Stargazing Through the Clouds: Students Chase Venus on a July Night
One participant tries to see Venus through a refracting telescope .
To many people, astronomy begins with observing the sky, as pictured here with students using binoculars and magnification apps on their phones.
On the rooftop, the eyes of eager students lit up as they observed the evening sky.
As the busyness of the day faded and night fell on 2 July, around 20 secondary school students gathered at EdUHK’s Tai Po campus for an introductory astronomy course. Organised as part of the SES Summer Programme on STEM education, the session was given by Dr Chan Man-ho, Associate Professor of the Department of Science and Environmental Studies (SES). While the classroom lecture introduced them to common astronomical knowledge, such as the solar system, the Milky Way, the 88 constellations and Halley’s Comet, their enthusiasm for the night sky was ignited further when they tried star-gazing after the lecture.
“The universe is so big that we need a special unit to measure distance: a light-year, which is the distance light travels in one year,” Dr Chan said. In the highly condensed course, the astrophysicist talked about our solar system, including its eight planets and their moons, and the Milky Way, which is home to our Sun. He shared that our home galaxy stretches roughly 100,000 light-years across and contains an estimated 100 to 400 billion stars.
Dr Chan said there are an estimated 100 to 400 billion stars in our Milky Way, and our Sun is only one of them.
Constellations, a constant source of wonder for ordinary people, carry behind them a wealth of folklore and legends. Dr Chan (pictured on the left) said there are 88 official constellations in the sky.
For thousands of years, the patterns of stars have drawn the attention of scientists. They are also a source of wonder for ordinary people. “There are 88 official constellations in the sky: some are named after animals, some after inanimate objects, and some after humans or mythological characters. Among them, Orion, or Orion the Hunter, is particularly well known because it is visible from almost anywhere on Earth. It contains one of the most recognisable star patterns in the night sky, Orion’s Belt. Located in the centre of the Orion constellation, the belt consists of three bright, evenly spaced blue supergiant stars, and it helps astronomers locate other celestial objects,” Dr Chan explained.
Dr Chan highlighted that as the Earth orbits the Sun, the sky changes with the seasons, and depending on the time of year, different constellations become visible or disappear from view. During summer, the Summer Triangle, an astronomical asterism formed by Altair, Deneb and Vega (each being the brightest star in its respective constellation), is prominently visible in the northern celestial hemisphere. “Vega is known as the weaver girl (織女), while Altair is called the cowherd (牛郎) in Chinese astrology. According to Chinese folklore, the two stars meet once every year. But astronomy suggests that Altair and Vega are actually separated by light-years on the opposite sides of the Milky Way,” Dr Chan said.
Venus is in the western sky when observed shortly after sunset. “During evening hours, Venus is very bright and visible even by naked eyes,” Dr Chan said.
After the lecture, the students moved to the rooftop for star-gazing. However, because the sky was cloudy, typical of a July night, only a few stars could be seen. Even so, the students were not disappointed. “When you look up at the sky during evening, the brightest object in the west is Venus,” Dr Chan told the group. As the clouds gradually moved away, Venus finally came into view: a bright, yellowish, round object that drew a moment of awe from the student stargazers. “If you observe Venus through a telescope, you can see that it shows phases, much like our Moon,” Dr Chan explained.
Dr Chan said that, on average, 20 shooting stars streak across the sky each night, but people rarely notice them because they are so dim.
In the dark classroom and on the rooftop alike, students listened attentively to Dr Chan’s explanations. Images of the Milky Way, diagrams of the constellations and the sighting of Venus left a deep impression on them. They were amazed by the wonders and mysteries of the Universe. During the Q&A, Chan Kei-ching, a Form Two student from St Margaret’s Co-educational English Secondary and Primary School, learnt from Dr Chan that astronomers use different methods, such as parallax and emission spectra of stars, to measure interstellar distances. The student said he joined the Summer Programme because of his curiosity about the sky. “There are a lot of mysteries in the world which humans have not discovered yet. I really want to know more about the mysteries of the Universe,” he said.
Dora says she gained much knowledge about the universe and tips for stargazing from Dr Chan’s inspiring talk.
Chan Kei-ching, right, says he thinks of the mysteries of the Universe whenever he looks at the sky, and wants to learn more about it.
Dora Mao Shuran, a Form Four student from Creative Secondary School, expressed a similar passion. Dora developed an interest in astronomy years ago when she still lived in her home city of Shanghai. “I have fewer chances to observe stars after moving to Hong Kong because I left my observation equipment behind,” she said. Even so, she remained enthusiastic about learning more about the Universe. “I enjoy looking at night stars. It is fruitful that I learnt from tonight’s lecture that December and January, when the weather is drier and less cloudy, are the best times for star-gazing in Hong Kong,” Dora said.
“I hope they will keep interested in astronomy, and when winter arrives find a clearer night to observe the sidereal sky again,” Dr Chan concluded.
Before leaving the Tai Po campus, the secondary school star-gazers gathered on the podium to observe the sky once more.
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