His eyes brimming with excitement, seven-year-old Wang Jun ran to an exhibition stand to pick up a pair of headphones and started listening, leaving his father behind.

　　"The Sound of Pulsar Stars collected by FAST," read a sign next to the stand.

　　FAST, Five-hundred-meter Aperture Spherical Radio Telescope, is the world's largest single-dish radio telescope and was set up two years ago on this day in southwest China's Guizhou Province. It helps scientists understand the universe by receiving and recording pulsar and interstellar signals from extraterrestrial sources.

　　Engineers and astronomers continuously try to perfect the telescope, making improvements to allow it to see farther into space. Meanwhile, those who visit the telescope find themselves in awe of the giant dish and its ability to lead to breakthrough discoveries.

　　SENSITIVE GIANT

　　Since its trial operation in 2016, FAST has found some 50 stars which bear features similar to pulsars, with 44 confirmed, according to scientists in National Astronomical Observatories of China (NAOC).

　　Pulsar observation can be used to conduct research on gravitational waves, black holes and to help solve many other major questions in physics.

　　"We are still improving the system," said Jiang Peng, chief engineer of FAST with NAOC, during Xinhua's recent tour to the FAST observatory. "Now we have met many goals previously set for the telescope."

　　The sensitivity of a telescope is the minimum brightness that it can detect. The lower the number, the farther a telescope can see. In FAST's case, Jiang's team cut the number by 20 percent in the last two years, making it arguably the world's most sensitive telescope.

　　They have also extended its annual observation time from around 700 hours to more than 1,000 hours, which means more data for scientists to analyze.

　　The telescope will start formal operation and open to Chinese astronomers in 2019, according to NAOC.

　　"We often say the telescope was almost usable two years ago; now it is usable, and our goal is to make it good to use," Jiang said.

　　SILENT TOURISM

　　The state-of-art technology and the spectacle of the giant dish have become a magnet for tourists over the years.

　　"My son is interested in science and aliens," said Wang Lifa, Wang Jun's father. "We are here to satisfy his imagination."

　　Wang drove six hours from a neighboring province to Kedu township of Pingtang County, around 15 km away from the mega-telescope. Visitors gather here before they go for a closer view of the giant dish.

　　Tourism took off in the once-impoverished town surrounded by lush forests as wider roads, fancy hotels and bustling shops have sprung up.

　　In the first half of 2018, Pingtang County received 5.13 million visitors, up 40.58 percent. The tourists brought in 550 million yuan (around 80 million U.S. dollars) for the small county, according to the local newspaper Qiannan Daily.

　　The tourist surge has also stoked concerns that it might affect the telescope whose probe results can be compromised by radio signals from electronic devices carried by tourists.

　　Around FAST, a 30-km perimeter was set up as a "silent zone" where the frequencies and radio power are strictly limited.

　　To view the telescope, tourists go to a core zone with a radius of five km around the FAST. Restrictions are even more extreme in that area: no phones, laptops or cameras. Even the GPS system on the ferry to the site is disabled.

　　The local government has also developed plans to curb tourists.

　　Last Thursday, the scenic spot stopped selling onsite tickets for the ferry buses to FAST and museums and moved the operation to an online booking website.

　　The local government restricted the number of tourists to the site to 2,000 per day.

　　"So far, the protection against signal interferences in the core zone has turned out to be effective," said Jiang, the FAST chief engineer.