Bruce Willis Couldn’t Save Us from Asteroid Doom

Researchers devised a formula to find the total amount of kinetic energy (E) needed in relation to the volume of the asteroid pieces (⅔πr3), their density (ρ), the clearance radius (R) which was taken as the radius of Earth plus 400 miles, the asteroid’s pre-detonation velocity (ν1) and its distance from Earth at the point of detonation (D) [physics.le.ac.uk]

According to the internet hysteria surrounding the ancient Mayan calendar, an asteroid could be on its way to wipe out the world on December 21, 2012. Obviously this is pretty unlikely — but if an asteroid really is on its way, could we take a cue from the disaster movie Armageddon in order to save the planet?

According to science research carried out by University of Leicester physics students, the answer is definitely “no.”

In the 1998 film, Bruce Willis plays an oil-drilling platform engineer who lands on the surface of an Earth-bound asteroid, drills to the centre and detonates a nuclear weapon, splitting the asteroid in half.

The two pieces of the asteroid then pass either side of Earth, saving the planet’s population from annihilation.

But the group of four MPhys students worked out that this method would not work, as we simply do not have a bomb powerful enough.

Students Ben Hall, Gregory Brown, Ashley Back and Stuart Turner found that the device would need to be about a billion times stronger than the biggest bomb ever detonated on Earth — the Soviet Union’s 50 megaton hydrogen bomb “Big Ivan” — in order to save the world from a similar sized asteroid.

To do this, they devised a formula to find the total amount of kinetic energy (E) needed in relation to the volume of the asteroid pieces (⅔πr3), their density (ρ), the clearance radius (R) which was taken as the radius of Earth plus 400 miles, the asteroid’s pre-detonation velocity (ν1) and its distance from Earth at the point of detonation (D).

Using the measurements and properties of the asteroid as stated in the film, the formula revealed that 800 trillion terajoules of energy would be required to split the asteroid in two with both pieces clearing the planet. However, the total energy output of “Big Ivan” only comes to 418,000 terajoules.

In other words, we would need to construct a bomb about a billion times stronger than the most powerful weapon ever built in order to save the world in this way.

They also found that scientists would have to detect the asteroid much earlier if we were to have any chance of splitting the asteroid in time.

On top of this, the asteroid would need to be split at almost the exact point that it could feasibly be detected at 8 billion miles.

This would leave no time for Bruce to travel to the asteroid and drill into its centre — let alone share any meaningful moments with Ben Affleck or Liv Tyler along the way.

Student Ben Hall, 22, from Haverhill, near Cambridge, said: “One possible alternative method would be moving the asteroid via propulsion methods attached to it. What is certain is that most methods would require very early detection of such an asteroid and very careful planning in deriving a solution.

“I really enjoyed the film Armageddon and up until recently never really considered the plausibility in the science behind the movie. But after watching it back I found myself being more sceptical about the film in many areas.

“I think that directors attempt to make films scientifically-accurate but find that a lot of trouble is run into in what can and cannot be done, thus leading to falsification in the science to make movies more interesting or visually appealing to the audience.

The science papers, entitled Could Bruce Willis Save the World?and Could Bruce Willis Predict the End of the World? were published in this year’s University of Leicester Journal of Special Physics Topics.

The journal is published every year, and features original short papers written by students in the final year of their four-year Master of Physics degree.

Ben, who graduated with a First last month and is due to start working at Coalville-based optical technology company Zeeko in August, added: “The module was great fun to be involved with as it allowed for us to get our creative juices flowing and attack original problems from different angles. The whole publishing and reviewing process also gave us a very good taster of what it is like to publish papers in the ‘real world’ as well as being a good simulation of the problems that arise when doing so.”

The other three group members also graduated with Firsts, and are set to start PhDs.

Course leader Dr Mervyn Roy, a lecturer at the University’s Department of Physics and Astronomy, said: “A lot of the papers published in the Journal are on subjects that are amusing, topical, or a bit off-the-wall. Our fourth years are nothing if not creative! But, to be a research physicist — in industry or academia — you need to show some imagination, to think outside the box, and this is certainly something that the module allows our students to practice.

“Most of our masters students hope to go on to careers in research where a lot of their time will be taken up with scientific publishing — writing and submitting papers, and writing and responding to referee reports.

“This is another area where the module really helps. Because Physics Special Topics is run exactly like a professional journal, the students get the chance to develop all the skills they will need when dealing with high profile journals like Nature or Science later on in life.”

How likely is an asteroid strike?

David Spiegelhalter
A report suggests that there should be 91 deaths every year from asteroid strikes, but what are the chances of that actually happening?

Buy insurance. Tick. Health check. Tick. Drive sensibly. Tick. As a general rule, we humans like to control our lives. But let’s face it, all of this caution is a complete waste of time if a huge rock from space has your name on it.

Take the recent ‘near-miss’ by the poetically-named asteroid 2012 BX34, which was only discovered two days before it sailed past within 40,000 miles (60,000km) of Earth. What if it had been heading straight for us?

A wonderful report from the US National Research Council (NRC) says that on average there should be 91 deaths per year from asteroid strikes – a remarkably precise figure and one that deserves some digging.

Try to think of when you last heard about an asteroid striking the earth. There really aren’t that many of them, or at least that many that are noticed or reported in newspapers.

One of the last significant impacts occurred on 30 June 1908, when an asteroid or comet exploded 6.2 miles (10km) above a secluded forest in Tunguska, Siberia, flattening trees over an area of 625 sq miles (1600 sq km), which surprisingly few people cared about at the time due to the remoteness of the region and the fact that there seem to have been no casualties.

Calculations suggest that if it had landed 4 hours and 47 minutes later, it would have hit St Petersburg(1), in which case people might have cared a lot, particularly as it was rather a delicate time in Russian history. According to estimates, such an airburst occurring over New York would cost \$1.19tn to insurers in property damage, not to mention causing approximately 3.2 million fatalities and 3.76 million injuries.

But that has not occurred. In fact, there are surprisingly few reports of fatalities involving asteroids. A few cars in the United States have been damaged and there was a case of a cow being killed in Valera, Venezuela in 1972 – the unfortunate animal was duly eaten and bits of the meteorite were later sold to collectors. A home outside Paris was also recently hit by an egg-shaped meteorite, but the appropriately-named Comette family were away at the time.

So how can the NRC be so precise? Well, to understand we need to understand how astronomers and statisticians think about these risks….

The population of natural Earth satellites

Our planet may frequently capture small asteroids into orbit (Image: Detlev van Ravenswaay/Science Photo Library)

Mikael Granvik, Jeremie Vaubaillonc, Robert Jedickea
Abstract
We have for the first time calculated the population characteristics of the Earth’s irregular natural satellites (NES) that are temporarily captured from the near-Earth-object (NEO) population.
The steady-state NES size-frequency and residence-time distributions were determined under the dynamical influence of all the massive bodies in the solar system (but mainly the Sun, Earth, and Moon) for NEOs of negligible mass.
To this end, we compute the NES capture probability from the NEO population as a function of the latter’s heliocentric orbital elements and combine those results with the current best estimates for the NEO size-frequency and orbital distribution.
At any given time there should be at least one NES of 1-meter diameter orbiting the Earth. The average temporarily-captured orbiter (TCO; an object that makes at least one revolution around the Earth in a co-rotating coordinate system) completes (2.88±0.82) rev around the Earth during a capture event that lasts (286±18) days. We find a small preference for capture events starting in either January or July.
Our results are consistent with the single known natural TCO, 2006 RH120, a few-meter diameter object that was captured for about a year starting in June 2006.
We estimate that about 0.1% of all meteors impacting the Earth were TCOs. (sciencedirect.com)

Observe asteroid 2005 YU55’s close approach tomorrow night!

Asteroid 2005 YU55’s close approach

There is a good opportunity to observe what is currently the largest asteroid that makes a close approach to the Earth on the evening of 8 November. Asteroid 2005 YU55 is 400 metres in size and it will make its closest approach at 11pm at a distance of 324,600km, which is 85 percent of the Earth-Moon distance (but there is no chance of it hitting the Earth!). If you have a 150mm or 200mm ‘scope then, despite the presence of the Moon and the asteroid’s low altitude in the western sky, it should still be possible to see it whizzing across the sky at 8.6 arcminutes a minute at the time of closest approach.

As darkness falls around 6pm the asteroid will be in Ophiuchus, some 24 degrees up and glowing at mag.+15.2. Two hours later it will have brightened by one and a half magnitudes and moved into neighbouring Serpens. At the time of closest approach at 11pm it will have very swiftly moved into Delphinus and brightened to mag. +12, but you will need a clear western horizon to follow it as its altitude will have slipped to 14 degrees.

 Time (8 Nov) RA Dec Mag 6pm 17h 53.56m -05° 22.5′ +15.2 7pm 18h 14.56m -00° 36.6′ +14.5 8pm 18h 38.70m +01° 31.3′ +13.8 9pm 19h 06.08m +03° 54.7′ +13.2 10pm 19h 36.46m +06° 29.0′ +12.6 11pm 20h 09.16m +09° 05.7′ +12.1 12am 20h 43.04m +11° 34.3′ +11.7

Most pristine known asteroid is denser than granite

The Rosetta spacecraft swung by asteroid 21 Lutetia on 10 July 2010

Asteroids are generally regarded as the solar system’s scrap heap, the battered bits that broke off and were left behind when the planets were forming. But the lumpy asteroid 21 Lutetia may be a whole, unbroken building block left nearly untouched since the solar system’s birth.

“We think planets were built of things like Lutetia,” says Ben Weiss of the Massachusetts Institute of Technology in Cambridge. “We’re getting a chance to see one of the building blocks of the solar system up close.”

The European spacecraft Rosetta zipped past Lutetia at 50,000 kilometres per hour in July 2010, snapping photos of a cratered world about 121 kilometres long. That makes it the second-largest asteroid ever visited by a spacecraft, next to 560-kilometre-wide Vesta.

Violent mêlée

Most of the asteroids to get visits from spacecraft are rubble piles, chunks of debris that were loosely held together by gravity. But Lutetia is so dense that it appears to have survived the violent mêlée of collisions in the early solar system intact.

“The real new thing is that it’s not a rubble pile, it’s a solid block of rock,” says Holger Sierks of the Max-Planck Institute for Solar System Research in Germany, lead author of a new paper reporting the observations. “It’s really a remnant from the early days.”

The rock has one of the highest asteroid densities ever measured, at 3.4 tonnes per cubic metre. That is denser than granite and suggests Lutetia might have heavy metals in its core.

For that to have happened, it must have melted in the past, allowing the heavy elements to sink to the centre. It could have done that if it formed within the solar system’s first million years, when there was enough radioactive aluminium-26 to melt the space rock.

Curiously, Rosetta’s optical instruments showed an unmelted surface covered in craters – providing no hint that its interior might be full of heavy metals. That hidden history of melting might explain a “seeming contradiction between the meteorite suite and the asteroids we see”, says Weiss.

Most asteroids look unmelted, but most meteorites that have fallen to Earth – thought to be fragments of asteroid cores – look like they have melted significantly. So it is possible that the melted meteorites are chips from space rocks that formed very early in the solar system, before the bulk of the radioactive aluminium – which has a half-life of 700,000 years – had decayed.

If Lutetia is a remnant from the solar system’s earliest days, what can we learn from it? Sadly, says Sierks: “We can’t really say much about the composition of the material. For that we really have to analyse in situ [with a lander] – or better, grab a piece and carry it back home for in-depth lab analysis.”
Journal reference: Science, DOI: 10.1126/science.1207325, 10.1126/science.1209389, 10.1126/science.1204062;
Planetary and Space Science, DOI: 10.1016/j.pss.2011.09.012
newscientist.com

WISE Revises Numbers of Asteroids Near Earth

This chart shows how data from NASA’s Wide-field Infrared Survey Explorer, or WISE, has led to revisions in the estimated population of near-Earth asteroids. The infrared-sensing telescope performed the most accurate survey to date of a slice of this population as part of project called NEOWISE. This allowed the science team to make new estimates of the total numbers of the objects in different size categories. NEOWISE observed more than 500 objects larger than 100-meters (330-feet) wide — what can be thought of as medium to large-size asteroids. Near-Earth asteroids smaller than this size range were not studied, and near-Earth comets will be analyzed at a later time. Asteroid sizes are not drawn to scale in the chart.

Each asteroid image represents about 100 actual objects. Near-Earth asteroids that have already been found are filled in and appear brown. An entire row of asteroid images through the blue outlines shows how many total objects were thought to exist before the NEOWISE survey. The green outlines show the reduced new estimates based on the NEOWISE data.

As the graphic reveals, only a small difference was observed in the estimated total numbers of the largest asteroids — the ones with the potential for global consequences should they impact Earth. For the medium-sized asteroids, which could still destroy a metropolitan area, new estimates predict fewer space rocks than previously thought. Details are listed below.

–For the largest asteroids, larger than 1,000 meters (3,300 feet), NEOWISE data revises the total population down to 981 from a prior estimate of about 1,000. While this is not a dramatic difference, the findings show that NASA has met an initial near-Earth asteroid goal agreed to with Congress in 1998, calling for at least 90 percent of the largest objects to be found. There are an estimated 911 objects of this size range known, which means that NASA has found 93 percent. That leaves roughly 70 of these bodies left to find.

–The NEOWISE data reveals an approximately 44 percent decline in the estimated numbers of medium-sized asteroids, which are defined as those objects between 100 meters and 1,000 meters (330 and 3,300 feet). Estimates now indicate about 19,500, where as 35,000 were thought to exist before.

–The study does not apply to objects smaller than 100 meters (330 feet), but it is estimated that there are more than a million in this size range based on previous studies.
http://www.nasa.gov

New views of an ancient asteroid

he Herschel Telescope is poised to obtain the first-ever views of target asteroid 1999 RQ36 at far infrared wavelengths before...

Using the Herschel Space Telescope, astronomers are set to obtain the first-ever images of asteroid 1999 RQ36 in far infrared light, a wavelength that the OSIRIS-REx spacecraft will not be able to see once it approaches the charcoal-black chunk of rock floating in space.
Peering through forest-fire smoke with the 61-inch telescope on Mt. Bigelow north of Tucson, Carl Hergenrother observed the asteroid known as 1999 RQ36 on its 2011 Earth-approaching orbit early last June.
The 1,900-foot (580 meter) diameter, blacker-than-coal asteroid is the destination asteroid for the U.S.’ first asteroid-sample return mission, NASA’s OSIRIS-REx.
Hergenrother, of the Lunar and Planetary Laboratory at the University of Arizona, heads the OSIRIS-REx asteroid astronomy working group of more than three dozen scientists from the U.S., Canada and Europe.
Astronomers want to get as many observations of 1999 RQ36 as possible through spring 2012, before the asteroid heads away from Earth and beyond view for ground-based and space telescopes for the next six years. By which time, the OSIRIS-REx spacecraft will have launched.
They plan observations with a network of telescopes in Arizona, the Canary Islands, Chile, Puerto Rico and space.
Observations will be challenging because the asteroid will pass no closer to Earth than 10.9 million miles (17.5 million kilometers) in early September, when it will be difficult to view against the angle of the sun….. Continue reading New views of an ancient asteroid