Download Binary Star - Armagh Observatory

STEM for TY Teachers
Discovering Our Place in the
Universe
Day 2
Mark Bailey and Libby McKearney,
Armagh Observatory
H&S, Housekeeping etc.
 This is a non-smoking building
 Morning tea and lunch will be served:
 Fire alarm, fire escapes – I will lead you to our fire assembly point, please
remain there until I check your name off the register and only return here
when advised to do so.
 Please be aware of any trip hazards (trailing leads, steps etc.)
 Location of facilities
 Evaluation – please continue to fill out your evaluation form as we go through
today and tomorrow!
 Second form on your table.
Our Programme for Today
Reminder: Main Learning
Objective
To provide TY Teachers/Coordinators with
sufficient knowledge of astronomy and related
sciences to give them the confidence and skills to
introduce some aspects of astronomy to their TY
students.
“Earth’s Place in Space: Bringing
‘Heaven’ Down to Earth”
Talk by
Mark Bailey
Gap tasks!
Moon: Relative Size and Phases
Moon’s diameter (3476 km) is 27%, i.e.
roughly one quarter, that of the Earth
Lunar phases depend on relative
positions of Earth, Moon and Sun as
both Earth and Moon revolve around
the Sun …
Images from NASA
From RAS Leaflet
Moon: Orbit Always Concave
With Respect to Sun
Heliocentric View
New Moon
Last Quarter
Full Moon
First Quarter
Geocentric View
Orbit Around Common Centre of Mass:
Produces Two Tidal Bulges
From RAS Leaflet
From McCully “Beyond The Moon”
“Spring” and Neap Tides: Depend on
Alignment of Moon With Sun
Our Programme for Today
Outline Programme for Saturday in Armagh:
Please make your way to Armagh Planetarium
9:30
Planetarium Show, tour and discussion on bringing a school group
10:45
Short walk back to Observatory for tea/coffee at 11am
11:15
Sun, Stars and Galaxies
12:15
Q&A
12:30
Human Orrery (umbrellas possibly!)
13:15
Lunch in Observatory and observing the Sun/Moon outside if clear
14:00
Plenary, evaluation, return to soap-box.
14:30
End of course, free time in Armagh and return to Donegal.
As we hope to observe outdoors on Friday night in Armagh, please bring warm clothes
(warm coat, hat, scarf, gloves etc.) and binoculars if you have them.
Just in case, for the outdoor tours, please bring waterproof clothing, an umbrella and
comfortable, waterproof footwear!
Earthballs are funded by the RAS as part of its contribution to UNAWE education and
public understanding of astronomy.
Core Theme 4
Sun, Stars and Galaxies
Sun as a star; formation and origin of stars, composition
etc.; exo-planetary systems; other stars (single, binary
etc.); star clusters; galaxies; galaxy clusters etc.; and the
Universe (cosmology and new ideas).
Sun, Stars and Galaxies
The Nature of the Sun and Other Stars; Stellar
Evolution; the Content and Structure of Galaxies
and the Universe as a Whole…
Sun
Solar Wind and Magnetosphere
Aurora: Northern/Southern Lights
Different Types of Stars
 Main-Sequence Stars - Young Stars: These stars
produce energy through nuclear fusion as they convert
Hydrogen to Helium. Most stars (about 90%) are MainSequence Stars. For these stars, the hotter they are, the
brighter they are. The Sun is a typical Main-Sequence star.
 Dwarf Stars: The name “dwarf” can be used to describe
stars like our Sun, or tiny (Earth-size) “white dwarfs”, the
compact remnants of stars like our Sun. Some mainsequence stars can be up to 20 times more massive than
our Sun and much brighter.
 Yellow Dwarf Stars: Yellow dwarfs are main-sequence
stars like the Sun.
Hertzsprung-Russell Diagram
 Red Dwarf: The term “red dwarf” usually refers to a
small, cool, very faint, main-sequence star whose surface
temperature is under about 4,000 K. Red dwarfs are the
most common type of star. Proxima Centauri is a red
dwarf.
 Giant and Supergiant Stars – Evolved, Large Stars
 Red Giant: A red giant is a relatively old star whose
diameter is about 100 times bigger than it was originally,
and has become cooler (the surface temperature is
under 6,500 K). They are frequently orange in colour.
Betelgeuse is a red giant. It is about 20 times as massive
as the Sun, but about 14,000 times brighter than the Sun,
and about 600 light-years from Earth.

Betelgeuse
 Blue Giant: A blue giant is a huge, very hot, blue star.
It is a post-main sequence star that burns helium.
 Supergiant: A supergiant star is the largest known type
of star; some are almost as large as our entire solar
system. Betelgeuse and Rigel are supergiants. These
stars are rare. When supergiants die they explode as a
supernova and may produce black holes.
Eta Carinae and Humunculus
Nebula
Faint, Virtually Dead Stars:
White Dwarf: A white dwarf is a small, very dense, hot
star that is often made mostly of carbon. These faint stars
are what remain after a red giant star loses its outer
layers. Their nuclear cores are depleted.
They are about the size of the Earth (but around
200,000 times more massive). They will eventually lose
their heat and become a cold, dark black dwarf. Our Sun
will someday turn into a white dwarf and then ultimately a
black dwarf. The companion of Sirius is a white dwarf.
Comparison Between White Dwarf and
Earth: Extreme Matter
 Brown Dwarf: A brown dwarf is a "star" whose mass is too
small to have nuclear fusion occur at its core (the
temperature and pressure at its core are insufficient for
fusion). A brown dwarf is not very luminous. It is usually
regarded as having a mass between approximately 1/100
and 1/10 that of the Sun.
 Neutron Star: A neutron star is a very small, super-dense
star which is composed mostly of tightly-packed neutrons. It
has a thin atmosphere of hydrogen. It has a diameter of
approximately 10 km and a density of roughly ten million
billion times that of water.
 Pulsar: A pulsar is a rapidly spinning neutron star with a
very powerful magnetic field that emits energy in a very
narrow beam as it rotates, leading – like a lighthouse – to
intense pulses of observed radiation.
 Binary Stars: Many stars are found in pairs (binaries)
or multiple systems.
 Double Star: A double star is two stars that appear
close to one another in the sky. Some are true binaries
(two stars that revolve around their common centre of
mass); others just appear double because they happen
to lie along the same line-of-sight from Earth.
 Binary Star: A binary star is a system of two stars that
revolve around their common centre of mass (the
barycentre). About half of all stars are in a group of at
least two stars. Polaris (the pole star of the Northern
Hemisphere of Earth) is part of a binary star system.
Neutron Stars and Pulsars: Even More
Extreme Matter
Roughly same mass as the Sun
(2 x 1030 kg); roughly same size
as Halley’s comet!
 Eclipsing Binary: An eclipsing binary is two stars that
appear to be a single star varying in brightness. The
variation in brightness is due to the stars periodically
obscuring or enhancing one another. Such binary star
systems happen to be tilted (with respect to us) so that
their orbital plane is viewed from the edge rather than
face-on.
 X-ray Binary Star: X-ray binary stars are a special
type of binary star in which one of the stars is a
compact, evolved object such as a white dwarf, neutron
star, or black hole. As matter is stripped from the
normal star, it falls at very high speed onto the
collapsed star, producing X-rays.
 Variable Stars - Stars that Vary in Luminosity: Many
stars, even the Sun, can vary in luminosity. Some change
their light output by a very significant amount in a regular
way and can therefore be recognized at very great
distances. These can be used as “standard candles” to
estimate distances.
 Cepheid Variable Stars: Cepheid variables are very
luminous stars that regularly pulsate in size and change in
brightness. As the star rapidly increases in size, its
brightness increases; then, it slowly decreases in size
again, and its brightness falls.
 Because of their intrinsic luminosity Cepheid stars can be
seen millions of light years away and used to calibrate the
distance scale of the Universe. Polaris and Delta Cephei
are examples of Cepheids.
End of star types.
Nova and Supernova
 A supernova is a stellar explosion that is more energetic
than a nova. Plural supernovae or supernovas.
Supernovae are extremely luminous and cause a burst of
radiation that often briefly outshines an entire galaxy,
before fading from view over several weeks or months.
 During this short interval a supernova can radiate as much
energy as the Sun is expected to emit over its entire life
span. The explosion expels much or all of a star's material
at a velocity of up to 30,000 km/s (10% of the speed of
light), driving a shock wave into the surrounding
interstellar medium. This shock wave produces an
expanding shell of gas and dust called a supernova
remnant.
 Nova (plural novae) means "new" in Latin, referring to
what appears to be a new star shining in the celestial
sphere.
 Although no supernova has been observed in the Milky
Way since 1604, the number of supernova remnants
indicates that on average such an event occurs about
once every 50 years in the Milky Way.
 Supernovae play a significant role in enriching the
interstellar medium with the heaviest elements.
Furthermore, the expanding shock waves from
supernova explosions can trigger the formation of new
stars.
EXO Planets
 Exoplanets: an extrasolar planet or exoplanet, is a
planet outside the Solar System. By early 2012, more
than 700 extrasolar planets (in 571 planetary systems
and 81 multiple-planet systems) have already been
identified.
 A substantial fraction of stars have planetary systems data from the HARPS mission indicates that this
includes more than half of all Sun-like stars. Data from
the Kepler mission has been used to estimate that
there are at least 50 billion planets in our own Galaxy.
The first confirmed detection was in 1992.
Transit of Venus and demo of
blink method in school
Other life?!!
 Children will ask!
 ET?
 Recent US citizens’ petition to reveal if their
government really knew anything about aliens on Earth
– “No”!
 The discovery of extra-solar planets has intensified
interest in the possibility of extraterrestrial life.
Scientists look for the signature of water or chemicals
which may sustain or indicate life. Posters on various
web-sites (e.g. Observatory).
Microbes,
Nebulae
“Pillars of Creation” in the Eagle Nebula
Orion Nebula and Proplyds
Orion Nebula imaged from Armagh
(Simon Jeffery)
Space Telescope image of
protoplanetary discs in Orion Nebula
 Nebula – often very beautiful images! A nebula (from Latin:
"cloud" pl. nebulae), is an interstellar cloud containing largely
hydrogen, helium and other gases, as well as interstellar dust.
Originally, nebula was a general name for any extended
astronomical object, including galaxies beyond the Milky Way
(some examples of the older usage survive; for example, the
Andromeda Galaxy is still described as the Andromeda Nebula.
 Nebulae often form star-forming regions, such as in the Eagle
Nebula. This nebula is depicted in one of NASA's most famous
images, the "Pillars of Creation". In these regions the
formations of gas, dust, and other materials "clump" together to
form larger masses, which attract further matter, and eventually
become massive enough to form stars. The remaining materials
are then believed to form planets, and other planetary system
objects.
Galaxies of Different Types
Galaxy Types: Galaxies come in various sizes and
shapes. They can have as few as 10 million stars or as
many as 10 trillion. (The Milky Way has about 200 billion
stars). In 1936, Edwin Hubble classified galaxy shapes in
the Hubble Sequence.
 Elliptical: These have a faint, rounded shape, but
they're largely devoid of star-forming gas and dust, with
no visible bright stars or spiral patterns. Elliptical
galaxies probably comprise about 60 percent of the
galaxies in the Universe. They show a wide variation in
size - most are small (about 1 percent the diameter of
the Milky Way), but some are many times larger.
 Spiral: The Milky Way is one of the larger spiral
galaxies. They're bright and distinctly disk-shaped, with
star-forming gas, dust and bright stars in the spiral
arms. Because spiral galaxies are bright, they make up
most of the visible galaxies, but they're thought to make
up only about 20 percent of the galaxies in the
Universe.
Some Galaxy Images
 Irregular: These are small, faint galaxies with large
clouds of gas and dust, but often no spiral arms or
bright centres. Irregular galaxies contain a mixture of
old and new stars and many tend to be small, about 1
percent to 25 percent of the Milky Way's diameter.
 Some more galaxy images:
Spiral galaxy M31 in Andromeda
Giant elliptical galaxy Centaurus A
Gravity
 Every time you jump, you experience gravity. It pulls
you back down to the ground. Without gravity, you'd
float off into the atmosphere along with all of the other
matter on Earth.
 You see gravity at work any time you drop a book, step
on a scale or toss a ball up into the air. It's such a
constant presence in our lives, we seldom marvel at the
mystery of it but even with several well-received
theories out there attempting to explain why a book
falls to the ground (and at the same rate as a pebble or
a couch, at that), they're still just theories. The ultimate
cause of gravity remains a mystery.
 So what do we know about gravity? We know that it
causes any two objects in the Universe to be drawn to
one another. We know that gravity assisted in forming
galaxies and other structures in the known Universe,
that it keeps the Moon in orbit around the Earth and so
on.
 As for the science behind the action, we know that
Isaac Newton defined gravity as an attractive force, one
that attracts all objects to all other objects. However,
Albert Einstein said that gravity is the result of the
curvature of space-time. These two theories are the
most common and widely held (if incomplete)
explanations of gravity.
The Expanding Universe!!
 The Expanding Universe, the theory developed from the
observed correlation between the red shifts of celestial
bodies and their distances, suggests that the space
between galaxies is expanding. This causes distant
galaxies to appear to be moving away from us with a
speed that increases with distance, just like the
separation of dots on a balloon as you blow it up.
 Cosmology is the discipline that deals with the origin,
structure, and space-time relationships of the Universe.
Cosmologists study the Universe as a whole: its birth,
growth, shape, size and eventual fate. Modern cosmology
is dominated by the Big Bang theory, which brings
together observational astronomy and particle physics.
The Expanding Universe
 The Big Bang theory is the prevailing cosmological
model that explains the early development of the
Universe. According to the Big Bang theory, the
Universe was once in an extremely hot and dense state
which expanded rapidly. This rapid expansion caused
the young Universe to cool and resulted in its present
continuously expanding state. According to recent
measurements, observations and scientific evidence,
this original state existed around 13.7 billion years
ago, which is currently considered as the age of the
known Universe. Prior to the hot stage of the Big Bang,
a very short-lived earlier stage of Inflation is thought to
have occurred.
End of presentation.