Because we can reason, the human race looks for reasons--we want to explain everything we see. When we look to the left, to the right, down at our two feet, we see the Earth. Biology, anthropology, archeology, geology, botany, physics, mathematics and countless other sciences and pseudo-sciences have been and are used to explain what we see in our immediate world. When we look up we see...stars.
Astronomy was the first science to come from our questions about the stars, cosmology becoming a science shortly after. These days we have astrophysics, an area of study finally linking what we see above and what we know below, acknowledging our place in the universe. But all of our recise calculation and thorough theories mean nothing if we cannot see.
Cassiopeia is one of the more noticeable constellations of the north sky. Opposite the Big Dipper, she rotates around the North Star, Polaris. Because she is circumpolar, the five brightest stars go from looking like a W to a 3, M and E as the night progresses.
The W of Cas is made up of five main stars. Caph [Beta Cas] is the first star to the west. Then comes Schedar [Alpha Cas], followed by Cih [Gamma Cas], which is the central point. From there are Ruchbach [Delta Cas] and Segin [Epsilon Cas], the easternmost stars. Stars of secondary brightness are Achird [Zeta Cas] (named because it lies between Schedar and Cih, appears to be part of the main constellation), Eta Cas, Theta Cas, Iota Cas, and Lambda, Kappa and Rho Cas.
As in the rest of the universe, Cas contains many binary stars. To name a few: Zeta Cas is a binary star system, and Lambda Cas is actually a tri-star system; of the fainter stars from Earth, Omicron Cas has a dim double, and Phi Cas is another multiple-star system.
Other stars of interest are the variables. Beta Cas is a type delta Sct: 2.25-2.31 variable with period of 2h 30m 11.5s. Gamma Cas is new sort of variable--it fluctuates unpredictably between a magnitude of 1.6 and 3.0. This exception to the rule has brought about a new classification of variable stars: "Gamma Cas Variables." These stars are either rapidly rotating subgiants of dwarfs with emission spectra. They vary in magnitude, though typically not as much as Gamma Cas itself. Gamma Cas remains an exception even in its own classification.
Further interest in the Gamma Cas area--over time-exposure photographs or scientific observation, this star is associated with two faint nebulosities. The most readily visible of Cas's non-star objects, they are only part of a local family of deep-sky objects. (image gallery)
Cas holds two official Messier objects, open clusters M52 [NGC 7654] and M103 [NGC 581]. NGC 457, another open cluster, contains Phi Cas, one of the most luminous stars known, shining at least 2x10^5 times as bright as our sun. The fourth open cluster in Cas is NGC 7789 which contains approximately a thousand stars. 7789 is near Beta Cas, just between Rho and Sigma Cas. Cas also contains one of the more photogenic nebulae, The Bubble Nebula, or, NGC 7635.
NGC 7635
As seen in the pictures above, the Bubble Nebula is a beautiful part of the sky. Part of a larger network of bubbles and shells called S162, the Bubble Nebula is the smallest of three surrounding massive star BD+602522. Stars like BD created the bubbles. As fast moving gasses expand off of BD, they push sparse gasses surrounding it into a shell. Energetic light from the star then ionizes the gas, causing it to glow. Other gas clouds in the region can also be energized by either a bubble's interior star or the heart of the gas shell. They then glow, as well. NGC 7635 is approximately 6 ly across and expanding at a rate of 4x10^6 m/h. It is 7x10^3 ly from Earth.
M52
M52 is an open cluster of stars located approximately 5x10^3 ly from earth and having an apparent dimension of 13 arc minutes, or, 19 ly in extension. M52 is about 6º NW of Rho Cas. To find it easily, draw an imaginary line between Alpha and Beta Cas and then extend it, doubling the original length. M52 is about another quarter-length of line beyond that. It is home to about 200 stars (a survey in 1959 found 193 member candidates for the cluster in a 9º area) which, at the center, reach a density of 3 stars per cubic parsec. Considering that our closest neighbor is slightly more than one parsec away, one can see why it is considered a "cluster."
M103
This open cluster can be found 1º N of Delta Cas. Located 8.5x10^3 ly from Earth, it is home to at least 40 stars. Observers of M103 are often confused by the non-member binary Struve 131, two stars of magnitudes 7.3 and 10.5. The brightest cluster members reach 10.5 mag or brighter, but are further away, thus this binary system is often included when observing M103. The cluster has an apparent dimension of 6 arc minutes (or 15 ly across) and, although there is some speculation, is somewhere between 20 and 25 million years old. There is one red giant in the cluster of about 10.8 magnitude, a remnant of the bright blue, super-hot stars that the long-since dispersed gas cloud formed in this region. M103 is easily found with good binoculars or a weak telescope, but hard to pick out with more powerful instruments, as the stars tend to "scatter".
So there is what we can see, but the question is, how can we see it?
Telescopes
The real science of astronomy didn't begin until Tycho Brahe established his astronomical laboratory on an island between Denmark and Sweden. In the days before light pollution, this was no doubt far enough from civilization for good naked-eye observing. The supernova he witnessed, now a SNR, is often coupled with Cas A in research of SNR gas shells, since Tycho's is only 100 years older. Using his 7' sighting rod and knowledge of trigonometry, Brahe made the most accurate observations up to that time. They were also the most accurate observations until the late 1600s, when more precise methods and instruments were developed. Brahe died in 1601; the telescope was first described in 1608, used for astronomy only one year later.
Tycho's method of declination/ascension measurement remained unbested for several centuries. Furthering the science of astronomy was, from that point on, in the hands of the glassmakers.
"The first spectacles were made of biconvex lenses, which enlarged objects and which were particularly useful to old people who are often far-sighted" (Asimov, 15). The development of light collection and refraction lenses began as early as 300 B.C. with Greeks supposedly using "burning glasses" to set fire to Roman ships. Early attempts as lenses (plano-convex and bi-convex) have been found, dated back as early as 2000 B.C. Alhazen, an Arabic physicist working around 990 A.D. was one of the first to point out refraction's use for collecting and recording starlight, as well as the more mathematical issues of focus distances and the sorts of lenses to use.
It wasn't until the seventeenth century that this knowledge was really put to use toward observation of the heavens. Hans Lippershey, a Dutch spectacle-maker, was said to have affixed the first plano-convex and biconvex lenses in a tube, what he called it a "looker," which no doubt sounds much better in Dutch. Once scientists got a hold of the "looker," it was dubbed an "optic tube", eventually becoming a "telescope" from the Greek for "to see at a distance." Galileo is the most recognized user of the telescope, since his careful observations of Venus and Jupiter's moons revealed the Earth's position not in the center of the "universe" but merely as one of several planets orbiting the sun.
Galileo's telescopes were refractors, crude by today's standards, made of two lenses in a wooden tube. They were mounted on an upright axis or hand-held for observation, a method long-since discarded. Early astronomers needed steady hands. These days, what refractors there are mounted perpendicular to the celestial pole, thus making it easier to track stars. Refractors work for magnification, but pose the problem of two lenses distorting the light. Besides, the image is upside down. A four-lensed telescope was invented that produced an upright image, but it was used for "terrestrial" viewing as the additional glass dimmed the incoming light significantly--light moves slower through glass, like water--and brightness is the essence of astronomy.
Newton, despite "discovering" gravity and coming up with the first working model of gravitational attraction (never mind its accuracy), was the first to build a reflecting telescope. Reflectors only require the light to pass through one magnifying lens (biconvex) and then bounce across two mirrors into an eyepiece. If the mirrors are relatively flaw-free, the image is of much higher quality than a refractor's. Reflecting telescopes are the mainstay of astronomy today; the last large refractor was built in 1897 just outside Chicago by George Ellery Hale, funded by Charles Yerkes, after whom it was named. The Yerkes telescope is a 1 meter (40") refractor and is maintained as more of a tourist attraction than a scientific instrument.
Shortly after the Yerkes observatory was completed, the reign of large refractors came to an end. Though images were better and larger apertures were suddenly possible, the difficulty of maintaining proper focus conditions rubbed many the wrong way. A comment was made in 1912 by H. H. Turner: "The reflector is so seriously influenced by air currents and changes of temperature as to be an instrument of moods and Dr Commons has accordingly compared it, somewhat ungallantly, to the female sex." Like ships and cars, telescopes are, apparently, a "she."
The true difficulty was in making the mirror--focusing pales in comparison. Because lenses and mirrors warp with temperature, the days before industrial cooling systems forced lens-making to go underground. Far from being a political situation, though, subterranean environments kept the glass at a stable temperature and pressure for grinding. As lenses and mirrors got bigger and bigger, grinding took longer and longer; pieces too large for conventional means of transit had to be strapped to train cars and padded heavily. Once up on the mountain, though, seasonal changes, weather and night and day can warp the mirror sufficiently as to render it useless. Thinner mirrors are better but pose the problem of actually manufacturing them. Mirrors with deep ribs in the back was the first solution. Better than that is the series of mirrors, computer-calibrated to work as one. In the VLT [Very Large Telescope], the honeycomb set of mirrors in each of the four concurrent telescopes are calibrated by tiny "fingers" on the back which constantly readjust for temperature, air pressure and other situations, rendering astronomy photos from the ground that are as clear as Hubble's from space.
Ah, the Hubble Space Telescope. As most Americans who were alive in the '90s are aware, Hubble is a large reflecting telescope that was shot out into space and didn't work for the first run. The mirror had a flaw. This was quickly fixed, though, and Hubble has been delivering unprecedented images of deep space up to that time. As mentioned before, it's been up to the glassmakers.
Other space observatories, like the Chandra X-ray Observatory [CXO](see following section), bring back information we are unable to gather on Earth, no matter how calibrated our super-thin mirrors. Telescopes like CXO must have an orbit outside the Earth's prodigious radiation field, since the wavelengths present would obscure any incoming X-rays from space.
Then again, there is a limit to everything and the glassmakers can no longer help us in one area of astronomy, although they can no doubt add their expertise in creating a well-rounded dish: Radio astronomy. Discovered serendipitously by employees of a telephone company, radio wavelength radiation from the sky tells us not only that the Big Bang happened but gives us additional and new information for every phenomenon observed through other, optical methods. The largest radio arrays are in the American southwest. The VLA, or Very Large Array, is one such and is made of 27 separate 25 meter dishes working collectively along a Y-shaped line of railroad tracks. This method of information-collection is called Long-Baseline Interferometry, also used by the VLT mentioned above. The most recent project in radio astronomy and LBI is the ALMA concept, touted to become the "world's most powerful radio array," the Atacama Large Millimeter Array will be 64 (or more) 12 meter dishes working collectively on millimeter and sub-millimeter wavelengths, to be located in Chile. It's detection sensitivity is projected to be 20 times that of the VLA.
There is, in a rather haphazard and deformed nutshell, the history of astronomy and observing. The Phenomenon section after this holds more information as the history of observing Cassiopeia--specifically the Cas A supernova. Of the information collected about the Cas A SNR, CXO has brought in the best information.
Chandra is the most technologically advanced space telescope currently running. Its creators are most congratulated for it's darkness-dodging orbit. More elliptical than any other satellite's orbit, Chandra maintains her power source on a 24-hour basis, thus also maintaining her ability to deliver stunning information.
Chandra has been used most for deep-space observation since her launch in 1999. And by "deep space" I mean "the edge of time." Chandra has captured clearer pictures of the distant past than any other device, delivering images of galactic development from 12 billion years ago. From very recent data, Chandra has confirmed one of several hypotheses for galaxy evolution. From CXO's observations, a dense region of intergalactic gas cools to form several smaller galaxies by means of the cosmic "nudges" left over from the Big Bang. Because these are close together, they begin to gravitate toward each other (toward the largest of the group) and, eventually, collide, which produces a supermassive galaxy, much like Andromeda. In short, black holes control the development of galaxies in the early universe. This is information we cannot gain optically--black holes are not bright enough to observe.
For more information on the part Chandra and other observation methods play in observing Cassiopeia, continue on to Phenomenon.
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