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

Today's issue status: done

• Small objects – report for 26 Jan. to 1 Feb.
• News briefs
  – Spitzer results, Rosetta & impact theory
• Risk monitoring – NEODyS has posted 2004 BB103 & JPL has removed 2003 YG118

Today's cover is an Astrometrica screen shot from Robert Hutsebaut's participation yesterday in confirming LINEAR discovery, 2004 BB103, a kilometer-plus object with impact solutions. He was working from Belgium using a Rent-a-scope telescope at New Mexico Skies Observatory, and succeeded despite the bright Moon, "thanks to [Astrometrica author] Herbert Raab's work." The faint object is marked by orange bars, while green circles show the stars used by the software to determine the astrometric position. This stack is made from 12 20-second exposures.

Discoveries & follow-up 26 Jan. – 1 Feb.

Among the smallest asteroids that come near enough to be noticed and watched, three were discovered and 13 more were tracked last week. This report summarizes that observing activity with objects listed in size order, smallest first. The data is as of Sunday, with H (absolute magnitude) and Earth MOID (minimum orbital intersection) from the JPL NEO Orbital Elements page and other planetary MOIDs from Lowell Observatory. Earth MOIDs that would be considered hazardous if for larger objects are flagged in yellow. Current Minor Planet Center H is also given, along with the original H from an object's discovery MPEC. Diameters are best estimates from a standard but very inexact H-to-size formula. Priorities, visibilities, and campaigns are from European Spaceguard Central Node (SCN).

A/CC has been developing a special focus on the smallest near-Earth asteroids since last September, and has run weekly summaries since December. The last two were for through January 18th and January 25th.

Spitzer results:  A "preliminary analysis" of data from January 21st was posted yesterday as a 19Kb PDF "to help observers planning GO-1 observations of asteroids, or observations in the ecliptic plane between -5° to +5° ecliptic latitude." It is a technical document with the title, "The Spitzer Space Telescope First Look Survey — Ecliptic Plane Component Thermal Observations and Preliminary Number Counts."

The First Look Survey (FLS) Ecliptic Component page says:

Our main goal is to characterize the population of moving objects, at 8 and 24 microns, and to explore smaller members of the asteroid population (< 1 km diameter). This survey has been designed to target asteroids in the main belt region between 2 and 4 AU, to determine number counts and ecliptic plane scale heights. With supporting ground-based observations at visible wavelengths we will also provide asteroid sizes and orbits to enable followup observations.

Rosetta:  The European Space Agency (ESA) posted another Rosetta comet mission preview today ahead of the February 26th launch.

“ [Even] Ariane 5, the most powerful launcher on the market today, lacks the power to hurl the probe on a direct route to the comet. To get the required momentum, it will rely on swing-by manoeuvres, using the gravitation pull of Mars (in 2007) and the Earth (three times, in 2005, 2007 and 2008). ”

During the ten years en route, there will be instrument tests, course corrections, and at least one asteroid encounter, but mostly just long silences.

Impact theory:  An Astronomy & Geophysics article and Cardiff University news release at EurekAlert today [see also] revisit the idea that "very cold summers around 536-540 AD" resulted from a comet impact:

The work was carried out by two Cardiff undergraduate students . . . under the supervision of Dr Derek Ward-Thompson [who said it] "shows that even a comet of only half a kilometre in size could have global consequences. Previously nothing less than a kilometre across was counted as a global threat."

UPI has a report today at the Washington Times as "Scientists: Comet caused Dark Age frosts."

Risk monitoring 3 Feb.

The Tuesday Daily Orbit Update MPEC (DOU) carries observations from LINEAR early yesterday in New Mexico of 2004 BB103, which was posted by NEODyS today and by JPL yesterday. The new data extends the short viewing arc by about 12 minutes, and today JPL very slightly lowered its risk ratings for this kilometer-plus object.

2004 BE68 has observations reported from early Saturday from Tenagra II Observatory in Arizona. This didn't add to the observing arc, but today JPL slightly, and NEODyS very slightly, lowered risk assessments for this object, while the NEODyS impact solution count rose from 44 to 55.

A single position is reported in the DOU from Saturday morning from Linz Observatory in Austria for 2004 BZ74. This didn't extend the viewing arc, but today both risk monitors cut their impact solution counts from 27 to 22 and very slightly raised their risk assessments for this object.

more Risk monitoring >>

Today's "Risk monitoring" report narrates routine activity in the night-and-day cycle of observation and analysis that identifies and usually soon removes risk possibilities. There is nothing unusual or alarming here. An "impact solution" (aka "virtual impactor" or "VI") is not a prediction but rather a possibility that hasn't been eliminated yet. To learn more, see "Understanding Risk Pages" by Jon Giorgini of JPL, and other links related to this subject.

<< continued from part 1

The DOU has a set of LINEAR observations of 2003 YG118 from early yesterday, and today JPL, for the third time since January 2nd, has removed a last single YG118 impact solution.

The European Spaceguard Central Node (SCN) Priority List today removed 2004 BN41 (more info above). Yesterday it had been noted at level 2 Necessary and in view for most observers until February 9th. An SCN observing campaign remains in effect.