In this detailed view from NASA's Hubble Space Telescope, the so-called Cat's Eye Nebula looks like the penetrating eye of the disembodied sorcerer Sauron from the film adaptation of "The Lord of the Rings." The nebula, formally cataloged NGC 6543, is every bit as inscrutable as the J.R.R. Tolkien phantom character. Though the Cat's Eye Nebula was one of the first planetary nebulae to be discovered, it is one of the most complex such nebulae seen in space.

Each telescope has its own advantage, for instance the refractor is better for observing the planets and the moon and the reflector for deep sky objects (e.g. galaxies). However the refractor suffers from what is known as chromatic aberration. This is when the different wavelengths (colours) of light are brought to focus at different points due to the glass in the objective lens refracting (bending) the different wavelengths to different degrees. This, however, is only noticeable in refractors with an aperture (diameter of objective lens) of 10cm (4") or more. It can be corrected using achromatic and apochromatic (modified lenses)...

It is surprising to many people that radio astronomy does not entail listening for E.T. to phone home. S.E.T.I, (The search for extra terrestrial intelligence) is a relatively tiny portion of radio astronomy. It would seem that the public perception of radio astronomy conjures up images of astronomers in tight jeans wearing headphones to detect some weak signal buried in the galactic noise. If we apply a brief reality check, we find that radio astronomy is much like optical astronomy, in that telescopes (instruments that detect, image and magnify) are used to observe the cosmos. The difference is that while...

A meteor, or a shooting star as they are more commonly known, is the streak of light produced when a meteoroid burns up in the Earth's atmosphere. It looks like a star falling towards us as it momentarily flashes above us. The meteoroids, which produce the meteors, are dust and rocks in space. Comets and asteroids are the two main sources. Upon coming close to the Sun, comets lose dust and fragments while asteroids lose fragments if they collide together. As the Earth moves along its orbital path, meteoroids hit the upper atmosphere, and hurtle towards Earth's surface. Once in...

The Earth is unique amongst the terrestrial planets in having a large satellite, the Moon, which, relative to the Earth, has the largest mass of any satellite - parent system (1:81). Numerous lines of evidence indicate that the Moon was derived from the Earth as the result of a singular impact event soon after the initial formation of the Earth. As a result the subsequent evolution of the Earth and the emergence and development of life, has been strongly influenced by the presence of the Moon. This article will highlight and explain the key areas in which the Moon has...

A comet is generally considered to consist of a small, sharp nucleus embedded in a nebulous disk called the coma. American astronomer Fred L. Whipple proposed in 1949 that the nucleus, containing practically all the mass of the comet, is a 'dirty snowball' conglomerate of ices and dust. Major proofs of the snowball theory rest on various data. For one, of the observed gases and meteoric particles that are ejected to provide the coma and tails of comets, most of the gases are fragmentary molecules, or radicals, of the most common elements in space: hydrogen, carbon, nitrogen, and oxygen. The...

Although neglected scientifically and publicly for a long time, in the past ten years asteroids have been the subject of much interest and debate. This has caused by announcements that the extinction of the dinosaurs 65 million years ago was caused by an asteroid that came to Earth off the coast of Mexico and also by movies such as Deep Impact and Armageddon. NASA Administrator Daniel Goldin's "faster, better, cheaper" motto has also been a boon to asteroid science mainly because a small asteroid relatively close to Earth is a lot cheaper to visit than one of our larger planetary...

Sometimes it pays to be looking in just the right place. Ask Carl Murray, Cassini imaging team member at Queen Mary, University of London. Murray was examining images taken June 21, 2004, a few days before the Cassini spacecraft arrived at Saturn. "I noticed this barely detectable object skirting the outer part of the F ring. It was an incredible privilege to be the first person to spot it," he said. The object Murray discovered was moving near Saturn's F...

If the era when the first galaxies formed can be called the opening act in the universe's history, then the Hubble Space Telescope has given scientists a front-row seat. Astronomers gathered at the Space Telescope Institute in Baltimore September 23 to review their initial analysis of the spectacular Hubble Ultra Deep Field (HUDF) photo released 6 months ago. Their preliminary view was that some of the structures contained in the image were a sampling of the earliest star-forming galaxies ever...

Take two sheets of white paper. In the middle of one sheet, poke a hole with a pin. Hold the sheets about a foot apart, so the punctured sheet faces the Sun, and you'll see a tiny solar image on the second sheet. This principle, called pinhole projection, was known to ancient Greek and Chinese scholars and, in the middle of the 19th century, morphed into one of the earliest photographic techniques. The NASA Institute for Advanced Concepts (NIAC) currently is studying a proposal for a space mission that could produce images of planets orbiting a distant star. The plan...