Solar Minimum and Solar Maximum

The Sun goes through a natural solar cycle approximately every 11 years. The cycle is marked by the increase and decrease of sunspots - visible as dark blemishes on the Sun's surface, or photosphere. The greatest number of sunspots in any given solar cycle is designated as "solar maximum." The lowest number is "solar minimum."

The solar cycle provides more than just increased sunspots, however. In the Sun's atmosphere, or corona, bright active regions appear, which are rooted in the lower sunspots. Scientists track the active regions since they are often the origin of eruptions on the Sun such as solar flares or coronal mass ejections.

The most recent solar minimum occurred in 2008, and the Sun began to ramp up in January 2010, with an M-class flare (a flare that is 10 times less powerful than the largest flares, labeled X-class). The Sun has continued to get more active, with the next solar maximum predicted for 2013.

The journey toward solar maximum is evident in current images of the Sun, showing a marked difference from those of 2010, with bright active regions dotted around the star.

Image Credit: NASA/SDO
Explanation from: http://www.nasa.gov/mission_pages/sunearth/news/solarmin-max.html

End of the Earth - Created by humans in 21 pictures

Aurora over Laksaa

Laksaa, Nordland Fylke, Norway

January 22, 2012

Image Credit & Copyright: Arild Heitmann

Dust Pillars in the Carina Nebula

These one-light-year-tall pillars of cold hydrogen and dust, imaged by the Hubble Space Telescope, are located in the Carina Nebula. Violent stellar winds and powerful radiation from massive stars are sculpting the surrounding nebula. Inside the dense structures, new stars may be born.

This image of dust pillars in the Carina Nebula is a composite of 2005 observations taken of the region in hydrogen light (light emitted by hydrogen atoms) along with 2010 observations taken in oxygen light (light emitted by oxygen atoms), both times with Hubble's Advanced Camera for Surveys. The immense Carina Nebula is an estimated 7,500 light-years away in the southern constellation Carina.

Image Credit:NASA, ESA, and the Hubble Heritage Project (STScI/AURA)
Explanation from: http://hubblesite.org/newscenter/archive/releases/2010/29/image/a/

Moon, Jupiter and Moons

Skygazers around planet Earth enjoyed the close encounter of planets and Moon in July 15's predawn skies. And while many saw bright Jupiter next to the slender, waning crescent, Europeans also had the opportunity to watch the ruling gas giant pass behind the lunar disk, occulted by the Moon as it slid through the night. Clouds threaten in this telescopic view from Montecassiano, Italy, but the frame still captures Jupiter after it emerged from the occultation along with all four of its large Galilean moons. The sunlit crescent is overexposed with the Moon's night side faintly illuminated by Earthshine. Lined up left to right beyond the dark lunar limb are Callisto, Ganymede, Jupiter, Io, and Europa. In fact, Callisto, Ganymede, and Io are larger than Earth's Moon, while Europa is only slightly smaller.

Image Credit & Copyright: Cristian Fattinnanzi
Explanation from: http://apod.nasa.gov/apod/ap120720.html

Milky Way Galaxy seen over Mount Rainier

Mount Rainier, Olympic Peninsula, Washington

October, 2012

Image Credit & Copyright: Dave Morrow

Mars and a Colorful Lunar Fog Bow

Even from the top of a volcanic crater, this vista was unusual. For one reason, Mars was dazzlingly bright in January 2010, when this picture was taken, as it was nearing its brightest time of the entire year. Mars, on the far upper left, is the brightest object in this picture. The brightness of the red planet peaked last week near when Mars reached opposition, the time when Earth and Mars are closest together in their orbits. Arching across the lower part of the image is a rare lunar fog bow. Unlike a more commonly seen rainbow, which is created by sunlight reflected prismatically by falling rain, this fog bow was created by moonlight reflected by the small water drops that compose fog. Although most fog bows appear white, all of the colors of the rainbow were somehow visible here. This image was taken from high atop Haleakala, a huge volcano in Hawaii, USA.

Image Credit & Copyright: Wally Pacholka
Explanation from: http://apod.nasa.gov/apod/ap100202.html

Two Earth's Satellites viewed from Houston

This photograph taken from Houston, Texas, juxtaposes Earth’s oldest satellite with one of its youngest. The Moon is thought to have been formed by the impact of a large body (perhaps Mars-sized) with the early Earth approximately 4.6 billion years ago. In contrast, the first components of the International Space Station (ISS) assumed orbit around the Earth in 1998, with assembly completed 13 years later—a significant period of time to us, but the merest fraction of a second in the history of the Moon.

While the ISS appears to be fairly close to the Moon’s surface in the image, it’s a trick of perspective. The Moon orbits Earth at an average distance of 384,400 kilometers (238,855 miles), while the ISS orbits at altitudes ranging from approximately 330 to 410 kilometers (205 to 255 miles).

The ISS can frequently be viewed from the Earth’s surface with the naked eye as a bright object moving rapidly across the sky. The ISS has also been photographed from Earth transiting more dramatic backdrops, such as the Sun.

As can be seen in the high-resolution version of this image, major structural elements of the Station—such as the solar panel arrays—can be resolved using high-powered binoculars or lenses. Major features of the lunar nearside surface are likewise discernable with the naked eye, the most obvious being the dark maria lowlands (mare in plural) contrasting with the bright highland regions (or terrae). With moderate magnification, other features such as impact craters become clearly visible; for example, Copernicus and Tycho Craters.

Image Credit: NASA
Explanation from: http://earthobservatory.nasa.gov/IOTD/view.php?id=76942