The small, northern constellation Triangulum harbors this magnificent face-on spiral galaxy, M33. Its popular names include the Pinwheel Galaxy or just the Triangulum Galaxy . M33 is over 50,000 light-years in diameter, third largest in the Local Group of galaxies after the Andromeda Galaxy (M31), and our own Milky Way. About 3 million light-years from the Milky Way, M33 is itself thought to be a satellite of the Andromeda Galaxy and astronomers in these two galaxies would likely have spectacular views of each other's grand spiral star systems. As for the view from planet Earth, this sharp, detailed image nicely shows off M33's blue star clusters and pinkish star forming regions that trace the galaxy's loosely wound spiral arms. In fact, the cavernous NGC 604 is the brightest star forming region, seen here at about the 1 o'clock position from the galaxy center. Like M31, M33's population of well-measured variable stars have helped make this nearby spiral a cosmic yardstick for establishing the distance scale of the Universe.

A bright trio of terrestrial planets were joined by a young Moon on September 1st, in planet Earth's early evening skies. In this view of the celestial gathering from Perth , Western Australia, the Moon's sunlit crescent is nearly horizontal at Perth's southern latitude of about 32 degrees. Venus , then Mercury , and finally Mars shine above colorful city lights on the far shore of the Swan River. The six unlit towers on the left surround a large cricket stadium. For now , the planetary trio still lingers low in the west just after sunset . But in the coming days Venus will move farther from the Sun, climbing higher after sunset, while Mercury and Mars will steadily sink into the glare along the western horizon .

A mountain top above the clouds and light-polluted cities was a good place to go to watch this August's Perseid meteor shower. In fact, this composite picture from one of the highest points in Romania, the Omu summit (2,507 meters) in the Southern Carpathian Mountains, captures about 20 of the shower's bright streaks against a starry night sky . The cosmic debris stream that creates the shower is composed of dust particles moving along parallel paths, following the orbit of their parent comet Swift-Tuttle . Looking toward the shower's radiant point in the constellation Perseus, perspective causes the parallel meteor streaks to appear to diverge. But looking directly away from the radiant point, as in this view, perspective actually makes the Perseid meteors seem to be converging toward a point below the horizon .

What created this unusual partial ring around Saturn? Discovered last year, the arc was captured in clear detail only two months ago by the Saturn-orbiting Cassini spacecraft . Since the arc occupies the same orbit as the small moon Anthe , a leading hypothesis holds that the arc was created by, and is replenished by, meteor impacts on Anthe. Similar arcs have been previously discovered, including an arc associated with the small Saturnian moon Methone , one arc related to Saturn's G ring , and several arcs orbiting Neptune . Pictured above , Anthe, only two kilometers across, is seen as the bright point near the top of the Anthe arc. The Anthe arc was imaged by the robotic space probe as it swooped to within 1.5 million kilometers of the small moon.

Our Milky Way Galaxy is not alone. It is part of a gathering of about 25 galaxies known as the Local Group . Members include the Great Andromeda Galaxy (M31), M32 , M33 , the Large Magellanic Cloud , the Small Magellanic Cloud , Dwingeloo 1 , several small irregular galaxies , and many dwarf elliptical and dwarf spheroidal galaxies . Pictured on the lower right is one of the dwarf ellipticals : NGC 205 . Like M32 , NGC 205 is a companion to the large M31, and can sometimes be seen to the south of M31 's center in photographs. The image shows NGC 205 to be unusual for an elliptical galaxy in that it contains at least two dust clouds (at 9 and 2 o'clock - they are visible but hard to spot) and signs of recent star formation . This galaxy is sometimes known as M110, although it was actually not part of Messier 's original catalog .

What's that diamond in the sky ? Cruising though space, sometimes you'll come across an unusual object. Such was the case on Friday for ESA 's Rosetta spacecraft on it's way to comet Churyumov-Gerasimenko in 2014. Robotic Rosetta buzzed right by the main belt asteroid 2867

Where is the best place on Earth to find meteorites ? Although meteors fall all over the world, they usually just sink to the bottom of an ocean , are buried by shifting terrain, or are easily confused with terrestrial rocks . At the bottom of the Earth, however, in East Antarctica , huge sheets of blue ice remain pure and barren. When traversing such a sheet, a dark rock will stick out . These rocks have a high probability of being true meteorites -- likely pieces of another world. An explosion or impact might have catapulted these meteorites from the Moon , Mars , or even an asteroid , yielding valuable information about these distant worlds and our early Solar System . Small teams of snowmobiling explorers so far have found thousands. Pictured above , ice-trekkers search a field 25-kilometers in front of Otway Massif in the Transantarctic Mountain Range during the Antarctic summer of 1995-1996.

In search of planets and the summer Milky Way , astronomer Tun

At first glance, the Helix Nebula ( aka NGC 7293 ), looks simple and round. But this well-studied example of a planetary nebula , produced near the end of the life of a sun-like star, is now understood to have a surprisingly complex geometry . Its extended loops and comet-shaped features have been explored in Hubble Space Telescope images. Still, a 16-inch diameter telescope and camera with broad and narrow band filters was used to create this sharp view of the Helix. The color composite also reveals the nebula's intriguing details, including light-year long, bluegreen radial stripes or spokes that give it the appearance of a cosmic bicycle wheel. The spoke features seem to indicate that the Helix Nebula is itself an old and evolved planetary nebula. The Helix is a mere seven hundred light years from Earth, in the constellation Aquarius .

On July 4th, 2005, the Deep Impact spacecraft directed a probe to impact the nucleus of Comet Tempel 1 . Still cruising through the solar system, earlier this year the robotic spacecraft looked back to record a series of images of its home world 31 million miles (50 million kilometers) away. In a sequence from top left to bottom right, these four frames from the video show a rotating Earth. They combine visible and near-infrared image data with enough resolution and contrast to see clouds, oceans, and continents. They also follow a remarkable transit of Earth by its large, natural satellite, the Moon . The Moon's orbital motion carries it across the field of view from left to right. Imaging the Earth from this distant perspective allows astronomers to connect overall variations in brightness at different wavelengths with planetary features. The observations will aid in the search for earth-like planets in other solar systems .