Back to the full dot-point answer

VICPhysicsQuick questions

Unit 2: How does physics help us to understand the world?

Quick questions on Astrophysics option: VCE Physics Unit 2 Year 11

15short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.

What is structure?
Show answer
Sun at centre. Eight planets: terrestrial (Mercury, Venus, Earth, Mars) and gas giants (Jupiter, Saturn, Uranus, Neptune). Dwarf planets (Pluto, Eris, Ceres).
What is distance scales?
Show answer
- Earth-Sun: 1 astronomical unit (AU) = $1.5 \times 10^{11}$ m. - Earth-Moon: $3.84 \times 10^8$ m. - Sun-Neptune: about 30 AU.
What is origin?
Show answer
Formed about 4.6 billion years ago from a collapsing molecular cloud (the solar nebula).
What is stars?
Show answer
Self-gravitating spheres of plasma producing energy by nuclear fusion. Hydrogen fuses to helium in the core (for sun-like stars).
What is classification?
Show answer
Spectral types O, B, A, F, G, K, M (hottest to coolest). Sun is G-type. Brown dwarfs are sub-stellar.
What is main sequence?
Show answer
Stars spend most of their lives fusing hydrogen. Position on the Hertzsprung-Russell (HR) diagram depends on mass; massive stars are hotter and more luminous but shorter-lived.
What is life cycle of a sun-like star?
Show answer
1. Protostar (collapsing nebula). 2.
What is supernovae?
Show answer
Released energy comparable to a galaxy's luminosity for weeks. Produce elements heavier than iron (which cannot form by fusion in normal stellar burning).
What is parallax?
Show answer
As Earth orbits the sun, nearby stars appear to shift against the background. The apparent angular shift (parallax angle $p$) gives the distance:
What is standard candles?
Show answer
Objects with known intrinsic brightness. Compare to apparent brightness to determine distance.
What is redshift?
Show answer
Light from distant galaxies is shifted to longer wavelengths (the Hubble flow). The redshift gives recession velocity; Hubble's law $v = H_0 d$ gives distance.
What is milky Way?
Show answer
Spiral galaxy, around 100,000 light-years across. About 200 billion stars. Sun is in the Orion Spur, about 26,000 light-years from the galactic centre.
What is local Group?
Show answer
Cluster of 50+ galaxies including Milky Way, Andromeda, and many dwarfs. About 10 million light-years across.
What is observable universe?
Show answer
About 93 billion light-years in diameter (due to expansion). 100 billion to 2 trillion galaxies. Filamentary large-scale structure with voids between.
What is hubble's discovery?
Show answer
Distant galaxies are receding from us, with velocity proportional to distance. The universe is expanding.

All PhysicsQ&A pages