Using the 10MP mode may make noise look lower, but likely not because the sensor is gathering cleaner data. Based on the answers, the camera is probably just downsizing the full 24MP image before saving it, rather than doing true hardware pixel binning. Downsizing can smooth noise, but you can usually get the same or better result later on your computer with more control.

For night photography, it’s better to shoot at full resolution—ideally RAW—and resize during editing if needed. That preserves all the original detail and gives you better options for noise reduction. If noise is still a problem, techniques like image stacking can help more than switching to a lower megapixel mode.

So: lower MP mode can reduce visible noise somewhat, but mostly as a byproduct of resizing, not because the camera becomes inherently less noisy.