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Hello! My name is Ian O'Neill and I've been writing for the Universe Today since December 2007. I am a solar physics doctor, but my space interests are wide-ranging. Since becoming a science writer I have been drawn to the more extreme astrophysics concepts (like black hole dynamics), high energy physics (getting excited about the LHC!) and general space colonization efforts. I am also heavily involved with the Mars Homestead project (run by the Mars Foundation), an international organization to advance our settlement concepts on Mars. I also run my own space physics blog: Astroengine.com, be sure to check it out!
The first-generation Taepoding-1 missile (Reuters)
[/caption]On Sunday, North Korea carried out its promise of launching a rocket carrying a satellite, as part of their peaceful space program. Naturally, this move has drawn massive international condemnation, prompting US President Barack Obama make a statement in Prague during his European tour. Japan has also reacted angrily, tightening sanctions against the state.
Although a rocket was launched, it was far from being a success, but it wasn’t a failure either. If the world were to listen to the official line coming out of Pyongyang, one would think Kim Jong-il has his first communications satellite in orbit, but the reality is a little more pedestrian. The Taepoding-2 rocket didn’t make it into space at all, and rather than orbiting the Earth, the communications satellite now rests at the bottom of the Pacific Ocean. However, this is a worrying development, the missile had a successful first-staging, propelling the rocket over Japanese airspace, a technical success in itself…
“North Korea broke the rules, once again, by testing a rocket that could be used for long-range missiles,” President Obama said in Prague. “It creates instability in their region, around the world. This provocation underscores the need for action, not just this afternoon in the U.N. Security Council, but in our determination to prevent the spread of these weapons.”
The North Korean rocket launch may not have successfully put a satellite into orbit, but Pyongyang’s actions have certainly sent international politics into a spin. North Korea isn’t known for its subtlety when it comes to international relations, and when you have a state that is so secretive about its nuclear ambitions (we know they have the beginnings of a nuclear weapons program after the 2006 underground nuclear bomb test), it is little wonder surrounding nations will be getting tense. In this case, Japan bore the brunt of Pyongyang’s sabre rattling, saying that if Japanese forces intercepted the rocket, the North Korea army would strike “major targets” in the country.
Ahead of Sunday’s launch, the US and allies neighbouring North Korea warned that should the launch go ahead, there would be serious political and economic consequences. Unfortunately, Jong-il’s government didn’t budge and launched anyway. Apart from causing world-wide condemnation, did the rocket actually succeed? According to one expert, the Taepoding-2 rocket launch was a “partial success.”
“It says, first of all, they had successful first staging and (were) able to control the rocket through staging,” said retired General Henry Obering, former director of the US missile defense agency. “That is a significant step forward for any missile program because often times the missiles become unstable as they go through the staging events.”
Although the first stage of the rocket launch was a success, showing that North Korea is slowly improving their long-range missile capabilities, the rest of the stages failed, causing pieces of the rocket to fall into the Sea of Japan and the Pacific Ocean.
In a post-launch statement however, the Korea Central News Agency quoted Kim Jong-il as saying “It is a striking demonstration of the might of our juche-oriented science and technology that our scientists and technicians developed both the multistage carrier rocket and the satellite with their own wisdom and technology . . . 100% and accurately put the satellite into orbit at one go.” Whether the statement actually came from Jong-il is open to debate, but the report is woefully wrong, the satellite didn’t come close to orbit.
Apart from the obvious propaganda, the launch will cause concern. The missile system is known to have an optimum range of 4200 miles, possibly with the ability to reach Hawaii and Alaska. Although the rocket failed and dropped into the Pacific, this episode clearly demonstrates the direction of North Korea’s technological advancements.
The possible path of the N. Korean launch, passing over Japan. First stage will drop into the Sea of Japan (AGI)
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Some time between April 4th-8th, North Korea will launch a communications satellite into orbit. Unsurprisingly there is huge scepticism being voiced by Japan, South Korea and the United States that the secretive military nation is in fact carrying out a test-launch of the Taepodong-2 ballistic missile system, mounting a “peaceful” satellite to disguise its real intention. If the world’s suspicions are correct, if successful, North Korea will have a means to deliver a possible nuclear strike as far as Hawaii or Alaska. Now the North Korean army has warned that if the launch is interfered with, they will attack “major targets” in Japan.
Oh dear, it sounds like it’s going to be a rough few days in the west Pacific…
A visualization of fairing separation after N. Korean rocket clears the atmosphere (Video still courtesy of Analytical Graphics, Inc. www.agi.com)North Korea’s neighbour, Japan, has warned that should the rocket start to fall toward the nation, they will attempt to intercept it using anti-missile Aegis destroyers at sea and Patriot guided-missile units on the land. This is what appears to have riled the North Koreans, prompting the Korean People’s Army (KPA) to issue a sabre-rattling statement saying, “If Japan recklessly ‘intercepts’ the DPRK’s (North’s) satellite for peaceful purposes, the KPA will mercilessly deal deadly blows not only at the already deployed intercepting means but at major targets.”
Unfortunately, North Korea has not proven itself to be a particularly “open” nation, so there is huge doubt that one of the nations in the “Axis of Evil” (a phrase coined by George W. Bush in his State of the Union Address on January 29, 2002) is simply deploying a peaceful satellite. N. Korea has long been developing chemical, biological and nuclear weapons, but any attempt by international inspectors to understand the scope of these claims have been unsuccessful. Also, previous rocket tests have provoked international outrage as they are seen as obvious attempts to intimidate neighbouring countries (principally Japan and South Korea) and demonstrated the nation is working on more sophisticated means to increase their military reach.
The satellite-carrying rocket will be directed to fly over Japan (Video still courtesy of Analytical Graphics, Inc. www.agi.com)Tensions are understandably high ahead of the launch, and some sources suggest that could be as early as Saturday (April 4th) as there are indications that fuelling activities are being carried out by Pyongyang. Spy satellite images appear to show there is indeed a satellite attached to the rocket, but the US and regional allies are under no illusions that such a launch would also test ballistic missile technology, violating the UN resolution passed in 2006 in response to the underground nuclear test and repeated missile launches. North Korea can expect severe treatment by the international community should this launch go ahead.
The US and regional allies will push for more sanctions will be put into place, further damaging international relations with North Korea. However, having signed an international space exploration treaty, North Korea appears to be hoping China and Russia will block any sanctions after launch, even though the launch directly violates the UN resolution. Russia has even urged North Korea’s neighbours not to take military action against the rocket launch.
Like most actions threatened by Pyongyang, we’ll just have to wait and see what happens, but this is certainly a volatile situation…
Just when I was getting excited about the possibility of travelling to distant worlds, scientists have uncovered a deep flaw with faster-than-light-speed travel. There appears to be a quantum limit on how fast an object can travel through space-time, regardless of whether we are able to create a bubble in space-time or not…
First off, we have no clue about how to generate enough energy to create a “bubble” in space-time. This idea was first put on a scientific grounding Michael Alcubierre from the University of Mexico in 1994, but before that was only popularized by science fiction universes such as Star Trek. However, to create this bubble we need some form of exotic matter fuel some hypothetical energy generator to output 1045 Joules (according to calculations by Richard K. Obousy and Gerald Cleaver in the paper “Putting the Warp into Warp Drive“). Physicists are not afraid of big numbers, and we are not afraid of words like “hypothetical” and “exotic”, but to put this energy in perspective, we would need to turn all of Jupiter’s mass into energy to even hope to distort space-time around an object.
This is a lot of energy.
If a sufficiently advanced human race could generate this much energy, I would argue that we would be masters of our Universe anyway, who would need warp drive when we could just as well create wormholes, star gates or access parallel universes. Yes, warp drive is science fiction, but it’s interesting to investigate this possibility and open up physical scenarios where warp drive might work. Let’s face it, anything less than light-speed travel is a real downer for our potential to travel to other star systems, so we need to keep our options open, not matter how futuristic.
The space-time bubble. Unfortunately, quantum physics may have the final word (Richard K Obousy & Gerald Cleaver, 2008)Although warp speed is highly theoretical, at least it is based on some real physics. It’s a mix of superstring and multi-dimensional theory, but warp speed seems to be possible, assuming a vast supply of energy. If we can “simply” squash the tightly curled extra-dimensions (greater than the “normal” four we live in) in front of a futuristic spacecraft and expand them behind, a bubble of stationary space will be created for the spacecraft to reside in. This way, the spaceship isn’t travelling faster than light inside the bubble, the bubble itself is zipping through the fabric of space-time, facilitating faster-than-light-speed travel. Easy.
Not so fast.
According to new research on the subject, quantum physics has something to say about our dreams of zipping through space-time faster than c. What’s more, Hawking radiation would most likely cook anything inside this theoretical space-time bubble anyway. The Universe does not want us to travel faster than the speed of light.
“On one side, an observer located at the center of a superluminal warp-drive bubble would generically experience a thermal flux of Hawking particles,” says Stefano Finazzi and co-authors from the International School for Advanced Studies in Trieste, Italy. “On the other side, such Hawking flux will be generically extremely high if the exotic matter supporting the warp drive has its origin in a quantum field satisfying some form of Quantum Inequalities.”
In short, Hawking radiation (usually associated with the radiation of energy and therefore loss of mass of evaporating black holes) will be generated, irradiating the occupants of the bubble to unimaginably high temperatures. The Hawking radiation will be generated as horizons will form at the front and rear of the bubble. Remember those big numbers physicists aren’t afraid of? Hawking radiation is predicted to roast anything inside the bubble to a possible 1030K (the maximum possible temperature, the Planck temperature, is 1032K).
Even if we could overcome this obstacle, Hawking radiation appears to be symptomatic of an even bigger problem; the space-time bubble would be unstable, on a quantum level.
“Most of all, we find that the RSET [renormalized stress-energy tensor] will exponentially grow in time close to, and on, the front wall of the superluminal bubble. Consequently, one is led to conclude that the warp-drive geometries are unstable against semiclassical back-reaction,” Finazzi adds.
However, if you wanted to create a space-time bubble for subluminal (less-than light speed) travel, no horizons form, and therefore no Hawking radiation is generated. In this case, you might not be beating the speed of light, but you do have a fast, and stable way of getting around the Universe. Unfortunately we still need “exotic” matter to create the space-time bubble in the first place…
Sources: “Semiclassical instability of dynamical warp drives,” Stefano Finazzi, Stefano Liberati, Carlos Barceló, 2009, arXiv:0904.0141v1 [gr-qc], “Investigation into Compactified Dimensions: Casimir Energies and Phenomenological Aspects,” Richard K. Obousy, 2009, arXiv:0901.3640v1 [gr-qc]
The injured long-tailed bat clings onto Discovery's external fuel tank (NASA)
[/caption]NOTE:This was the Universe Today’s contribution to April Fools Day, just in case you were wondering. However, it isn’t a joke that a bat died during a shuttle launch. Brian will forever be remembered by the Brian Bat Foundation…
On Sunday, March 15th, Space Shuttle Discovery launched from Cape Canaveral, beginning the highly successful STS-119 mission to “power up” the International Space Station (ISS). Unfortunately, a tiny stowaway was discovered clutching onto the external tank of the shuttle and refused to budge. For the whole of Sunday, NASA waited for the free-tailed bat (unofficially named “Brian” by yours truly) to fly away. Alas, Brian held on to Discovery all the way up to launch. NASA even took a photo of the shuttle as it cleared the launch tower, Brian still attached. He wasn’t frozen to the external tank (infrared images showed the bat was warm), a wildlife expert studied the last pictures of Brian, informing the space agency that Brian had in fact suffered a broken wing and was unable to fly away, even as the rockets ignited.
Although NASA was not thought to be responsible for the death of the little animal at first (calling the whole incident “sad but unavoidable”), a Florida state official is pursuing legal action against the ground staff at the Cape. According to state animal protection law, NASA may be charged with negligence, after making little effort to prevent “animal interaction” with the launchpad and apparent unwillingness to remove Brian by hand before launch. However, as investigated by the local press, there are far more animal deaths during shuttle launches than we realise…
NASA can be prosecuted under the same animal protection rules that cover Florida highways (Ian O'Neill)“First and foremost, the safety of the crew must be ensured,” said NASA spokeswoman Francis Rae, “it is unfortunate that the agency could be reprimanded over the death of an animal, but in the interest of safety and smooth launch operations, we will enact any preventative measures deemed necessary by the state.”
It turns out that NASA is a little shocked that a Florida official has decided to pursue the issue. NASA and Florida have enjoyed very close ties ever since the beginning of the Space Age and this is the first accusation of criminal negligence over the death of an animal (possibly in reaction to the huge international interest in the story). Little did the agency realise that the death of one unfortunate bat could land them in court.
“NASA enjoys total freedom of the airspace above the state, however the agency must still abide by the laws of the state, no matter how insignificant the rules may appear when compared with the endeavors of US activities in space.” — Statement by the District Attorney’s Office, Florida
According to local press, NASA can be fined for the preventable death of the bat under the same state laws that govern goods transportation (i.e. company-owned vehicles are liable if they hit endangered animal species on Florida highways). Therefore, if a truck hit a free-tailed bat on a freeway, and the driver was pulled over by a police officer, the company who owns the truck would be accountable. “This is exactly the same rule that is being applied to NASA, a free-tailed bat was killed during the operations of the shuttle. In the county’s eyes, that’s no different from a Walmart truck running over a protected animal. Like a cougar [the state animal],” reported the Orlando Sentinel.
The Ares V at the launchpad, plus artist's impression of what the anti-bat mesh would look like on launch day (NASA)Regardless of the outcome to the possible legal action, NASA has already prepared plans for an anti-bird/anti-bat mesh that will surround the launchpad after exterior inspection but before launch. This is where NASA tripped up, they performed an inspection on Saturday, March 14th, of Discovery’s external tank, but the pneumatic cranes (used to lift inspectors to the upright shuttle) were removed from the launchpad on launch day. Therefore, if NASA had to remove Brian by hand (if they knew he was injured), the Discovery launch would have been delayed further still, to wait for cranes and personnel to arrive on the scene.
This preventative measure isn’t thought to affect the remaining shuttle launches (before the shuttle is decommissioned in 2010), but the mesh will be built into the launch tower of the Constellation Program scheduled for launch in 2015 (pictured above).
“Estimates place the cost of the mesh at around $10 million,” said Rae. “However, if you factor in unforeseen project overruns and design issues, that cost could easily triple. Possibly more. We simply do not have the technology to fabricate such a large, lightweight net. It will, however, be worth it in the long-run.”
It would appear the mesh couldn’t come too soon for one NASA employee. Soon after Discovery launched on that fateful Sunday night, the Orlando Sentinel interviewed launch safety officer Aniline Lo who went into some detail about the real costs of a shuttle launch.
“…of course animals die during launches. We’ve had collisions with eagles during ascent, we’ve even found dead rats, mice and gophers left on the pad, there has also been injuries to some larger animals in the past. As the Cape is surrounded by water, it is hard to prevent alligators straying too close […] shuttle exhaust can hurt these reptiles, making them difficult to treat. It also seems the flash from the boosters cause confusion in some animals, including rabbits, actually attracting them to the launch pad at lift off. That always ends very badly.” — Aniline Lo, NASA Safety Officer
Lo then went into detail about the clean-up operation after launch. “It’s a shame, the adrenaline is pumping through your body before launch, but it is up to my team to clear up the mess which is the downer,” she said. “If you thought roadkill was bad, imagine it roasted. Hundreds of thousands of dollars post-launch could be saved in man-hours [for clean-up operations] if these animals are prevented from getting near to the rockets.”
The sad story of Brian the Bat captivated the world, but it looks like his demise was the tip of the iceberg. He was first named on the social networking site Twitter and on Astroengine.com. On launch day @DiscoveryBat appeared on Twitter, apparently tweeting from space and tweeting to this day. Even mainstream media refer to the ill-fated free-tailed bat as “Brian”. Consequently, the Brian Bat Foundation was set up to recognise animal endeavours in space. However, it appears the Foundation’s scope must now be extended to all the birds, angry alligators and rabbits on, or near, the shuttle’s launchpad during lift-off.
It was an energetic event that occurred over Tunguska, but what caused it? (Don Davis)
[/caption]Over a century ago, on June 30th, 1908 a huge explosion detonated over an unpopulated region of Russia called Tunguska. It is probably one of the most enduring mysteries of this planet. What could cause such a huge explosion in the atmosphere, with the energy of a thousand Hiroshima atomic bombs, flattening a forest the area of Luxembourg and yet leaving no crater? It is little wonder that the Tunguska event has become great material for science fiction writers; how could such a huge blast, that shook the Earth’s magnetic field and lit up the Northern Hemisphere skies for three days leave no crater and just a bunch of flattened, scorched trees?
Although there are many theories as to how the Tunguska event may have unfolded, scientists are still divided over what kind of object could have hit the Earth from space. Now a Russian scientist believes he has uncovered the best answer yet. The Earth was glanced by a large comet, that skipped off the upper atmosphere, dropping a chunk of comet material as it did so. As the comet chunk heated up as it dropped through the atmosphere, the material, packed with volatile chemicals, exploded as the biggest chemical explosion mankind had ever seen…
12,000 years ago, a large object smashed into North America, causing global destruction. Dust and ash was released into the atmosphere, triggering global cooling and possibly causing the extinction of a number of large mammals around this time. The Tunguska event was of a similar energy to that catastrophic impact, but fortunately for us, Tunguska had a benign effect on the world. It simply exploded high in the atmosphere, flattened a region of Russia and vaporized.
“Significantly, the energy of the chemical explosion is substantially lower than the kinetic energy of the body,” says Edward Drobyshevski of the Russian Academy of Sciences in St Petersburg, who has published his research into the Tunguska event. The fact that the Tunguska explosion energy is lower than what is expected of the kinetic energy of an object that hit the Earth from space is key to his work. Drobyshevski therefore concludes that the event must have been caused not by an asteroid or whole comet, it was actually caused by a fragment of comet material that fell off as the main cometary body skipped off the Earth’s upper atmosphere. This means that the Earth was hit on a tangent and the fragment dropped comparatively slowly toward the surface.
Sounds reasonable so far, but how did the fragment explode? Using our new understanding as to what chemicals comets contain, Drobyshevski surmises the fragment was rich in hydrogen peroxide. This is where the magic happened. The explosion was not due to a rapid release of kinetic energy, it was in fact a hydrogen peroxide bomb. As the fragment descended, it heated up. As the reactive chemicals in the material got hot, they explosively disassociated to form oxygen and water, ripping the fragment apart. The Tunguska event was therefore a huge chemical bomb and not a “regular” comet-hits-Earth impact.
An interesting study. Not content with dropping asteroids on our planet, the Universe has started throwing hydrogen peroxide explosives at us too. Whatever next?
Aram Chaos region of Mars as imaged by the OMEGA instrument on board ESA's Mars Express (ESA)
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The picture of Mars’ wet history is gradually becoming more comprehensive. This time, new observations by the European Space Agency’s Mars Express satellite have revealed concentrations of sulphates and ferric oxides in the 175 mile-wide (280 kilometres) Aram Chaos region, an ancient crater basin. Although the true nature of these compounds remain elusive, it could reveal past atmospheric precipitation, otherwise known as rain and snow…
Artist's impression of Mars Express (ESA)It is the mother of all planetary jigsaw puzzles, piecing together the geological and atmospheric evidence to better understand Martian history. Although we have hypothesised for some time about the presence of water in the regolith, it wasn’t until the Mars Phoenix Lander touched down in the Martian arctic in May 2008, dug a trench and detected water ice that we had proof of the existence of water on the surface. Observations made by the lander helped too, as it saw broken, regular shapes of a permafrost layer in the surrounding landscape (suggesting quantities of ice below the surface), and there is tantalizing evidence that liquid water brines may also exist at very low atmospheric pressures (with the help of perchlorate salts). It doesn’t stop there, Phoenix also confirmed that atmospheric ice may get large enough to fall as snow in arctic regions.
Now, from Mars orbit, the ESA Mars Express has used its OMEGA instrument (a.k.a. the Visible and Infrared Mineralogical Mapping Spectrometer) to map an equatorial region to gain clues about Martian history. The results beamed back to Earth are both exciting and a little peculiar.
It is well known that Mars is covered in ferric oxides, contained within the dust that blankets much of the planet. This is the compound that gives Mars its characteristic red hue. However, looking deep into the crater of Aram Chaos, there is a four-fold increase in the spectral signature of ferric oxides. This has led ESA scientists to believe this is indicative of a specific concentration mechanism. On Mars, ferric oxides are usually found with sulphates, but in this location, strong winds have blown away the lighter sulphates, leaving the ferric oxides behind, allowing the Mars Express spectrometer to measure the high concentrations.
On Earth, we commonly know ferric oxide as rust. Rust forms when there is a reaction between iron and atmospheric oxygen, facilitated by the presence of water.
“They have accumulated in dark deposits at the bottom of sulphate cliffs,” said Stephane Le Mouelic of the University of Nantes in France. This suggests that the ferric oxides have been uncovered by eolian (wind) erosion before being eroded themselves, dropping to the bottom of sulphate enriched cliffs. Driven by Martian winds, the ferric oxides went on to enrich dunes in the region.
Opportunity's blue berries, or ferric oxide deposits (NASA)It turns out the ferric oxide accumulation processes are not exclusive to Aram Chaos. According to observations by Mars rover Opportunity, there are ferric oxide concentrations in Meridiani Planum about 1000 km (600 miles) away. Also, Valles Marineris, about 3000 km (1900 miles) away appears to have similar deposits.
This is an intriguing study and it is possible that other regions will show similar accumulation processes, but are covered by other material. “OMEGA is sensitive to the first hundreds of microns of the surface. So, a layer of Martian dust just one millimeter thick will hide the signature from us,” said Marion Masse, also of the University of Nantes. Although OMEGA is restricted to hunting for ferric oxide deposits only in regions where rock is exposed due to wind action, this could be an important method to seek out how and where ferric oxides got deposited. Although scientists are keeping an open mind as to how these deposits formed, it could be due to atmospheric precipitation (rain or snow) or it could be down to volcanic ashes or glacial deposits.
Dusty debris around an old white dwarf star (NASA)
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What will happen to all the inner planets, dwarf planets, gas giants and asteroids in the Solar System when the Sun turns into a white dwarf? This question is currently being pondered by a NASA researcher who is building a model of how our Solar System might evolve as our Sun loses mass, violently turning into an electron-degenerate star. It turns out that Dr. John Debes work has some very interesting implications. As we use more precise techniques to observe existing white dwarf stars with the dusty remains of the rocky bodies that used to orbit them, the results of Debes’ model could be used as a comparison to see if any existing white dwarf stars resemble how our Sun might look in 4-5 billion years time…
A comparison of the Sun in its yellow dwarf phase and red giant phaseToday, our Sun is a healthy yellow dwarf star. If you want to be precise, it is a “G V star”. This yellow dwarf will happily burn 600 million tonnes of hydrogen per second in its core for 10 billion years, generating the light that is required to make our planet habitable. The Sun is approximately half-way through this hydrogen burning phase, so it’s OK, things aren’t going to change (for the Sun at least) for a long time yet.
But what happens then? What happens in 4-5 billion years when the supply of hydrogen runs out in the core? Although our Sun isn’t massive enough to entertain the thought of going out in a blaze of supernova glory, it will still go through an exciting, yet terrifying death. After evolving through the hydrogen-burning phase, the Sun will puff up into a huge red giant star as the hydrogen fuel becomes scarce, expanding 200 times the size it is now, probably swallowing the Earth. Helium, and then progressively heavier elements will be fused in and around the core. The Sun will never fuse carbon however, instead it will shed its outer layers forming a planetary nebula.
Once things calm down, a small sparkling jewel of a white dwarf star will remain. This tiny remnant will have a mass of around half that of our present Sun, but will be the size of the Earth. Needless to say, white dwarfs are very dense, intense gravitational pull countered not by fusion in the core (like all Main Sequence stars), but by electron degeneracy pressure.
Relative sizes of IK Pegasi A (left), IK Pegasi B (lower center; a white dwarf) and the Sun (NASA)When the Solar System reaches this phase in its evolution, what will it look like? What will become of the asteroids, gas giants, moons and rocky planets? I was very fortunate to chat with astrophysicist Dr John Debes, from NASA’s Goddard Space Flight Center, at January’s American Astronomical Society (AAS) conference in Long Beach (California) who is developing an n-body code simulating an evolving Solar System.
After the Sun has stopped hydrogen fusion in its core, it loses mass as it sheds its outer layers after the red giant phase and subsequent planetary nebula formation. It is estimated that the Sun will lose about 50% of its mass during this time, naturally affecting the Solar System as a whole. As the Sun loses mass, the outer planets (such as Jupiter) will drift outwards, increasing their orbital radii. In the simulation, Debes is very careful to ensure there is a gradual reduction in solar mass to ensure stability in the simulation.
What we are left with is an old Solar System, where little is left of the inner planets (it is likely that anything within the orbit of the Earth will have been swallowed by the Sun as it expanded through the red giant phase). Although the future white dwarf Solar System will seem very alien to present day, some things won’t change. Jupiter’s orbit might have receded with the drop in solar mass, it will remain a planetary heavyweight, causing disruption in asteroid orbits. Using known asteroid data, the motion of these chunks of rocks are allowed to evolve, and over millions of years, they may get thrown out of the Solar System, or more interestingly, pushed closer to the white dwarf. Once the whole system has settled down, resonances in the asteroid belt will become amplified; Kirkwood Gaps (caused by gravitational resonance with Jupiter) will widen, and according to Debes’ simulations, the edges of these gaps will become perturbed even more, making more asteroids available to be tidally disrupted and shredded to dust.
Artists concept of shredded asteroid around white dwarf (NASA/JPL-Caltech)The AAS conference was full of amazing research into white dwarf observations. The reason for this is that there are many white dwarf candidates out there with dusty metallic absorption lines. This means that there used to be rocky bodies orbiting these stars, but became pulverised (by tidal shear) for astronomers to analyse. These white dwarf systems can give us a clue as to what mechanisms could be supplying the white dwarfs with dusty material, even giving us a glimpse into the future of our Solar System.
“We have a physical picture for the link between planetary systems and dusty white dwarfs,” Debes said when describing his model in relation to the mysterious dusty white dwarf observations. “Dusty white dwarfs are truly a mystery! We think we know what might be going on, but we don’t have a smoking gun yet.”
However, Debes is getting close to finding a possible smoking gun, he’s basing his model on some of the key characteristics of these ancient dusty remnants to see what the Solar System could look like in billions of years time.
So, where does this dust come from? As the asteroid orbits are perturbed by Jupiter, they may get close enough to be tidally disrupted. Get too close and they will get shredded by the gravitational shear created by the steep tidal radius of the compact white dwarf. The asteroid dust then settles into the white dwarf. The presence of this dust has a very obvious signature in the absorption lines of spectroscopic data, allowing researchers to infer an accretion rate for metal-rich white dwarfs. In Debes’ model, he has set the upper limit to 1016 g/year and a lower limit to 1013 g/year, consistent with observed estimates.
Spectra of G29-38. Could this resemble the spectra of the Sun after turning into a white dwarf? (NASA/Spitzer)In his evolved Solar System model, Jupiter’s gravity controls this accretion rate, pushing asteroids toward the white dwarf and, by using a powerful supercomputer to track the perturbations and eventual shredding of known asteroids, there may be an opportunity to arrive at a profound conclusion. Debes is able to use his model to compare observations of known dusty white dwarfs with the simulated outcome of the Solar System. With reference to previous studies (in particularly Koester & Wilken, 2006 in the journal Astronomy & Astrophysics), Debes has found some similar white dwarf “Suns”.
“For G29-38, the canonical dusty white dwarf, they [Koester & Wilken] estimate a total mass of 0.55 solar masses–about what people believe the mass that our own sun will have remaining when it becomes a white dwarf,” Debes added. “But mass estimates are a bit uncertain–I’ve seen estimates ranging from 0.55-0.7 solar masses for this particular white dwarf.”
The Sun's future? The white dwarf G29-38 (NASA)“Another good candidate is a DAZ [a metal-rich white dwarf] called WD 1257+278, which does not show dust but is spot on with the mass expected for the Sun–0.54 MSun,” said Debes. “Its accretion rate is also consistent with my model predictions so far assuming an asteroid belt mass and characteristic perturbation timescale that I found in my simulations.”
Debes is continuing to make his model more and more sophisticated, but already the results are promising. Most exciting is that we may already be observing white dwarfs, like G29-38 or WD 1257+278, giving us a tantalizing glimpse of what our Solar System will look like when the Sun becomes a white dwarf star, ripping apart any remaining asteroids and planets as they stray too close to the Sun’s tidal shear. However, it also raises the question: if white dwarfs like G29-38 are being fed by the remains of tidally-blended asteroids, are there massive planets shepherding asteroids in these white dwarf systems too?
The injured long-tailed bat clings onto Discovery's external fuel tank (NASA)
[/caption]On Sunday, Space Shuttle Discovery lit up the Florida evening skies, cutting through a magnificent sunset. The STS-119 mission is set to assemble the final stages of the International Space Station’s solar array, making the outpost the second brightest object in the night sky (after the Moon). Today, Discovery successfully docked with the space station and all is set for the upcoming spacewalks.
However, space launch successes to one side, there has been an undercurrent of concern captivating the world. On Sunday, the shuttle had a stowaway attached to the external fuel tank, and although NASA was sure the little animal wouldn’t be a debris risk, the bat remained attached to the shuttle, apparently stuck in place. New details have now emerged about why the bat didn’t fly away before Discovery launched…
Brian the Bat was clearly not frozen in this IR image shortly before launch (NASA)On Sunday, there was some chat about the a bat roosting on the orange external fuel tank of the space shuttle. This isn’t such a strange occurrence, this is Florida after all, there is plenty of wildlife around Cape Canaveral, animals are bound to feature in shuttle launches every now and again. A bat has even roosted on the Shuttle before (STS-72 in 1996), only to fly away shortly before launch. Therefore, the bat discovered on Sunday morning was met with some mild curiosity and NASA was certain it would fly away before countdown.
However, during coverage of the shuttle launch, it became clear the bat was still roosting and some theories pointed at the possibility that the creature had become frozen to the tank as the cryogenic hydrogen and oxygen fuel was pumped into the external tank. However, the area where Brian was located (yes, I felt compelled to name himwhen chatting on Twitter about the situation), was not expected to drop below freezing. On watching Discovery blast off, the assumption was that Brian (then thought to be a fruit bat, he was in fact a Free-tailed bat) had long gone. How wrong we were.
This morning, images of Discovery’s launch surfaced and it would appear the bat remained attached to the fuel tank even when the shuttle passed the height of the launch tower. The bat was in it for the duration, he seemed determined to be the first bat in space!
The shuttle climbs, bat still holding on (NASA)So what happened? If the bat wasn’t frozen to the shuttle, why would he remain stuck on the external fuel tank? Surely he should have flown away when the shuttle powered up and vibrated before lift off? According to a NASA press release, the bat may have had little choice but to cling onto the shuttle. When the images were examined by a wildlife specialist, the conclusion was the bat may have had a broken wing, forcing him to hold on tight. Unfortunately, holding onto the fuel tank spelled certain doom; it is doubtful he would have been able to remain attached as the violent shaking and g-forces took hold. Although he made it as high as the launch tower, it is likely the bat dropped off and died in the searing 1400°C exhaust of the throttling boosters.
A sad reminder that small animals can be hurt and killed on the ground as we push into space. However, NASA goes through great effort to ensure there is minimal impact on birds and other animals during launches, and NASA can’t be blamed for the death of this one bat. At the end of the day, previous experience suggested the bat would simply fly away, unfortunately in this case, a broken wing was the bat’s downfall.
2009 FH fly past, only 85,000 km away from Earth (NASA)
[/caption]Another asteroid is set to make a close approach of 79,000 km according to NASA, a distance twice that of geosynchronous orbit around the Earth. Although the 15-20 metre-wide rock is not expected to cause any problems to Earth or satellites, some observers may be lucky to spot the faint light from 2009 FH as it passes.
Interestingly, this new object comes only two weeks after a larger (50 metre wide) asteroid was spotted passing the Earth at a similar distance. So it begs the question, why are we seeing so many asteroids lately?
“This asteroid flyby will be a good viewing opportunity for both professional and amateur astronomers,” said Don Yeomans from the Near-Earth Object Office at NASA’s Jet Propulsion Laboratory in Pasadena, California. “The asteroid poses no risk of impact to Earth now or for the foreseeable future.”
NASA is always very quick to point out these objects are harmless, passing the Earth at a very safe distance, often beyond the Moon’s orbit. However, 2009 FH will pass at a similar distance to the 50 metre-wide 2009 DD45 on March 2nd.
The orbit of 2009 FH (NASA JPL Small-Body Database Browser)In this case, 2009 FH will pass through the constellation of Gemini, as bright as a 14th magnitude star. Unfortunately there appears to be some fuzziness as to the time of observing opportunity. SpaceWeather.com reports that the best time to observe the asteroid has already passed (after sunset on March 17th, over North America), however, the NASA JPL news release states that close approach occurs at 5:17 am PST Wednesday morning. There is little more information available. However, check the 2009 FH ephemerides for more information.
This discovery was made by NASA’s Near Earth Object Observation Program, known as Spaceguard, to detect and track potentially hazardous asteroids that stray close to the Earth. It appears the Spaceguard team are getting better and better at spotting these chunks of rock. Although it might seem there are a lot more asteroids than before, this isn’t the case, we’re just getting better at finding them.
If there are habitable planets out there, where do we look?
[/caption]The cosmos is a very big place, how do you begin the search for exoplanets orbiting other stars? Astronomers have a few tricks up their sleeves to work out how to spot these tiny specks of distant alien worlds. Astronomers can look for the gravitational “wobble” of a star as a massive exoplanet tugs on its parent star during orbit, or more commonly, they look for the slight dimming of star light as the exoplanet passes in front of the star. In fact, the Kepler space telescope is going to peer into space, surveying 100,000 stars to do just this; not looking for large gas giants, but detecting rocky bodies that resemble large Earths with the unparalleled precision.
OK, so we have a means of finding these habitable worlds, how can we use this information to widen our search for extraterrestrial intelligence? Researchers in Israel have asked that same question, and arrived at a very logical answer. If we are to communicate with these advanced beings, perhaps we should make sure they can see us first…
The concept is simple enough. Find a star with an Earth-like transiting exoplanet (we will hopefully have a few super-Earth targets over the next three years with Kepler), aim a radio transmitter at the star and send a “Hello world!” message to the possible alien civilization living on the exoplanet. All going well (or not, depending on whether these extraterrestrials are actually friendly), we’ll get a reply from said star system in a few decades with a message saying something like “Hello world to you too!”. It would be a momentous day for interstellar communications and it would answer the one question that bugs astronomers everywhere: Are we alone in the cosmos?
So far so good, until interstellar travel becomes a reality, mankind and our new chatty alien neighbours can play a very long game of radio tag, learning more about each other as the years/decades/centuries go on (depending on how distant the extraterrestrial civilization is in the first place). But there’s a problem with this plan. What if our ET neighbours aren’t looking in our direction? What if the Sun looks like ‘just another’ star amongst the other 1010 Sun-like stars hanging out in the Milky Way? We can transmit to our hearts content, but they may never see us.
Shmuel Nussinov at Tel Aviv University in Israel asked these same questions and actually makes the search for extraterrestrial intelligence a little bit easier. With the assumption that a sufficiently advanced alien race is surveying the skies, also looking out for exoplanets orbiting other stars, they may be using the same transit method that we use to detect exoplanets. Therefore, it only seems reasonable that ET will only be able to detect Earth if we pass in front of the Sun, thus dimming it slightly for our alien neighbours to see us. If this is the case, it seems highly unlikely that any alien race will detect our existence unless they are located along a narrow angle along the ecliptic plane of our Solar System. So, if we want to open up some alien banter, we should perhaps send signals to Earth-like exoplanets spotted along the ecliptic.
Although the Earth only passes across the solar disk for 13 hours every year (as viewed by a distant observer), our star will appear to dim slightly, allowing ET to see us. Factor in the various transits of the inner Solar System planets, and our observers will see there are a few possibly habitable rocky “exoplanets” for them to transmit to. If we are already transmitting, communications can be exchanged.
