# Astronomy Basics – Earth, Sun and Moon

The basics of astronomy can be understood by looking at the prominent objects in the sky, such as the Sun and the Moon. Understanding how things at our planet get influenced by Sun and Moon is the first baby step one can take in astronomy. Ever wondered why planets, Sun, and our Moon are spherical? Large objects experience immense gravitational force. So the entire mass in such large objects gets evenly spread around the center, causing the round shape. Ever wondered why Sun is a star but Earth and Moon are not? Any object that is 0.08 solar masses or more experience a very high gravitational force. This results in the nuclear reaction in their core, making them stars. None of the planets or Moons in our solar system are close to that mass. So we have only one star in solar system, that is our Sun.

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## Written by MohanBabu

I am a marketing professional from India holding a postgraduate degree in management. My interests include travel, sports, astronomy, health, gardening, and photography.

• Not really Alex. Jupiter has 0.001 solar mass as against the minimum threshold of 0.08 solar mass to become a star. Jupiter needs to be 80 times more massive to qualify as a small star.

• drop all the moons in there, then saturn and all the other gas giants and all their moons and then see what we got…

1. Nicely done! I started looking to the stars as a child. The NASA moon landing had me entranced with what was out there beyond.

so which astronomical theory about the moon do you support?

That it once was part of the molten earth, knock-off by an asteroid
or that it was a separate body, captured by earth’s gravitational wave?

• It is improbable for Earth to capture such a large body like Moon had it been away. I would subscribe to the theory of a large mass being ejected out of Earth in the early stages of planet formation. Part of the ejected mass was captured by Earth’s gravity and became the Moon.

• That does in fact seem to be the most relevant/possible theory. I do agee with you!

• Thanks DocAndersen. You bring a new dimension to the discussions at Virily with your interests in technology and science.

• Thank you for the kind words. I return the compliment this is a great article in the science area!

2. Thanks for sharing the instructive information. I never thought about that. I learned something new.

• I am glad you find it informative Vidocka.

3. Always enjoy learning about astronomy.

• Thanks Carol. I am glad you liked it.

4. Astronomy has always been a taboo topic for me, my friend … I just don’t understand it and I don’t go into it anymore

• That is fine Lado. Astronomy does not appeal to everyone.

• This is too complicated and incomprehensible to me …. many things I do not understand, dear friend