Stellar Spectral Classes

Cards (49)

  • Who categorised the spectral classes used today?
    Annie Jump-Cannon
  • How many temperature classes did Annie Jump-Cannon create?
    Seven temperature classes
  • What are the spectral classes in order?
    • O
    • B
    • A
    • F
    • G
    • K
    • M
  • What intrinsic colour corresponds to spectral class O?
    Blue
  • What is the temperature range for spectral class O?
    25,00050,000 K
  • What prominent absorption lines are found in spectral class O?
    He, He, H
  • What intrinsic colour corresponds to spectral class B?
    Blue
  • What is the temperature range for spectral class B?
    11,00025,000 K
  • What prominent absorption lines are found in spectral class B?
    He, H
  • What intrinsic colour corresponds to spectral class A?
    Blue-white
  • What is the temperature range for spectral class A?
    750011,000 K
  • What prominent absorption lines are found in spectral class A?
    H (strongest), ionised metals
  • What intrinsic colour corresponds to spectral class F?
    White
  • What is the temperature range for spectral class F?
    60007500 K
  • What prominent absorption lines are found in spectral class F?
    Ionised metals
  • What intrinsic colour corresponds to spectral class G?
    Yellow-white
  • What is the temperature range for spectral class G?
    50006000 K
  • What prominent absorption lines are found in spectral class G?
    Ionised and neutral metals
  • What intrinsic colour corresponds to spectral class K?
    Orange
  • What is the temperature range for spectral class K?
    35005000 K
  • What prominent absorption lines are found in spectral class K?
    Neutral metals
  • What intrinsic colour corresponds to spectral class M?
    Red
  • What is the temperature range for spectral class M?
    Less than 3500 K
  • What prominent absorption lines are found in spectral class M?
    Neutral atoms, TiO
  • How does the intrinsic colour of a star relate to its temperature?
    • Intrinsic colour correlates with peak emission wavelength
    • Peak emission wavelength is determined by temperature
    • Described by Wien's law
  • What happens to atoms at low temperatures in stars?
    Not enough energy to excite atoms
  • What happens to atoms at higher temperatures in stars?
    Atoms have too much energy to form molecules
  • What is found in the atmospheres of the hottest stars?
    Hydrogen and helium in higher abundance
  • Why are the spectral lines of the hottest stars dominated by hydrogen and helium?
    Due to their higher abundance in atmospheres
  • What is the significance of the Balmer series in astronomy?
    • Involves electron transitions to/from n = 2
    • Wavelengths are in the visible spectrum
    • Important for studying hydrogen and helium
  • How does the prominence of Balmer lines vary among spectral classes?
    Depends on the surface temperature of stars
  • What is the prominence of Balmer lines in spectral class O?
    Weak
  • Why are Balmer lines weak in spectral class O?
    Star's atmosphere too hot for hydrogen
  • What is the prominence of Balmer lines in spectral class B?
    Slightly stronger
  • What is the prominence of Balmer lines in spectral class A?
    Strongest
  • What is the prominence of Balmer lines in spectral class F?
    Weak
  • What is the prominence of Balmer lines in spectral class G?
    Very weak / none
  • What is the prominence of Balmer lines in spectral class K?

    None
  • What stars are included in the Winter Triangle?
    Procyon, Betelgeuse, Sirius
  • What type of star is Betelgeuse?
    Type M star