Embed Size (px)
Citation preview
Altitude
Autumnal Equinox
Azimuth
Celestial Equator
Celestial Sphere
Circumpolar Star
Conjunction
Cross-Staff
Degree
Ecliptic
Equinox
Evening Star
Hand Measurements
Latitude
Latitude of FDHS
Longitude
Meridian
Minute
Morning Star
Nadir
North Celestial Sphere
One Hour of RA
Parallax
Polaris
Precession of the Equinox
Prime Meridian
Right Ascension
Second
Sidereal Day
Solstice
South Celestial Pole
Summer Solstice
Thuban
Vernal Equinox
Winter Solstice
Zenith
Zodiacal Constellations
Important Terms
The Sky
The Milky
Way
Galaxy
and
The
Andromeda
Galaxy
The Sky
The Leo Constellation
The Sky
Borealis & Shooting Star
The Sky
The Leonid Meteor Shower
The Sky
Naked Eye Planets
The Sky
The Comet McNaught 2007
The Sky
Discharge from Experimental Rocket
The Sky
Zodiacal Light
The Sky
Gegenschein
A Word about Numbers
This box a 10x10 array of dots
Which is 100 dots
A Word about Numbers
This box a 10x10
array of the boxes
from the previous
page.
Which is 10,000
dots
A Word about Numbers
This box a 10x10
array of the boxes
from the previous
page.
Which is 1,000,000
dots
A Word about Numbers
A Word about Numbers1 million seconds is 11.5 days
A Word about Numbers1 billion seconds is 31 years, 8 months
2024
2022
2019
2020
2021
2023
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
A Word about Numbers
1 trillion seconds is 31,688 years
AstrologyThe word ASTROLOGY is derived from two Greek
words:
•astron meaning "star"
•ogia meaning "study of”
•Literally means the “study of stars”
Astrology• Astrology is a symbolic language, an art form, a
science, and a method of divination.
• Though most cultural astrology systems share
common roots in ancient philosophies that
influenced each other, many use methods that differ
from those in the West.
Horoscope
A horoscope is an
astrological chart
or diagram
representing the
positions of the
Sun, Moon,
planets,
astrological
aspects and
sensitive angles
at the time of an
event, such as the
moment of a
person's birth.
Astronomy
The word ASTRONOMY is derived from two Greek
words:
•Astron meaning “star“
•-nomy from nomos, “law“
•literally means “law of the stars”
Astronomy
The Traditional Definition:Astronomy is a natural science that deals with the
study of celestial objects and phenomena that
originate outside the Earth's atmosphere.
Astronomy
It is concerned with the evolution, physics, chemistry,
meteorology, and motion of celestial objects, as well
as the formation and development of the universe.
Astronomy
Astronomers
consistently use
the scientific
method,
naturalistic
presuppositions
and abstract
mathematical
reasoning to
investigate or
explain
phenomena in the
universe.
Astrology vs. Astronomy
The Celestial Sphere
• It is useful in discussing objects in the
sky to imagine them to be attached to a
sphere surrounding the earth.
• This fictitious construction is called the
celestial sphere.
• At any one time we see no more than half
of this sphere, but we will refer loosely to
the imaginary half-sphere over our heads
as the celestial sphere.
The Celestial Sphere
• It is useful in discussing objects in the
sky to imagine them to be attached to a
sphere surrounding the earth.
• This fictitious construction is called the
celestial sphere.
• At any one time we see no more than half
of this sphere, but we will refer loosely to
the imaginary half-sphere over our heads
as the celestial sphere.
The Celestial Sphere
Place all of the
stars, planets, the
Moon, and the
Sun on a
transparent globe,
with the Earth at
the center.
The Celestial Sphere
•The Earth’s North
Pole is under the
North Celestial
Pole.
•The Earth’s South
Pole is under the
South Celestial
Pole.
•The Earth’s
equator is under
the Celestial
equator.
Earth rotates west to
east, so stars appear to
circle from east to
west.
The Celestial Sphere
The Celestial Sphere
Zenith = Point on the celestial sphere directly overhead
Nadir = Point on the celestial sphere directly underneath
(not visible!)
The Celestial Sphere
Meridian is an imaginary circle on the celestial sphere.
It passes from the north celestial pole to the southern
celestial pole, passing through the zenith
The Celestial Sphere
Fort Dorchester:
Longitude = 80 06 W
Latitude = 32 55 N
• Latitude: position north or south of equator
• Longitude: position east or west of Prime
Meridian (runs through Greenwich, England)
The Celestial Sphere
The Celestial South Pole is not visible from the
northern hemisphere.
Horizon
North
Celestial
North Pole
32° 55’
South
57° 5’
Celestial
Equator
Horizon
Charleston: l ≈ 32.9º or 32º 55’
The Celestial Sphere
The Celestial Sphere
Apparent Motion of The Celestial
Sphere
The Celestial Sphere
The Celestial Sphere
The Celestial Sphere
A circumpolar
star is a star that
never sets.
It never
disappears below
the horizon, due to
its proximity to one
of the celestial
poles.
The Celestial Sphere
The Sun’s gravity is doing the same to Earth.
At left, gravity is pulling on a slanted top. => Wobbling
around the vertical.
Precession of the Equinox
Precession of the Equinox
Although the axis seems
fixed on human time
scales, it actually
precesses over about
26,000 years.
Polaris won’t always be
the North Star.
Positions of equinoxes
shift around orbit; e.g.,
spring equinox, once in
Aries, is now in Pisces!
It will be closest to
Polaris ~ A.D.
2100.
In 3000 B.C. the
faint star Thuban in
the constellation
Draco was the
North Star.
Errai
Precession of the Equinox
Alderamin
Precession of the Equinox
The North Celestial Pole currently has
nearly the same coordinates as the bright
star Polaris (named from the Latin stella
polaris, meaning "pole star").
The Ecliptic
• The Sun’s apparent path on the sky is called the
Ecliptic.
• The planets share this path across the sky, ±6°
The Ecliptic
Due to Earth’s revolution around the sun, the Sun
appears to move through the zodiacal
constellations.
The EclipticIn ASTROLOGY
• The zodiac is a circle of twelve 30° divisions of
celestial longitude that are centered upon the ecliptic.
• These twelve divisions are called signs.
• Twelve constellations occupy these divisions.
The EclipticSign Constellation
Name English Tropical zodiac NameIAU constellation
boundaries
Solar stay
(days)
Aries The Ram 20 March – 20 April Aries 18 April – 13 May 25.5
Taurus The Bull 20 April – 21 May Taurus 13 May – 21 June 38.2
Gemini The Twins 21 May – 21 June Gemini 21 June – 20 July 29.3
Cancer The Crab 21 June – 22 July Cancer 20 July – 10 August 21.1
Leo The Lion 22 July – 23 August Leo10 August –
16 September36.9
Virgo The Virgin23 August –
23 SeptemberVirgo
16 September –
30 October44.5
Libra The Scales23 September –
23 OctoberLibra
30 October –
23 November21.1
Scorpio The Scorpion23 October –
22 NovemberScorpius
23 November –
29 November8.4
Serpentarius The Snake Handler Ophiuchus29 November –
17 December18.4
SagittariusCentaur The
Archer
22 November –
22 DecemberSagittarius
17 December –
20 January33.6
Capricorn The Sea Goat22 December –
20 JanuaryCapricornus
21 January –
16 February27.4
AquariusThe Water
Bearer20 January – 18 February Aquarius
16 February –
11 March23.9
Pisces The Fish 18 February – 20 March Pisces 11 March – 18 April 37.7
The Ecliptic
The Ecliptic
The planets are orbiting the sun almost
exactly in the plane of the Ecliptic.
The Moon is orbiting Earth in almost the
same plane (Ecliptic).
The Ecliptic
The planets are orbiting the sun almost
exactly in the plane of the Ecliptic.
The Ecliptic
The planets orbit the Sun almost exactly in
the plane of the Ecliptic.
28 January 2016
The Ecliptic
The planets orbit the Sun almost exactly in
the plane of the Ecliptic.
29 November 1989
The Ecliptic
The Ecliptic
April 23, 2002
The Ecliptic
Fort Dorchester:
Longitude = 80 06 W
Latitude = 32 55 N
• Latitude: position north or south of equator
• Longitude: position east or west of prime
meridian (runs through Greenwich, England)
Right Ascension
If you face the north celestial pole,
the stars will rise (ascend) on your
right - hence the term "right
ascension."
Right Ascension
West East
• Right ascension
(RA) is like
longitude.
• It locates where a
star is along the
celestial equator.
• The zero point of
longitude has been
chosen to be where
the line straight
down from the
Greenwich
Observatory in
England meets the
equator.
Right Ascension
• RA is measured in hours (h), minutes
(m) and seconds (s).
• One hour of RA (1h) is 15°.
• Since 24 x 15°=360°.
• There are 24 hours of Right Ascension
around the celestial equator.
• The celestial sphere makes one full
rotation (24h of RA) in one day (24
hours of time).
Right Ascension
Right Ascension
• The constellation Orion has a RA of 05h 35m 42s
• This is where (not when) the center of the constellation
appears on the Celestial Sphere.
Right Ascension
• When will the constellation Orion be directly overhead?
• You must consult a Star Chart for that (we will be using
them in a few chapters).
Right Ascension
Measurements in the Sky
In a full circle there are 360 degrees.
Each degree is split up into 60 parts, each part being 1/60
of a degree. These parts are called minutes.
Each minute is split up into 60 parts, each part being 1/60
of a minute. These parts are called seconds.
Symbol for degree: °
Symbol for minute: ‘
Symbol for second: “
Measurements in the Sky
60
Measurements in the Sky
So, the angle of 40 degrees, 20
minutes, 50 seconds is usually
written this way:
40° 20’ 50”
Or it can be written in decimal
form:
40.34722°
Measurements in the Sky
The Sun “travels” across the sky at 15 degrees per
hour.
Measurements in the Sky
• Astronomers use angles
to measure the relative
position of objects in the
sky.
• The angle between two
stars doesn't change and
doesn't depend on the
distance of the stars from
the Earth.
In ancient and
medieval times,
a cross-staff was
used to measure
angles in the
sky.
In the absence
of a cross-staff,
you can estimate
angles using
your fingers and
hand.
Measurements in the Sky
Measurements in the Sky
• To get started, hold your
hands at arm's length in
front of your face.
• Now raise your little finger.
The width of the tip of your
little finger at arm's length
is about one degree
• Raise your three middle
fingers to measure 5
degrees.
Measurements in the Sky
•Clench your fist or hold
your hand like a
policeman stopping traffic
to measure 10 degrees.
•Now stretch your thumb
and little finger as wide
as you can (one full
hand-span) to measure
about 25 degrees.
25o
Azimuth and Altitude
Azimuth - The angular distance measured around
the observer's horizon from the point directly
beneath the Celestial North Pole to place on the
horizon beneath the celestial body.
Azimuth is 0° for an object due north, 90° due
east, 180° due south, and 270° due west.
Azimuth and Altitude
Altitude, also referred to as elevation angle, refers to the vertical angle measured from the astronomical horizon (0°) towards the zenith (+90°).
Parallax is an apparent change in
an object's position due to a
change in the observer's position.
Parallax
The parallax
angles of the
star are so
small, that
you need a
telescope to
observe them.
……
Parallax
Stellar parallax is created by the different orbital
positions of the Earth that causes nearby stars
to appear to move relative to more distant stars.
Rotation – the movement of a
planet around an axis that is
internal to the planet.
e.g. a planet spinning on its
axis (a day).
Rotation
Daily Motion
• Thanks to the
Egyptians (in part),
our day is divided
into 24 hours.
• This day is a solar
day – the time from
the noon of one day
to the following day’s
noon.
Daily Motion• A synodic day is the period it takes for a planet to
rotate once in relation to Sun.
• From noon of one day to noon of the next day.
• Sometimes referred to as a solar day.
Daily Motion• The sidereal day is the time it takes for the Earth to
complete one rotation about its axis with respect to
the ‘fixed’ stars.
• The stars “move” around the Earth in 23 hours 56
minutes.
Daily MotionIf you look closely at the positions of the stars
over a period of several days, you will notice that
according to our clocks, the stars rise and set 4
minutes earlier each day.
The time of each image is 5:49
August 6August 7August 8August 9
6 August 5:49
Daily MotionIf you look closely at the positions of the stars
over a period of several days, you will notice that
according to our clocks, the stars rise and set 4
minutes earlier each day.
7 August 5:458 August 5:419 August 5:37
Daily Motion
Daily Motion
Revolution – the movement of
a planet around an axis that is
external to the planet.
e.g. a planet moving around a
star.
Revolution
Annual Motion
The motion of the Earth in its orbit round the Sun is
called its annual motion.
It takes 365.25 days to complete one revolution around
the Sun.
Annual Motion – Leap Year
• A leap year is a year containing one additional day in order to
keep the calendar year synchronized with the astronomical or
seasonal year.
• Prior to the 1500s, a 10 day drift developed between the
calendar event and actual astronomical time.
Annual Motion – Leap Year
• The Julian calendar was in
general use in Europe and
Northern Africa until 1582.
• Four Catholic countries—Spain,
Portugal, the Poland, and most of
Italy—implemented the new
calendar on the date specified by
Pope Gregory XIII.
Annual Motion – Leap Year
• Julian Calendar Thursday, 4
October 1582, being followed by
Gregorian Calendar Friday, 15
October 1582.
• In the British Empire (including
the American colonies),
Wednesday 2 September 1752
was followed by Thursday 14
September 1752 (170 years
later).
Annual MotionAutumnal Equinox - Sept 23*
• Length of day & night are “equal”
• 12 hours, 6 minutes, 55 seconds
Winter Solstice - Dec 22
• The shortest “day” of the year
• 9 hours, 59 minutes, 29 seconds
Vernal Equinox - March 20*, 2020
• Length of day & night are “equal”
• 12 hours, 8 minutes, 55 seconds
Summer Solstice - June 21, 2020
• The longest “day” of the year (daytime)
• 14 hours, 18 minutes, 46 seconds
*On these two days, the geometric center of the sun is above the
horizon for 12 hours.
• Literally meaning Equal Night.
• Although, as the etymology of the word suggests, the
term originally referred to when night and day are the
same length.
• There are two equinoxes each year.
Autumnal Equinox – September 23, 2019
Vernal Equinox – March 20, 2020
Annual Motion – Equinox
The instant at which the center of the Sun crosses the
celestial equator (the intersection of the ecliptic and
equator).
Annual Motion – Equinox
The Sun rises Due East on the horizon.
Annual Motion – Equinox
The sunlight strikes the Earth perpendicular to the
equator.
Annual Motion – Equinox
• Tropic of Cancer is a parallel of latitude on the Earth,
23.5 degrees North of the Equator.
• The The Tropic of Capricorn is a parallel of latitude
on the Earth, 23.5 degrees South of the Equator.
Annual Motion
• Literally meaning Standing Still of the Sun or Sun
Stopping.
• The summer and winter solstices are the longest and
shortest days of the year, respectively.
Winter Solstice – December 22, 2019
Summer Solstice – June 21, 2020
Annual Motion – Solstice
Occur when Sun
is at its greatest
distance from the
celestial equator.
Annual Motion – Solstice
During the Summer Solstice, the Sun is above the
celestial equator.
Summer Solstice
Summer Solstice
The Sun rises North of East.
Summer SolsticeThe sunlight strikes the Earth perpendicular to the
Tropic of Cancer.
Winter Solstice
During the Winter, the Sun is below the celestial
equator.
Winter SolsticeThe sunlight strikes the Earth perpendicular to the
Tropic of Capricorn.
Winter Solstice
The Sun rises South of East.
Annual Motion
Vernal Equinox – March 20 Summer Solstice – June 21
Autumnal Equinox – Sept 23 Winter Solstice – Dec 22
Annual MotionAutumnal Equinox - Sept 23*
• Length of day & night are “equal”
• 12 hours, 6 minutes, 55 seconds
Winter Solstice - Dec 22
• The shortest “day” of the year
• 9 hours, 59 minutes, 29 seconds
Vernal Equinox - March 20*, 2020
• Length of day & night are “equal”
• 12 hours, 8 minutes, 55 seconds
Summer Solstice - June 21, 2020
• The longest “day” of the year (daytime)
• 14 hours, 18 minutes, 46 seconds
*On these two days, the geometric center of the sun is above the
horizon for 12 hours.
Annual Motion
• ‘Sunrise’ is defined as the instant when the upper edge
of the sun's disk becomes visible above the horizon.
• In the same sense, ‘sunset’ refers to the moment the
upper edge disappears below the horizon.
• At both instances, the center of the sun is below the
horizon, and therefore the equinox day lasts a little
longer than 12 hours.
Annual Motion• Another reason why the Sun is visible longer than 12
hours on an equinox is that the Earth's atmosphere
refracts (bends) sunlight.
• Refraction causes the Sun’s upper edge to be visible
from Earth several minutes before the edge actually
reaches the horizon.
Annual Motion
When will “Equal night” occur in North Charleston?
This Autumn, 12 Hours of daylight will occur on -
September 26
• Length of day & night aren’t exactly equal
• 12 hours, 55 seconds
Next Spring, March 16 will be the closest to 12 hours of
daylight
• Length of day & night are almost equal
• 12 hours, 46 seconds
The Seasons
Earth’s axis of rotation is inclined vs. the normal to its
orbital plane by 23.5°, which causes the seasons.
The Seasons
Northern summer
corresponds to a southern
winter
Northern winter corresponds
to a southern summer
The Seasons are only caused by a varying angle of
incidence of the sun’s rays.
The Seasons
When sunlight shines on the earth at a lower angle (a), the
energy of the sunlight is spread over a larger area, and is
therefore weaker than if the sun is higher overhead (b) and
the energy is concentrated on a smaller area.
The Seasons
When sunlight shines on the earth at a lower angle (a), the
energy of the sunlight is spread over a larger area, and is
therefore weaker than if the sun is higher overhead (b) and
the energy is concentrated on a smaller area.
a
b
The Seasons• Since the Sun is not at the center of an elliptical orbit, the planet
moves closer towards and further away from the Sun as it orbits.
• The place where the planet is closest to the Sun is called
perihelion.
• When the planet is furthest away from the Sun, it is at aphelion.
• In Greek, "helios" mean Sun, "peri" means near, and "apo"
means away from
The Seasons
Earth’s distance from the sun has only a very
minor influence on seasonal temperature
variations.
Sun
Earth in
July
Earth in
January
Earth’s orbit (eccentricity greatly
exaggerated)
147.5 million km
Perihelion152.5 million km
Aphelion
The Motion of the Sun
Magnitude• The brightness of a star can impart a great deal of
information about the star.
• Due to the various distances of the multitudes of stars, the
brightness of a brilliant star can appear faint when
compared to a closer dim star.
Magnitude• In astronomy, magnitude is a logarithmic measure of the
brightness of an object, measured in a specific wavelength
or passband, usually in the visible or near-infrared
spectrum.
• An imprecise but systematic determination of the
magnitude of objects was introduced in ancient times by
Hipparchus.
Magnitude
• Hipparchus ranked
stars in three
magnitude very
general classes
according to their
brightness but he did
not assign a
numerical brightness
value to any star.
• The magnitude
system ranging from
1 (brightest) to 6
(faintest) was
established by
Ptolemy.
Apparent Magnitude
• The apparent
magnitude (m) of a
celestial object is a
number that is a
measure of its
brightness as seen by
an observer on Earth.
• It is adjusted to the
value it would have in
the absence of the
atmosphere.
Apparent Magnitude• The brighter an object appears, the lower its magnitude value
(i.e. inverse relation).
• Furthermore, the magnitude scale is logarithmic; and a
difference of n magnitudes in absolute magnitude
corresponds to a luminosity ratio of 100(n/5).
Magnitude
Difference
Relative
Brightness
0 1
1 2.51
2 6.31
3 15.85
4 39.81
5 100
10 10,000
15 1,000,000
20 100,000,000
Apparent Magnitude• The brighter an object appears, the lower its magnitude value
(i.e. inverse relation).
• Furthermore, the magnitude scale is logarithmic; and a
difference of n magnitudes in absolute magnitude
corresponds to a luminosity ratio of 100(n/5).
Magnitude
Difference
Relative
Brightness
0 1
1 2.51
2 6.31
3 15.85
4 39.81
5 100
10 10,000
15 1,000,000
20 100,000,000
Apparent Magnitude• The Sun, at apparent magnitude of −27, is the brightest
object in the sky.
• The faintest were of sixth magnitude (m = 6), which is the
limit of human visual perception (without the aid of a
telescope).
Apparent Magnitude
Magnitude Object
-26 The Sun
-13 Full Moon
-6 Crescent Moon
-4 Planet Venus
-3 Planet Jupiter & Mars
-2 Planet Mercury
-1 Brightest Star, Sirius
0 Planet Saturn
Apparent Magnitude
Magnitude Object
0 Planet Saturn
+1 Antares
+2 Polaris
+3Faintest naked-eye stars
naked eye: rural, suburban, small city
+4
Faintest naked-eye stars visible from
suburban areas & outer areas of small
cities
+5
Faintest naked-eye stars visible from
"dark" rural areas located some 40 miles
(60 km) from major cities
+6
Planet Uranus
Faintest naked-eye stars visible from
"dark" rural areas located some 100 miles
(150 km) from major cities
Apparent Magnitude
Magnitude Object
-26 The Sun
-13 Full Moon
-6 Crescent Moon
-4 Planet Venus
-3 Planet Jupiter & Mars
-2 Planet Mercury
-1 Brightest Star, Sirius
0 Planet Saturn
Absolute Magnitude• Absolute magnitude is a measure of the luminosity of a
celestial object, on a logarithmic astronomical magnitude
scale.
• An object's absolute magnitude is defined to be equal to the
apparent magnitude that the object would have if were viewed
from a distance of exactly 10 parsecs (32.6 light years), with
no dimming of its light due to absorption by interstellar dust
particles.
Absolute Magnitude• Absolute magnitude is a measure of the luminosity of a
celestial object, on a logarithmic astronomical magnitude
scale.
• However, the absolute magnitude is equal to the apparent
magnitude that the object would have if were viewed from a
distance of exactly 10 parsecs (32.6 light years).
Apparent & Absolute Magnitudes
Apparent & Absolute Magnitudes
Apparent & Absolute Magnitudes
Common
NameConstellation
Apparent
Magnitude
Absolute
Magnitude
Distance from
Earth
Sun n/a -26.72 4.2 93 million miles
Sirius Canis Major -1.46 1.4 8.6 light-years
Rigel Orion 0.12 -8.1 1,400 ly
Betelgeuse Orion 0.50 -7.2 1,400 ly
Aldebaran Taurus 0.85 -0.3 60 ly
Pollux Gemini 1.14 0.7 40 ly
Regulus Leo 1.35 -0.3 69 ly
Castor Gemini 1.57 0.5 49 ly
Apparent & Absolute Magnitudes
Common
NameConstellation
Apparent
Magnitude
Absolute
Magnitude
Distance from
Earth
Sun n/a -26.72 4.2 93 million miles
Sirius Canis Major -1.46 1.4 8.6 light-years
Rigel Orion 0.12 -8.1 1,400 ly
Betelgeuse Orion 0.50 -7.2 1,400 ly
Aldebaran Taurus 0.85 -0.3 60 ly
Pollux Gemini 1.14 0.7 40 ly
Regulus Leo 1.35 -0.3 69 ly
Castor Gemini 1.57 0.5 49 ly
Proper Motion
Luhman 16 is a binary brown-dwarf system in the southern constellation
Vela 6.5 ly away - during 2 year peroid
Proper motion refers to the movement across the sky
exhibited by a star or other celestial body.
Proper MotionThe enormous distances to the stars means that only the
closest have proper motions that are large enough to be
expressed in arcseconds per year – milliarcseconds per year
are more common.
Proper motion of 61 Cygni in one year intervals.
Proper Motion
Barnard's Star
is a very-low-
mass red dwarf
about 6 light-
years away
from Earth in
the
constellation of
Ophiuchus.
This image
covers 9 years
from 2007 to
2015.
This Ends the
Material for
Chapter 1
