Tag Archives: John Parejko

LSST: mining the sky in 4D

The Large Synoptic Survey Telescope (LSST) is going to be a unique astronomical instrument.

“Unlike a lot of other telescopes around the world, LSST is actually aptly named,” joked Dr. David Reiss of the University of Washington at a recent gathering of Astronomy on Tap Seattle at Peddler Brewing Company in Ballard. Reiss and Dr. John Parejko, two UW astronomers involved in the project, gave an overview of the telescope, which is under construction in Chile.

Parejko and Reiss

John Parejko (left) and David Reiss, research scientists at the University of Washington, discussed the Large Synoptic Survey Telescope at an Astronomy on Tap Seattle event October 28 at Peddler Brewing Company in Ballard. Photo: Greg Scheiderer.

As for the name, Parejko noted the scope will be truly large. It will have an 8.4-meter mirror, a 3.2-gigapixel camera, and will take an image of the night sky every 30 seconds.

“We’re going to generate 15 terabytes of data every single night,” Parejko noted. “That means by the end of the survey we’ll have 30 trillion database entries, and over half an exabyte of data and images being catalogued.”

“That’s a lot of data even for those of you who work at Amazon,” he quipped.

Synoptic is the word even the scientists say they have to look up every time. Essentially it means that the instrument will look at everything as a whole and provide a synopsis.

“Unlike a lot of other telescopes, the LSST has been designed to serve thousands of astronomers with interests ranging from supernovae or exploding stars, to planets and asterois, to the universe as a whole,” Reiss explained.

It’s a survey because LSST will not look at just one object.

“Not only is it covering all kids of different science, it’s actually covering the whole sky,” Parejko said. They hope to start observing in 2022, and the 10-year survey will photograph the entire sky every three nights. They expect to discover 37 billion stars and galaxies.

Lastly, it’s a telescope, but it’s much more.

“The main thing that LSST is going to produce is lots and lots of data,” Reiss said, “images and catalogs and databases of all of the objects in the sky that are going to be shared with everybody in real time.” With new information coming in constantly, they’ll be effectively creating a 10-year, multi-color, ultra high-resolution movie of the night sky.

The building

Parejko described the facility, which is being built on the Cerro Pachón ridge at 8,700 feet elevation, not far from town of La Serena in the mountain desert of Chile. It’s a good site for an observatory, with high elevation and low humidity. The building has been designed with a lab for working on the mirror and other parts of the telescope so that they don’t have to send things off the mountain for repairs.

“That means we minimize our down time; we can spend as much time as possible taking data,” Parejko said. You can watch progress of the construction on the LSST webcam.


An artists’ concept of the Large Synoptic Survey Telescope. Image: LSST.

The telescope itself will be short, squat, and compact, with the secondary mirror and camera located out at the end. They’re building it short to reduce wobble when it moves—another measure for minimizing down time. They were able to keep it short by using a different shape on the outside of the primary mirror than on the inside. Light will come into the scope, reflect off the outside of the primary to the secondary mirror, back down to the inside of the primary, which will beam it up to the camera.

“That’s how we can keep the telescope so short and compact, by folding the light like that,” Parejko explained.

The camera, about the size of a Smart Car, will have three lenses and space for five filters. The detector will feature 21 “rafts” each with nine CCDs. If one raft breaks, they’ll just pull it out, plug in another, and keep imaging.

The building will also include a major computer lab. That’s still under design.

LSST software

Reiss explained that, with so much data being collected, computing will be important. Essentially, they’re building, “sort of a Google index of the entire night sky over the course of ten years.” To do that, they’re creating a high-speed network to connect the telescope in Chile to a supercomputing center in Illinois. There, they’ll look for things that move or blow up, and expect to spot some 10 million events every night. Information about these discoveries will go out in nightly alerts to interested users.

“We’re basically providing the equivalent of astronomical Twitter, Google, and Amazon Web Services to the community,” Reiss said.

“We’re going to be sending out nearly 600 gigabytes worth of simply just these alerts every night,” he added. “If one of you were going to subscribe to these you’re going to max out your Comcast monthly allocation in one night.”

Researchers will be able to upload their software or algorithms into the LSST computing cluster and do calculations in the cloud, rather than having to download all of that data. Many institutions will receive the alerts and write algorithms that will help users pick and choose data. There will likely be smartphone apps that will allow users to, say, track their favorite asteroid, and people will be able to use the data to learn about the universe or do citizen science. Reiss noted that, by keeping a constant eye on the sky, we will be able to spot lots of the sorts of things that we only find today through the luck of looking in the right place at the right time.

LSST goals

The main science goals of the LSST are to learn about dark matter and dark energy, catalog the solar system, watch how things change, and learn about the structure and formation of the Milky Way.

Astronomy on Tap Seattle, November 2016The LSST team includes 39 institutional members, among them 21 colleges and universities. The UW is a founding member. The project employs 200 astronomers and engineers from 19 different countries. The total cost of getting LSST up and running by 2022 will be about $400 million. That sounds like a lot of money, but Reiss and Parejko pointed out, given the season, that it’s about what Americans spend on Halloween costumes for their pets in a typical year. Funding for the project has come from the National Science Foundation, the U.S. Department of Energy, and through fundraising by the nonprofit LSST Corporation.

Astronomy on Tap Seattle is organized by graduate students in astronomy at the University of Washington. The events are free, but you can help them cover the costs of creating them by donating online to the Friends of Astronomy Fund at the UW. The next event is scheduled for 7 p.m. Wednesday, November 16 at Peddler, and will be a Cosmos on Tap. Attendees will watch an episode of the original Carl Sagan series, and scientists will give updates on how the science has changed since the show first aired. As always, there will be trivia contests, and beer.


LIGO, LSST, AOT set for alphabet soup week

A talk by a founder of LIGO and a closer look at the LSST are the highlights of our astronomy calendar for the week.

Wave of the future

Rainer Weiss

Dr. Rainer Weiss. MIT photo: Bryce Vickmark.

Gravitational waves have been all the rave since they were first and finally detected last year. Dr. Rainer Weiss, one of the founders of the Laser Interferometer Gravitational-wave Observatory (LIGO) will give a lecture titled, “Gravitational Wave Astronomy: A New Way to Explore the Universe” on Tuesday, October 25 at 7:30 p.m. in room 130 of Kane Hall on the University of Washington campus in Seattle. Weiss began his work on gravitational waves with a classroom exercise in a general relativity course given at MIT way back in 1967. He will discuss the history of gravitational waves proposed by Einstein, go over the results of the LIGO project, and look into the future of gravitational wave astronomy.

All sign-ups for the free lecture have been taken, but you can watch a live stream of the talk on Tuesday. You can also sign up for the waiting list should seating become available. The talk is part of the Frontiers of Physics public lecture series from the UW College of Arts and Sciences.


AOT LSSTTwo University of Washington scientists involved in the Large Synoptic Survey Telescope (LSST) will talk about the project at a special Friday edition of Astronomy on Tap Seattle at 7 p.m. October 28 at Peddler Brewing Company in Ballard. Doctors John Parejko and David Reiss will explain the LSST, currently under construction in Chile and targeted for being fully operational by 2023. The LSST will image and catalogue tens of billions of galaxies and stars and find more than three million exploding stars and six million asteroids and comets over the next decade, effectively creating a 10-year, multi-color, ultra high-resolution movie of the night sky. It will collect an astounding 20 terabytes of data every night. Parejko and Reiss will talk about the LSST telescope and camera design, the software challenges associated with processing such a huge data set, and the science to be gained from mining the sky in 4-D.

Astronomy on Tap Seattle is organized by graduate students in astronomy at the UW, this month in concert with TEDxSeattle and the LSST. It’s free. It’s always a good idea to bring a chair, as the combination of beer and astronomy is tremendously popular!

Star parties and planetarium shows

The Island County Astronomical Society will hold a free public star party on the evening of Friday, October 28 at Fort Nugent Park in Oak Harbor.

The Spokane Astronomical Society will hold a special Halloween star party beginning at 5:30 p.m. Saturday, October 29 at the club’s dark-sky observing site near Fishtrap Lake on Miller Ranch Road East near Sprague.

Haunted Night SkyIt’s Spook-tober at the Pierce College Science Dome, and this Saturday, October 29 will be the last day for its kids’ planetarium show called “Haunted Night Sky.” Participants will be able to find creatures in the night sky, build a Frankenstein satellite, and take a tour of the Sea of Serpents on the Moon, the Witch’s Head Nebula, and other spooky places in the universe. Best for kids ages 3-12. Shows are scheduled for 12:30 p.m. and 2 p.m. Cost is $3.

Futures file

You can scout out future astronomy events on our calendar. New additions to the calendar this week include:

Up in the sky

Venus flirts with Saturn and Jupiter has an encounter with the Moon this week. The Sky This Week from Astronomy magazine and This Week’s Sky at a Glance from Sky & Telescope have more observing highlights for the week.


Learning about LIGO at Astronomy on Tap

The most recent gathering of Astronomy on Tap Seattle brought to town two scientists working in one of the most groundbreaking areas of astronomy: detection of gravitational waves.

Nature was kind to us

Jeff Kissel, a control systems engineer at the LIGO Hanford Observatory, talked about how exciting it was when they switched on advanced LIGO back in September 2015.

“Boom! Right out of the gate we saw this whopper of an event,” Kissel said, detecting gravitational waves from the merger of a pair of stellar-mass black holes. “Nature was very kind to us.”

What they spotted at Hanford and at LIGO in Livingston, Louisiana was a match.

“Inside our data, which is almost always noise, we saw this very characteristic wave form that was predicted by general relativity,” Kissel recalled. They found gravitational waves from a couple of other black-hole mergers in the following months.

“This is the beginning of gravitational wave astronomy,” Kissel said.

Gravitational waves oscillate through spacetime in a way
by this animation. Credit: ESA–C.Carreau

Kissel pointed out that LIGO only detects a small part of the gravitational wave spectrum. As with light, gravitational waves can come in a wide range of wavelengths with periods ranging from milliseconds to billions of years. Longer-length waves might come from the mergers of galactic nuclei, or even from quantum fluctuations from the early universe.

“There’s a whole zoo of things to find out there,” Kissel said. He anticipates more ground-based observatories as well as some space LIGOs that could have detector arms millions of kilometers long.

How LIGO works

LIGO sounds awfully complicated, but, broken down, the idea is pretty simple. Jenne Driggers
is a Caltech postdoctoral scholar stationed at the LIGO Hanford Observatory, where her gig is improving the sensitivity of the interferometers. Driggers explained that, essentially, they shoot a laser beam into a splitter that sends beams down two equal arms four kilometers long. The beams reflect from mirrors and return to be put back together.

A simplified look at how LIGO works. A laser beam is split and sent down two equal
arms four kilometers long, then reflected back by mirrors. When they return to be
recombined, they will usually cancel each other out and no light will get to the detector.
But if a gravitational wave distorts the system, the light will be spotted by the detector.
Credit: T. Pyle, Caltech/MIT/LIGO Lab

“When they recombine they can be exactly out of phase, and then there’s no laser light (at the detector),” Driggers said. “They cancel each other out totally. Or the lengths will change and these two electromagnetic waves can add up, and so we do get some light.”

When that happens it means that a gravitational wave has distorted the LIGO arms ever so slightly. They measure the light received at the detector to learn more about the wave.

In practice it’s a lot more complicated. It all happens in a total vacuum to avoid any distortion from air. The mirrors are suspended from a system of four pendulums, which helps to eliminate vibration. The mirrors are highly reflective pieces that each weigh around 100 pounds and cost half a million dollars. The laser is about the best there is.

“The laser wavelength itself is our ruler that we’re using to measure the distance between those two mirrors,” Driggers said, “and we need to be able to measure that distance to 10-19 meters.”

“This is one of the highest-power, frequency stable, power-stable lasers on the planet,” she added.

Driggers invited people to tour LIGO Hanford. Public tours are held twice each month, and groups of 15 or more can arrange for a private tour.

Up next: LSST

Astronomy on Tap Seattle is presented and organized by astronomy graduates students at the University of Washington. Their next event is planned for Friday, October 28 at Peddler Brewing Company in Ballard and will feature UW scientists Dr. John Parejko and Dr. David Reiss, who are working on the Large Synoptic Survey Telescope project. The events are free. Enjoy beer and astronomy!


BOSS and Pleiades figure out the universe

Astronomy these days is something of a tag-team event involving both observers and theorists. We got a look at how it works at the most recent Astronomy on Tap Seattle event at Bad Jimmy’s Brewing Company in Ballard.

Case in point: for a couple of decades cosmologists had been using the cold dark matter theory to explain how the universe evolved from a hot, dense, uniform place right after the Big Bang to the web of galaxies that we see today. The theory worked pretty well, but there were a couple of catches: it predicted that dwarf galaxies would have large central bulges of stars and increasingly dense dark matter at their cores. Neither prediction matched with the observations.

Figuring it out


Look! Up in the sky! Prof. Fabio Governato makes a point during his Astronomy on Tap talk Feb. 17 at Bad Jimmy’s. Photo: Greg Scheiderer.

Dr. Fabio Governato, a research professor in the Department of Astronomy at the University of Washington, said he and a few colleagues, after downing several beers each during an escape from a boring conference, decided to figure out this anomaly. Governato‘s talk at Astronomy on Tap Seattle was titled, “Dark Matter, Black Holes, and other reasons to work with NASA’s fastest supercomputer: Pleiades.”

Eventually, they hit upon the idea that supernova explosions in the dwarf galaxies might push away gas and thus retard star formation, and may also blow dark matter away as well.

“This is very simple physics,” Governato said, “but the problem was to find a numerical experiment that you could run with computers that shows clearly” how it works. They used millions of hours on supercomputers, like NASA’s Pleiades, adding the supernovae into the mix and tweaking the idea until the computer simulation of the cold dark matter theory turned out dwarf galaxies that matched what we actually observe. Their paper about the work was published in the journal Nature, and Governato has some humorous tales about the twists and turns between the work, the publication, and ultimate acceptance of the findings.

His talk also used interesting and sometimes humorous animations to make points. Governato’s movie of a dwarf galaxy formation based on the work is posted below.



Dr. John Parejko, holding a sample of the metal plates used in the BOSS survey, answers questions after his talk. Even pooches love Astronomy on Tap! Photo: Greg Scheiderer.

Dr. John Parejko works on the observation side of the equation. Parejko recently was with the Sloan Digital Sky Survey out of New Mexico. His talk was titled, “Detect the Ancient Universe Like a BOSS.”

“BOSS is measuring distances to millions of galaxies to find wiggles from the early universe, but that doesn’t make a very good acronym,” Parejko quipped. BOSS actually stands for Baryon Oscillation Spectroscopic Survey.

The wiggles or oscillations are evidence of interactions that happened right after the Big Bang.

“Patterns in that hot, dense plasma persist to today in the distribution of galaxies in the universe,” Parejko said.

“These are not gravitational waves,” he noted, as the discoveries from LIGO were fresh in the news. “These are actually the interaction between the dark matter and the baryons very early in the universe.”

The process was simple enough, as they took spectra of galaxies and computed their redshifts to precisely determine distances. The challenge was that they had to look at a lot of galaxies, and over the years BOSS examined about a third of the sky and took images of about two million galaxies, measuring the redshifts of about half of those. Using the redshift to pin down distances to and between galaxies, and examining the patterns that emerge, helps astronomers figure out galaxy formation and learn how dark energy is causing the expansion of the universe to speed up.

Part of the tool that BOSS uses is made at the University of Washington, where telescope plates are created for the project. Each metal plate, about three feet wide, has a thousand holes drilled into it, each one corresponding to a specific object in the sky. Humans plug a fiberoptic cable into each hole by hand, and the cable collects the light from targeted galaxies.

Birthday party!

Astronomy on Tap Seattle is organized by astronomy graduate students at the University of Washington. The next event, scheduled for March 23, will celebrate the first birthday of the program. Speakers will update the subjects of their talks from the first year. Attendees will be able to purchase a commemorative AoT beer glass and sample Bad Jimmy’s barrel-aged Big Sipper, a Scotch ale named as a salute to Astronomy on Tap.


Busy Presidents Day week ahead

Happy Presidents Day from Seattle Astronomy. We celebrate the birthdays of George Washington and Abraham Lincoln this week. Perhaps, though, we should observe Astronomers Day, because some big-name birthdays fall this week as well. Nicholas Copernicus was born Feb. 19, 1473—he would be 543—and Galileo was born Feb. 15, 1564—452 years ago this day. Maybe it is because of these two most important scientists that there are so many great astronomy events on the calendar this week!

Show me a rose

Rose City AstronomersWe’re planning a road trip to Portland, where the Rose City Astronomers will hold their monthly meeting at 7:30 p.m. Monday, Feb. 15 at the OMSI auditorium. Dr. Gregory Bothun of the University of Oregon will give a talk titled, “Astronomy, Big Data, and the Future.” The premise: we’re collecting astronomical data at an astronomically increasing pace, but human processing and thinking about all of this information can’t keep up. Is astronomy in danger of becoming a “pixel archive science?”

Silent Sky and These Things Abide

Silent SkyTaproot Theatre in Greenwood continues its run of Silent Sky, Lauren Gunderson‘s play about astronomer Henrietta Leavitt, through Feb. 27. This Tuesday, Feb. 16 at 7:30 p.m. the theatre will host a special conversation with the play’s director, Karen Lund, and Adrian Wyard of the Counterbalance Foundation as they discuss the search for truth by both science and religion, the history of the conversation between faith and science, and the possibilities for future dialogue. It’s free, but seating is limited, so contact the theatre if you wish to attend.

Watch for a post about our conversation with Wyard coming soon!

Decisions, decisions

There are two good events coming up on Wednesday, Feb. 17, but alas, you can only be in one place at a time, unless this whole multiverse thing is true.

AOT SeattleThe fine folks from Astronomy on Tap Seattle, organized by astronomy graduate students from the University of Washington, will host their monthly confab of astronomy, trivia, prizes, and beer at 7 p.m. at Bad Jimmy’s Brewing Company in Ballard. This month UW astronomer Dr. John Parejko will give a talk titled, “Detect the Ancient Universe Like a BOSS,” and Dr. Fabio Governato will speak about “Dark Matter, Black Holes and other reasons to work with NASA’s fastest supercomputer: Pleiades.” It’s free, but bring beer money.

Meanwhile the Seattle Astronomical Society will hold its monthly meeting at 7:30 p.m. Wednesday in room A102 of the Physics/Astronomy Building on the UW campus in Seattle. Astronomy Ph.D. student Phoebe Upton Sanderbeck will give a presentation about how measuring the temperature of the universe can help us understand its development.

Saturn’s moons of promise

Pacific PlanetariumPacific Planetarium in Bremerton will feature its monthly third Friday astronomy talk this Friday, Feb. 19 with hourly presentations at 5 p.m., 6 p.m., and 7 p.m. NASA Solar System Ambassador Ron Hobbs will share the latest findings about the environments on Saturn’s moons Enceledus and Titan, where liquid water and methane flow, which might provide the necessary conditions for life to develop. Tickets are $5 and are available at the door or in advance online.

The Mercury 13

Mercury 13Sally Ride became the first American woman in space when she flew on a space shuttle mission in 1983. More than two decades earlier 13 U.S. women were training for flight in the Woman in Space program. Of course, the Mercury 13 never got off the ground. At 2 p.m. this Saturday, Feb. 20 at the Museum of Flight aviation expert Philip Tartalone will explore the genesis of the Woman in Space Program, the personalities involved, the testing, and the social mores of the early 1960s that ultimately doomed the program. The presentation is free with admission to the Museum.

Up in the sky

Jupiter will be at opposition next month, but it’s already placed pretty well for viewing in the late evening these days. The Sky This Week from Astronomy magazine and This Week’s Sky at a Glance from Sky & Telescope have other observing highlights for the week.