I think Junko Yagami's（八神純子） 7th single "Polar Star" was her first one to delve into straight disco pop when compared to her first releases of pop ballads and Latin-infused tunes. Released in July 1979, I first came across it in her compilation album, "Best Of Me" which came out in 1990. On listening to it, there were some parts which reminded me of Olivia Newton-John's "Xanadu" (perhaps it was the soaring strings).
Written by Yagami and Yoshiko Miura（三浦徳子）and composed by the singer, "Polar Star" seems to be a tribute to the North Star itself....perhaps the only song I know that is astronomically disco. It does fly at the speed of light but Yagami's vocals are more than game to soar with the melody. I also enjoy how her voice hums off into the distance at the end, almost like the sung version of the Aurora Borealis. Mind you, she had some good practice with her most representative hit, "Mizuiro no Ame"（みずいろの雨）from the previous year, and this single would propel her into another disco hit, "Purpletown" a year later.
When I first heard the song all those years ago, it struck me as having a heroic theme so I wondered a bit whether the title was actually named after some heroine named Paula Starr. However, the lyrics set me straight. In any case, "Polar Star" peaked at No. 8 on Oricon and was the 51st-ranked song for 1979. Perhaps if there had been a Japanese team at the annual Iditarod Trail Sled Dog Race back then, this would have made for a nice inspirational tune instead of just yelling "Mush" across Alaska.