WTH! Wok the Hydrogen: Measurement of Galactic Neutral Hydrogen in Noisy Urban Environment Using Kitchenware

Astronomy observation is difficult in urban environments due to the background noise generated by human activities. Consequently, promoting astronomy in metropolitan areas is challenging. In this work, we propose a low-cost, educational experiment called Wok the Hydrogen (WTH) that offers opportunities for scientific observation in urban environments, specifically the observation of the $21$ cm ($f_{21} = 1420.4$ MHz) emission from neutral hydrogen in the Milky Way. We demonstrate how to construct a radio telescope using kitchenware, along with additional electronic equipment that can be easily purchased online. The total system cost is controlled within 150 dollars. We also outline the subsequent data analysis procedures for deriving the recession velocity of galactic hydrogen from the raw data. The system was tested on the campus of the Hong Kong University of Science and Technology, which is located approximately 2 km northeast of the nearest residential area with a population of 0.4 million and about 10 km east of the downtown area with a population of 2 million. We show that a precision of $\Delta v \approx \pm 20$ km s$^{-1}$ can be achieved for determining the recession velocity of neutral hydrogen with this relatively simple setup, and the precision can be further improved with longer exposure time.