The SDSS
The Sloan Digital Sky Survey is an international collaboration of scientists who have been working together since 2000 to map the positions of millions of objects on the sky. The survey uses a 2.5 meter telescope located at the Apache Point Observatory in New Mexico – the Sloan telescope. It is one of the most ambitious and influential astronomical surveys ever conducted and has surveyed about a third of the sky, obtaining optical images and spectra of astronomical objects. The SDSS has helped scientists measure properties and distances of these objects and has revolutionized our understanding of the universe by providing high-quality, publicly accessible data since the beginning of the project.
SDSS through time
The SDSS has gone through many phases from the 2000 to the present, each phase characterised by different funding, people, and broad science goals: SDSS-I/II (2000-2008), SDSS-III (2008-2014), SDSS-IV (2014-2021) and the most recent phase is SDSS-V which started in 2020. The most recent complete phase, SDSS-IV, was comprised of three different surveys: eBOSS, APOGEE-2 and MaNGA. MaNGA stands for Mapping Nearby Galaxies at APO and focused on producing spectra measurements across the entire face of many nearby galaxies.
APOGEE stands for Apache Point Observatory Galactic Evolution Survey and it mapped the Milky Way stars in an attempt to better understand how our galaxy formed and evolved. eBOSS stands for Extended Baryon Oscillation Spectroscopic Survey, it maps galaxies and quasars from when the universe was 3 to 8 billion years young! This period helps scientists understand dark energy and how it affects the expansion of the universe.
Together, these surveys in the fourth phase of the SDSS produced an extremely detailed map of the universe, covering nearby and very far away structures. The plates distributed by Plates for Education programme come primarily from the eBOSS survey, with some special plates coming from the MaNGA survey.
SDSS data
SDSS gathers two types of data: imaging or photometric data comprising of photographs of the sky with different filters in the optical band, and spectroscopic data comprising of optical spectra.
SDSS Plates
To capture the spectra of millions of objects, scientists had to come up with an efficient way of collecting data of many objects at the same time. That’s how the SDSS plates were born. You can learn more about plates and spectra in the next sections.
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All image credits to SDSS