Cluster satellites study the effects of solar wind
Science & Exploration

20 May

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ESA / Science & Exploration / Space Science

2003: On 20 May 2003, ESA announced that its four Cluster spacecraft had made a remarkable set of observations that led to a breakthrough in understanding the origin of a peculiar and puzzling type of aurora.

These aurorae - seen as bright spots in Earth's atmosphere and called 'dayside proton auroral spots' - occur when fractures appear in the Earth’s magnetic field, allowing particles given out from the Sun to squirt through and collide with the molecules in our atmosphere. This was the first time that a precise and direct connection between the two events had been made.

Polar plumes as seen by SOHO
Polar plumes as seen by SOHO

2003: On 20 May 2003, ESA's SOHO team announced findings that may overturn previous ideas about the origin of the 'fast' solar wind, which occurs in most of the space around the Sun.

Earlier results from SOHO established that the gas of the fast wind leaks through magnetic barriers near the Sun's visible surface. Straight, spoke-like features called plumes have also been seen rising from the solar atmosphere at the polar regions, where much of the fast wind comes from. According to previous ideas, the gas of the fast wind streams out in the gaps between the plumes.

Careful observations with SOHO now suggest that most of the fast wind leaves the Sun via the plumes themselves, which are denser than their surroundings. The SOHO team tracked gas rising at about 60 kilometres per second to a height of 250 000 kilometres above the Sun's visible surface.

Hubble's first image
Hubble's first image

1990: On 20 May 1990, ESA's Faint Object Camera aboard the NASA/ESA Hubble Space Telescope successfully took its first engineering test pictures.

This picture for the Faint Object Camera was the culmination of several weeks of intensive check-out and testing of the camera, following the launch of the Hubble Space Telescope on 24 April 1990.

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