[ad_1]
After two accidents, one of the largest radio telescopes in the world is so badly damaged that repair is no longer an option. Astronomers are losing an instrument that has withstood many storms.
The Arecibo telescope in a November photo. The hole that a suspension rope tore in the bowl is clearly visible.
One of the most famous radio telescopes in the world closes its doors. As the American National Science Foundation announced Thursday, the Arecibo telescope in Puerto Rico can no longer be saved after two carrier cables break. After an investigation, those responsible came to the conclusion that workers could not be expected to take the risk of repairing the severely damaged telescope.
A popular film subject
The telescope was put into operation in 1963. With its 305-meter bowl, it was the largest single telescope in the world until a few years ago. He made revolutionary discoveries. For example, the first radar map of Venus was created with its help. The telescope had a legendary reputation not only among astronomers. Even the directors have succumbed to its charm. It was used as a backdrop in the James Bond film “Golden Eye” and the science fiction thriller “Contact”.
The Arecibo telescope consists of the radio bowl and a 900 ton instrument platform which is supported by 18 steel cables and hovers 150 meters above the bowl. On August 10, one of these cables broke away from its holder and tore the bowl to a length of 30 meters. Since the supporting structure was still stable, it was decided to replace the cable. But then there was another accident. During the inspection work on November 6, one of the main cables ripped and shattered a large segment of the bowl.
It was concerning that the cable was only loaded to 60% of its maximum carrying capacity at the time of the accident. This raised concerns that even the intact cables might be weaker than expected. Given the risk of the instrument’s entire platform crashing into the bowl, the National Science Foundation decided not to repair with a heavy heart. The telescope must now be disassembled. How long it will take and how high the costs are is still unclear.
A child of the Second World War
The Arecibo telescope owes its creation to military considerations. As part of the “Defender” project, after World War II, the United States considered building a protective shield against ballistic missiles with nuclear warheads. Radar antennas should be used that detect rockets as they enter the atmosphere. However, it quickly became clear that too little was known about the upper atmosphere, the so-called ionosphere. The Arecibo telescope should deliver these results. At the same time, it should offer astronomers the opportunity to explore space using radio waves.
The successes were not long in coming. In 1967, astronomers discovered that Mercury rotated around its axis faster than previously thought. Seven years later, Russell Hulse and Joseph Taylor used the telescope to discover a pulsar which, together with a neutron star, forms a binary star system. Based on the decreasing orbital period, the two astronomers were able to indirectly prove that the two objects – as predicted by Albert Einstein – emit gravitational waves. For this, the discoverers were awarded the Nobel Prize in Physics in 1993.
What many don’t know: the first exoplanets were also tracked down with the Arecibo telescope, three years before the revolutionary discovery by Swiss astronomers Didier Queloz and Michel Mayor. However, because the three planets orbit a pulsar, they have not received the same attention as planet 51 Pegasi b, which orbits a sun-like star.
The Arecibo message was sent in 1974.
Over the years, the Arecibo telescope has also contributed several times to the search for extraterrestrial intelligence. Many of the signals that the volunteers analyzed within the Seti @ home project were recorded with this telescope. And only once did the telescope not stop listening. In 1974 the famous message of Arecibo was sent. In encrypted form, it contains information about our solar system, the earth and its inhabitants. The recipient was a star cluster in the Milky Way, 25,000 light-years from us.
In the nearly 60-year history of the Arecibo telescope, there have been many highlights and setbacks. The telescope has had to survive several hurricanes in recent years. Hurricane “Maria” was particularly violent in 2017. At that time, an instrument broke off the platform and damaged the bowl. The damage was limited.
At the turn of the year 2019/20, the telescope was then shaken by several earthquakes. The strongest had a magnitude of 6.4. But only the two cable breaks finally brought the telescope to its knees.
Follow the NZZ science bench Twitter.
[ad_2]
Source link
