In the first model, some scientists propose that only the four planets 581b, 581c, 581d, and 581e orbit Gliese 581. None of the planets orbits in a circle. Instead, their paths around the star are ellipses.
ɪ n ð ə WORD_BOUNDARY f ɜː s t WORD_BOUNDARY m ɑ d ə l WORD_BOUNDARY s ʌ m WORD_BOUNDARY s aɪ ə n t ɪ s t s WORD_BOUNDARY p ɹ ə p oʊ z WORD_BOUNDARY ð æ t WORD_BOUNDARY oʊ n l i WORD_BOUNDARY ð ə WORD_BOUNDARY f ɔ ɹ WORD_BOUNDARY p l æ n ɪ t s WORD_BOUNDARY f aɪ v h ʌ n d ɹ ɪ d WORD_BOUNDARY eɪ t i WORD_BOUNDARY w ʌ n WORD_BOUNDARY b iː WORD_BOUNDARY f aɪ v h ʌ n d ɹ ɪ d WORD_BOUNDARY eɪ t i WORD_BOUNDARY w ʌ n WORD_BOUNDARY s iː WORD_BOUNDARY f aɪ v h ʌ n d ɹ ɪ d WORD_BOUNDARY eɪ t i WORD_BOUNDARY w ʌ n WORD_BOUNDARY d iː WORD_BOUNDARY æ n d WORD_BOUNDARY f aɪ v h ʌ n d ɹ ɪ d WORD_BOUNDARY eɪ t i WORD_BOUNDARY w ʌ n WORD_BOUNDARY iː WORD_BOUNDARY ɔ ɹ b ɪ t WORD_BOUNDARY ɡ l iː z ə WORD_BOUNDARY f aɪ v h ʌ n d ɹ ɪ d WORD_BOUNDARY eɪ t i WORD_BOUNDARY w ʌ n WORD_BOUNDARY n ʌ n WORD_BOUNDARY ʌ v ð ə WORD_BOUNDARY p l æ n ɪ t s WORD_BOUNDARY ɔ ɹ b ɪ t s WORD_BOUNDARY ɪ n WORD_BOUNDARY ʌ WORD_BOUNDARY s ɜː k ə l WORD_BOUNDARY ɪ n s t ɛ d WORD_BOUNDARY ð ɛ ɹ WORD_BOUNDARY p æ θ s WORD_BOUNDARY ə ɹ ɹ aʊ n d WORD_BOUNDARY ð ə WORD_BOUNDARY s t ɑ ɹ WORD_BOUNDARY ɑ ɹ WORD_BOUNDARY ɪ l ɪ p s ɪ z WORD_BOUNDARY