NASA's "flying" telescope aboard a highly modified Boeing 747SP jetliner has begun its fourth series of science flights to study planets, asteroids and nearby galaxies.

This operational period known as "Cycle 4" is a one-year-long observing period in which the telescope, the Stratospheric Observatory for Infrared Astronomy (SOFIA), is scheduled for 106 flights between now and the end of January 2017.

"The Cycle 4 programme will make more than 550 hours of observations," said Pamela Marcum, NASA's SOFIA Project Scientist.

"We'll be studying objects spanning the full gamut of astronomical topics including planets, moons, asteroids and comets in our solar system; star and planet formation; extrasolar planets and the evolution of planetary systems; the interstellar medium and interstellar chemistry; the nucleus of the Milky Way galaxy, and nearby normal and active galaxies," said  Marcum said.

SOFIA's instruments observe infrared energy – one part of the electromagnetic spectrum, which includes visible light, X-rays, radio waves and others.

Many objects in space, for example newborn stars, emit almost all their energy at infrared wavelengths and are undetectable when observed in ordinary visible light.

In other cases, clouds of gas and dust in space block visible light objects but allow infrared energy to reach Earth. In both situations, the celestial objects of interest can only be studied using infrared facilities like SOFIA.

"During the February third flight, the target objects ranged from a young planetary system around the naked-eye star Vega, only 25 light years from us, to an infant star 1,500 light years away in the Orion star forming region," said Erick Young, SOFIA's Science Mission Operations Director.

"We also observed a supermassive black hole hidden behind dense dust clouds in the centre of a galaxy 170 million light years away," Young said.

Scientists from the University of Georgia, University of Arizona, University of Texas at San Antonio, and the Space Telescope Science Institute in Baltimore, obtained data using the Faint Object Infrared Camera for the SOFIA Telescope (FORCAST) mounted on SOFIA's telescope for imaging and spectroscopic observations during the flight.

In Cycle 4, the SOFIA observatory is scheduled to deploy to the Southern Hemisphere for seven weeks in June and July this year, with 24 science flights planned from a base at New Zealand.

Scientists will observe areas of interest such as the Galactic Centre and other parts of the Milky Way that are difficult to observe from the Northern Hemisphere.

The far-infrared High-resolution Airborne Wideband Camera-plus (HAWC+) will be added to SOFIA's suite of seven cameras, spectrometers, and high-speed photometers during the latter part of Cycle 4.