1,753 research outputs found
Minor Planet 2008 ED69 and the Kappa Cygnid Meteor Shower
Until recently, the kappa Cygnids (IAU#12) were considered an old shower, because the meteors were significantly dispersed in node, radiant, and speed, despite being 28-38° inclined. In 1993, an outburst of kappa Cygnids was observed, which implied that this meteoroid stream was relatively young, instead. At least some dust was still concentrated in dust trailets. Until now, no active comet parent body was known, however, and the wide 22° dispersion of nodes was difficult to explain. This work reports that a minor planet has been discovered that has the right orbital dynamics to account for the kappa Cygnids. Minor planet 2008 ED69 is intrinsically bright, with H = 16.7 ± 0.3, and moves in a highly inclined orbit (i = 36.3°). With one node near Jupiter's orbit, the perihelion distance, longitude of perihelion, and node quickly change over time, but in a manner that keeps dust concentrated for a long period of time. The stream is more massive than the remaining body, and a form of fragmentation is implicated. A break-up, leaving a stream of meteoroids and at least the one remaining fragment 2008 ED69, can account for the observed dispersion of the kappa Cygnids in Earth's orbit, if the formation epoch is about 2-3 nutation cycles ago, dating to around 4000-1600 BC. Most of that debris now passes close to the orbit of Venus, making the kappa Cygnids a significant shower on Venus
New meteor showers identified in the CAMS and SonotaCo meteoroid orbit surveys
A cluster analysis was applied to the combined meteoroid orbit database
derived from low-light level video observations by the SonotaCo consortium in
Japan (64,650 meteors observed between 2007 and 2009) and by the Cameras for
All-sky Meteor Surveillance (CAMS) project in California, during its first year
of operation (40,744 meteors from Oct. 21, 2010 to Dec. 31, 2011). The
objective was to identify known and potentially new meteoroid streams and
identify their parent bodies. The database was examined by a single-linking
algorithm using the Southworth and Hawkins D-criterion to identify similar
orbits, with a low criterion threshold of D < 0.05. A minimum member threshold
of 6 produced a total of 88 meteoroid streams. 43 are established streams and
45 are newly identified streams. The newly identified streams were included as
numbers 448-502 in the IAU Meteor Shower Working List. Potential parent bodies
are proposed.Comment: Accepted in Proceedings of the Meteoroids 2013 Conference Aug. 26-30,
2013, A.M. University, Poznan, Polan
3D/Biela and the Andromedids: Fragmenting versus Sublimating Comets
Comet 3D/Biela broke up in 1842/1843 and continued to disintegrate in the returns of 1846 and 1852. When meteor storms were observed in November of 1872 and 1885, it was surmised that those showers were the debris from that breakup. This could have come from one of two sources: (1) the initial separation of fragments near aphelion or (2) the continued disintegration of the fragments afterward. Alternatively, the meteoroids could simply have come from water vapor drag when the fragments approached perihelion (option 3). We investigated the source of the Andromedid storms by calculating the dynamical evolution of dust ejected in a normal manner by water vapor drag in the returns from 1703 to 1866, assuming that the comet would have remained similarly active over each return. In addition, we simulated the isotropic ejection of dust during the initial fragmentation event at aphelion in December of 1842. We conclude that option 2 is the most likely source of meteoroids encountered during the 1872 and 1885 storms, but this accounts for only a relatively small amount of mass lost in a typical comet breakup
Updated analysis of the dynamical relation between asteroid 2003 EH1 and comets C/1490 Y1 and C/1385 U1
The asteroid 2003 EH1, proposed as the parent body of the Quadrantid meteor
shower, is thought to be the remnant of a past cometary object, tentatively
identified with the historical comets C/1490 Y1 and C/1385 U1. In the present
work we use recovery astrometry to extend the observed arc of 2003 EH1 from 10
months to about 5 years, enough to exclude the proposed direct relationship of
the asteroid with both of the comets.Comment: Submitted to Monthly Notices of the RAS Letters Updated with a new
table and other minor change
Thermal Desorption of Water-Ice in the Interstellar Medium
Water (H2O) ice is an important solid constituent of many astrophysical
environments. To comprehend the role of such ices in the chemistry and
evolution of dense molecular clouds and comets, it is necessary to understand
the freeze-out, potential surface reactivity, and desorption mechanisms of such
molecular systems. Consequently, there is a real need from within the
astronomical modelling community for accurate empirical molecular data
pertaining to these processes. Here we give the first results of a laboratory
programme to provide such data. Measurements of the thermal desorption of H2O
ice, under interstellar conditions, are presented. For ice deposited under
conditions that realistically mimic those in a dense molecular cloud, the
thermal desorption of thin films (~50 molecular layers) is found to occur with
zero order kinetics characterised by a surface binding energy, E_{des}, of 5773
+/- 60 K, and a pre-exponential factor, A, of 10^(30 +/- 2) molecules cm^-2
s^-1. These results imply that, in the dense interstellar medium, thermal
desorption of H2O ice will occur at significantly higher temperatures than has
previously been assumed.Comment: 9 pages, 4 figures, accepted for publication in MNRA
Fundamental data on the desorption of pure interstellar ices
The desorption of molecular ices from grain surfaces is important in a number of astrophysical environments including dense molecular clouds, cometary nuclei and the surfaces and atmospheres of some planets. With this in mind, we have performed a detailed investigation of the desorption of pure water, pure methanol and pure ammonia ices from a model dust-grain surface. We have used these results to determine the desorption energy, order of desorption and the pre-exponential factor for the desorption of these molecular ices from our model surface. We find good agreement between our desorption energies and those determined previously; however, our values for the desorption orders, and hence also the pre-exponential factors, are different to those reported previously. The kinetic parameters derived from our data have been used to model desorption on time-scales relevant to astrophysical processes and to calculate molecular residence times, given in terms of population half-life as a function of temperature. These results show the importance of laboratory data for the understanding of astronomical situations whereby icy mantles are warmed by nearby stars and by other dynamical events
On the Correlation Between CO Absorption and Far-Ultraviolet Non-Linear Extinction Toward Galactic OB Stars
A sample of 59 sight lines to reddened Galactic OB stars was examined for
correlations of the strength of the CO Fourth Positive (A - X) absorption band
system with the ultraviolet interstellar extinction curve parameters. We used
archival high-dispersion NEWSIPS IUE spectra to measure the CO absorption for
comparison to parametric fits of the extinction curves from the literature. A
strong correlation with the non-linear far-UV curvature term was found with
greater absorption, normalized to E(B-V), being associated with more curvature.
A weaker trend with the linear extinction term was also found. Mechanisms for
enhancing CO in dust environments exhibiting high non-linear curvature are
discussed.Comment: 10 pages, including 6 figures. LaTeX2e (emulateapj5.sty). To appear
in ApJ, Sep 20, 200
Permanence and ambiguity in Milan:an ambiguous and composite building for Piazza Sant'Ambrogio
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