The Heart of Gold is a spaceship from the part of the book where Zaphod saves Ford and Arthur after being chucked out into the middle of space by the vogons and they Saved them by using the power of the improbability drive that helps them get through every point in the universe simultaneously.It also Symbolises power and the ability to get anywhere they want to.
The Heart of Gold is the sleekest, most advanced, coolest spaceship in the galaxy. Its stunning good looks mirror its awesome speed and power. It is powered by the revolutionary new Infinite Improbability Drive, which lets the ship pass through every point in every universe simultaneously
The Heart of Gold is a symbol because it is the main source of transportation that Arthur and Ford use to get to their destination of Magrathea and the improbability drive is the thing that gets them there. It is also a symbol because it is powered by the improbability drive and it naturally represents the strange and “improbable” things that happen in life