The Giant Sequoia

The world's largest tree by volume is sequoiadendron giganteum, otherwise known as the giant sequoia. Perhaps you've heard of them.

The President, Source

These redwood trees occur naturally only on the western slopes of the Sierra Nevada mountains in California. This highly exclusive environment means that there aren't very many of these trees and that they are uniquely susceptible to climate change. They are, however, amazing creatures. They usually grow between 50 to 85 meters tall (160 to 279 ft) and 6 to 8 meters (20 to 26 ft) in diameter. Some have even been measured up to 94.8 meters (311 ft) tall and 17 meters (56 ft) in diameter. That's huge. These trees are truly staggering, it is hard to conceptualize just how monumentally large they really are.

These trees are huge. Source

Being an evergreen, this tree lives in a very cold climate. Even though it is snow laden most of the year, the leaves of a giant sequoia will never lose their green color. These trees keep their seeds in cones, just as you might expect, but these cones are unique. A giant sequoia can keep its cones closed for up to 20 years or more. The only way for these cones to release their seeds is if they become dried out. This drying usually occurs during low-intensity forest fires where convection currents take heated air up into the canopies of the trees and dry out the cones. For a while, however, giant sequoias weren't reproducing very often. As it turns out, human forest fire prevention and livestock grazing significantly reduced the frequency of low-intensity forest fires. To make matters worse, the lack of fires allowed for white firs to begin to grow which could act as a ladder for high-intensity forest fires, allowing them to reach the vulnerable canopy of the giant sequoias. And the sequoias don't just depend on forest fires to open their seed cones, they also need these fires to clear away undergrowth to allow their seeds to grow. In response to the lack-of-fire crisis, the National Park Service began to set controlled fires back in 1970. So far they have been fairly successful.

Giant sequoias have thick bark to protect them from fires. Source

There used to be a logging problem with these huge trees. Giant sequoias are few in number and take a long time to grow, so logging was seriously damaging their population. As it turned out, however, the wood of these trees was fibrous and brittle, making it of little marketable value. When the public saw that these majestic trees were being cut down and made into toothpicks there was a strong movement to protect them. Now these trees aren't logged, but the mammoth stumps of old logged trees are still a tourist attraction.

The Mark Twain tree. Source

The Gegenschein (Picture of the Day: 12/6/12)

Gegenschein over Chile. Source

The night is not darkest when the sun is directly beneath your feet. The strange, dim light seen here will appear when the sun is in such a location, making the night bright (well, not very bright at all, but still). This effect is known as the gegenschein. This picture is of the gegenschein over Chile. It turns out that the sun's light will reflect off of interplanetary dust particles to create this effect. The gegenschein is extremely dim, so this picture is particularly rare. 

Besse Cooper Dies (Picture of the Day: 12/5/12)

Besse Cooper and grandson Paul Cooper. Source

This "Picture of the Day" is a bit sadder than the rest. A distinguished person has died. 116-year-old retired school teacher, Besse Cooper, passed away yesterday. She was the previous record holder for the worlds oldest person, but now that title falls to 115-year-old Dina Manfredini. What was Besse's secret to a long life? She said it was staying out of others' business and abstaining from junk food.

Here's to you, Besse, and your inspiring refusal to let time get you down!

Water on Mercury

On November 29th of this year, 2012, NASA announced something pretty amazing. There is evidence that water ice exists on the planet Mercury. Remember, Mercury is the closest planet to the sun, and its surface temperature can reach up to 700K (that is 427 C) if not higher. Scientists from NASA aren't making any bold claims yet, but some other sources that I've heard from are. It is difficult to tell what is true about this topic and what isn't, but I'll do my best to work it all out.

Mercury. Source

NASA went through some pretty complicated steps to find the evidence for water. The bare bones essence of what they did is this: they fired a radio wave at the poles of Mercury and measured what bounced back. The results were astonishing. There found pockets of highly reflective "stuff" at the bottom of what appeared to be craters on either pole. This significant because water ice is highly reflective in the radio wave spectrum. Not only that, but radio waves bounced off of water ice tend to be depolarized, and that's what happened to these radio waves. They came back depolarized.

Mariner 10, the last spacecraft to visit Mercury. Source

If Mercury is so hot, then how is it possible that there can be water ice? The answer to this is actually pretty clever. Mercury has a 3:2 orbital resonance around the sun, which, in English, means that it has a day of 176 Earth days. Every part of Mercury gets blasted by the sun eventually, so it stands to reason that any water on its surface would evaporate away into space (given Mercury's low mass). And while it's true that any water on Mercury should get blasted away it is also true that Mercury has a lot of impact craters. The poles of Mercury never get close to facing the sun, so there are regions in some of the deeper craters on the poles where light never shines. And because Mercury doesn't have an atmosphere, there is no hot air to heat the insides of these craters. It is therefore possible to have water on Mercury.

Locations of water on Mercury. Source

NASA's official claims don't exceed much more than what I have already said, but unofficially, there are some fascinating things related to their findings. It has been estimated that there might be as much as 1 trillion tons of water ice on Mercury. That is a lot of water. But what's even more fascinating is that there is evidence of water existing on slightly warmer parts of Mercury, surviving due to an insulative layer of... something. This "something" that keeps this water from melting could very well be organic matter. I'm not just talking about stray carbon atoms. It has been speculated that this insulating layer is composed of complex organic molecules indicative of either early life or the beginnings of life.

Life on Mercury? Could it be true? I don't know the answer to these questions, but it would be amazing to think that there could be something alive, or something that was once alive, on the hellish surface of this barren planet.

Giant Sequoias: The President (Picture of the Day: 12/4/12)

The President. Source

This giant sequoia, affectionately named the President, has helped us come to some ground breaking discoveries about these great trees. In this picture (actually several pictures, giant sequoias are huge) we see Steve Stillett and his team climbing around to do some research. They have been measuring different parts of this tree and taking numerous samples over the years in order to document the growth, age, and effect of climate change on these massive plants. Surprisingly, it has become apparent that older sequoias grow faster than young ones. This 3,200 year old tree has already reached a height of 247 feet, and will continue to grow as it ages. 

Lunar Halo Over Spain (Picture of the Day: 12/3/12)

A quadruple lunar halo over Spain. Source

This image is actually quite rare and fantastic. What we are seeing here is a quadruple lunar halo over Madrid, Spain. Falling ice crystals can, on occasion, create a lensing effect in the sky. This lensing effect can create halos around the sun or Moon. These halos are rare by themselves, but here we are seeing four of these rare halos. I was blown away by this picture and just had to share it.

Star Formation Regions

This topic is very relevant to me personally. For the last week or so I have been working on a project for my Astronomy class. My group and I chose to map out the star formation regions in the distant galaxy M33. Our pictures and analyses were certainly not professional, but I learned a lot about how stars form and how to identify star formation regions.

M33 through a hydrogen alpha filter. Not as good as the pictures I took... Source

Star formation regions are just dense nebulae, clouds of dust and gas floating around in outer space. Because most star formation regions are composed primarily of molecular hydrogen (H2) they are commonly called "molecular clouds". At a certain point these molecular clouds become dense and small enough due to gravitational processes and they begin to collapse. Once they collapse in on themselves they will divide into thousands of chunks that collapse further into protostars where they begin to heat up and burn before they become full fledged stars. It really is a fascinating process, and it's no wonder that many people call these star formation regions "stellar nurseries". They are the birthplaces of baby stars.

Orion nebula. A stellar nursery. Source

Maybe you're wondering how people identify star formation regions. Maybe you aren't wondering that, but I'm going to tell you anyway. Star formation regions tend to be large, cold areas of 70% hydrogen gas. Because their temperatures can hover around 10K they don't emit much light in the visible spectrum, but that doesn't mean that they don't still emit light. These hydrogen molecules are constantly moving around and exchanging electrons, which throws off photons at very specific wavelengths. Observers can locate star formation regions by searching for regions emitting large amounts of hydrogen light. This is done with a device known as a hydrogen filter. There are several kinds of hydrogen filters, but the most common is the hydrogen alpha filter. These filters work by filtering out all light except for light of the same wavelength as the hydrogen emission spectrum.

Hydrogen alpha filter. Source

Horsehead nebula through a hydrogen alpha filter. Source

Looking for hydrogen emission signatures isn't the only way to detect star formation regions, and it might not even be the best. An observer can also look for emissions around 24 microns, that's infrared light. The reason that this works is that protostars emit heavily at around 24 microns. Where there are protostars, there is a star formation region.

Sadly my hydrogen alpha images were not nearly as high quality as most of these images, but they were sufficient for my purposes. Mapping out star formation regions is way more fun that it should be.