Launched in 1990, the Ulysses spacecraft is in a highly elliptical orbit that takes it over the poles of our Sun. It has made the first-ever extensive set of observations of the Sun's polar regions over a long period of time.
Launched in 1995, SOHO co-rotates with the Earth around the Sun at a virtual point between the Sun and the Earth at a distance of 1.5 million kilometres from the Earth. From here SOHO can continuously observe the Sun. Its instruments are designed to investigate the Sun from its core outward to the surface, atmosphere, corona and solar wind.
|Volumetric mean radius||km||696 000||109.2|
|Mass (×1024)||kg||1 989 100||333 000|
|Volume (×1012)||km3||1 412 000||1 304 000|
|Surface gravity at the equator||ms2||274.0||28.0|
|Mass conversion rate (×106)||kgs-1||4300|
|Mean energy production (×10-3)||J kg-1||0.1937|
|Surface emission (×106)||Wm-2||63.29|
|Spectral type||G2 V|
|Rotation period at equator||d||25.6||25.6|
|Rotation period 60° latitude||d||30.9||30.9|