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Space News Update — April 8, 2014 —

Contents

In the News

Story 1:

NASA Space Assets Detect Ocean Inside Saturn Moon

Story 2:

NASA Satellite to Continue Gathering Data Up to Planned Lunar Impact

Story 3:

NASA Severs Most Ties with Russia, Sparing Station but Pushing for U.S. Launches Again

Departments

The Night Sky

ISS Sighting Opportunities

NASA-TV Highlights

Space Calendar

Food for Thought

Space Image of the Week

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1. NASA Space Assets Detect Ocean Inside Saturn Moon

Gravity measurements by NASA's Cassini spacecraft and Deep Space Network suggest that Saturn's moon Enceladus,

which has jets of water vapor and ice gushing from its south pole, also harbors a large interior ocean beneath an ice

shell, as this illustration depicts. Image Credit: NASA/JPL-Caltech

NASA's Cassini spacecraft and Deep Space Network have uncovered evidence Saturn's moon Enceladus

harbors a large underground ocean of liquid water, furthering scientific interest in the moon as a potential

home to extraterrestrial microbes.

Researchers theorized the presence of an interior reservoir of water in 2005 when Cassini discovered water

vapor and ice spewing from vents near the moon's south pole. The new data provide the first geophysical

measurements of the internal structure of Enceladus, consistent with the existence of a hidden ocean inside

the moon. Findings from the gravity measurements are in the Friday April 4 edition of the journal Science.

"The way we deduce gravity variations is a concept in physics called the Doppler Effect, the same principle

used with a speed-measuring radar gun," said Sami Asmar of NASA's Jet Propulsion Laboratory (JPL) in

Pasadena, Calif., a coauthor of the paper. "As the spacecraft flies by Enceladus, its velocity is perturbed by an

amount that depends on variations in the gravity field that we're trying to measure. We see the change in

velocity as a change in radio frequency, received at our ground stations here all the way across the solar

system."

The gravity measurements suggest a large, possibly regional, ocean about 6 miles (10 kilometers) deep,

beneath an ice shell about 19 to 25 miles (30 to 40 kilometers) thick. The subsurface ocean evidence supports

the inclusion of Enceladus among the most likely places in our solar system to host microbial life. Before

Cassini reached Saturn in July 2004, no version of that short list included this icy moon, barely 300 miles (500

kilometers) in diameter.

"This then provides one possible story to explain why water is gushing out of these fractures we see at the

south pole," said David Stevenson of the California Institute of Technology, Pasadena, one of the paper's co-

authors.

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Cassini has flown near Enceladus 19 times. Three flybys, from 2010 to 2012, yielded precise trajectory

measurements. The gravitational tug of a planetary body, such as Enceladus, alters a spacecraft's flight path.

Variations in the gravity field, such as those caused by mountains on the surface or differences in underground

composition, can be detected as changes in the spacecraft's velocity, measured from Earth.

The technique of analyzing a radio signal between Cassini and the Deep Space Network can detect changes in

velocity as small as less than one foot per hour (90 microns per second). With this precision, the flyby data

yielded evidence of a zone inside the southern end of the moon with higher density than other portions of the

interior.

The south pole area has a surface depression that causes a dip in the local tug of gravity. However, the

magnitude of the dip is less than expected given the size of the depression, leading researchers to conclude

the depression's effect is partially offset by a high-density feature in the region, beneath the surface.

"The Cassini gravity measurements show a negative gravity anomaly at the south pole that however is not as

large as expected from the deep depression detected by the onboard camera," said the paper's lead author,

Luciano Iess of Sapienza University of Rome. "Hence the conclusion that there must be a denser material at

depth that compensates the missing mass: very likely liquid water, which is seven percent denser than ice.

The magnitude of the anomaly gave us the size of the water reservoir."

There is no certainty the subsurface ocean supplies the water plume spraying out of surface fractures near the

south pole of Enceladus, however, scientists reason it is a real possibility. The fractures may lead down to a

part of the moon that is tidally heated by the moon's repeated flexing, as it follows an eccentric orbit around

Saturn.

Much of the excitement about the Cassini mission's discovery of the Enceladus water plume stems from the

possibility that it originates from a wet environment that could be a favorable environment for microbial life.

"Material from Enceladus’ south polar jets contains salty water and organic molecules, the basic chemical

ingredients for life," said Linda Spilker, Cassini's project scientist at JPL. "Their discovery expanded our view of

the 'habitable zone' within our solar system and in planetary systems of other stars. This new validation that

an ocean of water underlies the jets furthers understanding about this intriguing environment."

Source: NASA Return to Contents

__________________________

Will Ocean Discovery On Enceladus Spur Life-Hunting Missions to Icy Moons of Saturn, Jupiter?

Astronomers are hoping that the existence of a subsurface ocean on Saturn's icy moon Enceladus will build momentum for life-hunting missions to the outer solar system. Researchers announced their discovery of the deep watery ocean on Enceladus on Thursday (April 3) in the journal Science, confirming suspicions held by many scientists since 2005, when NASA's Cassini spacecraft spied geysers of ice and water vapor erupting from Enceladus' south pole. The discovery vaults Enceladus into the top tier of life-hosting candidates along with Europa, an ice-sheathed moon of Jupiter that also hosts a subterranean ocean. Both frigid satellites bear much closer investigation,

researchers say. "I don't know which of the two is going to be more likely to have life. It might be both; it could be neither," study co-author Jonathan Lunine of Cornell University told reporters yesterday. "I think what this discovery tells us is that we just need to be more aggressive in getting the next generation of spacecraft both to Europa and to the Saturn system once the Cassini mission is over." Source: Space.com

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2. NASA Satellite to Continue Gathering Data Up to Planned Lunar Impact

NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft is gradually lowering its orbital altitude to continue making science observations prior to its planned impact on the moon’s surface on or before April 21. Ground controllers at NASA's Ames Research Center in Moffett Field, Calif., are maneuvering the spacecraft to fly approximately 1 to 2 miles (2 to 3 kilometers) above the lunar surface to gather science measurements at the lowest altitude possible. A final maneuver will ensure a trajectory that will cause LADEE to impact the far side of the moon, which is not in view of Earth or near any previous lunar mission landings. Ground controllers have little room for error with LADEE's navigation system and, at these low orbital altitudes, a small error could mean the difference between continuing to orbit above the lunar surface and impacting it. Because of this, the team does not intend to target a specific impact location on the moon's surface. "The moon's gravity field is so lumpy, and the terrain is so highly variable with crater ridges and valleys that frequent maneuvers are required or the LADEE spacecraft will impact the moon’s surface," said Butler Hine, LADEE project manager at Ames. "Even if we perform all maneuvers perfectly, there's still a chance LADEE could impact the moon sometime before April 21, which is when we expect LADEE's orbit to naturally decay after using all the fuel onboard." Until mid-April, ground controllers will continue to fire the LADEE altitude control thrusters once a week to keep the observatory in its target orbit. On April 11, LADEE will perform its final orbital maintenance maneuver before the total lunar eclipse on April 15, when Earth’s shadow passes over the moon. This eclipse, which will last approximately four hours, exposes the spacecraft to conditions at the limits of what it was designed to withstand.

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"If LADEE survives the eclipse, we will have nearly a week of additional science at low altitudes before impact," said Rick Elphic, LADEE project scientist at Ames. "For a short mission like LADEE, even a few days count for a lot – this is a very exciting time in the mission." After the eclipse, ground controllers will determine how well the spacecraft is functioning. If it is healthy, LADEE will continue to acquire and transmit science data as long as its altitude and contact with ground controllers allow. "We're very eager to see how LADEE handles the prolonged exposure to the intense cold of this eclipse, and we've used flight data to predict that most of the spacecraft should be fine," said Hine. "However, the eclipse will really put the spacecraft design through an extreme test, especially the propulsion system." Launched in September 2013, from NASA's Wallops Flight Facility on Wallops Island, Va., the vending machine-size spacecraft has been orbiting the moon since Oct. 6. On Nov. 10, LADEE began gathering science data, and on Nov. 20, the spacecraft entered its science orbit around the moon's equator. LADEE has been in extended mission operations following a highly successful 100-day primary science phase. "Because the LADEE team has flawlessly performed every maintenance maneuver, they've been able to keep the spacecraft flying in its proper orbit and have enabled this amazing mission extension and science to continue up until the very end," said Joan Salute, LADEE program executive at NASA Headquarters in Washington. LADEE's three science payload instruments have been working to unravel the mysteries of the moon's atmosphere, acquiring more than 700,000 measurements. In its previous orbit, LADEE's closest approach to the lunar surface was between 12.5 and 31 miles (20 and 50 kilometers), and its farthest was between 47 and 93 miles (75 and 150 kilometers) – a unique position that allows the spacecraft to frequently pass from lunar day to lunar night every two hours. This vantage provides data on the full range of changes and processes occurring within the moon's tenuous atmosphere. Scientists hope this data will help answer a long-standing question: Was lunar dust, electrically charged by sunlight, responsible for the pre-sunrise glow detected during several Apollo missions above the lunar horizon? LADEE also is gathering detailed information about the structure and composition of the thin lunar atmosphere. A thorough understanding of these characteristics of our nearest celestial neighbor will help researchers understand other bodies in the solar system, such as large asteroids, Mercury, and the moons of outer planets.

Source: NASA Return to Contents

Take the Plunge: LADEE Impact Challenge

When will LADEE impact the lunar surface? NASA wants to hear your best guess!

Anyone is eligible to enter the "Take the Plunge: LADEE Impact Challenge." Winners will be announced after impact and will be e-mailed a commemorative, personalized certificate from the LADEE program. The submissions deadline is 3 p.m. PDT Friday, April 11. For more information about the challenge and to enter, visit: http://socialforms.nasa.gov/ladee

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3. NASA Severs Most Ties with Russia, Sparing Station but Pushing for U.S. Launches Again

The crew members of Expedition 40/41 pose in front of a Soyuz spacecraft simulator in Star City, Russia. From left, Alex Gerst (European Space Agency), Max Suraev (Roscosmos) and Reid Wiseman (NASA). Credit: NASA

NASA plans to cease most work with the Russian Federal Space Agency amid growing tensions concerning the

Ukrainian crisis, a spokesperson confirmed with a statement to Universe Today Wednesday evening (April 2).

While the International Space Station will still see work to ―maintain safe and continuous operation‖, most

other NASA activities with Roscosmos will cease, the statement read. It added (citing the Obama

administration) that Congress now faces a choice between fully funding human U.S. launches again in 2017, or

facing years more of sending money to the Russians for Soyuz launches from Kazakhstan.

In full, this is the statement that Bob Jacobs, NASA’s deputy associate administrator of communications:

―Given Russia's ongoing violation of Ukraine's sovereignty and territorial integrity, NASA is suspending

the majority of its ongoing engagements with the Russian Federation. NASA and Roscosmos will,

however, continue to work together to maintain safe and continuous operation of the International

Space Station. NASA is laser focused on a plan to return human spaceflight launches to American soil,

and end our reliance on Russia to get into space. This has been a top priority of the Obama

Administration’s for the past five years, and had our plan been fully funded, we would have returned

American human spaceflight launches – and the jobs they support – back to the United States next

year. With the reduced level of funding approved by Congress, we’re now looking at launching from

U.S. soil in 2017. The choice here is between fully funding the plan to bring space launches back to

America or continuing to send millions of dollars to the Russians. It’s that simple. The Obama

Administration chooses to invest in America – and we are hopeful that Congress will do the same.‖

It is unclear from this statement exactly what activities would constitute ―safe and continuous operation‖ of

station. So, for example, it’s unclear so far if (for example) NASA will still send photographers to cover

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launches and landing in Russia, or to what extent NASA TV broadcasts of Russian spacewalks would be

affected.

Since the shuttle retired in 2011, NASA and other space agencies such as the European Space Agency have

relied on Russian Soyuz spacecraft to bring astronauts to the International Space Station. Crews are generally

made up of large proportions of Russian cosmonauts and American astronauts, as well as a few astronauts

from other agencies. The current Expedition 39 crew has three Russians, two Americans and a Japanese

commander, Koichi Wakata. Expedition 40 will launch aboard a Soyuz spacecraft in May, if all goes to plan.

The human spaceflight relationship between NASA and Russia stretches back to the 1970s when Russia was

then the Soviet Union. Their first joint mission was with the Apollo-Soyuz Test Project in 1975. That

relationship expanded when several NASA shuttles visited the Russian space station Mir in the 1990s, laying

the groundwork for the International Space Station agreement today.

NASA is working on a commercial crew program that right now is slated to bring U.S. astronauts into space

from American soil again in 2017. There are several proposals being considered: a human-rated version of

SpaceX’s Dragon, Blue Origin’s New Shepard, Sierra Nevada Corp.’s Dream Chaser and the Boeing Co.’s CST-

100.

It is unclear, however, how much money CCP will receive in the upcoming fiscal 2015 budget request before

Congress. Historically, NASA receives less money for this program than what the agency requests (which has

pushed back launches by a few years). The new tensions with Russia, however, could make things different

this time around. This seems to be what NASA is counting on in the statement.

As far as what missions could be affected due to cooperation with Russia, planetary scientist Barbara Cohen

said on Twitter that while it may appear the US may do little with Russia beyond the International Space

Station, cooperation in planetary science is rather big. Russian scientists contribute to several ongoing and

upcoming NASA robotic missions, and US scientists are contributing to the planning for ExoMars, which is an

ESA-Roscosmos mission, and the US is contributing Elektra telecommunication radios to the orbiter and part of

a mass spectrometer for the rover. Additionally, US scientists are working with the Verera-D mission, a

strategic Venus mission sponsored by Roscosmos, with participation by NASA’s Planetary Science Division.

The news of the breach comes about a month after NASA administrator Charlie Bolden told reporters that the Russian diplomacy crisis, which erupted after troops went to Crimea a few weeks ago (to U.S. and other countries’ condemnation), would not affect Soyuz launches or other activities related to the space station. ―Everything is nominal right now in our relationship with the Russians. We continue to monitor the situation,‖ said NASA administrator Charles Bolden in a conference call with reporters March 4, following the release of NASA’s preliminary budget request. ―The safety of our crews and our assets that has not changed. Safety is the No. 1 of NASA’s core values, so we are constantly doing contingency planning on the International Space Station for emergencies that might arise,‖ Bolden added, citing an emergency ammonia pump replacement in December as one such example. ―Those are the kinds of things we are always planning for, and in terms of the situation on the ground, we will go into contingency planning for that as the situation dictates. But right now, we don’t see any reason to do so,‖ he added. International Space Station operations were recently extended to at least 2024, and NASA officials have pointed out that it and similar agreements have weathered other world crises.

Source: Universe Today Return to Contents

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The Night Sky

Source: Sky and Telescope Return to Contents

_____________________

Check Out NASA’s New “Dashboard” for Spacecraft Communications

Tuesday, April 8 Mars is at opposition — its closest opposition

since December 2007. Mars is actually

nearest to Earth on the 14th, but the

difference is barely a trace. This is the month

for Mars with your telescope!

Wednesday, April 9 This evening, look left of the Moon by about

a fist-width at arm's length for Regulus in

Leo.

Thursday, April 10 Look above the waxing gibbous Moon this

evening for Regulus. The Sickle of Leo

extends nearly upright from Regulus.

Friday, April 11 The waxing gibbous Moon shines under Leo

tonight. Leo is where you get if you follow

the pointer stars of the Big Dipper far enough

backward.

Saturday, April 12 Look far lower left of the Moon this evening

for fiery, glary Mars. By about midnight

they're lined up horizontally in the south.

DSN Now is a live visualization of NASA’s Deep Space Network usage and which spacecraft the various antennae are talking to.

It shows real-time data of which of the three antenna complexes are being used to communicate with the various missions, how far away the spacecraft are, and various other details about data rates, speeds and modes. DSN Now is from NASA’s wonderful Eyes on the Solar System website (which uses real data to provide simulated 3-D views from of the Solar System). Source: Universe Today

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ISS Sighting Opportunities

Sighting information for other cities can be found at NASA’s Satellite Sighting Information

NASA-TV Highlights (all times Eastern Time Zone)

April 8, Tuesday

11:05 a.m. - ISS Expedition 39 Educational Event with the Sandy Hook Elementary School in Monroe, CT- JSC

(All Channels)

11:30 a.m. - Space Station Live - JSC (All Channels)

April 9, Wednesday

10:30 a.m. - Space Station Live - JSC (All Channels)

11:15 a.m. - Coverage of the ISS Progress 55 Launch to the ISS (Launch scheduled at 11:26 a.m. EDT) - JSC

(All Channels)

4:45 p.m. - Coverage of the Docking of the ISS Progress 55 to the ISS (Docking scheduled at 5:16 p.m. EDT)

- JSC (All Channels)

April 10, Thursday

8:15 a.m. - ISS Expedition 39 In-Flight Event for JAXA - JSC (All Channels)

12 p.m. - ISS Mission Control On-Console Interview with the Digital Learning Network - JSC (All Channels)

April 11, Friday

8:15 a.m. - 5 p.m. - NASA’s Human Exploration Rover Challenge - MSFC (NTV-2)

Watch NASA TV online by going to the NASA website. Return to Contents

Date Visible Max Height Appears Disappears

Tue Apr 8, 9:01 PM 3 min 27° 25 above NW 11 above NNE

Wed Apr 9, 8:12 PM 4 min 43° 39 above WNW 10 above NE

Wed Apr 9, 9:49 PM 2 min 13° 12 above NNW 11 above NNE

Thu Apr 10, 8:59 PM 3 min 16° 15 above NNW 10 above NNE

Fri Apr 11, 8:10 PM 3 min 21° 21 above NNW 10 above NNE

Fri Apr 11, 9:47 PM 2 min 10° 10 above NNW 10 above NNE

Sat Apr 12, 8:57 PM 2 min 11° 11 above NNW 10 above NNE

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Space Calendar

Apr 08 - Mars At Opposition

Apr 08 - Comet P/2010 A2 (LINEAR) At Opposition (1.335 AU)

Apr 08 - Comet 220P/McNaught At Opposition (2.530 AU)

Apr 08 - Comet 176P/LINEAR At Opposition (2.808 AU)

Apr 08 - Comet 47P/Ashbrook-Jackson At Opposition (4.215 AU)

Apr 08 - Asteroid 1 Ceres Occults 2UCAC 32877293 (12.2 Magnitude Star)

Apr 08 - Asteroid 2014 EF4 Near-Earth Flyby (0.082 AU)

Apr 08 - Asteroid 326290 Akhenaten Closest Approach To Earth (1.460 AU)

Apr 08 - Asteroid 1495 Helsinki Closest Approach To Earth (1.571 AU)

Apr 08 - Asteroid 6600 Qwerty Closest Approach To Earth (1.708 AU)

Apr 08 - Asteroid 12490 Leiden Closest Approach To Earth (1.832 AU)

Apr 08 - Asteroid 17627 Humptydumpty Closest Approach To Earth (2.234 AU)

Apr 08 - 50th Anniversary (1964), Gemini 1 Launch (Unmanned)

Apr 09 - Progress Soyuz U Launch (International Space Station)

Apr 09 - Comet 124P/Mrkos Perihelion (1.645 AU)

Apr 09 - Asteroid 2991 Bilbo Closest Approach To Earth (1.363 AU)

Apr 09 - Asteroid 10379 Lake Placid Closest Approach To Earth (2.421 AU)

Apr 09 - Asteroid 2023 Asaph Closest Approach To Earth (2.632 AU)

Apr 09 - Asteroid 118401 LINEAR Closest Approach To Earth (2.807 AU)

Apr 10 - NROL-67 Atlas 5 Launch

Apr 10 - Asteroid 14593 Everett Closest Approach To Earth (1.337 AU)

Apr 10 - Asteroid 24101 Cassini Closest Approach To Earth (2.079 AU)

Apr 10 - Asteroid 1913 Sekanina Closest Approach To Earth (2.096 AU)

Apr 10 - Asteroid 4179 Toutatis Closest Approach To Earth (2.852 AU)

Apr 10 - Dwarf Planet 136108 Haumea At Opposition (49.895 AU)

Apr 11 - Cassini, Orbital Trim Maneuver #377 (OTM-377)

Apr 11 - Comet 114P/Wiseman-Skiff At Opposition (2.280 AU)

Apr 11 - Asteroid 2014 FS52 Near-Earth Flyby (0.039 AU)

Apr 11 - Asteroid 363599 (2004 FG11) Near-Earth Flyby (0.053 AU)

Apr 11 - Asteroid 6779 Perrine Closest Approach To Earth (1.080 AU)

Apr 11 - Asteroid 2228 Soyuz-Apollo Closest Approach To Earth (2.501 AU)

Source: JPL Space Calendar Return to Contents

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Food for Thought

Fermi Data Tantalize With New Clues to Dark Matter

A view of the entire gamma-ray sky from Fermi's LAT instrument, shaded to emphasize the central galaxy. The inset is a map of the galactic center with known sources removed, which reveals the gamma-ray excess (red, green and blue)

found there. This excess emission is consistent with annihilations from some hypothesized forms of dark matter. Credit: NASA/DOE/Fermi LAT Collaboration and T. Linden (Univ. of Chicago)

A new study of gamma-ray light from the center of our galaxy makes the strongest case to date that some of

this emission may arise from dark matter, an unknown substance making up most of the material universe.

Using publicly available data from NASA's Fermi Gamma-ray Space Telescope, independent scientists at the

Fermi National Accelerator Laboratory (Fermilab), the Harvard-Smithsonian Center for Astrophysics (CfA), the

Massachusetts Institute of Technology (MIT) and the University of Chicago have developed new maps showing

that the galactic center produces more high-energy gamma rays than can be explained by known sources and

that this excess emission is consistent with some forms of dark matter.

"The new maps allow us to analyze the excess and test whether more conventional explanations, such as the

presence of undiscovered pulsars or cosmic-ray collisions on gas clouds, can account for it," said Dan Hooper,

an astrophysicist at Fermilab in Batavia, Ill., and a lead author of the study. "The signal we find cannot be

explained by currently proposed alternatives and is in close agreement with the predictions of very simple dark

matter models."

This animation zooms into an image of the Milky Way, shown in visible light, and superimposes a gamma-ray

map of the galactic center from NASA's Fermi. Raw data transitions to a view with all known sources removed,

revealing a gamma-ray excess hinting at the presence of dark matter.

The galactic center teems with gamma-ray sources, from interacting binary systems and isolated pulsars to

supernova remnants and particles colliding with interstellar gas. It's also where astronomers expect to find the

galaxy's highest density of dark matter, which only affects normal matter and radiation through its gravity.

Large amounts of dark matter attract normal matter, forming a foundation upon which visible structures, like

galaxies, are built.

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No one knows the true nature of dark matter, but WIMPs, or Weakly Interacting Massive Particles, represent a

leading class of candidates. Theorists have envisioned a wide range of WIMP types, some of which may either

mutually annihilate or produce an intermediate, quickly decaying particle when they collide. Both of these

pathways end with the production of gamma rays -- the most energetic form of light -- at energies within the

detection range of Fermi's Large Area Telescope (LAT).

When astronomers carefully subtract all known gamma-ray sources from LAT observations of the galactic

center, a patch of leftover emission remains. This excess appears most prominent at energies between 1 and 3

billion electron volts (GeV) -- roughly a billion times greater than that of visible light -- and extends outward at

least 5,000 light-years from the galactic center.

Hooper and his colleagues conclude that annihilations of dark matter particles with a mass between 31 and 40

GeV provide a remarkable fit for the excess based on its gamma-ray spectrum, its symmetry around the

galactic center, and its overall brightness. Writing in a paper submitted to the journal Physical Review D, the

researchers say that these features are difficult to reconcile with other explanations proposed so far, although

they note that plausible alternatives not requiring dark matter may yet materialize.

"Dark matter in this mass range can be probed by direct detection and by the Large Hadron Collider (LHC), so

if this is dark matter, we're already learning about its interactions from the lack of detection so far," said co-

author Tracy Slatyer, a theoretical physicist at MIT in Cambridge, Mass. "This is a very exciting signal, and

while the case is not yet closed, in the future we might well look back and say this was where we saw dark

matter annihilation for the first time."

The researchers caution that it will take multiple sightings – in other astronomical objects, the LHC or in some

of the direct-detection experiments now being conducted around the world -- to validate their dark matter

interpretation.

At left is a map of gamma rays with energies between 1 and 3.16 GeV detected in the galactic center by Fermi's LAT; red

indicates the greatest number. Prominent pulsars are labeled. Removing all known gamma-ray sources (right) reveals

excess emission that may arise from dark matter annihilations.

Image Credit: T. Linden, Univ. of Chicago

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"Our case is very much a process-of-elimination argument. We made a list, scratched off things that didn't

work, and ended up with dark matter," said co-author Douglas Finkbeiner, a professor of astronomy and

physics at the CfA, also in Cambridge.

"This study is an example of innovative techniques applied to Fermi data by the science community," said

Peter Michelson, a professor of physics at Stanford University in California and the LAT principal investigator.

"The Fermi LAT Collaboration continues to examine the extraordinarily complex central region of the galaxy,

but until this study is complete we can neither confirm nor refute this interesting analysis."

While the great amount of dark matter expected at the galactic center should produce a strong signal,

competition from many other gamma-ray sources complicates any case for a detection. But turning the

problem on its head provides another way to attack it. Instead of looking at the largest nearby collection of

dark matter, look where the signal has fewer challenges.

Dwarf galaxies orbiting the Milky Way lack other types of gamma-ray emitters and contain large amounts of

dark matter for their size – in fact, they're the most dark-matter-dominated sources known. But there's a

tradeoff. Because they lie much farther away and contain much less total dark matter than the center of the

Milky Way, dwarf galaxies produce a much weaker signal and require many years of observations to establish

a secure detection.

For the past four years, the LAT team has been searching dwarf galaxies for hints of dark matter. The

published results of these studies have set stringent limits on the mass ranges and interaction rates for many

proposed WIMPs, even eliminating some models. In the study's most recent results, published in Physical

Review D on Feb. 11, the Fermi team took note of a small but provocative gamma-ray excess.

"There's about a one-in-12 chance that what we're seeing in the dwarf galaxies is not even a signal at all, just

a fluctuation in the gamma-ray background," explained Elliott Bloom, a member of the LAT Collaboration at

the Kavli Institute for Particle Astrophysics and Cosmology, jointly located at the SLAC National Accelerator

Laboratory and Stanford University. If it's real, the signal should grow stronger as Fermi acquires additional

years of observations and as wide-field astronomical surveys discover new dwarfs. "If we ultimately see a

significant signal," he added, "it could be a very strong confirmation of the dark matter signal claimed in the

galactic center."

Source: NASA Return to Contents

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Space Image of the Week

At the Edge of NGC 2174 Image Credit: NASA, ESA, Hubble Heritage Team (STScI/AURA)

Explanation: This fantastic skyscape lies near the edge of NGC 2174 a star forming region about 6,400 light-

years away in the nebula-rich constellation of Orion. It follows mountainous clouds of gas and dust carved by

winds and radiation from the region's newborn stars, now found scattered in open star clusters embedded

around the center of NGC 2174, off the top of the frame. Though star formation continues within these dusty

cosmic clouds they will likely be dispersed by the energetic newborn stars within a few million years. Recorded

at infrared wavelengths by the Hubble Space Telescope, the interstellar scene spans about 6 light-years. The

image celebrates the upcoming 24th anniversary of Hubble's launch onboard the space shuttle orbiter

Discovery on April 24, 1990.

Source: NASA APOD Return to Contents