I recently came upon a wall chart that shows the 'gravity wells' of the various planets in our solar system. the chart does include a 'noises off'- style mention of the Sun's own gravity well, which is appended by the unhelpful comment: 'An awfully long way down'. I've since found out that for the Sun it's around the 19,000,000 km mark - which compared to the Earth's own 6,400 km gravity well, is indeed an awfully long way down. It did get me thinking, however. I assume the depth of a gravity well is determined purely by the mass of a given object, rather than its density or surface gravity. As an example: were the Sun to be transformed into a white dwarf or even a black hole, would its gravity well be the same, I wonder? I should expect so, but I cannot be entirely sure. Indeed, I'm prepared to be proven wrong - especially when it comes to black holes, which seem to defy commonsense at every turn.