Letting It AH

We now join a single fragment in the collapsing cloud that will become a 1-solar mass star. Over a period of perhaps a million years, the cloud fragment contracts. In this process, most of the gravitational energy released by the contraction escapes into space, because the contracting cloud is insufficiently dense to reabsorb the radiation. At the center of the coalescing cloud (where densities are the highest), more of the radiated energy is trapped and the temperature increases. As the cloud fragment continues to contract, photons have a harder

Giant molecular clouds are huge collections of cold (10 K to 100 K) gas that contain mostly molecular hydrogen. These clouds also contain other molecules that can be imaged with radio telescopes. The cores of these clouds are often the sites of the most recent star formation.

Star Words

Giant molecular clouds are huge collections of cold (10 K to 100 K) gas that contain mostly molecular hydrogen. These clouds also contain other molecules that can be imaged with radio telescopes. The cores of these clouds are often the sites of the most recent star formation.

Astro Byte

What causes a molecular cloud to collapse and form stars? We're not exactly sure, but there are several likely possibilities. The expanding shock wave of a nearby supernova explosion might be sufficient to cause a cloud to collapse. Or, as we'll see in the next chapter, a ripple in a galaxy called a density wave could also be the trigger. Some astronomers even think that a fast-moving massive star, punching through a molecular cloud, could cause parts of it to collapse.

Astro Byte

What causes a molecular cloud to collapse and form stars? We're not exactly sure, but there are several likely possibilities. The expanding shock wave of a nearby supernova explosion might be sufficient to cause a cloud to collapse. Or, as we'll see in the next chapter, a ripple in a galaxy called a density wave could also be the trigger. Some astronomers even think that a fast-moving massive star, punching through a molecular cloud, could cause parts of it to collapse.

and harder time getting out of the increasingly dense material, thereby causing the temperature at the core to rise even higher.

If the original fragment had any slight rotation (as undoubtedly it did), it will be spinning faster now—the spinning cloud is contracting, like the skater pulling in her arms. If the original giant molecular cloud was 10 to 100 parsecs across, then the first cloud fragments would still have been much larger than our solar system. Depending on the eventual stellar type, a cloud fragment on the verge of becoming a protostar might be somewhat smaller than our solar system. This stage of star formation is typically accompanied by dramatic jets of outflowing material. These objects have been dubbed Herbig-Haro objects.

Herbig-Haro objects are jetlike structures that appear to arise during the process of low-mass star formation. High-mass stars might experience very brief, scaled-up versions of these impressive outflows.

(Image from NASA, Alan Watson (Universidad Nacional Autonoma de Mexico, Mexico et al.)

Telescopes Mastery

Telescopes Mastery

Through this ebook, you are going to learn what you will need to know all about the telescopes that can provide a fun and rewarding hobby for you and your family!

Get My Free Ebook


Post a comment