Looking out for nights on bright Saturn


A unique visual tour of Saturn and its amazing moons is promised when the head of imaging for the Cassini spacecraft, Nasa’s Carolyn Porco, gives three lectures here in the coming week, writes DICK AHLSTROM.

IF YOU FANCY a visit to some place a bit different this summer, how about Saturn? Three guided tours are planned, with late seats available for passengers in Dublin, Cork and Armagh. The nice thing is you won’t have to endure a seven-year journey to the second-largest, and arguably most beautiful, planet in the solar system.

Instead, “passengers” will be taken on a visual guided tour of the Saturn system, including its moons and its dramatic rings. The journey is courtesy of the Cassinisatellite, currently in orbit around the planet and responsible for delivering 100,000 remarkable images of the Saturnian system, explains Nasa’s Dr Carolyn Porco, leader of the Cassiniimaging team.

The Dublin Institute for Advanced Studies, Blackrock Castle Observatory in Cork and the Armagh Planetarium have joined together to bring Porco to Ireland as part of the celebrations of the International Year of Astronomy 2009. The year marks the 400th anniversary since Galileo introduced the telescope as the tool for astronomical study. Porco will give a free public talk at each of the three locations on June 30th, July 3rd and July 8th.

“I will be taking people on a visual tour of Saturn’s system,” she says. The talk will be peppered with dozens of images of the planet’s complex ring system, including the moons Titan and icy Enceladus and a collection of smaller moons.

Porco wants to convey the excitement she and her team experienced as Cassini and its piggy-backed companion satellite, Huygens, sent back pictures and data after arrival at Saturn in 2004. She also hopes to explain how planetary exploration can tell us something “about our perception of ourselves”.

Porco is also the director of Ciclops, the official source of images from the Cassinimission, and was selected as a science consultant for the new Star Trekfilm. She helped the film’s head of visual effects, Roger Guyett, of Industrial Light and Magic, to deliver an accurate representation of the scene showing the Starship Enterpriseas it rises out of the methane fog blanketing Titan, with Saturn and its rings looming large in the background.

The timing of her visit is fortuitous given a new round of important discoveries now arising from the Cassiniproject. The satellite’s nominal mission ended last year after four years in orbit. It was extended, however, as the “Cassini Equinox Mission”, to capture images of Saturn’s rings as the planet approaches its solar equinox, Porco explains.

“The sun is shining at a very low angle to the rings, and on August 11th will be in the ring plane,” she says. “Because the sun’s angle is so low, we can see anything that sticks up above the rings.”

With sunlight striking the rings side-on, anything that projects above the ring plane will cast sharp shadows. Cassini’s cameras are now capturing never-before-seen vertical structures in the ring system, waves stirred up by the tiny 8km-wide moon, Daphnis. Porco likens them to ripples on a pond, but these are exceptional. The debris making up the rings is in a tight band less than 10 metres across, but as Daphnis orbits past, it produces waves at the edge of the ring up to 1,500 metres high.

The disturbed material settles back down, but with the equinox on hand it means Cassini can capture amazing pictures and videos that show the waves forming.

“We have never been at Saturn with such high-resolution equipment when the equinox was upon us. This is a very special time,” she says.

The Cassinimission was made possible by the combined efforts of Nasa, the European Space Agency and the Italian Space Agency, she adds.

“It was really a joint endeavour. It was a demonstration of what humankind can do, regardless of ethnicity or what country you come from.”

The three talks are free but must be booked in advance as space is extremely limited.

Dublin Institute for Advanced Studies, hod@cp.dias.ie, 01-6621333; Blackrock Castle Observatory, info@bco.ie, 021-4357917;

Armagh Planetarium, neil@armaghplanet.com, 048-37523689 in the Republic or 028-37523689 in the North