Both orbit 1.5 million km from Earth’s second Lagrange point (L2) and both orbit it. ESA’s Gaia observatory has been at the location since January 8, 2014. Its objective is to map stars in our galaxy. On January 24, 2014, James Webb arrived eight years later. Gaia took a photograph of her new neighbor on February 18, as the spacecraft were separated by one million kilometers.
Francois Mignard from the Nice Observatory and Uli Bastian from the University of Heidelberg suggested that Gaia track down James Webb several weeks before it arrived at its destination. They discovered that the space telescope could occasionally be seen by the ESA observatory during its scan of the sky.
Gaia was not built to photograph celestial objects. Instead, it measures their movements, positions, distances and colors. It does have two telescopes, however, that can take photos of the sky in order to identify the objects it is interested in. Bastian and Mignard used them to take a photo of James Webb. They calculated that James Webb would be in Gaia’s view on February 18.
The observatory began scanning the sky that day and Mignard sent an email out to all those involved in the hunt. “JWST: We got it!” was the subject of the email. JWST stands to represent James Webb Space Telescope. Juanma MartinFleitas (Gaia’s calibration engine) sent another message to group a few days later. He said that he had identified the target and attached images of two tiny specks labelled “Webb candidates”. Bastian responded, “Your candidates can be renamed Webb.”
ESA released images showing that “very little reflected sun (from the telescope heat shield) reached Gaia. Thus the Webb appears as an insignificant, faint speck in Gaia’s two telescopes, with no visible detail.” The space agency said in a statement. Astrophysicists believe that the James Webb will be able to see the Universe at the time it was 13.5billion years ago, 300 million years after Big Bang.
