From 1826, hoping to detect a planet closer to the Sun than Mercury crossing the Sun’s disk, he kept daily records of the number of sunspots visible, and in 1843 announced that the number varied with a period of about 10 years. Schwabe’s discovery went largely unnoticed until publicized in 1851 by the German naturalist Friedrich Wilhelm Heinrich Alexander von Humboldt (1769–1859). J. R. Wolf collated sunspot data and in 1857 announced a period of just over 11 years, whereupon Schwabe received due recognition.