The International Space Station. Credit: NASA
Monday, April 29, 2013
Sunday, April 28, 2013
IN THE CONSTELLATION URSA MAJOR LIES NGC 2768
FROM: NASA
The soft glow in this image is NGC 2768, an elliptical galaxy located in the northern constellation of Ursa Major (The Great Bear). NGC 2768 appears here as a bright oval on the sky, surrounded by a wide, fuzzy cloud of material. This image, taken by the NASA/ESA Hubble Space Telescope, shows the dusty structure encircling the center of the galaxy, forming a knotted ring around the galaxy’s brightly glowing middle. Interestingly, this ring lies perpendicular to the plane of NGC 2768 itself, stretching up and out of the galaxy. The dust in NGC 2768 forms an intricate network of knots and filaments. In the center of the galaxy are two tiny, S-shaped symmetric jets. These two flows of material travel outwards from the galactic center along curved paths, and are masked by the tangle of dark dust lanes that spans the body of the galaxy. These jets are a sign of a very active center. NGC 2768 is an example of a Seyfert galaxy, an object with a supermassive black hole at its center. This speeds up and sucks in gas from the nearby space, creating a stream of material swirling inwards towards the black hole known as an accretion disk. This disk throws off material in very energetic outbursts, creating structures like the jets seen in the image above. Image Credit: NASA/ESA/Hubble
Saturday, April 27, 2013
THE LUNAR ATMOSPHERE
 |
| The Lunar Atmospheric Composition Experiment . CREDIT: NASA |
Article author: Brian Day
Until recently, most everyone accepted the conventional wisdom that the moon has virtually no atmosphere. Just as the discovery of water on the moon transformed our textbook knowledge of Earth’s nearest celestial neighbor, recent studies confirm that our moon does indeed have an atmosphere consisting of some unusual gases, including sodium and potassium, which are not found in the atmospheres of Earth, Mars or Venus. It’s an infinitesimal amount of air when compared to Earth’s atmosphere. At sea level on Earth, we breathe in an atmosphere where each cubic centimeter contains 10,000,000,000,000,000,000 molecules; by comparison the lunar atmosphere has less than 1,000,000 molecules in the same volume. That still sounds like a lot, but it is what we consider to be a very good vacuum on Earth. In fact, the density of the atmosphere at the moon’s surface is comparable to the density of the outermost fringes of Earth’s atmosphere where the International Space Station orbits.
What is the moon’s atmosphere made of? We have some clues. The Apollo 17 mission deployed an instrument called the Lunar Atmospheric Composition Experiment (LACE) on the moon’s surface. It detected small amounts of a number of atoms and molecules including helium, argon, and possibly neon, ammonia, methane and carbon dioxide. From here on Earth, researchers using special telescopes that block light from the moon’s surface have been able to make images of the glow from sodium and potassium atoms in the moon’s atmosphere as they are energized by the sun. Still, we only have a partial list of what makes up the lunar atmosphere. Many other species are expected.
We think that there are several sources for gases in the moon’s atmosphere. These include high energy photons and solar wind particles knocking atoms from the lunar surface, chemical reactions between the solar wind and lunar surface material, evaporation of surface material, material released from the impacts of comets and meteoroids, and out-gassing from the moon’s interior. But which of these sources and processes are important on the moon? We still don’t know.
With the discovery of significant ice deposits at the moon’s poles by NASA's Lunar CRater Observation and Sensing Satellite (LCROSS) and Lunar Reconnaissance Orbiter (LRO) missions, and the discovery of a thin scattering of water molecules in the lunar soil by the Chandrayaan X-ray Observatory, another fascinating possibility has captured researchers’ interest. The moon’s atmosphere may play a key role in a potential lunar water cycle, facilitating the transport of water molecules between polar and lower latitude areas. The moon may not only be wetter than we once thought, but also more dynamic.
One of the critical differences between the atmospheres of Earth and the moon is how atmospheric molecules move. Here in the dense atmosphere at the surface of Earth, the molecules’ motion is dominated by collisions between the molecules. However the moon’s atmosphere is so thin, atoms and molecules almost never collide. Instead, they are free to follow arcing paths determined by the energy they received from the processes described above and by the gravitational pull of the moon.
The technical name for this type of thin, collision-free atmosphere that extends all the way down to the ground is a "surface boundary exosphere." Scientists believe this may be the most common type of atmosphere in the solar system. In addition to the moon, Mercury, the larger asteroids, a number of the moons of the giant planets and even some of the distant Kuiper belt objects out beyond the orbit of Neptune, all may have surface boundary exospheres. But in spite of how common this type of atmosphere is, we know very little about it. Having one right next door on our moon provides us with an outstanding opportunity to improve our understanding.
Among the goals of the Lunar Atmosphere and Dust Environment Explorer (LADEE) are to determine the composition and structure of the tenuous lunar atmosphere and to understand how these change with time, and as external conditions vary. LADEE’s measurements come at a key time: with increasing interest in the moon by a number of nations, future missions could significantly affect the natural composition of the lunar atmosphere.
Friday, April 26, 2013
THE LAUNCH OF THE ANTARES ROCKET
FROM: NASA The Orbital Sciences Corporation Antares rocket is seen as it launches from Pad-0A of the Mid-Atlantic Regional Spaceport (MARS) at the NASA Wallops Flight Facility in Virginia, Sunday, April 21, 2013.
The test launch marked the first flight of Antares and the first rocket launch from Pad-0A. The Antares rocket delivered the equivalent mass of a spacecraft, a so-called mass simulated payload, into Earth's orbit.
Image Credit: NASA/Bill Ingalls
Thursday, April 25, 2013
Wednesday, April 24, 2013
Tuesday, April 23, 2013
Monday, April 22, 2013
NASA VIEW OF THE HORSEHEAD NEBULA
FROM: NASA
Hubble Sees a Horsehead of a Different Color
Astronomers have used NASA's Hubble Space Telescope to photograph the iconic Horsehead Nebula in a new, infrared light to mark the 23rd anniversary of the famous observatory's launch aboard the space shuttle Discovery on April 24, 1990.
Looking like an apparition rising from whitecaps of interstellar foam, the iconic Horsehead Nebula has graced astronomy books ever since its discovery more than a century ago. The nebula is a favorite target for amateur and professional astronomers. It is shadowy in optical light. It appears transparent and ethereal when seen at infrared wavelengths. The rich tapestry of the Horsehead Nebula pops out against the backdrop of Milky Way stars and distant galaxies that easily are visible in infrared light.
Hubble has been producing ground-breaking science for two decades. During that time, it has benefited from a slew of upgrades from space shuttle missions, including the 2009 addition of a new imaging workhorse, the high-resolution Wide Field Camera 3 that took the new portrait of the Horsehead. Image Credit-NASA-ESA-Hubble Heritage Team.
Sunday, April 21, 2013
THE FIRST SHUTTLE LAUNCH
FROM: NASA
A new era in space flight began on April 12, 1981, when Space Shuttle Columbia, or STS-1, soared into orbit from NASA's Kennedy Space Center in Florida. Astronaut John Young, a veteran of four previous spaceflights including a walk on the moon in 1972, commanded the mission. Navy test pilot Bob Crippen piloted the mission and would go on to command three future shuttle missions. The shuttle was humankind's first re-usable spacecraft. The orbiter would launch like a rocket and land like a plane. The two solid rocket boosters that helped push them into space would also be re-used, after being recovered in the ocean. Only the massive external fuel tank would burn up as it fell back to Earth. It was all known as the Space Transportation System. Twenty years prior to the historic launch, on April 12, 1961, the era of human spaceflight began when Russian Cosmonaut Yuri Gagarin became the first human to orbit the Earth in his Vostock I spacecraft. The flight lasted 108 minutes. Pictured here: a timed exposure of STS-1, at Launch Pad A, Complex 39, turns the space vehicle and support facilities into a night- time fantasy of light. Structures to the left of the shuttle are the fixed and the rotating service structure. Image Credit: NASA
Subscribe to:
Posts (Atom)