Define the term galactic cluster- give an example
A cluster of roughly a few hundred young stars in a loose distribution. Also called an open cluster.
www.encyclopedia.com/doc/1G2-2830101489.html
Example: Seyfert Sextet
Source: http://upload.wikimedia.org/wikipedia/commons/2/20/Seyfert_Sextet_full.jpg
Define the term galactic supercluster- give an example
Superclusters are large groups of smaller galaxy groups and clusters and are among the largest structures of the cosmos.
en.wikipedia.org/wiki/Galactic_supercluster
Example: Virgo Supercluster
Source: http://www.fas.org/irp/imint/docs/rst/Sect20/A2a.html
E.6.2 Explain the red-shift of light from distant galaxies.
Why are the galaxies the furthest away red shifted the most?
Because the universe is expanding (the finding that the galaxies furthest away are red shifted the most implied the expansion of the universe).
"It is as if there was a big explosion, the outer parts flew off fastest and are still travelling outwards with the greatest speed and we are somewhere in the middle" Heinemenn HL Physics Course Companion
Video notes related to question:
Because on the large scale, expansion is causing everything to move apart.We know that its the expansion of space and not just the motion of the galaxy because every galaxy in every direction that we can observe is moving away from us. This does not mean that we're the centre of the universe however, observed from any point in the universe, one would observe that all galaxies are moving away. Space itself is expanding.
Below is an imagine from Tim Kirk's IB Physics Study Guide showing how, in this model, the redshift of light can be thought of as the expansion of wavelength due to the 'stretching' of space.
"It is as if there was a big explosion, the outer parts flew off fastest and are still travelling outwards with the greatest speed and we are somewhere in the middle" Heinemenn HL Physics Course Companion
Video notes related to question:
- Relationship between the distance of the galaxy and how fast it appears to be moving is known as Hubble's Law.
- As the universe expands it "drags" the galaxies along with it.
- Overall motion of galaxies away from us is due to the expansion of the universe.
- As the universe expands, the galaxies within it do not.
- Small scale --> gravity can hold things together. Large scale--> expansion takes over, causing everything to move apart.
- Astronomers are finding that the universe is expanding at an accelerating rate.
- Where is the centre of the universe? Either nowhere is the centre of our universe or everywhere is the centre of the universe.
Because on the large scale, expansion is causing everything to move apart.We know that its the expansion of space and not just the motion of the galaxy because every galaxy in every direction that we can observe is moving away from us. This does not mean that we're the centre of the universe however, observed from any point in the universe, one would observe that all galaxies are moving away. Space itself is expanding.
Below is an imagine from Tim Kirk's IB Physics Study Guide showing how, in this model, the redshift of light can be thought of as the expansion of wavelength due to the 'stretching' of space.
E.6.3 Solve problems involving red-shift and the recession speed of galaxies.
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