Observations: AstronomyCast Ultraviolet Astronomy

Ultraviolet astronomy is generally used to refer to observations of electromagnetic radiation at ultraviolet wavelengths between approximately 10 and 320 nanometres; shorter wavelengths—higher energy photons—are studied by X-ray astronomy and gamma ray astronomy. Light at these wavelengths is absorbed by the Earth's atmosphere, so observations at these wavelengths must be performed from the upper atmosphere or from space. Much of the universe looks cool when being observed with ultraviolet radiation, as it is normally associated with hotter objects; objects hotter than normal stars. Stars that are in wither the early stages or late stages of evolution. The universe is able to be observed with different kinds of radiation x-ray, gamma, etc... Each provides new and valuable insight.

APOD 4.5

This is a sequence of pictures taken last week of the Moon and the Solar System's innermost planet, Mercury. As Mercury reaches its greatest elongation angle from the Sun, it tracks a similar path as the old crescent Moon. The two are climbing along an ecliptic plane steeply inclined along the horizon. This well composed sequence captures the rising Moon and Mercury above the city lights of Brisbane in Queensland, Australia.

Observations: AstronomyCast Cosmic Rays

Cosmic rays are energetic charged subatomic particles, originating in outer space. They may produce secondary particles that penetrate the Earth's atmosphere and surface. Most primary cosmic rays (those that enter the atmosphere from deep space) are composed of familiar stable subatomic particles that normally occur on Earth, such as protons, atomic nuclei, or electrons. Although most of the subatomic particles are stable protons and neutrons, a small fraction that enter the Earth's atmosphere occur as stable particles of antimatter. Antimatter is the extension of the concept of the antiparticle to matter, where antimatter is composed of antiparticles in the same way that normal matter is composed of particles. For example, a positron and an antiproton can form an antihydrogen atom in the same way that an electron and a proton form a "normal matter" hydrogen atom. Furthermore, mixing matter and antimatter can lead to the annihilation of both. The flux of incoming cosmic rays at the upper atmosphere is dependent on the solar wind, the Earth's magnetic field, and the energy of the cosmic rays.

APOD 4.4

This is a picture of unusual blobs found in the Carina Nebula. Energetic light and winds from nearby stars are breaking apart the dark dust grains that make the iconic forms opaque. Ironically the blobs, otherwise known as dark molecular clouds, frequently create in their midst the very stars that later destroy them. This picture was taken by the orbiting Hubble Space Telescope and span a couple of light months.

APOD 4.3

This is a brilliant picture of Earth's sister planet, Venus. It was taken on April 2nd in Portal, Arizona. It was taken as Venus crossed paths with the Pleiades, another set of very bright stars. The fact that the Pleiades are normally considered very bright stars in the sky shows just how brilliant Venus appears on this night. The last similar conjunction of Venus and Pleiades occurred nearly 8 years ago, and as it did then, Venus will continue on to cross paths with the disk of the Sun in June.

APOD 4.2

This is an image of the Volcano Tungurahua which sometimes erupts spectacularly. In the picture above, taken in 2006, the 5,000 meter high volcano is erupting, emitting dark plumes of ash and lava. As the lava flows down the side of the mountain, clouds intermingle with the dark ash. Located in Ecuador, Tungurahua has become active roughly every 90 years for the last 1,300 years.

APOD 4.1

This is a picture of the Grand Canyon taken on March 26. Off in the distance, keeping the canyon alight is the moon along with the planet Venus. In the foreground, the Colorado River sparkles in the Moon's light as it travels through the canyon as seen from the southern rim. On this date, wonders of the night sky included the compact Pleiades and V-shaped Hyades star clusters poised just above the Moon. Bright planet Jupiter is below the closer Moon/Venus pairing, near the western horizon.