The Orange Moon

During the night of August 7-8, I saw the moon in a way that is rarely seen. The moon was a bright orange-red colour in the night sky. At the same time, there were very little stars visible in the night sky, for some reason. It was quite perplexing why, but I decided to not worry about it and to focus on the Moon that night.

The Red Moon

The Red Moon

 

Many months ago, I was working on RASC’s (Royal Astronomical Society of Canada’s) Explore the Universe certificate program. My progress with the certificate stagnated for a while, and after realizing that I didn’t document when and with what I saw each celestial object with, I learned that I cannot use my current observations towards my certificate. Therefore, I had to start over again. It was heartbreaking to start again after working hard to find and observe those objects.

Despite that setback, I found a great opportunity to view this strange, yet beautiful moon. I quickly aligned my telescope to the Moon and I began looking at the features of the Moon. Last time I explored the Moon’s surface features, the moon was a waning crescent, which made it difficult to find all the surface features (mares, and craters) necessary. Here is a link to the previous blog post chronicling that night. During this night, the Moon was coming very close to its full phase, which meant that more surface features were visible and it would be easier to find them.

Since I had done this before, it was easy to find the mariae I found during my previous search, such as Oceanus Procellarum, Mare Insularum, and Mare Imbrium. I also found Crater Copernicus and the Crater Plato. After finding those mariae and craters, I went on to find other features that were in the dark side the last time I observed the Moon in its waning crescent phase. Here is an interactive map of the Moon to follow.

On the Moon, beside Mare Serenitatis is Mare Tranquilitatis, where Apollo 11 first touched down on the Moon. I then found Mare Crisium, which is located North-East of Mare Tranquilitatis. It quite perplexing how all the Mariae’s regolith contrasts with the regolith surrounding the mare. From my research, I learned that the formation of the Mariae started 3.9 Gyrs (Billion years) ago. At that time, the Moon’s crust had solidified and was being bombarded by many asteroids. Then there was a large volcanic event which flooded the plains with magma. It’s unclear why the mariae are concentrated in the near side but one theory suggests that the near side’s crust is thinner than the far sides, which made it easier for volcanoes to erupt at the near side. Another theory suggests that since the Earth and the Moon were closer to each other (10x closer) when they were formed, the hot Earth heated the near side, which delayed its cooling process. Whatever the reason, I’m glad humanity has the opportunity to see the mariae.

After finding many mariae, still not finding enough of the mariae on the list, I went back to Mare Imbrium to look for other mariae. I soon realized that north of the Plato crater there was Mare Frigoris, also known as the Sea of Cold. Looking at my list, I found the required number of mariae on the list for the certificate. I then moved onto finding the required numbers of craters.

It was considerably harder to find the craters on the Moon as most craters, unlike mariae, are not as recognizable, however, I was up to the task. After finding Crater Copernicus and Crater Plato, I found Crater Kepler, which was not on the list. I then found Crater Tycho, which looks similar to Crate Copernicus. In my previous attempt at looking at the Moon, Crater Tycho was hidden in the dark side of the terminator, which divided the Moon between the illuminated and the unilluminated side.

I then found Crater Aristarchus, which was also not on the list. After finding that crater, I was able to find three more craters to complete the requirements of my list. They are Craters Ptolemaeus, Aristoteles, and Posidonius. After finding Crater Posidonius, I finished most of the lunar requirements of my list. It felt great to finally start that certificate again.

Since the night sky was so hazy for some reason, I wasn’t see anything else, and as a result, I decided to pack up my equipment and bring it back to my house. It was a successful night of observing. I saw a beautiful red Moon, and identified many of its features. One thing that made today unique was the hazy red moon. After some research, I realized that the moon was red because of the smoke from the Northwest Territories Wildfires moving down towards Ontario. It was intriguing how events far away can effect us back home.

Happy Observing!

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Magnetic Fields: From the Sun

It’s not just the planets that have magnetic fields. The Sun also has a very large and dynamic magnetic field.

The sun’s magnetic field is formed much like on Earth and Jupiter. There are convection cells that bring heat from the sun’s heat sources to the surface. These convection cells, and the sun’s rotation period of 25.4 Earth days produce the sun’s magnetic fields. However, there are many notable differences.

These granules on the sun are convection cells.

The sun is over 12,000 times larger than the Earth, which means that its magnetic fields are larger as well. It’s so large, it extends past the orbit of Pluto. However, it isn’t a solid object, like Earth. The sun’s material is mostly plasma, which works like a gas; like Jupiter. This means that the sun experiences differential rotation, where the equator rotates faster than the poles. On the sun, its Equator rotates every 25.4 days, but its poles rotate every 29 days. This video will demonstrate what that does to the sun.
When the sun rotates, the equator stretchs the magnetic field lines towards the sun’s direction of rotation, and it will keep stretching it until they snap like rubber bands. When they snap, they release the energy in the magnetic field and the magnetic field lines pop out of the sun. These magnetic field lines cause the charged particles from the surface to become trapped along the magnetic field lines. Those trapped particles are called prominences. In addition, Sunspots are formed where the magnetic field lines poke out and in, when the charged particles are lifted from its surface. That is why sunspots are common during periods of high solar activity, like the Solar Maximum.

Eventually, the magnetic field lines will reconnect with each other, and release a lot of energy, leading to large solar flares, and coronal mass ejections. At the same time, the polarity of the magnetic fields will reverse. When the flip is complete, the sun’s magnetic field will drop to zero, reappear in its reversed polarity, and start the process again. This process occurs every 11 years and after each cycle, the poles reverse.

Today, there is evidence that the Sun’s magnetic field is in the process of flipping after a chaotic solar maximum. Once the flip is complete, the process starts again.

Here is a video that talks about the sun and its solar cycle by NASA:

 

 

Thank you for reading! For my next topic, I want to hear from you. What do you want me to write about next time? You can respond by going to the contact form at: http://www.jolyastronomy.com/contact-me/  Thank You.

WORKS CITED

Coursera Lecture 6.6

http://www.windows2universe.org/sun/activity/sun_mag_field_rotate_tangle.html

http://www.windows2universe.org/sun/solar_activity.html

http://www.windows2universe.org/sun/activity/sunspot_cycle.html

http://www.windows2universe.org/sun/activity/solar_cycle.html

http://www.windows2universe.org/sun/sun_magnetic_field.html

http://www.windows2universe.org/sun/atmosphere/solar_flares.html

http://www.usatoday.com/story/news/nation-now/2014/01/06/sun-magnetic-field-polarity-reverse/4306845/

http://news.nationalgeographic.com/news/2013/08/130807-sun-magnetic-field-reversal-space-weather/

http://www.space.com/23551-sun-magnetic-field-flip-video.html

 

IMAGES USED

 

VIDEO USED

The Tetrad of Lunar Eclipses

Taking a break from magnetic fields, I wanted to talk about a very rare event that started taking place on Tuesday, April 15, 2014. The first of four lunar eclipses took place that night. This is a rare event as this tetrad of eclipses will occur six months apart from each other; the first one on April 15, 2014, the next on October 8, 2014, the third on April 4, 2015, and the last one on September 28, 2015. All of the eclipses will be visible from North America.

All these eclipses will be total eclipses. That is when the entire moon is completely engulfed in the Earth’s shadow. This is the most spectacular eclipse as the whole moon turns a bright red, reminiscent of a sunset. This is also called the blood moon. The next kind of eclipse is a partial eclipse. This is when the Moon crosses into the Earth’s umbra, but is not completely consumed by it. The last and least noticeable is a prenumbral eclipse. The Moon enters the Earth’s prenumbra, but doesn’t cross into the umbra. This is a very subtle eclipse. The most one will notice is a drop in brightness. Luckily for us, all the eclipses during this tetrad of eclipses will make the moon glow red. But why red?

That is because, when the sun obstructs the Earth, most of the light is being blocked, but the light hitting the atmosphere is bending towards the Moon. While that occurs, the atmosphere is also scattering the shorter wavelengths of the spectrum into the atmosphere, leaving behind the red wavelength, which is the longest and the least likely to scatter. This is why the moon looks red during a lunar eclipse, and this is why sunsets are red.

Unlike a solar eclipse, this eclipse is safe to view without any eye protection, and it is visible across a whole continent, whereas solar eclipses are visible in a thin, 250 km region during its path. That will be another post…

Thank You for reading.

 

WORKS CITED

http://www.cbc.ca/news/technology/total-lunar-eclipse-last-night-was-the-1st-of-4-1.2610637

http://science.nasa.gov/science-news/science-at-nasa/2014/27mar_tetrad/

http://www.universetoday.com/19969/red-moon/

http://news.nationalgeographic.com/news/2014/04/140410-lunar-eclipse-blood-moon-space-viewing-guide/

 

 

WORKS CONSULTED

http://www.answersingenesis.org/articles/2013/07/12/lunar-eclipses-cause-blood-moons

http://americanlivewire.com/2014-04-14-why-does-the-moon-change-colors/

 

Magnetic Fields: On Other Planets

Hi everybody,

We ended the previous post with mentioning that Earth is not the only planet with a magnetic field. All the planets, with the exception of Venus and Mars, produce magnetic fields.

Mercury, the closest planet to the sun, and one of the smallest planets in the solar system, has a magnetic field. It is thought that Mercury’s large core is doing the geodynamo process to produce the magnetic field, however, it has not been confirmed yet, and there are other ideas floating around. Mercury’s magnetic fields are only 1% the strength of the Earth’s, however, it is strong enough to repel solar flares. Currently, the MESSENGER probe orbiting mercury is working to learn more about Mercury’s magnetic field using a variety of instruments. Of the inner planets, Venus and Mars are the only planets that do not produce magnetic fields.

Mercury’s magnetic fields with MESSENGER’s orbit.

Venus is similar to Earth in some ways; however, it doesn’t produce a magnetic field. While our knowledge of Venus is incomplete, there are a few conjectures as to why that is. The first one is that the core has solidified and there is no convective outer core to convect any conductive fluids, and thus no magnetic field could be produced. Another conjecture is that, since the planet went through a major resurfacing event, the crust has effectively sealed the core in, and the core became heated to a uniform temperature which doesn’t promote convection. Another theory is that in addition to the lack of convection, Venus is also rotating so slowly (243 days/Venus Day)- it isn’t moving fast enough to produce any magnetic fields. Since Venus doesn’t have a magnetic field, and any solar flare will interact with the ionosphere directly, the ionosphere will slow the flare down and redirect the flow of charged particles. Since the atmosphere is dense, and Venus’ winds are intense, the ionosphere will prevent the charged particles from reaching its surface. Despite all we have learned about Venus, these theories are still conjecture, and it will be difficult to find answers due to Venus’ harsh conditions. We have more complete information about Mars, however.

Venus’, Earth’s, and Mars’ interactions with Solar Flares

 

Mars is different, in many ways, from Venus and Earth, but like Venus, it doesn’t have a magnetic field. It has an ionosphere present, but the atmosphere is quite weak; therefore, the planet isn’t protected by any solar flares. Its mantle is presumed to be inactive, and its core is already small, having never accumulated enough iron, therefore convection in the core stopped and the magnetic field ceased to exist. However, there are traces of a magnetic field in Mars’ past found frozen into the rocks on Mars that are over 4 billion years old. There is a theory that Mars’ magnetic field was destroyed when a large asteroid impact interrupted the convective process of Mars, which stopped the production of the magnetic field. It is under debate, though, as some might consider that Mars’ geodynamo process ended when the core cooled enough to stop the convection process on its own. It makes sense since Mars is smaller, and lighter. It would take a shorter amount of time to cool down than Earth would. Since the magnetic field ceases to exist, the solar flares were able to strip away Mars’ outer atmosphere and kill any life on Mars. Unlike some inner planets, all the outer planets have magnetic fields.

Outer Planets

 

The magnetic fields of the outer planets

All the gas giants have magnetic fields, with Jupiter having the strongest magnetic fields of them all. The magnetic field works much like Earth’s, with the geodynamo process originating from its metallic hydrogen outer core and its fast rotation period. However, it is 100 times larger and extends 20,000 greater than Earth’s magnetic field. Some say that the tail of the magnetic field extends as far as the orbit of Saturn. It’s so big that it begins to repel a solar flare 3 million kilometres away from Jupiter. However, because of its larger distance from the sun, the intensity of the solar wind is 4% that of the Earth’s. This means, less effort is needed to repel it. Much like Earth, Jupiter has a set of radiation belts that trap any charged particles heading towards it. It is 1000 times stronger than Earth’s radiation belts. In addition, the magnetic fields also receive particles from its innermost moon, Io. The sulphur, and oxygen Io emits from its volcanoes create a ring of gas that interacts with the magnetic field and collects it, which creates a gas torus. Spacecraft visiting Jupiter will need to overcome the intense radiation present in its magnetic fields.

Saturn’s magnetic field is the second largest in the whole solar system. It works a lot like Jupiter’s, but it is only half of its strength. This is because; the metallic hydrogen outer core that conducts the geodynamo process is smaller than Jupiter’s. When the magnetic fields interact with the solar flare, they interact from 20 Saturn radii away, and its tail extend much farther than that. The magnetosphere has many taurii, originating from Enceladus, and Titan. Enceladus ejects a large amount of water vapour into space. The water vapour ionizes and rotates with the magnetic field. Eventually, it escapes through the magnetotail. Titan has a large amount of Nitrogen ion plasma and is released into Saturn’s inner magnetic fields. There might be other sources inside Saturn’s rings, inner moons, or the upper atmosphere. When the solar flare hits Saturn, much like Earth, aurorae are formed on Saturn spanning the whole spectrum of light. Spacecraft visiting here have to overcome its intense radiation as well here.

Uranus’ magnetic field is 0.1 times that of Saturn. Before Voyager 2 arrived there, no experiments took place there of its magnetic fields. They expected a magnetic field similar to the ones they knew, such as Earth’s. However, measurements revealed two major differences: Uranus’ magnetic fields aren’t in line with the center of the planet, and that it is tilted 59 degrees from the rotational axis. This means the magnetic field produced is asymmetric across the whole planet. One theory to suggest why it occurs is that, unlike the other planets where the magnetic fields are generated in their cores, Uranus’ magnetic fields is formed closer to the surface, such as in a water-ammonia ocean, where convective movement could take place. Since the magnetic axis is highly inclined with respect to the rotational axis, the magnetotail would be wound into a corkscrew shape. In addition, the radiation belts are mostly made of Hydrogen ions, which suggest that there are no taurii present from any of its moons. However, despite its differences, its magnetic fields are similar to Saturn’s magnetic fields.

Uranus and Neptune’s magnetic fields

Neptune is very similar to Uranus and is the only other planet to have similar magnetic fields to Uranus. Its magnetic field is titled relative to the rotational axis by 47 degrees and offset by 0.55 Neptune Radii. Comparing it to Uranus, it is likely that there is convective flow in a shell of conductive liquids that drives the geodynamo process. When the solar wind interact with Neptune’s magnetic fields, it starts to repel it at 34.9 Neptune Radii, and the magnetotail extends at least 72 Neptune radii, and probably farther. In addition, it is found that there are aurorae on Neptune, but much weaker than those of Earth. These results were verified by Voyager 2’s visit to the two ice giants.

 

However, one more celestial object has a magnetic field, and during an 11 year period, it produces noticeable black spots on it. Stay Tuned for the final segment.

 

WORKS CITED

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magearth.html

Coursera Lecture – Week 5.8

http://www.universetoday.com/27005/earths-magnetic-field/

http://genesismission.jpl.nasa.gov/science/module4_solarmax/solarmax_planets.html

https://www.windows2universe.org/physical_science/magnetism/planetary_magnetism.html

http://en.wikipedia.org/wiki/Mercury%27s_magnetic_field

http://messenger.jhuapl.edu/why_mercury/q3.html

http://image.gsfc.nasa.gov/poetry/venus/V3.html

http://phys.org/news141573374.html

news.sciencemag.org/2009/04/did-marss-magnetic-field-die-whimper-or-bang

http://www.redorbit.com/news/space/1112773528/solar-wind-makes-venus-act-like-a-comet-013013/

http://en.wikipedia.org/wiki/Magnetosphere_of_Saturn

http://zebu.uoregon.edu/disted/ph121/js20.html

http://en.wikipedia.org/wiki/Magnetosphere_of_Jupiter

http://en.wikipedia.org/wiki/Gas_torus

http://lasp.colorado.edu/education/outerplanets/giantplanets_magnetospheres.php#jupiter

http://voyager.jpl.nasa.gov/science/uranus_magnetosphere.html

http://en.wikipedia.org/wiki/Neptune

http://www.windows2universe.org/neptune/magnetosphere/N_mag_generation.html

http://www.windows2universe.org/neptune/upper_atmosphere.html

 

 

WORKS CONSULTED

http://www.universetoday.com/13943/mercury/

https://www.windows2universe.org/physical_science/magnetism/generating_magnetism.html

http://lasp.colorado.edu/education/outerplanets/giantplanets_magnetospheres.php

http://www-ssc.igpp.ucla.edu/personnel/russell/papers/venus_mag/

http://www.sciencedaily.com/releases/2012/03/120305173701.htm

http://nessc.unh.edu/savannah/Luhmann.pdf

http://www.britannica.com/EBchecked/topic/525169/Saturn/54281/The-magnetic-field-and-magnetosphere

http://www-ssc.igpp.ucla.edu/personnel/russell/papers/sat_mag.html

http://www-ssc.igpp.ucla.edu/personnel/russell/papers/nep_mag.html

http://www-ssc.igpp.ucla.edu/personnel/russell/papers/ura_mag.html

 

IMAGES USED

http://i.space.com/images/i/000/033/427/i02/venus-earth-mars-interacting-solar-wind.jpg?1381338788

Magnetic Fields: Its Purpose on Earth

Hi everybody,

If you have used a compass, then you have used one of Earth’s key features to find your way. That feature is Earth’s magnetic field.

Earth is a giant magnet. This is because the core generates the magnetic field using the process called the geodynamo. The geodynamo process works like this: the outer core is full of conductive metals that is heated from below by the inner core. This drives the convection. The convection in the outer core is maintained by the heat in the inner core, and chemical differentiation. With help by the rotation of the Earth, this drives convection, and creates an instability that forms the magnetic field, and this process aligns the magnetic field to the rotational axis of the planet.

The Geodynamo Process

Magnetic fields are essential for life on Earth. That is because the magnetic field protects the planet from cosmic rays and charged particles from solar flares. When the charged particles hit the magnetic field, they become trapped and slide along the field lines moving towards the poles. The strongest areas of the magnetic field are near the poles, and if the particles are not strong enough, then they are repelled and they bounce back and forth along the field lines and that creates the Van Allen Radiation Belts. There, the magnetic field has trapped the charged particles to prevent them from reaching the atmosphere. If we didn’t have the magnetic field protecting the Earth, then the atmosphere would become stripped of its atoms and the radiation from the solar wind would irradiate all life on Earth.

Van Allen Radiation Belts

However, the charged particles also interact with the magnetic fields. The motions of charged particles in circles form magnetic fields of their own. As a result, when both magnetic fields collide with each other, Earth’s magnetic field absorbs the momentum of the charged particles, and that pushes Earth’s magnetic field back. The Earth wants to make an even magnetic field, but the Sun is pushing the magnetic fields away from the sun. It’s not an even bombardment, due to the variations in solar output.

There are times when the solar wind is strong enough to overcome the magnetic field. The charged particle slides along the field into the poles, and when it is strong enough, it enters the atmosphere near the Earth’s poles, and ionizes the atmosphere. This leads to a beautiful sight called the Aurora Borealis/Australis.

Auroras over the landscape

Earth is not the only planet with a magnetic field though.

Stay tuned for my next post.

 

WORK CITED

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magearth.html

Coursera Lecture – Week 5.8

http://www.universetoday.com/27005/earths-magnetic-field/

 

 

IMAGES USED

http://i.huffpost.com/gen/607838/thumbs/o-TOMMY-ELIASSEN-AURORA-570.jpg?1

 

Movement of Planet Earth

Hi Everybody,

Did you know that you would weigh 0.3% more if the Earth was standing still? Probably not, but it doesn’t matter because the Earth does spin. If you look at something on Earth, like a tree, or a house, it seems stationary. However, those objects, like everything else on Earth, are in constant motion. This is because the Earth, and everything on Earth, rotates every 23 hours, 56 minutes, and 4 seconds.

Hold On! We know that a day is 24 hours. How can approximately 4 minutes be missing from a day? Before we answer that, what is this day that has 23 hours, 56 minutes, and 4 seconds? This is called the sidereal day. Sidereal days have 24 sidereal hours which corresponds to a 15 degree movement of the stars per hour with respect to the Earth’s rotation. Basically, a sidereal day is a day with respect to the stars’ fixed positions. For example, if you take the star Deneb, and track its motion for a whole day, it would’ve made a complete 360 rotation after a sidereal day. This has been used since antiquity to determine time. However, why is it that we have 24 hour days, and not sidereal days?

As the Earth rotates, and sidereal days pass, it also moves along its orbit around the sun. If the Sun and Earth were aligned at noon, and a sidereal day passed, the Earth would be out of alignment with the sun. It would need an extra four minutes of rotation to realign it to the sun and reach noon. This is a solar day, and a solar day has 24 hours.

Sidereal vs Solar Day

Sidereal vs Solar Day

Another way to think about it is, as the Sun moves along the celestial sphere(the sky) from east to west, it trails by 4 RA minutes every day. The reason that we have these two standards of time is because, one clock runs 4 minutes fast. If September 21 is our start point, where midnight is 0 hr, 6 months later, on March 21, midnight is 12 hr, or noon. It creates an imbalance in time. It is simpler to have a 24 hr day where noon is noon every day of the year. It is easier to plan your daily events without taking into account the imbalance of time. It’s clear that the orbit of Earth has a profound impact on our day in many ways.

Earth orbits around the sun for one year or 365.25 days. During that orbit, it travels a total of 940 million km in space. Almost all orbits are not circular, but are ellipses. That is true for Earth as well. There are two points in any orbit called: Periapsis, and Apoapsis. (Each body has a different name for their orbital points, e.g. for Sun, Perihelion, and Aphelion). Earth has a perihelion of 147,098,290 km (0.98329134 AU) and an aphelion of 152,098,232 km (1.01671388 AU). On average, Earth has a semi-major axis of 149,598,261 km, which is 1.00000261 AU. This means its orbital eccentricity is 0.01671123, where an eccentricity of 0 is a perfect circle, anything between 0 and 1 represents an elliptical orbit, and anything 1 or greater is a parabolic orbit, or a hyperbolic orbit, respectively. While the orbit is slightly eccentric, this eccentricity doesn’t have much effect on the climate of Earth. It is seen in the fact that when the Earth is at aphelion (farthest point from the sun) in July, the Northern Hemisphere experiences summer, and when the Earth is at perihelion (the closest point to the sun), in January, the Northern Hemisphere experiences winter. The reverse is true for the southern hemisphere. The main reason why there is winter and summer is because of the tilt of the Earth.

During the year, there are four major events that occur: The Winter and Summer Solstices, and the Autumnal and Vernal Equinox. Imagine two lines on Earth, the equator, and the ecliptic. The ecliptic is 23.5 degrees tilted with respect to the equator. This simulation will help you imagine both lines. The equinox occurs when the sun reaches the point where the ecliptic and the equator intersect. At this time, both the Northern and Southern Hemispheres have an equally long day and night. The Solstices occur when the sun, on the ecliptic, is at the highest point away from the equator. At that point, it is angled towards one hemisphere and away from the other. For example, An observer in Canada, on June 21, will see the sun at its highest inclination, whereas an observer in Chile will see it at its lowest inclination. This means that the hemisphere that is tilted towards the sun will experience longer days and shorter nights, whereas the other hemisphere will experience shorter days and longer nights. Click here to see the seasons in action. This process repeats every 365.25 days, but not quite.

While an Earth year is 365.25 days, the definition of a year has been refined over the centuries. Earth has a sidereal year of 365.2564 days. This is the time it takes for the Earth to return to the same position with respect to the sun. For example, starting September 21, 1 sidereal year later, it will be in the same position. Our modern calendar year is 365 days. This is problematic because as these additional 1/4 days accumulate, it will add up and cause problems. Every four years you are off by day. After 720 years, you have 180 extra days, and that means January is summer in Northern Hemisphere, which is a problem if you are keeping time. Luckily, Julius Caesar was able to figure that out and is able to legislate the leap year. He has introduced the leap year, and as a result, we never drift more than a day. However, that is not enough.

Our calendar doesn’t drift more than a day, but it still doesn’t match the seasons. The calendar does take into account the length of the year, and the tilt of the Earth, but it doesn’t take into account the precession of the axial tilt. This precession causes the Earth’s tilt to rotate westward ever so slightly. This means that Polaris won’t be our north star forever. This precession completes its rotation every 26,000 years. While the effect is quite insignificant, it does affect our calendar, because year after year, the precession shortens the time between seasons. This results in the tropical year, which has 365.2422 days, which is slightly shorter than a sidereal year. As a result, to account for the axial precession, Pope Gregory XIII, in the 16th century, corrected for the difference between the sidereal year and tropical year by removing the leap years of centuries not divisible by 400. For example, years 1700, 1800, 1900 do not have leap years, but 1600, 2000 do have a leap year. This correction, and the tropical year is what the Gregorian calendar is based on, and this calendar allows our timekeeping to remain consistent for many years to come.

The path of Earth’s axial precession

What the precession looks like.

So what did we learn today? We learned a lot about the movement of Earth. We learned about what is a sidereal day, and what makes it different from a solar day. We learned about the orbit of Earth and what occurs during that orbit. We also learned about what makes our calendar the way it is today. I hope you all found this interesting.

Stay tuned for more blog posts…

WORKS CITED

http://www.universetoday.com/26623/how-fast-does-the-earth-rotate/

http://astro.unl.edu/classaction/animations/coordsmotion/eclipticsimulator.html

WORKS CONSULTED

Coursera Lecture – Week 1.4 – 1.7, 1.10

http://en.wikipedia.org/wiki/Earth%27s_rotation#True_solar_day

http://en.wikipedia.org/wiki/Earth%27s_orbit

IMAGES USED

VIDEOS USED

http://www.youtube.com/watch?v=FmCJqykN2J0 – NASAEarthObservatory

About Our Planet Earth

Hi everybody,

It’s an amazing thing to look into the sky and look at the other worlds that exist. However, it all starts on the planet that we know the most about: the planet Earth.

Earth from Apollo 8

Earth from Apollo 8

Earth is a rocky planet located in the Solar System. It is the third planet from the sun. It is the most dense planet in the solar system, and the only planet to support life. It has one natural satellite, The Moon, and many other artificial satellites sent up by humans. It has a mass of 5.97219E24 kg, and orbits 1 AU or 149,597,870,700 m from the Sun.

Believe it or not, Earth is the only object with a name that doesn’t originate from Greek/Roman mythological figures. If it were, it could’ve been called Tellus (not Telus!) or Gaia, using Roman or Greek names respectively.

Planet Formation

Earth was formed during the formation of the Solar System. It is 4.5 billion years old. During its formation it accreted many smaller asteroids and planetesimals to form a protoplanet. In Earth’s early history, it is conjectured that a mars-sized protoplanet collided with the Earth and released all kinds of silicates into orbit which accreted to form the Moon. When the moon formed, it was really close to the Earth. As the system orbited the Sun, the Earth and Moon exchanged angular momentum, which slowed Earth’s rotation period and pushed the moon’s orbit outwards. This resulted in today’s Earth and Moon system.

Formation of a Moon

Atmosphere of Earth with Moon in the background

The planet’s atmosphere is 77% Nitrogen (N2), and 21% Oxygen (O2), with traces of other gases. Earth has a lot of free N2 in the atmosphere because it couldn’t form rocks with Silicon, Calcium, Sodium, and other elements to form rock, unlike O2 which formed rocks with these elements. In addition, N2 is quite stable, even under the influence of solar radiation. It has built up over time, unlike O2, which is consistently being recycled in Earth. In the past, the atmosphere, most likely, had a lot more Carbon Dioxide (CO2) than now. This was due to Earth’s formation. However, when water was introduced in the atmosphere, the raindrops was able to lock the CO2 in carbonate rocks, absorb inside the ocean, and eventually was used in photosynthesis. Now, there are traces of CO2 and it is increasing due to industrial processes, however, these traces (before and after human pollution) help trap heat to keep the climate in check using the greenhouse effect. It is also that same reason why Venus is the hottest place in the Solar System.

Earth’s Interior

The Earth has many layers. Earth has a crust, upper mantle, lower mantle, an outer core and an inner core. We learned about these layers by using sound waves. As one goes downards to the core, it gets hotter and denser. The reason the core is so hot is because the core generates heat using radioactive decay 80% of the time, and Kelvin-Helmholtz processes 20% of the time. The heat is transferred to the top by using circulation cells in the mantle. The core and outer core are made up of heavier elements, like iron, and nickel, whereas the mantle and crust is made up of lighter silicate materials. This is because, when Earth, during its formation, accreted enough mass, the heat of collisions and radioactivity causes the Earth to melt, and then the process of chemical differentiation takes place. The heavier elements sink towards the centre, whereas the lighter elements float to the top. This occurs when planetesimals becomes protoplanets. Today, due to plate tectonics, erosion, and other processes, most of Earth’s geologic history has been erased.

Earth

As far as we are concerned, Earth is the only planet that can support life. It is predicted that Earth’s biosphere started to form 3.5 billion years ago. Once life moved into land, the biosphere became divided into different biomes. The type of biome depends on its latitude, height from sea level, and humidity of area. For example, humid lowlands at equatorial latitudes produce very diverse biomes whereas extreme latitude, high height, and extreme humidity produce different biomes. In Earth’s history, there have been five major extinction periods, with the most recent occurring 65 million years ago, killing off all the dinosaurs. Eventually, the mammals diversified and a certain ape-like species of animal evolved to stand upright, and it eventually led to the evolution of humanity. Today, humans have evolved greatly with various innovations and technological advancements. In addition, the search for life beyond our solar system is increasing at a rapid pace. Astronomers, scientists, and looking at other stars and finding exoplanets that have the potential to support life.

Stay tuned for more information about our planet Earth.

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