A spectrograph begins to capture light from many stars at once


International collaboration to develop the Prime Focus Spectrograph (PFS) has marked a significant milestone in testing by successfully taking spectra of target stars.

The PFS will be mounted on the Subaru 8.2m Telescope on the summit of Mauna Kea, Hawaii. When finished, the instrument will use about 2,400 optical fibers to take simultaneous exposures of a large number of celestial objects in the night sky, such as stars and galaxies, and split their light into its various wavelengths. The resulting data set is called a “spectrum,” which tells researchers various details about a celestial object, including its motion, physical parameters, and age.

Using the PFS, researchers will be able to discover information that can only be seen with spectra and not visually in images. The team has been conducting tests on the telescope since 2018, but none have been more important than its latest test to capture light from celestial objects in the PFS.

In late September this year, the team conducted engineering observations at the Subaru Telescope, where they made raster scans. These scans allow researchers to test how well their instrument is aligned with the objects they should be capturing. The fibers are placed where the researchers believe the target objects should exist in the focal plane of the Prime Focus Instrument (PFI), then the telescope is blurred in a grid pattern on the sky and a spectrograph exposure is taken at each blurred position. . This allows the team to measure the discrepancy between the actual position of the fiber and the actual position of the target.

After starting to take data, the team continued to take more raster-scan datasets on many bright stars to correct for errors and apply possible optimizations, until they were finally satisfied that the instrument had been able to place the fibers fairly accurately on the stars. his objectives.

This milestone is still the result of a single field with a specific fiber configuration. The alignment of the fiber with the stars has not yet reached satisfactory levels.

“But this is clearly a very encouraging achievement. Based on the fact that we have been able to capture starlight from our target objects using the PFS, I would say that the team has achieved First Light Engineering and moved on to the next regimen of instrument commissioning. service,” said it’s a statement Naoyuki Tamura, PFS Project Manager and Associate Professor at the Kavli Institute for the Physics and Mathematics of the Universe project.