Astronomy - Eyes on the Universe
One of the Three Early Sciences - Astronomy
Pythagoras, Ptolemy, and Plato are the three “Ps” of the early sciences. These early philosophers provided the basis for investigators of the Renaissance and then the Scientific Revolution to synthesize mathematics, observations, and facts to develop more accurate world views.
Copernicus was so afraid of his new world view with the Sun at the center of the universe that he did not publish his work until after his death.
Brahe refined the established facts with meticulous observations of the heavens and developed a revised theory to Copernicus’s planetary orbits.
Kepler analyzed the Brahe data, applied mathematical theory and produced his three laws to describe planetary motion. He shattered the perception of the circular perfection of the heavens with the fact that elliptical orbits in nature are the norm.
Kepler’s contemporary, Galileo developed the principles of force and trajectory for earth-bound motion as opposed to celestial mechanics. He was the first investigator to blend experiment and logic with the practice of modeling behavior in nature. Galileo also honed his skills of observation with the use of the telescope, a tool that also demonstrated the imperfection of the heavenly bodies. Mountains on the moon were observed, suggesting another imperfection of the heavens, and the four observed moons of Jupiter suggested that Earth was not unique in having a satellite. Galileo was rewarded with house arrest for his remaining days of life, simply because he was searching for truth in nature.
Newton built upon this early work and kicked off the scientific revolution with his laws of inertia, determination of the force of gravity, and a myriad of other inquiries such as his work in optics.
Breaking News in Astronomy
According to observations by NASA's Chandra X-ray Observatory and ground-based optical telescopes, the supernova SN 2006gy is the brightest and most energetic stellar explosion ever recorded and may be a long-sought new type of explosion.The top panel of the graphic shown below is an artist's illustration that shows what SN 2006gy may have looked like if viewed at a close distance.
The bottom left panel is an infrared image, using adaptive optics at the Lick Observatory, of NGC 1260, the galaxy containing SN 2006gy.
The panel to the right shows Chandra's X-ray image of the same field of view, again showing the nucleus of NGC 1260 and SN 2006gy.
The Chandra observation allowed astronomers to determine that SN 2006gy was indeed caused by the collapse of an extremely massive star, and not the most likely alternative explanation for the explosion, the destruction of a low-mass star.
Story credit: NASA
Image credit: Illustration: NASA/CXC/M.Weiss; X-ray: NASA/CXC/UC Berkeley/N.Smith et al.; IR: Lick/UC Berkeley/J.Bloom & C.Hansen
Strange but True
The Size of the MoonThe Moon appears to be larger on the horizon than when it's high in the sky. This is nothing more than an optical illusion. It does not involve any enlarging effects of the earth’s atmosphere on the moon light.
Consequently, using the dome as a reference, we expect objects on the horizon (such as the Moon) to be farther away. Sincen the Moon is no farther away than when it is overhead, the human brain over compensates and imagines that it is larger.
Cosmology and its Role for Humanity
One of the hot topics in the field of cosmology is the role of dark matter in determining the fate of the universe.In the Test Your Knowledge segment of the July 2007 Newsletter, we looked at what Dark Matter was.
The search for dark matter began in the 1930s after astronomer Fritz Zwicky figured out that there was missing mass in the universe. He arrived at this conclusion using his telescope and observing the motion of the heavens. After the rest of the scientific community caught up to the notion of dark matter, a frenetic search for it began and continues to this very day.
Dark matter is believed to be something that does not radiate light or give off heat. It is known to exist because of the gravitational pull it exerts on stars and galaxies. It makes up 25 percent of the mass of the universe and is expected to be detected as tiny particles left over from the Big Bang that occurred over 13 billion years ago.
Modern day experiments are looking for particles called weakly interacting massive particles, or WIMPs, for short. The experiments are conducted underground so that interfering cosmic rays do not affect the results. These large detector machines are on standby to capture the rare occurrence of a WIMP colliding with an atomic nucleus and producing an elastic recoil. If this happens, voila, a WIMP has been detected. So far, no such phenomenon has been recorded. These underground experiments are active in Minnesota and South Dakota, Canada, England, France, Italy, Japan, and Russia.
Time will tell if a WIMP is detected. In the meantime, cosmologists are deciphering the implications of dark matter along with its companion force, dark energy, to reveal the fate of the universe. Pretty heavy stuff if you ask me.
Featured Astronomer
Hubble was recognized by his peers in the scientific community as a giant among them. Hubble’s contributions to astronomy are many and of great significance. His work also profoundly shaped the way the rest of the world viewed the universe.
One of the great thinkers of the twentieth century, Albert Einstein, attributed his change of view of the universe to Hubble, from static to dynamic – something his own relativistic equations could not do. While Einstein’s theoretical physics defined the expanding universe concept, Hubble’s comprehensive telescope work laid its observational basis.
Early in his career, Hubble took a job working at Pasadena California’s Mount Wilson Observatory as an astronomer under Ellery Hale’s direction. Soon after his arrival, Hubble trained the powerful new 100-inch telescope on the Andromeda nebula. Hubble was able to resolve what were previously faint images into individual stars, thereby showing that Andromeda might indeed be its own galaxy. With these observations Hubble proved the universe was at least twice as large as previously believed and much older. In the scientific community, Hubble had settled “The Great Debate,” which pitted one viewpoint that the Milky Way was the entire universe against the other viewpoint that the Milky Way was one of many nebulae in the larger universe.
Hubble’s success in measuring the distance of dimmer and dimmer nebulae led to his next major discovery in 1924. His observational work proved that most galaxies are hurtling away from the Earth at several thousand miles per second. He concluded that the universe is growing even larger, just like spots on an inflating rubber balloon. Each galaxy observes all of its neighbors moving away and the farther apart the galaxies, the faster their separation. Hubble surmised the universe would double its diameter every 1.4 billion years and this rate of expansion led to “Hubble’s law,” which states the further a galaxy is from us, the faster it is moving away from us. Hubble based this linear result on a relationship between the distance of a galaxy and the red-shift of its spectral lines, a phenomenon whereby the wavelength of light increases as an object moves further away from us.
Hubble profoundly affected the rest of the world’s view of the universe. The universe was much older and larger than previously believed. Hubble also taught his colleagues that the study of the universe only made sense by looking at the big picture.
One of the great tributes to Hubble can be found by simply looking to the heavens and seeing the Hubble Space Telescope. Named in his honor, the Hubble Space Telescope was launched in 1990 and placed into a 380-mile orbit above the Earth to continue the job of peering into the far reaches of the universe.
Fiber Optics and Astronomy Aligned - Its Heavenly!
In researching a piece for Eugene Shoemaker and asteroids, I came across the Titius-Bode Law, which defines planetary spacings. This empirical eighteenth century law was derived by dividing the distance between the Sun and Saturn into 100 parts, then normalizing distances into whole numbers as follows:| From Sun to: | Parts | Total |
|---|---|---|
| Mercury | 4 | 4 |
| Venus | 4+3 | 7 |
| Earth | 4+6 | 10 |
| Mars | 4+12 | 16 |
| missing | 4+24 | 28 (no Martian satellite detected) |
| Jupiter | 4+48 | 52 |
| Saturn | 4+96 | 100 |
| Uranus | 4+192 | 196 (predicted a planet would be here) |
This law suggested a planet was missing between Mars and Jupiter and predicted that a planet should be located beyond Saturn. It was later discovered that the missing planet was actually many asteroids orbiting the sun in the “28th” orbital position. Furthermore, by extrapolation, another planet should be located at the “196th” orbital. After the planet Neptune was discovered by William Herschel in 1781, its distance was calculated to be in the “192nd” orbital, very close to the orbit predicted by Titius-Bode.
While there was impressive agreement between predicted and measured planetary orbits, I was even more struck by the parallels of Titius-Bode to the universe of Synchronous Optical NETwork (SONET) communications. This telephony standard for fiber optic systems defines Optical Carriers (OC) at specific bit rates. Popular SONET product configurations utilize OC3, OC12, OC48, and OC192 optical bit rates; these designations consistent with the Venus, Mars, Jupiter, and Uranus orbitals, respectively. Clearly, SONET technology is out of this world.
Massive Sky Surveys of the Next Decade
Dr. David Wittman is a Harvard graduate who received his doctorate from the University of Arizona and became professor at UC Davis near Sacramento, CA. The talk given on February 4, 2008 centered on systematic imaging and the Large Synoptic Survey Telescope (LSST) - Sky Survey with LSST. Wittman's research focuses on astronomical optical surveys, which is “where it is at.” In the optical range of the electromagnetic spectrum, he said that more can be done with the collected data set. He stressed that this work is on imaging and not spectroscopy. To set the baseline for the functional scope of the LSST, Wittman compared it to the Hubble Space Telescope (HST), where the former captures images from the entire sky while the latter focuses on a particular point in the sky.
Before diving into the LSST approach of sky surveys, Wittman began with a review of past surveys. The Palomar Observatory Sky Survey (POSS) was completed in two phases; one in the 1950s and the other in the 1970s. The 1.2-meter Oschin Schmidt telescope was used with photographic plates. The project was financed by the National Geographic Society and the mapping of the Northern Sky was completed in 1958. During the 1970's, the U.K. Schmidt telescope, nearly identical to the Oschin telescope, carried out the Southern Sky Survey. In the early 1980s, Palomar's Oschin telescope was upgraded and a second sky survey called POSS II was completed. So both the northern and southern hemispheres were mapped. Sky Survey using POSS.
Another ongoing sky survey is the Sloan Digital Sky Survey (SDSS), which is just finishing up as of this writing. It will provide a very good general survey of the heavens: SDSS Sky Survey. The SDSS uses a 2.5-meter telescope with a huge CCD camera that incorporates fixed filters. With multiple filters, the same star will be imaged at five different wavelengths as the star passes overhead, plus a spectra can be captured for the more interesting celestial objects. This color imaging survey has made great strides over the black and white surveys done with the previous POSS technology. There have been major gains in quality with better resolution (it is now easier to resolve very close together objects), superior linearity (digital detectors provide the linearity), and precise calibration.
The Deep Lens Survey captured twenty degrees (using five 4-degree square areas) of the sky and is one of the more recent attempts at capturing astronomical data. Mosaic CCD imagers at NOAO's Blanco and Mayall telescopes are being used to conduct this optical survey. In addition, optical transient events such as moving objects and supernova candidates, are being released immediately as they occur in real time.
Whittman posed the question, “Why not have it all? That is, a wide area of sky captured with great depth in the data collection.” This is the objective of sky surveys going forward. He also gave a rationale as to why this work should be done. One major scientific quest is to understand dark matter and dark energy. The universe is believed to be comprised of atoms (4%), dark matter (22%), and dark energy (74%). Atoms make up all of the matter people are familiar with. Proof for dark matter is seen in the formation of elliptical galaxies, the phenomenon of velocity dispersion of galaxies in clusters, and gravitational lensing to name a few. Whittman reported that a density of 1 gram per square centimeter gives a strong lensing effect.
Conventional wisdom was shattered in 1998. The major cosmological surprise was that the cosmic expansion was NOT decelerating but was accelerating. The suspected driver of this expansion is dark energy. Whittman related that four major probes of dark energy are underway. All of this probing can be done with optical surveys since dark energy affects the geometry of universes and their growth structure. Ways to detect dark energy include studying the following:
1. gravitational lensing that reveals both changes in geometry and structure
2. supernova dimming that reveals changes in geometry
3. baryon acoustic oscillations which show changes in geometry
4. cluster counting also illustrates changes in geometry and structure
As Whittman says, “Dark energy is a term for the unexplained acceleration of the universe.” He next recounted the other optical sky surveys in chronological order. They include Pan-STARRS, KIDS, DES, the LSST, SNAP, and DUNE.
After presenting all of these sky surveys in varying detail, Whittman delved into more detail on the LSST program. Because this telescope can detect very faint objects, a complete solar census can be completed. The main event, however, is that three billion galaxies and 100 associated attributes will be measured at each of six wavelengths, each with 200 time samples. This idea of capturing time intervals is a new idea in astronomical observations. By employing image differencing techniques, astronomers can see what has changed and then go investigate those areas further. Statisticians are being consulted to ensure a high signal-to-noise (S/N) ratio is possible to beat out the noise of the image. Supernova tracking is also much easier. Strongly lensed supernova should be extremely rare, but they would offer an independent determination of the Hubble constant. With the LSST, these rare events will be captured in the dataset, expected to be on the order of 1,000 lensed supernova. This is critical for more precisely defining Hubble’s constant as a supernova gives the requisite great spike of light. Three major elements are being addressed with this project: the telescope, the camera, and data management. Data is a key element of this project, expected to produce 15 to 20 terabytes per night.
The session wrapped up with an interactive Q&A and the participants wondering if the questions around dark matter and dark energy will be answered in the next 10 years.
Further Reading:
Please read the Discover article on the LSST.
Space Exploration - Mars in 2008
The Phoenix Mars Lander has two key objectives to meet:1. Study the History of Water in All its Phases
2. Search for Evidence of Habitable Zone and Assess the Biological Potential of the Ice-Soil Boundary
The Lander arrived on May 25th and safely found a home from where it will begins its mission operations. The Phoenix Mars Lander touched down at 4:53 p.m. Pacific Time (7:53 Eastern Time), in an arctic region called Vastitas Borealis, at 68 degrees north latitude, 234 degrees east longitude. Here are a few pictures:
Images courtesy NASA/JPL-Caltech
bravenet.com