A major revision is required in our understanding of our Milky Way Galaxy according to an international team. Astronomers have found that there is a huge region around the center of our own galaxy, which is devoid of a type of young star called Cepheids.

The find suggests that, although there are Cepheids inside the Milky Way’s ‘heart’, there are no young stars in the surrounding Extreme Inner Disk region – an area that stretches roughly 8,000 light-years out from the galactic centre.

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.”