Thursday, December 31, 2009
Dust and the Helix Nebula
Wednesday, December 30, 2009
Suzaku Finds "Fossil" Fireballs from Supernovae
"This is the first evidence of a new type of supernova remnant -- one that was heated right after the explosion," said Hiroya Yamaguchi at the Institute of Physical and Chemical Research in Japan.
A supernova remnant usually cools quickly due to rapid expansion following the explosion. Then, as it sweeps up tenuous interstellar gas over thousands of years, the remnant gradually heats up again.
Capitalizing on the sensitivity of the Suzaku satellite, a team led by Yamaguchi and Midori Ozawa, a graduate student at Kyoto University, detected unusual features in the X-ray spectrum of IC 443, better known to amateur astronomers as the Jellyfish Nebula.
The remnant, which lies some 5,000 light-years away in the constellation Gemini, formed about 4,000 years ago. The X-ray emission forms a roughly circular patch in the northern part of the visible nebulosity.
Suzaku's X-ray Imaging Spectrometers (XISs) separate X-rays by energy in much the same way as a prism separates light into a rainbow of colors. This allows astronomers to tease out the types of processes responsible for the radiation.
Some of the X-ray emission in the Jellyfish Nebula arises as fast-moving free electrons sweep near the nuclei of atoms. Their mutual attraction deflects the electrons, which then emit X-rays as they change course. The electrons have energies corresponding to a temperature of about 12 million degrees Fahrenheit (7 million degrees Celsius).
Several bumps in the Suzaku spectrum were more puzzling. "These structures indicate the presence of a large amount of silicon and sulfur atoms from which all electrons have been stripped away," Yamaguchi said. These "naked" nuclei produce X-rays as they recapture their lost electrons.
But removing all electrons from a silicon atom requires temperatures higher than about 30 million degrees F (17 million C); hotter still for sulfur atoms. "These ions cannot form in the present-day remnant," Yamaguchi explained. "Instead, we're seeing ions created by the enormous temperatures that immediately followed the supernova."
The team suggests that the supernova occurred in a relatively dense environment, perhaps in a cocoon of the star's own making. As a massive star ages, it sheds material in the form of an outflow called a stellar wind and creates a cocoon of gas and dust. When the star explodes, the blast wave traverses the dense cocoon and heats it to temperatures as high as 100 million degrees F (55 million C), or 10,000 times hotter than the sun's surface.
Eventually, the shock wave breaks out into true interstellar space, where the gas density can be as low as a single atom per cubic centimeter -- about the volume of a sugar cube. Once in this low-density environment, the young supernova remnant rapidly expands.
The expansion cools the electrons, but it also thins the remnant's gas so much that collisions between particles become rare events. Because an atom may take thousands of years to recapture an electron, the Jellyfish Nebula's hottest ions remain even today, the astronomers reported in the Nov. 1 issue of The Astrophysical Journal.
"Suzaku sees the Jellyfish's hot heart," Ozawa said.
The team has already identified another fossil fireball in the supernova remnant known as W49B, which lies 35,000 light-years away in the constellation Aquila. In the Nov. 20 edition of The Astrophysical Journal, Ozawa, Yamaguchi and colleagues report X-ray emission from iron atoms that are almost completely stripped of electrons. Forming these ions requires temperatures in excess of 55 million degrees F (30 million C)-- nearly twice the observed temperature of the remnant's electrons.
Launched on July 10, 2005, Suzaku was developed at the Japanese Institute of Space and Astronautical Science (ISAS), which is part of the Japan Aerospace Exploration Agency (JAXA), in collaboration with NASA and other Japanese and U.S. institutions.
Spitzer's M101
Tuesday, December 29, 2009
Rigel and the Witch Head Nebula
Tuesday, December 22, 2009
Planetary Systems Now Forming in Orion
Monday, December 21, 2009
Star Cluster R136 Bursts Out
Sunday, December 20, 2009
Tutulemma: Solar Eclipse Analemma
Friday, December 18, 2009
Update on Last Night's DNS Disruption
During the attack, we were in direct contact with our DNS provider, Dynect. We worked closely to reset our DNS as quickly as possible. The motive for this attack appears to have been focused on defacing our site, not aimed at users—we don't believe any accounts were compromised. If you're concerned that your account could have been affected in some way, feel free to contact us, accountsafe [at] twitter.com.
Aurora Shimmer, Meteor Flash
Southern Geminids
Thursday, December 17, 2009
Mojave Desert Fireball
Wednesday, December 16, 2009
Comet Hyakutake Passes the Earth
Tuesday, December 15, 2009
A Fading Moonset Over Hong Kong
Wednesday, December 9, 2009
HUDF Infrared: Dawn of the Galaxies
Tuesday, December 8, 2009
Ice Moon Tethys from Saturn-Orbiting Cassini
Monday, December 7, 2009
The International Space Station Over the Horizon
Sunday, December 6, 2009
The Magnificent Tail of Comet McNaught
Saturday, December 5, 2009
Himalayan Skyscape
Friday, December 4, 2009
STS-130 Mission Information
Launch Target:
Feb. 4, 2010
Orbiter:
Endeavour
Mission Number:
STS-130
(130th space shuttle flight)
Launch Window:
10 minutes
Launch Pad:
39A
Mission Duration:
13 days
Landing Site:
KSC
Inclination/Altitude:
51.6 degrees/122 nautical miles
Primary Payload:
32nd station flight (20A), Tranquility Node 3, Cupola
STS-130 Crew Profiles
Endeavour will deliver a third connecting module - the Tranquility node - to the station and a seven-windowed cupola to be used as a control room for robotics. The mission will feature three spacewalks.
STS-130 is the 32nd shuttle mission to the station.
STS-130 Crew Profiles
George D. Zamka
Commander
View biography
Terry W. Virts Jr.
Pilot
View biography
Nicholas J. M. Patrick
Mission Specialist
View biography
Robert L. Behnken
Mission Specialist
View biography
Stephen K. Robinson
Mission Specialist
View biography
Kathryn P. Hire
Mission Specialist
View biography
Space Shuttle Mission: STS-130
Today, the six STS-130 astronauts are studying flight procedures at NASA's Johnson Space Center in Houston.
Shuttle Endeavour, with its payload of the Tranquility node and the seven-windowed Cupola module, is targeted to launch Feb. 4, 2010.
Endeavour's STS-130 Mission
Commander George Zamka will lead the STS-130 mission to the International Space Station aboard space shuttle Endeavour. Terry Virts will serve as the pilot. Mission specialists are Nicholas Patrick, Robert Behnken, Stephen Robinson and Kathryn Hire. Virts will be making his first trip to space.
Endeavour will deliver a third connecting module, the Tranquility node, to the station in addition to the seven-windowed Cupola module, which will be used as a control room for robotics. The mission will feature three spacewalks.
Liftoff from NASA's Kennedy Space Center in Florida is targeted for February 4, 2010 at 5:52 a.m. EST.
Additional Resources
› STS-129 Mission Information
The Double Cluster
Thursday, December 3, 2009
Honoring Apollo 13's Fred Haise
The ceremony took place at Biloxi's Gorenflo Elementary School.
Pictured from left to right are school principal Tina Thompson, Administrator Bolden, Fred Haise, Biloxi Public School District Superintendent Paul Tisdale and Stennis Space Center Director Gene Goldman.
Daphnis' Disturbances
Near the center of the image, tiny Daphnis (8 kilometers, 5 miles across) appears as a bright dot in the Keeler Gap near the edge waves it has created in the A ring. The moon has an inclined orbit and its gravitational pull perturbs the orbits of the particles of the A ring forming the Keeler Gap's edge and sculpts the edge into waves having both horizontal (radial) and out-of-plane components. Material on the inner edge of the gap orbits faster than the moon so that the waves there lead the moon in its orbit. Material on the outer edge moves slower than the moon, so waves there trail the moon. See PIA11656 to learn more about this process.
Epimetheus (113 kilometers, 70 miles across) orbits beyond the F ring at the bottom of the image. Bright specks in the image are background stars.
This view looks toward the northern, sunlit side of the rings from about 11 degrees above the ringplane.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Sept. 24, 2009. The view was obtained at a distance of approximately 1.8 million kilometers (1.1 million miles) from Daphnis. Image scale is 11 kilometers (7 miles) per pixel.
The Cassini Equinox Mission is a joint United States and European endeavor. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The imaging team consists of scientists from the US, England, France, and Germany. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.
Polar Ring Galaxy NGC 660
Wednesday, December 2, 2009
Scientists Explain Puzzling Lake Asymmetry on Titan
Saturn's oblong orbit around the sun exposes different parts of Titan to different amounts of sunlight, which affect cycles of precipitation and evaporation in those areas. Similar variations in Earth's orbit also drive long-term ice-age cycles on our planet.
As revealed by Synthetic Aperture Radar imaging data from NASA's Cassini spacecraft, liquid methane and ethane lakes in Titan's northern high latitudes cover 20 times more area than lakes in the southern high latitudes. The Cassini data also show there are significantly more partially filled and now-empty lakes in the north. (In the radar data, smooth features -- like the surfaces of lakes -- appear as dark areas, while rougher features -- such as the bottom of an empty lake-appear bright.) The asymmetry is not likely to be a statistical fluke because of the large amount of data collected by Cassini in its five years surveying Saturn and its moons.
Scientists initially considered the idea that "there is something inherently different about the northern polar region versus the south in terms of topography, such that liquid rains, drains or infiltrates the ground more in one hemisphere," said Oded Aharonson of Caltech, lead author of the Nature Geoscience paper.
However, Aharonson notes that there are no substantial known differences between the north and south regions to support this possibility. Alternatively, the mechanism responsible for this regional dichotomy may be seasonal. One year on Titan lasts 29.5 Earth years. Every 15 Earth years, the seasons of Titan reverse, so that it becomes summer in one hemisphere and winter in the other. According to this seasonal variation hypothesis, methane rainfall and evaporation vary in different seasons -- recently filling lakes in the north while drying lakes in the south.
The problem with this idea, Aharonson said, is that it accounts for decreases of about one meter per year in the depths of lakes in the summer hemisphere. But Titan's lakes are a few hundred meters deep on average, and wouldn't drain (or fill) in just 15 years. In addition, seasonal variation can't account for the disparity between the hemispheres in the number of empty lakes. The north polar region has roughly three times as many dried-up lake basins as the south and seven times as many partially filled ones.
"How do you move the hole in the ground?" Aharonson asked. "The seasonal mechanism may be responsible for part of the global transport of liquid methane, but it's not the whole story." A more plausible explanation, say Aharonson and his colleagues, is related to the eccentricity of the orbit of Saturn -- and hence of Titan, its satellite -- around the sun.
Like Earth and other planets, Saturn's orbit is not perfectly circular, but is instead somewhat elliptical and oblique. Because of this, during its southern summer, Titan is about 12 percent closer to the sun than during the northern summer. As a result, northern summers are long and subdued; southern summers are short and intense.
"We propose that, in this orbital configuration, the difference between evaporation and precipitation is not equal in opposite seasons, which means there is a net transport of methane from south to north," said Aharonson. This imbalance would lead to an accumulation of methane -- and hence the formation of many more lakes -- in the northern hemisphere.
This situation is only true right now, however. Over very long time scales of tens of thousands of years, Saturn's orbital parameters vary, at times causing Titan to be closer to the sun during its northern summer and farther away in southern summers, and producing a reverse in the net transport of methane. This should lead to a buildup of hydrocarbon -- and an abundance of lakes -- in the southern hemisphere.
"Like Earth, Titan has tens-of-thousands-of-year variations in climate driven by orbital motions," Aharonson said. On Earth, these variations, known as Milankovitch cycles, are linked to changes in solar radiation, which affect global redistribution of water in the form of glaciers, and are believed to be responsible for ice-age cycles. "On Titan, there are long-term climate cycles in the global movement of methane that make lakes and carve lake basins. In both cases we find a record of the process embedded in the geology," he added.
"We may have found an example of long-term climate change, analogous to Milankovitch climate cycles on Earth, on another object in the solar system," he said.
The paper's co-authors are Caltech graduate student Alexander G. Hayes; Jonathan I. Lunine, Lunar and Planetary Laboratory, Tucson, Ariz.; Ralph D. Lorenz, Applied Physics Laboratory at the Johns Hopkins University, Laurel, Md.; Michael D. Allison, NASA Goddard Institute for Space Studies, New York; and Charles Elachi, director of JPL. The work was partially funded by the Cassini Project.
For more information about the Cassini-Huygens mission, visit: http://www.nasa.gov/cassini or http://saturn.jpl.nasa.gov/index.cfm . The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate in Washington, D.C.
Atlantis and the STS-129 Profile
Undocking of the two spacecraft occurred at 3:53 a.m. CST on Nov. 25, 2009.
Atlantis and the STS-129 crew landed safely at Kennedy Space Center on Nov. 27
Details of Dark Senkyo
To learn about this area that appears dark near the moon's equator. This view looks toward Saturn-facing side of Titan (5150 kilometers, 3200 miles across) and is centered on terrain at 1 degree south latitude, 345 degrees west longitude. North on Titan is up and rotated 10 degrees to the right.
The image was taken with the Cassini spacecraft narrow-angle camera on Oct. 12, 2009 using a spectral filter sensitive to wavelengths of near-infrared light centered at 938 nanometers. The view was acquired at a distance of approximately 296,000 kilometers (184,000 miles) from Titan and at a Sun-Titan-spacecraft, or phase, angle of 11 degrees. Image scale is 2 kilometers (1 mile) per pixel.
The Cassini Equinox Mission is a joint United States and European endeavor. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The imaging team consists of scientists from the US, England, France, and Germany. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.
Dust Sculptures in the Rosette Nebula
Tuesday, December 1, 2009
Another Stall of Right-Rear Wheel Ends Drive
Before the Sol 2099 drive ended, Spirit completed 1.4 meters of wheel spin and the rover's center moved 0.5 millimeters (0.02 inch) forward, 0.25 millimeters (0.01 inch) to the left and 0.5 millimeters (0.02 inch) downward. Since Spirit began extrication on Sol 2088, the rover has performed 9.5 meters (31 feet) of wheel spin and the rover's center, in total, has moved 16 millimeters (0.63 inch) forward, 10 millimeters (0.39 inch) to the left and 5 millimeters (0.20 inch) downward.
Expedition 21 Crew Lands in Kazakhstan
All three crew members were reported to be in good condition. Due to icy conditions at the landing site, the landing support team recalled its helicopters to their bases in Kustanai and Arkalyk, Kazakhstan. Instead the team arrived in all-terrain vehicles from nearby Arkalyk to extract the Expedition 21 crew members from the Soyuz crew module.
Romanenko, De Winne and Thirsk spent 188 days in space, 186 of those aboard the orbiting International Space Station. The three arrived at the station in May as part of Expedition 20, which marked the start of six-person crew operations aboard the station. With their arrival, all five of the international partner agencies – NASA, the Russian Federal Space Agency (Roscosmos), the Japan Aerospace Exploration Agency (JAXA), the European Space Agency (ESA) and the Canadian Space Agency (CSA) – were represented on orbit for the first time.
Romanenko, a cosmonaut with Roscosmos, served as a flight engineer for Expeditions 20 and 21. He was selected as a test-cosmonaut candidate of the Gagarin Cosmonaut Training Center Cosmonaut Office in December 1997. The son of veteran Cosmonaut Yuri Romanenko, he qualified as a test cosmonaut in November 1999.
De Winne, an ESA astronaut, served as a flight engineer for Expeditions 20 and 21 and commander for Expedition 21. He spent nine days aboard the station in 2002 as a member of the Odissea mission arriving on a new spacecraft, the Soyuz TMA-1, then leaving on an older Soyuz TM-34.
Thirsk, a CSA astronaut, served as a flight engineer for Expeditions 20 and 21. In 1996, Thirsk flew as a payload specialist astronaut aboard space shuttle mission STS-78, the Life and Microgravity Spacelab mission.
After traveling back to the Gagarin Cosmonaut Training Center in Star City, Russia, the crew members will be reunited with their families and start their reorientation to a gravity environment after a half year off the planet.
Commander Jeff Williams and Flight Engineer Maxim Suraev remain on the station, comprising the Expedition 22 crew as a two-man contingent for three weeks until the arrival Dec. 23 of Russian cosmonaut Oleg Kotov, NASA’s T.J. Creamer, and Soichi Noguchi of the Japan Aerospace Exploration Agency, who will launch to the station Dec. 20 on the Soyuz TMA-17 craft.
NGC 6992: Filaments of the Veil Nebula
Slicing the Arc
Although it can't be seen here, the tiny moonlet Aegaeon (formerly known as S/2008 S 1) orbits within the bright arc. See PIA11148 to learn more. This view looks toward the northern, sunlit side of the rings from about 4 degrees above the ringplane. Many background stars are visible elongated by the motion of the spacecraft during the image's exposure.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Oct. 9, 2009. The view was obtained at a distance of approximately 2.1 million kilometers (1.3 million miles) from Saturn. Image scale is 12 kilometers (8 miles) per pixel.
The Cassini Equinox Mission is a joint United States and European endeavor. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The imaging team consists of scientists from the US, England, France, and Germany. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.
For more information about the Cassini Equinox Mission visit http://ciclops.org
Monday, November 30, 2009
WISE Snug in Its Nose Cone
The fairing will split open like a clamshell about five minutes after launch. The spacecraft will circle Earth over the poles, scanning the entire sky one-and-a-half times in nine months. The mission will uncover hidden cosmic objects, including the coolest stars, dark asteroids and the most luminous galaxies.
NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages WISE for NASA's Science Mission Directorate, Washington. The principal investigator, Edward Wright, is at UCLA. The mission was competitively selected under NASA's Explorers Program managed by the Goddard Space Flight Center, Greenbelt, Md. The science instrument was built by the Space Dynamics Laboratory, Logan, Utah, and the spacecraft was built by Ball Aerospace & Technologies Corp., Boulder, Colo. Science operations and data processing take place at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA.
More information is online at http://www.nasa.gov/wise and http://wise.astro.ucla.edu .
Shadow and Spokes
Mimas, the moon casting the shadow, is not shown. To learn more about the ghostly radial markings called spokes, see PIA11144 and PIA08288. Spokes appear bright when they are viewed at phase, or Sun-Saturn-spacecraft, angles higher than about 45 degrees. The phase angle in this image is 106 degrees.
The novel illumination geometry that accompanies equinox lowers the sun's angle to the ringplane, significantly darkens the rings, and causes out-of-plane structures to look anomalously bright and cast shadows across the rings. These scenes are possible only during the few months before and after Saturn's equinox which occurs only once in about 15 Earth years. Before and after equinox, Cassini's cameras have spotted not only the predictable shadows of some of Saturn's moons (see PIA11657), but also the shadows of newly revealed vertical structures in the rings themselves (see PIA11665).
This view looks toward the northern, sunlit side of the rings from about 8 degrees above the ringplane.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Sept. 9, 2009. The view was obtained at a distance of approximately 2.9 million kilometers (1.8 million miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 106 degrees. Image scale is 17 kilometers (11 miles) per pixel.
The Cassini Equinox Mission is a joint United States and European endeavor. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The imaging team consists of scientists from the US, England, France, and Germany. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.