milky way:

The Milky Way is the galaxy which is the home of our Solar System together with at least 200 billion other stars (more recent estimates have given numbers around 400 billion) and their planets, and thousands of clusters and nebulae, including at least almost all objects of Messier’s catalog which are not galaxies on their own (one might consider two globular clusters as possible exceptions, as probably they are just being, or have recently been, incorporated or imported into our Galaxy from dwarf galaxies which are currently in close encounters with the Milky Way The milky way is a spiral glaxy.

types of galaxies and what are they made of:

spiral galaxies:

The most common type of galaxy is called a “spiral galaxy.” Not surprisingly, spiral galaxies look like spirals, with long arms winding toward a bright bulge at the center. But be careful – if you looked at a spiral galaxy from the side, you could mistake its shape for a circle, and so you’d have to use other criteria to learn it was a spiral.

About 77% of the observed galaxies in the universe are spiral galaxies. Our own galaxy, the Milky Way, is a typical spiral galaxy. The images below show three other good examples.

Elliptical galaxies:

The giant elliptical, M87

A galaxy that has a superficially smooth, featureless appearance and an ellipsoidal shape. Giant ellipticals, such as M87, may contain over 10 trillion solar masses in the form of stars, are among the largest of galaxies, and are often found at the heart of rich clusters of galaxies. Dwarf ellipticals, on the other hand, such as M32 (a satellite of the Andromeda Galaxy) may have masses as low as 10 million solar masses and lie at the bottom end of the galactic size range. Normal ellipticals are quite rare throughout much of space, but form the majority in big clusters. It used to be thought that ellipticals were the oldest galaxies, but more recent studies, including computer simulations, suggest that they have formed from collisions and mergers between spiral galaxies. So-called starburst galaxies appear to show this process in action.

Irregular galaxies: 

Approximately 3% of galaxies observed cannot be classified as either ellipsoidal or spirals. These galaxies have little symmetry in their structure and are termed irregular galaxies. An example is Sextans A, shown in the image on the right. This irregular galaxy is a member of the Local Group, at a distance of about 10 million light years (Ref). The blue regions are clusters of young stars; the brighter stars are members of our own Milky Way galaxy in the foreground. Other examples of irregular galaxies are the Large Magellanic Cloud (a satellite galaxy of the Milky Way) and the Messier object M82.

Properties of Irregular Galaxies

Irregular galaxies have masses in the range 10⁸ to 10¹⁰ solar masses, diameters from 1 to 10 kpc, and blue magnitudes from -13 to -20. Other than that, they have few systematic features. 

Approximately 3% of galaxies observed cannot be classified as either ellipsoidal or spirals. These galaxies have little symmetry in their structure and are termed irregular galaxies. An example is Sextans A, shown in the image on the right. This irregular galaxy is a member of the Local Group, at a distance of about 10 million light years (Ref). The blue regions are clusters of young stars; the brighter stars are members of our own Milky Way galaxy in the foreground. Other examples of irregular galaxies are the Large Magellanic Cloud (a satellite galaxy of the Milky Way) and the Messier object M82.

Properties of Irregular Galaxies

Irregular galaxies have masses in the range 10⁸ to 10¹⁰ solar masses, diameters from 1 to 10 kpc, and blue magnitudes from -13 to -20. Other than that, they have few systematic features.

We classify stars by their characteristics.

Like our sun, all stars are huge balls of glowing gas

that produce or have

produced energy by fusion.

However, stars differ in size, brightness

and temperature. Some stars

are smaller, fainter, and cooler than the sun.

Others are much bigger, brighter,

and

hotter. Stars look like small points of light because

they are  very far away.

At most, only a few tousand can be seen without

a telescope.

To discribe the distances between stars,

astronomers often use a unit

called light-year.

A

light year is the distance light travels

in one year, wich is about 9.5 trillion kilometers.

Outside the solar system, the star

closest to earth

is

about 4 light -years away.

Stars have life cycle

Although stars last for very long periods,

they are not permanent.

Stars are a fascinating component of our universe. They may seem like

permanent objects in the sky,

but technology has allowed us to photograph the heavens, and now we know more about stars than ever before.

They are born, they live, and then they die. How does this happen?

That’s what this activity is all about! A star’s life is long compared to that of a human,

but we can see the stages of stellar birth, aging, and death in the heavens.

They follow a pattern similar to many of the life cycles we see here on earth. Stars are born, they “grow up,”

exist many years, and then they die, and there’s an exciting battle between the force of gravity

and gas pressure to that makes it exciting and potentially explosive!

Space may seem empty, but actually it is filled with thinly spread gas and dust.

This gas and dust is called interstellar medium. The atoms of gas are mostly hydrogen (H₂),

and the gas atoms are typically about a centimeter apart.

The dust is mostly microscopic grains

and comprises only a few percent of the matter between stars.

The dust is mostly carbon and silicon.

In some places, this interstellar medium is collected into a big cloud of dust and gas known as a nebula.

This is the birthplace of stars because the gas and dust is what makes up a star.

In fact, our sun was probably born in a nebula nearly 5 billion years ago.

]]> http://2009rt6sciromina.wordpress.com/2010/03/16/stars-change-over-their-live-cycles/feed/ 0 2009rt6sciromina http://2009rt6sciromina.wordpress.com/2010/03/16/the-sun-is-our-local-star/ http://2009rt6sciromina.wordpress.com/2010/03/16/the-sun-is-our-local-star/#comments Tue, 16 Mar 2010 16:49:45 +0000 2009rt6sciromina http://2009rt6sciromina.wordpress.com/?p=76 ]]> Dear Maryam

I have a question about The sun is our local star I don’t understand it. Please help me!!!!!!!!!!

Dear Romina

I’m going to help you,

The sun is the only star in our solar system.  The sun is far larger than any of the planets. It contains 99.9 percent of the mass of the etire solar system. The sun contains mostly of hydrogen. E nergy is produced when hydrogen in the sun’s  interior turns into helium. This energy is the source of light and warmth that make life possible on earth. The sun’s interior.

CORE: The center of the sun, called the core, is made of very dense gas. Temperatures reah about 15 million degrees Celsius. Under this extreme conditions, some hydrogen particles collide and combine to form helium in a process called funsion. The process releases energy that travels trough the core by radiation.

RADIATIVE ZONE: Once energy is produced in the core of the Sun, it needs a way to travel from the solar center to the outer regions. The physical transport of energy from its production site to the surrounding regions can be done in a number of ways. However, for a star like the Sun, the most efficient means of transferring energy near the core is by radiation. Consequently, the region surrounding the core of the Sun is known as the radiation zone. Throughout this region of the solar interior, energy, in the form of radiation, is transferred by its interaction with the surrounding atoms. In the radiation zone of the Sun the temperature is a little cooler than the core and as a result some atoms are able to remain intact. These intact atoms are able to absorb energy, store it for awhile, and then later emit that energy as new radiation. In this manner the energy that is generated in the core is passed from atom to atom through the radiation zone.

CONVECTION ZONE: Currents of hot gas in the convection zone carry energy outward.

PHOTOSPHERE: Visible light moves by radiation out into space from the photosphere. It takesn8 minutes for the light to reach earth.

CHROMOSPHERE:  The chromosphere is  the thin middle layer of teh sun’s atmosphere. It gives off pinkish light.

CORONA: The sun’s outermost layer, has avery low density. Sun spots are spots on the  sun’s photosphere that are cooler than surrounding areas. Although they apper dark, sunspots are actually bright.

Solar wind: Material in the sun’s corona is continually streaming out into space. The electrically charged particles that flow out in all directions from the corona are called  the solar wind.

1.What is a meteor: A brief streak of light produced by a small particle entering earth’s atmosphere at a high speed.

2.What is a comet: A body that produces a coma of gas and dust; a small, icy body that orbits the sun.

3.What is an asteroids: A small, solid, rocky body that orbits the sun.

4.Tell me something about pluto: Pluto is the smallest of the nine planets. It is smaller than the moon. Pluto’s  mass is less than 0.3 percent of earth’s mass, so its gravitational pull is weak. Pluto’s moon, charon, has a diameter half that of pluto and a mass about 15 percent  of Pluto’s. Because pluto and charon orbit each other, they are sometimes called a double planet. 

5. Why do scientists know less about pluto than about other planets? Because no spacecraft has passed close to pluto, so scientists do not have clear images of the planet’s surface.

I’m going to tell you what I did in science. Today we started a new chapter, it was about the outer solar system has four giant planets,

Beyond Mars stretches the outer solar system, where the four largest planets slowly orbit the sun. The gas giants Jupiter, Saturn, Uranus, and Neptune are made mainly hydrogen, helium and other gases.

The giant planets are so large and have such large amounts of these gases that they have  a lot of mass.The huge gravitational force from such a large mass is enough to pull the gas particles close together and make the atmosphere very dense. Inside the giant planets, the gases become more dense than water. The outermost parts are less dense and more like earth. The atmosphere of a giant planet is very deep. The atmosphere is thin and very cold. There may be a haze of gases. A little lower is a layer of clouds that reflect sunlight, just like clouds on earth. There are strong winds and other weather patterns. Lower down, it is warmer and there are layers of clouds of different materials. As you go farther, the atmosphere gradually becomes dense enogh to call liquid. It also gets thousands of degrees hotter as you get closer to the center of the planet. The materials around you become more and more dense until they are solid. Scientists think that each of the four gas giants has solid core, larger than earth, deep in its center.

The terrestial planets have rocky crusts , Scientists study about earth  to learn about other planets. They also study other planets to learn more about earth. Terrestial planets are Mercury, Venus, Earth, and Mars the 4 planets closest to the sun. They all have rocky crusts and dense mantles and cores. Their insides, surfaces, and atmostpheres formed in similiar ways and follow similar patterns. One planet earth can be used as a model to understand the others. In fact, the term terrestrial comes from terra, the Latin word for earth.

PROCESSES AND SURFACE FEATURES

All terrestrial planets have layers. Each planet gained energy from the collisions that formed it. This energy heated and melted the planet’s materials. The heaviest materials were metals, wich sank to the center and formed a core. Lighter rock formed a mantle around the core. The lightest rock rosse to the surface and cooled into a crust. Four types of process then shaped each planet’s rocky crust. The processes acted to different extents on each planet, depending on how much the crust and inside of the planet cooled. Tectonics is the processes  of change in a crust due to the motion of hot material underneath. As a planet cools, the crust gets stiffer and the mantle may stop moving, so this process stops. Volcanism a second process, called volcanism, occurs when molten rock moves from a planet’s hot interior onto its surface. The molten rock is called lava when it reaches the surface through an opening called a volcano. Weathering and Erosion Weather or small impacts break down rocks. The broken material is moved by a group of processes called erosion. The materials may form dunes, new layers of rock, or other features. Impact Cratering A small object sometimes hits a planet’s surface so fast that it causes an explotion. The resulting impact crater is often ten times larger than the object that produced it.

ATMOSPHERES

Atmospheres on terrestrial planets mainly formed from gases that poured out of volcanoes, If a planet’s gravity is strong enough, it pulls the gases in and keeps them near the surface. If a planet’s gravity is weak, the gases expand into outer space and are lost.

PLANTES ORBITING THE SUN AT DIFFRENT DISTANCES.

1. what is an AU?

An AU or Astronomical unit is earth’s average distance from the sun. An AU is about 150 million kilometers.

2. Why do the planets all orbit in one direction?

More than 99% of all mass in the solar system is in the sun. The gravitational pull of this huge mass causes planets and most other objects in the solar system to move around, or orbit the sun. The shape of each orbit is an ellipse a flattened circle or oval. A circle is a special type of ellipse. Most of the planet’s orbits are very nearly circles. Only one planet  Pluto has an orbit that looks a little fattened insted of round.

3. What are two regions of the solar system?

The first four planets Mercury, Venus, Earth, and Mars are relatively together and close to the Sun. They define a region called the inner solar system . Farther from the Sun is the outer solar system.

Max: hi

Maryam: I need help, I don’t get how the position of the sun and the moon affect earth

Maryam: Please help me

Max: Ok, When you look at the moon, you see a bright shape that is teh lit part of the near side of the moon. The unlit part is hard to see.

As we see the Moon only in reflected light, it shows distinct phases, depending on the angle made between itself, the Sunand the Earth. At New Moon, all three bodies are aligned, with the Moon between the Earth and the Sun. During this phase, despite the absence of direct illumination by the Sun, the lunar surface is just visible in light reflected from theEarth. Full Moon occurs when the Earth lies directly between the Sun and the Moon, with first and last quarters occurring at the 90° and 270° positions. The time taken from New Moon to New Moon, called the synodic month, is 29 days, 12 hours, 44 minutes.

Sun light streams past Earth and the moon, lighting one side of each body. Beyond each body is a long, thin cone of darkness where no sunlight reaches a shadow in space. The two bodies are far apart, so they usually miss each other’s shadow as the moon orbits earth. However, if the moon, the sun, and earth line up exactly, a shadow crosses earth or the moon. An eclipse occurs when a shadow makes the sun or the moon seem to grow dark. In a lunar eclipse, teh moon darknes. In solar eclipse, the sun seems to darken. The moon becomes dark during a lunar eclipse because it passes through earth’s shadow. There are two parts of earth’s shadow. The umbra is teh darkest part. Around it is a spreading cone of lighter shadow called the penumbra. Just before a lunar eclipse, sunlight streaming past earth produces a full moon.

Max: And a solar eclipse is when

Max: Now tides,

Tides are periodic rises and falls of large bodies of water. Tides are caused by the gravitational interaction between the Earth and the Moon. The gravitational attraction of the moon causes the oceans to bulge out in the direction of the moon. Another bulge occurs on the opposite side, since the Earth is also being pulled toward the moon (and away from the water on the far side). Since the earth is rotating while this is happening, two tides occur each day.

Spring tides are especially strong tides (they do not have anything to do with the season Spring). They occur when the Earth, the Sun, and the Moon are in a line. The gravitational forces of the Moon and the Sun both contribute to the tides. Spring tides occur during the full moon and the new moon. The Proxigean Spring Tide is a rare, unusually high tide. This very high tide occurs when the moon is both unusually close to the Earth (at its closest perigee, called the proxigee) and in the New Moon phase (when the Moon is between the Sun and the Earth). The proxigean spring tide occurs at most once every 1.5 years.

Neap tides are especially weak tides. They occur when the gravitational forces of the Moon and the Sun are perpendicular to one another (with respect to the Earth). Neap tides occur during quarter moons.

I want to know more about the moon because I have a TEST tomorrow about, The Moon is earth’s natural satellite, could you help me please.

Romina.

Dear Romina

mmmmmmmm… well first of all my name is Lulu, I know almost everyhting about space. Second of all I’ll help you,

The Moon is the earth’s sole companion, orbiting at an average distance of 384,400km. It follows us on our path around the sun , making one orbit of us (as seen against the background of stars) every 27 days, 7 hours, 43 minutes. This period is referred to as the sidereal month. The Moon’s equatorial diameter measures 3,476km making it less than one third the diameter of the earth.

The half of the moon’s surface that constantly faces earth is called the near side. The half that faces, away from earth is called the far side. Much of the moon’s surface is light -colored. Within the light-colored areas are many small, round features. There are also dark-colored features, some of wich cover large areas. Just as on earth, features on the moon are given names to make it easier to discuss them. Early astronomers thought that the dark areas might be bodies of water, so they used the latin word for ”sea.” Today, a dark area on the moon still called a lunar mare. The plural form is maria. The maria are not bodies of water, how ever. All of the features that can be seen on the moon are different types of solid or broken rock. The moon has no air, no oceans, no clouds, and no life. The light colors areas of the moon are higher at a greater altitudes then the maria, so they are called the lunar highlands. The ground of the lunar highlands is rocky, and some places are covered with a powder made of finely broken rock. The highlands have many round features, called impact craters, that formed when small objects from space hit the moon’s surface.

I hope now you understand.

sincerely,

Lulu

Just as a day is the time it takes earth to rotate once on its axis, a year is the time it takes earth to orbit the sun once. In astronomy, a revolution is the motion of one object around another. The word revolution can also mean the time it takes an object to go around once. Earth’s orbit is not quite a perfect circle. In january, earth is about 5 million kilometers closer to the sun than it is in july. You may be surprised to learn that this distance makes only a tiny diffrence in temperatures on earth. However, the combination of earth’s motion around the sun with the tilt of earth’s axis does not cause important changes of temperature.Most locations on earth experience seasons, patterns of temperature changes and other weather trends over the course of a year. Near the equator, the temperatures are almost the same year around. Near the poles, there are a very large chages in temperature from winter  to summer. As earth travels around the sun, the area of sunlight in each hemisphere changes. At an equinox, sun light shines equally on the northern and southern hemispheres. Half of each hemisphere is lit, and half is in darkness. At a solstice, the area of sun light is at a maximum in one hemisphere and a minimum in the other hemisphere. Eqinoxes and solticeshappen on or around the 21 days of certain months of teh year.