Solar Composition

Most of us know that the sun is a giant ball of gas, but what exactly is it made of? Astronomers have been working on uncovering the sun's exact composition for many years, and this is the current theory...

Composite image of the sun on 9/7/2011 from the Solar Dynamics Observatory

Since different elements have different weights, we can talk about the solar composition in terms of weight. The sun weighs about 4*10^30 pounds (that's a 4 with 30 zeros after it!). About 74% of that mass is Hydrogen atoms, 25% of the mass is helium atoms, and 1% is a variety of other elements including oxygen, carbon, iron and others. Another way to think of the sun's composition is in terms of number of atoms (or volume, essentially). In these terms,  92% of the sun is filled with hydrogen atoms, about 7.8% is made of helium atoms, and that other tiny 0.2% is made of heavier elements. This composition is ever changing, as the sun is continually undergoing fusion of hydrogen into helium in its core. The sun is also shedding mass in solar wind and solar flares, but this amount is so small compared to the size of the sun that it's practically unnoticeable. Over a human lifetime the composition of the sun will stay pretty much constant.

So how did astronomers figure out what the sun is made of? Tune in later this week to find out!

Image courtesy of NASA/SDO and the AIA, EVE, and HMI science teams

Earth's Magnetic Field

It's a good thing Earth has a magnetic field! If it didn't, we'd be showered with solar radiation 24/7 and probably wouldn't survive for very long! But what is this magnetic field and how does it work? Astronomers have some idea…

The Earth's magnetic field is thought to be caused by a molten iron core deep inside Earth. With fancy math and physics one can prove that a molten electrically conductive material  that is spinning will produce a magnetic field. This magnetic field is very similar to the one a bar magnet produces, just on a much larger scale. A bar magnet always has a north and south pole. If you sprinkle some iron filings around a bar magnet, you will see that they align themselves in a curved pattern extending from the north to the south pole. The iron filings are tracing the magnetic field lines, or in other words the force, produced by the magnet. One would naturally think that the north pole on Earth should represent the north end of the "bar magnet" inside Earth, and the south pole the south end, but it's actually the exact opposite! Let's stop and think… opposite ends of a magnet attract, while similar ends repel. So if a compass always points North, it must be attracted to the southern magnetic pole! Another fun fact about our magnetic poles is that they do not coincide with the physical north and south poles on Earth, they actually move quite a bit each year! In 2005, the north pole was measured to be at about 83N 114W, but today it is further west by roughly 10 degrees! Astronomers and geologists don't fully understand the production of Earth's magnetic field, and therefore don't fully understand why it is moving, especially at such a quick pace. There's much more work to be done on this subject.

Apollo Moon Landings

I'm sure many of you remember that glorious day when man first stepped on the moon. The date was July 16, 1969, the mission: Apollo 11. Neil Armstrong, Buzz Aldrin, and Michael Collins left the Earth that day, and five days later made history by putting the mark of a human being on another astronomical body.  This is the day most people think of when someone mentions the moon landing, but we've actually sent man to the moon a total of 7 times. Missions Apollo 11 through Apollo 17 all rocketed towards the moon, and all but Apollo 13 landed successfully on the moon. During each mission astronauts set foot on the moon, and the Apollo 15 mission was the first to drive a vehicle on the moon, called the lunar rover (pictured above). After Apollo 17, manned missions to the moon were canceled due to lack of funding. NASA needed to make some budget cuts, and decided to put money towards Skylab instead. Man has not set foot on the moon since. Many orbiters and robotic landers have studied the moon since then, and the next mission, a set of orbiters called GRAIL, is set to launch from Cape Canaveral on September 8th, 2011.

The movie Apollo 18 comes out this Friday and it looks like it's going to be a great sci-fi thriller! It's based on the idea that NASA actually did send astronauts to the moon again as an Apollo 18 mission, but never told the world because of what they found…. aliens on the moon! Of course these creatures are hostile and live on the dark side of the moon, what sci-fi movie would be complete without killer aliens? I'm surprised it took 40 years to come out with a film like this, and I hope it's a good one!

Image Credit: NASA

A Planet Made of Diamond!

 Artist's impression of the diamond planet

You read that right! Astronomers believe that they have discovered an exoplanet made of diamond! How can this happen? Well here's the scenario. There was once two stars orbiting each other in a binary system in our galaxy. One star was  bigger than other, and began stealing material from the other smaller star. Over time, the large star stripped so much material off the small star that it couldn't withstand the external pressure and exploded as a supernova! This huge explosion cleared away any gas and star material in the area, leaving behind only the core of the large star (now called a neutron star) and a the core of the small star. Because this is a binary system, the leftover cores began to orbit each other extremely quickly. The angular momentum in the system (speed of rotation, essentially) caused the neutron star to spin on its axis in a fraction of a second (once every 0.0057 seconds to be exact)! We call these stars pulsars, as they emit light from their poles which appears as mili-second pulses in radio telescopes. The small star's core now orbits the pulsar so closely that it only takes two hours for the planet to go around the star! Based on orbital speed and distance to the host star, astronomers speculate that it is less than half the size of Jupiter, but weighs about 1.2 times as much! This high density suggests that the star is made of carbon, and its close proximity to the host star would make it crystallized. And you know what crystallized carbon is… Diamond! A planet 5 times the size of Earth made diamond. I Think I agree with other astronomers who suggest that we somehow find a way to travel to this planet and bring some diamond back! (Though it's quite implausible.) Wouldn't it be awesome to have an exoplanet-diamond ring ? And I thought a meteorite necklace was cool!

Our Solar System

After some recent teaching experiences and discussions, I've come to realize that many adults have forgotten the basics about our solar system. So today ADYK presents a Solar System "refresher" to help you recall those astronomy facts you learned back in elementary school.

 

Above is a collection of real telescope images of the planets in our solar system (NOT to scale!). This is what the planets look like when you use very high power telescopes or planet orbiting satellites to observe them.

Our solar system contains 8 planets (Pluto doesn't count anymore),  one star (the Sun) and two large asteroid belts. Mercury, Venus, Earth and Mars and the four closest planets to the sun and are often called the terrestrial or rocky planets. They are basically giant chunks of rock in a roughly spherical shape. Mercury is made mostly of metals and is heavily cratered like the moon. Venus has a thick carbon dioxide atmosphere, and is essentially the poster child for what would happen if global warming got out of hand on earth. Earth is our home and is made of 70% salt water and has a rich Nitrogen atmosphere. Mars is the red planet where all the aliens live, supposedly. (*wink wink*). Beyond Mars sits the first asteroid belt, filled with oddly shaped rocks the size of people to the size of cities. Jupiter, Saturn, Uranus and Neptune sit beyond the asteroid belt and are often called the gaseous or Jovian planets. Jupiter is the largest planet, about 10x the size of Earth, and has that big red spot. Saturn is the one with the prominent ring structure, though all Jovian planets have a slight ring structure around them. Uranus and Neptune are the blue planets, and are about 4x the size of Earth. Uranus is turned on it's side, meaning that its spin axis is tilted 90 degrees from being straight "up and down". Past the Jovian planets is the Kuiper belt, a giant ring of asteroids which defines the edge of the solar system. Pluto, it's moons, and over 70,000 similar objects orbit in this ring. Most everything there is small, cold, and icy.

There you go, elementary school astronomy class in one paragraph!

Distance To The Stars

The stars are really far away, but how exactly do astronomers measure their distance? There are many different ways to measure the distance to an astronomical object, but for "nearby" stars, the easiest method is to use parallax. A stars parallax is a measurement of it's apparent position on the sky, related to very distant background stars, at two different positions in the Earth's orbit around the sun.

 

In the image above we have the Earth orbiting counterclockwise around the sun, a nearby star which we want to measure the distance to, and distant stars which appear stationary during the Earth's movement around the sun. When the Earth is to the left of the sun, the nearby star appears to be amongst distant stars on the right hand side. Six months later, the Earth is to the right of the sun, and the star appears amongst distant stars on the left. Half the apparent angular distance on the sky that the nearby star appeared to move is called parallax and is measured in arcseconds. Arcseconds are an angular measurement on the sky, defined such that a star that in one parsec (~19 trillion miles) away from Earth will have a parallax of 1 arcsecond. Using basic geometry, we find that the distance to any nearby star (in parsecs) is equivalent to 1/parallax (in arcseconds), or d=1/p. Just by using simple math that you probably learned in high school, you can calculate the distance to the stars. No calculus or crazy physics required! Now finding the distance to much more distant objects is a bit trickier, and will be the topic of future posts.

Image Credit: astroprofspage.com

We Really Are Stardust

Where did human life come from? That's the ultimate question. Science offers two solutions to this question. One is that life was placed here either by an intelligent being, or by chance via a meteorite back when the Earth was very young. The second option is that space is filled with the building blocks of life, and the gas and dust that the Earth formed from happened to contain these materials. Until now there was really no strong proof either way, but just recently astronomers made a huge discovery. Astrobiologists were studying the composition of a meteorite they found in the arctic and discovered guanine and adenine, two of the four building blocks of DNA! These proteins have never been found in outer space before, and astronomers believed conditions to be too harsh for these proteins to survive. Finding guanine and adenine in this meteorite suggests that these and other building block of DNA are created during supernova explosions and exists all throughout outer space. It's likely that these materials existed in the circumstellar disk around the sun back when it was very young, and therefore ended up here on Earth.  This also promotes the idea that other intelligent life may be out there since the building blocks for life seem to be free floating through space. There are of course religious based views on the formation of life, which I respect very much, but from a purely scientific standpoint, it appears that we really are a product of the stars.

Image Credit: NASA
Go to NASA.gov to read the article pertaining to this discovery.