Belopolsky got his degree at
Moscow University in 1876, and in 1878, he became the assistant to
Fyodor Aleksandrovich Bredikhin at
Moscow Observatory. In 1888, he joined the staff of
Pulkovo Observatory. He worked in
spectroscopy and discovered a number of
spectroscopic binaries. Among others, he discovered that
Castor B was a spectroscopic binary with a period of 2.92 days. Belopolsky was known for his fine instrument making, and in 1900 he built an apparatus with which he managed to experimentally detect Doppler shift of light reflected from a moving object. This was a breakthrough, since before this experiment the possibility of Doppler shift in light - as opposed to matter waves like sound - was still a controversial matter. He pioneered the use of optical Doppler shift to measure the rotational rates of distant objects. He was the first to discover that the equator of Jupiter rotates more rapidly than higher latitudes, and that the rings of Saturn do not rotate as a solid mass, proving that they were made up of individual small objects. He attempted twice to measure the rotational rate of Venus, suggesting 24 hours in 1900 and 35 hours in 1911—one of countless unsuccessful attempts by astronomers of that time to measure the length of the Venusian day. He was a good friend of
Oskar Backlund, and when the latter died in 1916, he succeeded him as director of Pulkovo Observatory. However he resigned in 1918, because he did not like the administrative burden. The crater
Belopol'skiy on the
Moon, the asteroid
1004 Belopolskya and
an award of the
Russian Academy of Sciences are named after him. , 1910 == References ==