Learning Goals Students will: 1) understand the terms for
common celestial objects and define the physical properties of
each.
Slide 3
Success Criteria Students will display learning goals by: 1)
Defining the physical properties of each celestial object.
Slide 4
Common measurement systems used in Astronomy
Slide 5
Distances in Space 1 light-year (1 ly) = the distance light can
travel in one year = 9.467 x 10 15 m or 9.467 x 10 12 km = 23 668
200 000 return trips from here to Toronto = 236 169 970 trips
around the world. It takes light about 8 minutes to travel from the
Sun to our planet
Slide 6
Distances in Space 1) Astronomical Unit The average distance
from the Earth to the Sun (Earths orbit is not a perfect circle) 1
A.U. = 1.495 x 10 11 m = 1.495 X 10 8 km (about 150 million km)
Most conveniently used for measuring distances to planets or other
objects in our Solar System (far better than using kilometers) The
most distant planet (Neptune) is about 30 AU from the sun.
Slide 7
Distances in Space Parsec (pc) A parsec is calculated using the
following right triangle: If the base of the triangle (adjacent
side) is 1 astronomical unit (1 AU) and the opposite angle is 1
second, then the length of the opposite side is 1 parsec. 1 pc =
3.086 x 10 16 m = 3.261 light years (ly)
Slide 8
Distances in Space Methods of Measuring Distances 1) Parallax
The angle to the distant object is measured twice during a year.
The angle between the measurements can be used to find the
distance. Parsecs are often used when measuring distances with
parallax This method is used when measuring the distance to nearby
stars (usually less than a few hundred ly)
Slide 9
Distances in Space Methods of Measuring Distances 2) The Red
Shift. This method will be explained in detail when discussing the
Big Bang Theory (not the TV show). It is the light wave equivalent
of the Doppler Shift for sound waves. This method uses the speed at
which stars are moving away from the Earth. It is the most commonly
used method of determining the distance to stars.
http://www.youtube.com/watch?v=FhfnqboacV0 (excellent video 2:28)
http://www.youtube.com/watch?v=FhfnqboacV0 Astronomers look for the
hydrogen and helium lines in the spectrographs of celestial objects
(usually the two strongest sets of lines on the absorption
question)
Slide 10
Using the Red Shift to measure distances The most accurate way
to measure redshift is by using spectroscopy. By looking at the
spectra of stars or galaxies, astronomers can compare the spectra
they see for different elements with the spectra they would expect.
If the absorption or emission lines they see are shifted, they know
the object is moving either towards us or away from us. In the
image at right, the object is redshifted because the absorption
lines are all shifted towards the red end of the spectrum. This
object is moving away from us. Astronomers talk about redshift in
terms of the redshift parameter z. This is calculated with an
equation: z = ( observed - rest )/ rest where observed is the
observed wavelength of a spectral line, and rest is the wavelength
that line would have if its source was not in motion.
Slide 11
Sample red-shift data Rest Wavelengths of Hydrogen - Balmer
Series NameColor Wavelength (Angstroms) Alpha () Red6562.8 Beta ()
Blue-green4861.3 Gamma () Violet4340.5 Delta () Deep Violet4101.7
The normal wavelengths for the 4 most distinct lines in the
hydrogen (H) spectrum are listed in black The position of these
wavelengths is listed for galaxy 587731512071880746. Notice that
the values are all higher! Using the Hubble Constant (H o ) and the
equation: cz = H o d (c= speed of light, z = redshift, d=
distance), the distance to the galaxy can be determined. This
method can be verified (for objects closer than 100 ly) using the
parallax method. Wavelengths of Hydrogen - Balmer Series for a
distant galaxy Object ID # 587731512071880746 NameColor Wavelength
(Angstroms) Alpha () Red7220 Beta () Blue-green5360 Gamma ()
Violet4780 Delta () Deep Violet4500
Slide 12
Sample data z Time the light has been traveling Distance to the
object now 0.00007151 million years 1 million light years 0.10
1.286 billion years 1.349 billion light years 0.25 2.916 billion
years 3.260 billion light years.55.019 billion years 5.936 billion
light years 17.731 billion years 10.147 billion light years 2
10.324 billion years 15.424 billion light years 5 12.469 billion
years 22.322 billion light years 10 13.184 billion years 26.596
billion light years Notice how the absorption spectral lines shift
further to the red end as more distant objects are compared.
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Meteoroid A chunk of interplanetary rock or dust that can be
seen as a track of light in the sky as it burns up in the Earths
atmosphere. This is a constant occurrence in the Earths atmosphere.
These chunks are too small to survive the heat of friction as they
travel through the Earths atmosphere.
Slide 15
Meteorite an interplanetary chunk of rock after it impacts on a
planet or moon. More simply a meteoroid that hits a planet or moon.
Meteorites have to pass through the atmosphere to hit the Earth and
therefore must be fairly large. Meteorites of immense size have hit
the Earth one that was approximately 20 km across caused the
extinction of the dinosaurs.
Slide 16
Meteor a chunk of interplanetary rock that is much smaller than
an asteroid. More simply a meteoroid that is travelling through
space. The melted appearance of this specimen suggests that is
actually a meteorite. Most meteors were formed as the Solar System
formed and are chunks of debris left over from this process
geologists used meteors to date the age of the Earth and the solar
system as a whole. There are a great variety of Meteor types based
on composition iron rich, stony, stony-irons, chondrites (some rich
in carbon)
Slide 17
Meteors & meteorites Two typical meteors are show at far
left. The famous Barringer meteor crater (below) in Arizona is
almost 2 km across. A massive meteorite roared over the Russian
city of Chelyabinsk on Feb 15, 2013, shattering windows and
damaging buildings.
Slide 18
Meteor Showers Meteor occur at random intervals and we
generally refer to them as shooting stars There are particular
periods where the rate of meteor sighting increase dramatically
these are called meteor showers The name is somewhat misleading, as
1 meteor/minute would rate as a good meteor shower. Some meteor
showers happen at regular intervals. For example the Perseid meteor
show (named because the meteors seem to come from the constellation
Perseus) occurs every August and is the result of the earth passing
through the debris of the comet Swift- Tuttle.
Slide 19
Kitchener Meteorite This meteorite, weighing 202 grams, fell to
Earth at 8:30am on Sunday, July 12, 1998. It passed close to the
left shoulder of Orville Delong, who was walking up to the 6th tee
of the Doon Valley Golf Club in Kitchener (very close to the
Highway 401 overpass over the Grand River) The meteorite is
completely covered with a black fusion crust about 0.5mm thick.
This crust is formed of glass produced by the intense heat of
friction as the meteorite slowed down in the atmosphere The
interior of the meteorite is almost white, with particles of iron
scattered through it. It is scientifically described as a class L6
chondrite and it probably originated in a body in the asteroid belt
which lies between Mars and Jupiter. The Kitchener Meteorite was
sliced open and shows a black fusion crust of about 0.5mm and a
light coloured interior with particlees of iron scattered though
it.
Slide 20
Asteroids A minor planet or non- luminous chunk of rock that is
smaller than a planet, but bigger than a meteoroid that orbits a
star. A belt of asteroids can be found between Mars and Jupiter.
Some asteroids have been perturbed from their orbits and travel in
elliptical paths through the inner planets. Since many asteroids
would likely be rich in metallic elements, they are a target for
future exploration.
Slide 21
Comets An object orbiting the sun, often in a very eccentric
elliptical orbit. Comets have been given the nickname dirty
snowballs as they are composed mostly of ice and loose rocky
material. When the comets path comes close to the sun, the ice is
turned into vapour and is released in a long, luminous tail. The
tail points directly away from the sun. Often a smaller second
tail, points away from the direction of movement.
Slide 22
Comets Comets generally originate from a region of space called
the Oort Cloud. Some originate from the Kuiper Belt. When comets
pass near larger objects, their orbits are disturbed and they can
be directed towards the sun and form elliptical orbits. There are
some comets which now travel within the planetary orbits they must
have been pushed into these orbits. It is believed that many dwarf
planets found in the Kuiper Belt, including Pluto, have
compositions similar to comets. Comets have struck the Earth. It is
possible that the Tunguska Explosion of 1908 was a comet. Many
scientists believe that the source of water in our oceans was due
to comet impacts early in our planets existence.
Slide 23
The Oort Cloud The Oort Cloud is a hypothetical region that is
thought to stretch outward beyond the Kuiper Belt along the plane
of the Solar System. It is named for Dutch Astronomer Jan Oort who
proposed this region in 1950. This is a cloud of debris left over
from the formation of the Solar System and is the source of comets.
Astronomer theorize that it contains over a trillion long period
comets greater 0.6 km in size (some which take 50 million years to
orbit the sun). It is located beyond the Kuiper Belt The Oort Cloud
is located from 5000 to 100000 AU from the sun.
Slide 24
Moons A natural satellite that orbits a planet. Moons can
travel in very elliptical orbits. Only moons with sufficient mass
form spheres this is because they have sufficient gravity to form
this shape. Therefore all small moons are irregular in shape. There
are 4 moons larger than our moon in the Solar System, but relative
to its planet, Earths moon is by far the largest. Some moons are
larger than Mercury (a planet) The 4 largest moons of Jupiter
Slide 25
Slide 26
Planets The definition of a planet became a topic of great
interest in 2006, when the Pluto debate came up! As a result,
planets must meet the following criteria: 1. An object that orbits
the sun. 2. An object that is large enough to be spherical in shape
due to a sufficient amount of mass. 3. An object that has an orbit
that is not controlled by another planet. 4. An object whose orbit
has been cleared of asteroids by its gravity. 5. An object that
does not emit own light (and is therefore too small to be
considered a star). Many stars form binary systems in which two
stars orbit each other. Stars need a sufficient mass of Hydrogen to
generate enough gravity to start a nuclear fusion reaction.
Slide 27
Mercury eclipsing or Transversing the Sun
Slide 28
Pluto demoted Planet Due to this definition, Pluto was demoted
to the definition of Dwarf Planet. Pluto was discovered in 1930 and
was considered a planet until 2006. Pluto has a highly elliptical
orbit that is found tilted 17 from the plane of the other 8 planets
orbits. Its mass is only 1/20 that of Mercury (and therefore
lighter than the moon. Pluto orbit has a 3:2 resonance with
Neptune. Thus Pluto orbits three times for every two orbits of
Neptune. Neptunes gravity has locked Pluto into this resonance.
Some astronomers suggest that Pluto may actually be a very large
captured comet.
Slide 29
Pluto demoted Planet Pluto has a moon that is almost half its
size suggesting that it is a binary (dwarf) planet (two objects
revolving around each other). Four other smaller moons have since
been found. Plutos orbit is inclined 17 from the 8 planets. Plutos
orbit is retrograde (opposite spin direction to the 8 planets)
Slide 30
Planets The IAU (International Astronomical Union) at one point
even suggested expanding the number of planets to 12 (and counting)
They suggested making the largest asteroid Ceres a planet (Ceres is
the only spherical asteroid in the Asteroid Belt), keeping Pluto a
planet, and adding two more Pluto-like planets that were found in
the Kuiper belt Sedna and Eris. Since more Pluto-sized objects are
being found in the Kuiper Belt (Quaoar and Makemake to name two),
the number of planets would continue to increase. However, all of
the objects mentioned dont meet all of the criteria on slide 18.
Ceres has not cleared its orbit of debris and most Kuiper Belt
objects are in resonance with Neptune. Thus we are forever stuck
with 8 planets!
Slide 31
Dwarf Planets and the Kuiper Belt Large objects orbiting the
sun that do not meet all of the criteria on slide 18. Discovery of
dwarf planets in the Kuiper Belt started with Eris in 2003. It is
believed to be larger than Pluto. It is suggested that there may be
hundreds of dwarf planets in the Kuiper Belt most of them too
distant and non-luminous to be found. It is also suggested that
they have icy compositions similar to comets and Pluto.
Slide 32
The Kuiper Belt The Kuiper Belt is a doughnut- shaped ring,
extending just beyond the orbit of Neptune from about 30 to 55 AU.
Named for astronomer Gerard Kuiper. Short period comets originate
from the Kuiper Belt (those with orbital periods less than 200
years) It is also the host of many icy dwarf planets including
Pluto (also known as KBOs (Kuiper Belt Objects) or TNOs (trans-
Neptunian Objects))
Slide 33
Exoplanets There are now thousands of known exoplanets. Planets
that orbit other stars than the sun. The first exoplanets were only
found 25 years ago. They are found when they pass in front of a
star. The search is on to find an Earth- like exoplanet (especially
one that might support life)! Many have been found by the Kepler
Spacecraft. This will be a separate topic for the discussion of
potential life outside of Earth.
Slide 34
Exoplanets as of October 2013
Slide 35
Stars a self-luminous ball of gas that shines or has shone
because of a nuclear fusion reaction in its interior. Extreme
temperatures (several million K (kelvin)) and pressures are
required to ignite a fusion reaction. The sun is our closest star.
There are many types of stars that you will learn about in lessons
this coming week so I will not get into details at this time! The
colour and size of a star can tell an astronomer a great deal about
its lifespan and ultimate future. Stars emit light due to the
fusion of lighter elements into heavier elements. The vast majority
of stars are fusing Hydrogen into Helium.
Slide 36
Infrared image of the Sun. Coronal Mass Ejection (Solar Flare)
and several sun spots. An artists rendering of neutron star drawing
gas from a companion star that is in orbit. This is often a prelude
to a Type II supernova
Slide 37
Slide 38
Slide 39
Constellations Ancient astronomers grouped these stars to form
creatures and objects that we call Constellations. Predicting your
behaviour or future based on these constellations (particularly the
12 constellations called the Zodiac) is called astrology. Astrology
is NOT a science. The stars in a constellation are not necessarily
located in a group or a star-cluster.
Slide 40
Zodiac Constellations The position of Zodiac constellations and
their appearance in the sky.
Slide 41
Nebula Interstellar region of gas and dust If enough gas and
dust are present, gravity will draw the dust together (over
millions of years) and the material could pull together to form a
star or a cluster of stars. (Our Solar System formed like this)
Nebulas can either emit light, absorb light or reflect light.
Nebulas can also result from the explosion of a star (Nova or
Supernova). Gases from the star are expelled into space. A small
remnant star can be seen in the middle of expelled gas in the
Hourglass Nebula
Slide 42
Slide 43
Slide 44
Galaxy A collection of stars, gas, and dust bound together by
gravity. (all other celestial objects will also be found) The
smallest galaxies may contain only a few hundred thousand stars,
while the largest galaxies have thousands of billions of stars.
Galaxies can be classified based on their shape - this also gives
information about their age! Galaxies rotate about a central point
the Milky Way galaxy takes 220 million years to rotate.
Slide 45
Milky Way Galaxy Our sun is found in the Milky way Galaxy. We
can see the Milky Way at night in a sufficiently dark place (cities
produce too much light). The Milky Way galaxy contains 200 - 400
billion stars and is about 120,000 light years across.
Slide 46
Slide 47
The Milky Way Galaxy The Milky Way galaxy contains our solar
system. Galaxies come in a variety of shapes (which are indicative
of their age and size), but we will discuss this in more detail
later in the course.
Slide 48
Galaxies Images from the Hubble Space Telescope and other types
of modern telescopes show that the Universe contains billions of
galaxies. The Hubble Deep View Telescope provides images of
thousands of galaxies in a single frame. (bottom picture)
Slide 49
Neutron Stars and Pulsars A star that has a mass of 1.5 to 3.0
times the mass of the Sun but a radius of only 10 km. It is the
result of the gravitational collapse of a large star! This collapse
has crushed all matter into neutrons. A teaspoon of a neutron star
would weigh thousands of tons. If the neutron star emits jets of
matter and energy in a pulsating fashion, it is known as a pulsar.
Pulsars spin rapidly and jets of material are often ejected from
the poles of the pulsar.
Slide 50
Black Hole a region in space from which, according to the
general theory of relativity, neither light, radiation, nor matter
can escape. Obviously we cannot see Black Holes, but we can infer
their existence from the behaviour of stars and other objects
nearby. Black holes have immense gravity and suck in stars and
other material that get too close to their gravity wells. It is
believed that a supermassive black hole exists in the middle of our
galaxy (and the middle of most galaxies. The black holes continue
to get larger as they suck in more and more material.
Slide 51
Novas When a star dies, the nuclear reaction in the core stops.
Since the outward force no longer exists, the star collapses onto
itself due to its force of gravity. This collapse is called a Nova
and can be seen from the outer layers of gas ejected from the
imploding star (A nebula forms that is illuminated by the collapsed
star within). When a small star goes Nova, it leaves behind a small
star called a white dwarf and a nebula. Our sun will follow this
route (I am simplifying this process I will add more detail later).
As stated before, when a star that has a mass of 1.5 to 3.0 times
the mass of the Sun goes Nova it will leave behind a neutron star
and a nebula.
Slide 52
Black Holes and Supernovas Black holes can only form from the
collapse of supermassive stars. (Those with a mass of more than
about 10 solar masses). The explosion will form a supernova. The
energy released in a supernova is so great that the supernova will
outshine every other object in the galaxy for a period of a few
weeks. We have only observed two supernovas in our own Galaxy. The
core of a supernova may become a black hole if there is sufficient
mass.
Slide 53
Supernova The explosion of a star with the resulting release of
tremendous amounts of radiation (energy) and dust. They only form
from the explosion of very massive stars and leave behind neutron
stars or black holes. Elements heavier than iron generally only
form from supernovas. A supernova will briefly outshine all other
stars in a galaxy. The Crab Nebula is the remnant of a supernova
recorded by Chinese astronomers in 1054. It was exceedingly bright
in the night sky for years after.
Slide 54
Slide 55
Quasar Quasars or quasi-stellar radio sources are the most
energetic and distant members of a class of objects called active
galactic nuclei. Scientists believe they are found at the centers
of super-massive galaxies and surround supermassive black holes.
They release so much energy, they outshine entire galaxies over
many EM wavelengths. They are extremely distant, among the most
distant objects in the universe and likely formed shortly after the
Big Bang (creation of the universe)