Guide to our Galaxy

Published on Nov 21, 2013

This virtual journey shows the different components that make up our home galaxy, the Milky Way, which contains about a hundred billion stars.

It starts at the black hole at the centre of the Milky Way and with the stars that orbit around it, before zooming out through the central Galactic Bulge, which hosts about ten billion stars.

The journey continues through a younger population of stars in the stellar disc, home to most of the Milky Way's stars, and which is embedded in a slightly larger gaseous disc. Stars in the disc are arranged in a spiral arm pattern and orbit the centre of the Galaxy.

The discs and bulge are embedded in the stellar halo, a spherical structure that consists of a large number of globular clusters -- the oldest population of stars in the Galaxy -- as well as many isolated stars. An even larger halo of invisible dark matter is inferred by its gravitational effect on the motions of stars in the Galaxy.

Looking at a face-on view of the Galaxy we see the position of our Sun, located at a distance of about 26 000 light-years from the Galactic Centre.

Finally, the extent of the stellar survey conducted by ESA's Hipparcos mission is shown, which surveyed more than 100 000 stars up to 300 light-years away from the Sun. In comparison, ESA's Gaia survey will study one billion stars out to 30 000 light-years away.

(See More Videos)

NASA | How to Cook a Comet

Published on Nov 21, 2013

(See More Videos)

A comet's journey through the solar system is perilous and violent. Before it reaches Mars - at some 230 million miles away from the sun - the radiation of the sun begins to cook off the frozen water ice directly into gas. This is called sublimation. It is the first step toward breaking the comet apart. If it survives this, the intense radiation and pressure closer to the sun could destroy it altogether.

Animators at NASA's Goddard Space Flight Center in Greenbelt, Md. created this short movie showing how the sun can cook a comet.

Such a journey is currently being made by Comet ISON. It began its trip from the Oort cloud region of our solar system and is now traveling toward the sun. The comet will reach its closest approach to the sun on Thanksgiving Day -- Nov. 28, 2013 -- skimming just 730,000 miles above the sun's surface. If it comes around the sun without breaking up, the comet will be visible in the Northern Hemisphere with the naked eye, and from what we see now, ISON is predicted to be a particularly bright and beautiful comet.

Even if the comet does not survive, tracking its journey will help scientists understand what the comet is made of, how it reacts to its environment, and what this explains about the origins of the solar system. Closer to the sun, watching how the comet and its tail interact with the vast solar atmosphere can teach scientists more about the sun itself.

This video is public domain and can be downloaded at: http://svs.gsfc.nasa.gov/goto?11384

Like our videos? Subscribe to NASA's Goddard Shorts HD podcast:
http://svs.gsfc.nasa.gov/vis/iTunes/f...

Or find NASA Goddard Space Flight Center on Facebook:
http://www.facebook.com/NASA.GSFC

Or find us on Twitter:
http://twitter.com/NASAGoddard

Exploring the dark universe at the speed of petaflops

Nov 21, 2013 by Gail Pieper

This visualization, part of a 1.1-trillion-particle simulation run on Argonne’s supercomputer
Mira, shows the complexity of cosmological structure formation.
Image via Phys.org

An astonishing 95% of our universe is made of up dark energy and dark matter. Understanding the physics of this sector is the foremost challenge in cosmology today. Sophisticated simulations of the evolution of the universe play a crucial role.

The primary lens through which scientists look at the night sky is no longer only a telescope—it's also a supercomputer. The new and coming generations of supercomputers will finally be capable of modeling the universe in the detail and volume required by astronomical surveys of the sky that are now underway, or soon will be.

Scientists use large cosmological simulations to test theories about the structure of the universe and the evolution of the distribution of galaxies and clusters of galaxies. State-of-the-art supercomputers let cosmologists make predictions and test them against data from powerful telescopes and space probes. Two decades of surveying the sky have culminated in the celebrated Cosmological Standard Model. Yet two of the model's key pillars—dark matter and dark energy, together accounting for 95% of the universe—remain mysterious. A research team led by Argonne is tackling this mystery, aided by some of the world's fastest supercomputers.

Continue Learning: http://phys.org/news/2013-11-exploring-dark-universe-petaflops.html

Related articles

• Joel Primack: Dark Matter Reveals the Structure of the Universe (askkuiper.wordpress.com)
• Dartmouth researchers shed new light on dark energy, cosmic speed-up (askkuiper.wordpress.com)

NASA's Chandra Helps Confirm Evidence of Jet in Milky Way's Black Hole

Nov. 20, 2013

Composite image of Sagittarius A* (Sgr A*), the supermassive black hole at the center of the Milky Way.
Image Credit: X-ray: NASA/CXC/UCLA/Z. Li et al; Radio: NRAO/VLA

Astronomers have long sought strong evidence that Sagittarius A* (Sgr A*), the supermassive black hole at the center of the Milky Way, is producing a jet of high-energy particles. Finally they have found it, in new results from NASA's Chandra X-ray Observatory and the National Science Foundation's Very Large Array (VLA) radio telescope.

Previous studies, using a variety of telescopes, suggested there was a jet, but these reports -- including the orientation of the suspected jets -- often contradicted each other and were not considered definitive.

"For decades astronomers have looked for a jet associated with the Milky Way's black hole. Our new observations make the strongest case yet for such a jet," said Zhiyuan Li of Nanjing University in China, lead author of a study appearing in an upcoming edition of The Astrophysical Journal and available online now.

Jets of high-energy particles are found throughout the universe, on large and small scales. They are produced by young stars and by black holes a thousand times larger than the Milky Way's black hole. They play important roles in transporting energy away from the central object and, on a galactic scale, in regulating the rate of formation of new stars.

"We were very eager to find a jet from Sgr A* because it tells us the direction of the black hole's spin axis. This gives us important clues about the growth history of the black hole," said Mark Morris of the University of California at Los Angeles, a co-author of the study.

The study shows the spin axis of Sgr A* is pointing in one direction, parallel to the rotation axis of the Milky Way, which indicates to astronomers that gas and dust have migrated steadily into Sgr A* over the past 10 billion years. If the Milky Way had collided with large galaxies in the recent past and their central black holes had merged with Sgr A*, the jet could point in any direction.

Continue Learning: http://www.nasa.gov/mission_pages/chandra/news/high-energy-particles-in-milky-way.html#.Uo0-CfmKK-0

Ames to pitch NASA on value of 'new' Kepler mission

By Stephen Clark

ASTRONOMY NOW

Posted: 16 November 2013

Artist's concept of the Kepler spacecraft. Credit: NASA/Ames

Managers in charge of the Kepler telescope have identified a way of salvaging the crippled observatory for a modified, less-sensitive cosmic survey for alien worlds, but NASA may not have the money to pay for the mission.

Since Kepler was knocked offline in May, officials at NASA's Ames Research Center in California have considered and analyzed new missions for the telescope.

And they think they have found a concept that is both feasible and scientifically intriguing.

The new mission scenario, dubbed "K2," calls for pointing Kepler across a swath of sky known as the ecliptic plane, or the plane where all the solar system's planets orbit the sun.

If approved by NASA Headquarters, the renewed Kepler campaign would be a shift from looking at stars like the sun to observing smaller, cooler stars that may harbor rocky planets close in, meaning they would be easier to detect.

"This is science that Kepler can do, and the K2 mission can do this uniquely, so this is really a selling point," said Steve Howell, Kepler's project scientist, during a Nov. 4 presentation at the second Kepler Science Conference held at Ames.

Plagued by reaction wheels and unable to adequately control its roll motion, Kepler is no longer capable of holding its gaze toward a field of more than 150,000 stars in the constellations Cygnus and Lyra. Kepler's optical detectors kept up a near-contant stare at the star field, which was selected because it was representative of the rest of the Milky Way, allowing scientists to extend their findings predict what may lie elsewhere in the sky.

Continue Learning: http://www.astronomynow.com/news/n1311/16kepler/#.UojvPvmKK-0

Dartmouth researchers shed new light on dark energy, cosmic speed-up

The detailed, all-sky picture of the Cosmic Microwave
Background in the infant universe reveals 13.77 billion
year old temperature fluctuations (shown as color differences)
that correspond to the seeds that grew to become the galaxies.
Credit: NASA/WMAP Science Team.

In a new study, Dartmouth researchers rule out a controversial theory that the accelerating expansion of the universe is an illusion.

While the findings don't explain the cosmic speed-up, they eliminate one provocative possibility that our planet, solar system and galaxy are at the center of the universe and that there is no dark energy. The findings appear in the journal Physical Review D. A PDF of the study is available on request.

The 2011 Nobel Prize was awarded for the discovery that the expansion of the universe is accelerating. One leading idea to explain the acceleration is a new, mysterious substance called dark energy, which is thought to make up nearly three-fourths of the energy of the universe.

Continue Learning: http://www.spacedaily.com/reports/Dartmouth_researchers_shed_new_light_on_dark_energy_cosmic_speed_up_999.html

NASA Spacecraft Finds Bounty of Alien Planets, Including 104 Potentially Habitable Worlds

From the first three years of Kepler data, more than 3,500 potential worlds have emerged. Since the last update in January, the number of planet candidates identified by Kepler increased by 29 percent and now totals 3,538, analysis led by Jason Rowe, a SETI research scientist.
Credit: SETI

The search for other Earth-like planets in the galaxy got a major boost today (Nov. 4) with the discovery of hundreds of newfound alien planets identified by NASA's Kepler spacecraft, a haul that includes 104 strange, new worlds that could potentially support life.

Scientists with NASA's planet-hunting Kepler mission announced the discovery of 833 new planet candidates during a press conference today, bringing the total number of candidate worlds to 3,538. Of the 104 planets in the habitable zone, 10 of them are about the size of Earth, scientists say.

Continue Learning: http://www.space.com/23460-alien-planets-kepler-discoveries-habitable-worlds.html