Thereupon, when all the good signs of the zodiac gradually evolved, the heir apparent of Pāṇḍu, who would be exactly like him in prowess, took birth.
Astronomical calculations of stellar influences upon a living being are not suppositions, but are factual, as confirmed in Śrīmad-Bhāgavatam. Every living being is controlled by the laws of nature at every minute, just as a citizen is controlled by the influence of the state. The state laws are grossly observed, but the laws of material nature, being subtle to our gross understanding, cannot be experienced grossly. As stated in the Bhagavad-gītā (3.9), every action of life produces another reaction, which is binding upon us, and only those who are acting on behalf of Yajña (Viṣṇu) are not bound by reactions. Our actions are judged by the higher authorities, the agents of the Lord, and thus we are awarded bodies according to our activities. The law of nature is so subtle that every part of our body is influenced by the respective stars, and a living being obtains his working body to fulfill his terms of imprisonment by the manipulation of such astronomical influence. A man's destiny is therefore ascertained by the birthtime constellation of stars, and a factual horoscope is made by a learned astrologer. It is a great science, and misuse of a science does not make it useless.
(Srimad Bhagavatam-----1:12:12-----translation and purport).

In the midst of that region of outer space (antarikṣa) is the most opulent sun, the king of all the planets that emanate heat, such as the moon. By the influence of its radiation, the sun heats the universe and maintains its proper order. It also gives light to help all living entities see. While passing toward the north, toward the south or through the equator, in accordance with the order of the Supreme Personality of Godhead, it is said to move slowly, swiftly or moderately. According to its movements in rising above, going beneath or passing through the equator—and correspondingly coming in touch with various signs of the zodiac, headed by Makara (Capricorn)—days and nights are short, long or equal to one another.
(Srimad Bhagavatam-----5:21:3-----translation).

The demigod Sūrya is always in touch with the Supreme Personality of Godhead, Nārāyaṇa. Residing in outer space, which is in the middle of the universe, between Bhūloka and Bhuvarloka, the sun rotates through the time circle of the zodiac, represented by twelve rāśis, or signs, and assumes different names according to the sign he is in. For the moon, every month is divided into two fortnights. Similarly, according to solar calculations, a month is equal to the time the sun spends in one constellation; two months constitute one season, and there are twelve months in a year. The entire area of the sky is divided into two halves, each representing an ayana, the course traversed by the sun within a period of six months. The sun travels sometimes slowly, sometimes swiftly and sometimes at a moderate speed. In this way it travels within the three worlds, consisting of the heavenly planets, the earthly planets and outer space.
(Srimad Bhagavatam-----5:22-----summary).

The sun-god, who is Nārāyaṇa, or Viṣṇu, the soul of all the worlds, is situated in outer space between the upper and lower portions of the universe. Passing through twelve months on the wheel of time, the sun comes in touch with twelve different signs of the zodiac and assumes twelve different names according to those signs. The aggregate of those twelve months is called a saṁvatsara, or an entire year. According to lunar calculations, two fortnights—one of the waxing moon and the other of the waning—form one month. That same period is one day and night for the planet Pitṛloka. According to stellar calculations, a month equals two and one quarter constellations. When the sun travels for two months, a season passes, and therefore the seasonal changes are considered parts of the body of the year.
(Srimad Bhagavatam-----5:22:5-----translation).

Situated 1,600,000 miles above Mercury, or 8,800,000 miles above earth, is the planet Mars. If this planet does not travel in a crooked way, it crosses through each sign of the zodiac in three fortnights and in this way travels through all twelve, one after another. It almost always creates unfavorable conditions in respect to rainfall and other influences.
(Srimad Bhagavatam-----5:22:14-----translation).

Situated 1,600,000 miles above Mars, or 10,400,000 miles above earth, is the planet Jupiter, which travels through one sign of the zodiacwithin the period of a Parivatsara. If its movement is not curved, the planet Jupiter is very favorable to the brāhmaṇas of the universe.
(Srimad Bhagavatam-----5:22:15-----translation).

Situated 1,600,000 miles above Jupiter, or 12,000,000 miles above earth, is the planet Saturn, which passes through one sign of the zodiac in thirty months and covers the entire zodiac circle in thirty Anuvatsaras. This planet is always very inauspicious for the universal situation.
(Srimad Bhagavatam-----5:22:16-----translation).

The word ayana means "path" or "going." The six months when the sun moves toward the north are called uttarāyaṇa, or the northern path, and the six months when it moves south are called dakṣiṇāyana, or the southern path. These are mentioned in Bhagavad-gītā (8.24-25). The first day when the sun begins to move north and enter the zodiacal sign of Capricorn is called Makara-saṅkrānti, and the first day when the sun begins to move south and enter the sign of Cancer is called Karkaṭa-saṅkrānti. On these two days of the year, one should perform the śrāddha ceremony.
Viṣuva, or Viṣuva-saṅkrānti, means Meṣa-saṅkrānti, or the day on which the sun enters the sign Aries. Tulā-saṅkrānti is the day on which the sun enters the sign Libra. Both of these days occur only once within a year. The word yoga refers to a certain relationship between the sun and moon as they move in the sky. There are twenty-seven different degrees of yoga, of which the seventeenth is called Vyatīpāta. On the day when this occurs, one should perform the śrāddha ceremony.
(Srimad Bhagavatam-----5:14:20-23).