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Meanwhile, on 29 January 2008, during the daytime, Asteroid 2007 TU24 passes between Earth and Sun at a distance of about 345,000 miles, and is about 300 meters across (from its brightness). It is interesting enough and large enough for an attempt to target it with radar. That will aide in computing future position and any possible Earth Impacts.

Concerning the possible Impact on Mars: 30 Jan 2008. Some thoughts.

The Latest THREAT to The Planet Mars. (besides us.) Is THAT Asteroid!

Asteroid: 2007 WD5

In the unlikely event of an impact, the time would be 2008 January 30 at 10:56 UT (2:56 a.m. PST) with an uncertainty of a few minutes. ---- NASA

By now -- everyone knows the asteroid 2007 WD5 will come "close" to Mars or maybe crash into it.

For the immediate future, I would hope more research would turn up additional images, and hope further refinement will force me to get my larger scope and ready it for an impact "event." I could only hope to see an impact flash, and I'd probably "blink" and miss it -- so it would be a good idea for whoever wants to witness an impact even with a small-to-modest telescope be able to make a "video".

The "swath" you will see below actually comes from these speckles of computed asteroid positions. Because we are mostly homebound critters we can only make observations from Earth (vicinity)and through the wiggly atmosphere. (Unless you have a Hubble.)

Wiggly positions with RMS (root mean square error analysis) values are wonderful. Unless you have exceptional clarity it is difficult to see in the sub-arc second range to get a position. Digital equipment producing digital images have an advantage of being able to make a fast record and sensitive imagers can catch almost every photon to make a digital image. Even with these methodologies the wiggly air makes them photons 'dance' through the air in position and fill nearby pixels, but good manipulation of the data can be done -- enough so to build the captured light into an image carried through time to become sensitive enough to provide a good position.

Right now the asteroid 2007 WD5 is between Earth and Mars, and below, I have posted the elements from JPL's site so you can enter these values into "planetarium type" programs if you have them, like "RedShift" or some of the more sophisticated visualization tools for showing the sky. The computation tools of, for example, "The Sky" and many other programs, are capable of very sophisticated visualizations, and if you have your own observations, they can be included to refine your orbital projections. JPL's are very good -- they should be. It is their job.

If you used a great many observations and plotted the asteroids position in the future from the various observations, you would end up with a great variety of possible future locations. That is similar to the difficulties we have in determining any impact point. We need a lot better "distance to" measurements. On the Moon, a retro-reflector, a corner cube reflector, was left -- and because we fired a laser at this cube and measured the return reflection -- we know precisely the distance to the Moon. Actually this has been an ongoing operation with a laser at McDonald Observatory near Fort Davis, Texas, since the Apollo visits to the moon.

Visit this site to roughly examine the orbit.

http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2007%20WD5;orb=1;cov=0;log=0#orb

The "Reddish Belt" of sky in the adjacent image and the area it covers against the planet is narrow compared to Mars, and contains the likely impact locations -- if there is an impact. Mars is about 4150 miles (6790km) in diameter and the width of the "belt" is about 373 +/- miles wide(600km). The asteroid is traveling about 27,900 mph (7.75 miles/sec or 12.5km/sec) That is a lot of kinetic energy, and if it is ordinary density rock, and only 50 meters in diameter, this amounts to 1.53 x 1016 Joules or 3.66 MegaTons TNT. But lets carry this a little further -- to the credible max; to a worst case. If 2007 WD5 is an iron-nickel left-over scrap of the early solar system formation days it could be as large as 750 feet in diameter, with an albedo of 5-7%, density of 8 and carry 3.73 x 1018 Joules or 890 MegaTons TNT. This size of impactor makes fairly large crater possibly over 4 miles across and 3/4 of a mile deep.

The link below provides a NASA animation of the asteroids approach to Mars.

http://www.nasa.gov/mov/206962main_Mars_Asteroid_Animation.mov

REFINEMENT From 75:1 to 25:1

As of late December 28 the probability of a Martian impact was elevated from 1-in-75 to about 1-in-25. (Almost 4%) If you were a partner of the Deer Hunter and had a revolver with one chamber loaded in a 25 chamber cylinder . . . and you spun the cylinders and it stopped, and you aimed it at the planet, or yourself . . . would you take the chance, and pull the trigger?

(Hmmm? Do we need another posting to discuss your gambling problem?)

The "refinement" is noted here in the article from NASA and I quote:

"Pre-discovery observations of asteroid 2007 WD5, taken on November 8, 2007 have allowed its orbit to be refined and the uncertainties for the late January Mars encounter have been improved. The impact probability resulting from the recent orbit refinement has increased to a surprising 3.9% (about 1 in 25 odds). The uncertainty region during the Mars encounter now extends over 400,000 km along a very narrow ellipsoid that is only 600 km wide. Since the uncertainty region intersects Mars itself, a Mars impact is still possible. However, the most likely scenario is that additional observations of the asteroid will allow the uncertainty region to shrink so that a Mars impact is ruled out. In the unlikely event of an impact, the time would be 2008 January 30 at 10:56 UT (2:56 a.m. PST) with an uncertainty of a few minutes."

Updated Uncertainty Region for 2007 WD5 at encounter with Mars, shown as white dots. The thin white line is the orbit of Mars. The blue line traces the motion of the center of the uncertainty region, which is the most likely position of the asteroid.

Image: NASA, JPL

"The "pre-discovery" observations were located by Andy Puckett, a recent Ph.D. from the University of Chicago who has since moved to the University of Alaska, Anchorage. Dr. Puckett located the observations in the archive of the Sloan Digital Sky Survey II, which contains extensive repeat coverage of 300 square degrees along the sky's celestial equator. The observations were taken using a 2.5 meter aperture telescope at the Apache Point Observatory near Cloudcroft, New Mexico. For the recent orbit refinement, these pre-discovery observations on November 8 were added to the existing observations provided by the Catalina Sky Survey and Spacewatch observatories (both near Tucson AZ) as well as New Mexico Tech's Magdalena Ridge Observatory." --NASA (quotes around "pre-discovery"--mine, Les Porter)

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In the next two weeks, more precise observations of the 2007 WD5 asteroid will be made with very large and quite a few smaller telescopes, and further refinements to the orbit will be made.
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NASA UPDATE JAN 2, 2008 And I quote:

Don Yeomans, Paul Chodas and Steve Chesley
NASA/JPL Near-Earth Object Program Office
January 2, 2008

"Additional position observations for asteroid 2007 WD5 taken on December 29 through January 2 have been used to improve the accuracy of the asteroid's orbit. As a result, the range of possible paths past Mars has narrowed by a factor of 3 and the most likely path has moved a little farther away from the planet, causing the Mars impact probability to decrease slightly to 3.6% (about one chance in 28). The new positional observations were made using the 2.4 meter telescope at New Mexico Tech's Magdalena Ridge Observatory and reported by astronomer Bill Ryan. It seems likely that as additional observations further shrink the uncertainty region of this asteroid, the region will no longer intersect Mars and the impact probability will quickly drop to zero."

Updated Uncertainty region at closest approach to Mars:

IMAGE: NASA, JPL

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Personally, and for multiple reasons, I hope we get to see an impact!!! -- and I hope it is impressive. I hope it is educational! I hope it adds funding to projects dedicated to locating all the "nearby" Earth objects with Earth-impact potential. Why "nearby?"

Far away ones, like icy comets that fall toward the Sun for tens of thousands of years would be difficult to detect until they get pretty close, say inside the orbit of Uranus -- with even an extremely large telescope, and the best and most sensitive photon capturing devices. If they have our number on them, our number is up. Won't hurt to "look" thoroughly though. It might be centuries after we solve the removal of CO2 from our air, before we could begin to push comets around and protect our world from inevitable external threats.

An impact devotee or "student" with a telescope of some size (Say 12 inches objective diameter or larger) and high power eyepieces for projection to imaging equipment should be prepared to record the possible impact, if one is announced. You won't see the asteroid, but if the impact occurs, you "might" see the flash, and your equipment might see the dust cloud raised, or its shadow or a slight color change in a tiny area on Mars.

Mars is ideally situated for observation at 10:56 UT in the Pacific Time Zone, as well as Mountain Time and even Central Time. Even Eastern Time zone is not impossibly bad either, but you look through a lot thicker "tube" of Earth's air.

Image NASA --JPL
January 8, 2008 From NASA and I quote:

NASA JPL "has updated the orbit of 2007 WD5 using new observations from the 3.5-meter telescope at the Calar Alto Observatory in Spain. This update also incorporates refinements to the Sloan precovery observations mentioned previously. While the best estimate of close approach distance remains steady at about 30,000 km, the uncertainty in position at the close approach has decreased by a factor of three. As a result, the impact probability estimate has fallen to 2.5%, or 1-in-40 odds. If the estimated miss distance remains stable in future updates, the impact probability will continue to fall as continuing observations further constrain the uncertainties. "

1:40 Well! Mars looks safe from this one!

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1:10,000

Astronomers RULE OUT Possibility of Asteroid Impact on Mars

Image of 2007 WD5 from the University of Hawaii 2.2-meter telescope on Mauna Kea, Hawaii. The circled dot is the asteroid. Other dots are artifacts from cosmic rays. The stars are trailed because the telescope is tracking the asteroid as it moves among the stars. (Credit: Tholen, Bernardi, Micheli with support from the National Science Foundation).

From NASA:

"Updated Jan 9, 2008 – As expected, scientists at JPL's Near-Earth Object Office have further refined the trajectory estimate for asteroid 2007 WD5 and ruled out any possibility of a Mars impact on Jan. 30. The latest trajectory plot of the asteroid was made possible by adding to previously obtained data some new data from a round of observations acquired by three observatories on the evenings of Jan. 5 through 8. Based on this latest analysis, the odds for the asteroid impacting Mars on Jan. 30 are 0.0 percent. The latest observations come from the German-Spanish Astronomical Center, Calar Alto, Spain; the Multi-Mirror Telescope, Mt. Hopkins, Ariz.; and the University of Hawaii telescope, Mauna Kea, Hawaii.

Drawing: NASA

Updated Uncertainty Region for 2007 WD5 at encounter with Mars, shown as white dots. The thin white line is the orbit of Mars. The blue line traces the motion of the center of the uncertainty region, which is the most likely position of the asteroid.

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I would have liked seeing one new fresh big hole -- on Mars. As long as it was ON Mars.

Astronomical Magnitudes (A quickie, this might help you understand astronomical magnitudes.)

If something is bright you really notice it, like Venus or the Moon in the sky. Way back when, before there were telescopes, people spent night times using their un-aided eye to see all the stars and knew some stars were brighter than others. People see six levels of brightness, and that was easily communicated -- although it was learned that people had different visual abilities -- and fainter objects could be seen by rare and eyesight-gifted people. The Greeks classed them into six groups of brightnesses, and the six magnitudes of visually accessible stars was born. In recent times (last century or two) people with the ability to see at the edge of the eighth magnitude were known, many of them becoming astronomers. EE Bernard was one such gifted person.

But most people could only see "six levels" of night-time star brightness, six magnitudes. The Greeks also noticed that there seemed to be a difference of about 2 times in brightness between each magnitude, so magnitude 1 was twice as bright as magnitude 2, and so on. A 4th magnitude star was twice as bright as a 5th magnitude star. So, as the positive number of the magnitude gets larger, the star is fainter.

Science minded people like measurable things (actually, things MUST be measurable to do "science" of any progressive value) so in 1856 British astronomer Norman R. Pogson formalized magnitudes noting that a first magnitude star or object was 100 times as bright as a sixth magnitude object and introduced his brightness system with the publication of a list of brightnesses of 36 asteroids on the 1st day of each month for the year 1857. He suggested formalizing the system so that 1 magnitude in difference was the 5th root of 100, or 2.512... and eventually the system was adopted internationally.

If you can see 6th magnitude stars, which is normal, how much fainter is asteroid 2007 WD5 at magnitude 22.1, than the faintest star you can see, at magnitude 6? It is a lot fainter. But here is how you can answer the question of just how much fainter.

22.1-6 = 16.1 magnitude steps, with a 2.512 change in brightness per "step". This is equivalent to (2.512)16.1 = 2,756,234 times fainter. (Technically this is 5th root of (100) =(2.511886...)16.1 = 2,754,228 time fainter.)

To see "visually" the 22.1 magnitude object would require a telescope of about 460 inches diameter. So we do not have any hope of seeing the object visually. Another way to determine what size telescope you would need to use to visually, through the eyepiece to see a 22.1 magnitude brightness is to measure accurately your dilated eye diameter and the limit of magnitude you can see flat-footed without a telescope at night. That difference will be very close to that 2.754228 million. To check it out, determine the area of your dilated eye and compare it with the light collecting area of a 460 inch mirror.(I used 7mm pupil and came up with 2,786,038 times area, as an example. However, I can see stars a tiny bit fainter than 6th magnitude, so I could use a slightly 'smaller' telescope.)

To "visually" see what the Hubble records in its Deep Image, which is about 30th magnitude -- would require a "telescope" of roughly 17,500 inches, or half again a thousand feet across -- something smooth as glass and half again as big as the Arecibo radio telescope, but in the visible spectrum, with an optical surface.

Your eye has an "exposure" time of about 1/10 of a second. Light enters your eye, stimulates rods, cones, and the information is mapped via the optic nerves to the occipital region of your brain. Since this happens about 10 times a second, the slow refresh rate allows the 24 frames or 25 frames per second of a movie to look smooth. You need to capture photons and add them up. Film works for that, but so do digital imagers.

I used to "push" Tri-X Pan film, cut sheet, or roll in the film-development-process (the chemistry) to "ISO 3600." But the ISO of your eye (and mine) is about ISO 500,000. Compare this organic camera to the widefield camera on the Hubble with an effective ISO of about 330 and you realize the eye is more sensitive than most film or digtital imagers, but it just can't hold onto the photons, or record and add them up like CCD's (charge coupled devices) do.

Human eyes are a remarkable "front-end" for interaction with the world. But it still takes a 1500-foot diameter telescope to get close to 30th magnitude objects naked eye visually.

Magnitude and Object Size

Astronomers have devised a means to compare objects that are of a variety of reflectivities, (albedos), and have computed sizes based on an object's magnitude and reflectivity.

"Absolute Magnitude" of a solar system body, like an asteroid, reflecting sunlight -- is how bright it would be if it were simultaneously 1 Astronomical Unit from the Earth and 1 AU from the Sun. The asteroid 2007 WD5 has an absolute magnitude of 24.283. Right now the asteroid of interest is 1.354 AU from the Sun and 0.416 AU from Earth. (Hey, it changes as I write.) This makes it brighter than its absolute magnitude (H) of 24.283 -- but still faint at mag 22.1, making its announced diameter dependant on its albedo (reflectivity.)

The diameter of the asteroid is not known with any certainty, but it is posted on NASA to be 50 meters (164 feet) in diameter meaning that it is made of very reflective material -- maybe like a dirty whitish snowball. That is very conservative.

http://cfa-www.harvard.edu/iau/lists/Sizes.html

For Magnitude 22.0
Albedo--------50%------ 25% --- 5%
Diameter-----75m -----110m ---240m
For Mag. 22.1 (authors interpolation)
----------------67m -------100m ---225m
---------------220ft ------- 325ft ---740ft

I think it is larger than 50 meters diameter from the above values since the smallest diameter assumed requires an albedo of 50%.

These values you can feed into your planetarium program, such as one of the RedShift programs.
Element Value, (Uncertainty (1-sigma)), Units
Eccentricity e 0.6025186863821474503311 (0.00086906)
Semi-major axis a 2.5413799581624889611930 (0.0056033) AU
Perihelion distance q 1.0101510441725090050368 (1.8609e-05) AU
Inclination i 2.3713495389216228126372 (0.0026802) deg
Longitude of the ascending node 67.53998738637327 (0.00037442) deg
Argument of Perihelion 312.6459818181322 (0.0060134) deg
Mean Anomaly M 313.3896582797448 (0.15415) deg
Time of Perihelion Passage tp 2454392.094313025830 [2007-Oct-18.59431303] (0.00011513) JED
Orbital period 1479.799335161823 days (4.894d)
Orbital period 4.05 years (0.0134yr)
Mean motion n .2432762276924745 (0.00080457) deg/d
Aphelion distance Q 4.072608872152468 (0.0089793) AU
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Do we have any way to get a "better" idea of the diameter of the asteroid via instruments?

When it gets to detecting asteroid objects with "Absolute Magnitudes" of 24 or 25 it takes a large telescope. That is, for any reasonable exposure time, a large aperture to collect enough light is required. If you have equipment with which you can actually point at and track the asteroid, (That is, you "know" the gross features of its orbit, and have programmable motion "steppers" to follow the object) you won't have much of a "streak." The size of the tracking error should help you analyze the small streaks shape. (You can get star streaks and asteroid streaks, since every photon counts.)