The Laser Interferometer Space Antenna (LISA) is launched
The Laser Interferometer Space Antenna (LISA) is a gravitational wave observatory launched by the European Space Agency.** This project is the third of three L-class (Large) missions in the "Cosmic Vision" programme which includes two other spacecraft – the Jupiter Icy Moon Explorer (JUICE) launched in 2022* and the Advanced Telescope for High ENergy Astrophysics (ATHENA) deployed in 2028.*
LISA is designed to sense gravitational waves – tiny ripples in the fabric of space-time – with extreme precision. Three spacecraft are placed in a triangular formation with 5 million kilometre sides, flying along an Earth-like heliocentric orbit. Laser interferometry is used to monitor fluctuations in the relative distances between them, with a resolution of just 20 picometres (20 trillionths of a metre, or smaller than a helium atom).*
To eliminate non-gravitational forces such as light pressure and solar wind on the test masses, each spacecraft is constructed as a zero-drag satellite and effectively "floats" around the masses, using capacitive sensing to determine their relative position, with ultra-precise thrusters to remain properly centred at all times.
Previous searches for gravitational waves in space were conducted for short periods by planetary missions with other primary objectives (such as Cassini–Huygens), using microwave Doppler tracking to monitor fluctuations in the Earth-spacecraft distance. By contrast, LISA is a dedicated mission using laser interferometry to achieve a much higher sensitivity. Other antennas had been operational on Earth, but their sensitivity at low frequencies was limited by the largest practical arm lengths, seismic noise, and interference from nearby moving masses.
Passing gravitational waves alternately squeeze and stretch objects by a tiny amount. These waves are caused by energetic events in the Universe, such as massive black holes merging at the centre of galaxies; black holes consuming small compact objects like neutron stars and white dwarfs; supernova star explosions; remnants from the very early phase of the Big Bang and possibly theoretical objects like cosmic strings and domain boundaries.
Since LISA is the first dedicated, space-based gravitational wave detector, the mission adds a whole new sense to our perception of the Universe – enabling astronomers to "hear" events in ways not possible before and revealing many important phenomena that were previously invisible.
phases out nuclear energy
Fukushima disaster in Japan, questions were raised about the long-term
viability of nuclear power. Switzerland was among the countries to abandon
this form of energy production, following public protests and a government
review in 2011. The country’s five existing reactors – supplying
about 40% of the country’s power – were allowed to continue
operating, but were not replaced at the end of their life span. The
last plant would be taken offline in 2034.*
A nuclear power
station with a cooling tower in Leibstadt, Switzerland.