Revamp of

As part of the transition from SDSS-III to SDSS-IV we have just launched a revamped version of the website.

The site is redesigned to represent the entire SDSS, from the beginning through today. We hope that it provides a good balance between presenting our amazing results so far and our exciting future.

The original SDSS website is still available at, and the SDSS-III website is still available at

Congratulations to the web team on the successful transition of the sites.

Passing the Baton – SDSS-III to SDSS-IV

Tonight marks the official start of the fourth phase of the Sloan Digital Sky Surveys (SDSS-IV), and the end of SDSS-III.  


SDSS-III ran from 2008-2014 and made a major upgrade of the SDSS spectrographs. SDSS-III contained four interweaved surveys: BOSS focussed on mapping the clustering of galaxies and intergalactic gas in the distant universe;  SEGUE-2 and APOGEE surveyed the dynamics and chemical evolution of the Milky Way; and MARVELS observed the population of extra-solar giant planets. Over the full survey, SDSS-III took more than 2 million spectra, all of which will be released in a final SDSS-III Data Release (DR12 for the SDSS) in January 2015. 


SDSS-IV will run from 2014-2020, comprising three surveys, eBOSS, APOGEE-2 and MaNGA. eBOSS will work to extend precision cosmological measurements to a critical early phase of cosmic history; APOGEE-2 will expand the survey of the Galaxy across both the northern and southern hemispheres, and MaNGA will for the first time using the Sloan spectrographs to make spatially resolved maps of individual galaxies. 

We’d like to take this chance to congratulate the SDSS-III collaboration on a successful set of surveys, and wish SDSS-IV all the best for the future.

The 2014 Shaw Prize in Astronomy Recognizes Key Measurements of Cosmic Structure by 2dF and SDSS

The 2014 Shaw Prize in Astronomy has been awarded to Daniel Eisenstein, John Peacock, and Shaun Cole “for their contributions to the measurements of features in the large-scale structure of galaxies used to constrain the cosmological model including baryon acoustic oscillations and redshift-space distortions.” For more details on the Shaw Prize see

Daniel Eisenstein, the director of SDSS-III, remarks that “although this is a tremendously gratifying personal recognition, it is also a wonderful recognition of the SDSS/BOSS and 2dFGRS collaborations that have created these exquisite surveys and pushed forward the science of large-scale structure. It is a great honor for our field and our teams!”

Shaun Cole and John Peacock were key members of the 2dF Galaxy Redshift Survey (2dFGRS) which together with the work of Daniel Eisenstein and his SDSS collaborators made the first detections of the baryon acoustic oscillation pattern in the distribution of galaxies in the Universe. Baryon acoustic oscillations are an imprint from fluctuations of matter and light in the early Universe. By measuring the apparent size of this pattern at different cosmic eras, astronomers are studying the nature and amount of dark matter and dark energy that govern our expanding Universe.

SDSS congratulates all of the winners of this year’s Shaw Prize in Astronomy!

SDSS-III Director Elected to National Academy of Sciences

It is a great pleasure to share the news that the Director of SDSS-III, and long time member of SDSS, Daniel Eisenstein (Harvard University) has been elected to the National Academy of Sciences!


Daniel Eisenstein

The SDSS is delighted, and feel this is a well a deserved recognition testament to Daniel’s scientific accomplishments and leadership.  

Daniel wants to emphasize that he feels this recognition is also a recognition of the impressive scientific scope of the Sloan Digital Sky Survey, in all its iterations, which has been the context for key aspects of Daniel’s scientific and leadership accomplishments.  

So congratulations to the SDSS-III Director and also to all those who have helped make all phases and surveys of the SDSS a success over the past decades.

The other three NAS electees this year in astronomy are Fiona Harrison, Steve Schectman, and Joseph Silk.

Please join us in congratulating all four astronomers on this honor and accomplishment!

BOSS Completes its Main Survey of Distant Galaxies and Quasars!

The SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS) has completed its main survey of galaxies and quasars. With 1.35 million luminous red galaxies and 230,000 quasars across 10,200 square degrees of the sky, BOSS has exceeded the number of objects and sky area goals from the original SDSS-III proposal.

Reaching this milestone involved the hard work and efforts of many people. In particular, the mountain and observing staff at Apache Point Observatory have been worked hard and efficiently to observe 2,300 plates with the new BOSS spectrograph in 4.5 years of dark time.


The coverage map of the completed BOSS main survey in equatorial coordinates with (RA, Dec)=(90,0) in the center of the image. Completed areas are shown in light blue and yellow. The red area is a 10,500 deg^2 region from which observations were selected. The project goal was to observe the 10,000 deg^2 footprint above declination -3 deg. A 200 deg^2 region was added between declinations of -3 deg to -7 deg to provide overlap with the Dark Energy Survey.

For the remaining 3 months of SDSS-III, the BOSS spectrograph continues to observe new interesting classes of objects as part of a set of ancillary proposals that were internally competed within the SDSS-III collaboration.

All of SDSS-I, SDSS-II, and SDSS-III/SEGUE observed 1.84 million survey-quality spectra with the original SDSS spectrograph during the timeframe 1999-2009. SDSS-III DR12 will be released publicly in 2014 December and the final BOSS data in DR12 is expected to exceed 2.7 million survey-quality spectra, including calibration targets, stars, repeated observations, and ancillary programs.

The Most Precise Measurement Yet of the Expanding Universe

More exciting news from the SDSS! A worldwide team of SDSS astronomers has completed the most precise measurement of the expanding universe ever. The result was announced just hours ago at the meeting of the American Physical Society in Savannah, Georgia.

Click on the illustration below to go to the SDSS press release describing this exciting news!


Yellow lines showing light paths pass through circles of increasing size. Each              circle shows in purple the structure of galaxies in the universe at some point in the past.

An illustration of how astronomers used quasar light to trace the expansion of the universe.

Seeing Beyond: Gail Zasowski and the Inner Milky Way

The inner galaxy, inconveniently obscured by dust, has long been shrouded in mystery – until now. The SDSS-III’s APOGEE (Apache Point Observatory Galaxy Evolution Experiment) survey uses infrared light (light with wavelengths longer than our eyes can perceive) to cut through the dust and see previously-hidden parts of our galaxy. Astronomers from the APOGEE survey are now surveying more than 100,000 red giant stars all over the Milky Way. Data from this large range of stars, including highly accurate measurements of velocities and chemical compositions, will allow astronomers to finally unravel the history of the Milky Way.

Photo of Gail Zasowski in front of a mountain

Dr. Gail Zasowski

But how do we know which stars to survey? We want to find red stars, but interstellar dust makes many stars appear redder than they actually are. That reddening is different in different parts of the Galaxy, so choosing a consistent sample of stars throughout can be difficult. Stars must be “targeted” for observation with great care. This is where Dr. Gail Zasowski, the target selection coordinator of APOGEE, comes in.

Zasowski has been interested in astronomy for a long time. Imagine a young girl visiting the National Air Space Museum in Washington, walking with her father. The father takes his daughter to a mural of the Solar System and starts explaining to her what the planets are. But before he can even start naming them, the young girl rattles off, “Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto!” Gail Zasowski was born to be an astronomer.

Zasowski attended the University of Tennessee, where she earned a Bachelor of Science degree in physics, and double majored in Latin. After taking a few astronomy courses and spending a summer in an astronomy Research Experience for Undergraduates (REU) at the University of Rochester, Zasowski decided to apply to graduate school for astronomy. “I definitely came to grad school not knowing as much astronomy as my classmates,” admitted Zasowski. And yet, as a graduate student at the University of Virginia, Zasowski discovered that a life doing research and making new discoveries in the world of astronomy was indeed where she belonged.

The stars aligned for Zasowski at Virginia when she took some classes with Steve Majewski, principal investigator of APOGEE, and asked him to be her Ph.D. advisor. Zasowski’s thesis work dealt with the different factors that affect the absorption of starlight by interstellar dust. “It depends on wavelength, but how it depends on wavelength depends on properties of the dust itself, such as the size and shape of the grains,” Zasowski said. “My first work with Steve was on seeing how these behaviors changed as a function of the dust’s position in the galaxy.”

The SDSS-III telescope and the sky

The SDSS-III telescope at Apache Point Observatory, high on a ridge in eastern New Mexico. This image shows constellations labeled in the sky. Image credit: Steve Majewski.

Towards the second half of her graduate career, Zasowski’s familiarity with interstellar dust led her to further involvement in the APOGEE survey. “I was spending so much time working with APOGEE that Steve suggested I should just do it officially. So for the last two and a half years of grad school I was the Target Selection Coordinator of the survey,” Zasowski explained.

The goal of the APOGEE survey is to look at red giant stars in all parts of the galaxy, but interstellar dust absorbs and reflects blue light more effectively than red. The problem lies in the fact that since the amount of dust is unknown, the observer does not know how accurate the perceived color of the star is. If a star looks very red, is that because the star really is red, or is it because there is a lot of dust in the way? The solution to this problem lies in the fact that there are some wavelengths of light for which most stars emit about the same amount of light – so any apparent differences in stars at those wavelengths must be due to the dust. We can then use that knowledge to calculate how the dust affects stars at the wavelengths we really are interested in.

Zasowski wrote the software that measures all the stars in a patch of the sky, corrects the measurements for the effects of the dust, and chooses which stars there should be observed further by APOGEE. In addition to stars, Zasowski’s software looks for the large number of other interesting objects that APOGEE is well-suited to find, including newborn stars and ancient star clusters in other galaxies. “One thing that’s interesting about the software,” said Zasowski, “Is that things are always evolving. Every time we think that the software is done and that we can handle all special cases, someone will come up with some other interesting special case that we hadn’t considered.”

Zasowski holding the APOGEE logo. The logo shows the word "APOGEE" inside a white ellipse, with the O as a magnifying glass on the Milky Way

Gail Zasowski standing in front of the APOGEE spectrograph holding the APOGEE project logo, which she designed. Image credit: Ricardo Schiavon.

Zasowski has also been heavily involved with some of the science results coming out of APOGEE. For example, she worked with David Nidever on the discovery of a new group of stars near the center of the Milky Way. Using APOGEE observations, Nidever and Zasowski measured the velocities of stars near the Galactic center, unexpectedly discovering a population of fast-moving stars that matched computer models of stars forming a long, narrow “bar” in the inner Galaxy. Another of Zasowski’s studies led to a new approach to studying “diffuse interstellar bands” (DIBs), an as-yet-unexplained feature seen in stellar spectra, arising from interstellar material of unknown chemical makeup. The wavelength coverage of APOGEE, and the distance that the survey probes through the Galaxy, helps Zasowski use these lines to measure Galactic properties in a whole new way.

“I’m also really interested in public outreach,” said Zasowski enthusiastically. She recently became a postdoc; after spending a year at Ohio State University, she will be spending the remainder of her three-year fellowship at Johns Hopkins University. She is funded under a National Science Foundation Fellowship, a part of which is devoted to education and public outreach. This past summer, she helped run a week long space camp in Columbus, Ohio. “Astronomy is the gateway science because it’s easy to understand and easy to get excited about, so it’s a really good way to get people into science,” said Zasowski. Zasowski hopes that her education and public outreach efforts will inspire another young astronomer, just as she was inspired as a young girl at a science museum.

AAS Awards Highlight 3 Astronomers Using SDSS Data

The American Astronomical Society has awarded three of its society prizes to scientists who have used SDSS data extensively in their work.

1) Chris Lintott (Oxford University and Adler Planetarium) was awarded the 2014 biennial Beatrice M. Tinsley Prize for creative and innovative contributions to research.

“With great insight and creativity, he created a transformative approach to science by engaging nonscientists in cutting-edge research via He demonstrated the unique capabilities of ‘crowdsourcing’ to attack otherwise intractable problems and, in the process, created a unique educational tool that is also an unparalleled public-outreach phenomenon.”

SDSS data served as the main source for the GalaxyZoo project that started the wildly successful Zooniverse enterprise. Other key SDSS people involved in setting up GalaxyZoo include Karen Masters (University of Portsmouth) now serving as the GalaxyZoo Project Scientist, Daniel Thomas (University of Portsmouth), Kate Land (Oxford), Kevin Schawinski (Oxford), Jordan Raddick (Johns Hopkins University), Alex Szalay (Johns Hopkins University), Anže Slozar (Brookhaven National Lab), Steven Bamford (University of Nottingham), Bob Nichol (University of Portsmouth), and Jan Vandenberg (Johns Hopkins University). For some history on the GalaxyZoo project and its evolution into Zooniverse see by Fortson et al.

We also congratulate two scientists whose PhD theses were based on SDSS observations and who received AAS young-astronomer awards based in significant part on the work that came out of their theses and subsequent developments.

2) Nadia Zakamska (Johns Hopkins University) was awarded the 2014 Newton Lacy Pierce Prize for research in observational astronomy by an young scientist
“for her multi-wavelength work on Type II quasars, which has characterized these energetic sources in detail and led to the current “standard model” of quasars. […] Her observational and theoretical work has shown that “feedback” from AGN is occurring on scales of tens of thousands of light-years.”

SDSS data were central to Dr. Zakamska’s PhD work on quasars and continued efforts in this area.

3) Chris Hirata (Ohio State University) was awarded the Helen B. Warner Prize for research by a young astronomer
“for his remarkable cosmological studies, particularly his observational and theoretical work on weak gravitational lensing, one of the most important tools for assessing the distribution of mass in the universe. […] His work is facilitating the next generation of important cosmological experiments.”

Dr. Hirata’s PhD thesis on gravitational lensing was heavily based on analysis of SDSS data.

SDSS congratulations and recognizes these three excellent scientists along with all of the 2014 AAS award recipients.

Breaking SDSS News: A One-Percent Measure of the Universe

We are here live at the American Astronomical Society meeting in National Harbor, Maryland, where this afternoon the SDSS announced some exciting new results. We have used Baryon Acoustic Oscillations (BAOs) to measure the most precise distances to galaxies all the way across the universe. This illustration shows how this technique works: we know from the early history of the Universe that galaxies are more likely to be separated by 450 million light-years than 350 or 550 million. We can use that knowledge to make highly accurate distance measurements, which tell us about the nature of the Universe we live in.


Image credit: Zosia Rostomian, Lawrence Berkeley National Laboratory

Read more about it in our press release!

News coverage about this story is already starting to appear. Check back on this page for links to stories!

BOSS Winter Collaboration Meeting at Lawrence Berkeley National Laboratory

Over 80 astronomers attended the 2013 BOSS Collaboration Meeting held at the Lawrence Berkeley National Laboratory, from December 9th to 11th. During the meeting we had active and involved discussions about at all the great results that are coming out from the over 2 million spectra already taken with the BOSS spectrograph.

BOSS_201312_collaboration_meeting_thumb(Image Credit: Berkeley Lab – Roy Kaltschmidt)

Final discussions on the Data Release 11 papers, as well as preparation for the upcoming final BOSS Data Release 12, were two of the main topics in the meeting, but there were also many new exciting results from the different working groups covering topics such as quasars, galaxies, and clouds of gas in distant galaxies.

The conference dinner, at the Chabot observatory, was preceded by a great talk on exoplanets by Sarah Ballard, and followed by observations of Jupiter’s satellites using telescopes almost a hundred years old. On Wednesday afternoon, the first BOSS soccer championship ended up with a tight score (Quasars 3 – Lyman alpha 5), surprisingly no injuries and a lot of fun!

SDSS Social Media in Chinese

A massive thank you to Qingqing Mao a PhD student from Vanderbilt who is running SDSS Social Media sites in Chinese (Simplified Mandarin). We have both Facebook and Weibo (Chinese version of Twitter) accounts for SDSS. Below is a wordl of the most common characters used by these accounts. The blue characters in the middle are a phonetic translation of “Sloan”. “Tian Wen” also appears many times – literally “sky language/culture” – meaning astronomy (e.g. “tian wen xue” means the study of astronomy).


SDSS-III APOGEE spectra motivate improved lab-based spectroscopy

A recent Nature editorial argues for the need to support lab-based basic spectroscopy to fully understand the wealth of astronomical data coming from surveys such as SDSS-III and its APOGEE spectrograph.  In particular such spectra contain many atomic and molecular transitions only very rarely studied in Earth-based laboratories.  Understanding the relative strengths of these transitions will be important in using them to fully measure the abundance of elements and molecules in stars in our Milky Way galaxy.

Hide and Seek: SDSS-III Astronomers Map Elusive Intergalactic Gas

Today’s blog is a guest post by SDSS astronomer Guangtun Zhu of Johns Hopkins University

For more than a decade, SDSS astronomers have been mapping all the galaxies of the Universe – but what about the space between the galaxies? How can we map whatever cold, dark gas might be there?

The top of image shows light traveling from a distant quasar to the SDSS telescope. The bottom shows the impact of light absorption on the quasar's observed spectrum.

When we look at spectra of distant quasars, we learn not only about the quasars, but also about whatever the light passed through on its journey from quasar to telescope. In this case, absorption lines in the quasar spectra reveal gas in intergalactic space. The SDSS has obtained spectra for more than 200,000 quasars, providing a map of gas absorption across the sky.

Mapping the distribution of matter between galaxies is one of the greatest challenges in modern astronomy. When we look up in the sky, even with the largest telescopes, we see mostly dark space between galaxies that appears to be totally empty. Theories of cosmology predict that most of the matter in the Universe should be in the form of diffuse gas between galaxies, but actually detecting that gas is extremely challenging because it emits essentially no light.

A team of SDSS-III scientists led by me and my Johns Hopkins colleague Brice Ménard has just finished a study that takes on this difficult task. Using new advanced statistical techniques, we have been able to detect the very weak but clear signature of magnesium in intergalactic space. Those techniques allowed us to find how the amount of gas around galaxies changes with increasing distance from the center of the galaxies. Our findings are summarized in a paper submitted to the journal Monthly Notices of the Royal Astronomical Society, and available on the arXiv preprint server:

“The Large-scale Distribution of Cool Gas around Luminous Red Galaxies”

To detect gas in the intergalactic space, we used its absorption effects. When light from a distant source passes through a gas cloud, photons at a specific energy are absorbed, leaving a valley in the source’s spectrum.

The light sources we used are quasars – very bright objects powered by supermassive black holes at the centers of distant galaxies. Quasars are the brightest things in the Universe, so they do an excellent job of shining through the intergalactic gas we want to study. And the SDSS has obtained spectra of more than 200,000 quasars, letting us see the signal of intergalactic gas all over the sky.

Most of the gas absorption, however, is so weak that its signature is hidden by variations in the quasar spectra themselves. So even with the huge dataset we have, we had to use new statistical techniques to find the gas. Using a sample of one million galaxies that lie between us and thousands of distant quasars, we looked at the place in the quasar spectrum corresponding to magnesium. Our statistics showed us that, on average, the quasars appeared to be missing 0.01% of the magnesium. In other words, out of every 10,000 photons emitted by a quasar at the right wavelength, 9,999 made it to Earth, and one didn’t show up because it was absorbed by magnesium between galaxies. This effect is way too small to see for any individual quasar – we can only find it by averaging the light from all the quasars, all over the Universe.

So now that we know that the intergalactic gas is there, what’s next? The “standard model” of cosmology makes certain predictions about how matter is distributed in the Universe. So far, the model’s predictions have matched up extremely well with observations of the distribution of galaxies. Will the model also correctly predict the distribution of intergalactic gas? Our research shows, for the first time, that the large-scale distribution of gas in the Universe is consistent with the standard model.

A graph with average distance from galaxy center on the x-axis and amount of gas on the y-axis. Data points go from top left to bottom right.

This graph shows how the amount of gas around an average galaxy changes with increasing distance. The blue points show our latest results. The green and orange lines show the predicted amount of gas associated with that galaxy (green) and the galaxies around it (orange). The blue curve is the sum of the orange and green curves. The graph shows that the observed amount of gas matches predictions very well.

New surveys such as SDSS-IV, the next phase of the SDSS, are now being prepared and will soon provide us with even more data to help us map the distribution of matter in space with even higher sensitivity. Astronomers will be able to map different elements around different types of galaxies, across cosmic time. These observations will lift the veil of the universe and reveal the overall distribution of matter. In addition, they will provide new clues to a better understanding of the formation and evolution of galaxies like our own Milky Way.

The future is bright for studies of dark regions in space.