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[ 20041230 ]

Happy Birthday

-- to my sister, who may have been somewhere in the mob of people outside the Today Show this morning, waving signs indicating that they share Matt Lauer's birthday. The camera panned over the crowd a couple of times, but was moving too fast for me to tell. I won't reveal her age, since she prefers to think of me as having become her older brother at some point in the last decade.

Jay Manifold [8:44 PM]

[ 20041229 ]

Nope (II)

Previously unknown and impressively credentialed reader Chuck Watson writes (I've added some links and incorporated others from his message):

The risk from a Cumbre Vieja event is, IMNSHO, vastly exaggerated. Day et al used an extreme worst-case scenario. Do that with any of a number of potential sources (ie Kick-'em-Jenny off Grenada) and you get a 50-meter wave. What's the odds? A lot less than a sizeable chunk of rock landing in the Atlantic and causing a 20-meter wave. We (Mark Johnson of the University of Central Florida and I) did a study of the risks to Florida from tsunamis - scroll down to "Tsunami Risk." Datasets are on-line at the top of the page.

Some excerpts from an interview I did Monday are here. I've put some additional notes on my blog, including damage estimates. Also actually got an image of the tsunami wave itself from NOAA-17.

Things like this make me think I've got the coolest readers in the world.

Jay Manifold [9:43 PM]


The update at the end of 2004 MN4 Follow-Up, below, regrettably turns out to be an example of undue optimism, or something, on my part. Posting on the ASKC Yahoo! Group, club member John Cravens quotes Universe Today: "Scientists from the Spacewatch Observatory near Tuscon, Arizona searched back through older observations to find some images of 2004 MN4 that were captured in March, 2004. This gave them enough data to recalculate the asteroid's path, and see that it doesn't pose a threat to the planet." No wonderful technology to see it during Full Moon after all ...

Separately, ASKC "rock hunter" Richard Fredrick reports that "[2004 MN4] still has several potential impact solutions with the one in 2053 carrying a value of 1 on the Torino scale. What's nice is that it spends the next several months in a good position to be observed to the point that some of those potential impacts should be eliminated.

"We made several observations of 2004 MN4 on Monday night from Powell through partly cloudy skies with a gusty south wind, but we sent in our observations anyway without knowing that the 2029 impact possibility had gone away."

Let's hear it for pro-am observing!

Jay Manifold [9:30 PM]

Another Thing I Didn't Know Existed

So, OK, I'm grazing through the channels, and I get to CoLours, and they're showing ... "Ice Golf." Could this explain Scott Burgess's recent visit to Svalbard?

Ice golf is just that -- players bundled up for Arctic conditions, accompanied by one guy with a rifle, presumably to deal with polar bears -- lugging golf bags around a frozen wasteland. Not a blade of grass in sight. Balls are day-glo orange, but are nonetheless frequently lost, "about one ball per stroke," said one participant. Cups are small holes dug in the snow, though they have more-or-less regular-looking pins. A typical score is something like 200, partly due to high winds and partly due to the difficulty of assuming a proper stance while wearing a parka and lots of warm, layered clothing.

Add this to the sports which will someday be played on Titan ... should be interesting in one-seventh gravity and a nice, dense atmosphere.

Jay Manifold [6:00 AM]

[ 20041228 ]

Hot Fudge Tuesdae

Previously unknown/unacknowledged reader Jeff Melcher, meanwhile, asks:

If the current orbit is prograde, coplanar, and of near-yearly periodicity – and just for fun assuming the rock is as solid as a billiard ball and not squishy like Lucifer’s Hammer’s “Hot Fudge Sundae” – how hard would it be to nudge it into one of the Terra-Luna Trojan points and keep it? I mean, it is easier than hoisting the same amount of mass up from the Lunar surface?

It seems to me it would be handy to have a big chunk of stuff well outside the Earth’s – or even Moon’s – gravity well.

Judging by the information available here, which states that 2004 MN4's hyperbolic excess velocity V = 5.86 km sec-1 -- this is substantially less than the escape velocity of Earth (11.2 km sec-1), but substantially more than lunar escape velocity (2.4 km sec-1). So my quick-and-dirty answer is that moving it into high Earth orbit would certainly be easier than launching the same mass from Earth's surface, but probably not easier than launching the same mass from the Moon's surface.

Of course, if 2004 MN4 is mostly volatiles -- ices and carbon-rich compounds -- it might be worth getting for that reason alone, since the Moon has such materials only in deep craters near the poles.

Jay Manifold [4:03 PM]

Cumbre Vieja and Clathrates

Previously unknown (or, just possibly, merely previously unacknowledged) reader "Stickmaker" writes: "I wonder if the people evaluating the potential damage [from Cumbre Vieja] are taking into account the possible release of methane from seabed clathrates."

While I'm not the subject-matter expert, my reading of the literature, especially Coincident sediment slump/clathrate complexes on the U.S. Atlantic continental slope (175 kB *.pdf) and also this abstract (78 kB *.pdf; page down to end), suggests that it's the other way 'round: methane release can cause gigantic undersea landslides along continental slopes, rather than landslides causing methane release.

I don't know whether simply passing a shockwave through a clathrate can induce breakdown; the hypotheses I've encountered all involve water temperature increases, leading to melting of the upper surface of the clathrate and release of free gas and water. Of course, volcanoes have been known to generate heat ...

Anyone with more information about this is encouraged to send it in.

Jay Manifold [3:34 PM]

[ 20041227 ]

Cumbre Vieja

CNN, and probably others, are mentioning the possibility of the collapse of a volcano in the Canary Islands, apparently by way of giving Atlantic coastal dwellers a piece of the action, as it were. A story on the lamentably defunct UniSci, Highest Tsunami Wave Yet Predicted -- In The Future, gives a good overview of this scenario; excerpts:

The greatest effects are predicted to occur north, west and south of the Canaries. On the West Saharan shore, waves are expected to reach heights of 100 meters from crest to trough, and on the north coast of Brazil, waves over 40 meters high are anticipated.

Florida and the Caribbean, the final destinations in the North Atlantic to be affected by the tsunami, will have to brace themselves for receiving 50 meter high waves ... some 8 to 9 hours after the landslide.

For tsunamis striking flat-lying coastline regions such as Florida, calculating the inundation distance -- the extent to which water penetrates inland taking the form of fast-moving floods after waves break -- is crucial to assessing potential damage.

Dr. Day and his colleagues estimate inundation distances in the region of several kilometers from the coast. Accurate estimates of the scale of economic loss are yet to be made, but are thought to be in the multi-trillion-dollar range.

The paper to which the article refers, by Simon Day and Steven Ward, may be found here (warning: 1.5 MB *.pdf).

Jay Manifold [9:53 PM]

Tsunami Relief Follow-Up

I also received an e-mail from Saheli Datta, an especially important kind of previously unknown reader: one with a lengthy, detailed list of relief agencies and contact information.

UPDATE: And rightfully tied for #1 on Blogdex, the SEA-EAT blog. Like the man says, save 'em all, and let God sort 'em out.

Jay Manifold [5:41 PM]

2004 MN4 Follow-Up

Previously unknown reader (the best kind) and self-identified "potential impactee" Oliver Baker asks: "Do you happen to know whether MN4 is moving 'with us' or 'against us' around the Sun and how coplanar its orbit is with ours?"

According to NEODys, 2004 MN4's orbital inclination is only 3°20', indicating that its orbit is not only nearly coplanar with Earth's but is also prograde; if it were retrograde, inclination would be given as 176°40'.

Meanwhile, the NASA/JPL NEO page gives the velocity of impact as 12.59 km sec-1, which is rather low, only about 1.36 km sec-1 more than Earth's escape velocity, and another indication that the asteroid's approach is along an orbit which is both nearly coplanar and whose overall size is close to that of Earth's. Looking again at the NEODys page, we find that the semimajor axis is only about 1/13 of an AU smaller than Earth's orbit, and the orbital period is nearly 11 months.

And the impact probability has now dropped to 1 in 56,000, so the fun's over; we're back to Torino 0. Better luck next time. ;^)

UPDATE: I have belatedly realized the true significance of the downgrade in impact probability, namely that it occurred as a result of new observations gathered very close to a Full Moon (15:06 UT = 9:06 AM CST on Sunday the 26th), implying a much better capability for detecting dim objects (2004 MN4 is approximately 60,000 times too faint to be seen by the unaided eye) -- even in the presence of an enormous amount of scattered light in the atmosphere -- than I had realized was available. (Unless of course the new observations came from the HST, which I think unlikely.)

Jay Manifold [5:35 PM]

[ 20041226 ]

A Horrifying Coincidence

So I post about a tsunami hitting Sri Lanka, and a couple of days later, a tsunami hits Sri Lanka, among other places. A blogger version of The Lathe of Heaven?

Now for the serious part: technical details of the quake; the tsunami warning system in effect for Indonesia and Thailand, but not Bangladesh, Burma, India, Malaysia, the Maldives, or Sri Lanka; and last but certainly not least, how you can help:

UPDATE: Via Tim Blair, Chanakya is keeping a list of relief organizations.

-- as is Michele Catalano at The Command Post.

As an aside, this demonstrates that extraterrestrial threats to human life, however great they may be, are not necessarily the greatest; as regular correspondent Mike Daley keeps reminding me, super volcanoes like Toba (located on Sumatra, the nearest landmass to the earthquake) could be much worse than asteroid strikes, and are much less susceptible to technological fixes. (Yellowstone may be next, but we don't really know when.) Not coincidentally, via WolverineTom, we find When Earth Turned Bad: New Evidence Supports Terrestrial Cause Of End-Permian Mass Extinction (I blogged about the extraterrestrial hypothesis in The Greatest Disaster of All).

Jay Manifold [4:21 PM]

[ 20041225 ]


Perhaps the ultimate historical irony: over on Dienekes' Anthropology Blog, a fascinating item suggesting that the Minoan civilization may have vanished as a result of absence of water rather than a tsunami.

Jay Manifold [4:37 PM]

Torino 4!

(Ref this earlier post.) Once again, something's wrong when I'm getting this from Glenn instead of him getting it from me. One more lesson in humility. ;^)

I will nonetheless attempt to add value for my readers. Turning to the 2004 MN4 Impact Risk page, we find that the asteroid's diameter is now thought to be 440 meters and its mass 1.2 × 1011 kilograms. Assuming a sphere and applying V = 4πr³/3, we find bulk density
r = 0.37 g cm-3, well under half that of water ice, suggesting that either 2004 MN4 is far from spherical or that its composition is quite fluffy, like dry snow, implying that an airburst is likely.

In any case, the projected energy of impact is 2,200 megatons. Now we turn to one of the earliest posts on Arcturus, Thinking About the Unthinkable, where I used some handy equations from Arsenal to find that the 5-psi overpressure radius (which may be regarded for the purposes of this discussion as the Bad Day radius) for a 10-kiloton explosion is just over 900 meters. These things scale inversely as the cube of yield, so ³√(2,200/0.01) × 0.9 km = 54 kilometers or thereabouts. The area thus affected, A = πr², is over 9,000 km², which at the average population density in the US of about 31 per km² (derived from this source) would contain about 280,000 people.

At the average population density of India -- which as I explained in my earlier post, is quite a bit nearer the probable impact site -- however, this works out to nearly 2.5 million people. Yikes.

Well, it's still overwhelmingly likely to miss us. Suppose it came pretty close, though; what would it look like? Glad you asked. NEODys has it at visual magnitude +17.8 and distance 0.099 AU. At lunar distance, 0.0026 AU, it would therefore be approximately (0.099/0.0026)² = 1,400 times brighter, or magnitude +9.9, making it a binocular object; and were it to pass us at a distance of one Earth diameter (0.000085 AU) above the closest point on Earth's surface, it would shine at magnitude +2.4, as bright as the stars in the Big Dipper. Its angular motion across the sky would be around 3° per minute at closest approach, perceptible to the unaided eye.

The real story here, though, is how this will play in the media. This is just about the slowest possible news day, and a Google News search on "2004 MN4" already gets 94 hits, including this piece on the USAToday site, a Robert Roy Britt article originally appearing on Space.com.

UPDATE: Alan Brain is all over it.

So is David Appell.

FURTHER UPDATE: Yikes! Instalanche in progress! Visitors are requested to 1) generally poke around and 2) read some of the posts listed under "Important Stuff" in the left sidebar.

Also reporting substantively on 2004 MN4 are Secular Blasphemy and local KC blogger Parrish Baker's Sparrow's Fall.

Welcome both SB and Zac Hanley's Ortholog to the blogroll.

Jay Manifold [7:43 AM]

American Christmas

In the middle of the afternoon of Friday, December 20, 1968, I walked home from Miss Jordan's fourth-grade class at Lakewood Elementary, east and north through a city park, between two lakes that I would be skating on a few weeks later. At the east entrance to the park were some swings with rubber seats (something like these). One of them was quite high off the ground, and I decided to balance in it on my knees. Of course I fell out, face-first onto the asphalt. The classmate I was with (David Miller, one of four Davids in the class) wasn't quite sure what to do; I was bleeding profusely and making quite a bit of noise, and managed to make my way to the nearest house while he tagged along. By the time the people who lived there had called my parents at work, I was already recovering my composure and, if I recall correctly, walked the rest of the way home. I remember being surprised when my parents showed up -- yeah, I was hurt, but not that bad.

So the next morning found me propped up on the living-room couch, gazing intently at the television at 6:30 AM CST, with an enormously fat lip that still hurt like crazy, waiting for the launch of Apollo 8.

Two days ago, that is 36 years and one day after that launch, I went to the KSC Visitor Center with my 12-year-old nephew. One of the neater things they do is recreate the Apollo 8 liftoff, at the Apollo/Saturn V Center, in a theater whose stage is occupied by the actual, original control consoles, many of which have jackets with logos of the major contractors (all of whom, except IBM, no longer exist as independent entities) hung over the backs of the chairs. The screens light up, the countdown narration is replayed, and on three large displays hanging above the set, the biggest rocket ever launched roars to life.

The mission summary that follows, of course, omits the one thing everyone remembers about Apollo 8, the moment that redeemed that whole sorry decade. I'm not complaining; I wouldn't handle it any differently in a venue like that. One of the things I discovered about myself in the wake of 9/11 is that my commitment to a secular order is absolute. But I won't shy away from reminiscing, or from telling people why it's important.

Seven years passed; NASA failed of its promise -- which is to say that Congress and the American people did, in a bizarre act of self-betrayal. By 1975 there was no manned space program, with the meaningless exception of Apollo-Soyuz (oddly enough, to this day the only launch I have ever watched in person). And being what and where I was, I spent the latter part of the Christmas school break here.

Much might be said in mockery of Young Life, mainly that it's "evangelism lite," but I'm not going to do that, either. True, the time I spent at Castaway was nowhere near as heavy on the spiritual side of things as I had gotten used to at what was then my home church. But it was six hundred miles away in a very different and strikingly beautiful physical environment -- one day I ditched camp with one of my bunkmates, Dave Searle (where are you now?), wandering around from one ice-fishing hut to another, just talking to people, and by late afternoon had actually caught a fish, which I had somebody in the camp kitchen pack in ice, and I ate part of it the following week, at home -- all wonderfully exotic for a not-especially-well-traveled 16-year-old (Minnesotan readers are allowed to snicker at this).

What I remember most, though, were the incredibly dark skies. Well, and the cold, but I forgot that, because I was looking at Saturn.

Only with binoculars, I'm afraid; my first telescopic observation lay nearly nine months in the future. It was easy to find, because it was almost lined up with Castor and Pollux.

Just so, twenty-nine years later. Saturn has circled the Sun, and the human world has become, in many ways, a better place during the interval. I look up at Gemini and am irresistibly reminded of that earlier time; but as regular contributor Mike Daley reminds me, now we have this. In seven minutes, as I type these words, Huygens will separate from Cassini to begin its three-week journey to the surface of Titan.

One night, the staffers at Castaway Camp played, of all things, the then-popular Diana Ross song Theme from Mahogany, also known as Do You Know Where You're Going To? -- surprisingly tasteful and appropriate. There are worse ways to spend 20-hour days -- they were getting up at five in the morning to make breakfast and staying up until well past midnight working on entertainment and cleanup -- than nudging adolescents toward the straight and narrow. I once wrote, in the context of (whaddaya know) amateur astronomy, that "this is what it means to be human." And it does: no other form of life on Earth can appreciate the Universe as we can. My privilege is to be able to say, with Sir Thomas Browne: "Thus there are two books from whence I collect my divinity. Besides that written one of God, another of his servant, nature, that universal and publick manuscript, that lies expansed unto the eyes of all." (Religio Medici, §16)

And to my (in some cases) "heathen" fellow science-bloggers, who "[know] how to join and read these mystical letters," I can only say that I am privileged to have your company. You're all smarter than me, anyway. I deserve your permalinks about as much as I deserve to have been born at the right time to see this, which is to say, not at all. Thank you.

But for all my readers this Christmas, I can do no better than to quote Frank Borman: "God bless all of you - all of you on the good Earth."

Jay Manifold [12:00 AM]

[ 20041224 ]

The Ultimate Friday the 13th

-- has a 1-in-300 chance of occurring in April 2029, when asteroid 2004 MN4 has a possible position that coincides with Earth (see animation at bottom of this page). Its Torino scale rating is 2 (of a possible 10), the only object yet discovered with a rating above 0 or 1, thus qualifying it as an "event meriting concern."

Additional observations, of which there will soon be plenty -- the JPL news release at SpaceRef says "[t]his asteroid should be easily observable throughout the coming months" -- are overwhelmingly likely to eliminate the possibility of an impact. But until then, we can have some fun figuring out how bad it would be; John Antczak's AP article, appearing in the San Jose Mercury-News as Asteroid gets initial elevated risk rating, but impact unlikely, quotes JPL NEO Program Manager Don Yeomans as estimating impact energy at 1,600 megatons. Meanwhile, over on NeoDys, the impactor table specifies a date of "2029/04/13.890," that is, 21:22 UT, or 4:22 PM CDT on Fri 13 Apr 2029. Now, taking another look at the diagram in the news release, we see that the asteroid will be approaching from nearly opposite the Sun (I estimate it at 160° west of the Sun); figuring local noon to be at longitude 125° W at the moment of putative impact, the hemisphere directly beneath it will be centered on longitude 75°E or thereabouts. So if it were to hit, there's a respectable chance that it would be in the Indian Ocean.

Now, turning to this post from last March for background, we find a hypothetical 300-meter-diameter impactor coming in 5,000 km from shore and raising an 11-meter tsunami which penetrates 500-1000 meters inland. But: "Wave height should vary inversely as the square of the distance to impact and directly as the cube of impactor diameter." So for a given distance, it would be over twice as high (2004 MN4 is believed to be 400 meters across), and assuming a bullseye at 75°E, directly on the equator, we derive a wave height of 600 meters on the southwest coast of Sri Lanka, 1,000 km distant, making for a very bad night -- this would be around 2 or 3 AM Saturday morning, Colombo time.

There is another (and equally remote) possibility that is rather more intriguing than horrifying: by the looks of that animation, there's a slight chance that 2004 MN4 could hit the Moon. Since the Moon would be just a few hours past New (Apr 13, 21:40 UT; source) when the asteroid reached it, the impact would not be directly visible from Earth. But what happened next sure would; see The Mysterious Case of Crater Giordano Bruno, in which we find:

Based on the size of the crater, it must have been a one-to-three kilometer wide (a half-mile to almost 2-mile wide) asteroid that blasted Giordano Bruno into the Moon's northeast limb. Such an impact on the Earth would be "civilization threatening" -- so it is important to know if such an event happened on the Moon less than a millennium ago, Withers noted.

The impact would have launched 10 million tons of ejecta into the Earth's atmosphere in the following week, previous studies have shown. In the Meteoritics article, Withers reports his calculations on the properties of the subsequent meteor storm.

"I calculate that this would cause a week-long meteor storm comparable to the peak of the 1966 Leonids," he said. Ten million tons of rock showering the entire Earth as pieces of ejecta about a centimeter across (inch-sized fragments) for a week is equivalent to 50,000 meteors each hour.

"And they would be very bright, very easy to see, at magnitude 1 or magnitude 2. It would have been a spectacular sight to see! Everyone around the world would have had the opportunity to see the best fireworks show in history," Withers said.

I was at the poster session at the Lunar & Planetary Science Conference where Paul Withers unveiled these calculations, and recall my astonishment at what a tremendous piece of work it was. To adapt it to a scenario involving 2004 MN4, it would of course be necessary to scale things back, since the asteroid is somewhere in the range of 1/60 to 1/400 the volume of the Giordano Bruno impactor. But that's still hundreds of meteors per hour for a solid week, everywhere on Earth.

A celestial light show: the next best thing to cataclysmic destruction. Hey, I can dream, can't I?

Jay Manifold [1:05 PM]

[ 20041223 ]

What I Want for Xmas

Horseman of the Arcturcalypse Alan Henderson sends a link to this picture of a telescope so big its finderscope has a finderscope. No information on where this was taken, so I'm suggesting it's from the Ringworld, since the 'scope itself is suitably immense in scale, and that's obviously Fist-of-God Mountain in the background. ;^)

Jay Manifold [8:00 PM]

A Near Miss

Something's wrong when I find out about this stuff from Glenn instead of the other way 'round, but anyway, InstaPundit was my conduit to Robert Roy Britt's Small Asteroid Passes Between Satellites and Earth, which was more understandably my conduit to the terrific website Asteroid/Comet Connection, which I have now permalinked on the left sidebar under "Info Sites."

Of immediate interest, of course, is a page by Marco Langbroek called 2004 YD5 as meteor event, in which we learn that notwithstanding that an impact would have been in the 50-100 kiloton range, disintegration would have occurred high enough (8,000 meters or more) that damage to anything on Earth's surface would have been unlikely. I note that this object approached both out of the Sun and above Antarctica, which as I noted in Stealth Killer Comets is the most problematic trajectory for early detection and would -- as Langbroek's animation admirably illustrates -- almost certainly result in an ocean strike, potentially very bad news for anyone living along the coastlines of, or on small islands in, the south Pacific, south Atlantic, or Indian Oceans.

Jay Manifold [6:50 AM]

Books I Like

Books We Like is "a way for progressives to use their online book purchases to effect change ..." Great idea. I recommend starting with a few of these. Heh.

Jay Manifold [6:49 AM]

[ 20041220 ]

De Revolutionibus, 2004

Via Rand Simberg, a guy I'd like to meet.

UPDATE: "DarkSyd" has found another.

Jay Manifold [1:23 PM]

Large Meteor Coincides With Terror Alert in Indonesia

In what I earnestly hope will be a source of lessons learned, a large meteor entered Earth's atmosphere near Jakarta this weekend during a terror alert. A LexisNexis™ search finds an item in the Townsville (Australia) Bulletin/Sun, from which I excerpt:

The explosion could be heard in Tangerang, just west of Jakarta, the southern suburb of Depok and as far away as Bogor, some 60km south of the capital.

"It is difficult to say what it was because there were no clear timings between the sighting and the blast, but from what the various accounts said, it is very likely to have been a falling meteor," said astronomer Muji Raharto.

Indonesia's security forces have been on alert after warnings from the Australian Government last week that Islamic militants blamed for a series of deadly bombings in the country were planning an imminent attack in the run-up to Christmas.

The incident occurred at 7:30 AM local time (0030 UT) on Sunday (6:30 PM Saturday CST), which undoubtedly helped prevent confusion with a bomb blast; the heightened security, "Operation Candle," has been aimed at "places of worship, shopping malls and international hotels," according to Rachel Harvey's BBC story, Jakarta shaken by 'meteor blast'. I note that, in general, impacts are somewhat more likely to occur between local midnight and noon, since that's when any given locale is on Earth's leading side in its orbit around the Sun.

Now for a very crude attempt at determining the energy of the blast and its probable consequences had it reached the surface, or occurred just above it. The blast was heard in an area 60 km across. This is approximately the radius within which the explosions during this incident (116 kB *.pdf) were audible (by, among a million or two others, myself). The key passage:

There were two large craters found where the two trailers had been. The first trailer explosion created a swimming pool-like crater, with a "deep part" 80 feet in diameter and eight feet deep connected to a smaller crater 20 feet in diameter and six feet deep. The second trailer explosion created a crater approximately 100 feet in diameter and eight feet deep.

Information received from the Kansas City Fire Department is that the first explosion involved a trailer/magazine with a split load. One end had approximately 3,500 pounds of ammonium nitrate/fuel oil mixture. The remainder of the load was approximately 17,000 pounds of ammonium nitrate/fuel oil mix with 5 percent aluminum pellets. The second explosion was a trailer/magazine loaded with approximately 1,000 30-pound "socks" of ammonium nitrate/fuel oil mixture with 5 percent aluminum pellets.

Assuming the Jakarta meteor to have been equivalent to the first, smaller explosion described above, it equated to very roughly 10,000 kg of TNT, one-hundredth of a kiloton. Had it been an impactor, the crater would have been approximately 25 meters in diameter. A low-altitude airblast could have caused severe damage to structures in an area very roughly four hundred meters across, perhaps fifteen hectares in all. The population density of Jakarta (see Table 11.4) was 126 persons per hectare in 1990 and is certainly higher now, suggesting a death toll on the order of 2,000 had the trajectory and composition of the meteor differed ever so slightly.

Someday, we will not be so fortunate, and when it happens, we must not misattribute the event to human agency. Thousands of dead over a wide area, a mushroom cloud, perhaps a crater, during a terror alert -- the risk of impactors is as much geopolitical as physical. Longtime Arcturus readers will recognize a familiar theme, since I argued this in A Modest Proposal for an Asteroid Warning System and Asteroid Detection, Again, to which I refer newer readers for lots more background.

A final physical note: recalling KE = ½mv² and that 1 kg TNT = 4.2 MJ, we find that 0.01 kT = 4.2 × 1010 joules and, assuming an entry velocity of 40 km sec-1, an impactor mass of ~50 kg. A sphere of this mass and with r = 3 g cm-3 (source; 464 kB *.pdf) would be just over a foot in diameter!

UPDATE: This story has been mentioned (but largely without analysis) by ...

Jay Manifold [11:16 AM]

[ 20041214 ]

Geminid Dream

The sky was clear last night in KC, and since as mentioned earlier, I offered to help out down at Powell Observatory, I drove down there from work, arriving about 6:40 PM. Several ASKC members were already present and the 30" was pointed at the Pleiades, though not yet initialized. A few hardy members of the public began trickling in around 7, including several young people from an astronomy class. After a bit of fiddling around, I got a couple of more experienced ASKCers to point the 30" at Deneb, which allowed us to tell the telescope where it was, so to speak, and then move on to the Messier objects of our choice.

Since the students had mentioned learning about planetary nebulae, I slewed the 'scope to M27, which everyone liked very much; I positioned myself at the top of the ladder (which looks something like this) in order to guide people to the eyepiece in the dark. The students had also said something about galaxies, so we next went to M31. That's when I learned that if an object is close enough to the zenith, the eyepiece is so far off the ground that unless you're about 7' tall, you won't be able to reach it even standing on the top platform on tiptoe. We gave up and I went to M15 instead, which also got lots of oohs and aahs.

Then I figured we'd better move to the eastern sky, so, OK, let's look at the Crab Nebula. Somehow I'd gotten the idea that the eyepiece I was using was a 40 mm, which yields 94x in the 30", so when the 'scope was finished slewing, I was surprised to find nothing resembling M1 in the field of view. I was further surprised that lots of poking around with the hand controller (while the audience got fidgety) turned up nothing. Yeah, sometimes it's hard to find, but not this hard. So I once again got help in pointing to a guide star, in this case Aldebaran, and shortly we were looking at the Crab. Not an impressive object for first-timers, I'm afraid; it's the thought (supernova remnant, 1054 AD, pulsar, all that stuff) that counts.

And even less impressive when you're actually looking at it through a 13mm eyepiece on a telescope with a focal length of 3,800 mm or thereabouts, ie 290x or more. No wonder I couldn't find anything. The next object, the Orion Nebula, was much more popular (and with the 30", you can see more than four stars in the Trapezium!).

Meanwhile, outside, the wind was howling out of the northwest at 20-30 mph, making for a bracing experience; the wind chill was down around 18°F. The observatory director was sitting in a convertible with the top down, the seats reclined all the way, and the heat going full blast. Now that's decadent.

Meteors? Oh, yeah ... I actually saw three or four, mostly from the top of the ladder while looking out through the slit in the dome, actually a rather interesting vantage point. You can see lots of sky from there and get that looking-out-of-a-starship feeling.

Anyway, thanks for the links from Gerard Vanderleun, Rand Simberg, superhawk, and especially for the e-mail from previously unknown reader (the best kind) John Wilkerson, who in spite of finding no Geminid webcams at Arcturus seems to have had a pleasant experience.

Jay Manifold [6:30 PM]

[ 20041211 ]

Comet Maccholz

Bagged it less than half an hour ago as I type this ... got finder charts off the indispensable Heavens Above and found it, as advertised, near 54 Eridani. It is conveniently near a point below and to the right (that is, southwest) of Rigel the same distance and direction that Rigel is from Betelgeuse. It turned up almost instantly in 10x50 binoculars, and I was shortly observing it in a 10" f/5 reflector at 39x. It has a large, round coma and starlike nucleus.

While technically a naked-eye object (magnitude +5.4 as of tonight), as trumpeted in the headline on Space.com, in fact Comet Machholz requires clear, dark, transparent skies well away from city lights to pick out visually. I was able to do so, but my observing location is a friend's 10-acre property 42 miles south-southwest of downtown KC. Even 10 miles closer to town, I might not have been able to do it.

I note, however, than on the evening of Fri 7 Jan, it will be only 2° west of the Pleiades and therefore much easier to find, even from the city. The Moon will be a waning crescent, just a few days from New, and so will not interfere.

Physically, c/2004 Q2 Machholz is just under half an AU from Earth, 248 light-seconds away, or about 74 million kilometers. Its orbital period is estimated to be nearly 120,000 years, so better try to find it this time around. ;^)

Jay Manifold [11:47 PM]

[ 20041210 ]

Advantages of Left-Handedness

I'm not a lefty myself (though I am listed in The Lefty Directory, heh), but I was greatly amused by an item currently tied for #10 on Blogdex, in which we find New Scientist providing empirical evidence in support of Judges 3:15-26, or rather, part of the strategy behind it: if you need to knock off a bad guy in close combat, send a southpaw.

For those of you who forgot your Bibles this morning, the passage is here. Your supplemental reading, in connection with "the ratio of left-handers to right-handers is higher in successful sportspeople than it is in the general population," is Judges 20:16.

Jay Manifold [7:14 AM]

[ 20041207 ]

Fear No Syzygy

(Ref my all-time favorite headline in Sky & Telescope.) Another planetary alignment is in the works, but it's a very safe bet that you won't be hearing any end-of-the-age predictions from the usual suspects, because they've got no clue that it's happening. And yet: "Apart from a similar brief interval in November 2002, the planets have not been arrayed in their natural order westward from the Sun since before the invention of the telescope, and they won't be again for at least four centuries." But you just can't count on kooks to get worked up about things like this; to know about it, they'd have to, like, pay attention and learn stuff, and habits like that tend to erode kookiness.

Jay Manifold [6:30 PM]

Sedna (III)

(Ref this earlier post and its linked predecessor.) Researchers suggest stellar flyby helped form solar system, writes Lee Bowman of Scripps-Howard. Excerpts:

It's possible that some of the objects in our solar system actually formed around another star," said Scott Kenyon, an astronomer with the Smithsonian Astrophysical Observatory in Cambridge, Mass., and co-author of a study on the possible stellar flyby published Thursday in the journal Nature.

Kenyon and physicist Ben Bromley of the University of Utah came up with the simulation while trying to explain, along with many others in the field, the odd location and orbit of the bright planetoid Sedna ...

Bromley and Kenyon theorize a situation in which our sun and another star passed a relatively close 14 billion to 19 billion miles from each other just a few hundred million years after the solar system started to form. At that time, the sun was a young star surrounded by a swirling planetary disk of gas, dust and rocks, with planets newly formed from those materials.

They envision two disks shaped something like circular saw blades brushing past each other while spinning rapidly, the outer edges of each colliding and throwing debris in all directions.

According to the simulation, done on a supercomputer at NASA's Jet Propulsion Laboratory in Pasadena, Calif., the passing star's gravity would have swept up everything out to about 50 times the distance of the Earth to the Sun (93 million miles), while our own sun's gravity would have pulled some alien planetoids into its grasp.

The simulation shows there is a 5 percent to 10 percent chance that Sedna formed within our solar system and was launched into its current orbit during the near miss of the two stars. There's also a 1 percent chance that Sedna was dropped off by the passing star.

But even if Sedna wasn't born elsewhere, "there may be thousands of objects like Sedna near the edge of our solar system," Bromley said. There are a number of candidate asteroids in or near the Kuiper Belt that may have formed around the other star. The researchers now plan further simulations and surveys from telescopes to try and spot some of the adopted planets.

Bromley and Kenyon's abstract is here; and in a reprint in the SFChronicle, Dennis Overbye of the NYTimes answers my immediate question -- how to search for more?

Sedna itself has only a moderately inclined orbit, the astronomers say. A more likely candidate for an extrasolar origin is another icy wanderer, known as 2000 CR105, about half the size of Sedna, discovered out beyond Neptune in 2000. Its orbit is inclined 20 degrees to the planets.

The detection of objects with inclinations of 40 degrees or more, the authors write in Nature, "would clinch the case for extrasolar objects in the solar system."

In turn, 2000 CR105 appears to be a giant comet, 400 kilometers in diameter (compare Comet 1/P Halley at 16 × 8 × 8 km).

Jay Manifold [6:28 PM]

[ 20041206 ]

What Awaits Us On Titan

In Gamble of a lifetime for space odyssey to Titan, Robin McKie, Science Editor of The Observer, interviews John Zarnecki, who paints an enchanting picture:

As the probe's batteries start to fade, Huygens will drop on to Titan's surface and Zarnecki's science package will send back its data, including indications of whether the spacecraft is floating, bouncing or squelching. Zarnecki is clear about his hopes, however. He wants a splash-down, giving his team the honour of finding the second world, after Earth, with an ocean on its surface. He has also calculated that, if such seas of methane and ethane exist, they will be swept by giant, slow-moving waves - a paradise for surfers.

'We will probably only have a few minutes' power left by the time we settle on the surface, so I would like to pick up readings showing that we are bobbing up and down on a sea,' he said. 'Then, just as the batteries are beginning to fail, the cameras will spot a 100-foot waves rushing toward the probe. Our instruments will show the craft is pitching over, then everything will go black. It would be a great way to go.'

Indeed. Thirty-nine days and counting!

Jay Manifold [8:14 PM]

In Answer to Stephen Wright's Famous Question

Namely: "Why is the alphabet in that order? Is it because of that song?"

Er, no. But what is that song? According to Author gazes whimsically at the stars, a book review by Susan Skorupa appearing in the Reno Gazette-Journal

The first song many of us learned as children - the ABC song - is sung to the same tune as "Twinkle, Twinkle Little Star," Reed reminds readers. It's derived from a 17th-century French folk song.

And the alphabet's a lot older than that; QED. In other news, while I don't think of myself as especially tone-deaf, in the 40-something years since I learned the alphabet, I never realized they were the same tune.

Jay Manifold [8:13 PM]

Transit of Venus Follow-Up

(For my experience, see this post of six months back.) In Appointment with Venus, the Guardian charmingly recounts the efforts of over 1,500 amateur observers to measure the size of Earth's orbit the old-fashioned way. In the event, they were only 0.007% off, and their error bars beat the spread, as it were. Read the whole thing (it's only three short paragraphs).

Jay Manifold [8:12 PM]

Nothing New Under the Sun

Thanks to Rand Simberg for pointing to The Islamization of Europe?, by David Pryce-Jones. This passage in particular caught my eye:

... is it any wonder that some Europeans are switching sides, so as to be on the winning one? The sheer élan and cultural confidence displayed by Islamist spokesmen may have something to do with the fact that every year, thousands of people all over Europe convert to Islam. Some of these converts, from Britain, France, and Germany, taking the direct route from words to action, have gone on to play a disproportionate role in terrorism and Islamist militancy. Thus, at a rally organized in London last year by a radical offshoot of the Muslim Brotherhood, a high proportion of demonstrators were clearly not of Middle Eastern origin. At a recent trial in Cairo in which three British citizens were condemned to prison for subversion and intended terrorism, two were English-born, with English names. They were led away shouting defiance of the West.

And, you know, it ain't the first time:

Many a university teacher during the 1930's has seen English and American students return from the Continent uncertain whether they were communists or Nazis and certain only that they hated Western liberal civilization.

It may be that the West is fated, by its very cultural plenitude, to host some minimal number of such parasites. And our survival may depend not only on whether they are dealt with, but how: when attracted but not committed to such a dread cause, to be warned; where vocally supportive of it but still open to moral suasion, to be led away from an inclination to terror; and finally to be held fully responsible for any material support or direct act carried out as part of their dark fantasy of conquest.

Jay Manifold [7:07 PM]

[ 20041205 ]

Astrophotography as Art (II)

(Ref this earlier post) Artist's Statement, written by Doug Zubenel, reproduced by permission:

In the early 60's, I marveled over the photographs of galaxies in the end credits of "The Outer Limits" episodes. Shortly after witnessing a meteor shower in Nov. 1968, I began to photograph celestial events. The years since have broadened my work to include weather, landscape and surreal imagery.

The purpose of these images is to emphasize the connectedness I sense between the celestial realm and the environment I move in. I perceive light as a messenger that passes through the portal of time and whispers, in the language of awe and beauty, words from another world ... words best expressed by the Psalmist: "The heavens declare the glory of God; the skies proclaim the work of his hands. Day after day they pour forth speech; night after night they display knowledge. There is no speech or language where their voice is not heard."

The photographs were made using a technique I created in 1982. There was no computer manipulation or use of computers in any way in making these images. Everything you see in the print comes directly from a simple, original negative or transparency.

The medium of photography as an art form holds more possibilities for me today than ever before. In recent years, I have started giving more thought to the concept of the photographic image as a visual metaphor. To perfectly render on film what is there requires only a technician. It is the artist who uses technique not as an end but as a means to the end of communicating an idea, challenging paradigms, stirring emotions or inspiring the spirit. The language of light, with its visual eloquence, best realizes these ends for me when the art is possessed of truth. I seek not to discover truth, but to communicate truth already revealed; solid, unchanging and universal. My images work best for me when I can successfully abstract or recontextualize a subject so that it is transformed into a metaphor. Abstraction devoid of meaning is or communicates a lie -- all things have meaning. Sometimes the image precedes the idea or meaning -- a kind of visual prophecy -- and such was the case for the photos "Denial" and "Transcience."

"Messengers of Light" will continue on display at the Cube at Beco, 1922 Baltimore, KC MO, through at least the first week of January. Doug's photographs typically include celestial objects like comets Hale-Bopp and Hyakutake, with foreground terrestrial elements like the Monument Rocks/Chalk Pyramids. An astonishing blend of land and sky.

Jay Manifold [4:28 PM]

[ 20041203 ]

Moon to Occult Jupiter Next Tuesday Morning

The full story is over on Space.com; for locals, disappearance occurs at 2:49 AM CST, with the crescent Moon just 5° above the horizon, a little south of due east. Reappearance is just under an hour later, with the Moon 16° up in the east-southeast; using YourSky, I found that the first-magnitude star Spica will be between the Moon and the horizon when Jupiter reappears -- the link notes that lunar occultations have indicated that Spica is a five-sun system. On this occasion, however, the Moon will pass 3.1° north (page down to see December's events).

The graphic shows that Callisto will disappear (and reappear) first, followed by Ganymede, Jupiter itself, and Europa. A bit of tinkering with this Jovian satellite simulator, however, indicates that the actual order as seen from KC will be Callisto, Ganymede, Europa (just barely), Jupiter, Io.

Obviously, getting up at 2 AM or thereabouts is for diehards. The local weather forecast as of now is for mostly-clear skies and temperatures down around freezing. I'll probably go for it if it looks like there's any chance of seeing anything, though, because the next one of these visible in most of North America isn't until 2026.

Jay Manifold [3:00 PM]

[ 20041202 ]

Best Meteor Shower of 2004 Coming Up

The current director of Powell Observatory, David Young, has announced that he will open the observatory on the evening of Monday the 13th, the peak of the Geminid meteor shower. It's not that people can watch meteors through a 30" telescope, but that events like that tend to attract the public, and the ASKC collects $3 a head from visitors to Powell. There will also be at least a few regular members on site, myself included, with telescopes; the Andromeda Galaxy and the Double Cluster in Perseus will be high overhead, and some summer-sky objects will still be visible in the west. By 9 PM, Saturn will be well above the east-northeastern horizon.

If the weather cooperates, the Geminids will almost certainly be the best meteor shower of the year; technical details at the International Meteor Organization website indicate a ZHR (definition) of 120 meteors per hour. The Moon will be just past New; as seen from Louisburg on the 13th, it will only be 4% illuminated, a fingernail clipping of crescent, and will set at 6:41 PM CST (sunset is at 4:58 that day). Best of all, the shower radiant will be above the horizon before 7 PM, making this one meteor shower you don't have to get up in (or stay up until) the middle of the night to see.

Jay Manifold [3:45 PM]

It's the Most Wonderful Time of the Year

The time when we remember past events and speculate on future developments.

Jay Manifold [6:25 AM]