The Sun is a single pixel.

A good gold digger would know that diamond > gold > cash!

Never said I was a good gold digger.

Umbrasquall wrote:A good gold digger would know that candy > diamond > gold > cash!

cute

Neutron Stars

What happens if there is such a large concentration of mass in an object that electron degeneracy pressure fails to support the shape of a star? The collapse of the atoms inside such an object will form something called a neutron star. A neutron star is essentially an object that has nuclear density. That is, a neutron star is as dense as the nucleus of an atom and are composed entirely of neutrons. While a white dwarf is the mass of the Sun compressed to the size of the Earth, a neutron star is the mass of the Sun compressed down to an object the size of New York City.

There are several ways that these amazing objects are formed in the universe. One of the more interesting ways is from the result of a Type 1a supernova. Here's how the process works: Imagine a binary star system (two stars orbiting around each other) such as the Sirius system in the previous post. Binary/multiple star systems are common (1/3 of the stars in the Milky Way galaxy) and usually one star will be larger than its companion. The larger star will burn out it's hydrogen reserves much faster than the smaller star. In the Sirius system, we can see that the smaller Sirius B has already exhausted it's fuel, puffed away it's outer layers, and became a white dwarf. Now, if the Sirius stars were closer together, the white dwarf would gravitationally attract the atmosphere of the larger star. As more and more of the atmosphere of the larger star is pulled onto the white dwarf, the smaller star gains more and more mass because of the acreted material. When the white dwarf passes a certain threshold called the Chandrasekhar limit (about 1.4 solar masses), electron degeneracy pressure fails and the star collapses further. The nuclear reaction that follows releases a very large amount of energy that is the Type Ia supernova. Once the smoke clears, so to say, we are left with a neutron star.

The interesting thing about Type Ia supernovae is that they always release the exact same amount of energy. This is because they always occur when there is exactly 1.4 solar masses piled into a white dwarf. Thus, Type Ia supernova are also called "standard candles," because we know exacly how bright they should be. With a understanding of the reaction that fuels the explosion and a little calculation we can find out exactly how much energy every Type Ia supernova releases. This is a very valuable piece of knowledge, because if we know how much energy is released, we can calculate how far away this star is based on the actual brightness of the nova we observe. If we know how far away this star is, we know how far away the galaxy the star is in is. Many of the accepted distances to galaxies we know of are based off of these caculations that compose a system of distance estimation called "the distance ladder."

I realized a little after that last post that it was probably kind of not entertaining, so here's something that comes with a picture! Yay pictures.

http://upload.wikimedia.org/wikipedia/commons/0/0d/Hubble_ultra_deep_field_high_rez_edit1.jpg

This is one of the most famous photographs ever taken in the field of astronomy. It is an exposure called the Hubble Ultra Deep Field. There was no visible stars in this bit of sky (the area of the photo is 1/13,000,000th of the total area of the night sky), and it was selected in particular because there were no remarkable features.

The result is really a staggering one. Each of the lights you can see in this photograph is an entire galaxy. From the blobs to the tiny faint pinprick dots in the background. Each of these galaxies contain hundreds of billions to trillions of stars.

A few things to consider to appreciate the scale of this image.

• This is only what we can see after a certain amount of exposure. There are likely many more galaxies in this patch of sky that we did not see because the exposure was not long enough.
  
• This is a photograph that is limited by the size of the visible universe. Remember that light has a finite speed, we can only see as far as light has had time to travel. The visible universe is limited by this fact. Any galaxies further than a certain distance we cannot see because the light they emitted has not had enough time to reach Earth yet.
  
• This is only 1/13 millionth of the sky. Imagine looking down the length of a piece of 0.7mm mechanical pencil lead from arms length. The bit of sky covered by the round tip of that piece of lead is about how large the area of this photo is. There are 10,000 visible galaxies in this photo.
  
• Each dot is an entire GALAXY. There are only four or so stars in this photo. You can tell them apart from the galaxies by the glare they make against the lense, in the shape of a cross.

That's a lot of galaxies out there right? And don't forget each one has anywhere between 100 billion to trillions of stars. I remember reading a calculation that someone did once which showed that there are more stars in the universe than there are grains of sand on all the beaches of the Earth combined.

Umbrasquall wrote: Yay pictures.

Lol thats exactly what i thought

how can scientists c all this stuff? do they get paid just to look at stars? cuz i wouldnt midn an easy laid back job like that

A detailed mosaic of Jupiter's Great Red Spot, which is actually a storm (like a hurricane) on the "surface" of Jupiter that has lasted for hundreds of years. The scale is 11 miles/pixel for this image, which was compiled from pictures taken by the Voyager mission 30 years ago at a distance of 1.1 million miles. The spot itself is about the size of 3 Earths.

Whew, dayum... That's some pretty trippy stuff, considering how small we are in comparison to a storm on a planet so far out there...

For Umbra. <3

Resource: http://articles.cnn.com/2010-09-30/us/planet.discovery_1_rocky-planet-red-dwarf-star-habitable-zone?_s=PM:US
Astronomers: Newly discovered planet may be able to support life
Astronomers have discovered a new planet that just may be able to support life in a nearby solar system a mere 20 light years from Earth.

It's called Gliese 581g and is located in the constellation Libra. It circles the red dwarf star Gliese 581.

According to a research that is set to be published in the Astrophysical Journal, the planet is "squarely in the middle of the habitable zone of the star" which offers a very compelling case for a potentially habitable planet around a very nearby star.

When a planet falls in the "habitable zone" it means that it orbits the star at a distance that allows for the planet to have both liquid water and an atmosphere, two conditions that are considered important for life to exist.

"Our findings offer a very compelling case for a potentially habitable planet," said Astronomy Professor Steven Vogt of the University of California Santa Cruz who lead the research along with Astronomer Paul Butler of the Carnegie Institute.

To scientists a "potentially habitable" planet is not one where humans would want to live, but rather one that could sustain life.

The scientists believe the new planet has a mass three to four times that of Earth and orbits its star approximately every 37 days.

It's likely rocky planet, according to Vogt. Size is another factor in determining the likelihood of a planet to be able to support life. It has to be large enough to hold an atmosphere, but not so large that it becomes an "ice giant" like Neptune or Uranus.

"If we discover life outside our planet, it would perhaps be the most significant discovery of all time," said Ed Seidel of the National Science Foundation. "This is clearly one of the most exciting areas of science these days."

The report can be found at http://arxiv.org/list/astro-ph.EP/new.

I saw an article about that just the other day. I wasn't aware that it was in the Gliese 581 system though. This is a cool discovery because it means that Gliese 581 has at least 6 planets around it, very similar to our Solar System. Apparently the two planets that sandwich the new Earth-like Gliese 581g are similar to Mars and Venus, the two planets that are Earth's neighbors. Kind of a neat coincidence.

Of course it's a red dwarf star, which means that the system has a much much longer lifespan than our system. Planets that fall within the habitable zone in such a system will have many factors more time to develop life. But it also means that life would probably be very different if it existed. The energy output of a red dwarf is hundreds of thousands times less than a G-class star like our Sun. Planets would need to be closer to the star to stay warm enough for life. Plant life, if it existed, would be darker, perhaps even black, instead of green, in order to absorb as much light as they can. Furthermore, 581g is very close to the star and likely tidally locked, meaning that it doesn't rotate, with one side constantly facing the star and the other always in darkness. If the atmosphere and ocean currents provide enough convection the average temperature could be consistent. But planet life as we know it would be limited to the light side, meaning that any animal life would either have to be on the same side, or in the eternal twilight zone (the ring of land between the light and dark side) in order to survive.

The Gliese system is already older than our system by more than 2 billion years, and red dwarfs have expected lifespans of trillions of years, compared to the 10 billion estimated of the Sun. It's possible that life will develop on planets like this within that time. Or it is possible that life/civilization had already developed and ended on these planets long before we became aware of the Gliese system. Interesting points to consider.