Surya (Sun); Chandra (Moon); Guru, Brihaspati (Jupiter); Kuja, Mangala, Angaraka (Mars); Shukra (Venus); Shani (Saturn); Buddha (Mercury).
Surya (Sum, Ram, Om); Chandra (Cham, Som); Guru (Gum, Brahm, Brim, Gam); Kuja (Kum, Am, Mam); Shukra (Shum); Shani (Sham); Buddha (Bum, Dhi). Lunar nodes are also considered as a Graha (planets-seizers) in Vedic Astrology and their bija mantras are: Rahu (Ram), Ketu (Kem). Bija mantras of controlling deities can be applied as well.
Upanishads say that Aum (Om) is a sound of Para-Brahman, initial sound, which creates all nama-rupa "all forms known by names-sounds"). Om is a sound of the essential cosmic vibration transmitted through the Sun. Om is good for all planets, particularly the Sun, Moon, Jupiter. All mantras usually (but not always, especially in Tantra) begin with Om.
This mantra is a bija mantra of Sarasvati, Goddess of knowledge and Vak (speech) and consort of Brahma (creator of Universe). Its primary related to the planet Mercury as a planet of speech, knowledge and guidance. It is sometimes used for the Moon and Jupiter, promoting their creative and expansive powers. AIM is also mantra of Guru and helps o access Jnana (higher knowledge). It can be used to call the wisdom power of any planet that we direct it towards.
This mantra is a bija mantra of Lakshmi, Goddess of prosperity and abundance and consort of Vishnu (preserver of Universe). Its primary related to the Moon as a planet of abundance, happiness and fertility. It is sometimes used for Venus as a Goddess mantra for the hart, happiness and love. It is also used relative to Jupiter for its general benefic qualities. Shrim is a mantra of refuge and devotion. It can be used for expression of devotion to any planetary deity, helping us to gain its favor.
Ram is a mantra of Rama (avatara of Vishnu). He is a yuga-avatara of Treta-yuga in his protective, saving, compassionate form. Ram is a bija mantra for Rahu. It can also be used relative to the Sun, Mars, Jupiter or whatever planet whose saving power we wish to increase. It is most applicable to the Sun.