Solar-B lifted off from Uchinoura, at the southern tip of Japan, at 0636 local time on Saturday (2136 GMT Friday).
"It will take two to three weeks to transfer the spacecraft into its so-called Sun-synchronous polar orbit. From this position, Solar-B will be able to observe the Sun without having any nights for eight months of the year" - Professor Tetsuya Watanabe, of the National Astronomical Observatory of Japan (NAOJ).
As is customary on Japanese missions, the satellite will get a new name once it is ready to begin its work.
According to the JAXA launch blog, the Santiago tracking Station has confirmed that the satellite successfully separated from the M-V-7 launch vehicle, and was inserted into the correct orbit and that the solar panels were deployed.