Long-lasting activity of asteroid (248370) 2005 QN<SUB>173</SUB>

We present the results of observations of asteroid (248370) QN<SUB>173</SUB> obtained during July 2021-January 2022 with three telescopes. Our analysis revealed the presence of the dust tail for about half of a year. The direct images of the asteroid were obtained with broad-band filters. No emissions were revealed in the spectra, and the spectrum of the asteroid closely matched that of a C-type asteroid. Created colour and linear polarization variations along the tail were analysed. The asteroid demonstrated a redder colour compared to the Sun. Dramatic changes in dust productivity obtained in different filters were not detected. The g - r colour changes from 0.2<SUP>m</SUP> to 0.7<SUP>m</SUP> over the coma, and the linear polarization degree varies from about 1.2 per cent to 0.2 per cent and from -0.2 per cent to -1.5 per cent at the phase angle of 23.2° and 8.16°. The total dust mass ejected until the latest observation on October 10 is 4.2 × 10<SUP>7</SUP> kg, with a maximum rate of 2.6 kg s<SUP>-1</SUP> based on the Monte Carlo modelling of the dust tail. The estimated asteroid size is 1.3 km. It is shown that large particles are concentrated around the nucleus, whereas smaller ones dominate in the tail. The evolution of (248370) QN<SUB>173</SUB> orbit and the orbits of the sample of the 464 short-periodic comets were followed. Ten of them approached the asteroid's orbit. These objects are not genetically related, despite very close distance of their orbits for a relatively long time.