CHAPTER 2: OTHER CELESTIAL

BODIES

COMETS• Are bodies of small mass that revolve around

the sun, usually in highly elliptical orbits and consisting of the dirty snowball model of small solid particles embedded in frozen gases.

• 1682, Astronomer Edmund Halley• Studied the written accounts of 24 comets.• Comets could be regular visitor• Nucleus or core of a comet resembles a large

dirty snowball• Consists of 25% dust and chunks of rocky

and metallic . Materials and 75% ice (methane, ammonia and carbon dioxide)

• 650 comets that have been scientifically recorded.

• The largest has nucleus measuring 42 miles in diameter and the smallest is 0.3 mile.

• When a comet passes close to the sun, it loses some of its matter, usually about 0.3% of its mass per orbit.

• The nucleus of a comet is slightly less denser than water and is covered by a thin crust of dust.

• As a comet comes near the sun, its ice begins to sublimate, to pass directly from solid to gas.

• Coma – the head of a comet consisting of a cloud of gas and dust and usually containing a nucleus.

Comets can be divided into two groups: • Short-period comets with orbital periods of

less than 200 years.• Long-period comets with periods on the

order of million years.

Comets are as old as the solar system and are the remnants of the building blocks that produced Uranus and Neptune.

ASTEROIDS• is one of the several thousand very small members

of solar system that revolve around the sun, generally in Asteroid Belt.

• Asteroid Belt is the region of interplanetary space between the orbits of Mars and Jupiter in which most asteroids are found.

• Ceres- the largest asteroid discovered- 480 miles diameter

• Hermes 1937• Asteroids spectra can be used to obtain rough

estimates of their mineral properties.

METEORS• Also called "Shooting Stars" or "falling stars"• Irregularly shaped masses of metals or rocks that are speeding around in space.• Meteorite is a piece of a meteor that lands on the surface of the earth.• Meteorites are made of iron, nickel, and other metals that can be also found in the earth.• It was classify into three: Iron Meteorites, Stony Meteorites and Stony Iron.• Meteor crater near Arizona was formed by the impact of an iron-nickel meteorite.

The Stars, Galaxies,

Constellations, and the Universe

NAMES OF STARS• When Ptolemy’s Almagest was passed on the

Arab astronomers, many of the stars ended up with Arabic names.

• Many stars start their names with Al e.g., Alel, Altair, and Alcor.

• Greek Letters is used in cataloguing the Stars in approximate order of brightness.Ex. Brightest Star is called Alpha

• Fairer stars with unusual properties are often known by English latters or Catalogue number. ex. T Tauri or B.D.4⁰ +/-4048

PROPERTIES OF STARS

1. Magnitude– refers to the brightness of the stars.

2. Color and Temperature– Color is a result of the temperature. Red Stars

are less hot than yellow stars. The hottest types are the blue-white stars.

3. Composition– Spectroscope is used to study the

composition of stars.– Composition, surface temperature and

luminosity change when they get older.– Typical Star 92.5% hydrogen atoms and 7%

helium atoms

4. Proper Motion– There is very little movement among stars.– 1 second or more arc per year– other shows second of arc per year 100 years

5. Radial Velocity– From the spectral lines coming from starlight, radial

velocity can be taken.– Some spectral lines shift toward the red or to the blue of

the spectrum.6. Size

– Speckle photography- the technique that obtains an image on the surface of a big star.

– If the star is small, its luminosity and temperature may be used to determine its size.

– Stefan Boltzmann Law: The hotter the star, the more it radiates per unit area.

7. Stellar Distance– The distance in parsec is equal to one

divided by the parallax angle.– Parallax - is the apparent shift of an object

when viewed from two different places.– a star with a parallax of 0.4 second of arc is

0.4 or 2.5 parsecs away. – Light year - another unit to indicate the

stellar which represesents the distance light travels in a year’s time.

– One parsec is equal to 3.26 light years.

STAR GROUPINGS1. Open Star Clusters

- close-knit, irregularly shaped groupings of stars.- Contain 100 to 1,000 and 2 to 20 parsec in diameter.

• Parsec (pc) - A unit of measure for interstellar space.• Interstellar - means existing or occurring between

stars.

2. Associations- cousins of open clusters.- few stars but larger in size and looser structure.- 10 to hundred members and about 10 to 100 pc.

3. Globular Star Clusters- Massive, tightly packed, symmetrical and very old.- Contain 20,000 to several million stars. 5 to 25 pc.

THE MILKY WAY • Galaxy is a mass if innumerable stars

planted together in clusters.• It is a big assembly of stars, gas and

dust that is held together by gravity.• Our galaxy contains a range of star

types of different composition, age, distribution and orbital geometry.

A. Population I- Stars of solar composition which have relatively young ages and are distributed in nearly circular orbits in the galactic disk. (e.g. Sun)

B. Population II- Stars that are nearly pure hydrogen and heliun with no heavy elements. (E.g. globular clusters)

CONSTELLATIONS• Patterns and designs imposed by our mind• Named after ancient gods, heroes, animals

or mythological beings• Names of the oldest constellations

originated about 300 B.C.• In the tigris-euphrates valley of

mesopotamia• Constellations names used today was

handed down from greeks and romans

THE ZODIAC CONSTELLATIONSConstellations

Mesopotamian-euphratean

IdentityAries, the Ram Ram, messengerTaurus, the Bull Bull, in frontGemini, the Twins Great twinsCancer, the Crab Workman of the River BalLeo, the Lion LeoVirgo, the Virgin Proclaimer of the rainLibra, the Balance Life maker of heavenScorpius, the Scorpion Scorpion of heavenSaguittarius, the Archer Star of the bowCapricornus, the Goat Goat fishAquarius, the Water Bearer UrnPisces, the Fish Cord- place joining the fish

HABITABLE PLANETS1. The central star should not be more than 1.5

M. so that it will last long enough for substantiated life to evolve at least 2 billion years and will not kill evolving life with too much UV radiation which breaks down organic molecules.

2. The central star should be at least 0.3 M. to be warm enough to create a large orbital zone in which a planet could retain liquid water.

3. The central star should not flare violently or emit strong X-rays. It should be on the main sequence in order to be stable, long enough to give its planet long term climatic stability.

4. The planet must orbit at the right distance from the stars so that liquid water will neither evaporate nor permanently freeze.

5. The planet's orbit must be circular and stable enough to keep it at a proper distance and prevent drastic seasonal changes.

6. The planet’s gravity must be strong enough to hold a substantial atmosphere.

HAS LIFE EVOLVED ELSEWHERE?

• If habitable planets exist and if life evolves readily under habitable conditions, shall we immediately conclude that life must be abundant throughout the universe?

• Has life narrowly escaped complete extinction by climatic change in the past?

• Or was there never any question that natural selection would allow a few species to survive each step of the earth’s evolution?

THE INSTRUMENT

S USED TO STUDY

ASTRONOMICAL BODIES

STELLAR SPECTROSCOPE

• A device that is used to measure the properties of light• An instrument for forming and examine spectra especially in the visible region of electromagnetic spectrum.

CHRONOGRAPH An excellent means of recording

astronomical observations accurately and permanently.

A revolving drum covered with a sheet of paper causes a pen to trace a continuous line on the sheet.

The main observatory clock is connected with this device, and an electric contact marks off each second.

SPECTOGRAPHA spectrograph is an instrument used to separate and measure the wavelengths present in Electromagnetic radiation and to measure the relative amounts of radiation at each wavelength. In other words obtain and record the spectral content of light or its 'spectrum'.

REFRACTING TELESCOPE

A refractor telescope is a type of optical telescope which is also referred to as a refracting telescope. Its curved primary (or largest) lens gathers light, bends it, and sends it back to a focal point where it is further modified by the use of another set of lenses called the eyepiece.

PYRANOMETER

A pyranometer is a type of actinometer used to measure broadband solar irradiance on a planar surface and is a sensor that is designed to measure the solar radiation flux density (W/m2) from a field of view of 180 degrees.

SPECTROHELIOGRAPH

The spectroheliograph is an instrument used in astronomy which captures a photographic image of the Sun at a single wavelength of light, a monochromatic image. The wavelength is usually chosen to coincide with an spectral wavelength of one of the chemical elements present in the Sun.

PYREHELIOMETERA pyreheliometer is an instrument for measurement of direct beam solar irradiance. Sunlight enters the instrument through a window and is directed onto a thermopile which converts heat to an electrical signal that can be recorded.

CHAPTER 2: “Summary”OTHER CELESTIAL

BODIES

1. Comets2. Asteroids3. Meteors4. Nebula5. Stars

Properties of Stars1. Magnitude2. Color and Temperature3. Composition4. Proper Motion5. Radial Velocity6. Size7. Stellar Distance

Star Groupings1. Open Star Clusters2. Associations3. Globular star Cluster

6. The Milky Way galaxy Two Major Group of Galaxy

1. Population I2. Population II

7. Constellations

8. Instruments used to study astronomical bodies

1. Stellar Spectroscope 2. Chronograph 3. Spectograph 4. Refracting Telescope 5. Pyranometer 6. Spectroheliograph 7. Pyreheliometer

1. M – Mang2. V – Victor3. E – Espinosa4. M – Mag5. J – Jogging6. S – Sa7. U – Umaga8. N – Ng9. P – Pumayat

ka!

“ 9 Planets Song ”1. M – Mercury2. V – Venus3. E – Earth4. M – Mars5. J – Jupiter6. S – Saturn7. U – Uranus8. N – Neptune9. P – Pluto

Thank You!!!