Space Physics Flashcards
Formation explained by accretion model
- Gravity attracts particles in interstellar gas and dust clouds.
- Clouds contain varied elements, with heavier ones closer to the center.
- Material rotation forms accretion disc around central protostar.
Elliptical Orbits and Conservation of Energy
- Objects in elliptical orbits around the Sun travel faster when closer to it.
- This is explained by the conservation of energy principle.
- As objects move closer to the Sun, their gravitational potential energy decreases, leading to an increase in kinetic energy and velocity.
- Conversely, as objects move farther from the Sun, their gravitational potential energy increases, causing a decrease in kinetic energy and velocity.
- This phenomenon demonstrates the balance between potential and kinetic energy to maintain a constant total energy in orbits.
Characteristics of Galaxies and Astronomical Distances
- Galaxies comprise many billions of stars.
- The Sun, our star, resides in the Milky Way galaxy.
- Other stars within the Milky Way are much farther away from Earth than the Sun.
- Astronomical distances are often measured in light-years, where one light-year represents the distance light travels in one year in the vacuum of space.
Definition:
Redshift
Redshift is the observed increase in the wavelength of electromagnetic radiation emitted from receding stars and galaxies.
Life Cycle of a Star
- Stars form from interstellar clouds of gas and dust containing hydrogen.
- A protostar forms when an interstellar cloud collapses, increasing in temperature due to gravitational attraction.
- A protostar becomes a stable star when gravitational attraction balances the outward force from high internal temperature.
- Stars eventually exhaust hydrogen fuel for nuclear reactions.
- Most stars expand into red giants, while more massive stars become red supergiants after converting most hydrogen to helium.
- Less massive stars form planetary nebulae with a white dwarf at their center after becoming red giants.
- Red supergiants explode as supernovae, leaving behind nebulae containing hydrogen and new heavy elements, with a neutron star or black hole at the center.
Definition:
Cosmic Microwave Background Radiation (CMBR):
Microwave radiation of a specific frequency observed throughout space is known as cosmic microwave background radiation (CMBR).
Determining Galaxy Velocity (v):
The speed at which a galaxy moves away from Earth can be found from the change in wavelength of the galaxy’s starlight due to redshift.
Define:
Hubble Constant (H₀):
is defined as the ratio of the speed at which a galaxy is moving away from the Earth to its distance from the Earth.
Calculating Galaxy Distance (d)
The distance of a far galaxy can be determined using the brightness of a supernova in that galaxy.
Current Estimate for H₀:
- The current estimate for H₀ is approximately 2.2 × 10^(-18) per second.
Equation:
Age of the Universe
d / v = 1 / H₀
