An artist’s depiction showing the distribution of Cepheids as blue dots across the Milky Way. Noticeable in the centre is an area devoid of Cepheids, meaning it contains very few young stars. Credit: The University of Tokyo
Our understanding of the structure and the distribution of stars across the Galaxy will have to be readdressed, according to a group of scientists who discovered a “stellar void” at its centre.
A study has found a region that is devoid of a type of young star called Cepheids.
Cepheids are useful for astronomers as they enable the measurement of distances in the Universe.
They are relatively young, between 10 and 300 million years old, and pulsate regularly.
The length and regularity of these pulsations is related to their luminosity, so astronomers can work out how bright the star actually is, measure how bright it appears from Earth, and thus calculate how far away it is.
A group of astronomers led by Prof Noriyuki Matsunaga of the University of Tokyo pointed a near-infrared telescope towards the centre of our Galaxy, in order to hunt for Cepheids amongst the cosmic dust that normally hides them from optical light observations.
They found a distinct lack of Cepheids in a region stretching about 8,000 lightyears from the centre, suggesting that no stars are being formed in this area.
While it is already known that Cepheids can be found closer to the galactic centre, these observations suggest a ring-shaped absence farther out.
Co-author Giuseppe Bono says:
"The current results indicate that there has been no significant star formation in this large region over hundreds of millions years.
The movement and the chemical composition of the new Cepheids are helping us to better understand the formation and evolution of the Milky Way."