1. Overview Flashcards
What types of radiation can be used to image stars?
X-rays, IR, optical
What are the two main forces acting on a star?
Thermal pressure outwards, gravity inwards
What are the two main forces acting on a molecular cloud?
Thermal pressure outwards, gravity inwards
What is the reason for the light and dark regions in the Milky Way?
Light regions: stars.
Dark regions: dust and gas in foreground - block light and do not emit at optical wavelengths.
What radiation does JWST detect?
IR
What type of stars does the Orion Nebula form?
Both high and low mass
What is one of the main challenges with imaging the Milky Way?
We are inside it
What galaxy is similar to the Milky Way that we can use?
The Whirlpool Galaxy
In an optical image of the Whirlpool Galaxy overlain with IR, what do the red and blue parts mean?
Red - where dust in concentrated
Blue - where stars are concentrated
When stars form, what length scale does the collapse go between?
~ 20,000 au to 1/200 au
When stars form, how many orders of magnitude does its size change?
Decreases by 6-7 orders of magnitude
How does density change during collapse to form a star?
Increases by 22 orders of magnitude
What force needs to win for a star to form?
Gravity
What is the reason for filamentary structure?
Turbulence (arises from mixing two viscous liquids)
Why does the ISM move faster than it should?
Turbulence
What stirs the gas and dust to cause turbulence?
Stellar winds, supernova shocks and collisions with other clouds
What triggers star formation?
Spontaneous - since P = nkT when the star cools thermal pressure decreases
Radiation pressure - feedback from other stars
Why may it seem that there are no other planetary systems like ours?
Observational bias
Transit method means if planet is bigger it creates bigger dip in light so is easier to see. Also, if closer to star, orbital period is shorter to more chance to see transit event.
Generally, how do stars form?
Via collapse of cold and dense molecular clouds in the ISM of galaxies
What does injection of energy into the ISM from young stars generate?
Winds, jets and outflows
What is a signature of accretion in young stars?
Being hot and bright
How do young stars grow?
Accreting material through a protoplanetary disk
What governs the formation of discs, outflows and jets?
Magnetic fields
How does planet formation occur?
Either core accretion
Or gravitational collapse of material in the protoplanetary disc
