用心看星，感受“鹿林彗星”——记星云天文社观星活动

2008年2月28日,昆明三中、昆明滇池中学星云天文社的40来名天文爱好者,坐车前往东川红土地,观察鹿林彗星。     

彗星与小行星

19P/Borrelly彗星2月2日过近日点19P/Porrelly(博雷利)彗星是一颗常规的周期彗星,远日点5.83AU,在木星轨道外侧一点,周期6.84年。1904年12月28日,法国天文学家博雷利(Alphonse Borrelly)在马赛发现了它,至今已经回归过16次,上-次回归是在2015年。博雷利彗星将于今年再次回归,并于2月2日抵达近曰点,同时亮度也达到极值。     

彗星情报站

发现的新彗星 2004年2月发现的正式编号的彗星有C／2004C1(Larsen)、C／2004 D1(NEAT)。 2004年2月12日,美国月球和行星实验室的J.A.Larsen报告在Spacewatch拍摄的资料上发现了一颗18.5等的彗星,编号为C／2004 C1(Larsen)。最初粗略的轨道显示它的近日距为4.3个天文单位,将于2005年     

点慧台

最新发现： 2008年11月里没有新发现的彗星,这种情况近年来非常罕见。 近期关注： C/2007 N3（Lulin）是以我国台湾鹿林天文台的名字命名的第一颗彗星,发现者是广东年轻的天文爱好者叶泉志和我国台湾著名的业余天文爱好者林启生,最早发现于2007年7月11日,发现时的亮度为18．9等。     

太阳风的发现之路

人类对太阳风最早的实验观测来自于对彗星彗尾的观测。在1943年,霍夫迈斯特(Hoffmeister)发现离子彗尾的方向与彗核和太阳连线方向(径向)有一个系统的且通常小于5度的偏离,起初天文学家们试图用太阳光的光压来解释这一偏离,但光压太弱,不足以造成这么大的偏差。另一个早期使人们费解的现象是在一些彗星中观测到的所谓“断尾事件”,即在彗星的彗尾中有时会观测到彗尾有很明显的不连续性(见图1)。为了解释霍夫迈斯特的发现,德国天体物理学家比尔曼(Biermann)于1951年提出了     

彗星情报站

2005年11月里共发现并命名了4颗新彗星。 11月4日夏威夷大学的D.Tholen报告Fabrizio Bernardi用夏威夷大学小行星巡天项目(UHAS)的3.6米加拿大-法国-夏威夷望远镜发现一颗新20等的彗星,编号为P/2005V1(Bernardi)。 11月20日E.J.Christensen报告了他在执行Catalina巡天项目任务时发现的一颗彗星,彗星的亮度17等,编号为C/2005 W2(Christensen),这个目标得到了其他一些观测者的证实。最初粗略的轨道为2005年6月1日过近日点,近日距3.2天文单位。随后发现LINEAR在11月3日已经拍摄到它,     

彗星情报站

2006年2月里共发现并命名了3颗彗星。其中P/2005SB216(LONEOS)最早发现于去年9月30日,当作小行星编号为2005 SB216,从12月开始陆续有观测者发现它具有彗星特性,最后于2006年2月7日确定为彗星,亮度19等。另外,本月有两颗周期彗星得到永久的编号174P/Echeclus和175P/Hergenrother。重新发现的周期彗星是41P/Tuttle-Giacobini-Kre-     

彗星情报站

新发现的彗星 以下是2004年3月发现的正式编号的彗星: P/2004 DO29(Spacewatch-LINEAR),P/2004 F1(NEAT),P/2004 CB(LINEAR),C/2004 F2(LINEAR),P/2004 F3(NEAT),C/2004 F4(Bradfield)。 2004年3月共发现了6颗彗星。 2004年2月17日Spacewatch和LINEAR发现了     

彗星情报站

最新发现2007年4月发现并命名了4颗彗星。2007年4月10日 LINEAR 发现一颗小行星状天体,随后确认为新彗星,编号为 C/2007 G1(LINEAR),亮度17.5等。最初给出的轨道显示彗星于2009年3月8日过近日点,近日距2.5天文单位。最后从更多的观测数据得出精确的轨道,过近日点的时间提前到2008年11月17曰,近日距增加到2.65天文单位。这是     

紫金山彗星(1977q)的轨道

1977年11月3日紫金山天文台发现一颗新彗星,定名为紫金山彗星(1977q)。本文收集了国内外共42次观测资料,精确计算了这颗彗星的轨道,轨道为近于抛物线的双曲线,逆向运行。1977年7月24日过近日点。文中给出了近年观测历表。最后,考虑全部大行星的准确摄动,计算研究了当此彗星处于日心距约为60天文单位时原始的和将来的轨道。     

A Disconnection Event of Comet Lulin†

The cometary disconnection event (DE) is the separation of the entire cometary tail or a part of it from the cometary head. It is one of the most spectacular phenomena of comets. The driving mechanism remains unclear, and at present there are many competitive theories to explain the onset of DE. However, the variable solar wind is suspected to play a major role. Comet Lulin exhibited a DE on 4th Feb. 2009. The data around this date are analyzed, and it is found that the comet Lulin had already endured a DE on 3rd Feb. 2009. By comparing the morphologies of the plasma tails in these two DEs, it is concluded that the DE which occurred on 3rd Feb. 2009 is another DE, which is distinct from that of 4th Feb. 2009. In this paper, we describe the results of analysis on the DE dated 3rd Feb. 2009. The measured velocity of disconnection motion is about 68 km/s, and the calculated onset time of this DE is 3.635 ± 0.215 Feb. 2009 in UT decimal date. Combining the orbital characteristics of Comet Lulin before and after the DE occurrence and the solar-wind data measured by the STEREO-A spacecraft, it is concluded that the DE which occurred on 3rd Feb. 2009 was probably caused by the magnetic reconnection due to the interaction between the comet and a coronal mass ejection (CME).     

Characteristics and Performance of the CCD Photometric System at Lulin Observatory

The Lulin One-meter Telescope at Lulin Observatory in Taiwan started open-use observations in January 2003. In order to evaluate the performance of the CCD photometric system, the characteristics and quality of the site, we obtained data of photometric standards as well as calibration data from February to November 2004. We report here the results of our analysis including the gain, readout noise, dark current and linearity of the CCD camera, and transformation coefficients, total throughputs, night sky brightnesses and limiting magnitudes for UBVRI bands.     

Imaging polarimetry of Comet 9P/Tempel before and after the Deep Impact

The NASA's Deep Impact mission was the first impact experiment to a cometary nucleus. The target of the mission was Comet 9P/Tempel, one of the Jupiter family comets. The impact was performed on July 4th, 2005. Imaging polarimetric observations were carried out by Polarimetric Imager for COmets (PICO) mounted on the Lulin One-meter Telescope (LOT) at Lulin Observatory, Taiwan. Intensity and linear polarization degree maps were obtained on July 3-5, 2005. Impact ejecta plume was clearly recognized in the enhanced intensity map. Furthermore, arc-shaped region of high polarization was recognized in the polarization map. Dust grains in this region had larger expansion velocity than the grains which provided the brightest area in the intensity map. comparing our results with the MIR spectroscopy obtained by Subaru Telescope we conclude that very small carbonaceous grains might be responsible for the region of high polarization.     

Observations of OH maser lines at an 18-cm wavelength in 9P/Temper1 and Lulin C/2007 N3 comets with RT-22 at the Crimean Astrophysical Observatory

Investigations on OH maser lines in comets have been performed with the RT-22 at CrAO. The results of observations of 9P/Temper1 and Lulin C/2007 N3 comets in the OH molecule line at a wavelength of 18 cm are presented. An original technique for observation data analysis has been developed. The gas production rate of OH molecules in these comets is estimated.     

Parabolic orbit determination. Comparison of the Olbers method and algebraic equations

In this paper, the Olbers method for the preliminary parabolic orbit determination (in the Lagrange–Subbotin modification) and the method based on systems of algebraic equations for two or three variables proposed by the author are compared. The maximum number of possible solutions is estimated. The problem of selection of the true solution from the set of solutions obtained both using additional equations and by the problem reduction to finding the objective function minimum is considered. The results of orbit determination of the comets 153P/Ikeya-Zhang and 2007 N3 Lulin are cited as examples.     

Determination of the parabolic orbit for a body moving in the plane of the ecliptic,by the Laplace method

A modification of the Laplace method for the determination of a preliminary orbit of a body moving in the plane of the ecliptic is presented. It is shown that on the basis of three close positions on the celestial sphere, the parabolic orbit can be determined in cases, when the classical Laplace method is not suitable. The numerical estimation of the number of possible solutions is carried out, and their spatial distribution depending on initial conditions is shown. An example of the determination of an orbit for the comet C/2007 N3 (Lulin) is given.     

Impact trajectories of the asteroid Apophis in the 21st century

The asteroid Apophis is one of the most hazardous near-Earth asteroids. As a result of the scattering of Apophis?? potential trajectories after its close approach in 2029, and its possible approach in 2036, there are many dangerous trajectories including impact trajectories after 2036. The purpose of this study is to identify and investigate these trajectories. We use the Everhart integrator; the DE405, DE423, and EPM2008 ephemerides; and two sets of initial data for Apophis (those collected by NASA in 2006 and by the IAA in 2010). More than 50 possible encounters in this century are presented, including 13 encounters between 2036 and 2050. The minimum geocentric distances obtained using a different ephemeris and initial conditions differ little between themselves. Analogous results in (Yeomans et al., 2009) are consistent with our results.     

SphinX: The Solar Photometer in X-Rays

Solar Photometer in X-rays (SphinX) was a spectrophotometer developed to observe the Sun in soft X-rays. The instrument observed in the energy range ≈?1?–?15 keV with resolution ≈?0.4 keV. SphinX was flown on the Russian CORONAS–PHOTON satellite placed inside the TESIS EUV and X telescope assembly. The spacecraft launch took place on 30 January 2009 at 13:30 UT at the Plesetsk Cosmodrome in Russia. The SphinX experiment mission began a couple of weeks later on 20 February 2009 when the first telemetry dumps were received. The mission ended nine months later on 29 November 2009 when data transmission was terminated. SphinX provided an excellent set of observations during very low solar activity. This was indeed the period in which solar activity dropped to the lowest level observed in X-rays ever. The SphinX instrument design, construction, and operation principle are described. Information on SphinX data repositories, dissemination methods, format, and calibration is given together with general recommendations for data users. Scientific research areas in which SphinX data find application are reviewed.     

Comparisons and Evaluations of JPL Ephemerides

In the light of the wide applications of a series of ephemerides developed by the Jet Propulsion Laboratory (JPL) of the National Aeronautics and Space Administration (NASA) of the USA to many aspects like the deep-space navigation and interplanetary exploration, it is necessary to make comparisons of their contents, applicable ranges, realizations and maintenances. In view of the fact that the explorations of the Venus and Mars are expected to carry out in China, their dynamical models and the adopted observational data are analysis by taking the DE405, DE421 and DE423 to be the examples. From the evaluations of the accuracies and performances of the above-mentioned ephemerides of different editions, their effects on the probes orbiting around the Venus or Mars are emphatically discussed, and a suggestion is given for their use that as far as the Venus missions are concerned, the use of the DE423 is recommend, and that the use of the DE421 or DE423 is recommended for the Mars Missions.     

Soft X-ray variability over the present minimum of solar activity as observed by SphinX

Solar Photometer in X-rays (SphinX) is an instrument designed to observe the Sun in X-rays in the energy range 0.85–15.00 keV. SphinX is incorporated within the Russian TESIS X and EUV telescope complex aboard the CORONAS-Photon satellite which was launched on January 30, 2009 at 13:30 UT from the Plesetsk Cosmodrome, northern Russia. Since February, 2009 SphinX has been measuring solar X-ray radiation nearly continuously. The principle of SphinX operation and the content of the instrument data archives is studied. Issues related to dissemination of SphinX calibration, data, repository mirrors locations, types of data and metadata are discussed. Variability of soft X-ray solar flux is studied using data collected by SphinX over entire mission duration.