The absolute minimum antenna which will work for you is a dipole cut to the frequency of interest. With this antenna you will be able to hear some of Jupiter's louder bursts.
Dipoles are good antennas for beginners because they are so easy to make and erect.
They match easily to the feed line and are cheap to construct. Let's say you pick 21 MHz. This will give you a length of 22.24 feet. It doesn't matter whether or not the wire is insulated. While you are there buy a roll of good strong nylon twine.