A candle can burn in zero gravity. Here’s a comparison picture as well.
According to David Bryant of European Space Agency, The Netherlands, “A candle can burn in zero gravity. The flame is a diffusion flame which tends to a spherical shape in the absence of airflow. The burning rate is reduced drastically since combustion only occurs in a thin spherical shell where the outward diffusing fuel vapours meet the inward diffusing oxygen. The flame loses the yellow colour of incandescent carbon particles and becomes an almost invisible clear blue. To test this, candles were burnt on board the space station Skylab.”
