[표지로 읽는 과학] A satellite that shines brighter than the stars in the night sky

The international academic journal Nature featured a star shining in the night sky as its cover this week. Objects moving in a tail across the dark night sky may look like shooting stars.

Recently, most lights that look like stars in the night sky are not stars at all. Many of these glowing objects are satellites. As science and technology develop, the proportion of artificial satellites replacing stars in the night sky is increasing. The star trail that appears on the cover of Nature is not actually a shooting star. It captures the traces left by artificial satellites as they pass through the sky.

Now, research has shown that when we look for the brightest star in the night sky, it may not be a star but a satellite. Scientists are concerned that the brightly shining satellite could threaten future astronomy research.

Sangita Nandakumar, a researcher at the Astronomy and Planetary Research Institute at Akatama University in Chile, and a research team published research results in Nature on October 2 that showed that the brightness of light emitted by a group of artificial satellites exceeded the brightness of stars. Samantha Roller, a professor at the University of Regina in Canada, shed light on Nandakumar’s research team’s paper in her contribution to this issue of Nature and said that bright satellites are interfering with the research of astronomers around the world.

According to Nandakumar’s research team, as a result of approximately 4 months of follow-up observation of the US private communication satellite ‘Blue Walker 3’, which was launched into low-Earth orbit at an altitude of 500 km in 2022, the satellite’s maximum apparent brightness magnitude was found to be 0.4.

It is similar in brightness to ‘Procyon’ and ‘Achernar’, the brightest stars in Canis Minor and Eridanus, respectively. The apparent brightness of Blue Walker 3 was 2nd magnitude, similar to that of the North Star, at the beginning of launch. During the mission, the satellite changed its attitude and its magnitude increased as its large solar panels reflected a large amount of light.

The closer the apparent brightness is to 0, the brighter it is. The difference in brightness of one grade is 2.5 times. The International Astronomical Union recommends that the apparent brightness of satellites in low-Earth orbit be kept below magnitude 7. The apparent brightness of Blue Walker 3 is about 400 times the standard value.

The research team emphasized, “If satellite launches are to be avoided to damage terrestrial astronomy research, the potential impact on the night sky must be taken into account.”