Sixty years ago today, on June 25, 1965 (May 26, 1965 in the lunar calendar), Lindblad, a pioneer in the structure of the Milky Way, passed away. Bertil Lindblad (November 26, 1895-June 25, 1965) was a Swedish astronomer and pioneer in the structure and dynamics of the Milky Way. Lindblad was born in Orebro, Sweden in 1895. He entered Uppsala University in 1914 and obtained his doctorate in 1920. From 1921 to 1927, he worked at the Uppsala University Observatory. In 1927, he served as Professor of Astronomy at the Royal Swedish Academy of Sciences. He founded the Stockholm Observatory and served as the first director until his death. In addition, he served as Chairman of the International Astronomical Union from 1948 to 1952 and twice as President of the Royal Swedish Academy of Sciences. Lindblad died in Stockholm in 1965. Lindblad's main work is on the structure of galaxies and star clusters, and is a pioneer in galactic dynamics. He found that stars tend to gather in the spiral arms of galaxies. In 1926, Lindblad proposed that the Milky Way consists of many subsystems, explained the velocity distribution of stars in the Milky Way, and proposed that the Milky Way's rotation center is in the direction of Sagittarius. In 1927, the famous paper on the differential rotation of the Milky Way was published, laying the foundation for the Dutch astronomer Alter to further establish the theory of the rotation of the Milky Way. In 1942, he first proposed the density wave theory to explain the spiral arm structure of spiral galaxies. He also conducted radiation research in the 1920s to explain the Sun's near-edge dimness. Lindblad received the Gold Medal of the Royal Astronomical Society in 1948 and the Bruce Award in 1954. A crater on the moon and asteroid 1448 were named Lindblad.