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SPEAKING OF ASTRONOMY

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Title: SPEAKING OF ASTRONOMY


1
SPEAKING OF ASTRONOMY
  • Words and terms used.
  • In scientific and technical discussions it is
    important that everyone use the words and terms
    that are generally defined and accepted by others.

2
UNIVERSE
  • The universe is everything, all matter and energy
    that is in existence.

3
ASTRONOMY
  • Astronomy is the scientific study of space,
    including the planets, stars, galaxies, comets,
    and nebulae.

4
CELESTIAL SPHERE The celestial sphere is an
imaginary sphere whose center is the Earth. This
sphere is used by astronomers to map celestial
objects.
5
CONSTELLATION
  • Any one of the 88 areas into which the sky - or
    the celestial sphere - is divided.

6
ASTERISM
  • A pattern of stars seen in Earth's sky which is
    not an official constellation.

7
DECLINATION
  • Declination is a celestial coordinate that is
    used to measure the degrees of latitude above or
    below the celestial equator on the celestial
    sphere.

8
RIGHT ASCENSION
  • Right ascension is a celestial coordinate that is
    used to measure the degrees of longitude on the
    on the celestial sphere. Zero degrees of right
    ascension is the position of the Sun during the
    vernal (spring) equinox (March 21).

9
ZENITH
  • An observer's zenith is the point directly
    overhead.

10
ALTITUDE
  • Altitude is a measurement in mapping astronomical
    objects on the celestial sphere (the sky as
    visible from Earth). Altitude is the angle of the
    object from the observer's horizon. If an object
    is on the horizon, its altitude is 0 degrees. If
    it is at the observer's zenith, its altitude is
    90 degrees. To find an object in the sky, two
    coordinates are needed, its azimuth and its
    altitude.

11
AZIMUTH
  • Azimuth is a measurement in mapping astronomical
    objects on the celestial sphere (the sky as
    visible from Earth). Azimuth is the angle of the
    object from the observer's north point (projected
    onto the horizon). If an object is due north, its
    azimuth is 0 degrees. If it is due east, its
    azimuth is 90 degrees, etc. To find an object in
    the sky, two coordinates are needed, its altitude
    and its azimuth.

12
ORBIT
  • An orbit is a closed path that an object takes as
    it revolves around another body. Orbits are
    generally elliptical, but may be perturbed by the
    presence of yet other bodies and may even form
    unusual figures.

13
APHELION
  • For an object (a planet or comet) orbiting the
    Sun, the aphelion is the point in its orbit which
    is farthest from the sun.

14
PERIHELION
  • The perihelion is a planet or comet's closest
    approach to the Sun. The Earth is at perihelion
    (the Earth is closest to the Sun) in January.

15
APOGEE
  • For an object orbiting the Earth, the apogee is
    the point in its orbit which is farthest from the
    Earth.

16
PERIGEE
  • For an object orbiting the Earth, the perigee is
    the point in each orbit which is closest to the
    Earth. The perigee varies a small amount from
    orbit to orbit. The closest perigee is called the
    proxigee.

17
ECLIPTIC
  • The ecliptic is the plane defined by the Earth's
    orbit around the Sun conversely, in the course
    of a year, the sun traces a path in the sky along
    the ecliptic. Most of the planets in our solar
    system appear close to the ecliptic plane from
    Earth. The Earth's axis is tilted at a 23.5 from
    the ecliptic (which causes the seasons).

18
UMBRA PENUMBRA
  • The penumbra is the area of partial shadow
  • The umbra is the area of total shadow

19
CONJUNCTION
  • The apparent close approach of a planet to the
    Sun (or another planet), from the point of view
    of an observer on the Earth.

20
CONJUNCTION
  • A planet is in conjunction when the Sun is
    exactly between that planet and the Earth or, for
    Mercury and Venus (the two inferior planets),
    when that planet, the Sun, and the Earth are
    lined up. Mercury and Venus have two positions of
    conjunction when either planet is directly
    between the earth and the Sun, it is in inferior
    conjunction when either planet is on the far
    side of the Sun from the earth, it is in superior
    conjunction. During conjunction, a planet cannot
    be seen from Earth (unless it is in transit) it
    is either behind the Sun or is lost in the glare
    of the Sun.

21
OCCULTATION
  • When a smaller astronomical body passes behind a
    larger astronomical body (wholly obscuring its
    view). One example of occultation is when a
    planet passes behind the Sun (from our
    perspective) and it is hidden from our view.

22
TRANSIT
  • When a smaller body passes in front of a larger
    one (for example, when an object passes between
    the Sun and the Earth). During this time, the
    object seems to be crossing the disk of the Sun.
    The only planets that ever pass between the Earth
    and the Sun are Mercury and Venus (since they are
    closer to the Sun than the Earth). Therefore, the
    only planets that can produce a transit are
    Mercury and Venus.

23
ECLIPSE
  • An eclipse happens when the moon blocks the Sun
    or the Earth's shadow falls on the moon.

24
GALAXY
  • A galaxy is a huge group of stars and other
    celestial bodies bound together by gravitational
    forces. There are spiral, elliptical, and
    irregularly shaped galaxies. Our Sun and solar
    system are a small part of the Milky Way Galaxy.

25
SOLAR SYSTEM
  • A solar system is a group of planets, moons,
    asteroids, and comets that orbit around a sun. In
    our solar system, nine planets, over 61 moons,
    and many other objects orbit around our Sun.

26
SUN
  • The Sun is a star at the center of our solar
    system. Our Sun is a medium-sized yellow star
    that is 93,026,724 miles (149,680,000 km) from
    Earth. Its diameter is 865,121 miles (1,391,980
    km). At its core, nuclear reactions produce
    enormous amounts of energy, through the process
    of converting hydrogen atoms into helium atoms
    (nuclear fusion). Its absolute magnitude is
    4.83. The solar mass is 1.99 x 1030 kg.

27
ELLIPSE
  • An ellipse looks like a flattened circle. It
    consists of all the points in a plane that
    satisfy the following ab(twice the length of
    the semi-major axis), where a is the distance
    from one focus to the point on the ellipse, and b
    is the distance from the other focus to the same
    point on the ellipse.

28
ELLIPTICAL ORBIT
  • An elliptical orbit is an orbit that traces out
    an ellipse as the orbiter rotates around another
    body (which is located at one focus of the
    ellipse).

29
EARTH SUN RELATIONSHIP
30
METEOROID
  • Tiny stones or pieces of metal that travel
    through space.

31
METEOR
  • A meteor is a meteoroid that has entered the
    Earth's atmosphere, usually making a fiery trail
    as it falls. It is sometimes called a shooting
    star. Most burn up before hitting the Earth.

32
METEORITE
  • A meteor that has fallen to Earth. Meteorites are
    either stone, iron, or stony-iron.

33
ASTEROID
  • An asteroid is a large rocky object or very small
    planet (planetoid). Most asteroids orbit the Sun
    in the asteroid belt between Mars and Jupiter. A
    few asteroids approach the Sun more closely. An
    asteroid impact with the Earth may have caused
    the extinction of the dinosaurs. The largest
    asteroid and first one ever discovered (by
    Giuseppe Piazzi on January 1, 1801) is Ceres,
    whose mass is equal to over one-third of the 2.3
    x 1021 kg estimated total mass of all the 3,000
    catalogued asteroids.

34
TELESCOPE
  • A telescope is a device that makes faraway
    objects appear closer and larger, allowing us to
    see distant objects in space. The first
    refracting telescope was invented by Hans
    Lippershey in 1608. Early telescopes used glass
    lenses and/or mirrors to detect visible light.
    Later telescopes gathered electromagnetic
    radiation from the entire spectrum, from radio
    waves to gamma rays.

35
REFRACTING TELESCOPE
  • A refracting telescope uses two lenses which
    magnify what is viewed the large primary lens
    does most of the magnification.

36
REFLECTING TELESCOPE
  • A reflecting (or Newtonian) telescope uses two
    mirrors which magnify what is viewed. The first
    reflecting telescope was first described by James
    Gregory in 1663.

37
CASSEGRAIN TELESCOPE
  • A Cassegrain telescope is a wide-angle reflecting
    telescope with a concave mirror that receives
    light and focuses an image. A second mirror
    reflects the light through a gap in the primary
    mirror, allowing the eyepiece or camera to be
    mounted at the back end of the tube.

38
SCHMIDT-CASSEGRAIN
  • A correcting plate (a lens) was added in 1930 by
    the Estonian astronomer and lens-maker Bernard
    Schmidt (1879-1935), creating the
    Schmidt-Cassegrain telescope which minimized the
    spherical aberration of the Cassegrain telescope.

39
EYEPIECE
  • SOMETHING ELSE TO MAKE US SPEND MONEY.

40
GIBBOUS MOON
  • A gibbous moon is between a full moon and a half
    moon, or between a half moon and a full moon.

41
REVOLUTION
  • Revolution is the movement of one object around
    another. For example, the revolution of the Earth
    around the Sun takes one year.

42
ROTATE
  • When an object rotates, it turns around a central
    point or axis. One planetary day is defined as
    the time it takes the a planet to rotate around
    its axis.

43
SIDEREAL TIME
  • Sidereal time is time measured relative to the
    stars (the period between successive conjunctions
    with any star) instead of relative to the motion
    of the Sun). One sidereal day, equal to 23 hours
    and 56 minutes, is the period during which the
    earth completes one rotation on its axis (this is
    the same as the time it takes to come into
    alignment with a particular star).

44
SIDEREAL YEAR
  • A sidereal year is measured relative to the stars
    (the period between successive conjunctions with
    any star). One sidereal year, equal to 365 days,
    6 hours, 9 minutes, and 9.5 seconds, is the
    period during which the earth completes one
    revolution around the Sun

45
HOW MANY DAY IN A YEAR?
  • THE EARTH ROTATES ON ITS AXIS 366 TIMES IN ONE
    REVOLUTION AROUND THE SUN.

46
SPEED OF LIGHT
  • The speed of light is the speed at which
    electromagnetic waves can move in a vacuum
    299,792,458 meters/sec (186,000 miles/second).
    According to Einstein's Theory of Relativity,
    nothing can go faster than the speed of light.

47
LIGHT YEAR
  • A light-year is the distance that light can
    travel in one year in a vacuum, which is about
    5,880,000,000,000 miles or 63,240 AU or 9.46053 x
    1012 kilometers.

48
MESSIER OBJECTS
  • During the late 18th century (1759-1781), the
    French astronomer Charles Messier made a list of
    103 fuzzy objects in space in order not to
    mistake star clusters, galaxies, and nebulae for
    comets (for which he was searching).

49
NGC
  • The NGC (New General Catalog) is a list of over
    13,000 deep-sky celestial objects. It was
    developed in 1888. For example, the Great Nebula
    in Orion is NCG 1976 (and M42). NGC4414 is a
    spiral galaxy 60 million light-years away.

50
TERMINATOR
  • The terminator is the day-night line on a planet
    (or other body).
  • Its also the end of this presentation
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