Heroes of the Helpdesk

They come in a steady stream: the requests for lost passwords, for aid in correcting a CasJobs query, for insight into the technical details of SDSS photometry, astrometry, and spectroscopy, for help with educational resources and SkyServer, and for general astronomical and database knowledge, all sent to helpdesk@sdss.org. Two or three times a day, they appear in the mailboxes of those on the helpdesk mailing list, representing the hopes and dreams of an astronomer, amateur, student, or professional, to use SDSS data to answer the big questions of the Universe (or at least to get more room on the server).

The helpdesk in action: Ben Weaver making SDSS science possible for yet another scientist.

The helpdesk in action: Ben Weaver making SDSS science possible for
yet another scientist.

The task falls to the volunteers, headed up and organized by Ben Weaver, Archive Scientist at New York University (right). Most questions are handled quickly by Ben, Ani Thakar, Archive Scientist at Johns Hopkins University, or Jordan Raddick, one of our Education Directors, also at Johns Hopkins. Promptness is easiest if the questioners have done us the kindness of including relevant information such as the context or URL they are using and the exact query. Occasionally questions about how parameters were derived or why there are changes between Data Releases requires the advice of other SDSS experts. In this case, Ben sends email to the relevant SDSS mailing list. Excellent answers are gratefully accepted from the wider collaboration, who really do know these data. Our thanks to everyone who has stepped up and contributed to making SDSS data scientifically valuable to an astonishing array of people. Above all, we wish to thank the helpdesk regulars. If you have sent an email to the helpdesk or if you know someone who has sent an email to the helpdesk (and you probably do, trust me), send a cheer their way.

How SDSS Uses Light to Understand Stars Inside and Out in the Kepler Field

Stars are not only fascinating objects in their own right — they also help us understand the history of our Milky Way galaxy. Our galaxy was created as dark matter’s pull brought gas together, and the gas formed stars and planets. As part of the APOGEE survey, we wish to map the Milky Way’s star formation throughout cosmic time. As stars died, many of the elements they fused in their interiors during their lives or death throes are mixed back into the remaining gas, changing its composition and the composition of subsequent generations of stars and providing the raw materials for planets (and humans!) and we are exploring this chemical history as well.

A small part of the spectra of a few of the stars observed by APOGEE. The dark lines are caused by absorption of atoms in the star's atmosphere (or sometimes the Earth's). A few of them are highlighted. The bright lines are caused by emission in the Earth's atmosphere ("night sky lines") These particular stars have also been observed by the Kepler satellite.

A small part of the spectra of a few of the stars observed by APOGEE. The dark lines are caused by absorption of atoms in the star’s atmosphere (or sometimes the Earth’s). A few of them are highlighted. The bright lines are caused by emission in the Earth’s atmosphere (“night sky lines”) These particular stars have also been observed by the Kepler satellite.

APOGEE studies stars by passing their infrared light through gratings that spread the light out in wavelength (think infrared rainbows). We do this for > 250 stars at once (one of the reasons why the APOGEE instrument is fantastic). We can tell a lot about stars from studying these spectra. For example, in an earlier blog post, we discussed how we can tell the surface temperature of stars from such data. Another very important property is the composition of the star, for example, how many atoms of iron, calcium, or oxygen it has relative to hydrogen. The image to the left shows a small part of the spectra we gathered for stars that were also observed by the Kepler satellite. The stars do not give off the same amount of light at each wavelength (=color) of light. Instead, there are many dark lines, which are created when atoms in a star’s atmosphere absorb light at very particular wavelengths. Each element has a different pattern of these absorption lines, and by measuring the depth of these lines (+ additional information and math), we can determine the composition of the gas out of which the star formed.

But this doesn’t tell us everything about the star! In particular, we can’t see inside the star where the original composition of the gas is being transformed from hydrogen into helium as the star ages. We have a good idea of how long it takes for a star with a certain mass and original chemical composition to run out of fuse-able hydrogen in its center (about 10 billion years in the case of a star with the mass and composition of the Sun). When that happens, the star undergoes a dramatic change, turning into a red giant or supergiant. So if we can determine the mass to go with the spectral  composition information for red giants that we observe, we can determine the age of those particular stars.

Measuring the mass of a star is hard work, but one possible technique is to use asteroseismology, which is the study of the waves that move through stars. In the outer parts of stars, these waves are actually sound waves that can evocatively be described as ringing the star like a bell (For more information see The Song of the Stars). The motions of these waves cause a star’s brightness to change by small amounts, and thus the frequency of these waves can be measured by studying the lightcurves of red giant stars. The Kepler satellite, in addition to studying many Sun-like stars looking for transiting planets, also measured the brightnesses over many years of thousands of red giants. The favorite frequencies of waves in different stars have been measured by members of the Kepler Asteroseismic Science Consortium. While much can be learned about the insides of stars from these data, we are particularly intrigued by the fact that how long and at what speed waves can move through the star depends on the star’s density and therefore (with some more math) its mass!

Combining together spectra from APOGEE and lightcurves from Kepler therefore gives us a way to figure out the ages of red giant stars in our Galaxy by measuring the masses and composition of stars that have just exhausted their hydrogen. In conclusion, songs and rainbows are good things.

This post is part of the SDSS Celebration of the International Year of Light 2015, in which we aim to post an article a month about how SDSS uses light in our mission to study the Universe. 

The Future is Now: Karen Masters Wins UK Award

Dr. Karen Masters, senior lecturer at the University of Portsmouth’s Institute of Cosmology and Gravitation and Director of Public Education and Outreach for SDSS-IV, has won the Women of the Future Science award. The Women of the Future Awards acknowledge successful young women in Britain and are handed out in fields ranging from business to arts and culture to science and technology. Karen (as we like to call her) received the award for her work
on understanding how galaxies form and evolve over the history of the universe. Karen uses a diverse set of tools, including the contributions of large number of citizen scientists looking at SDSS images of galaxies at the Galaxy Zoo (www.galaxyzoo.org) and the new data coming from the MaNGA survey of SDSS-IV (http://www.sdss.org/sdss-surveys/manga/). Karen is also one of the BBC’s “100 Women of 2014”, invited to share her thoughts and experiences as part of the BBC’s pledge to represent women better in their news reporting.


Dr. Masters accepting the award from the Rt Hon John Bercow MP,  Speaker of the House of Commons.

Dr. Masters accepting her award from the Rt Hon John Bercow MP, Speaker of the House of Commons, and Trui Hebbelink from Shell. 

For more information, see http://www.ras.org.uk/news-and-press/2527-dr-karen-masters-wins-women-of-the-future-award and http://www.bbc.com/news/world-29758792

SDSS hits the Big time

SDSS has made it big! How big? The Big 12! To explain a little more, especially for those who are not American college football fans, the Big 12 is a group of universities* that form a league in American college football. During broadcasts of college football games, which are very popular, there are a couple of advertisements that highlight the universities’ educational and research prowess. Usually these involve good-looking students with colorful liquids in test tubes or surrounding a professor in a lab coat at a computer terminal. But that’s not good enough for TCU, home to SDSS members Kat Barger and SDSS-IV Survey Coordinator Peter Frinchaboy. Their contribution to the Big 12 ad, on a broadcast seen by over 2 million people, features a shot of the Sloan Foundation telescope opening up for a night’s observing. TCU also has its own ad for these games, which focuses entirely on its involvement in the Sloan Digital Sky Survey, including more beautiful shots of the Sloan Foundation Telescope in New Mexico and a “starring” role for Peter. Take a look at http://www.big12makingadifference.com/university/tcu

* 10 universities are part of the Big 12. Don’t ask.

SDSS Collaboration Meetings in Park City, Utah, USA

Over 150 scientists from institutions in 13 countries in Europe, Asia, North America and South America recently traveled to Park City, Utah for the SDSS Collaboration meetings. First SDSS-IV got underway. The start of SDSS-IV observations on July 1, 2014 meant that this meeting was much less anticipatory and much more participatory than the SDSS-IV meeting last year. For the second half of the week, the SDSS-III collaboration, data all taken, was focused on the interesting science results coming out of this very successful 6-year survey. The overlap between the membership of the SDSS-IV and SDSS-III collaborations is quite large, so expect to see many of the faces in the photo from the SDSS-III half of the meeting in the future as well! Our enthusiastic thanks to the University of Utah for playing host to such a fabulous set of meetings.

SDSS-III collaboration meeting picture from the wonderful setting of Park City, Utah

SDSS-III collaboration meeting picture from the wonderful setting of Park City, Utah


The Sloan Digital Sky Survey Expands Its Reach

With the start of SDSS-IV this July, the Sloan Digital Sky Survey is entering a new and exciting phase of exploring the Universe. We’ve imaged 1/3 of the sky and taken over 3 million spectra, but we haven’t explored beyond the centers of nearby galaxies, haven’t mapped the Universe between 3 and 7 billion years after the Big Bang, and haven’t studied the part of the Milky Way that is only visible from the Southern Hemisphere. Well, that all changes starting now! We have a press release today featuring the science of SDSS-IV and including a fantastic video by John Parejko illustrating how SDSS takes all that data (hint: it starts with a lot of work in the daytime and continues with a lot of work in the nighttime).