Astral Blast and Thunder Mine are Jupiter single-target Psynergies, available to the Page and Apprentice Class series. Isaac (Apprentice), Felix (Apprentice), Garet (Page), and Jenna (Page) can use them if they have enough Jupiter Djinn for their class series.
An "attack with celestial force," Astral Blast appears as a group of stars fired from the user, striking the foe at a distance. In the Page series, Astral Blast is usable by the Page, Illusionist and Enchanter classes; in the Apprentice series, it is usable by the Apprentice, Illusionist and Enchanter classes (note that the latter two classes are different from their counterparts in the Page series). Astral Blast is also usable in both versions of the Conjurer class in the first Golden Sun. Astral Blast isn't as strong as others like it, such as Heat Wave, but it does do its job well, especially against Venus-based enemies such as Tret. Astral Blast costs 5 PP to use and strikes the target with Jupiter power equal to the user's own attack power with 32 base Attack added. It is obtained at level 11.
As with Psynergy like it, the more powerful Thunder Mine replaces Astral Blast after the wielder reaches the Conjurer class in The Lost Age. An "attack with ball lightning," Thunder Mine appears as a large ball of plasma-like energy with a heavy electrical charge slowly crashing into the foe. Unlike other, commonly used counterpart attacks, like Diamond Berg, Thunder Mine is supported by a large supply of PP. It costs 16 PP to use and strikes the target with Jupiter power equal to the user's own attack power with 85 base Attack added.
Astral Blast can be useful for Felix in The Lost Age because when going through the game acquiring Djinn as they are found, the player is subject to unequal Djinn distribution until Piers joins. Even then, distribution can be problematic. Set Djinn's power is critical at early stages of the game, and to avoid putting them on Standby to keep the mono-elemental classes, the player can switch them around and make Felix an Illusionist, with Astral Blast as his most useful spell. A good strategy to go along with that is to make Jenna a Brute, as the attack increase eliminates the need for a lot of Psynergy (in most cases she becomes stronger than Felix), and give Sheba the remaining Djinn to decide her class, or equip the Mysterious Card or Trainer's Whip.
Thunder Mine is acquirable late in the game, and is usually used infrequently because Felix's Venus Psynergy overpowers it.