cwnl:

The Life Cycles of Stars

Imaged Above: Stellar evolution by Chandra X-Ray Observatory

Introduction

Initial Note: There’s a spilled set of jewels and treasures sparkling out there in the night sky most people are in the habit of ignoring whilst having their strolls to wherever their destinations may be. While some of us may already be aware of the little fact that we’re made of the same chemical elements as these cosmic gems, some still perceive them as merely bright little dots of light emitting faint photons into our eyes whenever the Sun clocks out for the day. However, you’d be surprised at just how active and diverse these dots of concentrated matter truly are. In the following set of posts courtesy of NASA, we’ll be taking a comprehensive look into the life of Stars.

What Is A Star?

A star is a sphere of gas held together by its own gravity. The force of gravity is continually trying to cause the star to collapse, but this is counteracted by the pressure of hot gas and/or radiation in the star’s interior. This is called hydrostatic support. During most of the lifetime of a star, the interior heat and radiation is provided by nuclear reactions near the center, and this phase of the star’s life is called the main sequence.

Before and after the main sequence, the heat sources differ slightly. Before the main sequence, the star is contracting and is not yet hot enough or dense enough in its interior for the nuclear reactions to begin. During this phase, hydrostatic support is provided by the heat generated during contraction.

After the main sequence, most of the nuclear fuel in the core has been used up. The star now requires a series of less-efficient nuclear reactions for internal heat. Eventually, when these reactions no longer generate sufficient heat to support the star against its own gravity, the star will collapse.

The Cycle

A star’s life cycle is determined by its mass. The larger the mass, the shorter the life cycle. A star’s mass is determined by the amount of matter that is available in its nebula, the giant cloud of gas and dust in which it is born. Over time, gravity pulls the hydrogen gas in the nebula together and it begins to spin.

As the gas spins faster, it heats up and is known as a protostar. Eventually the temperature reaches 15,000,000 °C and nuclear fusion occurs in the cloud’s core. The cloud begins to glow brightly. At this temperature, it contracts a little and becomes stable. It is now called a main sequence star and will remain in this stage, shining for millions or billions of years to come.

As the main sequence star glows, hydrogen in the core is converted into helium by nuclear fusion. When the hydrogen supply in the core begins to run out, the core becomes unstable and contracts. The outer shell of the star, which is still mostly hydrogen, starts to expand. As it expands, it cools and glows red.

The star has now reached the red giant phase. It is red because it is cooler than it was in the main sequence star stage and it is a giant because the outer shell has expanded outward. All stars evolve the same way up to the red giant phase. The amount of mass a star has determines which of the following life cycle paths it will take after the red giant phase.

(Source: ikenbot)

cwnl:

Quick Space Fact:

The light hitting the earth right now is 30 thousand years old

The energy in the sunlight we see today started out in the core of the Sun 30,000 years ago – it spent most of this time passing through the dense atoms that make the sun and just 8 minutes to reach us once it had left the Sun! The temperature at the core of the sun is 13,600,000 kelvins. All of the energy produced by fusion in the core must travel through many successive layers to the solar photosphere before it escapes into space as sunlight or kinetic energy of particles.

Via Listverse

(Source: ikenbot, via ikenbot)

cwnl:

Quick Space Fact:

We are moving through space at the rate of 530km a second

Our Galaxy – the Milky Way is spinning at a rate of 225 kilometers per second. In addition, the galaxy is travelling through space at the rate of 305 kilometers per second. This means that we are traveling at a total speed of 530 kilometers (330 miles) per second. That means that in one minute you are about 19 thousand kilometers away from where you were. Scientists do not all agree on the speed with which the Milky Way is travelling – estimates range from 130 – 1,000 km/s. It should be said that Einstein’s theory of relativity, the velocity of any object through space is not meaningful.

Via Listverse

(Source: ikenbot, via ikenbot)

cwnl:

Carbon Dioxide Ice in the Late Summer

Mars has extremely large temperature changes from winter to summer compared to the Earth. It gets cold enough to freeze carbon dioxide out of the atmosphere during the winter, but this ice is unstable when the warmer summer arrives and forces it to sublimate (transform directly back into a gas) away.

Credit: NASA/JPL/University of Arizona

(Source: ikenbot)

(Source: circlesofcircles)

cwnl:

Solar-Type Stars (Medium)

This is the kind of star we are most familiar with. It is the type of star we see in the day time, the sun that warms planet Earth and the rest of the planets within our Solar System. They’re distinguishable by their bright yellow hues.

(Source: ikenbot)

Quick Space Fact:

Did You Know Some of The Rocks Found on Earth are Actually Pieces of Mars?

Both Earth and Mars have been slammed by large asteroids in the past. Although most of the debris kicked up by the impact falls back down on to the planet, some of it can be ejected so quickly that it escapes Mars entirely. These ejected meteorites can orbit the Solar System for millions of years before they finally crash down on other worlds. Some have crashed on Earth, and been identified by scientists. Tiny amounts of Mars’ atmosphere were trapped in the meteorites, and this is how scientists were able to study the Martian atmosphere before sending the first spacecraft.

via NASA

(Source: ikenbot, via ikenbot)

cwnl:

Big Asteroid to Cross Earth-Moon Orbit Tuesday

An asteroid the size of an aircraft carrier is to soar past the Earth this week and, while NASA is certain that the space rock will not hit us, it will be our closest encounter with such a large chunk of rock in three decades.

The 400-yard-wide asteroid is called 2005 YU55 and at the point of closest approach it will graze our planet at 201,700 miles — about 10 percent closer to Earth than the Moon’s typical orbit.

(via ikenbot)

cosmo-logic:

Stellar Evolution (source/fullsize)

(via theowlintheolivetree-deactivate)

davereed:

deckofficer:

Every space mission from the last 50 years mapped out.  Pretty awesome.  Click for hi-res.

by National Geographic

(via hilker)