Chromospheric cannonballs on the Sun

In the highly dynamic chromosphere, there exist many kinds of small-scale activities, such as spicules, surges, and Ellerman bombs. Here, we report the discovery of a new phenomenon in the chromosphere observed with the New Vacuum Solar Telescope at the Fuxian Solar Observatory. In the high tempo-spatial resolution H$\alpha$ images, some dark or bright structures are found to fly along the curved trajectory, looking like cannonballs. Their average size, mass, and velocity are about 1.5 $\times$ 10$^{9}$ km$^{3}$, 1.5 $\times$ 10$^{8}$ kg, and 56 km s$^{-1}$, respectively. In the simultaneous (extreme-)ultraviolet images obtained by the Solar Dynamics Observatory, these cannonballs appear as brighter features compared to the surrounding area, implying that there exists some kind of heating during this process. The photospheric magnetograms show the magnetic flux emergence and interaction with the pre-existing fields. These observations reveal that the cannonballs are chromospheric material blobs launched due to the magnetic reconnection between emerging magnetic flux and the pre-existing loops.