Chinese astronomers have discovered a rare compact binary system consisting of a millisecond pulsar and a companion helium star formed by common envelope evolution, which sheds light on future research on stellar evolution theory.
The research, conducted by a team led by professor Han Jinlin from the National Astronomical Observatories of the Chinese Academy of Sciences using China's Five-hundred-meter Aperture Spherical Radio Telescope (FAST), was published on Science online on Thursday.
Pulsars are spinning neutron stars that originate from the imploded cores of massive dying stars through supernova explosions. They emit twin beams of radio waves from their magnetic poles. These beams appear to pulse because astronomers see them only when a pulsar pole is pointed at Earth.
Thanks to the high sensitivity and detection abilities of FAST, the Chinese team identified a pulsar with a spin period of 10.55 milliseconds in a compact binary system, which has an orbit radius of 500,000 kilometers and an orbital period of 3.60 hours.
The companion star has 1.0 to 1.6 solar masses, eclipses the pulsar for about 17 percent of the orbit, and is undetected at other wavelengths, so it is most likely a stripped helium star.
The scientists interpret this system as having recently undergone a common envelope phase, thus producing a compact binary.
Such binary systems are very rare and hard to detect, because they only exist for about 10 million years. The team estimates only dozens of other examples of this system may exist in the entire galaxy.
This discovery is of great significance to the study of stellar evolution, physics of accretion onto compact stars, and gravitational-wave sources from mergers of binary stars.
FAST, the world's largest filled-aperture and most sensitive radio telescope, is located in a naturally deep and round karst depression in southwest China's Guizhou Province. It started formal operations in January 2020 and was officially opened to the world in March 2021.
Chinese astronomers discover rare compact binary system of pulsar, helium star
Chinese astronomers discover rare compact binary system of pulsar, helium star
Chinese astronomers discover rare compact binary system of pulsar, helium star
Ethiopian coffee, famous for its unique flavor, is quickly gaining ground in the Chinese market, and producers hope to further propel exports by leveraging China's newly implemented zero-tariff measures.
China's zero-tariff policy for all 53 African countries with which it has diplomatic relations takes effect on Friday, marking a new stage for China-Africa economic and trade cooperation.
For Ethiopia, the policy opens a timely growth avenue. The country ranks among the top five global coffee producers, and China has already emerged as its fourth-largest export market.
Finette, a coffee trader from the east African country, recently traveled to China to visit a coffee processing company in central China's Henan Province. During the trip, she hopes to establish a more stable and in-depth cooperative relationship this and other Chinese companies.
"I came here be because this company is a key buyer of green (coffee) beans from Ethiopia. I also come here for displaying Ethiopian traditional culture, information sharing. I'm the delegate of coffee trading company in Ethiopia. I hope more and more Chinese can drink coffee, drink the original Ethiopian coffee," said Finette.
On Thursday, the first branded store in China specializing in African coffee officially opened inside Zhengzhou Airport, a major import hub in the country's eastern region. The store is run by Huichuan Industrial Development Company, which has cooperated directly with Ethiopia and invested 300 million yuan (about 43.9 million US dollars) in the construction of a coffee processing industrial demonstration park in 2020.
"We already have more than a dozen varieties of African coffee on display here. We want to make high-quality African coffee a local specialty of Henan and bring it to more friends from other places," said Lu Ying, deputy general manager of the company.
Ethiopia's blooming coffee trade is part of a larger story. Trade between China and Africa has reached a record high for five consecutive years and is expected to exceed 300 billion US dollars for the first time in 2025. China has remained Africa's largest trading partner for 17 consecutive years. Over the past five years, China's annual imports of agricultural products from Africa have averaged over 5 billion US dollars.
"Since China expanded cooperation through unilateral openness, more and more African agricultural products have entered the Chinese market, such as Ethiopian coffee, Egyptian citrus fruits, South African pecans, and Kenyan avocados. This is partly due to China's expanding zero-tariff policy towards the least developed African countries, and partly a result of cooperation between relevant government departments and enterprises,” said Jing Ning, deputy director of the Department of West Asian and African Affairs under the Ministry of Commerce.
Ethiopian coffee gains momentum in China as zero-tariff policy takes effect
