A list of astronomical Bodies
Astronomy is the most
ancient science, People of all age are very much aquinted with it, and
it's popularity
Is ever increasing but
to understand the astronomy some particuler knowledge is assentioul
You got to know the
character ,physics mathmethical constant and lot more things because the
knowledge
Of astronomy contain
a huge diversity but dispite it's complexcity, to achieve some basic idea
It will be much easier
to follow a piriodic formula likely
This boxes below
Click any boxes to access more information
Quasars
The most extreme form of active galaxy. The name derives
from QUAsi StellAr Radio Source, and they are also known as Quasi Stellar
Objects or QSOs. It is now known that only about one percent are powerful
radio sources but their visual appearance is almost always star-like. Their
spectra contain strong emission lines which are redshifted enormously so
that the Lyman series of hydrogen, normally far into the ultraviolet, appears
at visual wavelengths. The velocities required to produce such redshifts
range up to 90 percent of the speed of light. Although there is still some
controversy over the interpretation of quasar redshifts, most people accept
that they arise from the expansion of the Universe, placing the most distant
quasars at 4,000Mpc to 8,000Mpc (13 to 17 thousand million lightyears)
away. Such distances imply visual luminosities thousands of times greater
than those of normal galaxies, and total energy emission up to a million
times that of a normal galaxy. The luminosity of some quasars varies markedly
on time scales as short as a few days, limiting the size of the emitting
region to about the size of the Solar System. Occasionally the quasar appears
surrounded by a very faint 'fuzz' which careful observation shows to be
a galaxy. High velocity jets are also to be found associated with some
quasars. The most widely accepted model for a quasar has a massive (~ 109
solar mass) black hole surrounded by an accretion disc at its centre. Material
from the accretion disc spirals into the black hole releasing up to 40
percent of its rest mass energy in the process. This is the energy which
powers the quasar. Jets, when visible, seem to be emitted along the rotational
axis of the black hole. Seyfert galaxies are thought to be a less extreme
form of the same phenomeno
Radial velocity
The component of the velocity of a celestial object
along the line of sight from the Earth. It is positive when the object
is moving away from the Earth, and negative when it is moving towards us.
The term is also sometimes used for the velocity of material towards or
away from some other object, such as the surface layers of an oscillating
star like a Cepheid or the expanding nebula around a nova or supernova.
Radiant
The point in the sky from which meteors in a meteor shower
appear to diverge. It is the direction in space of the relative velocity
of the meteors with respect to the Earth. The meteors are on parallel tracks
and appear to diverge from the radiant because of perspective. The meteor
shower is usually named for the constellation which contains the radiant,
e.g. the Geminid meteor shower (Gemini).
Radiation
pressure
The pressure exerted by light or other forms of electromagnetic
radiation. At the distance ofthe Earth, the solar radiation exerts a force
of about lO-SN (the weight of about 2O grains of sugar) onto a surface
one metre square perpendicular to the Sun. This small force is sufficient
to overcome gravity for very tiny particles, leading to the ionic tail
of comets and contributing to the formation of their dust tails.Inside
large stars the temperature is so high that radiation pressure can become
comparable with the gas pressure. This renders the star unstable, and limits
the maximum mass possible for a star to about lOO times the mass of the
Sun.
Proper motion
The movement of a celestial object across the sky due to
its actual motion through space.For stars proper motions range downwards
from a maximum of a few seconds of arc per year.
Proton
One of the constituents of atomic nuclei (see also nucleon
and neutron). It is a sub-atomic particle with unit positive electric charge
and a mass of 1.67xlO-27kg (slightly less than that of the neutron and
about 2000 times that of the electron). The nucleus of an atom of a particular
element always has the same number of protons. but may have differing numbers
of neutrons. The variation in the number of neutrons in a nucleus results
in the different isotopes of an element.
Proton-proton
chain
The main series of nucleosynthesis reactions whereby the
Sun and other low mass stars generate their energy. The first step in the
chain requires two protons to collide, stick together and to form a heavy
hydrogen nucleus, emitting a positron and a neutrino at the same time.
This is a very low probability reaction, and its rate of occurrence determines
the lifetimes of stars. The heavy hydrogen nucleus soon captures another
proton to form the He-3 isotope, and finally two He-3 nuclei combine to
give the normal isotope of helium plus two protons. The net effect, as
in the carbon cycle, is for four protons to combine to produce one helium
nucleus, with the excess energy being released to power the star.
Protostar
A star in the process of being born from an interstellar
gas cloud. Usually only observed as a strong infrared source within the
cloud because dust particles hide it at visual wavelengths.
Pulsar
A rapidly pulsating radio source. Pulsars are thought to
be rotating neutron stars, with the radio emission being beamed out along
their magnetic axes. The rotation whirls the beam around like the beam
of light from a lighthouse, and so we see a flash once per rotation. The
periods range from a millisecond to a few seconds and are very highly stable.
A few pulsars may also be observed at visible and shorter wavelengths.Some
pulsars originate as the compressed core of a supernova, but not all supernovae
seem to produce pulsars and not all pulsars are associated with supernova
remnants, so other processes such as the spinup of an existing neutron
star in a close binary system are needed to explain the remainder.
Quadrature
The position of an outer planet when the planet - Earth -
Sun angle is 90 degrees.
Quantum
Appertaining to the behaviour of sub-atomic particles as
described by quantum theory. Also used as an alternative name for the photon.
Sometimes used in the vernacular to denote any marked change in a quantity.
Quantum
efficIency
The ratio between the number of photons picked up by a radiation
detector to the number arriving at that detector. For charge coupled devices
(CCDs) the quantum efficiency can reach 80 percent, for photography it
is one percent or less.
Radio galaxy
A galaxy emitting much more than the normal amount of radio
energy. The optically visible galaxies are often giant ellipticals with
the radio emission coming from pairs of regions on either side and well
outside the visible part of the galaxy. The radio emission can reach a
million times that of a normal galaxy. They are classed as active galaxies
and their peculiarities may be due to super-massive central black holes
as with Seyfert galaxies and quasars.
Radio telescope
A telescope designed for receiving long wave radiation. Many
radio telescopes operate on similar principles to optical telescopes, using
a parabolic mirror to focus the radio waves. The mirrors of such radio
telescopes, however, have to be huge - up to 3O0m in diameter - in order
to gather sufficient energy and to resolve close sources. Greater resolution
and sometimes sensitivity is obtained by using two or more such basic radio
telescopes in an interferometer. By combining the outputs from several
interferometers in the technique of aperture synthesis, the effect of observing
with telescopes tens of kilometres across may be obtained. Even larger
systems can provide the resolution equivalent to a telescope thousands
of kilometres across, though notthe sensitivity of such an instrument,
via Very Long Baseline Interferometry (VLBI).
Rayleigh limit
The measure conventionally used for the angular resolution
of a telescope or other instrument. It is given by ?=1.22 ??/d radians
for a conventional type of telescope where ? is the operating wavelength
and d the diameter of the telescope objective.For optical telescopes this
becomes ? ~ 1/7d seconds of arc when d is measured in metres. The Rayleigh
limit, however, is an arbitrary quantity and experienced double star observers
can often do better than it would suggest. Conversely if the two objects
are of very different brightnesses (like the two components of Sirius),
their separation may need to be several times the Rayleigh limit before
they can actually be resolved.
Recombination
The recapture of an electron by an ionised atom.
Red giants
A cool star of large physical size. Some red giants would
extend out to beyond Jupiter if they were to replace the Sun. The
masses of red giants, however, are no more than a few times that of the
Sun, and so their densities are very low. They are stars in the late stage
of their lives, having consumed the hydrogen in the their cores and evolved
off the main sequence.
Redshift
of the galaxies
The general shift of lines in the spectra of galaxies towards
longer wavelengths.The shift is greater the further away the galaxy is
from us, and it is generally taken to be a Doppler shift due to the motion
of the galaxy. The velocity and distance are related by V = HxD, where
H is the Hubble Constant with a value around 60 ~ 30 kms-1Mpc-l. The redshift,
or rather the underlying velocities, are remnants of the explosive origin
of the Universe in the big bang.
Reflecting
telescope
A telescope which uses a mirror Three as its objective.
Current main designs include the Newtonian and the cassegrain with its
variant the Ritchey-Chretien telescope.
Roche lobe
One of two volumes in the space around a pair of mutually
orbiting bodies, wherein the gravitational field of one of the bodies predominates.
Within the Roche lobe another smaller object will be gravitationally bound
to the body at the centre of the lobe. Outside the lobes, a small particle
may swap between the bodies, or even be lost entirely to the system (see
also Lagrangian points and Trojan points).
r-process
A set of reactions in nucleosynthesis where neutrons are
added to nuclei more rapidly than the nuclei can undergo radioactive decay
The process is thought to occur during supernova explosions and to produce
many of the heavier elements.
R type stars
Stars similar to those of spectral types G and K, but
with an apparent overabundance of carbon.Their spectra therefore contain
intense bands due to carbon-rich molecules such as C2, CH and CN.
Sagittarius A
A complex radio source at the centre of the Milky llVay Galaxy.
At least a part of the energy is though to originate from interactions
in an accretion disc around a black hole with a mass a few million times
that of the Sun.
Saros
A period of about 18 years, after which a sequence
of similar solar or lunar eclipses is repeated.Since the saros is not an
exact number of days, the new set of eclipses occurs about 120D west of
the preceding set.
Saturn's rings
The spectacular aggregation of countless billions of small
rocky and icy particles that surround and orbit Saturn in its equatorial
plane. The outermost ring is about 240,000km across. Spacecraft have revealed
that the main rings are sub-divided into thousands of ringlets. Several
gaps in the rings are detectable from Earth, with the main one between
the outermost and middle rings known as Cassini's division. Despite their
enormous width, the rings are very thin; perhaps less than a kilometre,
although ripples make them seem thicker when they are viewed edge-on.
Scale height
The distance over which a quantity such as density or pressure
in a planetary or stellar atmosphere changes by a factor of2.7 (or byl/2.7
= x 0.37).The factor is actually e; the base of natural logarithms, and
is more accurately given by 2.71828... In the Earth's atmosphere, the pressure
has fallen to about 37% of its surface value by a height of 8OOOm, and
so the scale height in the lower parts of the Earth's atmosphere is about
8km.
Scattering
The interaction of radiation with matter in which the photon's
direction is changed, but its energy (or wavelength or frequency) remains
the same, or is changed by only a very small proportion. The blue light
from the daytime sky is due to sunlight scattered in the Earth's atmosphere.
The colour occurs because the scattering process involved (known here as
Rayleigh scattering) is much more effective at the shorter wavelengths.
Red light from the Sun is thus scattered to a much lesser extent than the
blue light.
ASTRONOMY NOWl NOV 1998
Our solar system consists of an average star we call
the Sun, the planets
Mercury,
Venus,
Earth,
Mars,
Jupiter,
Saturn,
Uranus,
Neptune,
and
Pluto. It includes: the satellites of the planets;
numerous comets,
asteroids,
and meteoroids; and the interplanetary medium. The Sun is the richest source
of electromagnetic energy (mostly in the form of heat and light) in the
solar system. The Sun's nearest known stellar neighbor is a red dwarf star
called Proxima Centauri, at a distance of 4.3 light
years away. The whole solar system, together with the local stars visible
on a clear night, orbits the center of our home galaxy, a spiral disk of
200 billion stars we call the Milky Way. The Milky
Way has two small galaxies orbiting it nearby, which are visible from the
southern hemisphere. They are called the Large Magellanic Cloud and the
Small Magellanic Cloud. The nearest large galaxy is the Andromeda
Galaxy. It is a spiral galaxy like the Milky Way but is 4 times as
massive and is 2 million light years away. Our galaxy, one of billions
of galaxies known, is traveling through intergalactic space.
The planets, most of the satellites of the planets and
the asteroids revolve around the Sun in the same direction, in nearly circular
orbits. When looking down from above the Sun's north pole, the planets
orbit in a counter-clockwise direction. The planets orbit the Sun in or
near the same plane, called the ecliptic.
Pluto is a special case in that its orbit is the most highly inclined (18
degrees) and the most highly elliptical of all the planets. Because of
this, for part of its orbit, Pluto is closer to the Sun than is Neptune.
The axis of rotation for most of the planets is nearly perpendicular to
the ecliptic. The exceptions are Uranus and Pluto,
which are tipped on their sides.
Composition Of The
Solar System
The Sun contains 99.85% of all the matter in the Solar System.
The planets, which condensed out of the same disk of material that formed
the Sun, contain only 0.135% of the mass of the solar system. Jupiter contains
more than twice the matter of all the other planets combined. Satellites
of the planets, comets, asteroids, meteoroids, and the interplanetary medium
constitute the remaining 0.015%. The following table is a list of the mass
distribution within our Solar System.
-
Sun: 99.85%
-
Planets: 0.135%
-
Comets: 0.01% ?
-
Satellites: 0.00005%
-
Minor Planets: 0.0000002% ?
-
Meteoroids: 0.0000001% ?
-
Interplanetary Medium: 0.0000001% ?
Interplanetary Space
Nearly all the solar system by volume appears to be an empty
void. Far from being nothingness, this vacuum of "space" comprises the
interplanetary medium. It includes various forms of energy and at least
two material components: interplanetary dust and interplanetary gas. Interplanetary
dust consists of microscopic solid particles. Interplanetary gas is a tenuous
flow of gas and charged particles, mostly protons and electrons -- plasma
-- which stream from the Sun, called the solar
wind.
The solar wind can be measured by spacecraft, and it has
a large effect on comet tails. It also has a measurable effect on the motion
of spacecraft. The speed of the solar wind is about 400 kilometers (250
miles) per second in the vicinity of Earth's orbit. The point at which
the solar wind meets the interstellar medium, which is the "solar" wind
from other stars, is called the heliopause. It is a boundary theorized
to be roughly circular or teardrop-shaped, marking the edge of the Sun's
influence perhaps 100 AU from the Sun. The space within the boundary of
the heliopause, containing the Sun and solar system, is referred to as
the heliosphere.
The solar magnetic field extends outward into interplanetary
space; it can be measured on Earth and by spacecraft. The solar magnetic
field is the dominating magnetic field throughout the interplanetary regions
of the solar system, except in the immediate environment of planets which
have their own magnetic fields.
The Terrestrial Planets
The terrestrial planets are the four innermost planets in
the solar system,
Mercury,
Venus,
Earth
and Mars. They are called terrestrial because they
have a compact, rocky surface like the Earth's. The planets, Venus, Earth,
and Mars have significant atmospheres while Mercury has almost none. The
following diagram shows the approximate distance of the terrestrial planets
to the Sun.
The Jovian Planets
Jupiter, Saturn,
Uranus,
and Neptune are known as the Jovian (Jupiter-like)
planets, because they are all gigantic compared with Earth, and they have
a gaseous nature like Jupiter's. The Jovian planets are also referred to
as the gas giants, although some or all of them might have small
solid cores.
Our Milkyway Galaxy
Andromeda Galaxy, M31
The Andromeda Galaxy, M31, is located 2.3 million light
years away, making it the nearest major galaxy to our own Milky Way. M31
dominates the small group of galaxies (of which our own Milky Way is a
member), and can be seen with the naked eye as a spindle-shaped "cloud"
the width of the full Moon. Like the Milky Way,
M31 is a giant spiral-shaped disk of stars, with a bulbous central hub
of older stars. M31 has long been known to have a bright and extremely
dense grouping of a few million stars clustered at the very center of its
spherical hub.
(Courtesy Jason Ware)
The Solar System
During the past three decades a myriad of space explorers
have escaped the confines of planet Earth and have set out to discover
our planetary neighbors. This picture shows the Sun and all nine planets
of the solar system as seen by the space explorers. Starting at the top-left
corner is the Sun followed by the planets Mercury,
Venus,
Earth,
Mars,
Jupiter,
Saturn,
Uranus,
Neptune,
and
Pluto.
Sun and Planets
This image shows the Sun and nine planets approximately
to scale. The order of these bodies are: Sun, Mercury,
Venus,
Earth,
Mars,
Jupiter,
Saturn,
Uranus,
Neptune,
and
Pluto. (Copyright Calvin J. Hamilton)
Terrestrial Planets
The terrestrial planets Mercury,
Venus,
Earth
and Mars approximately to scale. The terrestrial
planets are compact, rocky, Earth-like planets.
Jovian Planets
The Jovian planets Jupiter,
Saturn,
Uranus
and Neptune approximately to scale. The Jovian
planets are named because of their gigantic Jupiter-like appearance. (Copyright
Calvin J. Hamilton)
Diagram of Portrait Frames
On February 14, 1990, the cameras of Voyager
1 pointed back toward the Sun and took a series
of pictures of the Sun and the planets, making the first ever "portrait"
of our solar system as seen from the outside. This image is a diagram of
how the frames for the solar system portrait were taken. (Courtesy NASA/JPL)
All Frames from the Family Portrait
The series of pictures of the Sun and the planets taken
on February 14, 1990, for the solar system family portrait as seen from
the outside. In the course of taking this mosaic consisting of a total
of 60 frames, Voyager 1 made several images of
the inner solar system from a distance of approximately 6.4 billion kilometers
(4 billion miles) and about 32° above the ecliptic
plane. Thirty-nine wide angle frames link together six of the planets of
our solar system in this mosaic. Outermost Neptune
is 30 times further from the Sun than Earth. Our
Sun
is seen as the bright object in the center of the circle of frames. The
insets show the planets magnified many times.
(Courtesy NASA/JPL)
Portrait of the Solar System
These six narrow-angle color images were made from the
first ever "portrait" of the solar system taken by Voyager
1, which was more than 6.4 billion kilometers (4 billion miles) from
Earth and about 32° above the ecliptic.
Mercury
is too close to the Sun to be seen. Mars
was not detectable by the Voyager cameras due to scattered sunlight in
the optics, and Pluto was not included in the mosaic
because of its small size and distance from the Sun. These blown-up images,
left to right and top to bottom are Venus,
Earth,
Jupiter,
Saturn,
Uranus,
and Neptune.
(Courtesy NASA/JPL)
Sun and planets
summary
The following table lists statistical information for
the Sun and planets:
|
Distance
(AU) |
Radius
(Earth's) |
Mass
(Earth's) |
Rotation
(Earth's) |
# Moons |
Orbital
Inclination |
Orbital
Eccentricity |
Density
(g/cm3) |
| Sun |
0 |
109 |
332,800 |
25-36* |
9 |
--- |
--- |
1.410 |
| Mercury |
0.39 |
0.38 |
0.05 |
58.8 |
0 |
7 |
0.2056 |
5.43 |
| Venus |
0.72 |
0.95 |
0.89 |
244 |
0 |
3.394 |
0.0068 |
5.25 |
| Earth |
1.0 |
1.00 |
1.00 |
1.00 |
1 |
0.000 |
0.0167 |
5.52 |
| Mars |
1.5 |
0.53 |
0.11 |
1.029 |
2 |
1.850 |
0.0934 |
3.95 |
| Jupiter |
5.2 |
11 |
318 |
0.411 |
16 |
1.308 |
0.0483 |
1.33 |
| Saturn |
9.5 |
9 |
95 |
0.428 |
18 |
2.488 |
0.0560 |
0.69 |
| Uranus |
19.2 |
4 |
15 |
0.748 |
15 |
0.774 |
0.0461 |
1.29 |
| Neptune |
30.1 |
4 |
17 |
0.802 |
8 |
1.774 |
0.0097 |
1.64 |
| Pluto |
39.5 |
0.18 |
0.002 |
0.267 |
1 |
17.15 |
0.2482 |
2.03 |
* The Sun's period of rotation at the surface varies from
approximately 25 days at the equator to 36 days at the poles. Deep down,
below the convective zone, everything
appears to rotate with a period of 27 days.
Travel to the Sun
Copyright © 1997 by Calvin J. Hamilton. All rights
reserved
ref;Astronomy now(jul-nov).
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duke Jabed
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