The Discovery

The VISTA (Visible and Infrared Survey Telescope for Astronomy) is a telescope designed to observe the Milky Way’s deep structures by wide-field, high resolution imaging at infrared wavelengths. It recently demonstrated its capabilities when it allowed scientists to discover a previously unknown component of our galaxy from a survey it took between 2010 and 2014. Before, the central bulge of the Milky Way was thought to consist of old stars. The new data shows that it apparently contains 655 variable stars called Cepheids, which are young stars that expand and contract periodically, changing their brightness as they do.

The Cepheids

The time taken for a Cepheid to brighten and fade again is longer for those that are brighter and shorter for those that are dimmer. A complete cycle can take anywhere from a few days to many months. This allowed scientists to use Cepheids as an effective way to measure the distances to, and map the positions of, distant objects in the Milky Way and beyond. Out of the 655 discovered, 35 were found to be “classical Cepheids” which are much younger. After gathering information on the brightness, pulsation period, and distances of these 35, it was revealed that their ages range from 25 to 100 million years old.

This new component to our galaxy had remained unknown and invisible to previous surveys as it was buried behind thick clouds of dust. The discovery would not have been made without the power of VISTA.


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