IRAS LRS Spectra of Comets Tempel 1 and Tempel 2 (original) (raw)
Icarus, 1989
The properties of the outer layers of comets considered for the future Comet Rendezvous and Asteroid Flyby and Comet Nucleus Sample Return missions are studied, by following numerically the thermal evolution of spherically symmetric models of the nucleus, in the orbit of Comet P/Tempel-1. The evolution starts from isothermal (10°K) and homogeneous nuclei, composed of amorphous ice and dust. The crystallization of amorphons ice at 137°K is taken into account. As the ice sublimates, a permanent dust mantle is allowed to accumulate, at a rate which is proportional to the sublimation rate. Evolutionary sequences are computed for different values of the density, the dust/ice mass ratio, and the (constant) fraction of the dust which is not carried away with the sublimating ice. The main conclusions are (a) the temperatures at the outer and inner surfaces of the dust mantle are not very sensitive to changes in the parameters; (b) although the dust is assumed permeable to water vapor, the rate of erosion of the nucleus slows down as the dust mantle grows and its insulating effect increases; (c) the temperature at a depth of 10 m is-160°K for all models considered and hence, the ice at this depth is crystalline; (d) the total thickness of the crystalline ice layer, between the dust mantle and the amorphous ice core, varies from 40 to 240 m, depending on the parameters assumed. Consequently, it should be difficult for the probes of the two comet missions to sample pristine amorphous ice, unless they are aimed at the bottom of an active crater. ~ 1989 Academic Press. IIR'.
Icarus, 2013
The Deep Impact spacecraft flew by Comet 103P/Hartley 2 on November 4th, 2010 (EPOXI mission) and Comet 9P/Tempel 1 on July 4th, 2005 (Deep Impact mission). During the two flybys, spatially resolved infrared (1.05-4.8 lm) spectra of the surface of the nucleus were acquired by the HRI-IR instrument. The analysis of these two data sets, obtained by the same instrument, offers a unique opportunity to understand, compare and contrast the surface thermal properties of these two comets. For this paper, we use spectral cubes with a spatial resolution of 30 m/pixel to 40 m/pixel for Hartley 2 and 160 m/pixel for Tempel 1. We focus our analysis on the color, temperature, thermal inertia and roughness of the nucleus. The two comets have the same color, moderately red, with an average slope of 3.0 ± 0.9% per kÅ to 3.5 ± 1.1% per kÅ. There are very small variations of the color across the surface, except for regions with water ice that are neutral to blue, and two dark spots with redder (4.5 ± 1.4% per kÅ) materials on Hartley 2. The nucleus thermal emission at all resolved spatial scales differs from that of a gray body with an infrared emissivity of 0.9-1.0, the discrepancy being more important for larger incidence angles. Moreover, the color temperature of Comets Hartley 2 and Tempel 1 is relatively homogeneous across the surface and does not vary strongly with incidence angle. These two effects mainly result from surface roughness and associated projected shadows. From the temperature rise on the morning terminator, we derive a thermal inertia lower than 250 W/K/m 2 /s 1/2 for Hartley 2 and lower than 45 W/K/m 2 /s 1/2 for Tempel 1 (3r upper limits). For Hartley 2 and Tempel 1, the temperature of the regions with exposed water ice is more than 100 K above the sublimation temperature of water ice ($200 K). This observation indicates that the thermal emission is dominated by dust, and that water ice is not intimately mixed with dust at the scale of observation, with water ice patches at the meter or sub-meter scale.
The infrared spectrum of comet C/1995 O1 (Hale-Bopp) at 4.6 AU from the Sun
Astronomy and Astrophysics, 1996
Comet C/1995 O1 (Hale-Bopp) was observed on 27 April 1996 with the ISOPHOT instrument of ISO when it was at 4.6 AU from the Sun. The 2.5-12μm spectrum was recorded at low resolution. We present here the preliminary results of this observation. The 2.5-5μm spectrum shows emission in the CO_2_ ν_3_ band. The CO_2_ production rate is about 1.3x10^28^ s^-1^. The 6-12μm spectrum shows thermal emission at a colour temperature of 162K (6-8μm range) and a strong silicate band around 10μm, with a narrow feature at 11.2μm indicative of crystalline silicates.
Spectra of comet C/2002 T7 (LINEAR)
Advances in astronomy and space physics, 2020
We present the results of spectral observations of comet C/2002 T7 (LINEAR) carried out at the 1-m Zeiss-1000 telescope of the Special Astrophysical Observatory (Russia). The spectra were obtained within the 3500-7500 Å wavelength range on November 13, 14, and 21, 2003, before the perihelion passage, when heliocentric and geocentric distances of the comet were about 2.7 AU and 1.8 AU, respectively. Spectra do not show any emission features from the strongest cometary emissions of the CN, C2, and C3 molecules. The normalised spectral gradient of reflectivity is 2.8% per 1000 Å and 5.4% per 1000 Å for November 14 and 21, respectively. The Afρ parameter, which characterises the dust production rate in the comet, is on average about 800 cm. Comet C/2002 T7 (LINEAR) can be classified as belonging to the group of dusty comets
Temperature of Comet IRAS-Araki-Alcock (1983d)
Icarus, 1985
Infrared (1.5-20 p.m) observations of the nuclear condensation of Comet IRAS-Araki-Alcock (1983d) during the interval 5-8 May 1983 (UT) show that the distribution of 3.5-to 20-/~m radiation was blackbody in character with no evidence of 10-/zm emission from silicate grains in the coma of the comet. The observed color temperature of the nuclear condensation of the comet was 319 -+ 5°K on 7 May and 307 -+ 5°K on 8 May. Low-resolution spectrophotometry on 5 May in the 1.5-to 2.6-p.m region shows no obvious emission or absorption features, but thermal radiation of approximately the same color temperature as the 3.5-to 20-p.m radiation was present along with reflected sunlight. Scans of the nuclear region of the comet indicate that most of the thermal radiation observed at 11.6 and 20.0/~m came from an -< 120-kin-diameter, unresolved area centered on the nuclear region. Absolute flux measurements suggest that projected areas (unit emissivity) of 70 and 40 km 2 were responsible for the thermal radiation from the nuclear condensation on 7 and 8 May, respectively. This large change in total surface area suggests that the amount of dust in the nuclear region of Comet 1983d was highly variable and is consistent with the observation by M. A. Feierberg, F. C. Witteborn, J. R. Johnson, and H. Campins (1984, Icarus 60, 449-454) of an outburst on 11 May 1983.
Space Science Reviews, 2005
As comet 9P/Tempel 1 approaches the Sun in 2004-2005, a temporary atmosphere, or "coma," will form, composed of molecules and dust expelled from the nucleus as its component icy volatiles sublimate. Driven mainly by water ice sublimation at surface temperatures T > 200 K, this coma is a gravitationally unbound atmosphere in free adiabatic expansion. Near the nucleus (≤10 2 km), it is in collisional equilibrium, at larger distances (≥10 4 km) it is in free molecular flow. Ultimately the coma components are swept into the comet's plasma and dust tails or simply dissipate into interplanetary space. Clues to the nature of the cometary nucleus are contained in the chemistry and physics of the coma, as well as with its variability with time, orbital position, and heliocentric distance. The DI instrument payload includes CCD cameras with broadband filters covering the optical spectrum, allowing for sensitive measurement of dust in the comet's coma, and a number of narrowband filters for studying the spatial distribution of several gas species. DI also carries the first near-infrared spectrometer to a comet flyby since the VEGA mission to Halley in 1986. This spectrograph will allow detection of gas emission lines from the coma in unprecedented detail. Here we discuss the current state of understanding of the 9P/Tempel 1 coma, our expectations for the measurements DI will obtain, and the predicted hazards that the coma presents for the spacecraft.
ISOCAM Imaging of Comets 103P/Hartley 2 and 2P/Encke
Icarus, 2001
We present the results of ISOCAM observations performed on Comets 2P/Encke and 103P/Hartley 2, on 31 October 1997 and 1 January 1998, respectively. Images were obtained in the broadband filters LW3 (centered at 15.00 µm) and LW10 (centered at 11.50 µm). Tail models have been applied to the images to analyze the evolution of the dust coma environment and to derive infor-1 Based on observation with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherland, and the United Kingdom) with the participation of ISAS and NASA. mation about the velocity of the grains. The image of 2P/Encke presents a sunward spike interpreted as a Neck-Line. Thanks to the model, the time evolution of the comet dust environment during 3 months preceding the observation has been reconstructed. 2P/Encke presents a strong maximum in the dust velocity, a broad maximum of the dust mass loss rate, and a dip of the size distribution power index around perihelion. Model results indicate that the largest grains in the tail can reach sizes from centimeters to decimeters. This has important implications for the source of the Taurid meteoroids. For Comet 103P/Hartley 2 the numerical model suggests an anisotropic dust ejection with a tail composed of grains smaller than those in 2P/Encke. Both dust ejection velocity and dust mass loss rate reach a maximum about 2 weeks before perihelion. The power law best fitting the time-averaged size distribution of both comets has an index of about −3.2, indicating that the released dust is strongly dominated in mass by the largest ejected grains.
3- to 14-μm Spectroscopy of Comet C/1999 T1 (McNaught–Hartley)
Icarus, 2002
using the broadband array spectrograph system on the IRTF. The spectrum showed a silicate emission feature extending about 20% above the continuum. Two emission features at 10.3 and 11.2 µm appeared above the silicate band, the latter seemingly indicative of crystalline olivine. The 10.3-µm feature is only a 1-2 sigma detection but if real could indicate the presence of hydrated silicates. The color temperature at 8-13 µm was 260 ± 10 K, approximately 6% above the blackbody radiative equilibrium temperature of 235 K. The magnitude at [N] was 3.13 ± 0.02. On the second night, the comet had brightened slightly ([N] = 2.98 ± 0.02) and the two prominent emission features were absent, although the silicate emission feature maintained its trapezoidal shape with shoulders at 9.5 and 11.2 µm.
Submitted, 2011-02-28; Accepted, 2011-05-03 Physical Properties of Main-Belt Comet 176P/LINEAR 1
2016
We present a physical characterization of comet 176P/LINEAR, the third member of the new class of main-belt comets, which exhibit cometary activity but are dynamically indistinguishable from main-belt asteroids, to be discovered. Observations show the object exhibiting a fan-shaped tail for at least one month in late 2005, but then becoming inactive in early 2006. During this active period, we measure broadband colors of B − V = 0.63 ± 0.02, V − R = 0.35 ± 0.02, and R − I = 0.31 ± 0.04. Using data from when the object was observed to be inactive, we derive best-fit IAU phase function parameters of H = 15.10 ± 0.05 mag and G = 0.15 ± 0.10, and best-fit linear phase function parameters of m(1, 1, 0) = 15.35 ± 0.05 mag and β = 0.038 ± 0.005 mag deg−1. From this baseline phase function, we find that 176P exhibits a mean photometric excess of ∼30 % during its active period, implying an approximate total coma dust mass of Md ∼ (7.2 ± 3.6) × 104 kg. From inactive data obtained in early 200...