From Dunlap Institute for Astronomy and Astrophysics (CA) : “2021 Serving Up the Universe on a Plate”

From Dunlap Institute for Astronomy and Astrophysics (CA)


University of Toronto (CA)


Meaghan MacSween
Communications and Multimedia Officer
Dunlap Institute for Astronomy & Astrophysics,
University of Toronto

Press contacts:

Michael Blanton

Juna Kollmeier

Gail Zasowski

They may not look like much — just metal disks 80 centimetres (30 inches) across with some etched markings and hundreds of small holes — but round aluminum “plates” like this one from the Sloan Digital Sky Survey (SDSS) have been vital to mapping our Universe for more than 20 years.

A plate from the SDSS-III BOSS survey, against a zoomed-in background of itself, showing the holes and the annotations used to help plug in the optical fibres. Credit: Sloan Digital Sky Survey (US).

“The large number of objects in the sky that we have been able to observe using these plates has revolutionized many fields of astronomy, including the structure of our own Milky Way, the giant black holes at the centres of galaxies, and the evolution of the Universe as a whole,” says Dr. Jo Bovy. Bovy is an Associate at the Dunlap Institute for Astronomy and Astrophysics, and a Professor at the David A. Dunlap Department of Astronomy and Astrophysics, who has been involved with SDSS for over a decade.

The plates enabled the SDSS to use one of the most powerful techniques in astrophysics: splitting the light from an object up into the rainbow of its constituent colours to create a graph called a “spectrum,” which shows how much light of different energies the object emits.

Studying the spectrum of a galaxy can tell us details like how far away it is; how long ago its stars formed; and even how those stars orbit the supermassive black hole at the galaxy’s centre. The spectrum of the gas falling into that black hole can help us calculate how big the black hole is and how quickly it is growing. For an individual star, a spectrum can tell us its temperature; the chemical elements of which it is made; and how quickly it is moving towards or away from us. Multiple spectra of the same star over time can even be used to detect the presence of orbiting exoplanets or faint companions.

Astronomers have studied spectra of objects in the sky for centuries, but over time, a problem appeared. Traditionally, astronomers relied on tiny slits in metal sheets to pass the light from single — or at most, a few — stars or galaxies into one spectrograph (a device that measures a spectrum), often a laborious process. As sky surveys got bigger and needed to collect spectra for more and more stars and galaxies, it became impractical to wait for spectrographs to collect all the data using these traditional methods. A new approach was needed.

The solution came at the end of the 1990s, when astronomers and engineers from the SDSS began to drill hundreds of holes in large aluminum plates, each hole positioned to line up with a star or galaxy towards a particular patch of the sky as shown in this video of SDSS plates being drilled.

A video showing the production of Sloan Digital Sky Survey plug plates in the Physics Instrument Shop at The University of Washington. Plates are drilled, cleaned, and measured before being shipped to Apache Point Observatory. Once installed on the SDSS 2.5m telescope, optical fibers carry light from each hole to a spectrograph. This allows for simultaneous spectroscopic observations of hundreds to thousands of objects in a single exposure. Each plate represents a patch of sky three degrees across (about 6 times the diameter of the full Moon), and each hole aligns with an astronomical object in that seven degree squared field.
Videography and Editing by Gaelen Sayres and Mary Kawamura.
Music: Williamson – Hello Mr. Hoshi.

When the plate was set at the back of the telescope, an optical fibre, carefully plugged by hand into each hole as shown in this video of observers plugging fibers into an SDSS plate, carried the light from the star or the galaxy into a spectrograph. This new system allowed several hundred spectra to be collected at the same time, dramatically increasing the speed at which objects in the sky could be measured.

The final plate of the SDSS plate program sits at the base of the Sloan Telescope at the Apache Point Observatory in New Mexico, USA. The coloured fibres visible below the plate have been plugged into their holes and will carry the light to the waiting instruments. Credit: J. Burchett.

In fact, SDSS-IV Director Mike Blanton explains that “the very first batch of data we used in early 2000 was almost as big as any of the previous redshift surveys ever done, and that was just from the first month or two of observations!”

Since those early measurements, more than twelve thousand plates have been drilled; hand-plugged; and observed. That’s a lot of metal — if all of these plates were piled together, their combined weight would equal that of 12 African bull elephants — or, for astronomers, a cube of white dwarf star material just under four centimetres (one and a half inches) on each side. All those plates would contain enough metal to make 4.3 million soda cans. All of these plates were drilled by engineers at the University of Washington’s (US) machine shop, and each hole in each plate was plugged in by hand by staff at one of the SDSS’s telescopes in New Mexico and Chile.

Sloan Digital Sky Survey telescope (US) at Apache Point near Sunspot, New Mexico Altitude 2,788 meters (9,147 ft.)

Apache Point Observatory (US), near Sunspot, New Mexico Altitude 2,788 meters (9,147 ft).

The appearance of the plates has evolved over time as the SDSS started new surveys; built new spectrographs; and even started using different telescopes. Many of the plates from recent years have more than one thousand holes each; or have holes for fibres from multiple spectrographs at the same time; or have holes that can accommodate bundles of dozens of optical fibres packed together. All told, more than 5.3 million individual holes have been drilled, each to within a tolerance of 10 micrometers (4 ten-thousandths of an inch). If you had to count all of these holes one-by-one, it would take you more than 60 straight days with no breaks.

What have we learned from the photons that passed through all those holes? “SDSS brought about the equivalent of an industrial revolution in astronomy – providing data for millions of stars, galaxies and quasars,” explains Dr. Ted Mackereth, Banting-Dunlap-CITA Fellow and member of the collaboration. “With data on these large scales, we are able to make truly statistical statements about how our Universe has formed and evolved. SDSS has provided deep insights on many scales in astrophysics, from planets to galaxies, to the large scale cosmic web of our Universe.” You can learn more about all the amazing results of the SDSS from our list of press releases.

One of the best parts of all this information is that it is available any time to anyone anywhere. “All of the data obtained by SDSS are made public for every astronomer, and every person on the planet, to use,” says Bovy. “In fact, many of the most exciting discoveries using SDSS data have been made by people outside the collaboration, including members of the public as part of the Galaxy Zoo project.”

In addition to the vast scientific knowledge and online data troves enabled by this system, SDSS plates have provided a way for countless schoolchildren and members of the public to interact with real astronomical hardware and data. “To date, the SDSS’s Plates for Education program has distributed several hundred plates — all of which have been used to observe the sky — to schools, museums, and other educational institutions around the world,” explains Romina Ahumada, who leads these SDSS educational efforts in Chile.

Now, after over two decades of using these plates to support its data collection (literally and metaphorically), the Sloan Digital Sky Survey is moving to a new era — one in which tiny robots will position each optical fibre to match the location of a star; galaxy; supermassive black hole; or other target. This is the perfect time to look back at the monumental scientific contribution of the plates, as the team plans for the next major developments that will be enabled by the new, even faster system.

“The plates have been amazing”, explains Juna Kollmeier, Director of U Toronto Canadian Institute for Theoretical Astrophysics [Institut canadien d’astrophysique théorique] (CA) as well as the Director of the brand-new fifth phase of the SDSS project (SDSS-V). “In graduate school, I worked with the first ones, and it’s humbling to think of all we have learned and all we still have to discover.”

Although observations with the SDSS plates have now ended, the survey looks ahead to an even brighter future. SDSS-V observations have already begun using a sophisticated system in which robots repeatedly arrange and rearrange the optical fibres allowing far more objects to be observed in far shorter times.

Kollmeier continues, “With SDSS-V and its robots, we will now be able to fully probe the entire sky with spectra, repeatedly in time, and make that data available to the world. How does the Universe change over days, weeks, or even years?”

David Schlegel, a key developer of SDSS’s spectroscopy program and the Principal Investigator of the SDSS-III BOSS survey, holds up a newly drilled plate. Credit: DOE’s Lawrence Berkeley National Laboratory (US).

See the full article here .


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Dunlap Institute campus

The Dunlap Institute for Astronomy & Astrophysics (CA) at University of Toronto (CA) is an endowed research institute with nearly 70 faculty, postdocs, students and staff, dedicated to innovative technology, ground-breaking research, world-class training, and public engagement. The research themes of its faculty and Dunlap Fellows span the Universe and include: optical, infrared and radio instrumentation; Dark Energy; large-scale structure; the Cosmic Microwave Background; the interstellar medium; galaxy evolution; cosmic magnetism; and time-domain science.

The Dunlap Institute (CA), University of Toronto Department of Astronomy & Astrophysics (CA), Canadian Institute for Theoretical Astrophysics (CA), and Centre for Planetary Sciences (CA) comprise the leading centre for astronomical research in Canada, at the leading research university in the country, the University of Toronto (CA).

The Dunlap Institute (CA) is committed to making its science, training and public outreach activities productive and enjoyable for everyone, regardless of gender, sexual orientation, disability, physical appearance, body size, race, nationality or religion.

Our work is greatly enhanced through collaborations with the Department of Astronomy & Astrophysics (CA), Canadian Institute for Theoretical Astrophysics (CA), David Dunlap Observatory (CA), Ontario Science Centre (CA), Royal Astronomical Society of Canada (CA), the Toronto Public Library (CA), and many other partners.

U Toronto Dunlap Dragonfly telescope Array (CA) at its home at high-altitude observing location New Mexico Skies hosting facility at 7300′ altitude

NIROSETI team from left to right Rem Stone UCO Lick Observatory Dan Werthimer, University of California-Berkeley (US); Jérôme Maire, U Toronto; Shelley Wright, University of California-San Diego (US); Patrick Dorval, U Toronto; Richard Treffers, Starman Systems. (Image by Laurie Hatch).

The University of Toronto(CA) is a public research university in Toronto, Ontario, Canada, located on the grounds that surround Queen’s Park. It was founded by royal charter in 1827 as King’s College, the oldest university in the province of Ontario.

Originally controlled by the Church of England, the university assumed its present name in 1850 upon becoming a secular institution.

As a collegiate university, it comprises eleven colleges each with substantial autonomy on financial and institutional affairs and significant differences in character and history. The university also operates two satellite campuses located in Scarborough and Mississauga.

University of Toronto has evolved into Canada’s leading institution of learning, discovery and knowledge creation. We are proud to be one of the world’s top research-intensive universities, driven to invent and innovate.

Our students have the opportunity to learn from and work with preeminent thought leaders through our multidisciplinary network of teaching and research faculty, alumni and partners.

The ideas, innovations and actions of more than 560,000 graduates continue to have a positive impact on the world.

Academically, the University of Toronto is noted for movements and curricula in literary criticism and communication theory, known collectively as the Toronto School.

The university was the birthplace of insulin and stem cell research, and was the site of the first electron microscope in North America; the identification of the first black hole Cygnus X-1; multi-touch technology, and the development of the theory of NP-completeness.

The university was one of several universities involved in early research of deep learning. It receives the most annual scientific research funding of any Canadian university and is one of two members of the Association of American Universities (US) outside the United States, the other being McGill(CA).

The Varsity Blues are the athletic teams that represent the university in intercollegiate league matches, with ties to gridiron football, rowing and ice hockey. The earliest recorded instance of gridiron football occurred at University of Toronto’s University College in November 1861.

The university’s Hart House is an early example of the North American student centre, simultaneously serving cultural, intellectual, and recreational interests within its large Gothic-revival complex.

The University of Toronto has educated three Governors General of Canada, four Prime Ministers of Canada, three foreign leaders, and fourteen Justices of the Supreme Court. As of March 2019, ten Nobel laureates, five Turing Award winners, 94 Rhodes Scholars, and one Fields Medalist have been affiliated with the university.

Early history

The founding of a colonial college had long been the desire of John Graves Simcoe, the first Lieutenant-Governor of Upper Canada and founder of York, the colonial capital. As an University of Oxford (UK)-educated military commander who had fought in the American Revolutionary War, Simcoe believed a college was needed to counter the spread of republicanism from the United States. The Upper Canada Executive Committee recommended in 1798 that a college be established in York.

On March 15, 1827, a royal charter was formally issued by King George IV, proclaiming “from this time one College, with the style and privileges of a University … for the education of youth in the principles of the Christian Religion, and for their instruction in the various branches of Science and Literature … to continue for ever, to be called King’s College.” The granting of the charter was largely the result of intense lobbying by John Strachan, the influential Anglican Bishop of Toronto who took office as the college’s first president. The original three-storey Greek Revival school building was built on the present site of Queen’s Park.

Under Strachan’s stewardship, King’s College was a religious institution closely aligned with the Church of England and the British colonial elite, known as the Family Compact. Reformist politicians opposed the clergy’s control over colonial institutions and fought to have the college secularized. In 1849, after a lengthy and heated debate, the newly elected responsible government of the Province of Canada voted to rename King’s College as the University of Toronto and severed the school’s ties with the church. Having anticipated this decision, the enraged Strachan had resigned a year earlier to open Trinity College as a private Anglican seminary. University College was created as the nondenominational teaching branch of the University of Toronto. During the American Civil War the threat of Union blockade on British North America prompted the creation of the University Rifle Corps which saw battle in resisting the Fenian raids on the Niagara border in 1866. The Corps was part of the Reserve Militia lead by Professor Henry Croft.

Established in 1878, the School of Practical Science was the precursor to the Faculty of Applied Science and Engineering which has been nicknamed Skule since its earliest days. While the Faculty of Medicine opened in 1843 medical teaching was conducted by proprietary schools from 1853 until 1887 when the faculty absorbed the Toronto School of Medicine. Meanwhile the university continued to set examinations and confer medical degrees. The university opened the Faculty of Law in 1887, followed by the Faculty of Dentistry in 1888 when the Royal College of Dental Surgeons became an affiliate. Women were first admitted to the university in 1884.

A devastating fire in 1890 gutted the interior of University College and destroyed 33,000 volumes from the library but the university restored the building and replenished its library within two years. Over the next two decades a collegiate system took shape as the university arranged federation with several ecclesiastical colleges including Strachan’s Trinity College in 1904. The university operated the Royal Conservatory of Music from 1896 to 1991 and the Royal Ontario Museum from 1912 to 1968; both still retain close ties with the university as independent institutions. The University of Toronto Press was founded in 1901 as Canada’s first academic publishing house. The Faculty of Forestry founded in 1907 with Bernhard Fernow as dean was Canada’s first university faculty devoted to forest science. In 1910, the Faculty of Education opened its laboratory school, the University of Toronto Schools.

World wars and post-war years

The First and Second World Wars curtailed some university activities as undergraduate and graduate men eagerly enlisted. Intercollegiate athletic competitions and the Hart House Debates were suspended although exhibition and interfaculty games were still held. The David Dunlap Observatory in Richmond Hill opened in 1935 followed by the University of Toronto Institute for Aerospace Studies in 1949. The university opened satellite campuses in Scarborough in 1964 and in Mississauga in 1967. The university’s former affiliated schools at the Ontario Agricultural College and Glendon Hall became fully independent of the University of Toronto and became part of University of Guelph (CA) in 1964 and York University (CA) in 1965 respectively. Beginning in the 1980s reductions in government funding prompted more rigorous fundraising efforts.

Since 2000

In 2000 Kin-Yip Chun was reinstated as a professor of the university after he launched an unsuccessful lawsuit against the university alleging racial discrimination. In 2017 a human rights application was filed against the University by one of its students for allegedly delaying the investigation of sexual assault and being dismissive of their concerns. In 2018 the university cleared one of its professors of allegations of discrimination and antisemitism in an internal investigation after a complaint was filed by one of its students.

The University of Toronto was the first Canadian university to amass a financial endowment greater than c. $1 billion in 2007. On September 24, 2020 the university announced a $250 million gift to the Faculty of Medicine from businessman and philanthropist James C. Temerty- the largest single philanthropic donation in Canadian history. This broke the previous record for the school set in 2019 when Gerry Schwartz and Heather Reisman jointly donated $100 million for the creation of a 750,000-square foot innovation and artificial intelligence centre.


Since 1926 the University of Toronto has been a member of the Association of American Universities (US) a consortium of the leading North American research universities. The university manages by far the largest annual research budget of any university in Canada with sponsored direct-cost expenditures of $878 million in 2010. In 2018 the University of Toronto was named the top research university in Canada by Research Infosource with a sponsored research income (external sources of funding) of $1,147.584 million in 2017. In the same year the university’s faculty averaged a sponsored research income of $428,200 while graduate students averaged a sponsored research income of $63,700. The federal government was the largest source of funding with grants from the Canadian Institutes of Health Research; the Natural Sciences and Engineering Research Council; and the Social Sciences and Humanities Research Council amounting to about one-third of the research budget. About eight percent of research funding came from corporations- mostly in the healthcare industry.

The first practical electron microscope was built by the physics department in 1938. During World War II the university developed the G-suit- a life-saving garment worn by Allied fighter plane pilots later adopted for use by astronauts.Development of the infrared chemiluminescence technique improved analyses of energy behaviours in chemical reactions. In 1963 the asteroid 2104 Toronto was discovered in the David Dunlap Observatory (CA) in Richmond Hill and is named after the university. In 1972 studies on Cygnus X-1 led to the publication of the first observational evidence proving the existence of black holes. Toronto astronomers have also discovered the Uranian moons of Caliban and Sycorax; the dwarf galaxies of Andromeda I, II and III; and the supernova SN 1987A. A pioneer in computing technology the university designed and built UTEC- one of the world’s first operational computers- and later purchased Ferut- the second commercial computer after UNIVAC I. Multi-touch technology was developed at Toronto with applications ranging from handheld devices to collaboration walls. The AeroVelo Atlas which won the Igor I. Sikorsky Human Powered Helicopter Competition in 2013 was developed by the university’s team of students and graduates and was tested in Vaughan.

The discovery of insulin at the University of Toronto in 1921 is considered among the most significant events in the history of medicine. The stem cell was discovered at the university in 1963 forming the basis for bone marrow transplantation and all subsequent research on adult and embryonic stem cells. This was the first of many findings at Toronto relating to stem cells including the identification of pancreatic and retinal stem cells. The cancer stem cell was first identified in 1997 by Toronto researchers who have since found stem cell associations in leukemia; brain tumors; and colorectal cancer. Medical inventions developed at Toronto include the glycaemic index; the infant cereal Pablum; the use of protective hypothermia in open heart surgery; and the first artificial cardiac pacemaker. The first successful single-lung transplant was performed at Toronto in 1981 followed by the first nerve transplant in 1988; and the first double-lung transplant in 1989. Researchers identified the maturation promoting factor that regulates cell division and discovered the T-cell receptor which triggers responses of the immune system. The university is credited with isolating the genes that cause Fanconi anemia; cystic fibrosis; and early-onset Alzheimer’s disease among numerous other diseases. Between 1914 and 1972 the university operated the Connaught Medical Research Laboratories- now part of the pharmaceutical corporation Sanofi-Aventis. Among the research conducted at the laboratory was the development of gel electrophoresis.

The University of Toronto is the primary research presence that supports one of the world’s largest concentrations of biotechnology firms. More than 5,000 principal investigators reside within 2 kilometres (1.2 mi) from the university grounds in Toronto’s Discovery District conducting $1 billion of medical research annually. MaRS Discovery District is a research park that serves commercial enterprises and the university’s technology transfer ventures. In 2008, the university disclosed 159 inventions and had 114 active start-up companies. Its SciNet Consortium operates the most powerful supercomputer in Canada.