Sunday22 August 20049:09pm MDT2004-08-23 UTC 0309 last
panel top next

The Asteroid/Comet Connection's
daily news journal about
asteroids, comets, and meteors

Today's issue status: done

The weekly small objects report appears on Tuesday.

Cover: It has been the tradition every Sunday since we started running “cover” images in January to have the Sunday cover always relate to small near-Earth asteroids. Today we make a big exception and run a big asteroid, Main Belter 3184 Raab, to send big wishes to Herb Raab for successful surgery this coming week and a speedy recovery. This image shows his asteroid moving to the upper left of galaxy NGC 3628, caught at Great Shefford Observatory (larger image and details) last January 18th by Peter Birtwhistle, who notes that Herb Raab “has helped so many people over the years with such great impact.”

Closest by far – panel 1/2 Major News for 22 August 2004 previous
panel top next
Closest by far

The Minor Planet Center (MPC) took the highly unusual step overnight of issuing a circular (MPEC 2004-Q22) announcing the discovery of a tiny asteroid, 2004 FU162, observed for less than an hour last March. But what an arc that was, coming to almost one Earth radius from Earth's surface, which is by far the closest ever observed astrometrically (see “Closest observed flyby”).

The circular states that “This object passed some 0.000086 AU (=13000 km) from the center of the earth on 2004 Mar. 31.65.” And the MPC Closest Approaches page, which had to add another decimal point to list this asteroid's distance, footnotes the distance as 12,900 km. = 8000 miles. Earth's mean radius is about 6,371 km. = 3,956 miles.

Only four observations are reported, all from the U.S. Air Force/MIT LINEAR program early on March 31st. But this was enough for Steve Chesley at the NASA/JPL NEO Program Office to now calculate the object's orbit before and after being perturbed by the close passage.

Gareth Williams explains in the circular that, “Although the observed arc is only 44 minutes, the orbit is quite determinate and, given the exceptional nature of this close approach, the object is now receiving a designation.”

From the estimated brightness of 2004 FU162, a standard formula can be used to roughly derive its diameter as six meters/yards. At that size, if it had entered Earth's atmosphere, it would have destructed harmlessly, although spectacularly, before reaching the ground.

next-day 2004 FU162 news  ]

Sleuthing in your own archive:  Also stated in today's MPEC is that “A search by the discoverers for prediscovery images was unsuccessful,” but checking with other 1m-class observing activities or asking amateurs to check their images isn't mentioned. Peter Birtwhistle said to the Minor Planet Mailing List (MPML) today:

[2004 FU162] looks like it was AN09456 [see update], added to the NEOCP on March 31.76UT. By the time it was added it was already 2.6 hours past close approach and unobservable at ~20deg elong and mag 23. Anyone (in Australia/NZ?) get any interesting ‘satellite’ trails around 31.65UT? You definitely need a topocentric ephemeris for this one!

He tells A/CC that “My rule of thumb is that closest approach being at 31.65 UT would have been 234° of longitude after Greenwich midnight = central Australia. It dipped south of the equator, but how far depends on where you were, as parallax was huge! U.S. sites were not nearly so well placed, but at 15th mag and moving fast enough to notice.

continued >>

Closest by far – panel 2/2 Major News for 22 August 2004 previous
panel top next

<< Sleuthing in your own archive, continued

“The MPC Ephemeris Service has the object at mag 13 rising to 11 for an ephemeris generated for Siding Spring that day. This is the sort of mag at which I'm sure lots of astrometrists are picking up satellites that are moving at speeds comparable to 2004 FU162 in its run up to closest approach. It's only in the last half hour around closest approach that it was going fast enough to traverse my entire CCD field of view in a minute (and so there would be no means of determining where it was at any particular instant, since you can't see either the start or end of the trail).”

Update:  About the NEOCP temporary designation, Steve Chesley later told the MPML that 2004 FU162 “was AN09463, which was posted to the NEOCP about the same time as AN09456, but removed almost immediately.”

Closest observed flyby:  At the beginning of this report above, it is stated that the 2004 FU162 passage, at some 8,000 miles above Earth's surface, “is by far the closest ever observed astrometrically.” The distinction is important, because the title of “closest ever observed” probably belongs to the well documented Great Daylight Fireball of 1972. On August 10th many witnesses, including a meteor expert, saw and photographed an object of about 2004 FU162's size

fly through Earth's atmosphere, traveling from south to north along the Rocky Mountains of the U.S. From military satellite data it was later determined that the object passed 58 miles (93 km.) above a point in Montana during its journey. Gary Kronk's account of this event and subsequent investigations is great reading. See also these full-text references:

Ceplecha, Zdenek. March 1994. Earth-grazing daylight fireball of August 10, 1972. Astron. Astroph. 283(1):287-288. ADS 1994A&A...283..287C.

—. 1979. Earth-grazing fireballs. Astr. Insts. of Czech. Bulletin 30(6):349-356. ADS 1979BAICz..30..349C.

Hills, Jack G. & M. Patrick Goda. May 1997. Meteoroids captured into Earth orbit by grazing atmospheric encounters. P&SS 45:595-602. ADS 1997P&SS...45..595H.

A/CC's first news at 0505 UTC (1:05 EDT): MPEC 2004-Q22 issued with a Sunday 0319 UT time stamp takes the highly unusual step of announcing the discovery of an asteroid, 2004 FU162, with only a 44-minute observing arc, but what an arc — “some 0.000086 AU (=13000 km) from the center of the earth on 2004 Mar. 31.65” (1535 UTC, 10:35am EST). That's 8,073 miles, 0.033 lunar distances, or 2.04 Earth radii (i.e., it came to twice as far from the center of the Earth as you are). This was caught by the USAF/MIT LINEAR program with telescopes in New Mexico operated from Massachuestts, and the orbits were calculated by Steve Chesley at the NASA/JPL NEO Program Office for both before and after being perturbed by the passage, which is by far the closest ever observed. By standard formula using its brightness, this object is roughly estimated at six meters/yards wide, so it would have destructed harmlessly, although spectacularly, if it had entered Earth's atmosphere.

News briefs – panel 1/1 Major News for 22 August 2004 previous
panel top next
News briefs

Big NEO:  MPEC 2004-Q27 today announces 2004 QY2 as discovered Friday by the Siding Spring Survey (SSS) and confirmed yesterday by Reedy Creek Observatory, both in Australia, and also confirmed by Wykrota Observatory in Brazil yesterday and this morning by SSS. The first preliminary calculation has it crossing the orbit of Venus and coming only slightly further away from the Sun than Earth's distance. JPL was showing that 2004 QY2 has a minimum orbit intersection distance (MOID) with Earth of 0.051150 AU, which is just beyond the definition of “potentially hazardous.” Early on a Sunday evening in Pasadena (Monday UTC), however, JPL has now posted a set of very preliminary impact solutions (see details and links below).

JPL and the MPC put 2004 QY2's absolute magnitude (brightness) at H=14.4, which converts by standard formula to very roughly 5.5 km. (3.4 miles) wide, and makes it the 31st largest known near-Earth asteroid. It also appears to be the largest discovered in more than three years (since 2001 L07, H=14.29), and one of five asteroids with H<16.0 discovered so far this year. Because this object lives almost entirely inside Earth's orbit, it is rarely in view for ground-based optical telescopes.

Unusual object:  MPEC 2004-Q30 today reports that Reiner Stoss has found 2004 PY42 in the archive of NEAT's Mt. Palomar imagery from seven days between 12 June and 29 August 2002 for a total of 13 positions. The discovery of this oddball object was announced August 12th (see news) with the comment that, at that point, it had an “essentially indeterminate,” possibly even parabolic, orbit solution. Today it is determined to have a somewhat eccentric (e=0.2705) and inclined (i=19.1°) path between the orbits of Saturn and Neptune, crossing the path of Uranus. From its brightness, and using both asteroid and distant object albedo ranges, this object is estimated by standard formula to be on the order of 40-50 km. (25-30 miles) in diameter, and up to 90 km. (55 miles) using comet nucleus albedo.

Update:  Reiner Stoss notes that 2004 PY42 has an orbital shape shape and size similar to Centaur 1994 TA:

1994 TA11.71021.7950.30116.752
2004 PY4211.78320.5210.27116.152

Bits & pieces:  Peter Birtwhistle at Great Shefford Observatory has posted an entertaining page about his latest Main Belt asteroid discoveries.

Risk monitoring - panel 1/1 Major News for 22 August 2004 previous
panel top next
Risk monitoring 22 August

JPL early today posted 2004 QA2 with three very low-rated impact solutions. This object, estimated by JPL at 142 meters/yards wide, was announced yesterday in MPEC 2004-Q21 as discovered Friday by the Siding Spring Survey (SSS), which followed it for nearly five hours, and confirmed yesterday by Reedy Creek Observatory, also in Australia. 2004 QA2 isn't reported in the Sunday Daily Orbit Update MPEC.

Update:  JPL has posted 2004 QZ2, which was announced today in MPEC 2004-Q25 as discovered by the Catalina Sky Survey (CSS) in Arizona Friday morning and confirmed yesterday morning by Grasslands Observatory in Arizona and this morning by Sandlot Observatory in Kansas and Table Mountain Observatory in southern California. JPL puts this object's diameter at 480 meters/yards, and has the first highly preliminary impact solution in less than seven years.

Update #2:  JPL has posted 2004 QY2 with some very preliminary impact solutions for 11-13 July of many years to come, starting three years from now. These initial ratings come from formulas that take into account as one factor the sheer size of this object, which was announced today, Sunday — see “Big NEO” above.

Summary Risk Table - sources checked at 0234 UTC, 23 Aug




 2004 QZ2JPL 8/222011-210163-3.83-4.6502.061
 2004 QY2JPL 8/232007-209981-1.77-2.2202.042
 2004 QA2JPL 8/222037-20633-7.35-7.6800.924
 2004 PU42JPL 8/172071-210318-5.23-5.8503.772
 NEODyS 8/152071-20776-6.23-6.5203.772
 2004 PP97 NEODyS 8/172029-20757-4.04-4.5500.987
JPL 8/172023-210335-3.51-4.1100.987
VI = count of "virtual impactors" (impact solutions)
See A/CC's Consolidated Risk Tables for more and maybe
  newer details, and check the monitors' links for latest info.
Note that only objects recently in view are shown here.

Note: Impact solutions are not predictions but rather possibilities that haven't yet been eliminated, and most early solutions are removed quickly with further observation. When solutions have been posted, a night-and-day cycle of observation and analysis begins that eventually leads to removing all impact risks for most objects, usually within weeks if not days. For more about this, see "Understanding Risk Pages" by Jon Giorgini of JPL.   [ top ]
Publisher information, privacy statement, and disclaimer
The contents and presentation of this page are © Copyright 2004 Columbine, Inc. - All Rights Reserved
Please report broken links or other problems with this page to <>.
Any mentioned trademarks are the property of their respective owners.
Do NOT copy or mirror this page, but you are welcome to link to it. All information here is subject to change.
Individuals may make "snapshot" copies for their own private non-commercial use.
Linking: A/CC's Major News via frame or redirection, via partial mirror frame or redirection, or via news feed or XML/RSS
Bookmarks: A/CC's Major News via frame or redirection –&– via alternate partial mirror site frame or redirection