The heavier alkali metals are also less abundant than the lighter ones as the alkali metals from rubidium onward can only be synthesised in supernovae and not in stellar nucleosynthesis.
ðə hˈɛviɚɹ ˈælkəlˌaɪ mˈɛɾəlz ɑːɹ ˈɔːlsoʊ lˈɛs ɐbˈʌndənt ðɐn ðə lˈaɪɾɚ wˈʌnz æz ðɪ ˈælkəlˌaɪ mˈɛɾəlz fɹʌm ɹuːbˈɪdiəm ˈɑːnwɚd kæn ˈoʊnli biː sˈɪnθəsˌaɪzd ɪn sˈuːpɚnˌoʊvə ænd nˌɑːt ɪn stˈɛlɚ nˈuːklɪˌɑːsɪnθəsˌɪs.