Hubble's Universe Unfiltered

  • July 21, 2016

    The Final Frontier of the Universe

    by Frank Summers

    [Note: this article is cross-posted on the Frontier Fields blog.]

    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

    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.”

  • June 3, 2016

    Caught in a Gravitational Whirlpool?

    by Frank Summers

    Gravitational lensing by a massive cluster of galaxies produces lots of streaks, arcs, and other distorted shapes. The images of distant galaxies have been transformed when their light passes through the warped space within the galaxy cluster.

    Astronomers know that these distant galaxies, if seen without the intervening cluster, could look like normal galaxies. Or, these galaxies might have strange shapes due to galaxy interactions. Also, since distant galaxies are seen as they were earlier in the universe, some are still developing their shapes.

    This lack of knowledge about the true shape of a galaxy that has been distorted by gravitational lensing makes interpreting their images more difficult. One way to comprehend the distortions is to run a simulation. Take a well-known galaxy, and simulate the distortions that its appearance would undergo via gravitational lensing.

    That process is demonstrated in the video below. The simulation imagines the Whirlpool Galaxy passing behind the massive galaxy cluster Abell 2744. Astronomers in the Frontier Fields project have studied Abell 2744 carefully and have a detailed mass map for the cluster. Using that mass distribution, they can calculate the lensing effects for the simulation. Note that this is just a demonstration of the image distortions due to gravitational lensing. In reality, galaxies don't pass behind clusters at such superluminal speeds, the Whirlpool would appear much smaller, and many other caveats.

    These demonstrations are useful in comprehending the types of image distortions one might see. The really hard task is, however, to take an observed distorted image and try to re-create the actual, undistorted image. I have seen that attempted a couple times with mixed results. Maybe I can find one of those attempts and write that up as another blog post.

    For a another perspective on this video, see this Frontier Fields blog post.

  • May 6, 2016

    Episode 22: Celestial Fireworks

    by Frank Summers

    Download this episode


    Celestial Fireworks

    To help commemorate Hubble's 25th anniversary in April 2015, our imaging team captured an amazing cluster of thousands of massive, hot, bright stars. The brilliance of the cluster inspired the metaphor of "celestial fireworks," celebrating decades of astronomical accomplishments. To make this beautiful image even more eye-popping, our visualization team processed it into a three-dimensional computer model and created a flight into the nebula. In this episode, Dr. Summers explores the spectacular image and reveals behind-the-scenes details of how the visualization was made.


    Hubble Press Release:


    Show Notes:

    • It is remarkable that the Hubble Space Telescope reached the 25 year milestone. However, that doesn't mean the telescope is "old." The five servicing missions to the telescope provided a continuing series of advances in both the observatory hardware and the scientific instruments. In addition, two decades of experience running the observatory have brought about vast improvements in efficiency and yield. In so many ways, Hubble has increased its capabilities over the years and gotten demonstrably better with age. Scientific productivity is perhaps the best measure of the vitality of a telescope, and on that measure Hubble is a robust as it has ever been.


    • A search for the Spitzer Space Telescope image of the nebula Gum 29 finds an object known as RCW 49. They are the same nebula. There are multiple catalogs of nebulae by different astronomers, at different observatories, at different times. Colin Stanley Gum published his study of 84 nebulae in 1955, while the team of Rodgers, Campbell, and Whiteoak (RCW) produced a catalog of 182 objects in 1960. Other catalogs of nebulae include those of Caldwell and Sharpless. A nebula can be referenced by any of these catalog names, or by the more well-known NGC catalog number if such an entry exists. Unfortunately, there is no one standard naming convention, and cross-referencing between catalogs is a standard feature in astronomy.


    • In many of our visualizations, the stars were handled as image cutouts. If there are just a few hundred stars in an image, the process of identifying the pixels associated with each star is not overly cumbersome. Software written for astronomical research addresses such tasks and can be applied to visualization. However, dense star clusters with many thousands of stars present a severe challenge with tremendous overlap amongst the stars. The point-spread function technique, described in the video, is also an adaptation of research software. Although developed specifically for star clusters, the process can be applied to any image.


    • The development of computer graphics software to support Hollywood movies has greatly benefited our work in scientific visualizations. Astronomy is not a large enough market for specialized visualization software to be particularly profitable. Instead, we use the software written for the billion-dollar film market, and adapt it to our purposes. The sophisticated tools for look development, virtual cameras, and image rendering help add a cinematic feel, while we can keep track of the scientific details and ensure the presentation is astronomically appropriate. We strive for a combination of accuracy and aesthetics.


    Image notes

    Zoom to Gum 29 (movie)

    Credit: NASA, ESA, G. Bacon, and Z. Levay (STScI)

    Acknowledgment: A. Fujii, the Digitized Sky Survey 2 (STScI/AURA, Palomar/Caltech, and UKSTU/AAO), ESO, the Hubble Heritage Team (STScI/AURA), A. Nota (ESA/STScI), and the Westerlund 2 Science Team 


    Nebula Gum 29

    Credit: ESO


    Nebula Gum 29, infrared

    Credit: NASA/JPL-Caltech/E. Churchwell (University of Wisconsin)


    Star Cluster Westerlund 2, x-ray

    Credit: NASA/CXC/Univ. de Liège/Y. Naze et al


    Nebula Gum 29 and Star Cluster Westerlund 2

    Credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA), A. Nota (ESA/STScI), and the Westerlund 2 Science Team 


    Flight to Star Cluster Westerlund 2 (movie)

    Credit: NASA, ESA, G. Bacon, L. Frattare, Z. Levay, and F. Summers (Viz3D Team, STScI), and J. Anderson (STScI) 

    Acknowledgment: The Hubble Heritage Team (STScI/AURA), A. Nota (ESA/STScI), the Westerlund 2 Science Team, and ESO

    Music courtesy of Associated Production Music (APM)