The era of the iconic Arecibo telescope is over. This radio telescope in Puerto Rico has not only observed space rocks flying past Earth but also recorded mysterious radio waves from far off galaxies.
Arecibo’s 57-year tenure is over, but its memories will stay on forever. Here are five of this telescope’s best accomplishments that have helped mankind understand space a little better.
Crab Nebula Pulsar
Astronomers had originally considered pulsars to be pulsating white dwarf stars. However, in 1968, Arecibo discovered that the pulsar at the centre of Crab Nebula was flashing after every 33 milliseconds. This was way faster than any known white dwarfs had pulsated. Arecibo’s discovery led to the theory that pulsars were actually neutron stars that were spinning rapidly.
Reborn Pulsars
Arecibo discovered another pulsar, named PSR 1937+21, that was flashing every 1.6 milliseconds. This was faster than Crab Nebula neutron star. This discovery was confusing initially because PSR 1937+21 was older than the Crab Nebula pulsar – but so far, pulsars were thought to flash slower with age. That is when astronomers came to the conclusion that old pulsars can spin faster by siphoning mass from a nearby star. It would then flash every 1-10 milliseconds.
Mercury Ice
Mercury is an unlikely place to find frozen water because it is so close to the sun – and extremely hot. However, at the beginning of the 1990s, Arecibo discovered ice in the craters at Mercury’s north and south poles. These observations were later confirmed by NASA’s spacecraft, MESSENGER. This finding raised the question of whether there could be ice on the moon — and recent discoveries have found there is.
Unveiled Venus
Venus is difficult to map because it is shrouded in a thick layer of atmospheric clouds. However, Arecibo’s radar beams managed to cut through the haze and reach the planet’s surface. This allowed researchers to map Venus’ terrain in the 1970s. In fact, its radar images revealed proof of past volcanic and tectonic activity on the rocky planet.
Mercury’s Revolution
In 1965, a major discovery was made by the Arecibo. Its radar measurements indicated that Mercury rotates on its axis one time in 59 Earth days. It was previously thought to spin every 88 days. This discovery cleared up the mystery of the surface temperature of the planet. If Mercury had actually spun once every 88 days, then only one side of this planet would face the sun. This is because Mercury’s revolution period is 88 days.
