Hubble's Universe Unfiltered

  • October 14, 2016

    A Deep View Down Broadway

    by Frank Summers

    [Note: this blog post also appears on the Frontier Fields blog.]

    One of the more philosophical concepts that astronomers have to deal with on an everyday basis is the commingling of space and time in astronomical images.

    The underlying idea is straightforward. The speed of light is finite. Light from a star or nebula or galaxy takes a measurable amount of time to cross the space between it and us. Hence, the light we see now left that object at some previous time. We view astronomical objects as they were in the past. As I like to say, looking out in space is also looking back in time.

    The implications of this maxim are considerable, especially in dealing with the deep field images from Hubble (see the accompanying image of the Abell 2744 Parallel deep field). Such images contain a wonderful assortment of galaxies, with a few stars here and there. Each object is at a different position in space, both in the two-dimensional sense of a different position within the image and in the three-dimensional sense of being at a different distance from Earth. Further, objects at different distances are seen at different times in the past. Hence, astronomers must examine these deep field images in four-dimensional space-time.

    Tackling the expanse of space and time in these images can be mind-boggling. We’ll start with the stars, which are easier to understand. All the stars are local, within our Milky Way galaxy. These stars are generally hundreds to thousands of light-years away. The light we observe today might have left the star while the pyramids of Egypt were being built. Because stars don’t change appreciably on scales of thousands of years, stars in deep fields are just like stars in other astronomical images.

    The galaxies, however, stretch much farther into space. The nearest are many millions of light-years away, while the most distant are around ten billion light-years away. Galaxies don’t change much on million-year timescales. For example, it takes over 200 million years for our Sun to orbit once within our galaxy. Even though the light may have left a galaxy when dinosaurs first started to dominate our planet, the same galaxy would look similar today. Thus, the nearby galaxies in these images are comparable to local galaxies.

    Given billions of years, however, galaxies do change, and these deep field images provide compelling evidence. Distant galaxies do not have the standard spiral and elliptical shapes. They are often elongated, have bright spots of star formation, and are much smaller in size. We see galaxies as they were before the Sun, Earth, and the solar system formed. We study the development of galaxies over time to see how they form and grow. The perplexing point is that, for any given galaxy in the image, there is no distinct visual indicator of its distance in space or time. The layers of the universe are jumbled together across the image, and it is a grand puzzle of cosmology to sort them out.

    The usual method to determine distances, and therefore times, is to measure the cosmological redshift of each galaxy. That concept has been discussed in a Frontier Fields blog post by Dr. Brandon Lawton: “Light Detectives: Using Color to Estimate Distance”. Thus, I’d like to take this essay in a different direction.

    The Manhattan Deep Field

    When discussing the cosmic mixture of space-time with an artist visiting from Spain, I happened upon a novel idea for a human-centric analogy.

    Imagine you are in New York City, specifically Times Square in Manhattan. You look down Broadway to the southern end of the island about 4 miles away. If the speed of light were extremely slow, traveling only one mile per century, what would you see?

    Each mile down Broadway would represent one hundred years of New York’s history. Each block would be 5 to 10 years earlier in the development of the metropolis.

    A quarter of a mile away, the southern end of the theater district would appear as it did in the early 1990s when “Miss Saigon” came to Broadway. Only a few blocks farther would be the disco era and the civil unrest of the 1960s, then the World War II years and the Great Depression.

    The Empire State Building, about a mile away, would vanish, as it was not built until 1931. At a similar distance, Madison Square Garden would be seen hosting heavyweight boxing matches in its original building, before the demolition and re-construction in the late 1920s.

    Progressing another mile down Broadway to Union Square would travel back past the Civil War, Tammany Hall politics, economic growth fostered by the Erie Canal, and Alexander Hamilton’s original run on the New York stage.

    The mile beyond to the Soho district progresses through the times of New York as the capital of the United States, the Revolutionary War, the founding of Columbia University, and the importation of slaves by the Dutch West Indies Company.

    The final mile to Battery Park leads through the colonial era alternately dominated by Dutch or English foreign powers, past the garrison of Fort Amsterdam, to the island’s Native American roots and the initial explorations by Henry Hudson.

    A “slow speed of light” view from Times Square would lay out the entire history of the city of New York in a single view. The comingling of space and time would make it the historian’s exceptional equivalent of the astronomer’s standard observation: a deep view down Broadway.

    This idea of a time-warped view of New York provides an analogy to what Hubble uncovers: the history of galaxies compressed and jumbled within each deep field. Perhaps it can help you to look at these images from that requisite four-dimensional perspective. These deep field images are truly a trip down memory lane.

  • October 7, 2016

    News from the Universe, October 2016

    by Frank Summers

    Each month, I host the Public Lecture Series at the Space Telescope Science Institute in Baltimore, Maryland. Before introducing the main speaker, I present some Hubble discoveries and other astronomical findings and events called "News from the Universe".

    The stories I covered for the October 4, 2016 lecture are:

    -- The detection of possible water plumes on Europa

    -- The end of the Rosetta mission

     

     

    Here are the description and links to the main speaker's presentation for the October 2016 Public Lecture Series:

    A Multi-wavelength View of Stellar Life and Death in M83

    William Blair, Johns Hopkins University

    Although the timescales are long by human standards, galaxies undergo changes as stars are born, grow old, and ultimately die in supernova explosions. While we can't standby and watch these developments take place, we can piece together the processes involved just by looking at carefully selected snapshots in time. Messier 83, the Southern Pinwheel galaxy, is a case in point. This galaxy is home to both significant new star formation and at least 7 supernova explosions in the past 100 years. Both stellar birth and stellar death can be studied, and often require observations in different bands of light with both ground and space-based telescopes. Dr. Blair will describe a multi-year, multi-wavelength study of galaxy M83 that has provided detailed insights about its evolution.

     

    An archive of lecture webcasts back to 2005 is available at STScI Webcasting: STScI Public Lecture Series Archive.

    Most lectures since spring 2014 are also in a HubbleSiteChannel YouTube playlist: STScI Public Lecture Series Playlist

     

  • September 23, 2016

    A Hubble Journey from IMAX to 4K UHD

    by Frank Summers

    Way back in 2003, I had a summer intern who demonstrated an abundance of enthusiasm and gumption. As befits such passion, I assigned him a particularly ambitious project: attempt to extract thousands of individual galaxy images from a Hubble image with hundreds of millions of pixels. His excellent work showed that the project was indeed feasible, and that a spectacular visualization could be made with the resulting data set. We also learned that the video resolution of the time (640x480 pixels) was entirely inadequate to handle such high-resolution imagery.

    Thus, in the fall, we embarked on an even more ambitious project: an IMAX short film called "Hubble: Galaxies Across Space and Time." We improved and repeated the galaxy image extraction process on the final image data from the Great Observatories Origins Deep Survey (GOODS), a mosaic of more than 600 megapixels. From the roughly 30 thousand sources in the images, we crunched more than 10 thousand individual galaxies through the production pipeline. The resulting galaxy images, along with distances measured by the GOODS team, enabled us to create a 3D model of the galaxy distribution.

    A flight through this data set provides a visual experience of the changes in galaxies across the cosmos. In addition, because light takes billions of years to cross the intervening space, the distant galaxies are seen as they were when the light left them, billions of years ago. Thus, the journey is both across space and back in time.

     

     

    We were tremendously pleased with the result. Our small team, using 100% Hubble images and data, was able to produce a compelling visualization on the largest of screens. When it premiered at the Maryland Science Center in April 2004, I felt an awe-inspiring, "floating through the universe" immersion that was unlike anything I'd experienced before. Fortunately, folks who are not astronomy geeks were also impressed; the film won the Large Format Cinema Association's "Best Short Film" award in 2004.

    I have since shown this film in talks hundreds of times, but always with the disclaimer that it is "just so much better at full resolution." Well, today that changes. Today, we are releasing the film at 4K Ultra High Definition (UHD) resolution (3840 x 2160 pixels) on our HubbleSiteChannel on YouTube with movie file downloads available on the HubbleSite Videos page. This UHD version of the film has about 70% of the width of the master frames used to create the IMAX film prints. It is necessarily cropped in height to fit the now-standard 16x9 aspect ratio (the master frames are closer to the old standard 4x3 aspect ratio). Most importantly, this high-resolution format has 27 times as many pixels as the 640x480 resolution format we released to the public in 2004.

    Watching the film on a large screen at full 4K UHD is the first time I've approached the theater experience. The level of detail and the resulting feel of depth within the galaxy collection pull me into the scene that much more. After all the time spent processing the images, building the 3D models, and choreographing the camera, it is an absolutely wonderful surprise when I can still see something new in the end product. Although this film was completed more than a decade ago, the new technology has brought renewed enthusiasm about the possibilities for these cosmic visual explorations. What more might we do with the current, larger Hubble cosmology projects? We have even created a 6K UHD resolution (5760 x 3240 pixels) version of this film for the NASA Hyperwall that I'm just dying to try out at Goddard Space Flight Center.

    Our team has produced several other 4K UHD visualizations, and will continue to work on new ones. For more, check our Ultra HD Astronomy Visualizations playlist on YouTube or utilize the 4K-UHD Video tag on HubbleSite.