EARTH AND THE SOLAR SYSTEM
The Size and Distance Scale Of The Solar System
•
Our Earth is just one of several Planets that revolve around our
Sun, the primary and central object of our Solar System.
•
Since the entire Solar System, including our Earth, was created
about the same time (about 4.6 billion years ago), our understanding
of the origin and properties of the Solar System, the Sun, and its
other members are important to our understanding of Earth itself.
•
We consider the size of our Earth to be very large, in comparison
with most sizes and distances we deal with in our daily lives.
However, the size of the Earth is very small compared to the size of
the Solar System, which consists of the Sun and its family of
planets, of which our Earth is only about average in size.
•
EARTH AND THE SOLAR SYSTEM
The Size and Distance Scale Of The Solar System
• When we observe the night sky, the planets, stars and
galaxies appear to be close together.
Remember:
• some objects are closer to the Earth than others
• enormous distances separate us from other objects in the
universe.
• As we gather information from the farthest reaches of the
universe, we can learn about the history of the universe.
The Size and Distance Scale Of The Solar System
•
In turn, the size of our Solar System is very large compared to the
size of our Earth, or even the largest planet, Jupiter.
•
The distance from our Earth to the Moon:
238,000 miles or 384,000 kilometers
(nearly 100 times Earth’s diameter, or about 30 times
the Earth at its equator)
•
the distance around
The distance from our Earth to the Sun:
93,000,000 miles or 149,600,000 kilometers
(more than 390 times the distance to the Moon)
•
The most distant major planet from the Sun, Neptune, is 30 times
Earth’s distance from the Sun.
•
The nearest stars in our Galaxy, the star system of Alpha Centauri, is
9,000 times Neptune’s distance from the Sun!
Why don’t we use the kilometer?
• kilometer is just too small to be useful
• numbers become so large that it becomes hard to
write and hard to interpret
• so astronomers use other units of distance.
• next nearest big galaxy- the Andromeda Galaxy
– 21 quintillion km
– 21,000,000,000,000,000,000 km.
Units of Measurements
• light-year
• AU
• parsec
light-year
• A light-year is a unit of distance.
– distance that light can travel in one year.
• Light moves at a velocity of about:
– 300,000 kilometers km/ second (299,792 km/second)
– 186,000 miles/second (186,282 miles/second)
• In one year, it can travel about:
– 10 trillion km or
– 5.8 trillion miles
• More precisely, one light-year is equal to:
9,460,000,000,000 km
– 9.46 x 1012 kilometers
light units
http://www.youtube.com/watch?v=Rj1sDWjvgjM
Units of Light Measurement
• Visible light travels 186,000 miles per
second
– Light second =
Units of Light Measurement
• Visible light travels 186,000 miles per
second
– Light minute =
Units of Light Measurement
• Visible light travels 186,000 miles per
second
– Light hour =
Units of Light Measurement
• Visible light travels 186,000 miles per
second
– Light day =
Units of Light Measurement
• Visible light travels 186,000 miles per
second
– Light week =
Units of Light Measurement
• Visible light travels 186,000 miles per
second
– Light month =
Units of Light Measurement
• Visible light travels 186,000 miles per
second
– Light year =
AU
• astronomical unit (AU)
• used only in our solar system
• average distance between the Earth and the Sun
– approximately 150 million km (93 million miles)
• Earth is 1 AU from the Sun
• Mercury is 1/3 of an AU from the Sun
• Pluto averages about 40 AU from the Sun
parsec
• used for distances to other parts of the Milky Way
Galaxy (or even further)
• equal to 3.3 light-years
• Crab supernova remnant- 4,000 light-years away
• Milky Way Galaxy- 150,000 light-years across
• Andromeda Galaxy- 2.3 million light-years away
SIZES AND DISTANCES IN THE SOLAR SYSTEM
Sizes
Diameters of Solar System Members :
Sun =
1,392,000 km
Mercury =
Venus =
Earth =
Mars =
Jupiter =
Saturn = 120,536
Uranus =
Neptune =
Pluto =
4,878 km
12,104 km
12,756 km
6,794 km
142,984 km
km
51,118 km
49,530 km
2,304 km
Earth’s Moon =
3,476 km
Mean Distance from Sun
57,900,000 km = 0.387 AU
108,200,000 km = 0.723 AU
149,600,000 km = 1.000 AU
227,900,000 km = 1.524 AU
778,300,000 km = 5.203 AU
1,427,000,000 km = 10.07 AU
2,871,000,000 km = 19.19 AU
4,497,000,000 km = 30.06 AU
5,914,000,000 km = 39.53 AU
Mean Distance from Earth = 384,400 km
Earth and Moon to Scale
Sizes and Distances in the Earth-Moon System
Relative Sizes of Planets in Our Solar System
The Planets of Our Solar System
The Inner Planets
Sizes to Scale
Mercury
Venus
Earth and Moon
Mars
The Planets of Our Solar System
The Outer Planets
Jupiter
Saturn
Earth Included for Scale.
Uranus
Pluto
Neptune
Size Comparisons In Our Solar System
THE SIZE AND DISTANCE SCALE OF THE SOLAR SYSTEM
•
The distances between the members of our Solar System are much larger
than the sizes of the members (even the Sun).
•
The distance from the Earth to the Sun is:
– 150,000,000 km (about 93,000,000 miles) in comparison to the Sun’s diameter
of about 1,392,000 km (about 110 times that of Earth).
•
•
The region beyond the orbit of Neptune, called the Kuiper Belt, contains a
large number of smaller objects (including Pluto and at least one recently
discovered slightly larger object), all (as yet known) smaller than our
Moon.
The Kuiper Belt objects known to date can reach distances of more than
90 times Earth’s distance from the Sun.
SIZES AND DISTANCES IN THE SOLAR SYSTEM
Sizes
Diameters of Solar System Members:
Sun =
1,392,000 km
Mean Distance from Sun
Mercury =
Venus =
Earth =
Mars =
Jupiter =
Saturn =
Uranus =
Neptune =
Pluto =
4,878 km
12,104 km
12,756 km
6,794 km
142,984 km
120,536 km
51,118 km
49,530 km
2,304 km
57,900,000 km = 0.387 AU
108,200,000 km = 0.723 AU
149,600,000 km = 1.000 AU
227,900,000 km = 1.524 AU
778,300,000 km = 5.203 AU
1,427,000,000 km = 10.07 AU
2,871,000,000 km = 19.19 AU
4,497,000,000 km = 30.06 AU
5,914,000,000 km = 39.53 AU
Earth’s Moon =
3,476 km
Mean Distance from Earth = 384,400 km
Orbits of the Inner Planets
Orbits of Jupiter and Saturn
Orbits of the Outer Planets
The Kuiper Belt
• The Kuiper Belt is a zone beyond the outermost major planet,
Neptune, in which many of the comets that pass through the
inner part of the solar system travel, and may have originated in
the early years of our solar system.
• Surveys of the outer part of the solar system, beyond the orbit of
Pluto, have recently found several additional objects comparable
to Pluto in size.
• Most recently, an object apparently larger than Pluto has been
found, which would (if verified) make it the 10th planet of our
solar system.
• The detection of this (as yet un-named) object, called
(temporarily) UB313, was made using the ground-based 48-inch
Samuel Oschin telescope at Palomar Observatory.
• The object is 97 times Earth’s distance from the Sun, or more
than twice Pluto’s greatest distance.
• It is likely that, with continuing very deep sky surveys with both
ground-based and space-based telescopes, that more objects of
these types will be discovered.
Orbit of the newly discovered object, 2003 UB313, compared to those of Pluto and
the giant outer planets. Note, the orbits of Pluto and UB313, in red, are tilted relative
to the plane of the inner giant planet orbits.
The Size and Distance Scale of The Solar System
• The size of our Solar System, if defined by the diameter of
Pluto’s orbit, is about 40 times the diameter of Earth’s orbit
around the Sun.
• If we consider also the most distant Kuiper Belt objects
discovered to date, up to 90 times Earth’s distance from the
Sun, the diameter of our solar system would be increased
accordingly.
• However, the distance to the nearest star other than our Sun
is vastly larger than the size of our Solar System.
• The distances to stars can be estimated by comparing their
observed brightnesses with that of our Sun, if they are known
to be similar to our Sun in other respects (as determined, for
example, by spectroscopic measurements).
o The nearest stars to our solar system, the star system Alpha
Centauri, is at a distance about 9000 times Neptune’s distance,
or 6800 times Pluto’s maximum distance, from our Sun!
o If our solar system were scaled to the size of a quarter (with
Pluto’s orbit about 1 inch in diameter) the Alpha Centauri system
would be at a distance of about 285 feet!