Schott's speciality glass is playing a key role in uncovering the far-reaching answers of space.

Spectrographs in the Hobby–Eberly Telescope Dark Energy Experiment (HEDTEX) have been composed of Schott's Borofloat glass.

HEDTEX, held at the Austin McDonald Observatory (University of Texas at Austin), uses 156 state-of-the-art spectrographs that serve as the eyes into the universe’s to map the three-dimensional positions of one million galaxies.

These spectrographs use optical mirrors based on Borofloat glass – the floated borosilicate glass made by specialty glass expert Schott.

They will capture the full spectrum of light, measure the distances between galaxies at different times in the early universe, and reveal its composition.

With those measurements, scientists can deduce the rate of the universe’s expansion and further understand the physics of dark energy.

Borofloat’s high transparency, visual quality and optical clarity, and its thermal resistance are the key performance features helping to observe the universe.

The temperature stability of this glass is crucial to the HETDEX project because the Hobby-Eberly Telescope, the world’s third largest optical telescope is located more than 6,600 feet above sea level.

It therefore experiences seasonal temperature and weather fluctuations throughout the year, including snow in the winter and hot sunshine throughout the summer.

Thanks to the low coefficient of thermal expansion, Borofloat resists the challenging expansion and contraction forces that such change of temperatures would typically cause.

Additionally, Schott’s specialty glass boasts high chemical durability and excellent mechanical strength, mainly due to the addition of higher amounts of boron oxide in its composition which strengthens the chemical bonds within the glass network.

The added boron oxide gives Borofloat glass a low light refraction behaviour, which together with the material’s superior transmission is a key requirement for precise spectrograph measurement results.

Furthermore, light transmission in glasses will be significantly influenced by iron oxide impurity levels, and Borofloat has the lowest level of iron impurity of all industrial float glass materials in the market.

Pictured: Prototype of the spectrograph used for HEDTEX. It uses optical mirrors based on Borofloat glass from Schott. Source: Courtesy of Martin Harris/McDonald.