levo

Space

The life cycle of stars

  • 2 things to know
  • Papers 2 and 3

Overview

Recall questions on the energy source of a main-sequence star, what keeps it stable, how a Sun-like star moves off the sequence, and why the most massive stars are the shortest lived.

What you need to know

Answer each one before you reveal it.

Your recallNot started
Process

What is the energy source of a main-sequence star, what keeps it stable, and where does a Sun-like star end up?

Numbers

Two stars have the same luminosity but different surface temperatures. How do their sizes compare?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is the energy source of a main-sequence star?

    Model answer

    Nuclear fusion of hydrogen into helium in its core.

  2. 2

    What keeps a main-sequence star at a stable size for most of its life?

    Model answer

    The outward pressure from the hot radiating core is balanced by the inward gravitational attraction of the star's own mass.

  3. 3

    How does a star begin its life?

    Model answer

    A cloud of gas and dust collapses under gravity, heating as it contracts until the core is hot and dense enough for hydrogen fusion to begin, at which point the star joins the main sequence.

  4. 4

    Where would a protostar lie relative to the main sequence, and which way does it move?

    Model answer

    It lies to the right of the main sequence, being cool but luminous because of its size, and it moves leftwards as it contracts and heats up.

  5. 5

    How does a star like the Sun move across the diagram once it leaves the main sequence?

    Model answer

    As core hydrogen runs out the star swells and its surface cools, so it moves up and to the right into the red giant region.

  6. 6

    What is a planetary nebula?

    Model answer

    It is the shell of outer gas layers thrown off by a dying red giant, leaving the hot core exposed.

Other ways to work this

The same content, four other ways.

What is inside Levo

Six ways to work the same material.

1Closed book
2Open book
3Closed book

The 3-step method, run for you

Answer cold, learn it, then prove it stuck. Levo tracks the jump between your first attempt and your last.

Working as a Physicist
Mechanics
Electric Circuits
Materials

Cram a whole paper in one sitting

Sort every topic into what you know and what you do not, then drill only the weak ones.

The gradient gives the .
accelerationvelocitydisplacement

Blank Blitz makes facts automatic

Rapid timed gap-fills on the terms and numbers you need to recall without thinking.

AThe equation is s = (u + v)t/2.
BThe equation is v = u + at.
CThe equation is s = ut + ½at².

Build It gets the exam shape right

Assemble a full-mark answer from its marking points, in the order an examiner wants them.

Speed means rate of change of distance.
TrueFalse

Test It catches misconceptions

Spot the fault in a statement. The traps are the mistakes students actually make.

721941163128510

Brain Breaks between sessions

Short focus games to reset attention, so the next set lands better than the last.

Every question in Space, on a schedule.

Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.

Or £46 a year, about £3.83 a month. Cancel anytime.