medium, which the solar system’s travelling through, because it’s so tenuous and emits very little light.
Priscilla Frisch from the University of Chicago and Hans-Reinhard Mueller from Dartmouth College in Hanover, believe changes in the isotopes of some elements in Earth’s geologic record could hold clues about this journey.
They said that radioisotopes like carbon 14 and beryllium 10 are created when cosmic rays from outside our solar system slam into atomic nuclei in elements on Earth.
Frisch and Mueller said that if the theory works, other things like galactic clouds in the interstellar medium could also show up in the paleorecord.
Although it’s just a theory, the pair believes there’s evidence in the past 2 to 3 thousand years of a change in the local flux which seems to correlate with when the solar system entered the local interstellar cloud-cluster, a grouping of tiny clouds of atomic hydrogen which we are still travelling through.
They also claim there’s evidence of an earlier event about 18 thousand to 24 thousand years ago when the radio isotope levels also changed; and which seems to correspond with another cloud the solar system travelled through at the time.
"If the Sun travels through a very dense cloud of gas, the heliosphere would shrink down to something so small, the Earth’s orbit could actually take us outside the heliopause, the boundary between the heliosphere and the interstellar medium," ABC Science quoted Professor Naomi McClure-Griffiths from the University of Sydney and the CSIRO as saying.