Here's why:
* Jirachi is a Pokémon introduced in Generation III (Ruby, Sapphire, and Emerald). However, it's not available in the original games.
* The Outerspace mod is an unofficial ROM hack for Pokémon Emerald that adds new features and content. It's not officially endorsed by Nintendo, and while it may include additional Pokémon, it's unlikely to add Jirachi.
To encounter Jirachi, you would need to play Pokémon Ruby or Sapphire. Even then, it is a very rare Pokémon, and getting it requires specific steps and events.
If you're interested in encountering Jirachi, you'll need to:
* Play Pokémon Ruby or Sapphire.
* Obtain a special item called the "Azure Flute". This requires completing the main story and finding a hidden location.
* Use the Azure Flute at a specific location, which will summon Jirachi for a battle.
While it's not possible to get Jirachi in the original Pokémon Emerald or with the Outerspace mod, there are other ways to experience the joy of catching this mythical Pokémon!