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Variable Stars and the Stories They Tell


Massive object, typically comprised of mostly Hydrogen gas ... from their dusty and gaseous surroundings, these stars now become visible at ... – PowerPoint PPT presentation

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Title: Variable Stars and the Stories They Tell

Variable Stars and the Stories They Tell
  • Mike Simonsen
  • C. E. Scovil Observatory

Stars The Essential Building Blocks of the
What is a Star?
  • Massive object, typically comprised of mostly
    Hydrogen gas
  • Balancing act between gravitys contraction and
    nuclear burnings expansion
  • Mass is the most important quantity of a star
  • Initial mass determines its life cycle

Variable Stars
  • Stars that vary in brightness
  • Time scales of seconds, hours, days, years or
  • Understanding variable star behavior sheds light
    on other astronomical phenomena
  • General classifications or types

Pulsating variables
  • Light changes are related to the expansion and
    contraction of the stars atmosphere
  • Miras (LPVs)
  • Cephieds (standard candles)

Eruptive variables
  • Novae
  • Dwarf Novae
  • Supernovae

Eclipsing variables
  • Eclipsing variables are not intrinsically
  • The change in brightness is due to a line of
    sight effect

Stellar EvolutionThe Life Cycle of Stars
Star Birth
  • In the beginning a star condenses from a cloud of
    dusty interstellar gases
  • The life story of a star is the story of its
    perpetual attempt to contract

As the pillars themselves are slowly eroded away
by the ultraviolet light, small globules of even
denser gas buried within the pillars are
uncovered. These globules have been dubbed
"EGGs." EGGs is an acronym for "Evaporating
Gaseous Globules," but it is also a word that
describes what these objects are. Forming inside
at least some of the EGGs are embryonic stars
stars that abruptly stop growing when the EGGs
are uncovered and they are separated from the
larger reservoir of gas from whch they were
drawing mass. Eventually, the stars themselves
emerge from the EGGs as the EGGs themselves
succumb to photoevaporation.
From A Cloud of Gas
A Star is Born
Orion NebulaNearby star forming region
Variable stars within one degree of M42
T Tauri type stars
  • T Tauri stars are named for the prototype of the
    class, T Tauri. These objects are pre-main
    sequence stars and have recently emerged from the
    opaque envelope of stellar formation. Having
    recently coalesced from their dusty and gaseous
    surroundings, these stars now become visible at
    optical wavelengths.
  • Our own Sun presumably passed through the T Tauri
    stage some 4 1/2 billion years ago. Therefore,
    these stars may be able to offer us a peak into
    the evolution of our own Sun, solar system, as
    well as other planetary systems.

Middle Age
  • As stars evolve to middle age, they, just like
    people, tend to swell at the waist.
  • The instability strip on the H-R diagram
    represents stars in transition from one phase of
    their lives to another.
  • Many M class stars are red giants. Pulsating
    variable stars, like Mira.

Old AgePlanetary Nebulae
  • Planetary nebulae are formed when a red giant
    star ejects its outer layers as clouds of
    luminescent gas, revealing the dense, hot, and
    tiny white dwarf star at its core.
  • 95 of all stars that we see in our own galaxy
    will ultimately become "planetary nebulae". This
    includes the Sun.

Our Future Sun
V838 Mon
  • Originally classified as a nova, V838 Mon may be
    an entirely new class of nova. Luminous Red Nova
  • Other potential explanations
  • Thermal pulse of a dying star
  • Thermonuclear event within a massive supergiant
  • Mergeburst
  • Planetary capture event

Binary Star Systems
  • Stars in close proximity to each other can
    influence the evolutionary development of their
  • Symbiotic variable stars and cataclysmic variables

Cataclysmic Variables
Death and Destruction
Seeding the Universe
  • All the heavy elements in the universe were
    created inside the bowels of stars that have long
    since blown up or blown off their atmospheres.
  • We are indeed stardust.
  • We owe our very existence to variable stars.

Modeling Larger Scale Phenomena
  • Accretion disks
  • Star formation
  • Planetary formation
  • Galaxy formation
  • Active galactic nuclei
  • Black holes

The Search For Life
  • Find extra terrestrial planets
  • Exoplanet searches
  • Exoplanet transit observations
  • Serendipitous discoveries of variable stars

Amateur Contributions to Science
  • AAVSO American Association of Variable Star
  • Monitor pulsating variables
  • Observing cataclysmic variables
  • Timing eclipsing variables and RR Lyrae stars
  • Chasing after GRB afterglows
  • Observing exoplanet transits

Be a Part of the Story
Thank you!