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Space Topics: Planetary AnalogsStars Above, Earth BelowAstronomy and Space Exploration in America's National Parks
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The Milky Way over Bryce Canyon National Park
My flashlight illuminates my path as I hike down the Navajo Loop into Bryce Canyon at night. Jupiter shines brightly just beneath the center of the Milky Way in Sagittarius. Credit: Tyler Nordgren |
by Tyler
Nordgren
June 22, 2008
Starry Sky National Park
“The night sky is the world’s largest national park with its
beauty available to anyone who steps outside and looks up.”
– Geoff Chester, U.S. Naval Observatory
Bryce Canyon National Park, Utah -- Are we alone? What is our
place in the universe? Where did we come from as a planet full of life
with inhabitants able to ask these questions? These are some of the questions
astronomy has sought to answer since the first person looked into the night
sky and wondered about the heavens.
In December 1990 the Galileo spacecraft passed Earth en route to Jupiter. After its launch from the space shuttle Atlantis, it was forced to fly by Venus once and Earth twice in order to build up the necessary speed for its rendezvous with Jupiter and its moons. Here was a spacecraft designed to explore a new planetary system and surely one of the questions it would ask is whether or not there was life there. Now while there were very few astronomers expecting to find life floating in the atmosphere of Jupiter (although Carl Sagan and my graduate advisor Ed Salpeter had published a paper in 1976 describing what such life could be like) it was important to know if any lack of finding it in the Jovian system was due to Jupiter and its moons or to our spacecraft. Anyone attempting to say anything about the absence of life on the ice-covered ocean world Europa had better be able to show that Galileo could find signs of life on Earth, where we are pretty sure life is ample. Therefore, as Galileo flew by Earth for the first of two passes, its instruments were turned on, pointed home, and Carl and his collaborators asked, “Is there life on Earth?”
Earth from Galileo
These images were taken during Galileo's first Earth flyby. In each frame, the continent of Antarctica is visible at the bottom of the globe. South America may be seen in the first frame (top left), the great Pacific Ocean in the second (bottom left), India at the top and Australia to the right in the third (top right), and Africa in the fourth (bottom right). The images were taken at six-hour intervals on December 11, 1990, at a range of between 2 and 2.7 million kilometers (1.2 to 1.7 million miles). Credit: JPL / NASA |
Earth's night side
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Earth's night side (annotated)
Rosetta's OSIRIS wide-angle camera opened the shutter for five seconds to capture this view of nighttime over the Indian Ocean; the night side of Earth is peppered with bright lights from cities. The view is primarily of the northern hemisphere, with India at the center. Eastern Africa is at lower left; almost all of Europe is visible to the upper left, and almost all of eastern Asia to the upper right. The view is cut off becuase the long exposure saturated the sunlit crescent of Earth to the south. The photo was taken about two hours before Rosetta's closest approach, at 18:45 UTC on November 13, 2007. Credit: ESA © 2005 MPS for OSIRIS Team MPS / UPD / LAM / IAA / RSSD / INTA / UPM / DASP / IDA |
From a distance of 960 kilometers, life on Earth is betrayed to a passing planetary probe not by our engineering, but by our chemistry. Galileo’s instruments showed a world rich in water (in all three of its phases) and having an atmosphere containing both oxygen and methane. Left to its own devices, neither gas should remain for very long. Oxygen should oxidize the surface and methane should get broken down by the Sun's ultraviolet rays into water and carbon dioxide. In addition, Galileo observed the land areas to be dominated by a pigment highly absorptive in the red part of the spectrum, reflective in the green, and possessing a spectral profile unlike any known mineral. Carl and collaborators concluded in their 1993 Nature paper: “The identification of molecules profoundly out of thermodynamic equilibrium, unexplained by any non-biological process; widespread pigments that cannot be understood by geochemical processes… are together evidence of life on Earth without any a priori assumptions about its chemistry [i.e., without regards to life as we know it].”
In 2007 the European Space Agency’s Rosetta spacecraft passed by Earth on its way to a comet. And just as Galileo had done in 1990, Rosetta too turned on its instruments as it flew by Earth and this time anyone asking if there was life on Earth had a much easier time finding an answer. For Rosetta flew by the night side of Earth.
There in its cameras at a distance of 80,000 kilometers above the Indian Ocean it caught city lights from London to Singapore. No wonder that visitors from all over the world marvel at what they can see the nighttime sky of America’s parks, far from the bright city lights of home.
Bryce Canyon sits in the heart of southern Utah’s starry-sky and geologic wonderland and hosts the most organized night sky interpretation programs of any national park. Permanent and seasonal rangers give multiple astronomy talks, often two a night on topics ranging from the beauty of a dark starry sky to black holes and general relativity. And when the talks are done, visitors are led over to a “telescope field” behind the visitor center where volunteers set up three or more telescopes of differing sizes to entertain and educate the crowds of stargazers until the last family goes back to their campsite for the night.
In addition, this week sees the 8th annual Bryce Canyon Astronomy Festival. This four-day astronomy extravaganza draws visitors from all over the world. Guest speakers this year range from me (June 26, Bryce Canyon Lodge at 9:30pm) to NASA astronaut Story Musgrave, who was responsible for one of the major Space Shuttle servicing missions to the Hubble Space Telescope. There are also model rocket building workshops and a scale model solar system walk during the day, complemented by constellation shows and a vast field of telescopes at night, courtesy of the Salt Lake Astronomical Society. The festival is instead intended for the general public as a way of emphatically expressing the fact that the wonders of Bryce Canyon National Park, and indeed, of the entire park system, don’t end at sunset, and that the beauty the park service is sworn to protect isn’t found exclusively below the horizon.
Light pollution in Utah
The skies above Bryce Canyon National Park currently sit amid a vast dark region extending between the giant cities of Phoenix, Arizona; Salt Lake City, Utah; and Las Vegas, Nevada. Credit: Chad Moore |
Protection is key to the National Parks Service’s mission. In its founding charter the U.S. park service is been mandated by U.S. Congress “to conserve the scenery, the natural and historic objects and the wild life therein and to provide for the enjoyment of the same in such manner and by such means as will leave them unimpaired for the enjoyment of future generations....” An effort is being made within the park service to increase the definition of “scenery” to include natural “lightscapes.” This is defined by the park service as, “a place or environment characterized by the natural rhythm of the Sun and Moon cycles, clean air, and of dark nights unperturbed by artificial light. Natural lightscapes, including dark night skies, are not only a resource unto themselves, but are an integral component of countless park experiences.” The artificial light within this definition has come to be called light pollution. It’s why you’ve probably never seen the Milky Way from your home. You and 60% of the rest of America.
An architect I once had the pleasure of working with designed an astronomy deck for my university and then surrounded it with upward shining lights. When I pointed this out to him he asked, “What do astronomers need to see the stars for any more, isn’t that why you have the Hubble Space Telescope?”
We astronomers are lucky. The Hubble Space Telescope has captured the public’s imagination and affection (much like the Mars’ rovers Spirit and Opportunity). But space telescopes are phenomenally expensive and take funds away from other unmanned scientific missions. Besides, it’s not just astronomers who look at the stars, and I seriously wonder how long NASA will continue to receive funding for its science missions if someday soon the last person ceases to be able to see anything in the sky at night beyond our own light-polluted atmosphere. Every night this year that I have shown someone Saturn through my telescope during a campground program I heard gasps, shouts, and exclamations of delight. Every night when people see its rings and moons with their own eyes I hear the half-joking question, “Are you sure you aren’t just holding a slide up there?” I know that every one of them has seen a picture of Saturn in far more detail from the Cassini spacecraft currently in orbit, yet in their hearts they recognize there is still something unspeakably special about seeing it with their own eyes. This is the wonder that sends children off to be scientists or at the very least value the joy of cosmic exploration and the possibility of answering those question with which I started this journal entry. How much longer they will continue to do any of these if this personal connection to the universe is removed, I do not know.
In the concluding chapter of Carl Sagan’s Cosmos he describes in agonizing detail the sacking of the Library of Alexandria. He concluded, however, that when the mob came with the torches there was no one there to stop them because no one had ever bothered to make the scientific and technological contents of the library personally relevant to the public. Every night that light pollution steals another star from the view of the majority of people on Earth, we lose another personal connection to the exploration of the cosmos. When the last one goes, what will we have lost again?
The Milky Way over Bryce Canyon National Park
My flashlight illuminates my path as I hike down the Navajo Loop into Bryce Canyon at night. Jupiter shines brightly just beneath the center of the Milky Way in Sagittarius. Credit: Tyler Nordgren |
My travels are just about over. By the time I leave here I will have been traveling for exactly one full trip around the Sun. I have one more stop after this in Glacier National Park from July 20 to August 13. My next post will not be until I arrive in Glacier and begin to give astronomy programs in a park where evening twilight doesn’t end until midnight.
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