Chapter 15 Flashcards
How can we measure the Sun’s Orbital Radius?
using the Sun’s orbital properties and Newton’s version of Keppler’s third law
What does most of the galaxy’s mass consist of? How do we know?
- dark matter
- Orbits of the stars in the centre of the Milky are not faster in the centre. Instead they are all relatively constant suggesting something else with greater gravitational pull located throughout the MW is keeping speeds constant. That SOMETHING is suspected to be dark matter.
Why do we see virtually no gas or dust in the halo?
Because it is mostly dark matter
We suspect dark matter is made partly of______ which could pass RIGHT through you (shiver)
Axions
How is star stuff recycled:
- ______ _______ collapse due to ________ and give birth to stars
- stars shine for a long ‘effin time with energy produced by ________ ________
- After death the star returns much of their material _____ __ __ ________ ______.
- INTERSTELLAR CLOUDS collapse due to GRAVITY and give birth to stars.
- stars shine for a long ‘effin time with energy produced by NUCLEAR FUSION.
- After death the star returns much of their material BACK TO THE INTERSTELLAR MEDIUM.
Is all star material recycled?
-NO NOT ALL OF IT. SOME STAYS AS THE CORPSE OF BROWN DWARFS AND/OR CORPSES OF STARS (EW!)
How is the star stuff returned to the interstellar medium?
via interstellar winds which create bubbles of hot gas. These create shock fronts that gather up surrounding gas as it travels OR they pop spreading stuff everywhere.
Once the star stuff is returned to the interstellar medium it begins to ______&________ as it merges with ______ ______ gas and form atomic hydrogen clouds. The two combine to make ________ ________.
Once the star stuff is returned to the interstellar medium it begins to COOL &SLOW as it merges with ATOMIC HYDROGEN gas and form atomic hydrogen clouds. The two combine to make MOLECULAR CLOUDS.
Where are stars born
Molecular clouds
What clears out left over interstellar gas and dust of molecular clouds that isn’t popular enough to be included in the creation a new star?
-killed by radiation from the newly forming stars - the ultimate bullies
REVIEW OF THE STAR-GAS-STAR CYCLE:
- Big stars burn long time - JUNO?
- Interstellar winds stir up shit like bubbles that either pop and spread stuff everywhere, or create shock fronts that gather up stuff and sweep stuff away.
- Bubbles n stuff cool and slow as they mix with atomic hydrogen
- the atomic hydrogen and bubble stuff combine to form atomic hydrogen clouds.
- atomic hydrogen clouds cool further to become molecular clouds which give birth to stars.
- Radiation from new stars ‘take out the trash’ and clear up leftover interstellar gas and dust.
Read it again…with an accent…obviously
Most of the gas in the Milky Way is made up of?
(It’s like the Switzerland of cosmic gas)
How much of the galaxy’s total mass?
- ‘Cool, neutral’, hydrogen gas called “atomic hydrogen”.
- about a ‘couple percent’.
Interstellar dust grains are made of …
flecks of carbon & silicone that resemble smoke
What are the different colours in the Milky Way generated by?
ionization of different elements produce a variety of spectral lines
Blue tints are caused by…and indicate…because
- caused by reflection of star light on dust grains similar to the reason our sky is blue.
- blue tinges in the spiral arms indicate high star formation activity as blue stars don’t live long so there is a lot of recycling activity
The star population of the Milky Way is divided into…
TWO:
Disk (pop #1) & Halo (pop #2)
What kind of star is the sun
a disk star
How can we see a complete picture of the STAR-GAS-STAR CYCLE
viewing it through many different wavelengths
waves of star formation that spread through our galaxy
spiral arms
Any model of our galaxy must account for…. The simplest model shows it beginning in a ________ _________.
…differences between disk stars and halo stars.
-protogalactic cloud
What does a protogalactic cloud contain?
What happens as it collapses?
What happens with remaining gas?
- only hydrogen & helium
- halo stars begin to form
- remaining gas continues to collapse settling into a disk shape thanks to angular momentum
What caused disk stars to have a uniform motion and movement/direction of orbit?
collisions among gas particles
What evidence challenges the single protogalactic cloud model?
What other option?
Proportion of heavy elements in halo stars should then grow in concentration as they get closer to the centre of the galaxy- but they don’t.
-maybe there was a bunch of little clouds that collided to make a big one later? Maybe God really does exist cause this science shit doesn’t seem to be doing the job? 50/50 chance really ; )
Which stars have the highest concentration of heavy elements?
(Think heavy metal)
young ones. Typical. Kids these days.
- at the centre of the bulge (galactic centre) evidence suggests there is a…
- What shows us this
giant black hole.
is it just me or does it seem like we are just circling a great big drain?
-using radio, infrared and ultraviolet telescopes.
Why can’t we see the giant black hole in the galactic centre?
view is obscured by dust and clouds of gas
The centre of the Milky Way is located near
the tip of the spout on the Sagittarius constellation
What evidence suggests we are circling a big black hole?
a collection of stars circling something that is about 4 million times more massive than the sun, within about 1 light year of each other. CREEPY kinda
could we exist if stars were not organized into galaxies.
why?
- no
- who cares
The diameter of the MWG is
about 100,000 light years
components of the MWG
disk, halo, bulge, spiral arms
The halo contains a bunch of cold gas - T/F
F- has a bunch of hot
the disk contains an interstellar medium of
gas and dust
Orbital motions of stars in the galaxy allow us to determin
the distribution of mass in our galaxy
Why does ongoing star formation lead to a
blue-white appearance
Short-lived blue stars outshine others.
