Predicted Reappearance of Supernova Refsdal Confirmed

Hubble has captured an image of the first-ever predicted supernova explosion.

In November 2014, Hubble’s Frontier Fields program caught sight of a supernova called “Refsdal” while examining the MACS J1149.5+2223 galaxy cluster. Astronomers spotted four separate images of the supernova in a rare arrangement known as an “Einstein Cross” around a galaxy within the cluster.

The four images of the same supernova result from the way light from distant objects is not just magnified but bent by the immense mass of the galaxy cluster. (Link: http://frontierfields.org/2014/07/09/seeing-double-or-more-in-frontier-fields-images/)

Seeing such distant, gravitationally lensed objects is, of course, the point of the Frontier Fields project, but this one had a special quirk. By studying different models of just how mass is positioned in the galaxy cluster, astronomers could predict one more light path for Refsdal, one that would delay the light reaching the telescope until late 2015 or early 2016. This means they could predict when and where in the field the image of the supernova would appear next.

Astronomers began taking snapshots of the predicted area over an expected time period. And sure enough, on Dec. 11, 2015, the astronomers captured the reappearance of the supernova where they had anticipated it would be. The detection of this fifth appearance of the Refsdal supernova served as a unique opportunity for astronomers to test their models of how mass — especially that of mysterious dark matter — is distributed within this galaxy cluster, and they seem to be right on track.

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These images show the search for the supernova, nicknamed Refsdal, using NASA’s Hubble Space Telescope. The image on the left is the galaxy cluster MACS J1149.5+2223 from the Frontier Fields program. The circle indicates the empty but predicted position of the newest appearance of the supernova. The image at top right shows observations taken by Hubble on Oct. 30, 2015, at the beginning of the observation program to detect the newest appearance of the supernova. The image on the lower right shows the discovery of the Refsdal supernova on Dec. 11, 2015, as predicted by several different models.

Credit: NASA, ESA, and P. Kelly (University of California, Berkeley)

Acknowledgment: NASA, ESA, and S. Rodney (University of South Carolina) and the FrontierSN team; T. Treu (UCLA), P. Kelly (UC Berkeley) and the GLASS team; J. Lotz (STScI) and the Frontier Fields team; M. Postman (STScI) and the CLASH team; and Z. Levay (STScI)

How Hubble “Sees” Gravity

[Note: this post is cross-posted on the Hubble’s Universe Unfiltered blog.]

Gravity is the familiar force of nature responsible for the diverse motions of a baseball thrown high into the air, a planet orbiting a star, or a star orbiting within a galaxy. Astronomers have long observed such motions and deduced the amount of gravity, and therefore the amount of matter, present in the planet, star, or galaxy. When taken to the extreme, gravity can also create some intriguing visual effects that are well suited to Hubble’s high-resolution observations.

Einstein’s general theory of relativity expresses how very large mass concentrations distort the space around them. Light passing through that distorted space is re-directed, and can produce a variety of interesting imagery. The bending of light by gravity is similar to the bending of light by a glass lens, hence we call this effect “gravitational lensing”.

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An “Einstein Cross” gravitational lens.

The simplest type of gravitational lensing is called “point source” lensing. There is a single concentration of matter at the center, such as the dense core of a galaxy. The light of a distant galaxy is re-directed around this core, often producing multiple images of the background galaxy (see the image above for an example). When the lensing approaches perfect symmetry, a complete or almost complete circle of light is produced, called an “Einstein ring”. Hubble observations have helped to greatly increase the number of Einstein rings known to astronomers.

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Gravitational lensing in galaxy cluster Abell 2218

More complex gravitational lensing arises in observations of massive clusters of galaxies. While the distribution of matter in a galaxy cluster generally does have a center, it is never perfectly circularly symmetric and is usually significantly lumpy. Background galaxies are lensed by the cluster with their images often appearing as short thin “lensed arcs” around the outskirts of the cluster. Hubble’s images of galaxy clusters, such as Abell 2218 (above) and Abell 1689, showed the large number and detailed distribution of these lensed images throughout massive galaxy clusters.

These lensed images also act as probes of the matter distribution in the galaxy cluster. Astronomers can measure the motions of the galaxies within a cluster to determine the total amount of matter in the cluster. The result indicates that the most of the matter in a galaxy cluster is not in the visible galaxies, does not emit light, and is thus called “dark matter”. The distribution of lensed images reflects the distribution of all matter, both visible and dark. Hence, Hubble’s images of gravitational lensing have been used to create maps of dark matter in galaxy clusters.

In turn, a map of the matter in a galaxy cluster helps provide better understanding and analysis of the gravitational lensed images. A model of the matter distribution can help identify multiple images of the same galaxy or be used to predict where the most distant galaxies are likely to appear in a galaxy cluster image. Astronomers work back and forth between the gravitational lenses and the cluster matter distribution to improve our understanding of both.

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Three lensed images of a distant galaxy seen through a cluster of galaxies.

On top of it all, gravitational lenses extend Hubble’s view deeper into the universe. Very distant galaxies are very faint. Gravitational lensing not only distorts the image of a background galaxy, it can also amplify its light. Looking through a lensing galaxy cluster, Hubble can see fainter and more distant galaxies than otherwise possible. The Frontier Fields project has examined multiple galaxy clusters, measured their lensing and matter distribution, and identified a collection of these most distant galaxies.

While the effects of normal gravity are measurable in the motions of objects, the effects of extreme gravity are visible in images of gravitational lensing. The diverse lensed images of crosses, rings, arcs, and more are both intriguing and informative. Gravitational lensing probes the distribution of matter in galaxies and clusters of galaxies, as well as enables observations of the distant universe. Hubble’s data will also provide a basis and guide for the future James Webb Space Telescope, whose infrared observations will push yet farther into the cosmos.

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A “smiley face” gravitational lens in a galaxy cluster.

The distorted imagery of gravitational lensing often is likened to the distorted reflections of funhouse mirrors, but don’t take that comparison too far. Hubble’s images of gravitational lensing provide a wide range of serious science.

‘Hubble’s Views of the Deep Universe’ – Public Lecture

On November 3, 2015, I gave a presentation called “Hubble’s Views of the Deep Universe”.  This presentation was to commemorate some of Hubble’s most influential observing campaigns during this 25th anniversary year.  Of course, I could not get to all of Hubble’s programs that observed the deep universe in just an hour.  For additional information, check out the science articles on the Hubble 25th website and, of course, keep checking back to this blog.

Dr. Brandon Lawton
“Hubble’s Views of the Deep Universe”

November 3, 2015

For two decades, the Hubble Space Telescope has pioneered the exploration of the distant universe with images known as the “deep fields”. These deep fields have given astronomers unprecedented access to understanding how galaxies form and develop over billions of years in the history of our universe, from shortly after the Big Bang to today. Join us for a retrospective view of Hubble’s contributions to the investigation of the deep reaches of the cosmos and some fresh glimpses of what Hubble is currently doing to further our understanding of the most distant parts of the universe.

This lecture is part of the monthly public lecture series at the Space Telescope Science Institute in Baltimore, Maryland. Each month addresses a different cosmic topic, usually related to Hubble, but always venturing to some fascinating part of the universe. For more information, check out the web page on HubbleSite:
http://hubblesite.org/about_us/public_talks/

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.”

New Interactive Explorer for Galaxy Cluster Abell 2744

The high-resolution images taken by the Hubble Space Telescope for the Frontier Fields survey have yielded a treasure trove of insights into very distant galaxy clusters.  In addition to providing astronomers with unparalleled views of galaxies that Hubble would not otherwise be able to see, the high-resolution images are providing views of distant corners of the universe that are similar to the famous Hubble Deep Fields.

To give you some idea of just how detailed and rich the Frontier Field images are, an astronomer at the Space Telescope Science Institute has created this interactive viewer to explore them yourself:

Click here to explore the Abell 2744 yourself:

Abell 2744 Viewer

To help you use and navigate the viewer, we’ve created a short video to help familiarize you with the interface and controls.  Over time, we’ll be adding more of the Frontier Fields clusters, so be sure to check back for updates.

Astronomers Gather from Around the World

From August 3-14, thousands of astronomers from around the world gathered in Honolulu, Hawaii, to discuss the latest astronomical discoveries at the International Astronomical Union (IAU) General Assembly. The Frontier Fields had a highly visible role during this two-week meeting, including a fascinating three-day focus meeting where all things Frontier Fields were discussed, including recent science results and the future of the Frontier Fields. In this post, I will highlight just a few of the Frontier Fields highlights at the IAU General Assembly.

 

The Frontier Fields was highlighted with a 3-day focus meeting at the International Astronomical Union general assembly meeting in Honolulu, Hawaii.

The Frontier Fields was highlighted with a three-day focus meeting at the International Astronomical Union General Assembly meeting in Honolulu, Hawaii. The focus meeting was kicked off with a great introductory talk by Dr. Jennifer Lotz (Principal Investigator of the Hubble Frontier Fields program).

A Wealth of Science

The Frontier Fields focus meeting covered much of the latest and greatest science results coming from the Frontier Fields program. Some of the new results included deeper understandings of galaxies in the distant universe, more complete pictures of the massive galaxy clusters, and the searches for exploding massive stars, called supernovae. Some big points of discussion at the focus meeting included the methods by which astronomers obtained and studied the Frontier Fields data. These methods included the analysis of the images and spectra as well as the development of physics-based models of gravitational lensing around the Frontier Fields galaxy clusters. The modeling efforts continue to be incredibly important because they tie our physics-based understanding of how gravitational lensing works with the observations of gravitational lensing, and they allow astronomers to accurately search for and study extremely distant and lensed galaxies.

We will highlight some of the new results in future blog posts.

As for the Hubble Frontier Fields, it was nice to see the progress on the observing campaign. Hubble is two-thirds of the way through its Frontier Fields observing campaign, having completed observations of four out of the six massive galaxy clusters and their four associated parallel fields. The completed Hubble Frontier Fields images are shown below.

Shown on the left is the galaxy cluster Abell 2744. Shown on the right is the adjacent parallel field.

Shown on the left is the galaxy cluster Abell 2744. Shown on the right is the adjacent parallel field. This was the first completed pair of targets in the Hubble Frontier Fields program.
Credit: NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI)

 

Shown on the left is the galaxy cluster MACS J0416. Shown on the right is the adjacent parallel field. These were the second completed targets of the Hubble Frontier Fields program.

Shown on the left is the galaxy cluster MACS J0416. Shown on the right is the adjacent parallel field. This was the second pair of completed targets in the Hubble Frontier Fields program.
Credit: NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI)

 

Shown on the left is the galaxy cluster MACS J0717. Shown on the right is the adjacent parallel field. These were the third pair of completed targets of the Hubble Frontier Fields program. This marked the halfway point of the Hubble Frontier Fields observing campaign and were completed in the Spring of 2015, around the 25th anniversary of the Hubble Space Telescope.

Shown on the left is the galaxy cluster MACS J0717. Shown on the right is the adjacent parallel field. This was the third pair of completed targets in the Hubble Frontier Fields program. This marked the halfway point of the Hubble Frontier Fields observing campaign. The MACS J0717 observations were completed in the spring of 2015, around the 25th anniversary of the Hubble Space Telescope.
Credit: NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI)

 

Shown on the left is the galaxy cluster MACS J1149. Shown on the right is the adjacent parallel field. These were the fourth pair of completed targets of the Hubble Frontier Fields program.

Shown on the left is the galaxy cluster MACS J1149. Shown on the right is the adjacent parallel field. This was the fourth pair of completed targets in the Hubble Frontier Fields program.
Credit: NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI)

A Truly Multi-Mission Effort

Perhaps the most exciting aspect of the Frontier Fields focus meeting at the IAU was hearing from the multitude of ground- and space-based missions investigating the Frontier Fields. These observatories cover a wide range of the electromagnetic spectrum, from high-energy X-rays to low-energy radio waves. Scientific results were mentioned during this focus meeting from data obtained by the Hubble Space Telescope, the Chandra X-ray Observatory, the Jansky Very Large Array, the Very Large Telescope, the Atacama Large Millimeter/submillimeter Array, the Keck Observatory, the James Clerk Maxwell Telescope, the Herschel Space Observatory, and others. There was also a discussion of how the future James Webb Space Telescope will help us understand the cosmic frontier probed by the Frontier Fields.

With so many telescopes staring at these 12 patches of the sky, a wealth of data is being accumulated and studied that will keep astronomers busy for years to come. We truly expect the science from the Frontier Fields to redefine our understanding of massive galaxy clusters and the distant universe.

Sharing the Story

The Frontier Fields were highlighted in many other venues at the IAU meeting, not just during the Frontier Fields focus meeting. The Frontier Fields were a part of a Hubble 25th anniversary image gallery exhibit in the main concourse area of the convention center. A presentation was given to the astronomy education and outreach community about how the Frontier Fields are being incorporated into education and outreach products by the Office of Public Outreach at the Space Telescope Science Institute. Frontier Fields materials were available at the official NASA exhibit during the IAU meeting.

Perhaps the most stunning display of the Frontier Fields occurred at NASA’s hyperwall. The hyperwall is a high-definition video wall that provides a large and clear view of astronomical images and visualizations. Dr. Rachael Livermore (University of Texas, Austin) gave a visually stunning tour through Hubble’s Frontier Fields, including visualizations that highlighted the effects of gravitational lensing. Dr. Christine Jones (Harvard-Smithsonian Center for Astrophysics) gave a truly spectacular multiwavelength, multi-mission view of the Frontier Fields that included data from the Hubble Space Telescope, the Chandra X-ray Observatory, and the Jansky Very Large Array.

NASA’s hyperwall is always a big draw at professional astronomy meetings, public outreach events, and informal education venues. I highly encourage you to attend a hyperwall talk if you happen to be in the neighborhood of an event that has the NASA hyperwall.  You can follow NASA’s hyperwall on Twitter – @NASAHyperwall .

 

The Frontier Fields were featured, in high-definition, on NASA's Hyperwall. Top - Rachael Livermore presents the current status of Hubble's Frontier Fields. Bottom - Christine Jones-Forman presents a multiwavelength view of the Frontier Fields.

Images from the Frontier Fields were featured, in high definition, on NASA’s hyperwall. Top: Dr. Rachael Livermore presents the current status of Hubble’s Frontier Fields. Bottom: Dr. Christine Jones presents a multiwavelength view of the Frontier Fields.

 

 

 

 

 

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:

Galaxy Shapes in the Frontier Fields Observations

We can learn a lot about galaxies by analyzing their light, through computer modeling, and using other complex techniques. But at the most basic level, we can learn about galaxies by studying their shapes.

Galaxy appearance immediately reveals certain characteristics. Elliptical galaxies contain a wealth of old stars. Spiral galaxies are full of gas and dust. Distorted galaxies have likely experienced a gravitational interaction with another galaxy that warped their structure.

The Mice, as these colliding galaxies are called, are a pair of spiral galaxies seen about 160 million years after their closest encounter. Gravity has drawn stars and gas out of the galaxies into long tails.  Credit: NASA, H. Ford (JHU), G. Illingworth (UCSC/LO), M.Clampin (STScI), G. Hartig (STScI), the ACS Science Team, and ESA

The Mice, as these distorted colliding galaxies are called, are a pair of spiral galaxies seen about 160 million years after their closest encounter. Gravity has drawn stars and gas out of the galaxies into long tails. Credit: NASA, H. Ford (JHU), G. Illingworth (UCSC/LO), M.Clampin (STScI), G. Hartig (STScI), the ACS Science Team, and ESA

The Frontier Fields project adds another dimension to this simple analysis. When we look at extremely distant galaxies with the magnification of gravitational lensing, we see new detail that was previously obscured by distance. Their shapes are clues to what occurred within those galaxies when they were very young.

Galaxies viewed through the gravitational lenses of the Frontier Fields clusters can be seen at a resolution 10 times greater than non-lensed galaxies. That means those tiny red dots that so thrill astronomers in normal Hubble images actually have some structure in Frontier Fields imagery.

Previous studies, such as the Hubble Ultra Deep Field, The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, or even adaptive optics-enhanced studies by ground telescopes have shown that young, star-forming galaxies at about a redshift of 2 (existing when the universe was about 3.3 billion years old) appear to have a certain lumpiness. But without gravitational lensing, we lack the resolution to say for sure whether those lumps were massive clusters of newly forming stars, or whether some other factor was causing those galaxies to have a clumpy appearance.

Frontier Fields has revealed that yes, many of those galaxies have star-forming knots that really are quite large, implying that star formation occurred in a very different way in the early universe, perhaps involving greater quantities of gas in those young galaxies than previously expected.

Frontier Fields has also given us a better grasp of the physical size of gravitationally lensed young galaxies even farther away, at a redshift of 9 (when the universe was around 500 million years old). Observations show that these galaxies are actually quite small – perhaps 200 parsecs across, while a typical galaxy you see today is closer to 10,000 parsecs across. These observations help plan future observations with the Webb Space Telescope, picking out what will hopefully be the best targets for study.

This composite image shows examples of galaxies similar to our Milky Way at various stages of construction over a time span of 11 billion years. The galaxies are arranged according to time. Those on the left reside nearby; those at far right existed when the cosmos was about 2 billion years old. The Frontier Fields project is collecting galaxies from the earliest epochs of the universe to add to such comparisons. Credit: NASA, ESA, P. van Dokkum (Yale University), S. Patel (Leiden University), and the 3D-HST Team

This composite image shows examples of galaxies similar to our Milky Way at various stages of construction over a time span of 11 billion years. The galaxies are arranged according to time. Those on the left reside nearby; those at far right existed when the cosmos was about 2 billion years old. The Frontier Fields project is collecting galaxies from the earliest epochs of the universe to add to such comparisons. Credit: NASA, ESA, P. van Dokkum (Yale University), S. Patel (Leiden University), and the 3D-HST Team

Galaxy shape also plays a role in discoveries in the Frontier Fields’ six parallel fields, which are unaffected by gravitational lensing but provide a view into space almost as deep as Hubble’s famous Ultra Deep Field, with three times the area.

It’s well known that galaxies collide and interact, drawn to one another by gravity. Most galaxies in the universe are thought to have gone through the merger process in the early universe, but the importance of this process is an open question. The transitional period during which galaxies are interacting and merging is relatively short, making it difficult to capture. A distant galaxy may appear clumpy and distorted, but is its appearance due to a merger – or is it just a clumpy galaxy?

Collision-related features — such as tails of stars and gas drawn out into space by gravity, or shells around elliptical galaxies that occur when stars get locked into certain orbits – are excellent indicators of merging galaxies but are hard to detect in distant galaxies with ordinary observations. Frontier Fields’ parallel fields are providing astronomers with a collection of faraway galaxies with these collision-related features, allowing astronomers to learn more about how these mergers affected the galaxies we see today.

As time goes on and the cluster and parallel Frontier Fields are explored in depth by astronomers, we expect to to learn much more about how galaxy evolution and galaxy shapes intertwine. New results are on the way.

The Incredible Time Machine

Today’s guest post is by Mary Estacion. Mary is the News Video Producer at the Space Telescope Science Institute. She is also the host and producer of the “Behind the Webb” podcast series, which showcases the James Webb Space Telescope as it is being built as well as the engineers and scientists working on the observatory. The video in this post highlights a topic of particular interest to the Frontier Fields project — deep field astronomy.

The production of the “The Incredible Time Machine” video is part of a year-long celebration highlighting 25 years of the Hubble Space Telescope. Because of Hubble, we can see back to hundreds of millions of years after the Big Bang. This particular segment includes more than a half a dozen scientists from all over the country who have used Hubble to look at the universe’s earliest days. It takes you through the history of the Deep Field Program and shows how the addition of new instruments on Hubble throughout the years has furthered our understanding of the universe’s evolution.

For the video, go here:  http://hubble25th.org/video/5

Taking Stock During this Hubble Anniversary Week

This is a big week for the Hubble Space Telescope. Twenty-five years ago, on April 25, 1990, the Hubble Space Telescope was released into orbit from the Space Shuttle Discovery. Astronomers from around the world are taking stock of the amazing achievements of Hubble over the past 25 years: observations that continually challenge our view of our own Solar System, discoveries of extrasolar planetary systems, a more complete view of star and planet formation, understanding how galaxies evolve from just after the Big Bang to the present day, putting constraints on the nature of the enigmatic dark matter, and even helping to discover that the majority of the mass-energy in the universe is in the form of a mysterious repulsive force known as dark energy. To top it all off, thanks in large part to five servicing missions, Hubble is a more powerful telescope today than at any point in its history.

Astronomers are not only celebrating Hubble’s iconic achievements of the past, they are looking forward to what Hubble can accomplish over the next five years. This anniversary week at the Space Telescope Science Institute (STScI) in Baltimore, Md, a symposium is being held called Hubble 2020: Building on 25 Years of Discovery. STScI is the science operations center of the Hubble Space Telescope, so it is a fitting location for astronomers to gather to discuss the past and the future of Hubble science. For the adventurous out there who would like to test and strengthen their astronomy acumen, watch the astronomy symposium online, where astronomers discuss science results with other astronomers.

For other events celebrating Hubble’s 25th anniversary, you can click here.

Hubble Frontier Fields Update

Part of the conversation happening around the past, present, and future science of Hubble focuses on Hubble’s exploration of the deep universe. As it so happens, April 2015 is also the month where the imaging and processing of the Hubble Frontier Fields data are half-way complete. Of course, astronomers will be pouring over the images for years to come — the science results from the Frontier Fields are just beginning.

Shown in the images below are the first three completely imaged Frontier Fields galaxy clusters (Abell 2744, MACS J0416, MACS J0717) and their respective neighboring parallel fields.

Shown here are the first three completed Frontier Fields galaxy clusters and their associated parallel fields.  Labeled, from the top, are galaxy cluster Abell 2744, the neighboring Abell 2744 parallel field, galaxy cluster MACS J0416, the neighboring MACS J0416 parallel field, galaxy cluster MACS J0717, and the neighboring MACS J0717 parallel field.  The MACS J0717 galaxy cluster image and its associated parallel field are still being processed, so we expect another version of these images shortly.

Shown here are the first three completed Frontier Fields galaxy clusters and their associated parallel fields. Labeled, from the top, are galaxy cluster Abell 2744, the neighboring Abell 2744 parallel field, galaxy cluster MACS J0416, the neighboring MACS J0416 parallel field, galaxy cluster MACS J0717, and the neighboring MACS J0717 parallel field. The MACS J0717 galaxy cluster image and its associated parallel field are still being processed, so we expect new versions of these images shortly.
Credit: NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI)

Astronomers are already looking forward to the future of deep-field science. While much of the discussion this week is about Hubble, astronomers generally acknowledge that to truly build off of Hubble’s discoveries, we need the next-generation Great Observatory, the James Webb Space Telescope (JWST). JWST is scheduled to launch in the fall of 2018. I think it goes without saying that the participants of the Hubble 2020 symposium are incredibly excited at the prospect of these two behemoths of science — these machines of discovery —  exploring the universe at the same time.