Our Place in the Galaxy Flashcards
(12 cards)
What is the appearance of the Milky Way from Earth as seen with binoculars or a small telescope?
Using binoculars, the faint hazy patch of light resolves into a dense band of countless stars
Size and shape of the Milky Way, and the location of the sun, globular clusters, and sites of star formation
It is a spiral galaxy approximately 30 kPc across, with the sun about 10kPc from the centre. New stars are formed in the spiral arms, which are also packed with dust making them invisible. Globular clusters surround the galaxy in a halo.
How are 21cm radio waves used to determine the structure and rotation of our galaxy?
No visible light penetrates the dust filled arms. Fortunately, these arms contain hydrogen atoms which emit radio waves at a wavelength of 21cm. As the galaxy rotates, these ages are Doppler shifted, allowing us to determine its structure and rotation.
Name the group of galaxies gravitationally linked to the Milky Way.
The local group
What is the composition and scale of the local group?
It contains roughly 50 galaxies, roughly 50Mpc across. It includes Andromeda, The Milky Way, Lareg and Small Magellanic Clouds(satellite galaxies of the Milky Way), and the Triangulum Galaxy.
How to classify galaxies using the Hubble classification system
Ellipticals are filled, oval shaped galaxies. The number corresponds to decreasing circular-ness. (E.g. E0,E1)
Spiral galaxies have a circular centre with spiral arms, with letters corresponding to more wavy, speed out spirals (e,g. Sa, Sa)
Barred spiral galaxies have a straight ‘bar’ across them before the spiral. Like spirals, letters correspond to more wavy spiral (e.g. SBa, SBb)
The above three are placed on the tuning fork diagram, from ellipticals branching into the two spirals
Irregular galaxies are just weirdly shaped.
What type of galaxy is the Milky Way?
A barred spiral (SBb)
What are Active galaxies?
They are types of galaxies which emit large quantities of radiation as well as visible light. They contain an Active Galactic Nucleus (AGN) powered by a supermassive black hole
What are the different types of Active Galaxies?
Seyfert galaxies - which emit strongly in the IR, UV, and X-Ray regions
Quasars - which emit radio waves and have large redshiftfs
Blazars- compacted galaxies which have galactic jets that point towards us.
Information about AGNs can be obtain
From many regions of the electromagnetic spectrum
Why are galaxies grouped in large clusters and superclusters
Because they are pulled together by mutual gravity
What are the main theories for the formation and evolution of galaxies?
- Cast clouds of gas and dust collapsing gravitational to form, stars, which were pulled together to form galaxies
- Large lumps of matter clumping together in the early universe to form galaxies
Evidence suggests early galaxies were spirals, which merged together to form ellipticals.
