Monday27 September 20046:42pm MDT2004-09-28 UTC 0042 last
panel top next

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

Today's issue status: done


Cover: During the week of 20-26 September, the discoveries of 21 near-Earth asteroidal objects were announced. Ten of these were small asteroids, with five announced just on Friday, including 2004 SS26, which is seen at left in confirmation imagery from the day before from Robert Hutsebaut in Belgium using a Rent-A-Scope 0.25m telescope in New Mexico. This is a composite of 18 five-second exposures stacked on the object's motion of 40.57"/min. toward 149.1° when it was at its closest — about 15.8 lunar distances from Earth. For more about 2004 SS26, which was posted to the European Spaceguard Central Node Priority List today as urgent (visibility ends October 2nd), see yesterday's report

2004 ST26 gets a kick – panel 1/1 Major News for 27 Sept. 2004 previous
panel top next
2004 ST26
gets a kick

By Pasquale Tricarico

Tiny 2004 ST26 made the sixth closest known flyby of the year just before midnight UT last Tuesday, coming just inside the Earth-Moon system. And shortly after midnight it buzzed the Moon at a distance of about 29,400 km. (18,255 miles), or 7.6% of the distance between Earth and Moon. Pasquale Tricarico responded to the question, “Can you separate out how much the change in this object's orbit was due to the influence of the Moon vs. the Earth?” with the following explanation.

I compared two evolutions in ORSA, one with Earth and Moon, the other with a single EM-barycenter body. The evolution of the orbital elements of 2004 ST26 is almost the same, there is not a big difference between the two cases. Of course, there is a small extra kick from the Moon in proximity of the close approach, a small “bump,” as you can see in these graphs showing how the object's eccentricity and semimajor axis changed.

For more about 2004 ST26, see the September 24th cover image and news (with a Pasquale Tricarico animation) plus yesterday's report.

In general it is always true that, if there is some distribution of mass between two objects such as the Earth and Moon, and a third object is far enough away, all it will feel is the attraction of “something” located in the barycenter of the mass distribution. That something has a mass that is the sum of the masses. As the third object gets closer to the mass distribution, it starts feeling something different, due to the non-homogeneous distribution of mass. This is exactly what happened in this case. When 2004 ST26 was far from the Earth-Moon system, the attraction was essentially due to the Earth-Moon barycenter “body.” When it got closer, it felt separate attractions from the Moon and Earth contributions to the mass, and you see the bump, or “kick,” in the smooth curve from the Moon's influence. The smooth progression in the graphs represents the region where the Earth-Moon system can be well approximated by the barycenter, while in the kick region the system is resolved by the asteroid as separate bodies.

Terminology:  The semimajor axis (a) of a heliocentric (Sun-centered) orbit is an object's average distance from the Sun. This value is given in astronomical units (AU), where one AU is the average distance from Earth to Sun, thus the semimajor axis for Earth's orbit is a=1.0. Eccentricity (e) is a ratio measuring how non-circular an orbit is. Except for some comets, this value falls between e=0.0 (perfectly circular) and e=1.0 (not circular but parabolic).

News briefs – panel 1/1 Major News for 27 Sept. 2004 previous
panel top next
News briefs

Big flyby:  NASA's Astrobiology Magazine has an article today telling that 4179 Toutatis hasn't flown past Earth this close (four lunar distances) since the year 1353. “At three miles in diameter, this massive asteroid is the largest to pass that close in a century. Toutatis will measure about half the size of the asteroid that 65 million years ago caused the last mass extinction.”'s report today says “No space rock this big will pass so close in the next century.” And SpaceDaily has two AFP reports together today, one about Toutatis and another listing some of the larger minor object projects and missions.

Meteor news:  The Slovak Spectator has an article today that mentions a meteorite on display in cafe in the Slovakian village of Strba: “The 100-kilogram meteorite, almost half a metre in diameter, was [plowed up in a farm field] in the Westerwald region of Germany in 1930.”

Priorities:  Seven small objects with discoveries announced during 24 or 26 September, and which were mentioned in yesterday's weekly report without observing priorities available, were all posted today to the European Spaceguard Central Node Priority List. Six are level 1 Urgent: 2004 SC56 (visibility ends 16 Oct.), 2004 SR26 (5 Oct.), 2004 SS26 (2 Oct., see above), 2004 ST26 (30 Sept., see above), 2004 SU26 (7 Oct.), and 2004 SW26 (3 Oct.). And 2004 SU55 was posted as level 2 Necessary (19 Dec.).

Risk monitoring - panel 1/1 Major News for 27 Sept. 2004 previous
panel top next
Risk monitoring 27 Sept.

Only ten 2004-discovered near-Earth objects were reported in the Monday Daily Orbit Update MPEC, and none of them with impact solutions. Such is the observing slow down to be expected around the time of the full Moon.

Summary Risk Table - sources checked at 0040 UTC, 28 Sep




 2004 SW55 NEODyS 9/262026-20465-7.07-7.7301.114
JPL 9/262026-20927-6.23-6.4601.114
 2004 RQ252 NEODyS 9/252031-20552-5.63-5.6306.009
JPL 9/20R E M O V E D
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.   [ 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