June 15, 2015

The ring system of Saturn was found to be even more spectacular last week. A team led by Douglas Hamilton of the University of Maryland observed the planet’s giant outer ring using the Spitzer Space Telescope and found it to be even larger than scientists previously thought. They reported their findings in the journal Nature.

This artist’s conception shows a nearly invisible ring around Saturn — the largest of the giant planet’s many rings. It was discovered by NASA’s Spitzer Space Telescope. The artist’s conception simulates an infrared view of the giant ring. Saturn appears as just a small dot from outside the band of ice and dust. The inset shows an enlarged image of Saturn, as seen in infrared light. The ring, stars and wispy clouds are an artist’s representation. (Credit: NASA/JPL-Caltech/Keck)

Saturn’s seven most recognizable rings surround the planet at its equator but do not touch it. They consist mainly of pieces of ice, ranging from dust-sized grains to chunks more than 10 feet (3 meters) in diameter. These rings are named after the letters of the alphabet. The largest and most distant of these rings, the E ring, extends from about 110,000 miles (180,000 kilometers) from the center of Saturn to 300,000 miles (480,000 kilometers) away from the planet.

In 2009, Hamilton and other scientists found a diffuse doughnut-shaped ring far beyond the orbit of the previously known rings using the Spitzer Space Telescope. This year, Hamilton and his colleagues reexamined the ring and were able to better estimate its size and makeup. They found it extended from about 3.7 million miles (6 million kilometers)  to about 10 million miles (16 million kilometers) from Saturn’s surface. They also discovered that the ring is mostly made up of small pieces less than 8 inches (20 centimeters) in diameter, as opposed to the chunkier main rings.

This giant ring may show a strange interaction between two of Saturn’s natural satellites (moons). The ring is centered around the orbit of the moon Phoebe. Scientists suspect that Phoebe released the dust that now forms the giant outer ring. Furthermore, some scientists think that this dust gave another moon its odd coloration. One side of Iapetus is made up of very bright material, while the other side is dark. Its orbit crosses through the Phoebe ring, so dust landing on one side of the satellite may have caused the color differentiation.

Other World Book articles:

• Space exploration
• Astronomy (2003-a Back in Time article)
• Close Encounters with Saturn (a Special Report)

January 8, 2014

Galaxies that had been too faint, small, and ancient to be seen by even the most powerful telescopes made their photo debut yesterday thanks to the Hubble Space Telescope and a strange and violent group of galaxies called Pandora’s Cluster. The images show the 58 galaxies as they appeared some 10 billion years ago, only 4 billion years after the Big Bang, the event that scientists believe created the universe. The newly detected galaxies, which are only several thousand light-years across, are about 100 times as faint as previously discovered ancient galaxies.

Abell 2744, nicknamed Pandora's Cluster, is thought to have a very violent history, having formed from a cosmic pile-up of multiple galaxy clusters. Photo courtesy of NASA.

The images were the first taken by Hubble’s new Frontier Fields program, a three-year survey of the ancient universe using ultraviolet light. Even so, the galaxies would have remained hidden without the magnification provided by Pandora’s Cluster, which lies between Earth and the galaxies. In a phenomenon known as gravitation lensing, the Pandora Cluster acted like a zoom lens. Its gravitational force “bent” the light from the galaxies, focusing and brightening it.

A second team of researchers used data from both Hubble and the Spitzer Space Telescope to estimate the mass of four different ancient galaxies for the first time. The four galaxies are only about 1 percent as massive and 1/20th as large as the Milky Way. But the four, which appear as they did 13.2 billion years ago, are much brighter than scientists had expected. The scientists suggested that the rapid formation of stars in these young galaxies accounts for their brightness.

Additional World Book articles:

• Astronomy
• Inflation theory
• Astronomy Through a Millennium (a special report)
• Seeing the Universe in a Different Light (a special report)
• The Universe on the Grand Scale (a special report)
• When Galaxies Collide (a special report)

July 26, 2013

A new image of Comet ISON taken by the Hubble Space Telescope is giving the public a tantalizing preview of what the deep-space traveler may look like when it makes its maiden voyage around the sun in late November. Some astronomers think the comet could outshine the full moon, rivaling the display put on by the Great Comet of 1860. That comet could be seen during daylight hours without a telescope. However, other researchers caution that the comet could fizzle, the way Comet Kohoutek did in 1973. So-called sungrazing comets like ISON often break up or boil during their perilously close passage by the sun. ISON will zip by the solar surface at a distance of only 724,000 miles (1.16 million kilometers). The comet might not even make it that far, given the hazards of travel through the Main Belt (also known as the Asteroid Belt) and inner solar system. One thing is certain, though–the comet will not crash into Earth.

An image of Comet ISON taken when it was 363 million miles (584 million kilometers) from the sun is actually a mosaic of images that simulates the way the comet would look if we could see with the same resolution as Hubble. NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

Comet ISON was discovered in September 2012 by Russian astronomers while it was between the orbits of Jupiter and Saturn. It is named for the International Scientific Optical Network, a group of observatories in 10 countries. At this point, the nucleus of the comet is is less than 3 miles (5 kilometers) in diameter, though its dusty head is much larger—about 3,100 miles (5,000 kilometers) across. Its tail is an amazing 186,400 miles (300,000 kilometers) long, thanks to the prodigious amount of carbon dioxide escaping from the comet each day. Infrared observations made by American scientists using the Spitzer Space Telescope revealed that 2.2 million pounds (1 million kilograms) of carbon dioxide are “fizzing” away from the “soda-pop” comet daily. ISON is also shedding 120 million pounds (54.4 million kilograms) of dust.

Astronomers believe Comet ISON began its journey toward the sun from the Oort cloud, a cluster of comets, smaller objects, and perhaps even planets in the outermost region of our solar system. Scientists believe comets preserve leftover ice, rock, and dust from the solar system’s formation. As such, they provide valuable information about the history and composition of the solar system.

Additional World Book articles:

• Halley’s comet
• Meteor
• Stardust
• When Worlds and Comets Collide (a special report)