APOD 4.8 Station and Shuttle Transit the Sun

In this image, there are two small dark spots on the sun. However, they aren't sun spots. They are actually the International Space Station and the Space Shuttle Atlantis transiting the Sun. The bigger object is the ISS and the smaller one is Atlantis. The ISS and Space Shuttles are often seen streaking across the sky together during the night, but it is much rarer to see images of the two objects on the disk of the Sun. The two objects are orbiting about 350 kilometers above the Earth's surface. This image was taken about 50 minutes before the shuttle docked with the space station and this mission should be Atlantis' last mission.

Apod 4.7 Tentacles of the Tarantula Nebula

The Tarantula Nebula is located in the Large Magellanic Cloud and is the largest, most violent region of star formation in the Local Group of Galaxies. It is also known as 30 Doradus. It is an emission nebula, indicated by its red and pink coloring which is caused by the Hydrogen Alpha line radiation. Supernova remnants and dark nebula also exist there. The brightest region, which is just left of center is called R136 and contains many of the most massive, hottest, and brightest stars known. This star forming region would take up half of our sky if it were at the distance of the Orion Nebula. This is the most detailed image of this region ever taken.

Apod 4.6 Iguaçu Starry Night

This image was taken at the Iguacu Falls National Park on the border of Brazil and Argentina in the Southern Hemisphere. Many prominent objects are visible in the night sky and in this image, including Alpha Centauri, Beta Centauri, the Coalsack, the Southern Cross, both Magellanic Clouds, the Carina Nebula, Sirius, and Canopus. From our location, only Sirius and Canopus are visible in the constellations Canis Major and Carina, respectively. It is nice to see this image because we have also studied Alpha and Beta Centauri, and both Magellanic Clouds, but have so far not been able to see them in the sky because our latitude is too high in the Northern Hemisphere. Another intriguing feature is the influence of light on the picture coming from Argentina's Iguazú Falls International Airport. The center of the image is very bright from the light coming from the airport, so either the airport must be very close and/or very bright. I didn't realize an airport could cause that much light and affect a region of the sky that is so large.

Apod 4.5 The Antennae

This image parallels with our study of galaxy interactions. This image shows two galaxies colliding in the constellation Corvus, some 60 million light years away. Their collision has triggered rapid star formation near the center of the collision. One of the most interesting features of the image is the presence of two tails extending from opposite sides of the collision. They were created by matter being flung from the scene of the collision by gravitational tidal forces. These two streaks give the constellation its name, The Antennae.

Interacting Galaxies

http://hyakutake1957.files.wordpress.com/2008/04/colliding-galaxies.png
http://cosmology.net/images/Collidinggalaxies5678.jpg
http://news.nationalgeographic.com/news/2006/10/images/061019-galaxies_big.jpg
http://www.spacedaily.com/images/supernova-discovered-pair-colliding-galaxies-antennae-bg.jpg
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http://www.foxnews.com/images/366647/0_21_galaxies_hubble_6.jpg
http://talklikeaphysicist.com/wp-content/uploads/2008/04/collidinggalaxy-1.jpg
http://physics.uwyo.edu/~stark/outreach/galaxy/colliding/
http://www.twinlitworlds.com/hubble/pix/jpgsfull/collision.jpg
http://mainland.cctt.org/biolab/images/Colliding_Galaxies_HST_Gif.gif
http://www.noao.edu/gateway/intergal2.gif
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http://www.spacedaily.com/images/arp-87-pair-interacting-galaxies-bg.jpg
http://www.noao.edu/image_gallery/images/d5/vv150b.jpg
http://www.etsu.edu/physics/wars/arp107.jpg
http://coolcosmos.ipac.caltech.edu/cosmic_kids/learn_sirtf/images/interacting.gif
http://astro.uchicago.edu/~grodnick/gallery/galaxies/m51-irg_hogg.jpg
http://housefly.astro.princeton.edu/~rhl/PrettyPictures/M51-4x4.jpg

Apod 4.4 The Bloop: A Mysterious Sound from the Deep Ocean

This picture is a visual representation of the Bloop, which was a sound recorded in the Pacific Ocean in 1997 using deep sea microphones that had been spy microphones in World War 2. In the graph, time is shown on the horizontal axis, deep pitch is shown on the vertical axis, and brightness designates loudness. It is the loudest sound ever recorded in an ocean at over 150 decibels and was audible 5,000 kilometers away and by two different microphones that were over 3000 miles apart from one another. The sound is similar to that of a blue whale, but the blue whale isn't large enough to create such a monstrous sound. Two potential explanations are that there could be a gigantic life form at the bottom of the ocean that we have yet to discover, such as a prehistoric animal that survived through the extinction periods, or that an iceberg calving, an undersea earthquake, or an undersea volcano caused the noise. Since the bloop was recorded, no other bloops have been heard.

Astronomy Cast Ep. 177: Mysteries of the Milky Way, Part 2

How many spiral arms does the Milky Way have?:
There are man different types of spiral galaxies, from normal and barred, to even smaller classifications in each broader group. The arms are caused by density waves moving through the Galaxy. When you look at the galaxy in different wavelengths, you get different data on how many arms there are. Therefore, blue light was selected as a constant of observation. In blue light, the Milky Way appears to have 2 spiral arms.
Sibling Stars: Did other stars form in our solar nebula? What happened to them?
Everything starts out bound together in a star forming region. Over time, the star-forming region stretches out and the sibling stars start to separate. The best way to match with siblings is to match the Sun's composition with other stars'. Unfortunately, non-sibling stars can match as well.
Mass-extinctions:
Seem to trend every 60 million years. Are we due?
When the solar system goes through the Galaxy's disk, it goes through areas of high and low density, we become susceptible to cosmic rays and higher asteroid rates in the high density areas.
G-dwarfs: dwarf stars in the G part of the H-R diagram. They should be more abundant than large stars, but aren't. Why?
There should be a group of stars formed right after the Big Bang that are almost purely hydrogen and helium, but we haven't found a single one yet. They are called Population 3 stars. One explanation is that without the presence of metals, only giant stars could form out of pure hydrogen and helium. The other solution is that the first stars were so giant that they lived and died before any small stars could form. This prevents any G dwarves from forming, and therefore nothing that formed before the first generation of supernovae is capable of still being alive today because the supernova polluted space with metals.
Where are the intermediate mass black holes? We've found stellar mass and supermassive black holes, but only a couple of intermediate size black holes in the whole galaxy. We don't have enough evidence currently to have any real plausible conclusions.