The year 2009 is the international year of astronomy; it marks 400 years since Galileo used the telescope to first look up at space. As part of the celebration NASA and other astronomical societies having been doing things to celebrate.  NASA is doing its part this month by allowing the public to be the astronomers. They have put the public in control of the Hubble Space Telescope. NASA has picked six astronomical objects and is allowing the public to vote on which object Hubble will view and collect data on next. I decided to go over each of the six objects and describe what they are and why they might be of interest.

The first object is a star-forming region called NGC 6334 also known as the Cat’s Paw Nebula or the Bear Claw Nebula. It is located in the Scorpius constellation that is located in the southern hemisphere near the center of the galaxy.  It is located about 5,500 light years away. It glows with a deep red color that originates from a large amount of ionized hydrogen in the area. The nebula is usually obscured by large amounts of gas and dust sometimes making it difficult to observe from ground based telescopes.  The region is a very active star-forming region, which is the reason it is considered for observation. Observing these star forming regions tells us a lot about the birth and evolution of stars, and the interaction of a large number of young stars in close proximity to each other.

The second contestant is the planetary nebula NGC 6072, which is also located in the constellation Scorpius. There is not much information available on this object and it has not been viewed very often.  It is a remnant of a dead low mass star; a white dwarf with an envelope of gas and molecules surrounding it that were puffed off layers of the star as it was dying. Observing planetary nebulas is always useful, it gives us information about stars after they die and how the elements given off interacts with surrounding gas and dust. They also usually make for very pretty pictures.

The third object is planetary nebula NGC 40, otherwise known as the Bow-Tie Nebula. It is located about 3,500 light years form Earth in the constellation Cepheus. It is also composed of hot gas surrounding a dying/dead star. The white dwarf left behind radiates at about 50,000 degrees C and the gas envelope at about 30,000 degrees C.  This nebula has been imaged more than the other nebula, perhaps making it a less attractive candidate.

The fourth object in the contest is the spiral galaxy NGC 5172.  It is located at a distance of about 57 mega parsecs or about 150 million light years. It is a spiral type Sbc. IT has been a host to several well-documented supernovae. From what we can tell it is very similar in size and shape to our own Milky Way galaxy, which is the reason it may be a good candidate for study. Since we can not get an outside looking in view of our own galaxy studying ones similar to our own tell us information we could not otherwise get.

The next possible object is the edge on galaxy known as NGC 4289. It is located in the Virgo Constellation about 50 million light years away.  It is also a spiral galaxy but instead of being viewed face on it is seen completely edge on.  There are advantages to looking at the same types of things from different views; especially with astronomy. When looking at things so far away with things obstructing your view, light traveling so far, being bent around objects being able to see galaxies edge on can help with verifying measurements of brightness, velocity and other variables.

The last option for an object to choose is Arp 274, or NGC 5679, and is actually two (possibly three) galaxies interacting with each other.  It is also located in the Virgo constellation. Interacting galaxies are treasure-troves of data. By studying them we can information on formation and evolution or galaxies. We get information on how these interactions affect star formation, surrounding galaxies, central black holes, and more. I think this is a great candidate for further study. 

So those are the six objects open for voting. I encourage any readers to go check out NASA’s site and vote. I personally think this was a great idea on NASA’s part. Hubble has always been very popular and a great tool for creating public interest in astronomy, which can at times be hard to do.  I think it’s smart to give the general people the option to pick what they think is interesting and what they want to know more about. I encourage anything that the industry wants to do to try and rose public support, especially in times when funding is hard to come by NASA needs to keep the public in its corners.  I’m excited to see who the winner will be. 

The Apollo missions of the 1970’s can be credited with many great discoveries–the most notable of which, were the six missions that sent twelve astronauts to the moon.  During these manned missions to the Moon, rock samples were collected and returned to the Earth.  The analysis of these samples led to the current hypothesis of lunar formation.  This hypothesis suggests that the Moon was formed by a catastrophic collision between Earth and Mars-sized planetesimal.  After this collision, the Moon would have been covered by a thick blanket of magma, which cooled to form a crust much different from the Earth’s crust.   Then 3.8 billion years ago, during the late heavy bombardment, the Moon’s surface was pounded by meteor impacts, leaving the surface deformed and heavily cratered.  New data gathered by the Japanese mission, SELENA, may offer new insights into the formation of the moon.

SELENA focused on the differences between the near and far side of the moon, such as: compositional, gravitational, topographical, and tectonic differences.   However, it is difficult for spacecrafts to relay information from the far side of the Moon, due to the fact that the Moon is tidally locked to the Earth.  SELENA was able to surmount this obstacle by using a companion satellite positioned in an elliptical orbit at a higher altitude.  This companion satellite was then able to relay information between Earth and SELENA. 

Because the Moon is a homogeneous body, there are several differences between the near (Earth facing) and far-side of the Moon.  The nearside of the Moon is covered by dark basaltic plains, (the very features that Galileo once mistook for seas).  The far side of the Moon is much more heavily cratered, and the higher elevations are composed of a bright material. These compositional differences are accompanied by differences which are intrinsic properties of the materials that make up each side of the Moon, such as crustal thickness and density.  Other differences between lunar faces include volcanic activity and surface age.

Another key difference between the lunar faces is the gravitational anomalies found on either side of the Moon.   These differences in gravitational anomalies can be used to deduce possible density differences of the interior.  Positive gravitational anomalies on the nearside of the Moon have been known about for several years and are associated with the large areas of basaltic planes.  These planes are referred to as mascons (mass concentrations).    These mascons could be the result of basaltic magma filling basins after basin formation, or they could be the result of mantle uplift that could have occurred during a large impact event.  SELENA was able to map the gravitational anomalies of the lunar far-side for the first time.  What SELENA discovered was that the far-side mascons have small central positive gravitational anomalies that are surrounded by a wide ring of negative anomalies.  These differences in gravitational anomalies observed on either side of the Moon could suggest that the far-side of the Moon may have had much cooler and rigid conditions in its early history.  

SELENA also used a Lunar Radar Sounder to map subsurface stratigraphy beneath the nearside basaltic basins.  The results of this experiment show that the thickness of the most recent volcanic flows may have been deformed compressive stresses that occurred during a period of global cooling, and not entirely because of the stresses which occurred during mascon formation.

The terrain camera onboard SELENA was able to photograph volcanic flows on the lunar far-side.  These photos were then used to estimate the age of the far-side basalts using cratering statistics. Based on the cratering statistics, the age of the lunar far side was found to be much younger than the lunar nearside, with volcanic activity continuing to make fresh surface until approximately 2.5 billion years ago.

Although the data gathered so far is not enough to paint a clear picture of lunar evolution, it has become clear that the mascons formed much differently on either side of the Moon during late heavy bombardment.  To help interpret these discoveries, new data will be on its way as China, India, and the United States all have orbiters slated for lunar observation in the next couple of years.  In the meantime we are left to wonder, are these differences due to external processes such as a giant impact, or are they due to internal processes such as core formation, and crustal differentiation?  One thing seems clear, the difference in surface age on either side of the Moon will be an important variable when devising a model for lunar evolution.

Now that 2009 has begun its important for all to know that 2009 has been declared the international year of astronomy. It is the 400th anniversary of when Galileo Galilee first turned his telescopes to the heavens, opening a whole new world of scientific discovery. It is an important time to remind and education the public about the world of astronomy, with astronomy budgets tightening getting the public involved is crucial to keeping support alive and well.

The history surrounding Galileo is quite fascinating and worth looking into for any science or history enthusiast. He was truly one of the first real scientists, pioneering what we know as the modern scientific method. Galileo lived an interesting life teaching mainly in Pisa Italy (where he did the famous experiment of dropping objects of different weights off the leaning tower) and then spending the majority of his life in Florence. In Florence he spent his time educating the ruling family of the time, the Medici. He did not invent the telescope as many think, as it was first invented for use as a naval navigation tool. He was the first to use it for astronomical purposes. With his telescope he discovered the moons of Jupiter and documented sunspots, the phases of Venus, and made detailed drawings of the surface of the moon. For anyone interested a terrific read on the subject is the book ‘Galileo’s Daughter’ by Dava Sobel. It is a good biography not just of his professional but also personal life and includes real transcripts of letters between him and his daughter; it gives a good view of life in Italy at the time.

Back in 2009, many events will be happening throughout the year to commiserate this occasion. For a full list check out the official website at www.astronomy2009.org. The kick off will officially be in Paris on January 15 and 16 featuring keynote speeches from Nobel laureates and video feeds from scientists all over the world. The solar physics group will be having a yearlong campaign in over 30 countries at 150 different venues. ‘The Cosmic Diary’ is a website being launched in January focusing on the daily lives of astronomers with over 50 astronomers from 35 countries participating with blogs, articles, video, and more. Another event is the ‘100 Hours of Astronomy’ taking place on April 2-5. It will feature live web casts, public viewings, and other outreach events. One interesting feature going on the month of January is the project ‘Dark Skies Awareness’, where the International Year of Astronomy organization is trying to rise awareness about light pollution and they’ve called on the public to count the number of stars that are visible in areas with differing light pollution and you can then compare with there data on the number of stars when there is no light pollution and the results are quite surprising.

I personally encourage anyone reading to get involved. There are many ways for the public to get involved in astronomy. You can head out to your local planetarium and see what they have going on. Or go to a public viewing night held by your local university or observatory. I know some university’s go out into the community and do things like Universe in the Park viewing nights, or if you have children you can sign up their class or troop to have astronomy students come do a presentation. If you already have a telescope just take it out and make sure it gets some use, and if you know how try hooking up your camera to it and enter an astronomy picture contest. Astronomy is a fascinating subject, but in difficult financial times its important to keep the public enthused involved and educated, hopefully with some of these large scale events going on people will get reminded just how fun and amazing it can be to look up to the heavens as Galileo did so many years ago.

Saturn’s rings were first discovered by Galileo Galilei in 1610, but he was unable to identify them as rings, instead he called then “ears”. In 1655 Christiaan Huygens became the first person to identify Saturn’s “ears” as Rings. Since the discovery of the rings in 1610, there have been many theories which have attempted to describe the formation of the rings.

The most popular theory is that Saturn’s rings are only 100 million years old. These young rings would have formed by a commit that was ripped apart by Saturn’s tidal forces, or by a moon which was destroyed by a large asteroid impact. The strong evidence for this theory is that the rings are much too bright to be very old, because as time passes the rings should accumulate dust which would slowly darken the rings.

Recent simulations, based on data gathered by the Cassini mission, show that the rings might be much larger and much older than previously thought, perhaps as old as four billion years. These simulations show that the particles in the rings form clumps and are not evenly distributed particles. This could mean that there is an ongoing warfare between formation and destruction within the rings. The particles slowly clump together and a blasted apart by micro-meteors. The researchers believe that the reason for the relative brightness of the rings could be that the dust is incorporated into the centers of the clumps after reformation.

The rings consist of eleven major sub-rings. For the most part the rings have been given lettered names in the order of their discovery. The D ring is the closest to Saturn and is very faint. Voyager 1 discovered that the D ring consists of three ringlets: D73, D72, and D68. Recently Cassini has discovered that D73 has moved 200 km towards Saturn since its discovery. The C ring is about 5 meters thick and it has a mass of about 1.1×10¹⁸ kg. If viewed from above or below the ring appears transparent because 5 to 12 percent of the light perpendicular to the ring is blocked. The B ring is the thickest ring, about 5 to 15 meters. Voyager discovered “spokes” inside the B ring; these spokes were not observed again until Cassini observed them in 2007. These spokes may be seasonal phenomena, as they disappear in midsummer then reappearing around equinox, and disappearing again around midwinter. The A Ring is 10 to 30 meters thick and has a mass of about 6.2 x 10¹⁸ kg. In 2006 4 small tiny moons were discovered inside the A ring. There is now estimated to be over 1000 such moonlets inside the A ring. The F was discovered in 1979 by Pioneer 11. The ring is the most active of the rings, and is the very thin outermost ring. The ring is held together by two moons, Prometheus and Pandora. Occasionally during Prometheus’s orbit, it approaches the ring causing kinks and knots. It also steals material from the ring leaving behind a dark channel.

Besides their formation, there is still much to learn about the rings. For instance, what causes the seasonal spokes which occur inside the B ring? Why is some of the material accreted into tiny moonlets, while the rest remains as independent particles or clumps? Why has the ringlet D73 moved in towards Saturn? Whatever the answers may be, anyone who looks at Saturn through a telescope knows one thing for sure–Saturn is one of the most amazing and beautiful objects in our solar system.