Download 11.3 Measuring Distances in Space

Measuring
Distances in
Space
Sizes of Objects in the Universe
Quarks (parts of neutrons and protons)
are the smallest objects at 10-18 m while
our universe is estimated to be 1026 m.
This is a total difference of 1044 from
smallest to largest things in our
universe.
Astronomical Units (AU)
1 AU is the distance from Earth to our Sun (150 000 000 km).
This distance works well to measure objects within our Solar
System but for distant stars and galaxies, it is too small of a
distance unit.
The Light-Year
One light-year is the distance that light will travel in one year.
It is 9 500 000 000 000 km or 9.5 trillion km. One light-year is
about 63 000 AU. Distances to other stars and galaxies are
measured in light-years.
Distance to Proxima Centauri
Proxima Centauri, a dim red dwarf, is the nearest star from
our sun. It is 4.2 light-years away which means that the light
we see from Proxima Centauri today started on its way 4.2
years ago (is 4.2 years old). This star is so dim it can only be
seen through a telescope. It is the red object in the centre of
the picture.
Distances Within our Milky Way Galaxy
Our galaxy, the Milky Way Galaxy is about 100 000 light-years
in diameter. It takes 100 000 years for light to cross from one
side to the opposite side of our galaxy.
Andromeda Galaxy
The distance to Andromeda galaxy, the nearest spiral galaxy
to our Milky Way galaxy is 3.5 million light-years. The light
we see today from Andromeda took 3.5 million years to get
here, it is 3.5 million years old!
Milky Way
Andromeda
Determining Distances by Triangulation
The distance to a far away object can be determined by
measuring two angles and the distance between those two
angles. A line (called a baseline) is laid out and angle
measurements are taken at the baseline endpoints to the
distant object. Geometry and Trigonometry are then used to
determine the perpendicular distance from the far away
object to the baseline.
Parallax
Parallax is the apparent difference in position of an object
against a distant background due to a change in position of
the observer.
Stellar Parallax
If a star is viewed against a distant background at one “side”
point in the earth’s orbit around the sun and then six months
(1/2 an orbit) later, the star will appear to have moved slightly
against the distant background. This is Stellar Parallax.
More
Distant
Objects
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Parallax
The Parallax Angle
Astronomers measure angle p as the
parallax angle. The distance in parsecs is
computed by the formula, d = 1/p (in
arcseconds). One parsec is 3.26 lightyears (about 31 trillion km) and one arc
second is an angle of 1/3600 th of a degree.
For example, Proxima Centauri has a
parallax angle of .7687 arc seconds. It’s
distance is 1/.7687 = 1.3009 parsecs.
1.3009 parsecs X 3.26 light-years/parsec =
4.243 light-years.
The Parallax Method has Its Limits
Parallax can now be used for star distances up to 1,600 lightyears using the Hipparcos satellite. In 2012, a new satellite
(Gaia Mission) will measure star distances up to 10,000 light
years.
Hipparcos
Gaia
Measuring Distances Over 2000 Light-Years
Astronomers use Cepheid Variable Stars, Supernovae and
degree of Red Shift for measuring stars at great distances
(beyond 10 000 Light-Years).
Summary of Methods for Measuring Distances
God is Beyond Measure. Man is Insignificant, Yet Cared For
“When I consider your heavens, the work of your fingers, the
moon and the stars, which you have set in place, what are
mere mortals that you are mindful of them, human beings
that you care for them?” Psalm 8: 3-4
In the Immense Universe, Humans Have Dominion Here
“You have made them a little lower than the heavenly beings
and crowned them with glory and honour. You have made
them rulers over the works of your hands.” Psalm8: 5-6
God Redeems and Forgives Us
“God does not treat us as our sins deserve or repay us
according to our iniquities…As far as the east is from the
west so far has he removed our transgressions from Him.”
Psalm 103: 10, 12. How far is our sin removed?
What Does the Vastness of the Universe Teach?
Despite our smallness, the universe declares the greatness of
God’s love. His love removes our sins beyond the ends of
our universe for each one of us! “For as high as the
heavens are above the earth, so great is His love for those
who fear him. Psalm 103: 11
End of Presentation
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