The first stars in the universe are not as old as they are previously believed. Data from the European Space Agency's (ESA) Planck space telescope suggest that these ancient cosmic objects came into existence nearly 150 million years later than experts previously thought.

Between the years 2009 and 2012, Planck made a detailed study of the cosmic microwave background (CMB), the light released 380,000 years after the Big Bang, which scientists believe occurred about 14 billion years ago. As the universe expanded, the CMB spread across the sky and this light can be seen today at microwave lengths.

The unprecedented and detailed study of the CMB has allowed scientists working with Planck to release high resolution maps of this ancient light's temperature. The Planck team also studied readings of the CMB's polarization as an independent experiment for confirming results.

The data from Planck telescope confirmed the standard cosmological picture of the universe with high accuracy. The CMB data also provided scientists with hints about the history of the universe.

The observations of the CMB polarization made by the Planck space telescope revealed that the so called cosmic dark ages, the period when fogs made up of hydrogen atoms filled the cosmos, ended about 550 million years after the Big Bang so the period when the light from some of the first stars and galaxies lit up the cosmos and ended this dark ages started more than 100 million years later than previously estimated.

"While these 100 million years may seem negligible compared to the Universe's age of almost 14 billion years, they make a significant difference when it comes to the formation of the first stars," said Marco Bersanelli, from Italy's Università degli Studi di Milano.

Once the first stars started to shine, their light interacted with cosmic gas causing the atoms to turn back into electrons and protons marking a phase dubbed the "epoch of reionization." Since the stars and galaxies prompted the beginning of reionization, scientists said that the new measurements suggest when the stars and galaxies started to form.

The new data from Planck are crucial because earlier studies of the CMB polarization appeared to show that the first stars dawned at an earlier period placing the start of the reionization about 450 million years after the Big Bang.

"These are only a few highlights from the scrutiny of Planck's observations of the CMB polarisation, which is revealing the sky and the Universe in a brand new way," said Planck project scientist Jan Tauber. "This is an incredibly rich data set and the harvest of discoveries has just begun."