2005年流星雨前瞻

过去的2004年,流星们并没有带给我们太大的惊喜。英仙座流星雨的第一峰值如约而至,但凑巧全国大部分地区天气都不好,因此可以说只见云不见雨。而2005年,可以说是名副其实的中国流星年。全年中所有适合观测的大中流星雨的峰值时间对中国     

观测角

12月 1 4日双子座流星雨极盛双子座流星雨极盛出现于 1 2月 1 4日 ,极盛期持续近两天 ,据 2 0 0 0年天文普及年历预告 ,极盛时为 1 4日1时 ,双子座流星雨辐射点的赤道坐标为 :赤经 7ｈ2 8ｍ,赤纬为 33°。在理想条件下 (即晴夜天空无月光干扰 ,可看到 6 5等的暗星 ,辐射点在天顶 ) ,每小时可看到的流星数为 1 1 0。如果一位观测者的实际可见星等为ｍ ,辐射点天顶距为ｚ,则实际可观测到的每小时流星数为 1 1 0× ( 2 .6) ｍ - 6.5× (ｃｏｓｚ) 1.4 7。1 2月 30日金星傍月1 2月 ,在日没后金星出现于西部天空 ,地平高度很大 ,观测条件良好 ,…     

2010年11月重要天象预告

十一月夜空的主角,将是几个颇具看点的流星雨,南、北金牛以及狮子座流星雨的极大非常值得期待。当然,这段时间观测条件最好的行星还是木星,而到了月底,水星和金星的观测条件也将逐渐转好。其中水星是昏星,日落后在西方的低空中隐约可见,而金星作为晨星将在日出前出现在东方天空中,亮度可达-4．6等。     

观看狮子座流星雨——从入门到精通

一、同场竞技 随着近几年的狮子座流星雨的爆发,加上各种媒体的争相报道和炒作,对观看流星发生兴趣的人越来越多。在许多人看来,如果能有幸看到夜空中星雨飘落,并且在流星出现的瞬间许下一个心愿,该是人生中多么美好的记忆啊。 流星天文学作为天文学的一个分支,许多理论和方法都有待于依靠进一步的观测来不断地完善,而流星的观测,不仅仅是专业天文工作者的事情,实际上,     

流星观测(一)

记得F4有一首歌叫“流星雨”,歌词很煽情:“温柔的天空,应该让你感动,我在你身后,为你布置一片天空……陪你去看流星雨落在这地球上,让你的泪落在我肩膀……”如果在一个晴朗的夜晚,约上两三好友,或聚屋顶,或聚球场,更为潇洒一点,或去郊外空旷的草地、山顶,在这首缠绵悱恻的“流星雨”的浅吟低唱中,各自凝视一方的天空,守侯一闪即逝的流星的出现,岂不是一件很惬意的事民间一直有这样一个说法,如果你在流星还没有消失之前许下一个心愿,这个心愿就一定能够实现。当然,这只是一种美好的愿望,但作为一种生活的点缀,也可以为守望星空的我们增添几分浪漫的情趣。流星是飘浮在宇宙空间的尘粒,受到地球引力的影响,飞向地球,与地球大气摩擦燃烧的现象。流星的高度通常以     

五天四夜追狮王——99狮子座流星雨观测札记

1999年的狮子座流星雨已经过去了,每小时5000颗壮观的流星雨暴发在欧洲地中海的上空,相信那里的星友们一定饱了眼福,真让人羡慕啊。位于太平洋西岸的中国大陆,处于此次狮子座流星雨活动极大的前期,有可能看到流星数量增长的过程,因此也吸引了全国各地大量的爱好者和群众观...     

与狮子座流星雨的再次亲密接触

一年一度的天空盛宴——狮子座流星雨如期到来了。尽管这次流星雨无论从最佳观测地点还是流星极大值上来看都不能和2001年相比。但是由于近期我实验中心刚刚从美国引进一台性能优良的Meade天文望远镜,而且实验中心的领导也很支持天文科普工作,再加上有成功观测2001年狮子座流星雨的经验,所以今年我们决定再次和它亲密接触。11月17     

中国古代流星记录的亮度归算

在中国古籍中关于流星“大如X”的纪录,是古人对星像视面大小的估测,此视面是人裸眼观星时由于光线的衍射、漫射以及视觉中的光渗作用造成的一种特殊感知现象．视面“大如X”的实质是亮度的记录．这些记录可以按古人目视观测天象的天球模型进行视大小(角直径)的量化,进而可以用一些已知亮度的流星记录为“标准点”,将其归算为亮度．并将古籍中流星“大如X”的4420次纪录的131种比体均作了亮度的归算．     

“雨”夜听流星(上)

近年的狮子座流星雨,特别是2001年的狮了座流星雨,给我国的很多观天者留下了深刻的印象。人们终于看到了罕见的天外来客所形成的闪着亮光的雨。也终于开始对天外之雨与我们地球大气之雨有什么共性与差异有了感性的知识。我们大气中的雨,主要的成分是水,但也给我们带来了其它地区或者大气中的附加     

上海天文台佘山工作站夜天亮度的变化

使用1994—2007年在1．56m反射望远镜CCD照相机拍摄的资料，测定了上海天文台余山工作站夜天亮度的变化。由于上海城市的发展，佘山工作站的夜天亮度在V波段从每平方角秒约19mag变到15．8mag，也就是说，夜天亮度自1994年以来变亮了约20倍。国际上优良台站的夜天亮度在V波段等于或暗于21．5mag。上述夜天亮度是优良台站的200多倍。现在在佘山工作站使用1．56m反射望远镜对暗于V=14mag的星做精确测光已经很困难了。     

Investigation of Weakly Magnetic CP Stars. I

The magnetic fields of a sample of chemically peculiar stars, in which they had not been detected earlier, are reinvestigated on the basis of our own measurements and literature data. Despite the considerably higher measurement accuracy, again no magnetic fields were detected in any of them. An upper limit on the field of HD 10221 of 40 G was obtained. Despite the weakness of the fields, the parameters characterizing an anomaly in chemical composition correspond to those for strong fields. The same parameters in stars with strong fields generally correspond in value, although they are lower than expected in the case of HD 47152.     

Velocity Distribution of Stars in the Pup-CMa Association

The distribution of proper motions of stars in the Pup-CMa association is presented. The stars' velocities are approximately parallel to each other, which indicates that the stars are close together in space. The mutual distribution of stars and molecular clouds in the association is interpreted as proof that the stars emerged from a single gigantic primordial molecular cloud (or several large clouds), destroyed by radiation and/or stellar wind coming from those stars. It is assumed that part of that cloud is being dissipated, while part is being broken into several small clouds, which we are observing at present.     

Neutron Stars With a Quark Core

Models of neutron stars with a quark core are calculated on the basis of an extensive set of equations of state for superdense matter. The possible existence of a new branch of stable layered neutron stars is revealed for some realistic equations of state of neutron matter.     

Three New Variable Stars

Three new variable stars have been discovered in the region of Cepheus. Their equatorial coordinates, photographic magnitudes, and amplitudes of variability are given.     

The Demarcation Point from E-AGB Stars to TP-AGB Stars in HR Diagram for Medium-mass Stars

Via a study of the evolutionary tracks of 3∼10 M stars on the Hertzsprung-Russell diagram, the variations of the energy, density, temperature at the peak of helium-shell burning, ratio of surface luminosity of helium shell to stellar surface luminosity as well as the stellar radius are analyzed. Then the demarcation point of medium-mass stars in the evolution from early AGB stars to thermally pulsing AGB stars on the HR diagram is determined, and for 119 carbon stars our analysis agrees rather well with observation. At the same time the following is suggested. After arriving at this demarcation point in stellar evolution, in the formula of the loss of stellar wind material it is probably needed to introduce a quantity which is not concerned with the surface luminosity, but it dominates the formation of super stellar wind. On this basis and via the analysis of the structure and evolution of 5 M stars as well as the rate of mass loss of stellar wind, it is found that the effect of turbulent pressure on the mass loss of stellar wind in the stage of thermally pulsing AGB stars is rather great, hence the turbulent pressure of thermally pulsing AGB stars cannot be overlooked. Furthermore, the physical factors which possibly affect the matter loss of the stellar winds of thermally pulsing AGB stars are suggested.     

Some Comments on the Magnetic Braking of CP Stars

The low rotation velocities of magnetic CP stars are discussed. Arguments against the involvement of the magnetic field in the loss of angular momentum are given: (1) the fields are not strong enough in young stars in the stage of evolution prior to the main sequence; (2) there is no significant statistical correlation between the magnetic field strength and the rotation period of CP stars; (3) stars with short periods have the highest fields; (4) a substantial number of stars with very low magnetic fields (B _e < 500 G) have rotation speeds that are typical of other CP stars; (5) simulations of the magnetic fields by Leroy and the author show that the orientation of dipoles inside rotating stars, both slow and fast, is consistent with an arbitrary orientation of the dipoles; and, (6) slow rotators with P>25 days, which form 12% of the total, probably lie at the edge of the velocity distribution for low mass stars. All of these properties conflict with the hypothesis of magnetic braking of CP stars.     

Young Close-By Neutron Stars: The Gould Belt Vs. The Galactic Disc

We present new population synthesis calculations of close young neutron stars. In comparison with our previous investigation we use a different neutron star mass spectrum and different initial spatial and velocity distributions. The results confirm that most of ROSAT dim radioquiet isolated neutron stars had their origin in the Gould Belt. We predict that about several tens of young neutron stars can be identified in ROSAT All Sky Survey data at low galactic latitudes. Some of these sources also can have counterparts among EGRET unidentified sources.     

Neutron Stars in the Subsonic Propeller Stage

In the evolutionary tracks of magnetized compact stars the subsonic propeller state is intermediate between the supersonic propeller and accretor states. The rotation rate of a star in this stage decreases because of the interaction of its magnetosphere with the surrounding hot quasistatic shell. The radius of the magnetosphere is less than the corotation radius, and the boundary of the magnetosphere is stable with respect to inter-change instabilities. The mass flow rate from the inner radius of the shell to the surface of the compact object is limited by the rate at which plasma diffuses into the magnetic field of the star. Because of this, a subsonic propeller will show up as a low (or moderate) luminosity accretion pulsar with a soft x-ray spectrum.__________Translated from Astrofizika, Vol. 48, No. 3, pp. 477–490 (August 2005).     

Search for HH Objects and Emission Stars in Star Formation Regions. III. PMS Stars in NGC 7129

Slitless spectroscopy is used to discover 22 emission stars in the central and northwest regions of the cluster located in the NGC 7129 nebula. 16 of them are found for the first time. This sample is essentially complete up to V 20.0. The emission stars are distributed nonuniformly over the field of the cluster and are concentrated toward its center. Photometry in the V, R, and I bands is conducted on more than a hundred stars in the cluster. This yields an average absorption coefficient A _V=1.7±0.27 for this region. Based on their positions in color diagrams for the optical and near IR ranges, most of the emission stars can be regarded as T Tau objects.