Telescope to record eclipse-like event

Nasa’s flying telescope will capture a rare eclipse-like event from its winter base in Christchurch. The Stratospheric Observatory for Infrared Astronomy (Sofia), a 747-mounted telescope, will capture the ‘‘occultation’’ of Saturn’s largest moon late next month.

This occultation will occur when the moon, Titan, passes in front of a distant bright star.

For a brief time, the moon will cast a moving ‘‘shadow’’ on the Earth’s surface – like how an eclipse of our sun moves a shadow across the Earth’s surface.

If the pilots have their navigation correct, the plane will ‘‘chase down’’ the shadow and fly ‘‘directly in its centre’’.

An animation on Nasa’s website shows the plane intercepting the moving shadow at an angle, rather than flying in lockstep with the shadow, as with some previous occultation captures by Sofia.

Nasa will have ‘‘seconds’’ to collect data, said Bernhard Schulz, deputy director of Sofia science mission operations and a key member of the German partnership within Sofia.

They’re interested in how visible light from the star passes through Titan’s atmosphere.

Titan is the only moon in our solar system with an atmosphere – it’s 95 per cent nitrogen and 5 per cent methane, with trace amounts of organic chemicals containing carbon, hydrogen, oxygen and other elements important to life on Earth.

They’ll be able to probe every layer of the atmosphere, Schulz said in Christchurch last week.

The occultation will also help scientists learn if Titan’s atmosphere changes with the seasons. Titan’s surface has rivers, lakes, oceans and even wetlands of mostly liquid methane and the flow changes as the moon cycles through the seasons.

Sofia will fly 25 missions this winter, as part of a 20+ years science platform costing hundreds of millions.

Nasa contributes the highly modified 747 jet and operations, while the German Aerospace Centre DLR contributes the 2.5-metre telescope and associated filters and devices. Nasa gets about 80 per cent of the telescope’s time and Germany about 20 per cent.

It is cheaper than a satellite or spacecraft, said Nasa’s mission manager Edward Harmon. The Sofia programme also allows scientists to tweak instruments, add new ones and update software. Once blasted off from Earth, satellites and spacecraft are generally on their own.

For example, Nasa and the German DLR will deploy a Highresolution Airborne Wideband Camera Plus (Hawc+) for the first time in the southern hemisphere this winter. It will use polarisation to study celestial magnetic fields.

This season’s Sofia programme will also study the evolution of Eta Carinae, the most luminous and massive stellar system within 10,000 lightyears of Earth. It’s made of two massive stars and expected to explode as a supernova in the future. Sofia will also peer at the Large Magellanic Cloud, which is a satellite galaxy of the Milky Way nearly 200,000 light-years from Earth and only visible from the southern hemisphere.

Vast clouds of dust within it are slowly collapsing to form new stars, which is how our solar system is thought to have formed.

Sofia’s infrared instruments are used to pierce clouds of dust and gas. It can see through the black spots of images produced by the Hubble telescope. Sofia injects more than $5 million into the Canterbury economy in accommodation and costs.