Saturday, March 29, 2008
With a redshift of 0.46, 3C295 held the record as the most distant known galaxy cluster until 1975. How far away is it? About 4.8 billion light years.
Modern electronic detectors are much more sensitive to light than the old photographic plates used by Minkowski and others and as such galaxies of vastly greater distances are now known making Minkowski's find seem almost close.
Friday, March 28, 2008
March 29th also kicks off National Dark-Sky Week which runs until April 4. This is a great time to see the nighttime sky and learn what can be done to preserve it. Visit the website of the International Dark-Sky Association, THE source on nighttime lighting, to learn about what can be done each and every week of the year.
March 22, 1955 — Discovery of comet 52P/Harrington-Abell by Robert G. Harrington and George O. Abell on a plate taken during the National Geographic Society-Palomar Observatory Sky Survey.
Thirty six years later the 60-inch is a major workhorse telescope. Its main task now is in rapid-response observations for gamma-ray bursts and other transient phenomena.
Wednesday, March 26, 2008
Two years and one day after the first (failed) mirror was cast (see yesterday's post) the second (successful) disc began its trip from Corning, New York to Caltech in Pasadena, California on March 26, 1936.
The 20-ton piece of glass traveled 3,000 miles by rail at the breakneck speed of 25 miles per hour. It seemed like all of America came out to watch the event as thousands of people went down to the train tracks, all across the nation, to watch the train roll past. The route was carefully chosen to ensure that all bridges could handle the load and the the crate would safely pass under all of the overpasses along the way.
The train did not travel at night, making layovers in Buffalo, NY; Cleveland, OH; Bellafontaine, OH; Indianapolis, IN; Matoon, IL; St. Louis, MO; Brookfield, MO; Kansas City, MO; Wellington, KS; Canadian, TX; Clovis, NM; Belen, NM; Winslow, AZ; Needles, CA; San Bernardino, CA. It took 16 days to travel from Corning to Pasadena.
With the delays caused by World War II, the mirror remained at Caltech for 11 1/2 years as it was carefully crafted into the proper shape .
A few years ago I had the honor to meet a retired gentleman who was an elementary school student in Kansas when the mirror made its historic trip. He told me how his entire school was brought down to the railroad tracks to watch the mirror and the train go past. It is always a pleasure to meet people who have had a personal connection to part of the Palomar story.
Tuesday, March 25, 2008
Seventy four years ago today (March 25, 1934) the dedicated crew at Corning Glass Works made their first attempt at casting the 200-inch mirror.
Creating the 200-inch mirror was a monumental task.
Initially General Electric was hired to fabricate a 200-inch disc made out of quartz. Nearly a million dollars later, that idea was abandoned. George Ellery Hale approached the Corning Glass Works of New York with a proposal to instead cast the 200-inch mirror out of a special blend of glass called Pyrex. Changes in temperature make Pyrex expand and contract much less than ordinary glass, so a Pyrex mirror would be much less prone to the focus and distortion problems that plagued other glass mirrors.
The top side of a mirror has to be perfectly shaped, while the back is used for support. The back side of the 200-inch disc is honeycombed. The triangular pieces are hollow areas to make the mirror weigh less, while the round area are places where the mirror is supported from below to help the topside to maintain its critical shape. Making the honeycomb undersurface provided some challenges.
A mold was built inside of an oven (think bottom of a waffle iron) to give the mirror’s underside its special shape. The hollow spots were created by bricks that were held down by steel bolts.
After taking nearly a month to melt enough glass, on March 25, 1934 the molten glass was ladled into the mold. Alas, the glass was hot enough to melt the steel bolts and the bricks floated to the surface and ruined the mirror. This first disc is on display at the Corning Museum of Glass in New York. The successful second casting was performed in December 1934.
The Corning Museum of Glass website has a great article on the making of the mirror called The Glass Giant.
I have seen many wonderful photographs of March & December, 1934 castings. Thankfully it was also captured in two paintings by artist Christian Jacob Walter. Shown above is "Pouring Glass". The other painting is called "Ladling Glass." The paintings are on display at the Earth and Mineral Sciences Museum at Penn State University.
Later this year I hope to make the trek to visit Corning and to see the first disc. It is a part of the Palomar heritage that I need to visit.
Monday, March 17, 2008
Helping me to bring Palomar to the people are a great group of volunteers, the Palomar Observatory Docents (or PODs as I call them). Many of our active docents are shown in this recent group photo.
The PODs are a dedicated and wonderful group of people who have become part of the Palomar family by helping in our public outreach program in a variety of ways, including giving tours of the Hale Telescope.
We are always looking for more people who might be interested in helping out, especially as we are about to enter into our new tour season with docent-led tours of the 200-inch Hale Telescope given twice daily on Saturdays (11:30 am & 1:30 pm) from April through October.
Potential docents don't need to be an astronomer or a Palomar expert to apply. A willingness to learn and an interest in speaking to people is all that is needed. More information can be found here.
Eight years ago yesterday NASA's Near-Earth Asteroid Rendezvous (NEAR) spacecraft was re-
named NEAR Shoemaker to honor the late Dr. Eugene M. Shoemaker. Gene Shoemaker was legendary and inspirational planetary geologist who had a remarkable career. He was instrumental in organizing and performing many comet and asteroid surveys in the past century. He was perhaps most famous for finding, along with Carolyn Shoemaker and David Levy, Comet Shoemaker-Levy 9 with the Palomar 18-inch Schmidt in March 1993. The comet had broken up with a previous close encounter with Jupiter and collided with it in spectacular fashion in July 1994.
After a year in orbit about the asteroid Eros NEAR Shoemaker became the first spacecraft to perform a landing on an asteroid. Here is a sequence of images taken during one orbit about Eros:
Sunday, March 16, 2008
Saturday, March 15, 2008
As long as I don't get stuck in the snow on Palomar I hope to see you there!
Sunday, March 9, 2008
Caltech's Nicholas Law will be giving a free public lecture on adaptive optics, LuckyCam and what is to follow it on Saturday, March 15 at 7:00 pm. The talk will be held downstairs at Oceanside Photo & Telescope, located at 918 Mission Avenue in Oceanside. (Click here for a map.) No reservations will be needed to attend the lecture, but seating will be limited.
Above, the Cat's Eye Nebula. Below a comparison of the Hale Telescope (left) vs. the Hubble Space Telescope (right):
Notice that the Hubble sees more stars than the 200-Hale. Why? Its darker up there. However, you should be able to tell that the size of the stars is smaller in the Palomar image. After we successfully correct for the distortions caused by the atmosphere our larger telescope actually obtains higher-resolution images.
Want to know more about this? Attend the talk on Saturday night which is brought to you by the Friends of Palomar Observatory and the Oceanside Photo & Telescope Astronomical Society.
Saturday, March 8, 2008
From left to right this panorama shows the Palomar Crestline area (southeast); the ridge along State Park Road; French Valley, with its pond and Morgan Hill behind it; and the dome of the Palomar 24-inch telescope. Directly behind the dome is the Temecula Valley area and Mount Wilson in the distance behind it. At the right-hand portion of the image we are looking to the north towards Hemet.
Thursday, March 6, 2008
Astronomer Edwin Hubble (1889-1953) played a pivotal role in deciphering the vast and complex nature of the universe. His meticulous studies of spiral nebulae proved the existence of galaxies other than our own Milky Way, paving the way for a revolutionary new understanding that the cosmos contains myriad separate galaxies, or “island universes.”
Most of the great successes of Hubble's career were achieved not at Palomar but at Mt. Wilson. So it is only fitting that the dome of the 100-inch Hooker Telescope be shown behind him. The "spiral nebulae" referred to in the USPS description are what modern astronomers refer to as spiral galaxies.
Back in the 1920s no one was certain if they were part of our own Milky Way Galaxy or separate galaxies unto themselves. In 1923 Hubble used the 100-inch telescope to resolve and measure Cepheid variable stars in the Andromeda Galaxy (M31). Cepheid stars vary in brightness in a regular way that is directly proportional to their brightness. Once it is known how bright they really are and how bright they appear, it is possible to determine their distance.
Hubble found that the Cepheids in M31, and thus the galaxy itself, are 1 million light-years distant. (Modern figures put the distance at 2.9 million light years.) The only conclusion was that M31 and the other "spiral nebulae" were separate galaxies, completely distinct from our Milky Way.
Hubble pushed the bounds of known space even further with his 1929 discovery that the universe is expanding. This had a profound influence on cosmology and was the first clue pointing towards the Big Bang.
Hubble didn't get a lot of observing time at Palomar. The 200-inch telescope project took a long time to complete and Hubble passed away just five years after its dedication
If you are interested in reading about the life of Edwin Hubble I strongly recommend that you track down a copy of Gale E. Christianson's Hubble biography Edwin Hubble: Mariner of the Universe. If you are in a hurry, or just need something more right now you can read his biography posted on the Hubble Space Telescope website.
Saturday, March 1, 2008
Astronomer George Abell (1927 – 1983) was born 81 years ago today. He had a short, yet remarkable career in the world of astronomy.
Abell used the data from the survey to produce the first major catalog of clusters of galaxies. His catalog included thousands of galaxy clusters and it the basic reference in this field. It served as the one of the starting points for observational cosmology. He also showed how the brightness of certain galaxies within a cluster could be used to determine the distance to the galaxy cluster, allowing astronomers to map the large scale structure of the universe.
Here is a sky-survey image of a portion of Abell 2151, also known as the Hercules Cluster. The cluster is around 500 million light years distant and is part of the larger Hercules Supercluster.
Abell also studied the planetary nebulae that were revealed by the sky survey. Along with Peter Goldreich he correctly concluded that planetary nebulae evolve directly from red giant stars.
Here’s a sky-survey image of the planetary nebula now known as Abell 39. It is located about 7,000 light years away in the constellation of Hercules.
In addition to his astronomical work George Abell was a noted educator and popularizer of astronomy.
George Abell was honored by having an asteroid, 3449 Abell, named for him. The asteroid was discovered at Palomar Observatory by Eleanor Helin and S. J. “Bobby” Bus.