Posted on by Nancy Atkinson

Black Holes Can Only Get So Big

Ultra-massive black holes, which lurk in the centers of huge galaxy clusters like the one above, seem to have an upper mass limit of 10 billion times that of the Sun. (Credit: NASA)

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Black holes are thought to exist throughout the universe, with the largest and most massive found at the centers of the largest galaxies. These supermassive black holes have been shown to have masses upwards of one billion times that of our own Sun. But an astronomer studying black holes says there’s an upper limit to how big a black hole can get. Priyamvada Natarajan, an associate professor of astronomy and physics at Yale University has shown that even the biggest of these gravitational monsters can’t keep growing forever. Instead, they appear to curb their own growth – once they accumulate about 10 billion times the mass of the Sun.

These ultra-massive black holes, found at the centers of giant elliptical galaxies in huge galaxy clusters, are the biggest in the known universe. Even the large black hole at the center of our own Milky Way galaxy is thousands of times less massive than these behemoths. But these gigantic black holes, which accumulate mass by sucking in matter from neighboring gas, dust and stars, seem unable to grow beyond this limit regardless of where – and when – they appear in the universe. “It’s not just happening today,” said Natarajan. “They shut off at every epoch in the universe.”

Natarajan’s study is the first time an upper mass limit has been derived for black holes. Natarajan used existing optical and X-ray data of these ultra-massive black holes to show that, in order for those various observations to be consistent, the black holes must essentially shut off at some point in their evolution.

Artist's conception of a black hole. Credit: U of Tel Aviv
Artist's conception of a black hole. Credit: U of Tel Aviv

One possible explanation, says Natarajan, is that the black holes eventually reach the point when they radiate so much energy as they consume their surroundings that they end up interfering with the very gas supply that feeds them, which may interrupt nearby star formation. The new findings have implications for the future study of galaxy formation, since many of the largest galaxies in the universe appear to co-evolve along with the black holes at their centers.

“Evidence has been mounting for the key role that black holes play in the process of galaxy formation,” said Natarajan. “But it now appears that they are likely the prima donnas of this space opera.”

Source: PhysOrg

Posted on by Nancy Atkinson

New Report: LHC Switch-on Fears Are Completely Unfounded

Large Hadron Collider. Credit: NY Times

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We don’t mean to beat a dead horse – both Fraser and Ian have already covered this topic quite thoroughly — but just in case anyone still has any fears about the Large Hadron Collider meaning the end of the world, a new report published today provides the most comprehensive evidence available to confirm that the LHC’s switch-on, due on Wednesday next week, poses no threat to mankind. A copy of the report is available HERE. In a nutshell, it says nature’s own cosmic rays regularly produce more powerful particle collisions than those planned within the LHC, and nothing bad has happened to Earth from those quite natural and frequent events. The LHC will be studying nature’s laws in controlled experiments. So just relax and watch the LHC rap video.

The LHC Safety Assessment Group have reviewed and updated a study first completed in 2003, which dispels fears of universe-gobbling black holes and of other possibly dangerous new forms of matter, and confirms that the switch-on will be completely safe.

The report, ‘Review of the Safety of LHC Collisions’, published in IOP Publishing’s Journal of Physics G: Nuclear and Particle Physics, proves that if particle collisions at the LHC had the power to destroy the Earth, we would never have been given the chance to exist, because regular interactions with more energetic cosmic rays would already have destroyed the Earth or other astronomical bodies.

The Safety Assessment Group compares the rates of cosmic rays that bombard Earth, other planets in our solar system, the Sun and all the other stars in our universe itself to show that hypothetical black holes or strangelets, that have raised fears in some, will in fact pose no threat.

The report also concludes that, since cosmic-ray collisions are more energetic than those in the LHC, but are incapable of producing vacuum bubbles or dangerous magnetic monopoles, we should not fear their creation by the LHC.

LHC collisions will differ from cosmic-ray collisions in that any exotic particles created will have lower velocities, but the Safety Assessment Group shows that even fast-moving black holes produced by cosmic rays would have stopped inside the Earth or other astronomical bodies. Their existence proves that any such black holes could not gobble matter at a risky rate.

As the Safety Assessment Group writes, “Each collision of a pair of protons in the LHC will release an amount of energy comparable to that of two colliding mosquitoes, so any black hole produced would be much smaller than those known to astrophysicists.” They conclude that such microscopic black holes could not grow dangerously.

As for the equally hypothetical strangelets, the review uses recent experimental measurements at the Brookhaven National Laboratory’s Relativistic Heavy-Ion Collider, New York, to prove that they will not be produced during collisions in the LHC.

Source: EurekAlert

Posted on by Nancy Atkinson

Sleek, Sexy Spacecraft to Launch Next Week

GOCE: Spacecraft of the future is here! Credit: ESA

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This has to be the sexiest looking spacecraft ever built by humankind. No, it’s not a starship or battle cruiser (although it does look a little like the Eagle spacecraft from the old television show Space: 1999). This sleek, slender, sexy, shiny and sophisticated spacecraft is an Earth-orbiting satellite that will investigate our planet’s gravitational field and map the reference shape of our planet – the geoid – with unprecedented resolution and accuracy. GOCE, or the Gravity field and steady-state Ocean Circulation Explorer is scheduled to launch on Wed. September 10 at 16:21 CEST (14:21 UTC). Why such a sleek design? As GOCE Systems Manager Michael Fehringer says, “Form follows function not only in the world of fashion! To fly low and avoid air drag, the best shape for the satellite to be is long, slender and absolutely symmetrical along the direction of flight.”

ESA’s 1 ton, 5 meter-long spacecraft will be in an extra low orbit (260 km, or 161 miles) and will experience drag from Earth’s upper atmosphere, so smooth and lean helps reduce the friction. Adding to the sleek design is that the solar panels are attached to the long body of the satellite instead of sticking out clumsily and adding to the drag. ESA has a great animation of GOCE in flight. Although the design will help, the spacecraft will need a boost to its orbit occasionally, and has state of the art ion engines.

GOCE on the launchpad. Credit: ESA
GOCE on the launchpad. Credit: ESA

GOCE will be in a sun-synchronous orbit, meaning it will be almost always be in sunlight, providing a stable thermal environment for the spacecraft.

The instruments are all placed along the axis of the satellite’s body, adding to its sleekness — check out this great animation. GOCE carries a set of six state-of-the-art high-sensitivity accelerometers to measure the components of the gravity field along all three axes. The data collected will provide a high-resolution map of the geoid and of gravitational anomalies. This will greatly improve our knowledge and understanding of the Earth’s internal structure, and will be used as a much-improved reference for ocean and climate studies, including sea-level changes, oceanic circulation and ice caps dynamics survey. Numerous applications are expected in climatology, oceanography and geophysics, as well as for geodetic and positioning activities.

Here’s an interactive feature to take a closer look at the spacecraft.

Oooo. It’s enough to make a girl purr.

Source: ESA
Also, check out Ian’s article on Astroengine

Posted on by Nancy Atkinson

Cassini Images Ring Arcs Among Two of Saturn’s Moons

Anthe and arc of ring material. Credit: NASA/JPL

NASA’s Cassini spacecraft has imaged a faint, partial ring orbiting with one small moon of Saturn, and has confirmed the presence of another partial ring orbiting with a second moon. This is further evidence that most of the planet’s small, inner moons orbit within partial or complete rings. Recent Cassini images show material, called ring arcs, extending ahead of and behind the small moons Anthe and Methone in their orbits. The new findings indicate that the gravitational influence of nearby moons on ring particles might be the deciding factor in whether an arc or complete ring is formed.

Both Anthe and Methone orbit Saturn in locations, called resonances, where the gravity of the nearby larger moon Mimas disturbs their orbits. Gravitational resonances are also responsible for many of the structures in Saturn’s magnificent rings. Mimas provides a regular gravitational tug on each moon, which causes the moons to skip forward and backward within an arc-shaped region along their orbital paths, according to Nick Cooper, a Cassini imaging team associate from Queen Mary, University of London. “When we realized that the Anthe and Methone ring arcs were very similar in appearance to the region in which the moons swing back and forth in their orbits due to their resonance with Mimas, we knew we had a possible cause-and-effect relationship,” Cooper said.
Arrows indicate the positions of Anthe, at top left, and Methone, at bottom right. Credit: NASA/JPL

Scientists believe the faint ring arcs from Anthe and Methone likely consist of material knocked off these small moons by micrometeoroid impacts. This material does not spread all the way around Saturn to form a complete ring, because of the gravitational resonance with Mimas. That interaction confines the material to a narrow region along the orbits of the moons.

This is the first detection of an arc of material near Anthe. The Methone arc was previously detected by Cassini’s Magnetospheric Imaging Instrument, and the new images confirm its presence.

Source: JPL Press Release

Posted on by Nancy Atkinson

Phoenix Probe Says Both Yes and No to Water on Mars

Phoenix's thermal and electroconductivity probe. Credit: NASA/JPL/Caltech/U of AZ

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NASA’s Phoenix Mars Lander has a fork-like conductivity probe on it’s robotic arm, and results from the instrument are presenting a bit of a quandary for mission scientists. The thermal and electroconductivity probe has sensed humidity rising and falling in the air the near the lander, but when stuck into the ground, its measurements so far indicate soil that is thoroughly and perplexingly dry. “If you have water vapor in the air, every surface exposed to that air will have water molecules adhere to it that are somewhat mobile, even at temperatures well below freezing,” said Aaron Zent, lead scientist for the probe. While Phoenix has other tools to find clues about whether water ice at the site has melted in the past, the conductivity probe is the main tool for checking for present-day soil moisture.

Preliminary results from the latest insertion of the probe’s four needles into the ground, on Wednesday and Thursday, match results from the three similar insertions in the three months since landing. “All the measurements we’ve made so far are consistent with extremely dry soil,” Zent said. “There are no indications of thin films of moisture, and this is puzzling.”

In below-freezing permafrost terrains on Earth, that thin layer of unfrozen water molecules on soil particles can grow thick enough to support microbial life. One goal for building the conductivity probe and sending it to Mars has been to see whether the permafrost terrain of the Martian arctic has detectable thin films of unfrozen water on soil particles. By gauging how electricity moves through the soil from one prong to another, the probe can detect films of water barely more than one molecule thick.

Three other sets of observations by Phoenix, in addition to the terrestrial permafrost analogy, give reasons for expecting to find thin-film moisture in the soil.

One is the conductivity probe’s own measurements of relative humidity when the probe is held up in the air. “The relative humidity transitions from near zero to near 100 percent with every day-night cycle, which suggests there’s a lot of moisture moving in and out of the soil,” Zent said.

Another is Phoenix’s confirmation of a hard layer containing water-ice about 5 centimeters (2 inches) or so beneath the surface.

Also, handling the site’s soil with the scoop on Phoenix’s robotic arm and observing the disturbed soil show that it has clumping cohesiveness when first scooped up and that this cohesiveness decreases after the scooped soil sits exposed to air for a day or two. One possible explanation for those observations could be thin-film moisture in the ground.

The Phoenix team is laying plans for a variation on the experiment of inserting the conductivity probe into the soil. The four successful insertions so far have all been into an undisturbed soil surface. The planned variation is to scoop away some soil first, so the inserted needles will reach closer to the subsurface ice layer.

“There should be some amount of unfrozen water attached to the surface of soil particles above the ice,” Zent said. “It may be too little to detect, but we haven’t finished looking yet.”

Source: Phoenix News

Posted on by Nancy Atkinson

Atlantis Rolls to the Launch Pad

Space Shuttle Atlantis on the pad. Credit: NASA

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Thursday afternoon space shuttle Atlantis rolled out to Launch Pad 39A at the Kennedy Space Center, making it’s slow 5.1 km (3.2 mile) journey along the crawlerway from the Vehicle Assembly Building. NASA mission managers cleared the shuttle’s move after a weather briefing on the status of Tropical Storm Hanna which determined the storm would remain far enough off shore to not cause any problems for the shuttle exposed out on the pad. Atlantis’ seven-member crew are set for an equipment test Friday at Kennedy in preparation for their mission to service NASA’s Hubble Space Telescope. The telescope has already rewritten the books on astronomy and will remain operational for at least another five years following the upgrades. Atlantis is targeted to launch Oct. 8 on mission STS-125. However, another hurricane, Ike, lurks out in the waters of the Atlantic, and could cause problems. But NASA is betting it won’t turn north and head for Florida.

Hubble Servicing Mission No. 4 is the only flight left on NASA’s shuttle manifest that is not headed to the International Space Station. Because Hubble is in a different orbit, Atlantis’ crew cannot seek “safe haven” on the ISS in case of any problems that might prevent a safe re-entry.

Therefore, a second shuttle, Endeavour, will head out to Launch Pad 39 B on Sept. 19, and be ready and on alert for a rescue mission. But if no rescue flight is needed, Endeavour will be moved to pad 39A and prepared for launch on the next ISS assembly mission around Nov. 10.

News Source: NASA

Posted on by Nancy Atkinson

US Astronauts May Have to Leave Space Station in 2012

A Soyuz approaches the ISS. Credit: NASA

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Because of stalled legislation that is needed to allow NASA to pay the Russian Space Agency to ferry US astronauts to the International Space Station on board the Soyuz spacecraft, the US section of the space station may have to go unmanned in at least part of 2012. In an interview with CBS’s Bill Harwood, NASA Administrator Mike Griffin said because of the of the three-year lead time needed to build Soyuz vehicles, contracts must be in place by early 2009. But because of Russia’s invasion of Georgia, Congress is unlikely to extend an exemption that allows money to be paid to Russia for high technology goods. Griffin said the problem is very serious, and new legislation would have to be approved within the next few weeks to prevent an interruption in NASA astronauts being on board the ISS.

With the exemption to the Iran-North Korea-Syria Non-Proliferation Act, NASA has been able to buy Soyuz seats for U.S. and international astronauts. While the exemption doesn’t expire until the end of 2011, Congress must approve an extension now in order for NASA to place contracts with the Russians by early next year.

Griffin said NASA has been working all year on getting the needed legislation passed. Congress has been aware of the need for a renewal of the exemption for quite some time, as Griffin talked about the importance of the exemption in his testimony during budget hearings last winter.

NASA also is counting on using the Soyuz to bridge the five-year gap between the end of shuttle operations in 2010 and the debut of the Constellation program in 2015. In addition, NASA still needs the Russian Soyuz for rescue capability for the ISS.

“Where it stands is right now,” Griffin said of the exemption, “it’s dead stalled. Because there’s no legislation which is going to come out of the Congress, other than the continuing resolution package, before they recess to go home for elections. And so right now, we’re just on dead stop. And of course, the invasion of Georgia didn’t help.”

“So here’s what will happen. The first and most obvious possibility is there won’t be any American or international partners on the space station after Dec. 31 of 2011. That’s a possibility. Another possibility is that we will be told to continue flying shuttle and we would be given extra money to do so, in which case our Ares and Orion could be kept on track and we would no longer have a dependence on Russia.

“A third possibility is we could be told to keep flying shuttle, not be given any extra money, in which case we don’t get Ares and Orion anytime soon and we still have a gap, it’s just further out in time.”

Asked if he has any optimism a waiver can be in place in time to avoid a gap in U.S. space station operations, Griffin said simply, “no.”

“My own guess is at this point we’re going to have some period in 2012 where there’s no American or international partner crew on station, that there’s only the Russians there,” he said. “That period always ends three years from when we have a contract with the Russians. So if we can get through all this by June of next year and have a contract with the Russians, then in the latter part of 2012 we can fly a Soyuz flight and restore things to normal.”

A transcript of the entire interview is available from CBS News here. In the interview, Griffin also talks about the upcoming mission to the Hubble Space Telescope and the recently announced delays for the Constellation Program.

Source: CBS News Space Place

Posted on by Nancy Atkinson

Communicating Via the Cepheid Galactic Internet

Cepheid Variable Star. Credit: Hubble Space Telescope

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If an alien species wanted to communicate with Earthlings, or any other civilization that might be out there, how might they do it? Some have proposed microwaves, neutrinos or lasers, or even moving stars around into patterns. But why wouldn’t aliens just use the internet? The Cepheid Galactic Internet, that is. A group of scientists has proposed that a sufficiently advanced civilization could use Cepheid variable stars as beacons to transmit information throughout the galaxy and beyond. These stars can be seen from long distances and, the scientists say, any technologically advanced civilization would likely observe Cepheid variables as distance markers. The group of physicists and astronomers from Hawaii and California propose that Cepheids and any other regular variable stars should be searched for signs of phase modulation and patterns which could be indicative of intentional signaling.

In their paper, the group of scientists proposes that advanced civilizations hoping to communicate would want to use a form of communication with a high data rate, just as everyone on Earth would prefer broadband for their internet. Microwaves and lasers have problems with resolution and noise, while photons or neutrinos would take an enormous amount of power to send messages long distances. And moving stars around? Well, that sounds pretty difficult if not labor intensive. So how about something akin to a T1 line that is already established? All that would need to be done is to “tickle” the star, as the scientists call it, or tweak the Cepheid, to send a message. The researchers write, “Recently, some authors have driven home the point that it is far more energetically practical for transmitting large amounts of data to place long lasting artifacts in stellar systems to which the ETI (extra terrestrial intelligence) may wish communicate information (their history for example) as intelligent life matures and becomes capable of decoding this ‘Rosetta stone.’”

By “tickling” the star, with the delivery of a relatively small amount of energy via neutrinos or other forms of power pulses at the right time could trigger the Cepheid to a specific variability, and a message could be encoded within that variability.

The researchers admit the civilization attempting this would have to be highly advanced. But if some civilization has in fact created a message and sent it via the Cepheid Galactic Internet, all we have do to is open our inbox.

Who knows, they could be on to something. They’ve even discussed their proposal with Freeman Dyson. “It may be a long shot,” they write, “but should it be correct, the payoff would be immeasurable for humanity. The beauty of this suggestion seems to be simply that the data already exists, and we need only look at the data in a new way.”

Sources: arXiv, On Orbit

Posted on by Nancy Atkinson

Where In The Universe Challenge #19

Here’s another “Where In The Universe” challenge, and in keeping with the Mission:Impossible theme from the previous post, your mission, should you choose to accept, is to identify where in the universe this image was taken. Give yourself extra points if you can name the spacecraft responsible for the image. Does everyone have their watches synchronized and secret decoder image detectors ready? It’s fairly certain this website will not self destruct in five seconds, so take your time looking at the image. As always, no peeking below before you make your guess.

This is an image of a dune field on Mars in Wirtz Crater, and yes, the white material is actually frost on the dunes. It was taken by the HiRISE Camera on the Mars Reconnaissance Orbiter. I came across this image while searching for more evidence of frost on Mars, other than what the Phoenix and Viking Landers had imaged. Just to make sure I wasn’t seeing things, I checked in with Nathan Bridges from JPL and the HiRISE Team about this image. He explains, “The white material is frost, composed of water and/or carbon dioxide. When this image was taken, it was winter in this part of Mars and it gets cold enough for water to condense out of the atmosphere and even for the atmosphere itself to freeze (the atmosphere is made of CO2) The color is approximately what you would see on Mars, but is enhanced to bring out detail.”

This image was taken on January 7, 2007 at about 3:50 in the afternoon, Mars local time, as HiRISE was 254 km (158.7 miles) above Mars’ surface. Wirtz Crater is located at -48 degrees latitude and 334.6 degrees longitude east.

For more information about this image, or to get higher resolution versions of the entire image swath, check out HiRISE’s website.

Posted on by Nancy Atkinson

Asteroid Imposters

Are some asteroid masked of their true identity?

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A frequent plot device in the old “Mission: Impossible” television show was the special masks the IMF team used so they could impersonate anyone. Viewers were often surprised to find out who ended up being an imposter. Similarly, astronomers and planetary scientists are considering that a fair amount of Near Earth Objects (NEOs) aren’t what they appear: they could be comets impersonating asteroids. Paul Abell, from the Planetary Science Institute says between five and ten percent of NEOs could be comets that are being mistaken for asteroids, and Abell is working on ways to make unmasking them a mission that’s possible.

Some NEOs could be dying comets, those that have lost most of the volatile materials that create their characteristic tails. Others could be dormant and might again display comet-like features after colliding with another object, said Abell. He is using NASA’s Infrared Telescope Facility at the Mauna Kea Observatories in Hawaii and the MMT telescope on Mount Hopkins, south of Tucson, Ariz., to uncover observational signatures that separate extinct/dormant comets from near-Earth asteroids.

This is important for a couple of reasons. First, dormant comets in near-Earth space could become supply depots to support future exploration activities with water and other materials. Second, like other NEOs, they could pose a threat to Earth if they are on a collision course with our planet. Third, they can provide data on the composition and early evolution of the solar system because they are thought to contain unmodified remnants of the primordial materials that formed the solar system.
Comet Tempel 1. Credit: NASA/U of Maryland
Unlike rocky asteroids that blast out craters when they slam into Earth, comets are structurally weak and likely to break up as they enter the atmosphere, leading to a heat and shockwave blast that would be much more devastating than the impact from an asteroid of the same size.

Low-activity, near-earth comets flashed onto the planetary-science radar screen in 2001, when NEO 2001 OG108 was discovered by the Lowell Observatory Near Earth Asteroid Search telescope. It had an orbit similar to comets coming in from the Oort Cloud, but had no cometary tail. But in early 2002 when it came closer to the sun, the heat vaporized some of the comet’s ice to create the clouds of dust and gas that make up the comet’s coma and tail. It was then reclassified as a comet.

“That’s what started me on this line of reasoning and scientific investigation,” Abell said.
By combining orbital data with spectra and the albedos (brightness) of these objects, Abell hopes to identify which are low-activity comets and where they are coming from.
“Are all these comets made of the same type of material or are they different?” Abell asked. “If they’re composed of different materials, they may have different spectral signatures, and our preliminary work on Jupiter-family comets and Halley-type comets shows that this may be true. Why is that? Is it something to do with the initial conditions of their formation regions? Or is it due to the different environments in which they spend most of their time?”

“All this is important to understanding their internal makeup, which will give us data on the material composition and evolution of the early solar system,” he added.

Source: PSI Press Release