Bob Doyle, Columnist
For the past 46 years, space telescopes have been sent into orbit allowing spectacular views of objects, using a variety of wavelengths (our atmosphere blocks off most of the waves shorter than light and a good deal of the waves longer than light).
Even for light waves, our atmosphere is a simmering broth of air currents, which dulls the focus of Earth-based telescopes. But digital cameras, used both in space telescopes and ground telescopes capture a high percentage of light particles (photons) to produce brighter images of space objects both near and far.
A way to get sharper images with Earth based telescopes is to make a number of exposures and then blend the images together, reducing the effects of air currents.
The large observatory scopes use adaptive optics where a laser beam is shot in the direction of the desired object; fluctuations in this laser “star” are used to correct the atmospheric distortions by applying pressure to optical elements.
The book I am reviewing for this column is “Space” by Marcello D’Angelo, an Italian journalist who has compiled a fine collection of space images, both from Earth based scopes and space telecopes.
“Space” is one of a number of books that promises the reader a tour of the universe. “Space” was published in 2012 by White Star Publishers with an ISBN of 978-88-0717-6.
In my opinion the most beautiful space images fall into five categories: vistas of Earth, our Sun, the rings and moons of Saturn, the shrouds of gas about dying stars and the galaxies.
Since the 1960s, a number of satellites have been put into orbit about Earth to study its weather, ice coverage, vegetation growth, gases in our atmosphere, and temperatures.
Next to the table of contents, “Space” has a wonderful whole page picture of North America, including the Arctic Ocean, Central America, the Caribbean, and northern South America.
An unusual two-page spread shows the entire Earth at night. Many coastal areas are rimmed with light while parts of some continents are dark (central Africa, the Sahara Desert, the eastern interior of equatorial South America, northern Siberia and central Australia). A Pacific typhoon has an uncanny resemblance to a spiral galaxy.
Space telescopes yield solar images in ultraviolet and X-rays that show wild eruptions in our sun’s atmosphere. In the sun’s outer atmosphere (corona) temperatures soar into millions of degrees.
X-ray images show holes in the corona where solar gases stream outward, escaping the sun’s gravity. This is the solar wind that blows past Earth. We are protected from this gaseous flow by the Earth’s magnetic field.
Saturn, the second largest planet has a complex ring system made of icy fragments that orbit Saturn. The other three giant planets also have ring systems, but pale in comparison to Saturn’s bright rings.
Saturn’s rings are likely due to the death spiral of an icy moon towards Saturn; this moon was torn apart by Saturn’s tidal forces and its debris spread into a narrow plane.
The Cassini Saturn orbiter has had a number of close approaches of Enceladus, a modest icy moon of Saturn that ejects dozens of gallons of water steam into space each second.
Since Enceladus receives about 1 percent solar energy per square feet as much sunlight as our moon, this heat of Enceladus must come from within. Could there be reservoirs of heated water within Enceladus holding life?
When most stars exhaust their hydrogen fuel, their balance between outward gas pressure and gravity is broken.
For a small portion of a star’s life, other nuclear reactions provide the needed gas pressure but at a price. The star begins to swell, becoming a red giant star. As the nuclear reactions spread outward, the star’s outer layers begin to pulsate.
Then the outer layers are ejected outward. The remaining core of the star (a white dwarf) is very hot, illuminating the ejected outer layers. Each element gives off special colors, producing a beautiful gauzy array.
Stunning images of these dying stars include the Helix Nebula (of Aquarius), the Cat’s Eye Nebula (Draco) and the Dumbbell Nebula (Vulpecula). Long after our Earth is vaporized, our shrunken sun will have a multicolored shroud of gases.
There are three types of galaxies or star kingdoms; elliptical, irregular and spiral. The spirals are the most picturesque with their twisting centers and trailing spiral arms, laden with hot young stars that illuminate surrounding gas and dust clouds.
Gorgeous spiral galaxies include the nearby Andromeda galaxy, M74 galaxy in Pisces and M33 in Triangulum.
SKY SIGHTS AHEAD: This week the moon glides in front of some dim star groups (Aquarius, Pisces and Aries). The moon appears half full on Jan. 7; for a few days before and afterwards, the lunar craters and mountain ranges are at their best.
Next Saturday evening, the moon will be in Taurus, near the bright star Aldebaran and the Pleiades (7 Sisters) star cluster.
Bob Doyle invites any readers comments and questions. E-mail him at email@example.com . He is available as a speaker on his column topics.