Origins

How did everything form?

The origins of the universe are still uncertain. The most accepted hypothesis is : The “Big Bang Theory” (NOT the TV show!)

Most of what people know about the Big Bang is incorrect.  Watch this video, Origins of the Universe 101 by National Geographic.  As you do, note the following:

• Humans have been trying to figure out where we came from for a long time.
• The first element to form after the Big Bang was Hydrogen - a fact discovered by astronomer and astrophysicist Cecilia Payne
• How does the Scientific Method relate to our understanding of the Big Bang?
• The video explains how one event set the stage for another event, like dominos toppling over.  This will be a theme throughout the rest of this course.

How old is the Universe?  Find out on Space.com's " How Old is the Universe? " page!

We now have a Universe, complete with stars and their associated solar systems, black holes, and so on.  Stars, however, have a finite lifetime. There are many types of stars, and each type ‘dies’ in a specific manner.  The stars we need to eventually form planets are stars like our own Sun.  Towards the end of their lives, these types of stars will first become a Red Giant (or Supergiant), where the outermost layer of the star expands to nearly twice the star’s original size.  In our system, all the planets out to the asteroid belt will be destroyed.  The star then collapses upon itself, forming either a nebula or a supernova, spewing gases and matter outward to form a ginormous gas cloud.

Image source:  " Stelar Evolution " by Encyclopædia Britannica is licensed under CC BY-NC 4.0

The star has exploded . . . Now what?

One star explodes ⇒ creates a nebular ⇒ thousands of new stars!  (called a star nursery).

Some stars will form either an interstellar cloud or a nebula, in which new stars (and solar systems) are formed.  Check out the image below.  The Circinus Molecular Cloud Complex is 2,280 light-years away from Earth, located in the constellation of Circinus.  It's massive - nearly 180 light-years across and is 250 000x denser than our Sun.  A "molecular cloud" forms when the hot gas and dust in an interstellar cloud becomes cool enough that molecules will form, eventually leading to the formation of stars.

Image source:  "Star Formation in the Circinus Molecular Cloud Complex" by NASA/JPL-Caltech/UCLA is in the Public Domain

The dark patch behind the bright stars in the center of the image is the Circinus Molecular Cloud.  And those bright stars? One of them is IRAS 14568-6304, and it's a brand new star.  The glowing gas obscuring it is called a protostellar jet.

Image source:  "Violent birth announcement from an infant star" by ESA/Hubble & NASA is in the Public Domain

Awesome.  We have a star.  But, how did it form, and when does the solar system form?

Good questions!  Read on . . .