banG Science

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Lunar Cycle 06

Un héroe estadounidense

vulnerable

Life Cycle of a Star 03

¿Podrá un latinoamericano

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HR Diagram: Relationship between Pressure and Gravity

Page. 14

Lunar CyclePage.7

Day and NightPage.5

2 | Vol 105| Year 07 | No. 02| 2013| www. banGscience.co | BanG | @banGscience |

Relationship between gravity and pressure in a MS StarBy,Barry Xie

MInd-BogglerBy, Gianluca Percovich

Numbers in the newsBy,Ghaled A. Mystery photo

By,Gianluca Percovich

mystery photoBy,Aaron Feleke

Table of Contents 8-9 Feature

03 Life Cycle of a Star

4 Tides

6 Lunar Cycle

7 Seasons

Crossword puzzleBy, Aaron Feleke

5 Day and NIght

Ask banG scienceBy,Ghaled A.

Mystery photoBy,Nicolas M. Ovalle

Gross OutBy, Gianluca Percovich

Crossword puzzleBy,Nicolas M. Ovalle

ask banG scienceBy,Aaron Feleke

Cool JobsBy, Nicolas M. Ovalle

| Vol 105| Year 07 | No. 02| 2012 | www. banGscience.co |BanG |@banGscience | 3

What are the phases in the life cycle of a star? How does the star change phases in its life cycle?

By,Ghaleb A.

A star begins its life as a nebula, a cloud of gas (hydrogen) and dust floating in space.

Stars are born in nebulae. Disturban-ces to the nebulae form a star. A star is a lit globe of gas producing its own heat and light by nuclear fusions. Sur-face temperatures of stars range from 2000o C to about 30,000o C. Stars are colored red blue and white. Stars live for less than a million years and emit the same light as a million suns.

After a star comes a red giant. Red giants are large bright stars with cool surfaces. They form during the later stages of evolution when it begins to run out of hydrogen fuel in its core. They have diameters between 10 to 100 times that of the sun. They have surface temperatures between 2000o C to 3000o C. Very large red giant stars are called Super Giants. Supergiants have diameters up to 1000 times that of the sun and are up to a million times more illuminated than the sun.

Next up comes a Red Dwarf. These stars are cool and faint and live for up to a 100 billion years. The white dwarf is the last stage in a stars life cycle. They have mass like the sun but they are only 1% of the sun’s diameter.

They have surface temperatures of 8000o C. White dwarfs are the rema-ins of stars when they used up all their nuclear energy supplies. They cool and fade over a million years.White dwarfs are very dense due to gravitational effects.

Supernovas are the explosive deaths of stars. They are as bright as 100 mi-llion suns for a short period of time.

There are 2 types of supernovae:

Type 1: One star falls on a white dwarf causing ti to explode

Type 2: This happens when stars are 10 times more massive than the sun. Nuclear reactions cause them to explode. They leave behind neutron stars and black holes.

Neutron stars are made up of neu-rons. They are mad when supernovas explode forcing the electrons and protons to combine together. They are every darns and have diameters of about 20 KM. They have mass 3 times that of the sun. If it was any greater, it would shrink and become a black hole.

Black holes are formed by stars at the end of their lifetimes. They have great gravitational pulls that can suck up anything, even light. Their densities cannot be measured. They distort the space around them and can even suck in stars.

Life Cycle of a 10,000,000 Yearsis how long it takes to form a Protostar.

1,000,000 Timesis how much greater the luminosity of a Red Giant is to the Sun’s luminosity.

109 Timesis how much greater the size of the Sun is to Earth’s size.

29.5 Daysis how long it takes for the Lunar Cycle to complete.

12 Hoursis the approximate time it takes for the tides to switch in between low tide and high tide

3 Monthsis the lenght of one season

How is a star formed?

By,Ghaleb A.

Before we an-swer this question, what is a star? A star is a massive lit sphere made of plasma and is held together by gravity. A star is formed out of a cloud of cool, dense molecular gases. In order for the cloud o become an actual star, the cloud must collapse in on itself and increase in its density. There are two ways this can happen. The cloud of gases can either collide with another dense cloud or, if the cloud is near enough to a super-nova, it can encou-nter the pressure from the supernova and collapse. The next step depends on the size of the newly born star (called a protos-

tar.) If it is a small protostar it will only have enough energy to become a brown subdwarf (a sub stellar object that cannot main-tain high tempera-ture therefore can’t convert hydrogen to helium. If the protostar is smaller than the sun but not small enough to be a brown subdwarf, then it undergoes a pro-ton chain reaction to convert hydro-gen into helium. If the protostar is larger than the sun, it undergoes a carbon-nitrogen-oxygen cycle to convert the hydro-gen to helium.

Ask banG science

This is a Black Hole. When a star runs out of fuel, the core of the star starts pulling all the matter around it into the center. This process starts increasing the density of the object. There gets a point when the density and the gravitational pull is so great that not even light cannot escape. All around the black hole the light is distorted and is smudged around it. This photo shows a star at its final stage, a black hole. In this photo the black hole is smear-ing the image of the galaxy behind it .

Mystery Photo


Gross Out

Tides

Some of the sea creatures hidden by the sea are revealed from the tidal level receding. Every few hours things like this happen in locations with larger tidal level changes and diversity.

You have the sun and moon’s gravitational fields to thank for these tides as they way they work together and apart to change the water levels fairly often. The way it works is that as the sun and moon work paral-lel to create high tide levels causing the water to rise incredibly high for high tide and very low for the low tides. There is also a neap tide that occurs when the sun and moon are perpendicular to each other causing their gravitational fields to work against each other, thus causing low high tides and high low tides. Since tides are usually moving up and down you can see when the tides are incredibly high or low, by looking at rocks near the ocean looking for sea life or water.

Mind-Boggler

This is the Bay of Fundy in Nova Scotia, this location has some of the biggest tidal changes in the world at roughly six to eight feet an hour, with few places having

changes of forty to fifty feet of water. These changes are caused by the tides which is water level rising and falling due to the sun and moon causing large changes in gravity, Therefore changing the water level.




Day and Night

Cool Jobs

Video game animators have to simulate the day and night cycle to make a video game more re-alistic. This process requires for them to care-

fully study the day and night cycle and make sure that they have the cycle down to the very last detail. This would be a job that would appeal to a large amount of the teenage population. You do not only get to play games and animate, but you also get paid for doing what you enjoy.

Across2.The center of the earth that is usually the hottest.4.when your side of earth has sunlight.6.Hours in the day.9.an object that gives off light.11.how many years are equivalent to 730 days.12.not transparent ex: the earth and sun.14.the spinning motion of a planet on its axis.Down1.where most of the light and heat comes from during the day.3.the movement of an object around an-other object.5.The study of moons, stars, and other objects in space.7.the earth travels around the sun in an ________ shape.8.the shape of the earth.10.when you’re part of the earth is away from the sun.13.an imaginary line that passes through the center of the earth.


Lunar Cycle

Mystery Photo

Across3. number of days it takes to complete the lunar cycle9. The stage at which the moon is getting darker to reach New Moon12. The stage at which the moon is 50% illuminated ,and it comes after full moonDown1. The stage at which the moon’s bright side is increasing to reach First Quarter2. The stage at which the moon is getting darker to reach Third Quarter4. The direction at which the Moon orbits the Earth5. a second moon in one month. happens every 2.7 years6. The first stage of the Lunar Cycle7. The stage at which the moon is 50% illuminated ,and it comes before the full moon8. The stage at which the moon’s bright side is increasing to reach Full Moon10. The stage at which the moon is completely illuminated11. The side that gets illuminated first.

What’s that in the sky? Is it a bird, a plane, No its a First quarter Moon during the day! Because

of the way the Earth rotates some issues between day and night do occur, such as the moon appearing during the day, however something that makes this moon incredibly amazing is that it is one quarter of the lunar cycle while rotating showing the amazing prospect of the moon in this area showing that this moon is about to become a full moon as soon as the cycle hits two more phases.


What affects the seasons? Is it because the sun is closer to earth during the summer and farther away during the Winter.

By, Aaron Feleke

Seasons are not affected by how far the sun is away from the earth, it is affected by earth’s tilt, the rotation of the earth around the sun and the surface area the sun its the earth. Many people have this

misconception including Harvard graduates. There are 4 seasons; winter, summer, autumn (fall). Since the earth is a sphere, the suns rays are not distributed equally to every place of the earth and the surface area of which the sun rays hit decreases. Since the earth rotational axis switches the poles also switch side. If you you live in the Northern hemisphere when the North pole is facing away, it is summer. When the South pole is facing away from the sun it is Winter for the northern hemisphere. The land

around the equator is a very flat surface therefore it gets a higher surface area of sun rays. Because of this, land around the equator only have one season which is always summer. Since the South and North Poles are not directly in front of the sun and always are right at the bottom and the top of the earth, they do not get as much of the suns rays. Because of this, the north and south poles have cold weather which comes with winter.

Seasons

The photo shows the Lillaz waterfalls which is a tourist attraction at the Gran Paradiso National Park. This is a Italian national park in the Graian Alps which is between the Aosta Valley and Piedmont regions. The park is named after Gran Paradiso mountain, which is located in the park.This photo shows how the waterfall looks in the summer which is in the left and how it looks in the winter which is on the right. On the left you can see water flow down in the waterfall. It was about ninety degrees when that photo was taken. On the right, you can see sheets of ice just freezing the water in place. From this you can infer that the the temperature is below freezing or 0 degrees celsius.

Ask banG science

Mystery Photo


HR Diagram: Relationship between gravity and pressure

On approximately its ten-billionth birthday – that is, in around five billion years from now – the hydrogen supply in the core of the Sun will be exhausted and the generation of energy will shift to the outer layers. As a result of this change, the Sun will expand and become a red-coloured giant star that engulfs the planets closest to it – Mercury and Venus.

By,Barry Xie

AMain Sequence star is one that has similar proportions in relation between brightness, mass and temperature. The color of a star is usually decided by the its temperature. The hottest stars are colo-

red blue, while the least hottest stars are colored red. In between these two are colors such as blue, white, and orange. In addition, as the brightness and temperature increase, the size also increases proportionally. Most stars follow this pattern, and are therefore classified as Main Sequence Stars. The

Key DefinitionsMain Sequence Star - The main sequence is a continuous and distinctive band of stars that appear on the Hertzsprung-Russell Diagram.Gas Pressure - A result of fusion; the force that opposes gravity within a star.Gravity - The force that attracts a body toward the center of the earth, or toward any other physical body having mass.Fusion - The process or result of joining two or more elements together to form a single element.Core - The gravitational center of a star, where fusion within a star occurs.Shell - An outer gaseous shell surrounding the core, comprised mostly of hydrogen and helium.Hertzsprung-Russell Diagram - a scatter graph of stars showing the rela-tionship between the stars’ luminosities versus their temperatures.

Feature


Feature

best way to show the trend is on the Hertzs-prung-Russell Diagram.The diagonal along the middle represents the Main Sequence Stars.

Makeup of a Main Sequence StarA main sequence star has essentially two

parts. The “core” which serves as a center for the gravitational force within the star. The second is the “shell” that surrounds the core, and its function is to conduct the energy released from the core to the surface, where the energy takes the form of heat and light that is emitted. The shell is composed mainly by hydrogen and helium. The chemical makeup of the star is around 93% hydrogen, 3% helium, with traces of other elements.

Pressure in a Main Sequence StarAs a result of the process of nuclear fusion

within the core, gas pressure is produced. This gas pressure has an outward force, as its goal is to escape outside, from the core to outer space. This gas pressure helps sustain the shell of the star, and also pushes out on the star.

Gravity in a Main Sequence Star

Within a Main Sequence Star, as we mentioned earlier, is the star’s core. This core is the very center of the gravitational pull of the star, or in other words attracts everything to it. The force of gravity, which is generated by the star’s own mass and size, compresses the star, and keeps it in a bound shape, so that none of the substance escapes.

Balance of the two forces

The two forces of gravity and pressure are im-portant, because they help keep a star in its form. They are opposite forces, and are ideally of the same strength. Gravity helps contain the shell of the star, forming the outside border of the shell. Gas Pressure is from the core, and defines the border between the core and the shell.

Equilibrium

Equilibrium is the state where both gravity and gas pressure emitted are balanced. This does not mean there is no change at all within the star, only that the star’s gas pressure to gravity ratio has no large net change. During the majo-rity of a star’s life, equilibrium is achieved, and there is no drastic change to the star. The range

of

which a star stays within equi-librium varies on each star, but is usually the duration of how long the hydrogen fusion process within a star lasts. this is because it generates a steady flow of gas pressure during this period of time.

Death of a star

Once the star runs out of fuel (in this case, not enough hydrogen atoms to fuse together) the star starts to cool down. Due to there being none to little gas pressure being produced, the shell of the star falls into disarray. The core of a star starts to contract, and becomes even denser, increasing its force of gravity even further. As the stars gravity is stronger, the star is conti-nuously condensed and made more compact, until the entire star collapses. The final destina-tion of the star is determined by its initial mass.

Types of Fusion

Although there are multiple kinds of fusion, there are three that make up 99% of all fusion processes. They are Hydrogen Fusion, Helium Fusion, and Carbon Hydrogen. The process of fusion is taking two of the same elements, combining the two (which generates enormous amounts of energy), to create a different ele-ment. For example, take the process of Hydro-gen Fusion. It takes two atoms of Hydrogen,

combines the two to release certain amounts of energy, and the two atoms of Hydrogen become one Helium atom.

Main Sequence Stars and Equilibruim

A main sequence star has to be in equilibrium at all times, and are mostly generating energy by hydrogen fusion. This is because later in a star’s life cycle, the star expands, becoming a red giant or a supergiant. The star will then collapse, and the star will most likely become a white dwarf, which is also not included as a Main Sequence Star.

Conclusion

As a summary, pressure and gravity must be in equilibrium at all time within a Main Sequen-ce Star. This gas pressure is produced through the process of fusion, which also produces the energy necessary to sustain the star. The gravity of a star is focused around its core, which is where the process of fusion takes place and is also the densest spot within the star. Once a star falls out of equilibrium between the two forces, the star life span will end, and will collapse to either become a neutron star, white dwarf, or will end in a supernova.

Classifications

In order to be a main sequence star, a star must achieve the following criteria.

1) The size must increase proportio-nally with the amount of heat energy it releases.

2) The size and temperature must fit with color it is represented by.

Temperature, in Kelvin

2,000–3,700 3,700–5,200 5,200–6,000 6,000–7,500 7,500–10,000

10,000–33,000

≥ 33,000

Color Red Orange Yellow Yellow/White White Light Blue Blue

Solar Masses ≤ 0.45 0.45–0.8 0.8–1.04 1.04–1.4 1.4–2.1 2.1–16 ≥ 16

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