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)

February 27, 2014

The number of known exoplanets in the Milky Way Galaxy has nearly doubled, thanks to a new method of confirming planet candidates discovered by the Kepler space telescope. Mission control officials at NASA‘s Ames Research Center in Moffett Field, California, announced that they had identified 715 new planets, which raises the total number of alien planets to some 1,700. The research has also significantly increased the number of smaller exoplanets. About 95 percent of the new planets are smaller than Neptune, which is about 17 times as massive as Earth. Many exoplanets found previously were at least as massive as Jupiter, which is 318 times as massive as Earth. All of the newly discovered planets orbit one of 305 stars in a multiplanet system like the solar system.

Although Kepler’s original planet-hunting days are over–the telescope has been nonoperational since May 2013–mission scientists are still on the job. The new exoplanets were found in data collected during the telescope’s first two years in orbit, from 2009 to 2011. Kepler’s main mission was to search one section of the Milky Way for Earth-like planets in the “habitable zone.” The habitable zone, also called the Goldilocks zone, is the region around a star that scientists believe is neither too hot nor too cold to support life as we know it. In this zone, the temperature is cool enough to let liquid water form and warm enough to prevent water from freezing. Earth orbits in the habitable zone of the solar system. Although Kepler searched over 150,000 stars for signs of orbiting planets, its search zone was actually quite small. Scientists estimate that the Milky Way alone has up to 200 billion stars.

All of the newly identified planets orbit a star in a multiplanet system, like the solar system. (NASA)

The new method of identifying planets is called validation by multiplicity. This method, which relies on the logic of probability, allows scientists to identify exoplanets in groups, rather than one by one. NASA officials compared the technique to the behavior of lions and lionesses living on the savannah. “In our imaginary savannah, the lions are the Kepler stars and the lionesses are the planet candidates,” the agency explained in a press release. “If you see two of the big cats it could be a lion (star) and a lioness (planet) or two lions. But if more than two large felines are gathered, then it is very likely to be a lion and his pride (star and its planets).”

Additional World Book articles:

• Binary star
• In Search of Other Worlds (a special report)
• Space exploration (2011) (a Back in Time article)

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)

October 17, 2012

Amateur astronomers have discovered an extraordinary planet–one whose skies are illuminated by four suns. The planet, whose discovery was announced this week at an astronomical conference in Reno, Nevada, was named Planet Hunters 1 (PH1). The name refers to the group of volunteers who study data from the Kepler space telescope that NASA has made available to the public on its Planethunters.org website. Two of those volunteers made the discovery, which was confirmed by professional astronomers.

PH1 is located about 5,000 light-years from Earth. (A light-year is the distance light travels in a year, about 5.88 trillion miles or 9.46 trillion kilometers.) Astronomers believe it is a gas giant, larger than Neptune but smaller than Saturn–about six times as wide as Earth. The planet orbits two of the four stars, circling the pair every 138 days. The two stars orbit each other every 20 days.

The other two stars in the system orbit the first pair, but they are located much farther away from the planet–about 93 billion miles (155 billion kilometers). Those other two stars shine in PH1′s sky at certain times of the year, sometimes at night and sometimes during the day.

Extrasolar planets orbit stars other than the sun. In this infrared image of the star HR 8799, three planets orbit the star. The arrows indicate the directions of the planets’ orbits. (C. Marois et. al/NCR Canada)

Two stars that orbit each other are called binary stars. Many of the stars in our solar system belong to such binary systems. Less common are planets that orbit binary stars. Of the hundreds of exoplanets (planets outside of the solar system) discovered so far, only six have been confirmed to orbit binary stars. PH1 is even rarer yet. It is the only planet ever discovered as part of a quadruple star system.

Additional World Book articles:

• Astronomy
• Kepler, Johannes
• Star
• Telescope
• Astronomy 2011 (Back in Time article)
• Space exploration 2009 (Back in Time article)

August 3, 2012

Scientists have gained a powerful new tool for finding and studying black holes and other violent objects that give off high-energy X rays–NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) space observatory. Black holes are regions of space whose gravitational force is so strong that nothing can escape from them. Because black holes trap even light, astronomers cannot see them directly.

Black holes “are sort of the Las Vegas of the universe,” said one scientist. “What happens in a black hole stays inside of a black hole. But on the outskirts of them, that is where there’s tremendous action.” That action occurs when a cloud of gas and dust–or even a star–gets close enough to the black hole to be captured and “eaten.” In the process, the material swirling into the black hole gets so hot that it glows and emits invisible high-energy X rays–the kind used in medicine to image the inside of the body and teeth. This radiation can reveal not only the location of a black hole but also its size. Scientists also plan to study mysterious black hole “burps,” which may be X rays that shoot from black hole if too much material is pulled in at once.

Galaxies appear in much sharper focus in a computer simulation showing NuSTAR’s view of an area of deep space (lower right), compared with an image taken by the European Space Agency’s INTEGRAL satellite (upper left). NuSTAR’s ability to capture high-energy X rays will enable scientists to find individual black holes currently hidden by clouds of dust. (ESA/NASA/JPL-Caltech)

Other targets of the NuSTAR observatory will be supernovae–massive exploding stars that create black holes–and active galaxies–galaxies with supermassive black holes in their nuclei (cores) that give off vast amounts of radiation. Scientists also plan to study the sun‘s atmosphere, which is much hotter than the surface below.

Since the June 14 launch of the $170-million space telescope, NuSTAR’s scientists have been calibrating its instruments and taking test images. Because NuSTAR has more than 100 mirrors for reflecting X rays, it will be able to produce images 10 times as sharp as those from current X-ray telescopes, even the orbiting Chandra X-ray Observatory.

Additional World Book articles:

• Electromagnetic waves
• Space exploration

June 14, 2012

A space observatory designed to search for and study one of the most powerful and mysterious objects in the universe was launched into Earth orbit on June 13. NASA‘s Nuclear Spectroscopic Telescope Array (NuSTAR) will be able to collect the high-energy X rays that surround black holes, regions of space whose gravitational force is so strong that nothing can escape from them. Because black holes are powerful enough to trap even light, astronomers cannot see them directly. But just before a cloud of gas and dust–or even a star–is sucked into a black hole, the material gets so hot that it glows and emits invisible high-energy X rays. Scientists use the rays given off by these doomed objects to identify, measure, and study black holes. Astronomers also plan to use NuSTAR data to study the effects of black holes on their host galaxies.

A supermassive black hole sucks in a swirling disk of matter, shooting out beams of particles, in this artist’s conception. (NASA)

The NuSTAR observatory includes the first focusing telescopes that will be able to image the sky in the high-energy X-ray region of the electromagnetic spectrum. Because of this ability to focus, the images NuSTAR produces will be 10 times as sharp as images from current X-ray telescopes, even the orbiting Chandra X-ray Observatory. NuSTAR’s instruments will be able to see through clouds of gas and dust that block low-energy X rays.

NuStar’s mission also includes gathering data on other high-energy-emitting targets (objects that give off high-energy X rays). Among them are supernovae, massive exploding stars that create all of the chemical elements heavier than the two lightest elements–hydrogen and helium–including iron, gold, and uranium. Astronomers also planned to investigate active galaxies, galaxies that give off vast amounts of radiation from their nuclei (cores).

NuSTAR (NASA/JPL-Caltech)

NuSTAR was launched in mid-air from a L-101 Stargazer aircraft atop a Pegasus XL rocket built by Orbital Sciences, a private company based in Dulles, Virginia. Such airborne launches require less fuel than a traditional surface take-off. The NuSTAR mission is part of NASA’s Small Explorer class of low-budget space flights.

Additional World Book articles:

• Astronomy
• Electromagnetic waves
• Space exploration

Feb. 24, 2012

Russian scientists are beginning to examine the first images made by their country’s new RadioAstron space telescope, now the largest space telescope in Earth orbit. Launched with little fanfare in July 2011, the radio telescope has a collecting dish 33 feet (10 meters) wide. By comparison, the collecting mirror aboard the Hubble Space Telescope is 8 feet (2.4 meters) wide. The RadioAstron space telescope is funded and run by Russia’s Astro Space Center in Moscow and is part of an international network of ground-based radio telescopes spread around the world. The new space telescope will help astronomers view such objects as supermassive black holes in the center of distant galaxies, cosmic rays, dark matter, neutron stars, and new planetary systems. The telescope began science operations in December 2011.

Radio telescopes collect and measure faint radio waves given off by objects in space. Instead of the mirrors and lenses used in optical telescopes, radio telescopes use a large dish that looks much like a satellite dish. Numerous radio telescopes can be linked together, a technique called interferometry. With this technique, scientists can create a telescope equal to the distance between the telescopes. For example, a network of telescopes spread around Earth would have the power of one telescope with a dish the diameter of Earth, about 8,000 miles (12,800 kilometers) wide. The RadioAstron space telescope travels in a highly elliptical (oval) orbit around Earth. This orbit takes the satellite as far away as 240,000 miles (390,000 kilometers). At that distance, the linked telescopes have the power of one dish 240,000 miles wide–about the distance from Earth to the moon.

An astronomer studies an image produced by the Expanded Very Large Array of radio telescopes at Socorro, New Mexico. The colors in the "painting" represent different amounts of radio energy sent out by objects in the sky. National Radio Astronomy Observatory

 

Additional World Book articles:

• Astronomy
• Green Bank Telescope
• National Radio Astronomy Observatory
• Telescopes: 400 Years of Stargazing (A Special Report)

 

Jan. 13, 2012

Planets orbiting stars other than the sun may be the rule rather the exception, an international team of scientists has reported. In fact, the Milky Way alone–an average-sized galaxy among the billions of galaxies in the universe–probably contains at least 160 billion planets. And even that, the scientists said, is a conservative estimate.

The scientists reached that number after making a statistical analysis of planets found using gravitational lensing, one of the main methods for hunting for extrasolar planets. They calculated that each star in the Milky Way has an average of 1.6 planets. Then they multiplied this number by the 100 billion stars estimated to belong to the Milky Way. Gravitational lensing, however, is not useful for finding exoplanets less than five times larger than Earth. Nor is it especially useful for finding planets that orbit closer to their star than Venus or farther from their star than Saturn. So the total number of alien planets is certainly much higher.

Three rocky planets smaller than Earth--the first alien planets that small found outside the solar system--have been found orbiting a red dwarf about 120 light-years from Earth. The smallest of the three planets (foreground), which is about the size of Mars, actually orbits the farthest from the star. NASA/JPL-Caltech

Evidence for that conclusion was the discovery of the first exoplanets smaller than Earth outside the solar system. Astronomers studying data imaged by the Kepler space telescope found the three rocky planets about 120 light-years from Earth. One of the planets is about the size of Mars, about half the size of Earth. All three orbit so close to their star, a red dwarf, that their sizzling surface temperatures rule out the existence of life as we know it. The Kepler scientists said the galaxy might have many more small planets than it has large planets. Astronomer John Johnson, one of the authors of the study, said that small exoplanets were “kind of like cockroaches. If you see one, then there are dozens hiding.”

Additional World Book articles:

• Back in Time (Astronomy 1996)
• Back in Time (Astronomy 1999)
• COROT
• In Search of Other Worlds (A Special Report)
• Kepler, Johannes
• Transit

The discovery of a planet that orbits two stars-an arrangement that some scientists previously thought existed only in science fiction-was announced by astronomers at NASA‘s Ames Research Center in Mountain View, California. Kepler space telescope detected the planet, which scientists named Kepler-16b. The research team uses data from the telescope, which measures dips in the brightness of more than 150,000 stars, to search for transiting planets. (A transiting planet is a celestial body that moves across the face of another celestial body, hiding a small part of it.) Kepler-16b is about 200 light years from Earth and about the size of Saturn. Astronomers believe that Kepler-16b is gaseous and too cold to harbor life. It orbits the two stars in 229 days. The stars in turn circle each other.

“This discovery confirms a new class of planetary systems that could harbor life,” notes Kepler astronomer William Borucki. “Given that most stars in our galaxy are part of a binary (two star) system, this means the opportunities for life are much broader than if planets form only around single stars. This milestone discovery confirms a theory that scientists have had for decades but could not prove until now.”

Additional World Book articles:

• Astronomy
• Kepler, Johannes
• Hubble Space Telescope