- Arianespace Orders Six More Russian Soyuz-ST Carrier Rockets
- NASA Completes Anti-geyser Testing for SLS Liquid Oxygen Tank
- New Study Confirms the Presence of Dark Matter in the Inner Part of Our Galaxy
- The Sun's Activity in the 18th Century Was Similar to That Now
- Mars Reconnaissance Orbiter Completes 40,000 Orbits
- First Pair of Merging Stars Destined to Become Supernova Found
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Posted: 10 Feb 2015 04:10 AM PST
Arianespace company has ordered from Russia six more Soyuz-ST carrier rockets for launches from the Kourou space center in French Guiana in the next four years, Alexander Kirilin, CEO of the Progress Rocket and Space Center in the Volga city of Samara, said on Tuesday. "As of today a total of 10 Soyuz-ST carrier rockets, manufactured at our enterprise, were launched from French Guiana," Kirilin told TASS.
Last April the Russian enterprise entered some $400 million contract with the European company on the production and supply of seven Soyuz-ST carrier rockets for the launches from the Kourou center up to 2019. "According to contracts, a total of 13 carrier rockets [seven under last year’s contract and six more under a new one] were ordered to provide for launching campaigns up to 2019," Kirilin said. The very first contract on the use of Soyuz-ST carrier rockets from the Kourou space center was signed in 2015 and stipulated a plan of at least 50 launches. Soyuz-ST is a modification of the Russian three-stage Soyuz-2 spacecraft with a Fregat-MT booster and an ST cone adapted for launches from Kourou. The Soyuz rocket is the workhorse for Russian human space missions and has been used for that purpose longer than any other vehicle. In the 1960s it began carrying cosmonauts into space and then to the Soviet Salyut and Mir stations.
Credit: TASS
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Posted: 10 Feb 2015 03:43 AM PST
Goodbye, geysers! NASA engineers have successfully finished anti-geyser testing for the liquid oxygen tank that will help fuel the agency's new rocket, the Space Launch System, on the journey to Mars. More than 120 hours of anti-geyser testing have been completed on a full-scale, 40-foot replica of the SLS liquid oxygen tank feed system -- which will be housed in the rocket's core stage -- at one of the test stands at NASA's Marshall Space Flight Center in Huntsville, Alabama. The core stage, towering more than 200 feet tall with a diameter of 27.5 feet, will store cryogenic liquid hydrogen and liquid oxygen that will feed the vehicle’s RS-25 engines.
"Geysering occurs when heat enters the liquid oxygen feed system, causing the liquid to boil and form large oxygen gas bubbles that rapidly expel," said Chad Bryant, propulsion manager in the Stages Office at Marshall, where the SLS Program is managed for the agency. "This rapid expulsion of boiling liquid can momentarily displace large volumes of heavy liquid that crash back down, causing a damaging hammer effect on the system. "One of the largest risks with a liquid oxygen feed system of this scale is the potential of creating a geyser -- that's why this kind of testing is so important," he added. "This gives us the confidence that the operations we have in place for propellant loading, conditioning and draining will successfully suppress geysers in the system during flight vehicle operations." Those operations include using helium. The system is filled and thermally conditioned by pumping liquid oxygen up the engine feed lines and into the tank, allowing heat to escape up and out the top of the tank vent. As liquid level rises in the tank, helium is injected into the feed lines, introducing fluid circulation throughout the liquid oxygen system. This circulation is the key to maintaining uniform fluid temperature and eliminating localized propellant heating. "We've used enough liquid oxygen on the test article to fill the SLS oxygen tank eight times -- it's very thorough testing," Bryant said.
Data from the test series will be used in the development and demonstration of the liquid oxygen procedures for SLS core stage green run operations at NASA's Stennis Space Center near Bay St. Louis, Mississippi, and the first flight of the rocket from the agency's Kennedy Space Center in Florida. Green run testing of the SLS core stage is the first time the RS-25 engines are assembled into a single configuration with the core stage and fired at nearly full power. "Anti-geyser testing really provided valuable insights into system-specific behaviors and data for model validation," said Jacob Parton, anti-geyser test conductor. "Building the test article had its challenges, but testing went quite well. The NASA and Boeing teams did a fantastic job." The Boeing Company of St. Louis is the prime contractor for the SLS core stage, including its avionics. The test series began in August and wrapped up in late January. The first flight test of the SLS will feature a configuration for a 70-metric-ton (77-ton) lift capacity and carry an uncrewed Orion spacecraft beyond low-Earth orbit to test the performance of the integrated system. As the SLS evolves, it will provide an unprecedented lift capability of 130 metric tons (143 tons) to enable missions even farther into our solar system. Credit: NASA  | ||
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Posted: 09 Feb 2015 01:20 PM PST
The ubiquitous presence of dark matter in the universe is today a central tenet in modern cosmology and astrophysics. Its existence in galaxies was robustly established in the 1970s with a variety of techniques, including the measurement of the rotation speed of gas and stars, which provides a way to effectively 'weigh' the host galaxy and determine its total mass. These measurements showed that the visible matter only accounts for a fraction of the total weight, the predominant part is delivered by dark matter. Applying this technique to our own Galaxy is possible, and the existence of dark matter in the outer parts of the Milky Way is well ascertained. But up to now it has proven very difficult to establish the presence of dark matter in the innermost regions.
The diameter of our Galaxy is about 100,000 lightyears. Our Solar System is located at a distance of about 26,000 light years from the center. Coming closer to the center of our galaxy it becomes increasingly difficult to measure the rotation of gas and stars with the needed precision.
Now scientists from the Technische Universität München (TUM), Stockholm University, Universidad Autónoma de Madrid, ICTP South American Institute for Fundamental Research, São Paulo and University of Amsterdam have obtained for the first time a direct observational proof of the presence of dark matter in the innermost part the Milky Way, including at the Earth’s location and in our own ‘cosmic neighborhood’.
In a first step they created the most complete compilation of published measurements of the motion of gas and stars in the Milky Way. Then they compared the measured rotation speed with that expected under the assumption that only luminous matter exists in the Galaxy. The comparison clearly showed that the observed rotation cannot be explained unless large amounts of dark matter exist around us, and between us and the galactic center.
“We know that dark matter is needed in our Galaxy to keep the stars and gas rotating at their observed speeds,” says Dr. Miguel Pato, who conducted the analysis at TU München. “However, we still do not know what dark matter is composed of. This is one of the most important science questions of our times.”
Possessing a very strong statistical evidence, even at small galactocentric distances, the results open a new avenue for the determination of dark matter distribution inside the Galaxy. With future astronomical observations, the method will allow to measure the distribution of dark matter in our Galaxy with unprecedented precision.
“This will permit to refine the understanding of the structure and evolution of our Galaxy. And it will trigger more robust predictions for the many experiments worldwide that search for dark matter particles,” says Miguel Pato, who meanwhile moved to The Oskar Klein Centre for Cosmoparticle Physics at the Stockholm University.
Credit: tum.de
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Posted: 09 Feb 2015 12:51 PM PST
Counting sunspots over time helps in knowing the activity of our star but the two indices used by scientists disagree on dates prior to 1885. Now an international team of researchers has tried to standardise the historical results and has discovered that, contrary to what one may think, the solar activity of our times is very similar to that of other times, such as the Enlightenment. Scientists have been counting sunspots since 1610 with small telescopes. Thus it has been verified that the Sun's activity increases every eleven years, according to the interval in the growth of the number of darker and colder spots in comparison with the rest of its surface. The more spots that appear, the more luminous the surrounding areas are, and our star shines brighter.
Nonetheless, the eleven-year cycles do not always have the same intensity. The more intense peaks of the Sun's luminosity were produced in the 20th century, which experts have called the 'modern maximum'. However, an international team of scientists has reviewed the historical data and has verified that there were also elevated values in other periods.
"It has been a huge surprise to observe that in the 18th century the levels of the Sun's activity were practically the same as they are now," points out José M. Vaquero, researcher at the University of Extremadura (Spain) and co-author of the research, a review of the number of sunspots recorded in the last 400 years.
The results, published in the journal Space Science Reviews, also reveals that in other periods the opposite occurred, such as the Maunder minimum (1645-1715), when the sunspots practically disappeared and solar activity was drastically reduced.
"A proper estimate of the past and present activity of the Sun, our main source of light and heat, is crucial in understanding numerous phenomena that occur on Earth, especially to rule out the role of the Sun in global warming," says Vaquero, "but we come up against the problem that two indices or ways of calculating historical solar activity exist, and their data does not coincide when describing what happened before the 20th century".
The first index is the 'International Sunspot Number' or Wolf number, thought up by the Swiss astronomer Rudolf Wolf in 1849. It is currently the method followed by the Royal Observatory of Belgium, aided by a network of more than a hundred other astronomical observatories, the majority amateur. The second version is the 'Group Sunspot Number', and was created by US scientists Douglas V. Hoyt and K.H. Schatten in 1998.
"Unfortunately these two series only coincide in the more recent period, from approximately 1885 onwards," points out Vaquero. "In the previous periods, the US index shows a much lower level of solar activity than the European one, and this causes confusion and contradictions when the number of sunspots is used in modern research regarding the solar dynamo or the solar forcing on the Earth's climate system, for example".
The historical study of sunspots has led to the detection of several errors in the two versions. Their authors, from centres such as the Royal Observatory of Belgium, Stanford University and the US National Solar Observatory, have also been able to correct some of the detected incidents.
To carry out this research, Spain has provided information from the catalogue of sunspots from the Observatory of the University of Valencia, created between 1920 and 1928 before its fire, and data from the Astronomical Observatory of Madrid recorded between 1876 and 1986.
Credit: eurekalert.org
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Posted: 09 Feb 2015 11:39 AM PST
NASA's Mars Reconnaissance Orbiter passed a mission milestone of 40,000 orbits on Feb. 7, 2015, in its ninth year of returning information about the atmosphere, surface and subsurface of Mars, from equatorial to polar latitudes. The mission's potent science instruments and extended lifespan have revealed that Mars is a world more dynamic and diverse than was previously realized. Now in its fourth mission extension after a two-year prime mission, the orbiter is investigating seasonal and longer-term changes, including some warm-season flows that are the strongest evidence so far for liquid water on Mars today. The orbiter has returned 247 terabits of data, which is more than the combined total from every other mission that has ever departed Earth to visit another planet.
It circles Mars at an altitude of about 186 miles (300 kilometers), on a near-polar pattern, about 12 times a day. In its 40,000 orbits, the spacecraft has flown nearly twice as far as the 310 million miles (500 million kilometers) it flew during its 2006 journey from Earth to Mars.
The mission has illuminated three very different periods of Mars history. Its observations of the heavily cratered terrains of Mars, the oldest on the planet, show that different types of ancient watery environments formed water-related minerals. Some of these environments would have been more favorable for life than others.
In more recent times, water appears to have cycled as a gas between polar ice deposits and lower-latitude deposits of ice and snow. Extensive layering in ice or rock probably took at least hundreds of thousands, and possibly millions of years to form. Like ice ages on Earth, the layering is linked to cyclic changes in the tilt of the planet's rotation axis and the changing intensity of sunlight near the poles.
Mars' present climate is also dynamic, with volatile carbon dioxide and, just possibly, summertime liquid water modifying gullies and forming new streaks. With observations of new craters, avalanches and dust storms, the orbiter has shown a partially frozen world, but not frozen in time, as change continues today.
In addition to accomplishing its own science achievements, the Mars Reconnaissance Orbiter mission provides communication relay for missions on the surface of Mars and evaluates potential landing site candidates for surface missions.
Two other active NASA spacecraft are currently orbiting Mars -- Mars Odyssey since 2001, and MAVEN (Mars Atmosphere and Volatile Evolution) since last year. Two NASA rovers -- Opportunity and Curiosity -- are active on the surface. These robotic missions and others in development are paving the way for human-crew Mars missions in the 2030s and beyond as part of NASA's Journey to Mars strategy.
NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, built the orbiter and collaborates with JPL to operate it.
Credit: NASA
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Posted: 09 Feb 2015 08:00 AM PST
Astronomers using European Southern Observatory's (ESO) facilities in combination with telescopes in the Canary Islands have identified two surprisingly massive stars at the heart of the planetary nebula Henize 2-428. As they orbit each other the two stars are expected to slowly get closer and closer, and when they merge, about 700 million years from now, they will contain enough material to ignite a vast supernova explosion. The results will appear online in the journal Nature on 9 February 2015. The team of astronomers, led by Miguel Santander-García (Observatorio Astronómico Nacional, Alcalá de Henares, Spain; Instituto de Ciencia de Materiales de Madrid (CSIC), Madrid, Spain), has discovered a close pair of white dwarf stars — tiny, extremely dense stellar remnants — that have a total mass of about 1.8 times that of the Sun. This is the most massive such pair yet found and when these two stars merge in the future they will create a runaway thermonuclear explosion leading to a Type Ia supernova.
Type Ia supernovae occur when a white dwarf star acquires extra mass — either by accretion from a stellar companion or by merging with another white dwarf. Once the mass exceeds the Chandrasekhar limit the star loses its ability to support itself and starts to contract. This increases the temperature and a runaway nuclear reaction occurs and blows the star to pieces.
The team who found this massive pair actually set out to try to solve a different problem. They wanted to find out how some stars produce such strangely shaped and asymmetric nebulae late in their lives. One of the objects they studied was the unusual planetary nebula known as Henize 2-428.
“When we looked at this object’s central star with ESO’s Very Large Telescope, we found not just one but a pair of stars at the heart of this strangely lopsided glowing cloud,” says coauthor Henri Boffin from ESO.
This supports the theory that double central stars may explain the odd shapes of some of these nebulae, but an even more interesting result was to come.
"Further observations made with telescopes in the Canary Islands allowed us to determine the orbit of the two stars and deduce both the masses of the two stars and their separation. This was when the biggest surprise was revealed," reports Romano Corradi, another of the study's authors and researcher at the Instituto de Astrofísica de Canarias (Tenerife, IAC).
They found that each of the stars has a mass slightly less than that of the Sun and that they orbit each other every four hours. They are sufficiently close to one another that, according to the Einstein’s theory of general relativity, they will grow closer and closer, spiralling in due to the emission of gravitational waves, before eventually merging into a single star within the next 700 million years.
The resulting star will be so massive that nothing can then prevent it from collapsing in on itself and subsequently exploding as a supernova. "Until now, the formation of supernovae Type Ia by the merging of two white dwarfs was purely theoretical," explains David Jones, coauthor of the article and ESO Fellow at the time the data were obtained. “The pair of stars in Henize 2-428 is the real thing!”
"It's an extremely enigmatic system," concludes Santander-García. "It will have important repercussions for the study of supernovae Type Ia, which are widely used to measure astronomical distances and were key to the discovery that the expansion of the Universe is accelerating due to dark energy".
This research was presented in a paper entitled “The double-degenerate, super-Chandrasekhar nucleus of the planetary nebula Henize 2-428” by M. Santander-García et al., to appear online in the journal Nature on 9 February 2015.
The team is composed of M. Santander-García (Observatorio Astronómico Nacional, Alcalá de Henares, Spain; Instituto de Ciencia de Materiales de Madrid (CSIC), Madrid, Spain), P. Rodríguez-Gil (Instituto de Astrofísica de Canarias, La Laguna, Tenerife, Spain [IAC]; Universidad de La Laguna, Tenerife, Spain), R. L. M. Corradi (IAC; Universidad de La Laguna), D. Jones (IAC; Universidad de La Laguna), B. Miszalski (South African Astronomical Observatory, Observatory, South Africa [SAAO]), H. M. J. Boffin (ESO, Santiago, Chile), M. M. Rubio-Díez (Centro de Astrobiología, CSIC-INTA, Torrejón de Ardoz, Spain) and M. M. Kotze (SAAO).
Credit: ESO
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