Most of us know that our sun, along with Earth and the other planets of our solar system, formed roughly 4.6 billion years ago. The process began when a massive cloud of dust and gas collapsed on itself, creating compressed areas that attracted more matter. This gradually accreting mass heated up and then began to spin thanks to the force of gravity. The densest area in the center, around which the rest of the matter revolved, eventually became the sun, a ball of fusion-powered hydrogen and helium that allowed life to take hold on our planet.
Knowing a bit about the sun’s history raises some big questions: is the formation of our sun typical? Do some stars form faster or perhaps more slowly than our own sun? To get to the bottom of these questions, scientists have been trying to figure out ways to accurately determine the formation rate of stars. The rate changes depending on how much gas is in an interstellar cloud and how heavy and hot that gas is. With this information, scientists will be able to make other inferences about the properties and life cycle of the star, as well as to better understand the conditions under which stars are born. But measuring a star’s formation rate is easier said than done–until now.
Star-forming in the Eagle Nebula. Credit: NASA
Previous strategies included monitoring radio emissions at different wavelengths looking for what scientists call “tracers”—measurable particles of an interstellar cloud. But tracers, which can include dust and various molecules, particularly those that can outlast ultraviolet radiation, can be tricky—they can be absorbed by bigger areas of interstellar dust or be obscured by other unrelated emissions. Scientists needed a more accurate and consistent way of identifying and measuring tracers in order to devise a consistent methodology for calculating star formation rates.
Golden rings of star formation (captured by Hubble). Credit: ESA/Hubble & NASA; acknowledgment: R. Buta (University of Alabama)
Fatemeh Tabatabaei from the Instituto de Astrofisica de Canarias (IAC) led an international group of astronomers, including scientists from the Heidelberg and Bonn-based Max Planck institutes, to a breakthrough by using radio emissions “at intermediate frequencies between 1 and 10 GHz” as tracers for star formation rate calculations. The ability to pinpoint a finite range of effective frequencies for detecting the emissions and for avoiding factors that obscure tracers represent a significant stride in the groundwork necessary to understanding the process and speed of star formation. The group studied 52 galaxies using the 100-m Effelsberg radio telescope, which can detect fluctuations in radio emissions originating far, far away. The researchers believe that this approach will work on other galaxies, deepening astronomers’ understanding of star formation, as well as of the universe itself.
The findings also mean that even in the apparent silence of space, galaxies sound off when new stars are born. We just have to know how to listen.