Stellar Evolution and Characteristics
What is the initial material for all stars, and what force causes this material to collapse?
[Stars begin as large clouds of dust and gas (mostly hydrogen) known as a nebula. The force that causes the nebula to collapse is gravity.]
What unit of measurement is defined as the distance light can travel in one year, and is this unit used to measure distance or time?
This unit is the light year (ly). It is a unit of distance.
Which type of orbit allows a satellite to appear motionless relative to the ground, making it useful for communication purposes?
Geostationary Orbit (GSO)
What element makes up approximately 75% of all matter in the universe, and how do astronomers use spectral lines to confirm a star is made of this element?
[The most common element in the universe is hydrogen. Astronomers identify hydrogen by comparing the dark lines in the star's absorption spectrum to the known line pattern of the element's emission spectrum.]
What fundamental process in a star's core releases massive amounts of energy, and what elements are typically involved in the beginning of this process?
The process is called Nuclear Fusion. This occurs when light atoms combine and become heavier ones, specifically fusing hydrogen to form helium.]
How can astronomers use the concept of parallax to determine which of two observed planets is closer to Earth?
[The closer an object is to the observer, the more it will appear to move (greater apparent shift) against the distant background stars when viewed from two different positions in space.]
Describe the difference between the two parts of the shadow cast during an eclipse.
[The two shadow types are the Umbra (the fully shaded inner region, which is the darkest) and the Penumbra (the partially shaded outer region, which is the lighter shadow)
Differentiate between an Emission Spectrum and an Absorption Spectrum based on how they appear and what they are caused by.
[An Emission Spectrum shows colored lines of light emitted by a glowing gas. An Absorption Spectrum shows a pattern of colours with dark lines, caused when light from a continuous source passes through cooler gas, and the gas absorbs certain wavelengths.]
Explain the "battle" that defines a star's size and stability during its lifetime, naming the two opposing forces.
[The Stellar Life Cycle is a battle between two forces: the force of gravity pulling inwards (determined by the star's mass) and the pressure from heat pushing outwards (generated by fusion of heavier elements).]
Communication signals from NASA's InSight lander on Mars must travel a distance of 4.32x10^11 m to reach Earth. Given the speed of light is 3x10^8 m/s,
How long (in minutes) does the signal take to travel this distance?
24 minutes
What must be aligned in space to cause a Spring Tide, and what characteristic defines this type of tide?
Spring Tides occur when the Sun, Earth, and Moon are aligned. This alignment results in the highest tidal range
If astronomers observe light from a star showing a significant shift towards the red end of the spectrum, what is this phenomenon called, and what does it indicate about the star's motion relative to Earth?
[This phenomenon is called Red-shift. It indicates that the star is moving away from the observer.]
The Sun is classified as an average star. What stellar death outcome is predicted for the Sun, and what two distinct objects can massive stars leave behind after exploding?
[Average stars like the Sun will end their life as a White Dwarf. Massive stars explode as supernovas, leaving behind either a Neutron Star or a Black Hole.]
Explain the core reason why observing a distant galaxy, such as GN-z11 (whose light took 13.4x10^9 years to reach Hubble), is described as "looking back in time."
[Light travels at a constant, finite speed. When we see light from a distant object, that light was emitted a long time ago. Therefore, the more distant the object, the older the light we see, meaning we are looking further back into its past.]
If you were tasked with developing a satellite to continuously monitor weather patterns over London, UK, which of the three main orbit types would you choose (LEO, MEO, or GSO), and why?
[You would choose Geostationary Orbit (GSO). This is because GSO satellites appear motionless relative to the ground, allowing continuous coverage of a fixed geographical area like the city of London.]
On the Hertzsprung-Russell (H-R) Diagram, describe the general relationship between a Main Sequence star's surface temperature and its brightness (Luminosity). Where are the coolest stars found on the diagram?
[On the Main Sequence, the general relationship is that as temperature increases, brightness (Luminosity) generally increases. The coolest stars are found on the right side of the graph (and are typically red).]
What determines the fate (death outcome) of a star (white dwarf, neutron star, or black hole), and why is the surface temperature of White Dwarf stars generally much higher than Red Supergiants, despite White Dwarfs being later-stage stars?
[The crucial property that determines the death outcome of a star is its mass. White Dwarf stars would have a higher surface temperature than Red Supergiants because a change in size indicates a change in core temperature, and White Dwarfs are the hot, dense remnants of an average star's core.]
Voyager 1 is currently located 148 AU away from Earth (where 1 AU = 1.5x10^11 m). Convert this distance into metres and then calculate how many hours it takes for a signal from Voyager 1 to reach Earth, given the speed of light is 3x10^8 m/s.
= 20.6h
Explain the critical observation Edwin Hubble made regarding the relationship between distant galaxies and red-shift, and what monumental conclusion about the universe was drawn from this evidence?
[Hubble found that all distant galaxies were red-shifted, and crucially, the more distant the galaxy, the greater the red-shift. The conclusion drawn from this evidence is that the universe is expanding, which led to the theory known as "The Big Bang".]