Saturn a magnificent sight in evening sky

Astronomers would agree: The most magnificent sight to view through a telescope is the planet Saturn

Astronomers would agree: The most magnificent sight to view through a telescope is the planet Saturn. Its planetary globe, encircled by its unique rings, can be easily seen by using any beginner’s telescope on today’s market. During the evening hours this spring, the Ringed World is well-positioned halfway up the sky in the south, making it practically an effortless target.

Saturn has been known since antiquity, but only as a “star” wandering very slowly among the constellations. In fact, it is the most sluggish of the five “wandering stars” that are visible to the naked eye. The ancient Greeks called these celestial drifters “planets.”

A small telescope will show the five naked-eye planets as more than points of light and, with adequate magnification, these worlds become colored shapes. Saturn, however, is matchless in its telescopic appearance. Its exceptional set of rings easily distinguishes it from all the other planets of our solar system.

Mysterious rings

Galileo was almost able to recognize Saturn’s rings with his homemade telescope, but its quality could not adequately separate the rings from the planet. Instead, Galileo saw Saturn as a world with mysterious side lobes — a coffee cup handle on each side — that he called “ansa.”

Galileo never solved the mystery of Saturn’s rings and it puzzled him throughout his life. Subsequent observers also failed to discern the rings, some describing Saturn as emitting vapors that produced an elongated appearance where the mist reflected sunlight. Another said that the lobes could be explained by the presence of two large, dark moons close to the planet and two bright moons farther out.

The correct explanation was given in 1659, when Christian Huygens, after four years of observing Saturn with a telescope that was slightly better than Galileo’s instrument, concluded: “The planet is surrounded by a thin, flat ring, nowhere touching the planet.”

Amateur telescopes will show that Saturn’s rings have three basic sections, prosaically named the A, B and C ring, in approaching distance to the planet. In 1675, astronomer Giovanni Cassini discovered a dark lane between the A and B rings. Now called the Cassini Division, it is a gap between these two ring segments and can be easily seen when viewed through an amateur telescope.

The discovery of a division in the rings cast doubt on the then-prevailing theory that Saturn’s rings were liquid or solid. That uncertainty was compounded in 1837, when the director of the Berlin Observatory, Johann Encke, found a much less prominent separation in Saturn’s A-ring.

Today, we know that the rings are made of countless icy objects ranging in size from tiny grains to rocks and boulders to house-sized masses, all encircling Saturn. Spacecraft investigations near Saturn have found additional rings that are only discernible from space.

Intriguing moon

Unlike the planet Jupiter, with four major moons orbiting it, Saturn has only one substantial natural satellite, its moon Titan. This moon is not only one of the largest planetary satellites in our solar system but is also the only moon with a substantial atmosphere.

Because of its considerable diameter for a moon, it is no surprise that Titan was the first Saturnian moon to be discovered. First reported by Christian Huygens in 1655, Titan can be seen through an amateur telescope; its appearance is definitely non-stellar, that is, it can be distinguished as an object rather than a point of light.

The last hundred years of observations have shown us that Titan is the most intriguing of all the moons in the solar system because of its significant atmosphere. The first indication of an atmosphere came early in the 20th century when astronomers were first able to notice that there was considerable darkening on the limb of Titan.

In the 1940s, University of Chicago astronomer Gerard Kuiper analyzed the light reflecting from Titan and found that there was the greenhouse gas methane in its atmosphere. When the Voyager 1 planetary probe flew by Saturn in 1980, it found that Titan’s atmosphere was almost entirely nitrogen and that methane only composed 1 percent of it, primarily in the upper atmosphere — that’s how Kuiper was able to detect it. This makes Titan and Earth the only solar system bodies to have a nitrogen-rich atmosphere. Titan’s atmosphere, however, exists at a temperature of only 93 degrees above absolute zero!

The most recent observations of Saturn and its moons come from the Cassini mission spacecraft that is currently operating in orbit around the planet. In January 2005, the Cassini craft released a probe into the atmosphere of Titan. After a two-and-a-half hour descent, the probe landed on the surface of Titan. It found that Titan has a “methane cycle” similar to the water cycle on Earth. Liquid methane on the surface evaporates, condenses in Titan’s atmosphere and then rains down onto the surface.

April sky

Saturn’s slow progress against the starry background means that it will be well-placed for observing though early summer this year. By mid-evenings in April, the planet is more than halfway up the sky in the southeast and by late evening, the Ringed Planet is at its highest in the south.

Saturn is plainly visible as an extra “star” in the constellation of Leo the lion. The planet is just east of the bright star Regulus, the star that symbolizes the lion’s heart. Regulus is also considered to be the “dot” of the backward question mark of stars that forms Leo’s head and mane. Watch for the moon near Saturn on April 14 and 15.

Also in the evening sky is Mars. The Red Planet still has considerable altitude in the west as the sky gets dark but continues to fade throughout April. Mars is now in the middle of Gemini and currently sets in the northwest a little before 3 a.m. A waxing crescent moon will be seen with Mars on April 11.

Jupiter is the target for the morning sky. This enormous planet is the very bright “star” in the southeast in the hours before sunrise.

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