Infinite Cosmos

Purnamadah purnamidam | Purnat purnamudachyate
Purnasya purnamadaya | Purnamevavashishyate.
[infinite Brahman - Isha Upanishad]
"That [Brahman, the Supreme Being] is infinite (full, complete). This [physical Universe] is infinite. From the infinite [Brahman], the infinite [Universe] came into being. The infinite [Brahman] having the infinite [Universe] taken away, remains infinite."

Universe is immense and we donot know whether the Universe has an "end" or not; we are not completely sure even of the full meaning of the question.
The Universe is probably 10-20 billion years old. The entire Universe is not static, but expanding. Universe contains objects such as Galaxies (some exploding and colliding); Neutron Stars and Pulsars; Quasars; and Black Holes
Our Solar System located at the edge of the Milkiway disk of stars is probably 4-5 billion years old. The Milkiway, bright band of stars is estimated to be about 50000 light years in its diameter. There are 200 billion "Suns" in a galaxy like our own Milky Way, a spiral galaxy.
Astronomers can see billions of galaxies. Around 10000 stars visible to our naked eye are generally within a few hundred light years around us. Some giant stars are located nearly 1000 light years are also visible to naked eye.
The Solar System is the "system" of planets, asteroids, and comets that orbit around our Sun. Newer suns (such as our Sun) are in the spiral arms. Older suns are in the center of the galaxy. Our Solar System is in the Orion Arm of the Milky Way.


Astronomy Myths

Vedic Astronomical Values

The Sanskrit word "jyotish" referred to the study of astronomy and astrology both; as in other cultures of the day, astronomy and astrology were considered inseperable. The astronomical methods outlined in the Vedanga-jyotisha were thus in use in India for a long time. It is clear in the text of Surya Siddhanta and the current practice of Indian astrology that sidereal measurements are of primary importance. Tropical measurements are also used but in a secondary way.
  1. Twelve spokes, one wheel, navels three. Who can comprehend this? On it are placed together three hundred and sixty like pegs. They shake not in the least. (Dirghatama Rishi, Rig Veda 1.164.48)
  2. One of the oldest works on jyotish is the Vedanga-jyotisha, probably written by Lagadha. He most likely compiled techniques and observations from manuscripts that existed in his day. The work that survives was probably rewritten by later astronomers around 400 BCE, judging from the work's clasical (post-Vedic) Sanskrit. However, this work contains an observation that the Winter Solstice occurred when the star Shravishtha (α Delphini) was on the horizon. This dates the original work around 1400 BCE, placing it in the late Vedic period.
  3. A seven named horse does draw this three naved wheel… Seven steeds draw the seven wheeled chariot… Wise poets have spun a seven strand tale around this heavenly calf, the Sun. (Dirghatama Rishi, Rig Veda 1.164.1 5). Seven visible planets.
  4. The number seven related to the Sun has much significance when understanding the third mean solar motion. During the course of 10,000 years there are seven rotations of the third mean solar motion. For a single year the count is 0.2563795 diurnal revolutions of the earth. For two years it is .512759 and so on. One complete rotation (to equal 366.2564…) of the third motion takes 1428.571429 [10000/7] sidereal years.
  5. Yuga in mythology is a large number. Sun (our whole solar system) orbits around the center of the Milky Way Galaxy at 828,000 km/hr. But even at that high rate, it still takes us about 230 million years to make one complete orbit around the Milky Way
  6. Axial precession is the movement of the rotational axis of an astronomical body, whereby the axis slowly traces out a cone. In the case of Earth, this type of precession is also known as the precession of the equinoxes or precession of the equator. Earth goes through one such complete precessional cycle in a period of approximately 26,000 years, during which the positions of stars as measured in the equatorial coordinate system will slowly change; the change is due to the change of the coordinates. IT takes 26,471 years to come to same position. Every 2206 years, starting rasi for solar year will move by one.

Saptarishi Mandala
Mandala means Circle, Saptarishi means 7 sages. The 7 stars of what we call the Great Bear (Ursa Major) or Big Dipper in English, have been called or named after The Seven Sages or the Sapta Rishis in Indian Astronomy. (Interestingly Sapta Rsha (Seven Sages), can have been distorted to Sapta Rksha (Seven Bears) which could have led to the name Great Bear. The seven sages are Marici to the east (alpha), Vasishta (beta) to his west, then Angiras (gamma), then Atri (delta), then Pulastya (epsilon), then Pulaha (zeta), and Kratu (eta)” (5 and 6) : Brihat Samhita of Varahamihira. There are two sets of definitions as to who the saptha Rishi's are. The vedic tradition is 'Gautama, Vishwamithra, Jamahagni, Bharadwaaja, Kashyapa, Vasishtha and Athri' are the saptha rishis. However, the saptha Muni's according to Varahamihira are' Marichi, Vasishtha, Angirasa, Athri, Pulasthya, Pulaaha, and Kruthu'.
Thus 'Dhruva' clearly is Polaris. The saptha Rishi's are the seven major stars of Ursa major. 'Marichi' stands for Alkaid, 'Vasishta' stands for Mizar, 'Angirasa' stands for Alioth, 'Athri' stands for Megrez, 'Pulasthya' stands for Phecda, 'Pulaaha' stands for' Merak and 'Krathu' stands for DuBhe. The companion star for Mizar is Alcor. Hence 'Arundhathi' stands for Alcor. Vasishta and Arudhathi (Mizar-Alcor) can not be seen separate. The star Arundhathi is difficult to separate from Vasishta for people with poor eyesight.

Indian astronomers

Ancient astronomers are also called as rishis. Agasthya Rishi crossed vindhya mountains southwards and it is a major event in the vedic chrononlogy. A star in southern extreme is named after Agasthya or Canopus in constellation Carina.
There were many astronomers and many works have been lost. Few are discussed below: