A European spacecraft has arrived near the sun on what is expected to be one of the most exhaustive examinations of the star ever undertaken.
The Ulysses probe has taken 31/2 years to travel the 93 million miles from Earth to the sun's south pole.Between now and the autumn of 1995, when it's due to pass the north pole, the probe will scrutinize the sun from a totally new perspective: It will be the first time the sun has been observed from pole to pole.
Ulysses was deployed in space from the U.S. shuttle Discovery in October 1990. Its initial course took it away from the sun for 16 months in the direction of Jupiter, until it was deflected by that planet's gravitational shield toward the sun.
The probe is controlled by a team from the European Space Agency and the National Aeronautics and Space Administration based at the Jet Propulsion Laboratory in Pasadena, Calif.
Racing through space at a speed of 93,000 mph, Ulysses already has transmitted useful scientific data back to Earth.
One thing scientists have learned is that the solar winds or dust particles that blow from the solar surface move twice as fast over the south pole as they do over the sun's equator.
The solar winds cause a steady loss of mass - about 2.6 billion pounds per second - in the intensely hot gases that make up the sun.
Nothing is more vital for life on Earth than the sun, which is 861,800 miles in diameter and revolves around its own axis every 27 days. A slight change in the sun's temperature could lead to a new ice age on Earth or cause the polar ice caps to melt and the oceans to overflow.
Scientists have discovered that previous changes in climate were linked to fluctuations in the sun's cycle of activities, which reach a peak every 11 years.
One of the priorities for Ulysses is to examine the sun's magnetic field, which influences the solar cycles as well as the climate on Earth. Another is to search for the source of gamma rays as well as gravity waves, which were first pinpointed in theory by Albert Einstein.
Ulysses also will examine the short-lived but violent outbreaks known as solar flares for clues as to the makeup of particles and the conditions existing in the sun's atmosphere.