Hale—Bopp彗星的一次爆发观测

使用上海天台的１．５６ｍ望远镜和Ｓｅｒｉｅｓ２００ＣＣＤ照相机发现Ｈａｌｅ－Ｂｏｐｐ彗星于１９９６年４月２１日于４月２３日期间有一次爆发,４月２２彗星星等比前一天增亮了０．２等,但一天后其亮度又致恢复原来的亮度,这段时间内,彗头的半强度处的直径也相应的变化。     

1994年4月的SL9彗星观测

１９９４年４月１２日晨，我们对Ｓ９彗星进行了成功的观测．观测使用云南天文台一米望远镜和加了缩焦器的Ⅱ号ＣＣＤ系统．照相机像素为５１２×５１２，视场约７’×７’．在近两小时的不同时刻的四张照片中，观测到了彗星２１颗碎核中的主要部份及其运动．本文介绍了此次观测情况和资料处理，并给出对ＳＬ９各彗核的位置和亮度的测量结果．     

1997年3月4日海尔-波普彗星的小规模分裂

１　引言彗核分裂是彗星的最重要特征之一．至１９８２年止文献记录共观测到２２个彗核分裂,３３个次核［１］．１９８６年哈雷彗星回归时观测到彗核的分裂［２］．１９９６年紫金山天文台２００ｍｍ赤道望远镜和青岛观象台同时观测到百武彗星的分裂［３］．海尔波普彗星从１９９５年８月到１０月曾爆发５次［４］．１９９６年３月至１２月不断有喷流射出,彗核活动日趋剧烈［５］．１９９７年３月４日我们观测到彗核的小规模分裂及喷流特征,３月３日我们观测到海尔波普彗星近核照片上有喷流,这可能是３月４日彗核小块分裂的前奏．３…     

海尔—波普彗星自转周期的测定

采用小波方法对海尔波普彗星的近核ＣＣＤ图像进行处理,并进一步分析了彗核的亮度中心周围的特征结构,从而提出了一种直观而有效的方法来测定海尔波普彗星投射在观测平面上的平均自转周期,结果为２４．４１±０．９６小时     

寻找彗星的望远镜

寻找彗星的望远镜张大庆１９９６年１月３１日凌晨（日本当地时间），日本鹿儿岛县的天文爱好者百武裕司，用他的２５×１５０ＦＵＪＩＮＯＮ双筒望远镜，在天秤座发现了一颗亮度１１等星的新彗星，这就是被新闻媒介广泛报道的“百武彗星”，编号Ｃ／１９９６Ｂ２。这是百...     

海尔-波普(Hale-Bopp)彗星的观测

海尔－波普（Ｈａｌｅ－Ｂｏｐｐ）彗星的观测刘学富１９９７年春天要发生的两大重要天象：一是１９９７年３月９日在我国漠河地区可看到日全食；另一个是１９９７年春（２月中旬～４月底）可能出现亮度壮观的海尔，波普彗星，为了帮助天文爱好者朋友们开展天文观测，特编...     

我们观测了林尼尔彗星

Ｃ 1 999Ｓ4Ｌｉｎｅａｒ彗星 ,是在 1 999年 9月 2 7日被发现的 ,Ｃ 1 999 Ｓ4是它的编号 ,ＬＩＮＥＡＲ是近地小行星计划的缩写。尽管发现该彗星时它十分暗 ,但天文学家们经过计算发现该彗星将在 2 0 0 0年 7月 2 4日过近日点 ,届时的亮度可能达到 3等或 4等 ,这是一颗在北半球的夏夜可以用肉眼观测的彗星。进入今年 5月份 ,我们巡天会就开始密切关注该彗星的动态 ,不断查看ｓｋｙｐｕｋ(ｓｋｙａｎｄｔｅｌｅｓｃｏｐｅ) ,ｓｋｙｍａｐ ,ＮＡＳＡ的主页 ,下载各种有关 1 999Ｓ4的数据。我们发现ＳＫＹＭＡＰ预报的彗星的亮度与另两个网站…     

海尔-波普彗星球状喷出物的光变曲线

研究了海尔－波普彗星１９９６年９月的光变曲线,发现其在９月１０日至１１日发生了一次爆发,爆发时核Ｖ星等增亮２．１ｍ．相应地,在ＣＣＤ图像上也发现爆发时彗核抛出的２个球状凝聚物．     

彗星C/1997L1被改名为“朱-巴拉姆”彗星

彗星Ｃ１９９７Ｌ１被改名为“朱－巴拉姆”彗星据１９９８年１月２３日国际天文学联合会快讯消息,由北京天文台观测宇宙学课题组于１９９７年６月３日发现的彗星Ｃ１９９７Ｌ１被重新命名为“朱－巴拉姆”彗星。这一决定是国际天文学联合会小天体命名委员会为了确定...     

海尔-波普彗星的一个可能的巨大等离子体喷流

１９９６年９月１１日，使用上海天文台１．５６ｍ望远镜和Ｓｅｒｉｅｓ２００ＣＣＤ照相机，在Ｂ波段发现海尔波普彗星有一个巨大的喷流，初步认定为等离子喷流．     

The Destruction of Heterogeneous Cometary Grains as the Possible Cause of Variations and Outbursts of Comets' Brightness

It is examined whether the destruction of heterogeneous cometary grains can explain the variation of cometary brightness and comet outburst.Calculations were carried out for water ice grains with carbonoxideinclusions. It was shown that for realistic chosen values of parametersthe comet luminosity can increase by even a few stellar magnitudes.     

BVR broadband photometry of comets 1P/Halley and 4P/Faye

We analyzed the visible broadband photometric data of comets 1P/Halley and 4P/Faye, obtained during their perihelion passages of 1986 and 1991, respectively at the Sanglokh Observatory (Tajikistan) and the European Southern Observatory (Chile). Applying the Lomb-Scargle periodogram in the V-band magnitudes and B-V color index, we find that the most probable periodicities are 79 ± 6 and 7.36 ± 0.04 days for 1P, and 6.1 ± 0.3 days for 4P. After comparing results of color and magnitude periodograms, we argue there is a systematic difference in the number of signals identified and the level of confidence of the same periodicity in the periodograms. Our results suggest the quest for periodicities in the color of the coma of active comets should be complementary to ones in magnitudes. We have verified that the distribution of the color B-V of Faye’s coma was invariable during and after the possible occurrence of a post-perihelion outburst. We verify a symmetry in the pre- and post-perihelion H₀ photoelectric absolute magnitude of the comet Halley. The same issues were not observed in the B-V color index. We verify that the absolute magnitude H₀ of the comet Halley differs from each other when calculated from the visual or photoelectric magnitudes, due to the section of the coma used to estimate these magnitudes. We also verified that this difference in the photometric aperture can compromise comparisons of B-V color distributions between active comets.     

Polarimetric Study of Comets C/1995 O1 (Hale–Bopp) and C/2000 Wm1 (Linear)

We made polarimetric observations of comet Hale–Bopp covering awide phase angle range, from 18.8 to 47°. At certain phase angles the heliocentricdistance of the comet was less than 1 AU during its pre and post perihelion passages. Oneof the important findings, based on the data in the visual bands, is the higher polarizationwith stronger wavelength dependence compared to comet Halley, indicating the presenceof much finer grains in comet Hale–Bopp. It may also be noted that comet Hale–Bopphas shown highest degree of polarization known so far for any comet and hence fallsin the class of high polarization comets. Polarimetric observations were made of cometC/2000 WM1 (LINEAR)using narrow band (IHW) filters 4845 Å and 7000 Åand broad bands filters BVR during November 23–26, 2001 when the phase angle rangedfrom 15 to 22°. Some of the results based on these observations are presented anddiscussed.     

Brightness changes in P/Halley

Thirty photometric magnitudes, in each filter (UBV), of P/Halley (1982i) have been measured on 1986, January 12. They show short-term variability of about 0.15 magnitude. The present measurements show the active nature of the comet.     

Dust Trails of 8P/Tuttle and the Unusual Outbursts of the Ursid Shower

We calculate the position of dust trails from comet 8P/Tuttle, in an effort to explain unusual Ursid meteor shower outbursts that were seen when the comet was near aphelion. Comet 8P/Tuttle is a Halley-type comet in a 13.6-year orbit, passing just outside of Earth's orbit. We find that the meteoroids tend to be trapped in the 12:14 mean motion resonance with Jupiter, while the comet librates in a slightly shorter period orbit around the 13:15 resonance. It takes 6 centuries to decrease the perihelion of the meteoroid orbits enough to intersect Earth's orbit, during which time the meteoroids and comet separate in mean anomaly by 6 years, thus explaining the 6-year lag between the comet's return and Ursid outbursts. The resonances also prevent dispersion along the comet orbit and limit viewing to only one year in each return. We identified past dust trail encounters with dust trails from 1392 (Dec. 1945) and 1378 (Dec. 1986) and predicted another outburst on 2000 December 22 at around 7:29 and 8:35 UT, respectively, from dust trails dating to the 1405 and 1392 returns. This event was observed from California using video and photographic techniques. At the same time, five Global-MS-Net stations in Finland, Japan, and Belgium counted meteors using forward meteor scatter. The outburst peaked at 8:06±07 UT, December 22, at zenith hourly rate ∼90 per hour, and the Ursid rates were above half peak intensity during 4.2 h. We find that most Ursid orbits do scatter around the anticipated positions, confirming the link with comet 8P/Tuttle and the epoch of ejection. The 1405 and 1392 dust trails appear to have contributed similar amounts to the activity profile. Some orbits provide a hint of much older debris being present as well. This work is the strongest evidence yet for the relevance of mean motion resonances in Halley-type comet dust trail evolution.     

Photometric Study of Comet C/2014 S2 (PANSTARRS) After the Perihelion

We analyzed the BVR photometry of comet C/2014 S2 obtained between March and June 2016, in observatories installed in Europe and the United States. Using the Lomb–Scargle periodogram, we found that the most probable periodicity deduced from the V-band magnitudes is 2.70 days, suggesting that it is the period of rotation of the nucleus of this comet is \(2.70 \pm 0.07\) days or \(68 \pm 2\) h, with a peak-to-peak light curve amplitude of \(0.4 \pm 0.1\) magnitudes. We verify that the absolute magnitude \(H_0\) and the activity index n differ from each other when they are calculated from the visual or CCD magnitudes. Considering the absolute magnitude \(H_{v0}=\) 6.0, obtained from visual magnitudes, we estimate that the lower limit of nuclear radius is 1.3 km. Analyzing the variation of magnitude R with the photometric aperture, we suggest that the coma of this object was in steady-state within the time limits of our observational interval. The coma had a mean color index B–V\(=0.79\pm 0.22\), which is typical of active comets. Additionally, we have shown that the use of a variable photometric aperture, linked to geocentric distance, is probably unnecessary for the comet PANSTARRS .     

Secular brightness variations of periodic comets as a result of desintegration of their icy-dust nuclei and the solar activity

Results are presented from studies of the features of secular brightness fading for 18 short-period comets. The results by Sekanina are supplemented by new data on periodic-comet apparitions after 1964. Annual and orbital-period variations in the absolute magnitude for each comet, as well as the corresponding average values are determined. A statistically significant effect of the 90-year solar activity cycle on secular variations in the integrated magnitudes of short-period comets is found. The corresponding correlation coefficient is 0.81.     

The α-Monocerotids meteor outburst: the cross section of a comet dust trail

One minute counts obtained during the meteor outburst of α-Monocerotids on November 22, 1995, are analyzed in order to examine the possibility of filamentary structure in the stream profile. None is found. It is argued that far-comet type outbursts are due to the Earth's passage through the dust trail of a long period comet, thus offering a direct means of studying such comet dust trails. Hence, the meteor stream activity curve is the first accurate cross section of dust densities through a comet dust trail.     

Discovery Of Mg-Rich Pyroxenes In Comet C/1995 O1 (Hale-Bopp): Pristine Grains Revealed At Perihelion

The NASA Ames HIFOGS spectrometer observed comet C/1995 O1 (Hale-Bopp) at epochs including 96 Oct 7–14 UT (2.8 AU), 97 Feb 14–15 UT (1.2 AU), 97 Apr 11 UT (0.93 AU), and 97 Jun 22, 25 UT (1.7 AU). The HIFOGS 7.5–13.5 μm spectrophotometry (R = 360 - 180) of the silicate feature at 2.8 AU is identical in shape to the ISO SWS spectra of comet Hale-Bopp (Crovisier et al., 1997); the strong 11.2 μm peak in the structured silicate feature is identified as olivine. Upon close passage to the sun, the HIFOGS spectra at 1.2 AU and 0.93 AU reveals strong peaks at 9.3 μm and 10.0 μm. The post-perihelion 10 μm silicate feature at 1.7 AU is weaker but has nearly the same shape as the pre-perihelion spectra at 1.2 AU, reverting to its pre-perihelion shape: there is no change in the dust chemistry by close passage to the sun. The appearance of the strong peaks at 9.3 μm and 10.0 μm at r_h ≲ 1.7 AU is attributed to the rise in the contribution of pryoxenes (clino-pyroxene and orthopyroxene crystals) to the shape of the feature, and leads to the hypothesis that the pyroxenes are significantly cooler than the olivines. The pyroxenes are radiating on the Wien side of the blackbody at 2.8 AU and transition to the Rayleigh-Jeans tail of the blackbody upon closer approach to the Sun. Composite fits to the observed 10 μm silicate features using IDPs and laboratory minerals shows that a good empirical fit to the spectra is obtained when the pryoxenes are about 150 K cooler than the olivines. The pyroxenes, because they are cooler and contribute signficantly at perihelion, are more abundant than the olivines. The perihelion temperature of the pyroxenes implies that the pyroxenes are more Mg-rich than the other minerals including the olivines, amorphous olivines, and amorphous pyroxenes. The PUMA-1 flyby measurements of comet P/Halley also indicated an overabundance of Mg-rich pryoxenes compared to olivines. Comet Hale-Bopp's pyroxenes are similar to pyroxere IDPs from the ’Spray‘ class, known for their D-richness and their unaltered morphologies: Hale-Bopp's Mg-rich pyroxenes may be pristine relic ISM grains. This revised version was published online in July 2006 with corrections to the Cover Date.