Callisto

Figure obtained from Astronomy Picture of the Day

           This is a picture of Callisto which is one of the Galilean satellites that orbits around Jupiter. This picture was posted on Astronomy picture of the day on July 31^st, 2001. It is the third largest moon in the Solar System and is close to the size of Mercury. Callisto is the Galilean moon that is furthest away from Jupiter and is thought to have a large body of water under the icy surface. It is also thought to be one of the satellites in the solar system where life could form. I will discuss the evidence that shows that this is possible. There are three factors that need to be present in order for life to evolve. One is that there needs to be source of elements and molecules from which to build living organisms. Second is the need for a source of energy for metabolism and growth and the last is the need for a liquid medium for transporting the molecules of life.  The outer three Galilean moons are thought to be areas of interest for finding life. As mentioned earlier there is evidence that there are vast bodies of water that is under the ice.  Callisto itself does not have a strong magnetic field but it does have an induced magnetic field which is evidence of the presence of salty water under the surface. Another factor is the energy that is needed. It is thought that the warmth and energy needed from can be formed by radioactive decay that is occurring on the satellite. Of the two other Galilean moons Callisto has the least amount of energy available. It is thought that to would not have the energy needed to create and sustain life. Because of this Europa and Ganymede is thought to have a better opportunity for life.  

Jupiter and Venus

Figure Obtained from Astronomy Picture of the Day

               This picture was obtained from Astronomy Picture of the Day, it was posted on March 18^th 2012.  The two very bright objects that are shown in the image are Venus and Jupiter. Venus is known as the sister planet to Earth. It is closer to the sun then Earth but it is very close in size and composition. Venus is one of the four rocky planets that are located in our solar system. It appears to be very bright in the night sky this time of year because of its proximity to Earth as well as the very thick clouds that blanket the whole planet. As mentioned above the other bright object is Jupiter. Jupiter is the largest planet in our solar system and has a large number of moons. Four of these moons are very large one being larger than the planet Mercury. These moons are known as the Galilean moons. I was able to observe Jupiter last week when it was higher in the sky and at dusk and from a telescope one could see the four moons. Jupiter is not like Earth and Venus in composition and in size. It is one of the four outer planets that are normally called the Gas Giants. This is because they have very large layers of gas and supercritical components and a very dense and small core. The core is more massive than Earth but it is smaller is size.  It is interesting that no matter where you are on Earth at this time of year on a clear night everyone on Earth can see these two objects with the naked eye. Anyone on the planet with a clear western horizon at sunset could see them. If you missed seeing these objects in the night sky the APOD site says that you will get another chance next may to see these objects close together.   

The Active Sun

Figure obtained from: Astronomy Picture of the Day

           The picture above was taken from astronomy picture of the day. It was posted on March 15^th 2012. The pictures are of the gamma-ray sky and some recent activity that has occurred very close to home.  When one takes a picture of the sky in the gamma ray region of the electromagnetic spectrum usually the most exotic and energetic of astrophysical environments can be observed.  An example would be like the active galaxies such as quasars. These are very small galaxies that look like stars and they are powered by supermassive black holes. Another example that is shown above would be a dense pulsar. A pulsar is a rapidly rotation neutron star that emits regular radio waves at rates around one thousand pulses per second.  One can see that in the bottom picture the Sun lights up part of the gamma ray sky. This is due to a massive solar flare that occurred on March 7^th. This is just one of the recent solar eruptions that have occurred.  This solar flare had energies up to 1 billion times the energy of visible light photons. This is amazing because on most other days the Sun would not show up in these gamma ray images because they do not have the massive amounts of energy.  The Sun will most likely shine again in the gamma ray sky in the not so distinct future because we are approaching a sunspot maximum. This is the period of time when the Sun will increase in activity. This increase in activity may have effects on Earth. One of the main effects would be auroras. As well the charged particles that are coming off of the Sun during this active time may disrupt radio and electrical transmissions. It will be neat to follow this increase in the Sun’s activity! 

Holy Moon!

Figure Obtained from Astronomy Picture of the Day

          The picture above was obtained from Astronomy Picture of the Day. The picture was posted on March 10^th 2012.  I chose to write about this picture because I was astonished by the size of the moon in this picture. It was taken on March 7^th in California; the building that is in the forefront of the picture is the Lick Observatory that is perched on a mountains 4200 foot summit. One notices many features of the moon in this picture. One of the main features is the color of the moon, which is not the silver color that we are used to seeing. This is caused because the moon reflects the Sun’s light. This is because the moon does not produce its own light and thus reflects the light from the sun. When the sun is just rising like in the picture above the sunlight is filtered by the atmosphere. This causes the red light that has longer wavelengths to move through the atmosphere hence giving the moon its orange glow. The atmosphere also gives the moons outline its ragged rim.  This has to do with atmospheric refraction that is occurring.  One can also notice a number of the moon’s lunar maria. These are the dark a regions of the moon that is shown in the picture above, these maria make up the “Man in the Moon”. The reason that the maria are different from the rest of the surface is because they are composed (basaltic) of a different material. They are basaltic plains that were formed by ancient lava flows. They are less reflective than the light regions “lunar highlands” as a result of their iron rich composition.  The maria cover about 16 percent of the lunar surface. From this dramatic picture one can see many aspect of the moon that are less distinguishable if taken when it appears further away. 

Spiral Galaxy ESO 510-13

Figure Obtained from: Astronomy Picture of the Day

          The picture above was obtained but Astronomy Picture of the Day. It was posted on March 4^th 2012.  This shows a spiral galaxy edge on and it has a distinctive warped appearance. A galaxy is a collection of millions, billions, or even trillions of stars gas and dust that are gravitational bound. The material rotates around a center.  The center of the galaxy is the location of a supermassive black hole. Like our Milky Way Galaxy this galaxy is spiral. As well from the edge on view one can see the dimensions of the galaxy. The length of the galaxy is enormous compared to the thickness of the galaxy.  The dark bands that are shown in the figure above are where the gas and dust as well as some stars are located.  As well there is a large part of the galaxy that we are not able to see. This is the large amount of dark matter that is located at the edge of the visible galaxy and it expands out to large distances.  This dark matter is what allows deviations in Kepler’s third law. If the orbit of the stars around the galactic center follows Kepler’s third law then the further the star is away from the center the slower it orbits of the stars around the center are. However, this is not true for galaxies. The speed of rotation increases up until a certain point and then it stays relatively constant as you move away from the galactic centers. This change is caused by the sheer amount of dark matter that surrounds the galaxy. But why is this galaxy warped? It is also important to note that the disks of galaxies are thin and flat but not solid. It is thought that some wraps result from interactions or collisions between galaxies.  It however, is not completely known, and it is also thought that our galaxy is thought to have a small warp.

Figure Obtained from: APOD

This picture was posted on Astronomy Picture of the Day on February 22, 2012. When I first looking at this picture I knew that it was Earth but I thought much like others that the large rock was not from Earth. It stucks out like a sore thumb and does not look like it belongs. One can see that most of the landscape in the forefront of the picture looks to be very flat and have a scaly appearance. This appearance is due to mud flowing, then drying. As it dries the ground cracks and it gives it the scaly appearance.  This rock does not look like the rest. One can however; see a path that looks like a drag mark that fades into the background. As I looked at the caption that went along with the picture I was surprised to find out that there was a natural and earthly explanation for the position of the rock. It can be explained quite simply actually. The reason the 300 kilogram rock is able to move out to its current position is caused high winds blow the rock to its position. This would not be able to occur in the normal environment of the Racetrack Playa.  But it does occur after a rain. This allows the high winds to push even this heavy stone across the lakebed. The rain causes the lakebed to become slick and slippery and this coupled with the wind are the reason for the position of this rock.  This rock that moves like this is termed a sailing stone. Even though at first glance it looks like this may be a piece of space debris it turns out to be a rock from earth that went on a slip and slide. This shows that one has to be objective when looking at a picture and not to jump to conclusions. 

Black Hole

Picture Obtained from Astronomy Picture of the Day

          This picture was obtained from astronomy picture of the day. It was from February 24^th 2004. It shows that a black hole is able to rip up a star. Black holes are stellar remnants that are above three solar masses. A black hole is formed because the neutron degeneracy pressure that would keep a neutron star a star is overcome and therefore, the star is able to collapse and become very dense. A black hole is composed of a singularity where all the mass is held and then there is the event horizon which is the boundary of the black hole. Once an object passes the event horizon it cannot escape. The black hole has so much gravity that an object has to excess the speed of light. This means that light cannot escape it.  If there is material near a black hole it can be pulled into the hole. In this picture the giant black hole  pulls on the front of a closely passing star much more strongly than the back. This is explained by general relativity.  This strong tidal force would stretch out a star and likely cause some of the star’s gasses to fall into the black hole.  This infalling gas emits x-rays when the gases are heated when they are compressed from falling into the hole. The picture above is an artist’s illustration of the sequence of destruction of the star by the black hole. When the star is destroyed most of the stellar remains would be flung out into the galaxy. This aspect of the destruction does not make sense to me. I would think that the material would spiral into the black home because the star is close enough to the hole and the gravity is large enough to rip the star apart.  However, these event are rare and occur only once every  10000 years the black holes are located at the center of galaxies.  Even though I am not sure about all the processes that are going on but I know that black holes are very powerful aspects of the universe.