It Takes a Team

There is no denying that the history we tell about science is full of achievements often credited to individual efforts.  The reality, of course, is that scientific achievements are not done alone or in intellectual vacuums.

Standing on the Shoulders of Giants

Astronomer Edwin Hubble, for example, built upon the ideas of other astronomers when he made his landmark discovery in 1923 that the faint spiral nebulae observed in the sky were actually other galaxies outside our Milky Way.  This surprising finding greatly expanded our understanding of the size of the universe.

Still from Hubblecast episode 89: Edwin Hubble

This is a still image from Hubblecast 89, which talks about the life of Edwin Hubble.  Credit: NASA & ESA

Before Hubble’s discovery, scientists were embroiled in a fierce debate about the nature of these nebulae.  Some, most prominently astronomer Harlow Shapley, believed that these nebulae were parts of our own Milky Way galaxy.  Others, like Heber Curtis, posited that the Milky Way galaxy was smaller than suggested by Harlow Shapley, and these nebulae were likely entire galaxies outside of the Milky Way.  This scientific disagreement was brought to the fore during a public debate between Curtis and Shapley in 1920.

It was not until 1923 when Edwin Hubble observed a cepheid variable star in one such nebulae that the debate was quickly settled.  Hubble determined that the cepheid variable he was observing was very far away – much too far away to be a part of the Milky Way galaxy.  In fact, he had discovered the variable star resided in what we now know to be our neighboring Andromeda galaxy.  This put to rest the debate vociferously argued by Shapley and Curtis.

Cepheid variable stars are stars whose intrinsic brightnesses change with time by a known amount. This makes them great “standard candles” to calculate their distances.  If you know you are observing a 60-watt light bulb, you can calculate the distance to the light bulb based on the amount of light you observe – the  fainter the 60-watt light bulb appears, the farther away it is.

The key to Hubble’s discovery was the knowledge that we could determine a cepheid variable’s intrinsic brightness based off of its observed periodicity, which is the amount of time the variable star takes to go from maximum brightness to minimum brightness and back to maximum brightness.  Hubble could not make his discovery without this background information, which, as it turns out, was first published in 1912 by astronomer Henrietta Swan Leavitt.  Henrietta was not given proper credit for this monumental discovery at the time, but there is now no doubt that her efforts paved the way for our modern understanding of stars and distances in the cosmos.

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Picture of astronomer Henrietta Swan Leavitt taken before 1921.

Astronomy, like all sciences, is dependent on building upon our scaffolded knowledge to further our understanding into new realms of the unknown.  It also depends upon teams of dedicated individuals working together.  Edwin Hubble, a premiere astronomer of the early 20th century, built upon the discoveries of prior scientists and engineers.  He also depended upon the support of his assistant and the staff of the Mt. Wilson Observatory, where he conducted many of his observations.

The Frontier Fields: A Team of Professionals Building Upon the Successes of Prior Programs

Today, astronomy is increasingly relying on larger projects that require teams of men and women with diverse skill sets, including the Hubble Frontier Fields program.  Frontier Fields was conceived following the successes of prior Hubble deep-field programs.  These include the Hubble Deep Field, Hubble Ultra Deep Field, CANDELS, and in particular, CLASH – which helped build our understanding of gravitational lensing around galaxy clusters.  The general Frontier Fields program also both benefited from, and enhanced, our understanding of mathematical models that predict how light from distant galaxies will be lensed by foreground massive clusters.  Of course, all of the deep-field studies are possible because of the work of prior luminaries such as Edwin Hubble, Henrietta Leavitt, and Albert Einstein.

In July 2016, the Hubble Frontier Fields team was given the AURA team award.  AURA – the Association of Universities for Research in Astronomy – operates the Space Telescope Science Institute (STScI – the science operations center for Hubble) for NASA.

"The STScI Frontier Fields team receives the 2016 AURA team award for its
unparalleled efforts in implementing the Hubble Frontier Fields Director's
Discretionary program and providing rapid [astronomical] community access to
high-level data products generated from the observations." - AURA

The full list of recipients of the AURA award can be found by clicking the link below.

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2016 AURA Team  Award - STScI Frontier Fields

Some of the recipients of the 2016 AURA team award.  The team received the award in July 2016 for the Hubble Frontier Fields program, which began in 2013.  Credit: P. Jeffries/STScI.

In addition to the awardees, there is also support from the STScI directorate (Ken Sembach and Neill Reid).

It should be noted that the NASA Frontier Fields program is bigger than just the core Hubble Frontier Fields program at STScI.  There are also teams of people working with NASA’s other Great Observatories, the Chandra X-ray Observatory and the Spitzer Space Telescope, to acquire images of these fields in invisible X-ray and infrared light.  There are teams of astronomers proposing for follow-up observations of the Frontier Fields using many ground-based observatories in radio, millimeter, infrared, and visible light.  In addition, there are the astronomers and mathematical modelers who are taking this publicly available data and using it to broaden our understanding of the physics of the cosmos.

Science truly is a team sport.

Beyond the Frontier Fields: How JWST Will Push the Science to a New Frontier

The Frontier Fields Project has been an ambitious campaign to see deep into our universe. Gravitational lensing, as used by the Frontier Fields Project, enables Hubble to see fainter and more-distant galaxies than would otherwise be possible. These images push to the very limits of how deeply Hubble can see out into space.

Hubble, Spitzer, Chandra, and other observatories are doing cutting-edge science through the Frontier Fields Project, but there’s a challenge. Even though leveraging gravitational lensing has allowed astronomers to see objects that otherwise could not be detected with today’s telescopes, the technique still isn’t enough to see the most distant galaxies. As the universe expands, light gets stretched into longer and longer wavelengths, beyond the visible and near-infrared wavelengths Hubble can detect. To see the most distant galaxies, one needs a space telescope with Hubble’s keen resolution, but at infrared wavelengths.

That infrared telescope is the James Webb Space Telescope, slated to launch in October 2018. It has a mirror 6.5 meters (21 feet) across, can observe wavelengths up to 10 times longer than Hubble can observe, and is the mission that will detect and study the first appearances of galaxies in the universe.full_jwst_hst_mirror_comparison

Figure 1: Webb will have a 6.5-meter-diameter primary mirror, which would give it a significant larger collecting area than the mirrors available on the current generation of space telescopes. Hubble’s mirror is a much smaller 2.4 meters in diameter, and its corresponding collecting area is 4.5 square meters, giving Webb around seven times more collecting area! Webb’s field of view is more than 15 times larger than the NICMOS near-infrared camera on Hubble. It also will have significantly better spatial resolution than is available with the infrared Spitzer Space Telescope. Credit: NASA. http://webbtelescope.org/gallery

Observations of the early universe are still incomplete. To build the full cosmological history of our universe, we need to see how the first stars and galaxies formed, and how those galaxies evolved into the grand structures we see today.

 

Looking back in time to the first light in the universe:

Astronomers use light to explore the universe, but there are pieces of our universe’s early history where there wasn’t much light. The era of the universe called the “Dark Ages” is as mysterious as its name implies. Shortly after the Big Bang, our universe was filled with glowing plasma, or ionized gas. As the universe cooled and expanded, electrons and protons began to bind together to form neutral hydrogen atoms (one proton and one electron each). The last of the light from the Big Bang escaped (becoming what we now detect as the Cosmic Microwave Background). The universe would have been a dark place, with no sources of light to reveal this cooling, neutral hydrogen gas.

Some of that gas would have begun coalescing into dense clumps, pulled together by gravity. As these clumps grew larger, they would become stars and eventually galaxies. Slowly, starlight would begin to shine in the universe. Eventually, as the early stars grew in numbers and brightness, they would have emitted enough ultraviolet light to “reionize” the universe by stripping electrons off neutral hydrogen atoms, leaving behind individual protons. This process created a hot plasma of free electrons and protons. At this point, the light from star and galaxy formation could travel freely across space and illuminate the universe. It is important to note here, astronomers are currently unsure whether the energy responsible for reionization came from stars in the early-forming galaxies; rather, it might have come from hot gas surrounding massive black holes or some even more exotic source such as decaying dark matter.

The universe’s first stars, believed to be 30 to 300 times as massive as our Sun and millions of times as bright, would have burned for only a few million years before dying in tremendous explosions, or “supernovae.” These explosions spewed the recently manufactured chemical elements of stars outward into the universe before the expiring stars collapsed into black holes.

Astronomers know the universe became reionized because when they look back at quasars — incredibly bright objects thought to be powered by supermassive black holes — in the distant universe, they don’t see the dimming of their light that would occur if the light passed through a fog of neutral hydrogen gas. While they find clouds of neutral hydrogen gas, they see almost no signs of neutral hydrogen gas in the matter located in the space between galaxies. This means that at some point the matter was reionized. Exactly when this occurred is one of the questions Webb will help answer, by looking for glimpses of very distant objects still dimmed by neutral hydrogen gas.

Much remains to be uncovered about the time of reionization. The universe right after the Big Bang would have consisted of hydrogen, helium, and a small amount of lithium. But the stars we see today also contain heavier elements — elements that are created inside stars. So how did those first stars form from such limited ingredients? Webb may not be able to see the very first stars of the Dark Ages, but it’ll witness the generation of stars immediately following, and analyze the kinds of materials they contain.

Webb’s ability to see the infrared light from the most distant objects in the universe will allow it to truly identify the sources that gave rise to reionization. For the first time, we will be able to see the stars and quasars that unleashed enough energy to illuminate the universe again.

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Figure 2: JWST will be able to see back to when the first bright objects (stars and galaxies) were forming in the early universe. Credit: STScI. http://jwst.nasa.gov/firstlight.html

 

Early Galaxies:

Webb will also show us how early galaxies formed from those first clumps of stars. Scientists suspect the black holes born from the explosions of the earliest stars (supernovae) devoured gas and stars around them, becoming the extremely bright objects called “mini-quasars.” The mini-quasars, in turn, may have grown and merged to become the huge black holes found in the centers of present-day galaxies. Webb will try to find and understand these supernovae and mini-quasars to put theories of early galaxy formation to the test. Do all early galaxies have these mini-quasars or only some? These regions give off infrared light as the gas around them cools, allowing Webb to glean information about how mini-quasars in the early universe work — how hot they are, for instance, and how dense.

Webb will show us whether the first galaxies formed along lines and webs of dark matter, as expected, and when. Right now we know the first galaxies formed anywhere from 378,000 years to 1 billion years after the Big Bang. Many models have been created to explain which era gave rise to galaxies, but Webb will pinpoint the precise time period.

Hubble is known for its deep-field images, which capture slices of the universe throughout time. But these images stop at the point beyond which Hubble’s vision cannot reach. Webb will fill in the gaps in these images, extending them back to the Dark Ages. Working together, Hubble and Webb will help us visualize much more of the universe than we ever have before, creating for us an unprecedented picture that stretches from the current day to the beginning of the recognizable universe.

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Figure 3: This illustration shows the cold side of the Webb telescope, where the mirrors and instruments are positioned. Credit: Northrop Grumman. http://webbtelescope.org/gallery

 

Resources:

https://frontierfields.org/2016/07/21/the-final-frontier-of-the-universe/

http://hubble25th.org/science/8

http://webbtelescope.org/article/13

The Final Frontier of the Universe

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

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Gravitational lensing in galaxy cluster Abell S1063 Credit: NASA, ESA, and J. Lotz (STScI)

Fifty years ago, in 1966, the Star Trek television series debuted. Given the incredible longevity of the franchise, it seems remarkable that the original television series only lasted three seasons.

Each episode famously began with the words “Space: the final frontier.” To me, those thoughts evoke an idea of staring into the night sky and yearning to know what is out there. They succinctly capture an innate desire for exploration, adventure, and understanding. Such passions are the same ones that drive astronomers to decipher the universe through science.

While Captain Kirk and company could make a physical voyage into interstellar space, our technology has (so far) only taken humans to the Moon and sent our probes across the solar system. For the rest of the cosmos, we must embark on an intellectual journey. Telescopes like Hubble are the vehicles that bring the universe to us.

To explore remote destinations, the Enterprise relied upon a faster-than-light warp drive. Astronomy, in turn, can take advantage of gravitational warps in space-time to boost the light of distant galaxies. Large clusters of galaxies are so massive that, under the dictates of general relativity, they warp the space around them. Light that travels through that warped space is redirected, distorted, and amplified by this “gravitational lensing.”

Gravitational lensing enables Hubble to see fainter and more-distant galaxies than would otherwise be possible. It is the essential “warp factor” that motivates the Frontier Fields project, one of the largest Hubble observation programs ever. The “frontier” in the name of the project reflects that these images will push to the very limits of how deeply Hubble can see out into space.

But is this the “final frontier” of astronomy? Not yet.

Abell S1063 Parallel Field - This deep galaxy image is of a random field located near the galaxy cluster Abell S1063. As part of the Frontier Fields Project, while one of Hubble's instruments was observing the cluster, another instrument observed this field in parallel. These deep fields provide invaluable images and statistics about galaxies stretching toward the edge of the observable universe.

Abell S1063 Parallel Field – This deep galaxy image is of a random field located near the galaxy cluster Abell S1063. As part of the Frontier Fields Project, while one of Hubble’s instruments was observing the cluster, another instrument observed this field in parallel. These deep fields provide invaluable images and statistics about galaxies stretching toward the edge of the observable universe.

The expanding universe stretches the light that travels across it. Light from very distant galaxies travels across the expanding universe for so long that it becomes stretched beyond the visible and near-infrared wavelengths Hubble can detect. To see the most distant galaxies, one needs a space telescope with Hubble’s keen resolution, but at infrared wavelengths.

In what may have been an homage to the Star Trek television series with Captain Picard, the project for such a telescope was originally called the “Next Generation Space Telescope.” Today we know it as the James Webb Space Telescope, and it is slated to launch in October 2018. Webb has a mirror 6.5 meters (21 feet) across, can observe wavelengths up to ten times longer than Hubble can observe, and is the mission that will detect and study the first appearances of galaxies in the universe.

In the Star Trek adventures, Federation starships explore our galaxy, and much of that only within our local quadrant. Astronomical observatories do the same for scientific studies of planets, stars, and nebulae in our Milky Way; and go beyond to galaxies across millions and billions of light-years of space. Telescopes like Hubble and Webb carry that investigation yet further, past giant clusters of galaxies, and out to the deepest reaches of the cosmos. With deference to Gene Roddenberry, one might say “Space telescopes: the final frontier of the universe.”

Telescopes Team up to View Cosmic Collisions

NASA’s Frontier Fields is a program to capture new deep-field images across the electromagnetic spectrum, from X-rays to infrared light.  NASA’s Great Observatories — the Hubble Space Telescope, Chandra X-ray Observatory, and Spitzer Space Telescope — are taking the lead on this ambitious effort. Other observatories around the world, including the Jansky Very Large Array (JVLA) in New Mexico, which observes radio light, also contribute considerable time to observing the new deep fields.

A new Frontier Fields release from the Chandra X-ray Center highlights the energetic chaos that occurs when massive galaxy clusters collide. The two new images combine data from the Chandra X-ray Observatory, the Hubble Space Telescope, and the JVLA radio dishes. Astronomers are interested in understanding how merging galaxy clusters grow with time and what happens to the galaxies, their gas, and the associated, enigmatic dark matter.

The images of these galaxy clusters (MACS J0416 and MACS J0717) are described below. Read the full release from the Chandra X-ray Center here.

MACS J0416

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The galaxy cluster MACS J0416 seen in X-rays (blue), visible light (red, green, and blue), and radio light (pink), taken by the Chandra X-ray Observatory, Hubble Space Telescope, and Jansky Very Large Array, respectively.  Credit: X-ray: NASA/CXC/SAO/G. Ogrean et al.; Optical: NASA/STScI; Radio: NRAO/AUI/NSF.

The object known as MACS J0416 is actually composed of two clusters of galaxies that will eventually merge to create a single larger massive galaxy cluster.  The image of MACS J0416 contains Chandra X-ray data (blue), Hubble Space Telescope data (red, green, and blue), and a halo of radio light imaged by the JVLA (pink).

According to a paper published in The Astrophysical Journal, the cores of the two galaxy clusters have likely not passed through each other yet, indicating an early phase of their merger.

Astronomers discovered this by studying the cluster’s appearance in visible and X-ray light.  Hubble’s visible-light images show both the galaxies themselves and their gravitational lensing effects, helping us pinpoint the location of dark matter in the cluster. X-ray observations from Chandra show us the location of the heated gas. In MACS J0416, the galaxies and their dark matter are still lined up with the heated gas, meaning their merger has not progressed very far yet. In other observations of merging galaxy clusters, such as the Bullet Cluster, gas heated by the shock of collision eventually separates from the dark matter.

MACS J0717

Galaxy cluster MACS J0717.5+3745 with dark matter map

The galaxy cluster MACS J0717 seen in X-rays (blue), visible light (red, green, and blue), and radio light (pink), taken by the Chandra X-ray Observatory, Hubble Space Telescope, and Jansky Very Large Array, respectively.  Credit: X-ray: NASA/CXC/SAO/G. Ogrean et al.; Optical: NASA/STScI; Radio: NRAO/AUI/NSF.

The massive galaxy cluster MACS J0717 results from a merger of four clusters of galaxies. The image of MACS J0717 contains Chandra X-ray data (blue), Hubble Space Telescope data (red, green, and blue), and JVLA radio data (pink).  Unlike MACS J0416, MACS J0717 appears to have been merging for quite some time. The evidence of merging includes the separated knots of X-rays (blue) formed by the collision of high concentrations of gas, and the giant arcs of radio emission (pink) stretched and distorted by the merger.

MACS J0717 is also the largest known cosmic lens, and thus a prime candidate for observing distant objects magnified by gravitational lensing. The galaxy clusters in MACS J0717 are still merging and are not yet confined to a smaller area — leaving a large total mass over a relatively large area of the sky. This large gravitational lens can magnify and uncover galaxies of the early universe, a key goal of the Frontier Fields project.

Often, observations of these distant, young galaxies only capture the brightest objects. But observations of MACS J0717 demonstrate how Frontier Fields can be used to view some of the universe’s more ordinary early galaxies. In a paper published in The Astrophysical Journal, astronomers discovered seven gravitationally lensed radio sources in MACS J0717. Many of these galaxies would not be observable without the benefit of magnification due to gravitational lensing. The gravitational lensing of massive clusters in radio waves provides a new view of these radio sources, which are thought to be common — but not well-studied — star-forming galaxies in the early universe.

Hubble has also observed distant galaxies using gravitational lensing.  An example is noted here. By using a combination of telescopes, and a combination of different wavelength observations, the Frontier Fields project is providing a broader and deeper view into the galaxies of the early universe.

The Whirlpool Galaxy Seen Through a Cosmic Lens

The Frontier Fields images, while beautiful, aren’t all that easy to comprehend to eyes outside the astronomy community. Look at them and you see streaks of light and blurry smudges mixed into a field of obvious galaxies. It can be difficult to interpret the distortions that occur as light from distant galaxies becomes magnified and bent by the vast mass of the Frontier Fields’ galactic clusters.

So here’s an interesting thought experiment. What if we could take a well-known galaxy and put it behind one of our Frontier Fields galaxy clusters? What would that look like?

Thanks to Dr. Rachael Livermore of the University of Texas at Austin and Dr. Frank Summers of the Space Telescope Science Institute, you can see for yourself. In this video simulation, the Whirlpool Galaxy, also known as M51, sweeps behind the Frontier Fields galaxy cluster Abell 2744. As it moves, the gravity of the galaxy cluster distorts the light of the Whirlpool, warping and magnifying and even multiplying its image.

Obviously, this isn’t a realistic video — galaxies don’t just take jaunts through the cosmos. But it illustrates how our image of the Whirlpool would change depending on where it was placed behind the galaxy cluster. Livermore used the Whirlpool Galaxy for this video because it’s a well-known, popular Hubble image, easily recognizable through the distortions that happen at different locations in the lensing cluster.

Take a look. After the intro, the image on the left of the dotted line shows the location of the Whirlpool behind the cluster, while the image on the right shows the lensing distortion underway.

In this simulation, we’ve moved the Whirlpool to a distance astronomers refer to as redshift 2. That far back, it would be so distant that the light we’re seeing from it would have started traveling away from the galaxy when the universe was just a quarter of its current age. If the Whirlpool were that far away in real life, its light would take 10 billion years to reach Earth.

Note that this isn’t how the Whirlpool would really appear at that distance. At such a distance, all we would be able to make out is the vivid central bulge of stars. But for the purpose of this illustration, the whole galaxy has been kept artificially bright.

The most impressive distortions occur as the Whirlpool passes behind the center of the galaxy cluster, with multiple, stretched, distorted images of the galaxy appearing. At this point, the light of the Whirlpool beaming toward Earth bends to go around the cluster, but can go either left or right. There’s no preference, so some of it goes one way, and some goes another, and we get many images of the same galaxy.

This location is ideal for astronomers, because as you can see in this illustration, the images become both stretched and magnified, allowing the galaxy structure to be seen in greater detail. Furthermore, because a gravitational lens acts much as a telescope lens, more light is focused our way, making the galaxies brighter.

This, Livermore notes, is a primary reason why astronomers are interested in these galaxy clusters – the chance to see the distant background galaxies in so much greater detail than Hubble would be able to produce on its own.

 

 

 

 

 

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.”

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A Century Later, General Relativity is Still Making Waves

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

In November 1915, Albert Einstein published a series of papers that laid out the ideas, equations, and some astronomical applications of the general theory of relativity. While Isaac Newton described gravity as a force between two massive bodies, Einstein’s general relativity re-interprets gravity as a geometric distortion of space and time (see my previous blog post “Einstein’s Crazy Idea” ).

One example cited in those papers was that general relativity can explain the extra precession of Mercury’s orbit that Newton’s formulation does not explain. Another prediction, the bending of light as it passes a massive object, was tested and shown accurate less than four years later. This effect, called gravitational lensing has been shown in tremendous detail by the Hubble Space Telescope (see my previous blog post “Visual “Proof” of General Relativity“), and is one of the prime motivations behind the Frontier Fields project.

Last year, scientists celebrated the centennial of general relativity. The theory has been a resounding success in diverse astronomical situations. However, there was one major prediction that had not yet been tested: gravitational waves.

General relativity predicts that mass not only can create distortions in space-time, but also can create waves of those distortions propagating across space-time. In cosmology, the global expansion of space over time is a familiar concept. For a gravitational wave, space also stretches / shrinks, but that localized distortion moves across space at the speed of light.

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The Laser Interferometer Gravitational-Wave Observatory (LIGO) is one of the projects designed to observe the minute distortions of gravitational waves. It consists of two detectors, one in Hanford, WA, and one in Livingston, LA. Each detector has two perpendicular arms, consisting of ultra-high-vacuum chambers four kilometers (two and a half miles) in length.

For the experiment, a laser light source is split and sent down and back each arm. By measuring how the laser light signals interfere with each other when recombined, extremely precise measurements of any change in distances can be made. The idea is that when a gravitational wave passes by, the minuscule stretch of one arm and shrink of the other will be observable.

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The signal observed in the LIGO event GW150914

On September 14, 2015, both LIGO detectors observed an event (see the accompanying image). The pattern in the signal indicates that a series of gravitational waves passed through the detectors in about two-tenths of a second. It is extremely important that multiple detectors saw the same event so that local disturbances can be ruled out. Plus, the time delay between the detectors helps measure the speed of the waves.

To analyze the event, the LIGO team used computer simulations. The shape and duration of the event waveform matched that expected for the merger of two black holes. The amplitude of the detection helped determine how far away the black-hole merger took place. The best fit is a merger of a 36-solar-mass black hole with a 29-solar-mass black hole to form a 62-solar-mass black hole, about 1.3 billion light-years away.

The energetics of the merger are simply astounding.Recognizing that 36 + 29 = 65, one can see that three solar masses of material did not end up in the resulting black hole. Instead, it was converted in the energy that created the gravitational wave. Released in less than half a second, the peak wattage of the event was greater than the visible light wattage from all the stars in the observable universe.

And yet, when detected on Earth, the measured space distortion was smaller than the size of a proton. The reason it took a century to find gravitational waves is because one has to measure subatomic displacements. Gravity is demonstrably the weakest of the four fundamental forces. It takes a tremendous amount of energy to produces a gravitational wave that can be seen at cosmic distances.

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There are several major results from this observation. The detection shows, for the first time, that both black-hole mergers and gravitational waves exist. The time delay between detectors, and analysis of the signal at different frequencies, demonstrates that gravitational waves travel at the speed of light. All the results are consistent with the predictions of general relativity.

This event marks the beginning of gravitational-wave astronomy. With more detectors coming online and planned improvements to current detectors, the field is burgeoning. Dozens to thousands of black-hole or neutron-star mergers, with more detail about each event, should be found in the next decade.

More than a billion years ago, two black holes merged in a distant galaxy, emitted a tremendous amount of energy, and created a gravitational ripple moving across space. Recently, the LIGO project detected this almost infinitesimal motion of space; a deviation much smaller than the size of an atom. With that amazing observation, the last major prediction of general relativity was verified. A century later, Einstein still rules.

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

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: https://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.