Parasara : "O Brahmin, the four incarnations, viz. Rama, Krishna, Narasimha and Varaha are wholly with Paramatmamsa. The other incarnations (than these, out of the ten) have in them Jeevamsa too."
The Unborn lord has many incarnations. He has incarnated as the planets (Nava Grahas) to bestow on the living beings the results due to their Karmas. He is Janardana. He assumed the auspicious form of Grahas to destroy the demons (evil forces) and sustain the divine beings.
Verse 5-7 — Planetary Correspondences with Divine Incarnations
रामोऽवतारः सूर्यस्य चन्द्रस्य यदुनायकः ।
नृसिंहो भूमिपुत्रस्य बुद्धः सोमसुतस्य च ॥५॥
वामनो विबुधेज्यस्य भार्गवो भार्गवस्य च ।
कूर्मो भास्करपुत्रस्य सैंहिकेयस्य सूकरः ॥६॥
केतोर्मीनावतारश्च ये चान्ये तेऽपि खेटजाः ।
परात्मांशोऽधिको येषु ते सर्वे खेचराभिधाः ॥७॥
rāmo'vatāraḥ sūryasya candrasya yadunāyakaḥ |
nṛsiṁho bhūmiputrasya buddhaḥ somasutasya ca ||5||
vāmano vibhedhejyasya bhārgavo bhārgavasya ca |
kūrmo bhāskaraputrasya saiṁhikeyasya sūkaraḥ ||6||
ketormīnāvatāraśca ye cānye te'pi kheṭajāḥ |
parātmāṁśo'dhiko yeṣu te sarve khecarābhidhāḥ ||7||
From the Sun God the incarnation of Rama, from the Moon that of Krishna, from Mars that of Narasimha, from Mercury that of Budhdha, from Jupiter that of Vamana, from Venus that of Parasu Rama, from Saturn that of Koorma (Tortoise), from Rahu that of Varaha (Pig) and from Ketu that of Meena (Fish) occurred. All other incarnations than these also are through the Grahas. The beings with more Paramatmamsa are called divine beings.
Verse 8-13 — Jeevatmamsa, Reabsorption, and the Supreme Duty to Study Astrology
The beings with more Jeevatmamsa are (mortal) beings. The high degree of Paramatmamsa from the Grahas, viz. Sun etc. did incarnate as Rama, Krishna etc. After completing the mission, the Paramatmamsas (of the respective) Grahas again merge (in the respective) Grahas. The Jeevatma portions from the Grahas take births as human beings and live their lives according to their Karmas and again merge in the Grahas. And at the time of Great Destruction the Grahas as well merge in the Lord Vishnu. One who knows of all these, will become versed in the knowledge of the past, present and future. Without a knowledge of astrology these cannot be known. Hence everyone should have a knowledge of astrology, particularly the Brahmin. The one who, devoid of knowledge of astrology, blames this Vedic Science will go to the hell called 'Raurava' and will be reborn blind.