14 DAY TRIAL // Data provided by Ulysses spacecraft indicates that the Sun's hot-particle wind is less powerful and emanates less heat than at any previously recorded date since humankind began its space race in the 1950s.
During a more tranquil period of the Sun's activity, the Ulysses spacecraft has been able to measure its low winds (the constant high-speed jet of particles emitted by the Sun at a speed of 1 billion mph – 1.6 billion km/h), which form the solar weather that has so much impact on Earth and the rest of the system's planets. Normally, the charged particles of the solar wind keep Earth protected by cosmic rays from the distant stars of the galaxy, literally enveloping our planet in a defensive bubble (the heliosphere). As such, it is clear that the reduced power exhibited by the current solar wind level may eventually prove harmful to terrestrials.
The data showed that the solar wind level is 20 to 25% lower than the previously recorded minimum, both in density and pressure, which may mean that future levels might be even lower. Nancy Crooker, physicist at Boston University in Massachusetts stated, "We know that the sun has been this cool before, this inactive before. But that was prior to the Space Age, so we didn't have actual physical measurements until now. [...] It's a big deal. It's the first time we've measured these conditions. It's expanding our horizons of what we can do and compare."
The Ulysses probe has traded its own life for the opportunity to make this discovery; it has dedicated all of its 18 years (4 times more than its predicted lifetime) to measuring the solar wind progression and regression during the eleven-year activity cycle of the Sun. During this period, it was able to record two solar wind minimums and one maximum. After its radioisotope thermoelectric generators will not be able to keep the hydrazine fuel from freezing anymore, the probe will eventually die somewhere in the cold space.