The Hunt for Jellyfish Galaxies in the Frontier Fields

Jellyfish galaxies, exotic galaxies with “tentacles” made of stars and gas, appear as though they are swimming through space. So far, astronomers studying the Frontier Fields have found several of these strange galaxies, and they are currently combing through the mountains of data to find even more.

Sometimes also known as “parachute galaxies” or “comet galaxies,” jellyfish galaxies form when spiral galaxies collide with galaxy clusters. When the cold gas from an approaching spiral hits the hot gas from a galaxy cluster, the stars continue on, but the collision blasts the cold gas out of the galaxy in trailing tails, or “tentacles.” Bursts of stars form in these streamers, sparked by the shock of cold gas hitting hot gas. The tentacles, with their knots of newborn stars, trace the path of the colliding, compressed gas. Eventually, these jellyfish galaxies are thought to settle into elliptical galaxies.

Three examples of jellyfish galaxies in the Frontier Fields. In each image, the telltale, trailing “tentacles” of stars and gas are present. The left and right galaxies are from galaxy cluster Abell 2744. The middle galaxy resides in galaxy cluster Abell S1063.

Some examples of jellyfish galaxies in the Frontier Fields. In each image, note the telltale, trailing “tentacles” of stars and gas. The left and right galaxies are from galaxy cluster Abell 2744. The middle galaxy resides in galaxy cluster Abell S1063.

Jellyfish galaxies are sometimes also seen in less massive groups of galaxies. Their characteristic shape is, however, usually much more pronounced for spirals falling into massive galaxy clusters, because the gas they encounter there is denser, and because they move faster due to the stronger gravitational pull of the cluster. The higher speed results in a more energetic collision that, in turn, increases the pressure that strips the infalling galaxy of its cold gas and triggers widespread star formation.

Astronomers have studied similar interactions in detail in nearby galaxy clusters but do not fully understand the much more violent process that creates jellyfish galaxies in very massive clusters. If the cold galactic gas is stripped very quickly these collisions could be the primary way by which spiral galaxies are transformed into ellipticals. Unfortunately, because the phenomenon is over so quickly, it is very difficult to observe. One expert on jellyfish galaxies—Dr. Harald Ebeling of the Institute for Astronomy at the University of Hawaii—explains that this is why astronomers are looking at extremely massive clusters, such as those in the Frontier Fields, in their search for a large sample of these galaxies.

Aside from helping to explain why elliptical galaxies are so common in the universe, jellyfish galaxies capture the process of galaxy/gas collisions in action. Their trailing, star-forming tentacles may also explain the presence of “orphan” stars that do not belong to any galaxy.

The work to uncover the secrets of the Frontier Fields goes on. Stay tuned for more exciting news on jellyfish galaxies and other oddities as scientists continue to study the vast amount of data collected in the Frontier Fields.

Spotlight on Gabriel Barnes Brammer, ESA/AURA Astronomer

This occasional series focuses on members of the Frontier Fields team. It highlights the individuals, their jobs, and the paths they took to get to where they are today.

Portrait of Gabriel Brammer

Astronomer Gabriel Brammer answers questions about his role on the Frontier Fields program and the path he took to get there.

What does a typical day on the job entail? What are your responsibilities?

A typical day involves a lot of communication: e-mail and teleconferencing with scientific collaborators around the U.S. and around the world, assisting observers with preparing their Hubble observations, and conversations and meetings with fellow members of the Hubble Wide Field Camera 3 instrument team. My research focuses on the formation and evolution of distant galaxies, often using Hubble observations. I have a position that allows me to pursue my own independent research interests along with my responsibilities supporting Hubble operations, and I appreciate that the goals of both of these aspects of my work are closely aligned.

 What specifically is your educational background?

I obtained a bachelor’s degree in astronomy from Williams College in Williamstown, Massachusetts, and a Ph.D. in astronomy from Yale University in New Haven, Connecticut.

 How did you first become interested in space?

My favorite subjects in school were always math and science, particularly physics when I was a bit older. Reading Carl Sagan’s “Cosmos” in high school always sticks with me as being a defining moment in inspiring my interest in space science and astronomy. Sagan presents such a clear connection between the beauty of the subject and the rigorous science that underlies it; I’ve seen from other profiles of my colleagues similar to this one that I’m far from alone in finding inspiration there!

Was there someone (parent, teacher, spouse, sibling, etc.) or something (book, TV show, lecture, etc.) that influenced you in developing a love for what you do, or the program you’re a part of?

The pursuit of an advanced degree in astronomy, or any field, is a very long chain that stretches over 20 years of a student’s life, obviously including a dramatic evolution in his or her own personal development and maturity. From day one I’m grateful for the tireless love, support, and encouragement from my parents and family, and I have had many excellent teachers, mentors, and role models at all stages of my education and career. Each of them represents a strong link in that chain, and without any one of them individually, the path I would have taken would likely have been very different from the one I am happy and honored to be on today.

Was there a particular event (e.g., lunar landing, first Shuttle flight, etc.) that particularly captured your imagination and led to life changes?

 The bright appearance of Comet Hale-Bopp in the winter of 1997, my junior year of high school, was a formative event for me at an opportune moment. Seeing the bright comet, a transient visitor from the outer solar system, just hanging over the horizon captivated me. As often as I could, I would drag the small telescope my dad had recently bought, along with as many friends I could muster, out to the cold, dark skies of central Iowa to see it.

Later in the summer of ’97, I went to New England to tour potential colleges, where, during a short visit to Williams College, I met Professor Jay M. Pasachoff and his students who were preparing an expedition to observe the solar eclipse in Aruba the following year. That brief encounter, along with the recent experience observing Hale-Bopp, showed me that studying astronomy would offer an ideal combination of research in the physical sciences and travel to exotic locales to observe both aesthetically and scientifically magnificent phenomena. I was privileged to later study and research with Professor Pasachoff myself, including an unforgettable expedition to observe the solar eclipse in Lusaka, Zambia, in 2001.

Gabe checks out the telescope for observations of the June 21, 2001, total solar eclipse from Lusaka, Zambia, as part of the Williams College Eclipse Expedition. Credit: J. Pasachoff.

Gabe checks out the telescope for observations of the June 21, 2001, total solar eclipse from Lusaka, Zambia, as part of the Williams College Eclipse Expedition. Credit: J. Pasachoff.

How did you first get started in the space business?

My first experience visiting and working at a professional astronomical observatory was with the National Science Foundation’s Research Experiences for Undergraduates program at the Cerro Tololo Inter-American Observatory in 2001. I must say I was pretty miserably exhausted my first night observing up on the mountain top, ready to adjust my career plans at 4 a.m., with the local radio reminding us between cumbia (dance music) hits of the glacial progress of time — “son las cuatro con cinco minutes … son las cuatro con diez minutos.” I suppose the second night was a bit better, and by the third night I was hooked.

I’ve been working at observatories ever since, now having spent something like 270 nights observing the skies from mountain tops in Arizona (Kitt Peak) and Chile (Cerros Tololo, Las Campanas, and Paranal) to valleys in Japan (Nobeyama). Going outside at night at one of these observatories and seeing the eyes of giant telescopes staring up at the sky, gathering in photons from distant objects, is an extraordinary experience. I’m happy to now have a more normal sleep schedule at the Space Telescope Science Institute, but I appreciate still being close to the day-to-day operations of Hubble as an observatory and working on the front lines as photons from distant stars and galaxies hit the detectors.

A composite image of sunset and midnight at the Very Large Telescope at Cerro Paranal, Chile.

A composite image of sunset and midnight at the Very Large Telescope at Cerro Paranal, Chile. Each of the four domes houses a telescope with a primary mirror 8.2 meters (26.9 feet) in diameter. Credit: Gabriel Brammer.

What do you think of the Hubble results, or the impact that Hubble has on society? 

Even classmates in my kids’ pre-kindergarten classes know Hubble when they see it! Hubble has something for everybody, from atmospheres of extra-solar planets to the most distant galaxies, and therefore has had an immeasurable impact on society’s scientific imagination and curiosity.

Is there a particular image or result that fascinates you?

To me the Hubble Ultra-Deep Field /eXtreme Deep Field (HUDF/XDF) represents all of the past success of Hubble and points to the future potential of Hubble and its successors like the James Webb Space Telescope in a single image. Now including near-infrared observations by the Wide Field Camera 3, installed in 2009, the HUDF/XDF shows us galaxies across some 95 percent of cosmic history, from the first star-bursting seeds of galaxies to the assembly of more massive, more regular structures of galaxies more like those we see today. The Frontier Fields represent the most recent exciting extension of the legacy begun with the Hubble Deep and Ultra-Deep Fields.

The eXtreme Deep Field, or XDF.

The eXtreme Deep Field, or XDF, was assembled by combining 10 years of NASA Hubble Space Telescope photographs taken of a patch of sky at the center of the original Hubble Ultra Deep Field. The XDF is a small fraction of the angular diameter of the full Moon. Credit: NASA, ESA, G. Illingworth, D. Magee, and P. Oesch (University of California, Santa Cruz), R. Bouwens (Leiden University), and the HUDF09 Team.

 I also love browsing through Hubble’s spectacular high-resolution images of nearby galaxies. In the deep fields, we generally infer properties of galaxies based on small, barely resolved images of their structures, while images of local galaxies such as the mosaic of M82 show many of the myriad processes that form and shape galaxies in exquisite detail. It is through the combination of these resolved nearby studies and distant surveys that Hubble has made such a large contribution in our understanding of how galaxies form and evolve.

Mosaic image from Hubble of the magnificent starburst galaxy Messier 82 (M82).

This mosaic image from Hubble of the magnificent starburst galaxy Messier 82 (M82) is the sharpest wide-angle view ever obtained of this galaxy. M82 is remarkable for its bright blue disk, webs of shredded clouds, and fiery-looking plumes of glowing hydrogen blasting out of its central regions. Credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA). Acknowledgment: J. Gallagher (University of Wisconsin), M. Mountain (STScI), and P. Puxley (National Science Foundation)

Are there specific parts of the program that you’re proud to have contributed to?

I am happy to have helped make the Frontier Fields observations as deep and as efficient as possible to maximize the scientific return from extremely valuable observing time on Hubble. With only a relatively minor change to the observing strategy, taking extra care to avoid extra glare from bright foreground light from the Earth, we enabled the Frontier Fields to see ever fainter and more distant galaxies than otherwise would have been possible.

Photo taken by Gabe of Comet Lovejoy (C/2011 W3) and the European Southern Observatory’s Very Large Telescope at Cerro Paranal, Chile (December 22, 2011). Credit: Gabriel Brammer.

Photo taken by Gabe of Comet Lovejoy (C/2011 W3) and the European Southern Observatory’s Very Large Telescope at Cerro Paranal, Chile (December 22, 2011). Credit: Gabriel Brammer.

 

Also see “Spotlight on Jennifer Mack, Research and Instrument Scientist,”
 Spotlight on Dan Coe, ESA/AURA Astronomer,” and Spotlight on Tricia Royle, Senior Program Coordinator.”

Spotlight on Tricia Royle, Senior Program Coordinator

This occasional series focuses on members of the Frontier Fields team.  It highlights the individuals, their jobs, and the paths they took to get to where they are today.

Portrait of Tricia Royle

Tricia Royle, senior program coordinator, answers questions about her role on the Frontier Fields program and the path she took to get there.

What does a typical day on the job entail? What are your responsibilities?

When astronomers are granted time on Hubble, their program is assigned to a program coordinator to make sure the observations are feasible and schedulable on the telescope. When problems occur any time between acceptance and execution, it’s the program coordinator who helps get problems resolved. We act as liaisons between the various groups at the Space Telescope Science Institute (STScI) — science, operations, scheduling — and the observers — principal investigators and co-investigators. I tend toward the large-scale and long-term observations like Frontier Fields.

What specifically is your educational background?

I have a BSc in physics and astronomy from York University in Toronto, Ontario, Canada, and I have taken postgraduate courses in applied physics from Johns Hopkins University in Baltimore, Maryland.

What particularly interested you in school or growing up?  What were your favorite subjects?

I wasn’t particularly good at school in the early years and didn’t like the monotony of memorizing multiplication tables or writing out spelling words. In grade six, when the curriculum started to get interesting and turn more logic-based, I started to pay attention and actually enjoyed just about every class — except history, which still had too much memory work. In high school, it became clear that math and science were my favorites, though I still took a lot of English and arts courses because I enjoyed the creativity involved.

Tricia Royle poses with an astronaut at Kennedy Space Center.

Nineteen-year-old Tricia on her fifth or sixth trip to Kennedy Space Center in Florida. Tricia recalls, “It was pretty much the first place I asked to go every time I’d go to Florida. Eventually, my family just accepted it as higher priority than Disney World.”

How did you first become interested in space?

Growing up in a very rural area about an hour outside of Toronto, surrounded by farms and no streetlights, I had always been able to see the Milky Way, but I didn’t know much about what I was seeing. When I first read that our sun was a star and figured out that meant every star I was seeing was potentially someone else’s “sun,” it was pretty humbling. I wasn’t very old and I’m pretty sure I annoyed a lot of aunts and uncles with my new-found “discovery” that our sun is actually a star. I didn’t understand how they could talk about anything else if they knew how many suns there were in the sky! Weather and gas prices just didn’t seem important enough to warrant discussion when compared to my new sun/star revelation.

Was there someone or something that influenced you in developing a love for what you do, or the program you’re a part of? Was there a particular event that especially captured your imagination and led to life changes?

A lot of things happened when I was in my pre-teens and teenage years to push me toward space. I remember feeling intense sadness and disbelief after the Challenger disaster. I was in middle school, just starting to enjoy learning, and had a hard time dealing with the idea that a teacher who was supposed to go into space, then come back to share her experience with her classroom and other classrooms, now wasn’t coming back at all. I hadn’t realized before then how dangerous it was to launch a shuttle and couldn’t see past the loss of those seven astronauts to understand why anyone would take that risk.

A year or so later, Star Trek: The Next Generation came on TV, and it all started to make sense. I loved the scientific language and ideas in the show and the notion of “going where no one had gone before.” Traveling around on the Enterprise seemed like a dream come true, and I started to understand why someone would put everything at risk to go into space. Star Trek: The Next Generation was my first exposure to positive science fiction — not just doomsday aliens and robots — and it introduced me to the concept of just how much more might be out there and what might be possible. Hubble launched a few years after that, when I was in high school, and started sending back incredible images of real things that were actually out there, waiting to be found. It seemed to me that maybe a bit of the show was coming to life and I wanted to know more.

When it came time to choose a topic for my first high school term paper — it happened to be advanced chemistry — I decided it was a good excuse to find out more about all those suns/stars I had seen in the sky as a child, on Star Trek for the past four or five seasons and now coming down from Hubble. This seemed like a really good idea until my 10-page report was closer to 30 pages, and I still had several books to go through. Thankfully, I had a wonderful chemistry teacher who encouraged me to delve as deep as I wanted into the topic, but to choose something specific to keep the final paper under 15 pages so she could finish reading it in an evening. I chose to focus on the life cycle of stars, and that was the beginning of my intense curiosity about the science of space and the universe.

Tricia Royle posing at the sign at the entrance to Kennedy Space Center.

On a later trip, 21-year-old Tricia poses at the entrance to Kennedy Space Center.

How did you first get started in the space business?

The summer after my third year at York University, I worked with Dr. John Caldwell analyzing Hubble data on the low-mass stellar companions of larger stars. During that summer, he visited STScI and Johns Hopkins University to attend a conference and meet with his collaborators. I was invited to tag along. I imagine I looked a little — or a lot — lost and awkward standing among seasoned Hubble scientists and STScI employees in the auditorium after a talk. Fortunately, one of the Hubble data analysts took pity on me and invited me into her conversation. Lisa Frattare — now part of Hubble Heritage — became an instant friend and would later encourage me to apply to work at STScI after graduation.

I didn’t take her seriously, thinking there was no way a fresh-out-of-school job could be with something as huge as Hubble. But on a dare with one of my college roommates, we both applied for our unattainable dream jobs — I applied to STScI and he applied for a coaching job at the University of Hawaii. As luck would have it, I got an interview and came to work at STScI shortly after graduation as a program coordinator. Sadly, my roommate did not make it out to Hawaii.

Before I left York University, Dr. Caldwell described my new position at STScI as “the hot seat of astronomy,” which ended up being an understatement. Immediately after I started, I was working with and attending conferences with scientists I’d seen listed in textbooks. In my first two years, I had the opportunity to work with the Director of STScI — Robert Williams — and many others on the Hubble Deep Field to push the science limits of the telescope, and to join Lisa Frattare and Keith Noll on the Hubble Heritage Project to help make beautiful images from Hubble’s scientific data. I worked with Hubble Heritage for five years and still think it is one of those really great initiatives that highlights for everyone, not just scientists, what Hubble can do. All in all, not a bad start to a career in space.

What do you think of the Hubble results, or the impact that Hubble has on society? 

 I think people have started to take for granted the amazing images Hubble continues to allow scientists to take. It’s been up there for almost 26 years, which means there are a lot of kids and even adults who don’t know what it’s like to NOT have these observations sent down on a regular basis, or what it was like before Hubble helped solve some of the fundamental questions about the expansion of the universe and what is out there. I have two school-aged kids who just assume that Hubble has or will answer any question they may have about stars or galaxies. I don’t think it occurs to them that Hubble hasn’t always been and won’t always be around to do that.

The fact that it is such an ingrained part of the scientific and academic community says just how successful it has become. It’s like the Internet – it’s hard to remember what it was like before we had this way to find answers to our questions. I suspect Hubble’s archives and legacy programs will continue to provide answers, or trigger new questions, for a long time yet.

Is there a particular image or result that fascinates you?

The Ultra Deep Field, or UDF. I found out I was pregnant with my first child just after I started working as program coordinator for the UDF, and the UDF images were released while I was still in the hospital after delivering my daughter — so I will forever tie those two events together. But more than that, I still use the UDF image in my presentations, even though it is almost 12 years old, because it fascinates everyone who learns what they are really looking at. I ask people to look at that image and realize that what they are seeing aren’t individual stars, but galaxies. Then I ask them to keep in mind that this particular piece of sky was chosen because it was “boring,” and to further consider that everything they are seeing is contained within a patch of sky the size of the president’s eye on a dime, held at arm’s length. More than a few jaws drop at the implication. Seeing the UDF image triggers that realization in people, especially kids, of just how vast the universe must be easily makes the UDF my favorite.

Are there specific parts of the program that you’re especially proud to have contributed to?

I like the view from where I sit in Operations. I like watching a Hubble program develop from the initial science outline in the Phase 1, to a workable Phase 2, to a successfully executed set of observations. I especially love the large and multi-cycle programs — 47 Tuc, Hubble Deep Field, Ultra Deep Field, Andromeda, CANDELS, and now Frontier Fields. They allow me to work with people who have such a passion for what they do on these in-depth programs and challenge me to find new ways to get them the science they need.

Because repeat observers are assigned, when possible, to the same program coordinator each time they observe, that working relationship has a chance to grow cycle after cycle. Program coordinators tend to get very attached to the scientists they work with multiple times. I’ve been here since Cycle 6 and now we’re ramping up for Cycle 24, so the list of observers I claim as mine is pretty long, and I feel very protective of them and their observations, even if they’ve moved on to other program coordinators or even other telescopes.

What outside interests could you share that would help others understand you better?

A lot of what we do on Hubble can feel abstract and intangible, since we can’t actually go to the telescope or out in space to touch what we observe — so I like to do things that produce more tangible, immediate results. In addition to my love of reading and watching sci-fi TV shows, I do a lot of crafts to create something I can hold in my hand.

With most of my observers scattered around the country and internationally, I rarely see them in person. Giving talks about Hubble to schools and the more general public lets me connect the science to people. Being able to explain a Hubble image to someone without a science background and make it real for them, helps put into perspective that what I do at work on a daily basis can be inspiring and has results beyond the image itself. I want what we do at STScI and on Hubble to show people they can dream as big as they like because the universe is big enough to handle it.

Is there anything else that you think is important for readers to know about you?

I was one of only four female physics and astronomy majors in my first year at York University. Before classes even started, my academic advisor suggested that I might want to choose something easier than physics and astronomy, despite coming in with an A+ average in high school and scoring in the top 5 percent on the math assessment. Male classmates with B averages were not given the same suggestion to find an easier major.

In the years ahead, every test grade of mine that fell below an A – there weren’t many – brought up the question from others, and myself, as to whether I really should be there, whether I was good enough. It was a constant fight to prove to classmates, professors and myself that I deserved to major in physics and astronomy. It wasn’t enough that I wanted to be there and was passing my courses – I had to excel. Four of us started, but I was the only female graduate in physics and astronomy in my year.

I have a daughter and a son, still relatively young, but they’re starting to look at what they want to do when they finish school. Obviously I want them to do well, but my wish for both of them, and anyone else looking at what to do in their life, is that in whatever field they choose, they know that wanting to be there is enough and they don’t have to prove to anyone they deserve to follow their dreams.

 

Also see “Spotlight on Jennifer Mack, Research and Instrument Scientist
and “
Spotlight on Dan Coe, ESA/AURA Astronomer

Spotlight on Dan Coe, ESA/AURA Astronomer

This occasional series focuses on members of the Frontier Fields team.  It highlights the individuals, their jobs, and the paths they took to get to where they are today.

Dan Coe, ESA/AURA Astronomer, in front of the first Frontier Fields image, Abell 2744.

Dan Coe, ESA/AURA Astronomer, in front of the first Frontier Fields image, Abell 2744.

What is your position? What are your responsibilities?

I am an ESA/AURA astronomer at the Space Telescope Science Institute (STScI) in Baltimore. I use gravitational lensing to search for distant galaxies in Hubble and Spitzer Space Telescope images. I am the gravitational lens model coordinator for the Frontier Fields program. I also work to support astronomers’ use of Hubble’s Advanced Camera for Surveys and the Near-Infrared Camera on the upcoming James Webb Space Telescope.

How did you get involved with the Frontier Fields program?

In 2012, working on the Cluster Lensing And Supernova survey with Hubble (CLASH), I discovered a candidate for the most distant galaxy yet known, MACS0647-JD. Its light took about 13.4 billion years to get here, so we see it as it was long ago. We are looking 97 percent of the way back to the Big Bang. Back then, galaxies were much smaller, just 1 percent the size of our Milky Way, and had yet to form grand spiral structures.

MACS0647-JD is more distant than any of the galaxies discovered in the Hubble Ultra Deep Field (UDF), even though Hubble stared at the UDF for much longer: a week vs. four hours for the infrared images. This demonstrates the power of gravitational lensing. Galaxy clusters enable us to see fainter light from galaxies in the distant universe.

Gravitational lensing had been used often by astronomers, but its power had yet to be fully exploited. No one had taken ultra-deep images of a galaxy cluster with Hubble or Spitzer. I advocated for this to a committee convened by former STScI Director Matt Mountain. And now it has become a reality in the Frontier Fields program led by Jennifer Lotz. The ultra-deep images of galaxy clusters are revealing the faintest galaxies ever studied, magnified by gravitational lensing.

How do astronomers study gravitationally lensed galaxies?

The distant galaxies in these images are most typically magnified by factors of between 2 and 10. To properly study these galaxies, we need estimates of their magnifications from gravitational lens modeling. By studying the observed deflections and distortions of background galaxies, astronomers build up a model of each galaxy cluster’s mass distribution (primarily dark matter) and the resulting lensing magnifications.

For the Frontier Fields, five groups of astronomers from around the world collaborated to gather the best possible data on all six clusters and produce gravitational lensing models. I coordinated these efforts and processed their model submissions for all astronomers to use. This lens modeling work is unprecedented both for its collaborative nature and the accessibility that all astronomers now have to the magnification estimates. With deep Frontier Fields imaging now in hand, astronomers are able to study the lensing in much more detail and are producing the best dark matter maps and lensing models ever.

Are there specific parts of the program that you’re proud to have contributed to?

I helped Jennifer Lotz select the six Frontier Fields clusters—with a lot of input from other astronomers. I had hoped my babies would do well! So far they have, and I am proud.

Left: Frontier Fields Hubble image of Pandora's Cluster, Abell 2744. Right: Lensing magnifications (color) and distortions (swirls) of distant galaxies according to one model produced by Johan Richard and the

Left: Frontier Fields Hubble image of Pandora’s Cluster, Abell 2744. Right: Lensing magnifications (color) and distortions (swirls) of distant galaxies according to one model produced by Johan Richard and the “CATS” (Clusters As Telescopes) team.

How did you first become interested in space?

Mom was a space geek, as she tells it. She can still name the Mercury Seven [NASA’s first astronaut class]. She drew celestial bodies on the ceiling above my crib and hung a poster of Van Gogh’s “Starry Night” on my wall. She sat me on her lap to watch Carl Sagan’s “Cosmos” and to read the companion book. She took me outside to enjoy eclipses and meteor showers. And she held me in her arms and cried on my head as we watched the first Shuttle launch. I remember always being awestruck by the immensity of the universe. And I knew I wanted to work on everything.

This picture of Dan and his mom was taken when the future astronomer was just 5 months old.

This picture of Dan and his mom was taken when the future astronomer was just 5 months old.

What specifically is your educational background?

I went to Browne Academy elementary school, Thomas Jefferson High School for Science and Technology, Cornell University for my B.S. in Applied & Engineering Physics—with a concentration in astrophysics—and Johns Hopkins University, right across the street from STScI, for my Ph.D. in astronomy.

What particularly interested you in school or growing up? What were your favorite subjects?

Growing up, I loved math, puzzles, games, and eventually computer programming. The latter proved especially useful for my career since we write many programs to analyze our Hubble images and other data.

“What about poetry?” Mom would ask. She and my father had studied art, literature, and history. As a smart-aleck kid, I insisted all of that could be explained by mathematics. But as I grew up, I grew to appreciate the poetry in Carl Sagan’s explanations of our universe. I became more curious about all of the physical and personal forces that brought us to where we are and take us where we are going. And all of this, in time to meet my partner Kate Welch, a Shakespeare scholar, who gives me a deeper appreciation for both poetry and history. Turns out I should have listened to my mother all along!

How did you first get started in the space business?

I followed Carl Sagan to Cornell, but unfortunately I never got to meet him. He was too sick to teach my freshman year. During my senior year, astronomers announced new supernova results suggesting the existence of dark energy. Carl Sagan had taught us we are all made of star stuff. But then we learned that the universe is mostly made of something very different: dark matter and dark energy. Astronomy had humbled humanity yet again. I think I always planned to go to grad school for astronomy, but those exciting results really sealed it for me.

Once in grad school at Johns Hopkins, my advisor Narciso Benitez started me working on mapping dark matter in galaxy clusters by modeling gravitational lensing, and measuring distances to galaxies in new Hubble ACS images, including the UDF. He was a constant source of inspiration as I tackled tough analysis problems. I followed him to Granada, Spain, where I finished my Johns Hopkins Ph.D.

After three years at NASA’s Jet Propulsion Laboratory and Caltech in Pasadena, I am now back in Baltimore at STScI. My colleagues and I here are fortunate to work with Adam Riess, one of the Nobel Prize winners from that inspiring dark energy discovery in 1998.

What do you think of the Hubble results, or the impact that Hubble has on society?

I am proud to be contributing a small part to Hubble’s great legacy. In addition to my Frontier Fields work, I am leading a large new Hubble program called RELICS to observe 41 more lensing galaxy clusters. Complementary to the Frontier Fields, RELICS is casting a broader net with shallower imaging. Our goal is to find the best and brightest distant galaxy candidates for more detailed study with current telescopes and with the James Webb Space Telescope.

Hubble has filled us with wonder and taken us back in time, almost all the way back to the Big Bang. By flipping through Hubble’s scrapbook, we can relive 97 percent of the history of the universe. James Webb will tell the tale of our cosmic origins in the first galaxies.

I can’t say I really comprehend the immensity of the universe any more than I did as a child. But I have appreciated new details, and I remain awestruck. The universe teaches us to be humble yet proud, and most of all, I think, grateful. Humble, as an insignificant speck in the vast cosmos. Proud that we have come so far and can begin to comprehend it. And grateful that we have the privilege to witness and explore so much of it.

Is there a particular image or result that fascinates you?

We named one of our cats after the Carina Nebula. The Hubble + CTIO Blanco color image of this stellar nursery is a masterpiece—the most beautiful astronomy image I’ve seen. Our other cat is named Maggie, after Queen Margaret in Shakespeare’s Henry VI; she has a “tiger’s hide.”

Dan calls picture of the Carina Nebula

Dan calls this picture of the Carina Nebula “the most beautiful astronomy image I’ve seen.” This 50-light-year-wide view of the nebula’s central region shows a maelstrom of star birth and death. The mosaic was assembled from 48 frames taken with Hubble’s Advanced Camera for Surveys, with information added from the Cerro Tololo Inter-American Observatory in Chile.

What outside interests—e.g., hobbies, service, dreams, activities—could you share that would help others understand you better?

When I was around 10, my father and I started playing duplicate bridge at a local club on Saturdays. Many of the other partnerships would argue with one another over their play, but not us. Dad and I did our best, celebrated our good plays, and learned from our mistakes, but never got angry with one another. My parents’ unwavering support, pride, encouragement, and engagement of my curiosity have made me the astronomer I am today. I do my best to keep making them proud.

Dan, at the age of 11, poses with his mom and dad.

Dan, at the age of 11, poses with his dad and mom.

Is there anything else that you think is important for readers to know about you?

I feel very fortunate to be paid to do what I love. And I have been privileged. Like many others at STScI, I work hard and try to give back in small part by sharing the rich history of our universe with others in Baltimore and with people around the world. I hope you enjoy hearing our stories.

Also see “Spotlight on Jennifer Mack, Research and Instrument Scientist.”

Spotlight on Jennifer Mack, Research and Instrument Scientist

This occasional series focuses on members of the Frontier Fields team.  It highlights the individuals, their jobs, and the paths they took to get to where they are today.   

This is a picture of Jennifer Mack, a Hubble Research and Instrument Scientist.

Jennifer Mack, a Hubble Research and Instrument Scientist, answers questions about her role on the Frontier Fields project.

What is your position?

My formal title is Research & Instrument Scientist in Hubble Space Telescope’s Instruments Division. I help manage the Frontier Fields data pipeline, which delivers the best possible calibrated data products to the astronomical community. I am also part of the WFC3 [Wide Field Camera 3] Instrument team where I work on calibration of the UVIS [ultraviolet and visible light] and IR [infrared light] detectors.

What is a “data pipeline” and what does it mean to “calibrate”?

A data pipeline is a set of software for processing and combining sets of images. It includes tools to correct for instrument artifacts, such as bad pixels, thermal signal from the detectors, and variations in sensitivity across the field of view. The goal of calibration is to tie the brightness of objects measured in Hubble’s cameras to some absolute system, based on measurements of stars of known brightness.

What does a typical day on the job entail? What are your responsibilities?

The data pipeline team keeps an eye on the Frontier Fields images as they are arriving from the telescope. For a given cluster, these come in a steady stream over a period of about 6 weeks, so we have to keep on top of things. First and foremost we need to be sure that the telescope was pointing in the right place and that it was stable throughout the exposure.

We also develop software to correct the images for artifacts that aren’t automatically handled by Hubble’s standard calibration pipeline. This includes masking out artifacts like satellite trails or scattered light from bright stars. We also mask IR ‘persistence’ which is leftover signal from very bright objects in observations taken just prior to ours. For the IR detector, we correct the images for stray light, usually from the bright Earth, that varies with time over the course of an exposure. For the ACS [Advanced Camera for Surveys] detector, we correct for artifacts like hot pixels and charge transfer losses during readout, both of which are considerable after being in space for 13 years.

Once that is complete, we correct the images for distortion and align them. These are then stacked together to create full-depth mosaics for each filter using specialized software called AstroDrizzle which allows us to optimize the resolution of the final images.

What specifically is your background?

I have a BS in physics and an MS in astrophysics. I’ve been at Space Telescope since 1996, and over the years have helped calibrate Hubble’s main imaging cameras: WFPC2 [Wide-Field Planetary Camera 2], ACS, and now WFC3.

What particularly interested you in school or growing up?  What were your favorite subjects?

I was particularly interested in science and math in high school. I remember in physics class we had to predict the landing spot of a marble rolled down an inclined plane and off of the side of a table. Measuring only the height of the incline, the height of the table, and the time the marble was in the air, we were able to calculate where on the floor the marble would land and then put a paper cup there to catch it. I was amazed that this actually worked and was struck by the power of mathematics to predict events which seemed like magic to me.

How did you first become interested in space?

My birthday coincides with the peak of the Perseid meteor shower. This is a particularly spectacular event in southwest Colorado where I grew up, and when I was little I asked my mom if the meteors were special for my birthday. She cleverly told me that they must be, and that felt very magical to me. When I got older, friends and I would hike to the top of a mountain and lay back to get a full view of the night sky. As the meteors streaked across the sky, we would imagine that we were clinging to the side of the Earth, spinning at 1000 miles/hour, and trying not float away into space. Growing up under really dark skies really sparked my curiosity about space and made me think about all the mysteries still undiscovered.

Was there someone (parent, teacher, spouse, sibling, etc.) or something (book, TV show, lecture etc.) that influenced you in developing a love for what you do, or the program you’re a part of?

When I was young, I asked a lot of questions and especially wanted to understand how and why things worked. My parents never said “I don’t know,” but took the time to show me how to find answers, either in books or on the computer. We watched a lot of nature documentaries together, including the original Cosmos series which resulted in a lot of interesting discussions. My parents really listened to my questions and as a result instilled in me a general curiosity and love of learning.

Is there a particular image or result that especially fascinates you?

I’ve always been fascinated by galaxy clusters, and the Frontier Fields images are pushing the limits of HST’s instruments to the extreme. By combining very deep exposures with the power of a gravitational lens, we are able to look back even further in time to view galaxies when the Universe was only 500 million years old. When you create very deep images like these, limitations in the current instrument calibration become apparent. We are developing new techniques to do cutting-edge calibration and sharing these new methods with the user community in the hope of allowing for the best possible science with HST. It’s exciting to be a part of all this new discovery!

Are there specific parts of the program that you’re particularly proud to have contributed to?

In addition to my Frontier Fields work, I’m proud to be a member of the Hubble Heritage Team, which produces some of the most iconic astronomy images ever. These images are designed specifically for the purpose of inspiring people, and I think that is an especially worthy pursuit! My specialty is in understanding Hubble’s instruments, and I work on designing the observations and also in calibrating and aligning the images once they have been acquired. Some recent mosaics I’ve had the pleasure of working on include hits like the Eagle Nebula, Westerlund 2, the Monkey Head Nebula, and the Horsehead Nebula.

Is there anything else that you think is important for readers to know about you?

I have a 5-year-old son who loves space and especially playing Lego “Hubble Rescue” to reenact the servicing missions. One of his more memorable quotes: “Hey mom, how about this time I be Mike Massimino and you be John Grunsfeld!” Being able to share my passion for astronomy with my son has been especially rewarding. [Editor’s note: Mike Massimino performed spacewalks on two Hubble servicing missions, and John Grunsfeld is a spacewalking veteran of three Hubble servicing missions.]

This picture shows Jennifer Mack enjoying time  with her son in a field in Colorado.

Jennifer Mack enjoying time in Colorado with her son.

 For more information on the processing of Hubble images, please see these posts:

For more information on how Hubble images are proposed, planned, and scheduled, please see these posts:

James Edwin Webb: Turning Imagination into Reality

by Holly Ryer and Ann Jenkins

The Frontier Fields program peers into the universe’s distant past, yet it also offers a glimpse of the future work that the powerful James Webb Space Telescope will conduct. Webb, known as Hubble’s successor, will use infrared vision to detect galaxies beyond even Hubble’s reach.

But the man for whom the Webb telescope is named is not commonly linked to space science. James Edwin Webb (1906–1992) wasn’t a scientist or engineer; he was a businessman, attorney, and manager. Still, many believe that this second administrator of NASA, who ran the fledgling agency from 1961 to 1968, did more to advance science and space exploration than perhaps any other government official. He laid the foundations at NASA for one of the most successful periods of astronomical discovery, one that continues today.

James Edwin Webb, the second administrator of NASA, was a staunch champion of space exploration. Photo credit: NASA.

James Webb was born in Granville County, N.C. He completed his college education at the University of North Carolina at Chapel Hill, where he received a degree in education. Webb then became a second lieutenant in the United States Marine Corps and served as a Marine Corps pilot. Afterward, he studied law at the George Washington University Law School in Washington, D.C. and was admitted to the Bar of the District of Columbia in 1936.

Webb’s long career in public service included serving as director of the Bureau of Budget and Under Secretary of State under President Harry Truman. In 1961, when he was selected by President John Kennedy to serve as the NASA administrator, Webb was reluctant to take the job. He assumed that it might be better handled by someone with a firmer grasp of science or technology. However, Kennedy wanted a leader with keen political insight and management skills for the position.

Webb oversaw great progress in the Space Program while serving as NASA’s administrator. During his tenure, NASA developed robotic spacecraft, which explored the lunar environment so that astronauts could do so later. On his watch, NASA also sent scientific probes to Mars and Venus. By the time Webb retired, NASA had launched more than 75 space science missions to study the stars and galaxies, our own Sun and the as-yet-unknown environment of space above the Earth’s atmosphere.

Webb also weathered the turmoil of the 1967 Apollo 1 tragedy, in which three astronauts—“Gus” Grissom, Edward White, and Roger Chaffee—died in a flash fire during a simulation test on the launch pad at Kennedy Space Center in Florida. Firmly committed to getting NASA back on its feet after this terrible setback, Webb strove to maintain support for the program. His success helped to pave the way to future NASA triumphs, such as the historic Apollo moon landing, which took place shortly after his retirement from NASA in 1968.

Webb remained in Washington, D.C., where he served on several advisory boards and as a regent of the Smithsonian Institution. In 1981, he was awarded the Sylvanus Thayer Award by the United States Military Academy at West Point for his dedication to his country. Former NASA Administrator Sean O’Keefe said of Webb: “He took our nation on its first voyages of exploration, turning our imagination into reality.”

Edwin Hubble Expands Our View of the Universe

by Donna Weaver and Ann Jenkins

American astronomer Edwin Powell Hubble (1889–1953) never lived to see the development or launch of his namesake, the Hubble Space Telescope. But like the telescope that bears his name, Dr. Hubble played a crucial role in advancing the field of astronomy and changing the way we view the universe. As Hubble’s namesake is breaking new ground in the exploration of the distant universe via the Frontier Fields, let us take a step back and learn more about Hubble, the man.

This is an illustration of Dr. Edwin Powell Hubble.

Edwin Hubble is regarded as one of the most important observational cosmologists of the 20th century. Illustration credit: Kathy Cordes of STScI.

As a young boy, Edwin Hubble read tales of traveling to undersea cities, journeying to the center of the Earth, and trekking to the remote mountains of South Africa. These stories by adventure novelists Jules Verne and H. Rider Haggard stoked young Hubble’s imagination of faraway places. He fulfilled those childhood dreams as an astronomer, exploring distant galaxies with a telescope and developing celestial theories that revolutionized astronomy.

But Hubble didn’t settle immediately on the astronomy profession. He studied law as a Rhodes Scholar at Queens College in Oxford, England. A year after passing the bar exam, Hubble realized that his love of exploring the stars was greater than his attraction to law, so he abandoned law for astronomy. “I chucked the law for astronomy and I knew that, even if I were second rate or third rate, it was astronomy that mattered,” Hubble said. (1)

Our Galaxy Is Not Alone

He studied astronomy at the University of Chicago and completed his doctoral thesis in 1917. After serving in World War I, he began working at the Mount Wilson Observatory near Pasadena, Calif., studying the faint patches of luminous “fog” or nebulae — the Latin word for clouds — in the night sky. Hubble and other astronomers were puzzled by these gas clouds and wanted to know what they were.

Using the 100-inch reflecting Hooker Telescope — the largest telescope of its day — Hubble peered beyond our Milky Way Galaxy to study an object known then as the Andromeda Nebula. He discovered special, “variable stars” on the outskirts of the nebula that changed in brightness over time. These stars brightened and dimmed in a predictable way that allowed Hubble to determine their distances from Earth. Hubble showed that the distance to the nebula was so great that it had to be outside the Milky Way Galaxy. Hubble realized that the Andromeda Nebula was a separate galaxy much like our own. The discovery of the Andromeda Galaxy helped change our understanding of the universe by proving the existence of other galaxies.

Hubble also devised the classification system for galaxies, grouping them by sizes and shapes, that astronomers still use today. He also obtained extensive evidence that the laws of physics outside our galaxy are the same as on Earth, verifying the principle of the uniformity of nature.

The Expanding Universe

As Hubble continued his study, he made another startling discovery: The universe is expanding. In 1929 he determined that the more distant the galaxy is from Earth, the faster it appears to move away. Known as Hubble’s Law, this discovery is the foundation of the Big Bang theory. The theory says that the universe began after a huge cosmic explosion and has been expanding ever since. Hubble’s discovery is considered one of the greatest triumphs of 20th-century astronomy.

Albert Einstein could have foretold Hubble’s discovery in 1917 when he applied his newly developed General Theory of Relativity to the universe. His theory — that space is curved by gravity — predicted that the universe could not be static but had to expand or contract. Einstein found this prediction so unbelievable that he modified his original theory to avoid the problem. Upon learning of Hubble’s discovery, Einstein immediately regretted revising his theory.

For his many contributions to astronomy, Hubble is regarded as one of the most important observational cosmologists of the 20th century.

(1) As quoted by Nicholas U. Mayall (1970). Biographical memoir. Volume 41, Memoirs of the National Academy of Sciences, National Academy of Sciences (U.S.). National Academy of Sciences. p. 179.

How Hubble Observations Are Scheduled

This is the third in a three-part series.

After observing time is awarded, the Institute creates a long-range plan. This plan ensures that the diverse collection of observations are scheduled as efficiently as possible. This task is complicated because the telescope cannot be pointed too close to bright objects like the Sun, the Moon, and the sunlit side of Earth. Adding to the difficulty, most astronomical targets can only be seen during certain months of the year; some instruments cannot operate in the high space-radiation areas of Hubble ’s orbit; and the instruments regularly need to be calibrated. These diverse constraints on observations make telescope scheduling a complex optimization problem that Institute staff are continually solving, revising, and improving.”

Preparing for an observation also involves selecting guide stars to stabilize.the telescope’s pointing and center the target in the instrument’s field of view. The selection is done automatically by the Institute’s computers, which choose two stars per pointing from a catalog of almost a billion stars. These guide stars will be precisely positioned within the telescope’s fine guidance sensors, ensuring that the target region and orientation of the sky is observed by the desired instrument.”]

A weekly, short-term schedule is created from the long-range plan. This schedule is translated into detailed instructions for both the telescope and its instruments to perform the observations and calibrations for the week. From this information, daily command loads are then sent from the Institute to NASA’s Goddard Space Flight Center to be uplinked to Hubble.

Hubble’s Flight Operations Team resides in the Space Telescope Operations Control Center at NASA’s Goddard Space Flight Center in Greenbelt, Md.  In addition to monitoring the health and safety of the telescope, they also send command loads to the spacecraft, monitor their execution, and arrange for transmission of science and engineering data to the ground.

Hubble’s Flight Operations Team resides in the Space Telescope Operations Control Center at NASA’s Goddard Space Flight Center in Greenbelt, Md. In addition to monitoring the health and safety of the telescope, they also send command loads to the spacecraft, monitor their execution, and arrange for transmission of science and engineering data to the ground.

The journey from proposal through selection and scheduling culminates in the email informing astronomers that their data is ready to be accessed. Usually, the process takes more than a year from idea to data—sometimes even longer. Of course, that’s when the real work begins—the analysis of the data and the hard work of uncovering another breakthrough Hubble discovery!

How Hubble Observations Are Planned

This is the second in a three-part series.

Researchers awarded telescope time based on the scientific merit of their Phase I proposal must submit a Phase II proposal that specifies the many details necessary for implementing and scheduling of the observations. These details include such items as precise target locations and the wavelengths of any filters required.

Once an observation has occurred, the data becomes part of the Hubble archive, where astronomers can access it over the Internet. Most data is marked as proprietary within the Institute computer systems for 12 months. This protocol allows observers time to analyze the data and publish their results. At the end of this proprietary-data-rights period, the data is made available to the rest of the astronomical community. (Most of the very large programs, such as Frontier Fields, have given up proprietary time as part of their proposal.)

This is a view of the many computers that are part of the Barbara A. Mikulski Archive for Space Telescopes (MAST), located at the Space Telescope Science Institute (STScI) in Baltimore, Md. The archive is named in honor of the United States Senator from Maryland for her career-long achievements and becoming the longest-serving woman in U.S. Congressional history. MAST is NASA’s repository for all of its optical and ultraviolet-light observations, some of which date to the early 1970s. The archive holds data from 16 NASA telescopes, including current missions such as the Hubble Space Telescope and Kepler. Senator Mikulski is in the center, STScI Director Matt Mountain at her right, and STScI Deputy Director Kathryn Flanagan at her left. The plaque to image right is a photo of Supernova Milkuski, an exploding star that the Hubble Space Telescope spotted on Jan. 25, 2012. It was named in honor of the Senator by Nobel Laureate Adam Riess and the supernova search team with which he is currently working. The supernova, which lies 7.4 billion light-years away, is the titanic detonation of a star more than eight times as massive as our Sun.

This is a view of the many computers that are part of the Barbara A. Mikulski Archive for Space Telescopes (MAST), located at the Space Telescope Science Institute (STScI) in Baltimore, Md. The archive is named in honor of the United States Senator from Maryland for her career-long achievements and becoming the longest-serving woman in U.S. Congressional history. MAST is NASA’s repository for all of its optical and ultraviolet-light observations, some of which date to the early 1970s. The archive holds data from 16 NASA telescopes, including current missions such as the Hubble Space Telescope and Kepler. Senator Mikulski is in the center, STScI Director Matt Mountain at her right, and STScI Deputy Director Kathryn Flanagan at her left. The plaque to image right is a photo of Supernova Milkuski, an exploding star that the Hubble Space Telescope spotted on Jan. 25, 2012. It was named in honor of the Senator by Nobel Laureate Adam Riess and the supernova search team with which he is currently working. The supernova, which lies 7.4 billion light-years away, is the titanic detonation of a star more than eight times as massive as our Sun.

Along with their Phase II proposal, observers can also apply for a financial grant to help them process and analyze the observations. These grant requests are reviewed by an independent financial review committee, which then makes recommendations to the Institute director for funding. Grant funds are also available for researchers who submit Phase I proposals to analyze non-proprietary Hubble data already archived. The financial committee evaluates these requests as well.

Up to 10 percent of Hubble ’s time is reserved as director’s discretionary time and is allocated by the Institute director. Astronomers can apply to use these orbits any time during the course of the year. Discretionary time is typically awarded for the study of unpredictable phenomena such as new supernovae or the appearance of a new comet. Historically, directors have allocated large percentages of this time to special programs that are too big to be approved for any one astronomy team. For example, the observations of the Frontier Fields use director’s discretionary time.

In my last post, I talked about how observations are proposed.  In my next post, I will talk about how observations are scheduled.

How Hubble Observations Are Proposed

This is the first in a three-part series. 

Time on the Hubble Space Telescope is a precious commodity. As a space telescope, Hubble can observe 24 hours a day, but its advantageous perch also attracts a large number of astronomers who want to use it. The current oversubscription rate—the amount of time requested versus time awarded—is six to one.

The process of observing with Hubble begins with the annual Call for Proposals issued by the Space Telescope Science Institute to the astronomical community. Astronomers worldwide are given approximately two months to submit a Phase I proposal that makes a scientific case for using the telescope. Scientists typically request the amount of telescope time they desire in orbits. It takes 96 minutes for the telescope to make one trip around the Earth, but because the Earth usually blocks the target for part of the orbit, typical observing time is only about 55 minutes per orbit.

Longer observations require a more compelling justification since only a limited number of orbits are available. Winning proposals must be well reasoned and address a significant astronomical question or issue. Potential users must also show that they can only accomplish their observations with Hubble ’s unique capabilities and cannot achieve similar results with a ground-based observatory.

The Institute assembles a time allocation committee (TAC), comprising experts from the astronomical community, to determine which proposals will receive observing time. The committee is subdivided into panels that review the proposals submitted within a particular astronomical category. Sample categories include stellar populations, solar system objects, and cosmology. The committee organizers take care to safeguard the process from conflicts of interest, as many of the panel members are likely to have submitted, or to be a co-investigator, on their own proposals.

The time allocation committee (TAC) discusses which proposals will receive observing time on Hubble.

The time allocation committee (TAC) discusses which proposals will receive observing time on Hubble.

Proposals are further identified as general observer (GO), which range in size from a single orbit to several hundred, or snapshot, which require only 45 minutes or less of telescope time. Snapshots are used to fill in gaps within Hubble ’s observing schedule that cannot be filled by general observer programs. Once the committee has reviewed the proposals and voted on them, it provides a recommended list to the Institute director for final approval.

In my next post, I will discuss how observations are planned.