20th anniversary of first light for SDSS telescope

A map showing some of what the Sloan Digital Sky Survey has
discovered over the last twenty years. The dots show the
distance to various sky objects that the SDSS has
discovered. The horizontal axis of the map is labeled in
light-years, stretching from our own solar system to the
most distant reaches of the universe. Sample images at the
top show some of the things the SDSS has seen. Credit: V.
Belokurov, M. R. Blanton, A. Bonaca, X. Fan, M. C. Geha, R.
H. Lupton, the SDSS Collaboration

This week marks the twentieth anniversary of “first light”
for the telescope behind the Sloan Digital Sky Survey (SDSS),
which has gone on to create by far the largest
three-dimensional map of the Universe ever made. Early in the
morning of May 10th, 1998, the observers and engineers
pointed the Sloan Foundation Telescope to the celestial
equator and light went through to the survey’s exquisitely
sensitive camera. When dawn broke after a long night’s work,
SDSS observer Dan Long emailed his usual observer’s log
summarizing what happened. After describing the technical
details of the observations, and before noting a series of
newly identified problems to fix, he wrote: “Wow; What a

“That was the beginning of our survey, and we’re still going
strong twenty years later,” says Michael Blanton, a professor
at New York University and the Director of SDSS-IV. “We are now
planning our fifth generation, called SDSS-V, and we’re still
using the same Sloan Foundation Telescope.”

The telescope’s mirror, 2.5 meters (8 feet) in diameter, is
small by astronomy research telescope standards, but powerful
because it can see a large area of the sky simultaneously.
Astronomers have used it to make an enormous, highly-detailed
map – a map which covers one-third of the night sky, with
measurements of hundreds of thousands of Milky Way stars and
distances to more than four million galaxies. All the data
collected by the telescope is available free to anyone online,
and all images are open access under the SDSS’s Image Use

This map has played a key role in astronomical history, helping
astronomers learn about our Milky Way, other galaxies, distant
black holes, the nature of dark matter and dark energy and
myriad types of stars in ways never imagined when the project

The Sloan Foundation Telescope at Apache Point Observatory in
New Mexico, shown at time of first light in May 1998. An
early set of images is shown superposed on the sky behind it.
Credit: Dan Long (Apache Point Observatory

The SDSS has measured the universe’s expansion more precisely
than ever before and has mapped how galaxies and larger
structures grew over cosmic time, helping to establish our
current standard model of cosmology. It discovered some of the
nearest stars and the smallest companion galaxies to our own
Milky Way galaxy, revealing how our galaxy grew by
cannibalizing smaller galaxies. It has studied the Milky Way’s
disk of stars more completely than ever before, using infrared
light to peer through the obscuring dust. It has studied the
dark matter content of the Milky Way and distant galaxies, and
found some of the most distant quasars known.

And perhaps most importantly, the SDSS has achieved its
remarkable scientific discoveries while establishing a new way
of doing science. Since 2001, the project has made all its data
freely available to the public in a series of roughly-annual
releases of data – most recently with Data Release 14 in July
2017. The team who built and operated the survey recognized
that the data were far too rich for them to reap all the
science from it alone, and that maximizing the science return
would require the entire worldwide community of astronomers. As
a result, a generation of astronomers have grown up learning
their craft with the help of SDSS data. Close to ten thousand
astronomers have worked with SDSS data, publishing over eight
thousand scientific papers – thus making it the most broadly
used data set in astronomy.

Along the way, SDSS gained the support of numerous
institutions. One-quarter of the funding for SDSS comes from
the Alfred P. Sloan Foundation, and about five percent comes
from the U.S. Department of Energy. The rest comes from more
than fifty universities and research institutions on four
continents, all of whom consider it so vital to their
scientists that they contribute their time, effort, and
resources to become members of the project. The next step,
SDSS-V, will commence in 2020 and will continue to uncover the
unexpected by observing millions of stars, and black holes across the entire sky.

At the Apache Point Observatory, home of the Sloan Foundation
Telescope, astronomers will gather this Wednesday, 9th May
2018, to mark this anniversary, remember the early days of the
project, and discuss the impact it has had on the field of
astronomy. The telescope no longer hosts a camera, but it still
measures spectra of hundreds of celestial objects every night –
and is still operated by a dedicated on-site team of observers
and engineers. True to the online nature of the Sloan Digital
Sky Surveys over the last 20 years, this celebration will be
broadcast live on the internet, and involve collaboration
members past and present across all parts of the globe.

The core of the project – the people who get the data upon
which so many of the world’s astronomers depend – sits the team
of observers and engineers at Apache Point Observatory. A
handful of the original team that led the efforts in 1998 are
still with the project. Dan Long was promoted along the way to
Chief Telescope Engineer, a position from which he recently
retired. Many other members of the team have joined more
recently. But they all share the excitement that Dan Long
expressed the night of first light, and each night brings the
prospect of new discoveries that will change the way we see our
universe and make them and us say “Wow.”

Explore further:
Sloan Digital Sky Survey expands its reach

Provided by: Sloan Digital Sky Survey

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