The Newsletter of the Friends of Palomar Observatory, Vol. 12 No. 1 – April 2017
By Steve Flanders
Stodgy and dated until recently, the Greenway Visitor Center’s exhibition hall has been given a thorough upgrade and modernization. In 2014, the work of Eleanor Helin was celebrated with the installation of the decommissioned 18-inch Schmidt telescope as the centerpiece of the permanent Helin Commemorative Exhibit titled Searching the Sky for Dangerous Neighbors. Sometime later, the Outreach Center began a weekly lecture program—the Greenway Talks Series—that runs on Saturday mornings through the winter months. In November 2015, the Luskin Virtual Presence Kiosk was installed in the Museum as a multimedia center displaying live camera images from the dome of Hale Telescope along with topical videos and slideshows. In addition, ViewSpace has returned to provide visitors with short astronomy themed presentations updated daily from the Space Telescope Science Institute.
The capstone to this project was completed this past January. Having been in place for many years, all of the informational posters lining the walls were removed. In their places, we have installed 30 new posters that detail the key elements of the Observatory’s science mission.
Among the nine subject headings, two headings deal with engineering innovations, five discuss the major elements of the Observatory’s science program, one subject heading titled Palomar Tonight celebrates the various communities that sustain this enterprise; and one further heading on a panel titled The Palomar Mission establishes the tone of the exhibit. Located on the left as you enter the room, this panel sets out the institution’s mission statement and describes the concept underlying the exhibition itself:
The Observatory’s mission is to study the nature of the Universe and humankind’s place in it. This exhibit touches upon various aspects of that mission: the place, the science, the tradition, and the people who have made it special.
These “aspects” are distributed around the Museum’s exhibit space. Between the mission statement to the left and the community acknowledgements on the right, the remaining 28 panels are grouped and color-coded under seven major science and engineering headings. All of the topics on all of the panels are presented in clear, well-ordered text and graphics.
There is, however, a dimension to this exhibit that may not be obvious. At first sight, it may appear as though each of the seven major subjects is treated as a stand-alone unit, internally sufficient and self-contained in itself. But as that may be, a second inspection is warranted nevertheless. Indeed, another look will show that the various topics in the exhibit are linked together in a web of interrelationships. This web reflects the coherence of the Observatory’s mission and a broadly based coherence found in all the work done here since Fritz Zwicky began his scientific investigations with the 18-inch Schmidt telescope in 1936.
An example: Among the seven subjects, two deal with engineering. On the left side of the room, a heading titled Building Palomar occupies three posters. Citing the role played by George Hale and paying particular attention to Mark Serrurier’s design of the truss structure of the telescope tube, this set of posters, the successful completion of the Observatory is presented as the culmination of an extended collaborative effort that brought together the engineering talents of a great many individuals and corporations.
On the other side of the room, five panels are grouped under the subject Technical Innovation. During the 1970’s and after, Jim Gunn and James Westphal developed a detector for the Palomar telescope they called "Four-Shooter." It represents one of the first successful astronomical cameras to use CCD technology and was developed to serve as a prototype for the Hubble Space Telescope’s Wide-Field and Planetary Camera.
As the text points out:
Innovation has been and continues to be central to Palomar’s success as a leading astronomical research center.
Similarly, relationships between topics may be seen across the exhibit. Three science subjects—Calibrating Cosmic Expansion, Cosmic Chemistry and The Hearts of Galaxies—concern cosmology and are connected through the questions we ask about the largest entities and the longest time lines of our Universe.
These subjects bear upon related aspects of the same story and, in that way, together directly speak to the Observatory’s stated mission: We know a good deal about our place in the Universe because, building upon the work of Edwin Hubble, Walter Baade, and Allan Sandage among others, we now are equipped to make measurements of speed and distance that locate us in time and space on a cosmic scale.
We know we inhabit a place in a Universe that not only is expanding but also is evolving. Maarten Schmidt provided evidence of this in his studies of quasars, the extremely luminous objects at the hearts of certain active galaxies we see only in a much earlier era now at very great distances. Not found in the space around us, quasars must therefore be products of the very different conditions that prevailed long ago.
Further, our place in the Universe exists in its familiar form because the diversity of atomic elements in the interstellar medium has grown and evolved. Jesse Greenstein cataloged the elemental composition of stars in our galaxy. Working with Fred Hoyle and Margaret and Geoffrey Burbridge, Willie Fowler drew upon Greenstein’s work to demonstrate that everything in our environment is built from atomic elements synthesized over billions of years through many generations of stars.
Here we see a portion of the web of relationships represented in the exhibit: cosmic chemistry became possible as the debris ejected by the Big Bang cooled sufficiently to form atoms. Over time, great clouds, at first primarily of hydrogen, collapsed to form stars that ended their lives by seeding the Universe with heavy elements and complex molecular structures.
Gerry Neugebauer participated in the NASA working group that cataloged half a million infrared sources using data gathered by the IRAS mission. Among these sources, Neugebauer found young stars surrounded by disks of dust and debris—an early indication of the possible existence of planets in orbit around distant stars.
And on the subject of exoplanets, Caltech astronomer Erik Petigura will describe what we presently know about exoplanets in a talk to be given at the Planetarium at Palomar College on May 6. Further information is found in the accompanying article about this season’s Friends events.
For some time, astronomers have understood that the Sun and all of the components of our Solar System were formed in the gravitational collapse of a cloud of galactic gas and dust. It was cloud well stocked with heavy elements processed and enriched through successive generations of stars. In the same way, the many rock and ice fragments orbiting beyond Neptune are also remnants of that cloud, perhaps so far from the Sun that they remain largely unaltered.
Five panels on the right side of the Museum concern The New Solar System and describe the richer understanding of our Solar System that has resulted in part from discoveries made at Palomar. Several panels focus on a few key individuals who have studied the small-body populations and dynamics, such as asteroid families in the main belt and near Earth, as well those found at great distances in the Kuiper Belt and beyond. Michael Brown has discovered more than a dozen Trans-Neptunian Objects that are now classified as “dwarf planets.” Decades ago, Hubble, Baade, and Sandage were concerned about the size of the Universe and our place in it; now Brown is concerned with the size of our Solar System and, by significantly expanding its boundaries, has at least in some small measure altered the way we understand our place in it.
Eleanor Helin and Gene and Carolyn Shoemaker were concerned with that group of primordial artifacts that orbit the Sun from within the Asteroid Belt between Mars and Jupiter. As is also true of bodies far out in the Kuiper Belt, the asteroids of this region occasionally make close approaches to each other on orbits that may intersect. As a result, trajectories change and things that were once at a safe distance may be thrown into the inner Solar System.
In 1969, Gene Shoemaker began a systematic search for asteroids whose orbits might bring them dangerously near the Earth. He collaborated, first, with Eleanor Helin and later with his wife Carolyn along with several others. The danger represented by such objects was illustrated in 1993 when Carolyn Shoemaker sighted a comet that, just before it collided with Jupiter, was first torn to pieces by tidal forces in the giant planet’s gravitational field.
Gene and Carolyn Shoemaker’s search for near-Earth asteroids constitutes one among a number of sky surveys that have been done at Palomar Observatory using the two wide field telescopes. Indeed, survey work is essential to the science of The New Solar System. And to an equal degree, the three supernova search programs conducted at Palomar between 1935 and 1975 represent the indispensable foundation for at least two of the science topics addressed in the exhibit: first, the science of stellar life cycles and chemical evolution seen in the section titled Cosmic Chemistry and, second, the construction of the cosmic distance ladder as well as the science of dark matter and dark energy seen in the five posters of Calibrating Cosmic Expansion.
We might note that Fritz Zwicky began his work here by conducting a search for supernovae of which he eventually found 120 occurrences. Equally significant, using images acquired in the first Palomar Sky Survey, George Abell produced a catalog of galaxy clusters that for the first time traced the large scale structure of the Universe.
In a substantive manner, the investigations and accomplishments and discoveries seen in the exhibit’s six other science and engineering headings are one way or another all linked by the support of and through a common reliance upon the data and the evidence acquired in surveys. And this idea may be more true now than ever as the science of astronomy generally enters the era of “Big Data” and as Palomar Observatory prepares to launch the Zwicky Transient Facility (ZTF). As it matures, ZTF will go deep into the night sky to generate vast stores of time-domain data. The output of this undertaking will be useful to all the areas of inquiry seen in the exhibit but with particular emphasis upon the high-energy Universe described under the heading Hearts of Galaxies.
It is appropriate then that the last subject heading, Palomar Tonight should bring balance and a sense of perspective to the exhibit. At Palomar, we touch upon many of the most significant questions currently of interest to astronomers and astrophysicists worldwide. Our continued ability to make contributions to that conversation is very much a function of the mutual respect and joint efforts of several communities: astronomers and engineers from Caltech and other institutions who drive forward the various research programs; most particularly, the members of the staff who insure all aspects of the Observatory’s operations; the volunteer docents who communicate to the public their unfettered enthusiasm for this place; and, finally, members of the public who are curious and interested in the work of this venerable institution.
By Andy Boden
2017 will be a big year in the life and legacy of Palomar Observatory. I have previously written in these pages (Big Eye 9-3, 10-1, & 10-2) that the Zwicky Transient Facility (ZTF) is coming to Palomar this year. ZTF is an ambitious new step in night sky reconnaissance undertaken at Palomar, and a broad international partnership in the model of the successful Palomar Transient Factory arc of projects. As I wrote in September 2014, a key partner in ZTF development is the U.S. National Science Foundation (NSF), whose 2014 funding grant to Caltech has enabled the development of an ambitious new camera with a collecting field similar in size to the original Palomar Sky Survey photographic plates. The larger format ZTF camera will be able to survey the Palomar skies much more completely and rapidly than ever before.
The new project is named the Zwicky Transient Facility to recognize the many astrophysical insights and contributions made by Caltech’s Prof. Fritz Zwicky. Over his long career Zwicky contributed to many fields of astronomy and technology, but his seminal vision to bring wide-field sky reconnaissance to Palomar (in conjunction with the Hale Telescope) solidified the Observatory as the dominant astronomical facility in the world for nearly 50 years.
For the past few years the new ZTF camera has been in development at Caltech in Pasadena, and it is nearly ready to make its first trip to Palomar late in the spring. In preparation for the new camera’s arrival (and depicted here), long-planned modifications to the Samuel Oschin Telescope are now well underway. The Oschin Telescope optics have been removed for protection and refurbishment, and the concrete balancing blank has been inserted in their place (see image); the telescope structure is being modified to accommodate the larger and heavier ZTF camera (see image); both the telescope and dome control systems are being upgraded to support ZTF’s higher observation rate; and a new optical element is being added to the “Schmidt corrector” in the front of the telescope to deliver better image quality across the larger field of the new camera. Later this year a new robotic filter exchange mechanism will be added to rapidly switch between survey “colors” (passbands) when the need arises. And other Observatory infrastructure (e.g. the data connection as provided by our UCSD/HPWREN partners) is being upgraded to handle the more data-intensive requirements of ZTF operations.
If all goes according to plan the Samuel Oschin Telescope and ZTF camera will be ready for commissioning in the early fall, and the three-year ZTF survey should start near the end of calendar 2017. With NSF investment in ZTF the entire U.S. astronomy community will be engaged in Palomar science to a much greater degree than ever before. Among the key scientific areas ZTF will target is the emerging field of gravitational wave astronomy (apropos of our July Friends event discussed below in this issue). In particular ZTF is well positioned to search for light from the “afterglows” of gravitational wave events—if found, such light has the potential to teach us much more about these extreme cosmic events. Other items in the ZTF discovery space span a broad spectrum from detecting earth-crossing asteroids in our own solar system, to searching for the optical counterparts to recently discovered and enigmatic “fast radio bursts.”
We at the Observatory are excited to see the years of planning, building, and preparing ZTF finally coming to fruition.
On Saturday, May 6, Erik Petigura, a Hubble Postdoctoral Fellow at Caltech, will be speaking on the subject of “The Prevalence, Properties, and Architectures of Exoplanets.” The talk will be held in the Planetarium at Palomar College in San Marcos.
Exoplanets orbit stars other than our Sun. At first, the study of these objects focused upon individual discoveries. But, thanks in large part to the many identifications made by NASA’s Kepler Mission, the direction of exoplanet research has changed. We now know, Dr. Petigura argues, that planets are common and that nature produces a rich diversity of planetary compositions and orbital architectures.
In this talk Dr. Petigura will present an overview of exoplanet demographics and will describe how this developing field of study may illuminate our understanding of the Earth’s history and the processes that led to development of life.
The event at the Planetarium on May 6 will begin with a reception at 6:30 pm. Dr. Petigura’s talk will start at 7:00 pm after which Mark Lane, director of the Planetarium, will present a sky show. Here are directions to the Planetarium. Please park in the lot across the street from the Planetarium. No RSVP is needed and guests are welcome.
We have a second event scheduled at the Outreach Center for later in the summer. On Saturday, July 22, David Reitze, Research Professor of Physics at Caltech and Executive Director of the LIGO Project will speak on the subject of “Black Holes Last Tango in Space: LIGO and the Dawn of Gravitational-wave Astronomy.”
Dr. Reitze’s presentation will begin at 7:00 pm and afterwards the docents will hold a star party on the basketball court behind the Outreach Center. I will out send a reminder several weeks before July 22.
We also anticipate scheduling a Friends event in the fall but I will need to send an update when plans are more fully settled.
In addition, we will be holding afternoon cookouts on weekends at the Outreach Center following the regular public tours. Burgers and hot dogs and salad and popcorn and a movie—all the members of the Friends of Palomar Observatory are invited and I’ll write to you when we schedule the first one.
- Steve Flanders
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