Blaming Black Holes for Gamma Ray Bursts

Artist's rendering of a black hole. Image Credit: NASA

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Black holes get a bad rap. Most people are afraid of them, and some think black holes might even destroy Earth. Now, scientists from the University of Leeds are blaming black holes for causing the most energetic and deadly outbursts in the universe: gamma ray bursts.

The conventional model for GRBs is that a narrow beam of intense radiation is released during a supernova event, as a rapidly rotating, high-mass star collapses to form a black hole. This involves plasma being heated by neutrinos in a disk of matter that forms around the black hole. A subclass of GRBs (the “short” bursts) appear to originate from a different process, possibly the merger of binary neutron stars.

But mathematicians at the University of Leeds have come up with a different explanation: the jets come directly from black holes, which can dive into nearby massive stars and devour them.

Their theory is based on recent observations by the Swift satellite which indicates that the central jet engine operates for up to 10,000 seconds – much longer than the neutrino model can explain.

The scientists believe that this is evidence for an electromagnetic origin of the jets, i.e. that the jets come directly from a rotating black hole, and that it is the magnetic stresses caused by the rotation that focus and accelerate the jet’s flow.

For the mechanism to operate the collapsing star has to be rotating extremely rapidly. This increases the duration of the star’s collapse as the gravity is opposed by strong centrifugal forces.

One particularly peculiar way of creating the right conditions involves not a collapsing star but a star invaded by its black hole companion in a binary system. The black hole acts like a parasite, diving into the normal star, spinning it with gravitational forces on its way to the star’s centre, and finally eating it from the inside.

“The neutrino model cannot explain very long gamma ray bursts and the Swift observations, as the rate at which the black hole swallows the star becomes rather low quite quickly, rendering the neutrino mechanism inefficient, but the magnetic mechanism can,” says Professor Komissarov from the School of Mathematics at the University of Leeds.

“Our knowledge of the amount of the matter that collects around the black hole and the rotation speed of the star allow us to calculate how long these long flashes will be – and the results correlate very well with observations from satellites,” he adds.

Source: EurekAlert

Space Wallpapers

Earthrise
Earthrise

Here are some amazing space wallpapers. If you want to make one of these your computer desktop wallpaper, just click on the image. That will take you to a much larger version of the image. You can then right-click on the image and choose, “Set as Desktop Background”. That will make any of these space wallpapers your desktop background.

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This is one of the most famous space photographs every taken. It’s called “Earthrise”, and it was captured by the crew of Apollo 8 as they were orbiting around the Moon. They saw the Earth rising over the Moon’s horizon and captured this amazing photograph.


Earth from space
Earth from space

NASA created this amazing wallpaper as part of its celebration for Sun-Earth day in 2008. You can see the Sun shining just outside of the photograph above.


Supernova 1054 AD
Supernova 1054 AD

Almost 1000 years ago, a star detonated in the sky as a supernova, shining brilliantly for a few days. After it faded away, it was replaced by this amazing nebula.


Star formation in the Eagle Nebula
Star formation in the Eagle Nebula

This amazing space wallpaper shows active star formation in the Eagle Nebula. These newly forming stars are blasting out huge clouds of gas and dust into space.


Saturn wallpaper
Saturn wallpaper

Here’s a beautiful image of Saturn captured by NASA’s Cassini spacecraft during a time that it was positioned over the planet’s pole.

We have got lots of image galleries here in Universe Today. Here are some Earth wallpapers, and here are some Venus wallpapers.

You can also download some cool space wallpapers from NASA’s JPL, and here are some wallpapers from Hubble.

You might also want to try listening to an episode of Astronomy Cast. Here’s an episode just about the Hubble Space Telescope.

Mount Krakatoa

Illustration of the Krakatoa eruption.

[/caption]Mount Krakatoa is a volcanic island found in Indonesia. Its most famous eruption in 1883 is one of the biggest in recorded history. You guessed it right; Krakatoa belongs to the Pacific Ring of Fire, the volatile horseshoe-shaped area bordering the Pacific Ocean.

Better known as Krakatau in Indonesia, its eruption in 1883 produced a series of tsunamis that smashed into 165 coastal villages in Java and Sumatra. 36,000 people perished when those giant waves hit. Most of those who were killed during the 1883 eruption, which lasted for two days (Aug 26 to 27), were actually victims of the tsunamis.

Some of the giant waves from that eruption, which rose up to 40 meters, managed to reach the southern part of the Arabian Peninsula, some 7,000 km away. When the 2004 Indian Ocean Tsunami (a.k.a. the 2004 Indonesian Tsunami) struck, it reminded the scientific community of the 1883 eruption because of the proximity of their points of origin.

The eruption also had a large impact on the global climate. On the average, temperature dropped by as much as 1.2ºC in the succeeding year. In the years that followed, global climates were very erratic, stabilizing only 4 years after.

Mount Krakatoa’s lava was known to be made of dacite or rhyolite. This explains the magnitude of its eruption. Generally speaking, volcanic eruptions are more explosive if their lava is composed of dacite or rhyolite. They are cooler and stickier than basalt, allowing them to accumulate pressure before being set free.

Although the 1883 eruption destroyed more than 60% of the volcanic island, a submarine eruption in 1927 produced a new island in its stead. This volcano is aptly called Anak Krakatau, which is Indonesian for “Child of Krakatoa”. Anak Krakatau’s radius is estimated to be 2 kilometers and rises up to a maximum height of 300 meters above sea level. Studies have shown in to be growing at a rate of 5 meters per year.

Before 1883, three volcanoes known as Rakata, Danan, and Perbuwatan combined to what then became Krakatoa island.

Mount Krakatoa is an example of a stratovolcano, a tall, conical volcano with multiple strata of solidified lava, tephra, as well as volcanic ash. These type of volcanoes typically have steep sides and usually erupt frequently & violently. Most of the popular eruptions have been made by stratovolcanoes. Other known stratovolcanoes are Mount St. Helens and Mount Pinatubo.

Indonesia is the country that holds the biggest number of active volcanoes, at 130. Iceland, another volcano-dotted country, holds about the same number (of volcanoes) but not all are as active as those in Indonesia.

We have some articles in Universe Today that are related to Mount Krakatoa. Here are two of them:

Mount Krakatoa articles brought to you by USGS. Here are the links:

Tired eyes? Let your ears help you learn for a change. Here are some episodes from Astronomy Cast that just might suit your taste:

Sources:
http://vulcan.wr.usgs.gov/Volcanoes/Indonesia/description_krakatau_1883_eruption.html
http://hvo.wr.usgs.gov/volcanowatch/2003/03_05_22.html

First Science Data from LRO; ‘Tantalizing’ Hints of Water

This image shows daytime and nighttime lunar temperatures recorded by Diviner. Credit: NASA/UCLA

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The Lunar Reconnaissance Orbiter has successfully completed its testing and calibration phase and is now in its science and mapping orbit of the moon. Already, the spacecraft has made significant progress in creating the most detailed atlas of the moon’s south pole, and Thursday mission scientists reported some of the early science results, including “tantalizing” hints of water at the Moon’s south pole. So far, the data returned from LRO’s seven instruments “exceed our wildest expectations,” said Richard Vondrak, LRO project scientist at NASA Goddard Space Flight Center . “We’re looking at the moon now with new eyes.”

Last Tuesday, a final maneuver put LRO 50 km (31 miles) above the Moon, closer than any previous orbiter. LRO has already proved its keen eyes, imaging fine details of the Apollo landing sites earlier this summer with the LROC, the Lunar Reconnaissance Orbiter Camera.

Coldest place in the solar system

According to the first measurements from the Diviner instrument, which has infrared radiation detectors, LRO found that temperatures at about 35 Kelvin, or -238º Celsius deep in some permanently shaded regions. Vondrak said that these bitterly cold regions at the south pole “are perhaps the coldest part of the solar system.” With such cold temperatures, volatiles like water ice could be present, preserved for billions of years.

This image shows neutron flux detections around the lunar south pole from LEND. Credit: NASA/Institute for Space Research (Moscow)
This image shows neutron flux detections around the lunar south pole from LEND. Credit: NASA/Institute for Space Research (Moscow)

And indeed, first results from LRO’s Lunar Exploration Neutron Detector, or LEND instrument found hallmarks of hydrogen—a potential marker of water— not only in deep, dark craters, but in unexpected places as well.

“What it also seems to indicate is that the hydrogen is not confined to permanently shadowed craters,” said Vondrak. “Some of the permanently shadowed craters do indeed contain hydrogen. Others, on the other hand, do not appear to have hydrogen. And in addition, there appears to be concentrations of hydrogen that are not confined to the permanently shadowed regions.”


Surface topography

This mosaic shows altitude measurements from the LOLA instrument. Credit: NASA's Goddard Space Flight Center
This mosaic shows altitude measurements from the LOLA instrument. Credit: NASA's Goddard Space Flight Center

Data from LRO’s Lunar Orbiter Laser Altimeter, or LOLA, give scientists a detailed look at the topography of the lunar south pole, shown here. Red regions are high altitude, and blue regions are low altitude.

Some of the first results have turned up fresh craters, unknown boulders, and smooth sites that would be good landing sites for future humans or robotic missions. However, most regions are filled with rough terrain, which will make in situ exploration difficult. The roughness is probably a result of the lack of atmosphere and absence of erosion from wind or water, according to David Smith, LOLA principal investigator.

Another instrument, LRO’s Cosmic Ray Telescope for the Effects of Radiation instrument is exploring the lunar radiation environment and its potential effects on humans during record high, “worst-case” cosmic ray intensities accompanying the extreme solar minimum conditions of this solar cycle, showing damaging amounts of radiation at various points.

This Mini-RF image shows radar imagery of the lunar south pole. Credit: NASA/APL/LPI
This Mini-RF image shows radar imagery of the lunar south pole. Credit: NASA/APL/LPI

The Mini RF Technology Demonstration on LRO has confirmed communications capability and produced detailed radar images of potential targets for LRO’s companion mission, LCROSS, the Lunar Crater Observation and Sensing Satellite, which will impact the moon’s south pole on Oct. 9.

LRO’s prime science mission will last a year.

“The LRO instruments, spacecraft, and ground systems continue to operate essentially flawlessly,” said Craig Tooley, LRO project manager at Goddard “The team completed the planned commissioning and calibration activities on time and also got a significant head start collecting data even before we moved to the mission’s mapping orbit.”

“There’s still an awful lot to be done,” says Michael Wargo, chief lunar scientist at NASA Headquarters in Washington, D.C. “And the maps will only get better.”

See more information, including more images and flyover videos here.

ISS Canadarm2 Grabs Resupply Ship

The station’s robotic arm attaches the unpiloted Japanese H-II Transfer Vehicle (HTV) to the Earth-facing port of the Harmony node. Credit: NASA TV


In a true display of international cooperation, American flight engineer Nicole Stott, using Canada’s Canadarm2, captured the Japanese H-II Transfer Vehicle (HTV), with help from Belgium’s Frank DeWinne and Canada’s Robert Thirsk, under the direction of Russian ISS commander Gennady Padalka. The unpiloted HTV arrived at the International Space Station Thursday and later was attached to the Harmony node at 6:26 p.m. EDT. The HTV launched on Sept. 10, and took seven days to reach the ISS so controllers could run various tests and demonstrations on its maiden voyage.

“We had an amazing time doing this,” said Stott, “and we’re so happy to have this beautiful vehicle here. We look very much forward to going in tomorrow and finding all the supplies that I’m sure you’ve stored there for us.” The crew then offered a toast to the new vehicle with their recycled water drink bags.

Stott only had 99 seconds to latch onto the cargo ship before it moved past the station and into another orbit. It came to with nine meters (30 feet) away from the lab before going into free drift so it could be grabbed by the arm.

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The crew will open up the HTV on Friday afternoon.

The HTV can bring up to six tons of supplies to the ISS, and will be used to dispose of spent equipment, used clothing, and other waste material when it later undocks and burns up the Earth’s atmosphere during re-entry.

The success of the HTV is crucial for station re-supply, especially when the space shuttle is retired.

“After the space shuttle starts to fade away, we will take over responsibility to bring stuff up to the space station. We’re really looking forward to the success of this mission,” Japanese astronaut Soichi Noguchi, who is scheduled to launch to the ISS in December, said before HTV-1’s arrival.

Source: NASA

NASA Has a Little Fun With Buzz

Buzz Lightyear returns from 15 months in the ISS. Credit: NASA. Click for larger image.

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Buzz Lightyear, that is. The action figure returned from space on Sept. 11, aboard space shuttle Discovery’s STS-128 mission after 15 months aboard the International Space Station. Word has it that Disney is quite excited about his return, and will give him a ticker-tape parade on October 2, along with some of his his space station crewmates and the original Buzz, Apollo 11’s Buzz Aldrin, at Walt Disney World in Florida.

So what was Buzz doing on the ISS?

While in space Buzz supported NASA’s education outreach program — STEM (Science, Technology, Engineering and Mathematics)–by creating a series of fun educational online outreach programs. Following his return, Disney is partnering with NASA to create a new online educational game and an online mission patch competition for school kids across America. NASA will fly the winning patch in space. In addition, NASA plans to announce on Oct. 2, 2009, the details of a new exciting educational competition that will give students the opportunity to design an experiment for the astronauts on the space station.

Source: NASA

Searching for Life As We Don’t Know It

Artist's impression of exoplanets around other stars. Credits: ESA/AOES Medialab

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When discussing the possibility of finding life on other worlds, we usually add the phrase “life – as we know it.” But we’ve been surprised at exotic forms of life even on our own world and we need figure out how life might evolve elsewhere with foreign biochemistry in alien environments. Scientists at a new interdisciplinary research institute in Austria are working to understand exotic life and how we might find it.

Traditionally, planets that might sustain life are looked for in the ‘habitable zone’, the region around a star in which Earth-like planets with carbon dioxide, water vapor and nitrogen atmospheres could maintain liquid water on their surfaces. Consequently, scientists have been looking for biomarkers produced by extraterrestrial life with metabolisms resembling the terrestrial ones, where water is used as a solvent and the building blocks of life, amino acids, are based on carbon and oxygen. However, these may not be the only conditions under which life could evolve.

The University of Vienna established a research group for Alternative Solvents as a Basis for Life Supporting Zones in (Exo-)Planetary Systems in May 2009, under the leadership of Maria Firneis.

“It is time to make a radical change in our present geocentric mindset for life as we know it on Earth,” said Dr. Johannes Leitner, from the research group. “Even though this is the only kind of life we know, it cannot be ruled out that life forms have evolved somewhere that neither rely on water nor on a carbon and oxygen based metabolism.”

One requirement for a life-supporting solvent is that it remains liquid over a large temperature range. Water is liquid between 0°C and 100°C, but other solvents exist which are liquid over more than 200 °C. Such a solvent would allow an ocean on a planet closer to the central star. The reverse scenario is also possible. A liquid ocean of ammonia could exist much further from a star. Furthermore, sulphuric acid can be found within the cloud layers of Venus and we now know that lakes of methane/ethane cover parts of the surface of the Saturnian satellite Titan.

Consequently, the discussion on potential life and the best strategies for its detection is ongoing and not only limited to exoplanets and habitable zones. The newly established research group at the University of Vienna, together with international collaborators, will investigate the properties of a range of solvents other than water, including their abundance in space, thermal and biochemical characteristics as well as their ability to support the origin and evolution of life supporting metabolisms.

“Even though most exoplanets we have discovered so far around stars are probably gas planets, it is a matter of time until smaller, Earth-size exoplanets are discovered,” said Leitner.

The research group discussed their initial investigations at the European Planetary Science Conference in Potsdam, Germany.

Source: Europlanet

Space Shuttle Flushes the Toilet for All the World To See

Shuttle with water dump. Copyright Clair Perry

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This picture is from last week; September 9, 2009 to be exact, but I still wanted to share it. I just got in touch with photographer Clair Perry from Prince Edward Island, Canada to get his permission to post the image. No, this is not a comet. Pictured is space shuttle Discovery executing a water dump. The shuttle needed to get rid of excess waste water before landing the next day, and jettisoned it overboard via the waste water dump line, creating a spectacular visual effect as sunlight hit the spraying water. This dump occurred just as the shuttle was flying over North America last week, and lots of people witnessed this “toilet flush.” Some reports indicated it was “pristine” water (the shuttle fuel cells’ by-product is water) and other reports said it was “waste water and urine” (the Bad Astronomer called it Constellation Urion). Whatever, it was pretty. NASA said this was an unusually large dump, about 150 pounds (68 kg), because new regulations say no shuttle water dumps can take place while docked to the ISS, so as not to contaminate the outdoor experiments on the Kibo lab.

See below for the spectacular entire image, which also includes the nearby ISS creating a streak in the sky. Thanks to Clair Perry for sharing his images.

Shuttle and ISS on 9/9/09.  Copyright Clair-Perry
Shuttle and ISS on 9/9/09. Copyright Clair-Perry

And if you’re worried about the water ice freezing and becoming projectiles in orbit, NASA says that while waste water usually freezes upon jettison into a cloud of tiny ice droplets, when the sun hits, the ice sublimates directly into water vapor and disperses in space.

I remember the first time I saw a shuttle water dump. It was back in 2000, and I had gotten up early, about 4:45 am, to watch the shuttle pass over. But I saw this strange sight, like something was coming off of the shuttle. I ran inside and turned on NASA TV, just in time to see a view of a golden spray shooting out of the shuttle — the sunlight hitting the water at just the right angle made it look like a shimmering gold spray. Gold, not yellow.

God Particle

The Large Hadron Collider at CERN. Credit: CERN/LHC

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When the media talks about the “god particle”, they’re really talking about a theoretical particle in physics known as the higgs boson. If reality matches the predictions made by theoretical physics, the higgs boson is the particle that gives objects mass. It explains why objects at rest tend to stay at rest and objects in motion tend to stay in motion.

One of the primary goals of the Large Hadron Collider in Switzerland is to search for the so called “god particle”. When it finally gets running, the Large Hadron Collider, or LHC, will run beams of protons around a 27 kilometer circle, slamming them together at close to the speed of light. All the kinetic energy of the protons is instantly frozen out as mass in a shower of particles. Remember Einstein’s famous E=mc2 formula? Well, you can reconfigure the equation to be m = E/c2.

The higgs boson is thought to be a very heavy particle, and so it takes a lot of energy in the collider to create particles this massive. When the LHC starts running, it will collide protons at higher and higher energies, searching for the higgs boson. If it is found, it will confirm a theorized class of particles predicted by the theory of supersymmetry. And even if the higgs boson isn’t found, it will help disprove the theory. Either way, physicists win.

The term “god particle” was coined by physicist Leon Lederman, the 1988 Nobel prize winner in physics and the director of Fermilab. He even wrote a book called the “God Particle”, where he defended the use of the term.

We have written many articles about the Higgs Boson and the Large Hadron Collider here on Universe Today. Here’s an article about how the LHC won’t create a black hole and destroy the Earth. And here’s more on Fermilab’s search for the Higgs Boson.

We have also recorded an episode of Astronomy Cast all about the higgs boson. Listen to it here, Episode 69: The Large Hadron Collider and the Search for the Higgs Boson.

What is Cherenkov Radiation?

How the CANGAROO Imaging Cherenkov Air Telescope works

Cherenkov radiation is named after the Russian physicist who first worked it out in detail, in 1934, Pavel Alekseyevich Cherenkov (he got a Nobel for his work, in 1958; because he’s Russian, it’s also sometimes called Cerenkov radiation).

Nothing’s faster than c, the speed of light … in a vacuum. In the air or water (or glass), the speed of light is slower than c. So what happens when something like a cosmic ray proton – which is moving way faster than the speed of light in air or water – hits the Earth’s atmosphere? It emits a cone of light, like the sonic boom of a supersonic plane; that light is Cherenkov radiation.

The Cherenkov radiation spectrum is continuous, and its intensity increases with frequency (up to a cutoff); that’s what gives it the eerie blue color you see in pictures of ‘swimming pool’ reactors.

Perhaps the best known astronomical use of Cherenkov radiation is in ICATs such CANGAROO (you guessed it, it’s in Australia!), H.E.S.S. (astronomers love this sort of thing, that’s a ‘tribute’ to Victor Hess, pioneer of cosmic rays studies), and VERITAS (see if you can explain the pun in that!). As a high energy gamma ray, above a few GeV, enters the atmosphere, it creates electron-positron pairs, which initiate an air shower. The shower creates a burst of Cherenkov radiation lasting a few nanoseconds, which the ICAT detects. Because Cherenkov radiation is well-understood, the bursts caused by gamma rays can be distinguished from those caused by protons; and by using several telescopes, the source ‘on the sky’ can be pinned down much better (that’s what one of the Ss in H.E.S.S. stands for, stereoscopic).

The more energetic a cosmic ray particle, the bigger the air shower it creates … so to study really energetic cosmic rays – those with energies above 10^18 ev (which is 100 million times as energetic as what the LHC will produce), which are called UHECRs (see if you can guess) – you need cosmic ray detectors spread over a huge area. That’s just what the Pierre Auger Cosmic Ray Observatory is; and its workhorse detectors are tanks of water with photomultiplier tubes in the dark (to detect the Cherenkov radiation of air shower particles).

However I think the coolest use of Cherenkov radiation in astronomy is IceCube, which detects the Cherenkov radiation produced by muons in Antarctic ice … traveling upward. These muons are produced by rare interactions of muon neutrinos with hydrogen or oxygen nuclei (in the ice), after they have traveled through the whole Earth, from the Artic (and before that perhaps a few hundred megaparsecs from some distant blazer).

ICAT: imaging Cherenkov Air Telescope
CANGAROO: Collaboration of Australia and Nippon (Japan) for a Gamma Ray Observatory in the Outback
H.E.S.S.: High Energy Stereoscopic System
VERITAS: Very Energetic Imaging Telescope Array System
UHECR: ultra-high-energy cosmic ray

This NASA webpage gives more details of how ICATs work.

Quite a few Universe Today stories are about Cherenkov radiation; for example Astronomers Observe Bizarre Blazar with Battery of Telescopes, and High Energy Gamma Rays Go Slower Than the Speed of Light?.

Examples of Astronomy Casts which include this topic: Cosmic Rays, and Gamma Ray Astronomy.

Sources:
http://en.wikipedia.org/wiki/Cherenkov_radiation
http://abyss.uoregon.edu/~js/glossary/cerenkov_radiation.html