DARK ENERGY IS THE MAJORITY OF THE UNIVERSE
I hope to describe astronomers' most recent definitions of dark energy. To me it is one of the most fascinating concepts in astronomy. There is a description of dark energy at science@nasa. The following is my summary of the website's definition.
Scientists don't know what dark energy is, but they know how much of it there is. Dark energy makes up approximately 70% of the universe. (I question how scientists can be certain of measuring the whole universe.) The matter we can observe, including all the matter on earth that we know of, makes up less than 5% of the universe. Dark matter, which I hope to describe in a future post, makes up around 25% of the universe. (Again, I wonder how scientists can claim to know what makes up the universe.)

According to science@nasa, "Albert Einstein was the first person to realize that empty space is not the same as nothingness. Space has amazing properties, many of which are just beginning to be understood. The first property of space that Einstein discovered is that it is possible for more space to come into existence. One version of Einstein's gravity theory makes a second prediction: "empty space" can possess its own energy. This energy would not be diluted as space expands, because it is a property of space itself; as more space came into existence, more of this energy-of-space would come into existence as well. As a result, this form of energy would cause the universe to expand faster and faster as time passes. Unfortunately, no one understands why space should contain the observed amount of energy and not, say, much more or much less."


According to the aforementioned article at science@nasa, scientists do not have an absolute value of the total energy in the universe. Rather, they measure differences in energy that they can observe. Scientists are not able to predict the magnitude of the energy in the universe.

THE FAINTEST STARS
According to Astronomy Magazine's website, the Hubble Space Telescope has made a discovery that provides clues to the origin and evolution of the universe. It has imaged what Astronomy Magazine describes as "the faintest stars ever seen in a globular cluster." Globular clusters are spherical clusters of hundreds of thousands of stars. The globular cluster that the faint stars were found in is one of the oldest formations in the universe. According to Astronomy Magazine, "'These faint stars will act as clocks,' explains Harvey Richer, leader of the research team that made the discovery." The ages of these newly discovered stars will provide information on how and when globular clusters formed. According to Astronomy Magazine, "'It's a test of the age of the universe,' says Richer. 'We're learning about the timeline of the formation of nature.'"

MOON ROCK FOUND IN ANTARCTICA
According to the website of Astronomy Magazine, Geologists from Case Western Reserve University in Cleveland searched an ice field in Antarctica in 2005 for over six weeks in hopes of finding meteorites. On December 11, 2005, they found a rare meteorite that came from the moon. The geologists were a part of the U.S. Antarctic Search for Meteorites program. The lunar meteorite is the size of a golfball and is 5-ounces. It was found on the Miller Range of the Transantarctic Mountains, which is about 460 miles from the South Pole. This Moon rock is extremely special because unlike the other meteorites collected, because it consists of a coarse-grained material similar to basaltic lava that would be found in the lunar maria. (I learned in my astronomy class that maria are craters on the moon that filled with lava and then cooled.) It has crystals made of a type of glass that forms during an impact such as when it hit the earth. According to Astronomy Magazine, "the meteorite's large crystals suggest this Moon rock slowly cooled deep inside the lunar crust."

XENA BECOMES ERIS
According to a news update at the website of Spaceflight Now, a solar system body known to many astronomers as Xena (She was named after the television character in the show Xena: Warrior Princess) is now going to be named Eris. Eris was the Greek goddess of discord. Eris is a Pluto-like object which lies in the Kuiper Belt beyond Neptune. Spaceflight Now comments that this is an apt name considering all the trouble this tiny world has caused astronomers, forcing them to look again at Pluto. At 2400 km in diameter, Eris is even larger than Pluto.
Although Eris is larger than Pluto, it is not to be classed as a major planet of the Solar System. So our solar system now has eight planets. Eris is classed as a dwarf planet. It has a moon named Dysnomia, after the daughter of Eris.
On a personal note, I think it is amazing that all students in public school, as well as almost all adults, have believed for so long that our solar system is empty except for nine planets. When I studied astronomy in college, I learned that there is alot of matter out there that isn't just a star or a planet. There are alot of bodies of matter similar to Eris.

THE BLACK HOLE AT THE CENTER OF THE MILKY WAY
There is a supermassive black hole at the center of our galaxy, and in 2003 scientists discovered that its mass larger than they thought it was, yet its size is far smaller than I ever imagined.
According to an article at the website of SPACE, the supermassive black hole is larger than anyone thought. Scientists had previously thought that the black hole contained about 2.6 million times the mass of the Sun. Now they think the black hole is between 3.2 million and 4 million solar masses.
New research shows that the mass, which is unimaginably vast, takes up incredibly little space: an area about 10 times smaller than Earth's orbit around the Sun.
And imagine all that mass, so densely compressed, spinning. It spins around about once every 11 minutes. That is incredibly fast, considering the rate at which other bodies spin. The Sun takes about a month to spin on its axis. Earth spins once every 24 hours.
Black holes trap any light that gets near them. So they can't be seen. But astronomers can measure the mass of a black hole through the speed at which stars orbit it.

SUPERMASSIVE BINARY BLACK HOLES DETECTED
On April 6, 2006 the Chandra X-Ray Observatory released information about a recent discovery. The following description is informed by the information I found at the site of the Chandra X-Ray Observatory.
A team of astrophysicists recently announced a fascinating discovery. Through X-ray detection they have discovered a "proto supermassive binary black hole." An image of this system was obtained using NASA's Chandra X-ray Observatory. The two black holes were observed in radio images. The images reveal that two supermassive black holes are bound together by their gravity. They are in orbit. This is called a binary system.
The binary system of black holes is in the galaxy cluster Abell 400. Scientists at the Chandra Observatory were able to depict an image showing the two supermassive black holes (separated by 15") at the centre of the cluster.
According to the previously mentioned article released by the Chandra X-Ray Observatory, "Each black hole is located at the centre of its respective host galaxy and the host galaxies appear to be merging. It is not, however, just the two host galaxies that are colliding - the whole cluster in which they live is merging into another neighbouring galaxy cluster.Using these new data, the team show that the two black holes are moving through the intracluster medium at the supersonic speed of about 1200 km/s."
This motion would cause what Harvard University describes as "wind." It is believed that this wind would bend the radio plasma emitted from these two black holes so that it would move in the opposite direction. Both black holes' radio plasma is being bent into jets going in the same direction. This suggests that the black holes are traveling along the same path and are therefore gravitationally bound.The black holes are scheduled to collide eventually. To view an animation of the black hole merger, click here . The animation is provided by Chandra X-ray observatory.
The two black holes began to orbit one another when the galaxies that they are located in collided. The two black holes will probably come together. However, this will not occur for several million years. The collision will cause gravitational waves. Albert Einstein predicted that this would happen as a part of his theory of relativity. According to the Chandra X-Ray Observatory, " this event will produce one of the brightest sources of gravitational radiation in the Universe."

MAP OF MAGELLANIC CLOUD SHEDS LIGHT ON GALAXY FORMATION
I learned the following information from an article at the website of Spaceflight Now.
Astronomers have recently compiled hundreds of thousands of images to create a map of the Magellanic cloud. The Large Magellanic Cloud is a satellite galaxy of the Milky Way. It is about 160,000 light years away. Being able to view it as a whole gives astronomers insight into the life cycle of galaxies. Until now we have mainly been able to study galaxy evolution only within our own galaxy.
Karl Gordon of the University of Arizona Steward Observatory states, "What's exciting and significant is that our images go really deep in the galaxy, deep enough to get a life cycle of the interstellar medium, a life cycle of dust. We see young stars which consume dust as they form in dusty molecular clouds and old stars which are ejecting dust back into the interstellar medium. We can now test sophisticated theories about how stars form, how they evolve, what the different populations are, and how important they are in a global galaxy environment." ut we've measured almost the entire galaxy in deep, sharp detail."

SCIENTISTS DISCOVER POTENTIAL FOR EARTHLIKE PLANETS
I learned from an article at the National Geographic website written by Anne Minard that new research is revealing more and more potential for the existence of Earth-like planets that could harbor life.
Anne Minard writes, "The latest computer models are telling scientists that more than a third of the star systems containing Jupiterlike gas giants may also harbor Earthlike planets." I know from taking Astronomy 101 that a gas giant is like the outer planets in our solar system, which are far enough away from the sun's heat that certain gases accumulate and condense there, forming planets that are extremely large because they are made of the vast amount of gas that exists at that temperature. Scientists theorize that considering a planet's distance from the star it orbits and the matter that would accumulate there, such a planet could be covered with liquid water and might therefore support life.
Latest advances using computer models are focused on a star system like our own in that it contains gas giants that are known as hot Jupiters. Scientists believe thatover time gas giants migrate inward. According to Anne Minard, "As they move into their near-star orbits, hot Jupiters could be playing violent games of planetary billiards that produce Earthlike planets."
Scientists think that such planets may stir up debris in the region at the right distance from a star where liquid water could exist. Water and other such debris could accumulate and form Earthlike planets.
But how many planets like this could be out there? Astronomers have detected about 200 exoplanets, and about half of them are hot Jupiters.
I found an article here at www.physorg.com that further describes the potential for Earthlike planets.
An article at CNN's website provides exciting news that is more recent than the previously mentioned articles, having been posted on September 8, 2006. According to the article, "Earthlike planets covered with deep oceans that could harbor life may be found in as many as a third of solar systems discovered outside of our own, U.S. researchers said on Thursday."
An extremely comprehensive article at the Science News website describes the theory that I have described and also presents critical viewpoints about the theory.

PROOF THAT DARK MATTER EXISTS
According to an article at Spaceflight Now that reports on a NASA news release, a cosmic event has given evidence for the existence of dark matter. I learned the following from the article:
Dark matter and normal matter were separated when two large clusters of galaxies collided. This collision was discovered recently by NASA. According to Spaceflight Now, "'This is the most energetic cosmic event, besides the Big Bang, which we know about,' said team member Maxim Markevitch of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass."
Although scientists have already found significant evidence for dark matter, the observations of this collision of galaxies provides the strongest evidence yet. In clusters of galaxies matter is in the form of atoms that are concentrated as hot gas and stars. There is more hot gas in between the galaxies than the mass of all the stars combined. This matter is held within the cluster of galaxies by gravity, but the gravity is too strong to account for the gravitational force that acts on the matter observed. Therefore scientists proposed the existence of dark matter that has mass and therefore has gravity. In the cluster of galaxies there is far more dark matter than matter. It is invisible and it is detected through its gravity. Without dark matter, the galaxies would not be able to stay together and would drift apart.
Scientists studied the galaxy clusters using NASA's Chandra telescope as well as the Hubble Space Telescope, the European Southern Observatory's Very Large Telescope and the Magellan optical telescopes. According to Spaceflight Now they measured gravitational lensing, in which "gravity from the clusters distorts light from background galaxies as predicted by Einstein's theory of general relativity. The hot gas in this collision was slowed by a drag force, similar to air resistance. In contrast, the dark matter was not slowed by the impact, because it does not interact directly with itself or the gas except through gravity. This produced the separation of the dark and normal matter seen in the data."

REDEFINING THE SOLAR SYSTEM
I recently attended a show at the Cleveland Natural History Museum Planetarium. The audience was full of children. It was a delight to be among them when the speaker announced in a mysterious voice, "Pluto is no longer a planet." They gasped. Then they all began talking to one another, echoing in the domed room. I was also suprised to hear about Pluto. The news about Pluto is probably the biggest astronomy news that people are aware of right now, and therefore it is my first topic.
Spaceflight Now is a news site for astronomy. I learned the following from an article at the website Spaceflight Now:
the International Astronomical Union has determined a definition for the term "planet" that excludes Pluto. As Spaceflight Now describes the new definition of a planet, "It must orbit the sun, be massive enough that its own gravity pulls it into a nearly round shape, and be dominant enough to clear away objects in its neighborhood." Pluto meets only the first two criteria, and therefore is now labeled a "dwarf planet." Ceres, the largest known asteroid, is now considered to be a dwarf planet as well. Over a dozen other objects are now considered to be dwarf planets.

SPACE SHUTTLE TAKEOFF DELAYED
According to a news article at Yahoo! published within the last two hours , NASA was planning to launch the space shuttle Atlantis today, Friday September 8. But they have postponed the launch until Saturday. The reason for the delay was "a faulty fuel tank sensor," states Yahoo!, and this will be the fifth attempt to launch Atlantis. The space shuttle will head to the international space station for construction purposes. The construction had been postponed since the space shuttle Columbia exploded three years ago.
NASA has a "Launch Blog" that will begin six hours prior to the launch. It will provide live coverage of the launch of the space shuttle Atlantis.
NASA also has a site about Atlantis with news from the past few weeks and more details about the space shuttle. The site describes the space shuttle as being "the most complex machine ever built."