SKA

Two arrays run by one observatory. SKA-Low, in Western Australia: 131,072 log-periodic antennas in 512 stations, 50–350 MHz. SKA-Mid, in South Africa's Karoo: 197 dishes (133 new 15 m dishes plus MeerKAT's 64), 350 MHz–15.4 GHz, on baselinesbaselineThe separation between two antennas of an interferometer, projected onto the plane perpendicular to the source. Long baselines give fine resolution; short ones recover extended emission. up to 150 km. Science: 21 cm tomography of cosmic dawnepoch of reionisationThe period, roughly 150 million to 1 billion years after the Big Bang (z ≈ 20–6), when the first stars and galaxies ionised the neutral hydrogen filling the Universe. Probed by redshifted 21 cm emission and high-z galaxies. and the epoch of reionisation, HI21 cm lineThe 1420 MHz hyperfine line of neutral hydrogen (HI). It traces gas in galaxies; redshifted to lower frequencies, its summed brightness over large volumes (intensity mapping) maps large-scale structure without resolving individual galaxies. in galaxies to high redshiftredshiftz = λ_observed/λ_emitted − 1, the stretching of light by cosmic expansion (or by recession). For distant sources it stands in for distance and look-back time: z ≈ 1 is about 8 Gyr ago, z ≈ 10 about 13.3 Gyr., pulsar timingpulsar timing arrayA set of millisecond pulsars timed for years. Nanohertz gravitational waves perturb pulse arrival times by nanoseconds, correlated between pulsar pairs in a specific way with their separation on the sky (the Hellings–Downs curve). and cosmic magnetism.

Operator

SKAO

Site

Western Australia and Karoo, South Africa

SKA-Low

50 MHz – 350 MHz

SKA-Mid

350 MHz – 15.4 GHz

Science verification

2027 (target)