As per the Hindu religion and Vedic astrology, the nine planets that govern and influence every aspect of our lives are termed as Navagrahas. In Sanskrit, nava means nine and graha is taken from the word grih which means "to seize" or "to influence" or "to take hold of".
It is said that in ancient times, the Hindu sages or rishis found that there were certain forces which influenced or impacted the life of a human being greatly. Of all the forces, they recognized the nine powerful ones and termed them as Navagrahas. The Navagrahas are personified and worshipped as celestial deities by the Hindus. Most of the temples will have a dedicated section with the nine idols of navagrahas to facilitate the worship.
The nine entities that constitute Navagrahas are as follows:
According to the Vedic astrology, these nine entities have certain fields and energies associated. The influence of such energies on the rise and fall in each one's life is the main study of the Indian astrology. In fact, the astrologers state that the characteristic traits including the physical aspects are actually created and shaped by the position of the Navagrahas in one's horoscope.
It is strongly believed that the grahas have to be worshipped and appeased in order to maintain peace and harmony in our lives. Hence there are various slokas or mantras that have been written for each graha or the influencing entity. The most famous and the common among them all is the Navagraha mantra written by Veda Vyasa.
Namah Suryaya Chandraya Mangalaya Budhayacha
Guru Shukra Shani Bruhascha Raahave Ketave Namaha
Meaning: I bow to Navagrahas, the Sun, Moon, Mars, Mercury, Jupiter, Venus, Saturn, Rahu, and Ketu.
Japakusuma Sankasham Kaashya Peyam Maha Dyutim
Tamo Arim Sarva Paapaghnam Pranathosmi Divakaram
Meaning: I pray to the Sun (Surya), the day-maker, destroyer of all sins, the enemy of darkness, of great brilliance, the descendant of Kaashyap, the one who shines like the japaa flower.
Dadhi Shankha Tusha Raabham Kshiiro Dhaarnava Sambhavam
Namami Shashinam Somam Shambor Mukuta Bhushanam
Meaning: I pray to the Moon (Chandra) who shines coolly like curds or a white shell, who arose from the ocean of milk, who has a hare on him, Soma, who is the ornament of Shiva's hair.
Dharani Garbha Sambhutam Vidyut Kanti Samaprabham
Kumaram Shakti Hastam Cha Mangalam Pranamaamyaham
Meaning: I pray to Mars (Kuja or Mangala), born of Earth, who shines with the same brilliance as lightning, the young man who carries a spear.
Priyangu Kalika Shyamam Roopena Pratimam Budham
Sowmyam Sowmya Guno Petam Tam Budham Prana Maamyaham
Meaning: I pray to Mercury (Budha), dark like the bud of millet, of unequalled beauty, gentle and agreeable.
Devanaam Cha Rishii Namcha Gurum Kanchana Sannibham
Buddhi Bhuutam Trilo Kesham Tam Namami Bruhaspatim
Meaning: I pray to Jupiter (Guru), the teacher of Gods and Rishis, intellect incarnate, lord of the three worlds.
Hima Kunda Mruna Labham Daityanam Paramam Gurum
Sarva Shastra Pravak Taram Bhar Gavam Prana Maamyaham
Meaning: I pray to Venus (Shukra), the ultimate preceptor of demons, promulgator of all learning, he who shines like the fiber of snow-white jasmine.
Nilanjana Samabhasam Ravi Putram Yamagrajam
Chaya Martanda Sambhutam Tam Namami Shanaishcharam
Meaning: I pray to Saturn (Shani), the slow moving, born of shade and Sun, the elder brother of Yama, the offspring of Sun, he who has the appearance of black Collyrium.
Ardha Kaayam Mahaa Viiryan Chandraa Ditya Vimardhanam
Sinhi Kaagarbha Sambhutam Tam Rahum Prana Maamyaham
Meaning: I pray to Rahu, having half a body, of great bravery, the eclipser of the Moon and the Sun, born of Simhikaa.
Palasha Pushpa Sankaasham Taarakaa Graha Mastakam
Rowdram Rowdraa Tmakam Ghoram Tam Ketum Prana Maamyaham
Meaning: I pray to Ketu, who has the appearance of Palaasha flower, the head of stars and planets, fierce and terrifying.
Navagrahas indeed form an integral part of Hinduism as well as Vedic astrology. There is also a particular puja performed for each graha known as "Graha Shanthi". This pooja is usually performed to establish peace or truce with the graha, mainly its negativities.
Astrologers prescribe different gemstones for each entity of Navagrahas. It is believed that if the right gemstone is worn, then the negative effects of the position of the particular deity diminish and the positivity can reap in more benefits.