APOD 4.1

Picture from March 30, 2011

This is the spiral galaxy know as NGC 5584. The galaxy is over 50,000 light-years across and some 72 million light-years away in the constellation of Virgo. The galaxy, with its bright young stars and dark dust lanes, is really a beautiful sight. However, there was also a recent type Ia supernova (the explosion of a white dwarf star) in the galaxy, useful tools in determining distances in the cosmos. Data gathered from the supernova, as well as 7 other galaxies, is being used to determine Hubble's Constant - the expansion rate of the universe. The results of this effort seem to support the theory that dark energy, a mysterious force that we cannot detect, is accelerating the expansion of the universe.

Astronomy Cast - Ep. 213: Supermassive Black Hole

On this episode of Astronomy Cast, the hosts discussed a relatively recent development in astronomy, Supermassive black holes. There is now thought to be one at the center of every galaxy in the universe, including our own Milky Way. Their discovery is a result of observing the orbital speeds of stars close to the center of the galaxy. They were observed to be moving at phenomenal speeds, and the calculated mass of the object they are orbiting was found to be millions of times more massive than the sun. Exactly how they came to be so much more massive than black holes made by collapsing stars is still poorly understood. They could not have been formed in the big bang, as all models predict an even distribution of mass in the early universe. Some other theories suggest that they could have been formed over time by simply accruing a lot of material. However, this process would take a very long time (longer than the time a stellar black hole would have had to grow to the size of a supermassive one) due to the fact that not all matter that approaches a black hole falls in. A lot of the matter is actually jettisoned through jets near the poles of the black hole. The matter is jettisoned with very high energy at relativistic speeds at both poles of the black hole. Strangely, when these jets are faced towards us the physics involved with them causes the matter to appear to be moving faster than light speed. The only thing stopping them from actually achieving such speeds is the relativistic effect of the black hole itself, which actually slows down time around it.

Observation 3/26/11

Tonight at Astronomy Night, we observed the bright stars of the Winter sky begin to appear as the sun set. Starting with Sirius, the whole of the "Heavenly G" (Aldebaren, Capella, Castor, Pollux, Procyon, Sirius, Rigel, and Betelgeuse) came into view, as well as the other first magnitude star, Canopus. To the northeast, part of the Big Dipper of Ursa Major was visible, which pointed the way to Polaris, the pole star. Through binoculars, I also observed the star clusters of Taurus (the Pleiades and the Hyades), as well as the faint glow of the Orion Nebula. The asterism of "the kids" in the constellation of Auriga was also observed.

APOD 3.8

This is a picture of the galaxy NGC 3628. It is a galaxy some 35 million light years distant in the springtime constellation of Leo the Lion which astronomers suspect is a spiral galaxy. It is somewhat difficult to determine the structure of the galaxy because, as you can see, we only have a view of the edge. However, dust lanes are seen to cut across the middle of the galaxy, suggesting that it is a spiral galaxy. It is somewhat similar in size to our own Milky Way, but the disk seem to fan out near the edge. To the upper left in the image, a "tidal tail" (long stretch of material reaching out of the galaxy) is visible. This suggests that the galaxy is interacting gravitationally with the other 2 galaxy in the Leo Triplet (a group of 3 galaxies in Leo), M66 and M65.

APOD 3.7

Picture from March 12, 2011

This is a mosaic image of the Mare Orientale, a prominent feature on the moon. From a terrestrial perspective, it would be just barely on the moon's western edge, making it difficult to see. This mosaic of the impact basin was made from pictures taken by the Lunar Reconnaissance Orbiter. The Mare Orientale (Italian for "Eastern Sea") is the youngest large impact basin on the moon, despite being some 3 billion years old. It is 600 miles across, and was formed by a collision with an asteroid, which subsequently caused a rippling effect in the lunar crust. The reason these regions are called "seas" despite being located on our dry and barren moon dates back to a time when astronomers were only able to see them as big dark spots that resembled bodies of water.