Stellar Nurseries Karena Fiore
Dec 16, 2015
What is a Stellar Nursery?
Also known as molecular clouds, a stellar nursery is a dense region in space where new stars are made. A stellar nursery is located within a nebula
These interstellar clouds have high concentrations of molecular hydrogen and helium.
Temperatures range from 10 to 30 K
History
Nebulas were first recorded around 150 AD by Ptolemy
The first true nebula was mentioned in 954 by Abd al-Rahman al-Sufi in his Book of Fixed Stars. The nebula was distinct from surrounding star clusters
Al-Sufi also catalogued other nebulas such as the Omicron Velorum Cluster and Brocchi’s Cluster
History
In the late 1700s, the Herschels published three catalogs that listed thousands of nebulas and star clusters they had found
An updated version of the Herschels catalog was published in 1888 by J.L.E. Dreyer The New General Catalogue (NGC) is a compilation of clusters,
nebulas, and galaxies
Ways a Stellar Nursery is Formed
A cloud of gas becomes so dense that it collapses under its own gravity
A shockwave from a supernova (ex. The Crab Nebula)
When a low-mass star has lost most of its material, its temperature increases and it emits UV radiation that will ionize the surrounding gas This is a planetary nebula
The Crab Nebula (NGC 1952)
Structure of a Stellar Nursery
It is composed of mainly hydrogen and helium There are trace amounts of the other elements (under 1%)
There is also plasma (ionized gas) within the nebula
Width of millions of miles to hundreds of light years across
Planetary nebulas have a central star
Star Formation
Interstellar clouds are at a state of hydrostatic equilibrium gas pressure and the internal gravitational forces balance each other
Certain events will happen to trigger star formation Molecular clouds collide
Shockwaves of a supernova explosion
Galactic collisions
This will trigger a gravitational collapse within the nebula
Star Formation
As a molecular cloud fragment collapses under gravity, it becomes a protostar This is the early stage of a forming star
When a protostar reaches 10 million K in its core, it becomes a main-sequence star It is now able to undergo hydrogen fusion
Stars
Stars are born in clusters because the cloud in which they are formed is thousands of times more massive than each star
Brand new stars are main-sequence stars
High mass stars expand to become giants and supergiants These stars fuse hydrogen, helium, carbon, oxygen, etc.
Low mass stars eventually become white dwarfs Outer layers of star have been ejected and nuclear fusion has ceased
Life Span of a Stellar Nursery
Nebulas exist for a few million years
The radiation pressure from new stars drive away the gas of a nebula The dissipated nebula cannot be considered a stellar nursery anymore
There is not enough concentrated hydrogen and helium gas to form new stars
Cat’s Paw Nebula (NGC 6334)
In September of 2013, a newly discovered stellar nursery was found approximately 5,500 light years from Earth
It was found with ArTeMiS, a wide-field sub-millimeter-wavelength camera It can sense interstellar dust grains that can be found inside a nebula
Bibliography
http://en.wikipedia.org/wiki/Star_formation
http://en.wikipedia.org/wiki/Molecular_cloud
http://en.wikipedia.org/wiki/Nebula
http://www.universetoday.com/65067/newly-discovered-stellar-nurseries-in-the-milky-way/
http://www.kidsastronomy.com/nebulae.htm
www.nasa.gov
Bennett, Jeffrey O. The Essential Cosmic Perspective. 5th ed. San Francisco: Addison-Wesley, 2009. Print.
http://news.discovery.com/space/astronomy/cats-paw-nebula-star-forming-region-vista-eso-130925.htm
http://en.wikipedia.org/wiki/Star