PLANET NEWS FROM NEAR AND FAR
Astronomers have been busy booting Pluto out of the solar system, finding a new planet orbiting a nearby star, and exploring a crater on Mars

by Terence Dickinson, SkyNews Editor

Astronomers have been busy lately. A major astronomical meeting in late August was the scene of the now-famous dumping of Pluto as a full-fledged planet of the solar system. Pluto, they said, was much too small for it to properly qualify as a planet. More crucially though, the scientists said that other similar-sized bodies had been found orbiting the Sun in the same vicinity as Pluto--one of them slightly larger than Pluto. Rather than designate that object a planet too, the final decision was to demote Pluto and reduce the planet count from nine to eight.

Astronomers have been busy lately. A major astronomical meeting in late August was the scene of the now-famous dumping of Pluto as a full-fledged planet of the solar system. Pluto, they said, was much too small for it to properly qualify as a planet. More crucially though, the scientists said that other similar-sized bodies had been found orbiting the Sun in the same vicinity as Pluto--one of them slightly larger than Pluto. Rather than designate that object a planet too, the final decision was to demote Pluto and reduce the planet count from nine to eight.

Also on the planet front, just last week astronomers using the Hubble Space Telescope announced that they had gathered definitive evidence for the existence of the nearest planet beyond our solar system. It’s a Jupiter-sized world that orbits the Sun-like star Epsilon Eridani, which is 10.5 light-years (approximately 100 trillion kilometres) from Earth. That may sound far away, but it’s next door in astronomical terms.

The as-yet unnamed planet is calculated to be slightly larger than Jupiter with about 1.5 times Jupiter's mass. It orbits once around its parent star, Epsilon Eridani, every 6.9 years, compared to 11.9 years for years for Jupiter to circle the Sun.

The Hubble observations show that the planet's orbit is tilted 30 degrees to our line of sight, which is the same inclination as a disk of dust and gas that also encircles Epsilon Eridani. This is a particularly exciting result because, although it has long been inferred that planets form from such disks, this is the first time that a planet and the remnants of such a disk have been observed around the same star.

The planets in our solar system share a common alignment in a flat plane--evidence that they were created at the same time in the Sun’s primordial disk. But the Sun is a middle-aged star some 4.5 billion years old, and its debris disk dissipated long ago. Epsilon Eridani, however, still retains its disk because it is young, only 800 million years old.

Astronomers originally detected the planet in 2000 by measurements that were interpreted as a rhythmic, back-and-forth wobble in Epsilon Eridani caused by the gravitational tug of an unseen planet. However some astronomers wondered if in fact there might be some other reason for the wobble. The Hubble observations have settled any uncertainty, making this the closest so-called extrasolar planet (planet of another star) to our sun.

Although the Hubble Space Telescope and other telescopes have not taken a picture of the planet, the evidence for its existence was gathered by tracking changes in the star’s wobbling motion. However, astronomers hope to snap pictures of it in 2007, when its orbit is closest to Epsilon Eridani. Then the planet may be bright enough in reflected starlight to be imaged by Hubble or large ground-based telescopes.

Meanwhile, another group of researchers at mission control for NASA’s robotic Martian rovers were making news of their own much closer to home on our planetary neighbour Mars. After more than two years driving the solar-power rovers Spirit and Opportunity around the desert planet, scientists said last week that they were plotting how to navigate the rover Opportunity down into Victoria Crater, a deep and geologically interesting structure, probably more than a billion years old.

The six-wheel robot has spent its first week at Victoria crater acting like a tourist, snapping pictures of the kilometre-wide jagged pit filled with cliffs of thickly layered rocks which undoubtedly hold clues about the Martian past. For scientists, an exciting new dimension to the mission is new aerial images of the craters mapped by the Mars Reconnaissance Orbiter, which has just become operational. In one image, the rover appeared as a speck with its wheel tracks visible in the soil.

This kind of technological achievement on other worlds is not exactly routine, but you don’t hear much about it in the mainstream news either. The idea is that by studying close-ups of the rover's surroundings using aerial shots taken by the orbiter, scientists hope to zero in on the safest route for the rover to enter the big crater and probe the inner walls--before the vehicle konks out. Both rovers were designed to last six months and they are still working after more than 30 months on Mars.

A preliminary analysis of the pictures seen so far shows distinct patterns in the sedimentary rock layers in the crater, suggesting the area experienced a fluctuating climate--sometimes watery, sometimes dry--scientists said. Opportunity and its twin, Spirit, have both uncovered geologic evidence of past water activity on the planet. The question remains: How long was water in liquid form on the planet, and what happened to it? Mars is now dust-dry. Is this the long-term fate of Earth? Can Mars tell us anything about the destiny of our own planet?

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Constellation Watch
By Todd Carlson, Assistant Editor

The most famous constellations visible in the autumn—Capricornus, Aquarius and Pisces—tend to be among the least prominent in the sky. Constellations such as Orion and Taurus, seen in the winter, or Scorpius and Sagittarius found in the summer, have dominant stars that make identification easy.

Not only are the stars of these famous constellations dim, but they don’t link together into a shape that looks like their namesakes. Over the years I have created my own visual representations of some constellations which help me to identify them.

Capricornus is a perfect example of a constellation which is difficult to identify. While it may be a goat in mythology, to me it appears to be kite-shaped, with the top pointed towards the horizon. Editor Terence Dickinson says it looks to him like an upside-down Napoleon hat.

To the left of Capricornus is Aquarius, the water bearer. Once you identify the jugs of water held at the end of a stick, the visual appearance of this grouping might get a passing grade as somewhat matching its water bearer description.

Pisces, the fish, looks more like a tadpole and is found to the left of Aquarius. The key to locating Pisces is identifying the Circlet, an asterism (grouping of stars) at the head of the constellation. From its head, a trail of stars flow eastward, creating the tadpole’s tail.

The lesson in this is that you can personalize the sky by memorizing the constellations in your own way. A beginner may not see a goat, a bull or a whale. But the grouping of stars that forms the form a constellation can be personalized in a way the makes the night sky easy to navigate.

Click HERE for an image showing where to locate Capricorn, Aquarius and Pisces.


Planetary Roundup

Saturn rises near 3:00 a.m. in October in the constellation Leo and can be seen high in the eastern sky at dawn. On the morning of October 16, the 24-day old Moon is near Saturn.

Jupiter, Mars, Venus and Mercury are all hidden by the glare of the Sun and are not visible.

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SkyNews Observer's Guide

Is there an aurora occurring tonight? What special events are happening in the night sky this week? Looking for reviews of the latest telescope? Visit www.skynews.ca for all your astronomy needs—news, product reviews, satellite transit times, Photo of the Week, aurora monitoring and more!

In the November/December 2006 issue of SkyNews:

• SkyNews reviews two new apochromatic refractors from William Optics.
• Exploring the Night Sky by Alan Dyer.
• Scoping the Sky by Ken Hewitt-White.
• Astrophotography or Sleep? A personal guide to getting your astronomy fix without losing sleep.
• Christmas gift ideas for the backyard astronomer.
• Readers’ Gallery.
• And more!

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