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4.6 Billion Years of Me

Saturday April 27, 2019:

4.6 billion years in service and counting...

Basic Facts:

- About 4.6 billion years old

- Diameter of 1.39 million km (864,000 miles)

- Mass of 2 x 10^30 kg (2 followed by 30 zeros)

- Average distance from Earth: 1 Astronomical Unit (AU) = 150 million km (93 million miles)

- Surface temperature: 5,500 C (10,000 F)

- Core temperature: 15,0000,000 C (27,000,000 F)

- G-type main-sequence star (spectral class)

- Made of plasma (ionized gas, 4th state of matter)

- Contains: ~73% hydrogen (H), ~25% helium (He), ~2% O, C, Ne, Fe

For the past 4.6 billion years, our closest star, the Sun, has been powering the solar system and keeping the planets, dwarf planets, asteroids, Kuiper Belt Objects (KBO), comets, and other contents bounded by its center of mass*. All this while the Sun orbits the center of the Milky Way Galaxy about 26,000 light years (ly) away. The orbit takes between 225 and 250 million years! Our Sun is 109 times Earth's diameter, 330,000 times Earth's mass, and is located only about 8.33 light minutes away (8 min 19 sec at light speed). (Light travels, in a vacuum (space), at 300,000 km/s, or 186,000 mi/s.) What's remarkable, to the matter of mass, it holds 99.8% of the solar system's mass. It contains mainly hydrogen (lightest and most abundant element in the universe), where under the extreme temperature and pressure of the Sun's core, fuses together to form helium yielding tons of energy. This process is called nuclear fusion. Do not be confused with nuclear fission. That's the process being used at today's nuclear power plants where heavier radioactive elements such as uranium is broken down to lighter elements. In fusion, two atoms fuse together to form a heavier one. For a star like the Sun, nuclear fusion proceeds for billions of years until there is no fuel left (the hydrogen then helium).

As the Sun ages, it will fuse together all the hydrogen that's left into helium. Since the core is hot enough, it will then fuse the helium atoms. After helium, the Sun's core cannot fuse heavier elements, therefore, the core will collapse under the Sun's intensive interior pressure. As that happens, the outer layer of the Sun expands into space, thus it gets bigger. The swelling of the Sun is expected to surpass Venus' orbit possibly into Earth's. Here, the Sun turns into a red giant and at this stage, our home the Earth is vaporized, sterilized of life as we know it. Does a supernova occur? No! The mass isn't great enough. Supermassive stars (>8 solar masses, 1 solar mass = mass of sun) undergo supernovae at the end of their lives. Instead, the Sun sheds its outer layers forming a planetary nebula and what's left in the middle is a white dwarf. White dwarfs don't fuse anything, it's more of a hot glow. Eventually the glow dissipates over the course of many billions of years. Yes, this is how our solar system ends. Whatever planets survive turn into rogue planets roaming the galaxy. Don't worry, though, this doesn't happen for another 5 billion years. A star like the Sun has a life expectancy of about 10 billion years. In the meantime, enjoy life!

Our Sun has an 11-year cycle (plus, minus few years) where solar activity is high and low. When activity is high, there are greater occurrences of solar flares and prominences (see image below). When activity is low, occurrences are less. For the past few years, we have been at a low. The last high was 2012/2013 and next should be around 2024. As you can see in the image above, there are a couple sunspots (right). During high activity, sunspots are common throughout the Sun. They are produced after the eruption of flares. These are cooler regions on the Sun's surface, so they are dark. (Still hot though.) Solar flares spew out Solar Energetic Particles (SEP) into space carried by solar winds outward. These charged (or ionized) particles travel at millions of km per hour. If the flare is aimed at Earth, it would take a few days to reach us. Our protective magnetic field deflects most of the particles, but some do make it to Earth's upper atmosphere producing the northern and southern lights, auroras. Did not get into layers of the Sun, but it's shown below. Be thankful to this star for your existence.

(*We orbit the sun because the center of mass is located inside of it. Center of mass is the point where the weighted relative position of the distributed mass sums to zero. As with stars orbiting the center of the Milky Way, the center of mass is located there. Center of Milky Way is home to Sagittarius A*, a supermassive black hole.)

Graphic created by Kelvinsong.

Information has been sourced from

Visit the link below for more information about the Sun:

The Sun is only one of hundreds of billions of stars in our Milky Way Galaxy. Additionally, at least hundreds of billions of galaxies that exist in the universe. There are plenty of other sun-like stars out there since they are main-sequence. Most stars are in the main-sequence. Stars are classified by type based on their size, temperature, and luminosity. The types are (hottest to coolest): O, B, A, F, G, K, M. (As mentioned before, the Sun is G-type with its surface temperature at 5,500 C.) In that order, you get blue supergiants (least common) to red dwarfs (most common). Much more on stars later.....

big dipper
Our Sun is only one of countless stars.

Inspire to imagine, explore, and capture the moment (space edition)

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27 avr. 2019

Space topic II

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