The Cepheids of M100 . ... Credit Copyright: NASA , HST , W. Freedman ( CIW ), R. Kennicutt ( U. Arizona ), J. Mould ( ANU ) Explanation: Can this blinking star tell us how fast the universe is expanding? ... Cepheids variable stars are therefore used as distance indicators . By noting exactly how long the blinking period is and exactly how bright the star appears to be, one can tell the distance to the star and hence the star's parent galaxy. ... NASA Official: Jay Norris. ...

... Comet Tutorial . ... On July 1, 1993 an image was taken with the Hubble Space Telescope (HST) that clearly shows at least 15 individual fragments in one image frame of the train. ... This made an accurate orbit (or orbits) difficult to determine; however, after numerous observations of the comet, astronmers determined that the comet had passed within 96,000 kilometers (60,000 miles) of the center of Jupiter or 25,000 kilometers (16,000 miles) from the cloud tops during the July 8, 1992, approach. ...

... Comet Tutorial . ... On July 1, 1993 an image was taken with the Hubble Space Telescope (HST) that clearly shows at least 15 individual fragments in one image frame of the train. ... This made an accurate orbit (or orbits) difficult to determine; however, after numerous observations of the comet, astronmers determined that the comet had passed within 96,000 kilometers (60,000 miles) of the center of Jupiter or 25,000 kilometers (16,000 miles) from the cloud tops during the July 8, 1992, approach. ...

... Meta Index / Home Page / Description / Specifying source region shapes . When radiusstyle =`contour', the task calculates the source region shape as an elliptical locus which approximates the contour of the PSF at a given flux value. ... Clearly, in order to calculate the shape of such a flux contour, it is necessary firstly to normalize the PSF to the source brightness and secondly to determine the flux level (in `brightness' units per pixel) at which to find the contour. ...

... Observing . ... Solar Observing . ... April 3 (SUN) - Solar Observing, Central Park , Manhattan . ... APRIL'S SKY . ... Lecture Series at the American Museum of Natural History The Amateur Astronomers Association is proud to present an astronomy lecture series from October through May each year for our members and the .. ... The€аAmateur Astronomers Association of New York€аwas organized in 1927 to promote the study of Astronomy, emphasizing its cultural and inspirational value. ...

Measurement of Sky Brightness at the Iranian National Observatory Davoud Afshari1 and Sadollah Nasiri1,2 1Physics Department, Zanjan University, Zanjan 45195-313, Iran; Institute for Advanced studies in Basic Science (IASBS), Zanjan 45195-1159, Iran; Measurement of light pollution 2 Introduction Among 34 candidate sites at the central part of the country, 5 sites namely Garkesh (in Kashan ), Kolahbarfi(in Kashan ), Deynava (in ... One of these is light pollution. ...

Next: ZGSC (Compressed GSC) and XSKYMAP . ... This is a preliminary report on an investigation of the quality and properties of plates digitized during creation of the Guide Star Catalog (GSC). The results will be vital for reclassifying GSC objects. ... Many objects are measured on more than one plate, and thus have multiple catalog entries. ... Among the shortcomings of the GSC are: biased magnitudes and incorrect classifications for certain objects, presence of artifact objects. ...

... The described algorithm is suitable for measurements of complex images of stars. ... a) the zero-based number of stars in the complex (multicentric) image, . b) set of preliminary coordinates - x i , y i , for all stars, index i is number of a star, . ... i - index of a star in the complex image; . ... These parameters are calculated by a nonlinear method of a least squares.The main output parameters of this algorithm are x i , y i ; where the index i is number of a star in the multicentric image. ...

... The Pleiades star cluster, also known as the Seven Sisters and Messier 45, is a conspicuous object in the night sky with a prominent place in ancient mythology . ... The stars in the Pleiades are thought to have formed together around 100 million years ago, making them 1/50th the age of our sun, and they lie some 130 parsecs (425 light years ) away. ... Data for these stars are listed in a table below. ... Yes . ... WEBDA Pleiades cluster data . ... M45: The Pleiades Star Cluster (2007 November 18) ...

Physical and dynamical parameters of particles in outbursting Comet 17 P/Holmes . ... The time depending offset between the center of brightness and center of mass of the comet nucleus has been determined on the ground of positional observations of the comet. ... The motion of these particles allowed subsequent offset between the center of brightness and center of mass of the comet nucleus to be obtained from positional observations. ... comet, dynamical model, outburst, brightness. ...

Aristarch is Copernic of Classic World. ... First Aristarch determined the fact for how many times the Sun was father then the Moon and then he compared the Sun and the Moon with the Earth. ... Only the Moon rotates around the Earth. ... Gipparch suggested that the Sun turned around the Earth steady and in circumference but the Earth is displaced according its centre. ... The orbit point in which the Sun is nearer to the Earth Gipparch called perigee and the most remote one he called apogee . ...

... It is found that the correlation coefficients between these two parameters calculated separately inside and outside the sunspot formation zone ±30 have cyclic variation and occur in anti-phase. This suggests different mechanisms of formation of the corona in the fields of small, medium, and large scales. ... The relationship between the coronal green line brightness (CGLB) and the magnetic field strength (MFS) has been investigated by constructing the corresponding synoptic maps for the 1977-2001. ...

Modeling of atmospheres of the brightest stars belonging to the Cyg OB2 association O LGA M A RY E VA , V. G . K L O C H K OVA , E.L. C H E N T S OV Special Astrophysical Observatory RAS; olga.maryeva@gmail.com We present the results of modeling of the spectrum of the brightest stars belonging to the Cyg OB2 association ­ Cyg OB2 #7 (O3If ) and Cyg OB2 #11 (O5Ifc). ... The lines in Cyg OB2 #7 spectrum are divided into three groups which can not be described with a single model. ...

... I. Mean Surface Brightnesses and Integral Color Indices for Bars Gusev A.S. ================================================================================ Abstract: UBVRIJHK surface brightnesses and color indices of bars of galaxies are determined using surface photometry data for 100 barred galaxies (table1.dat). ... J0 Mean surface J0 brightness 46 A1 --- CI- CI sign 47 -50 F1.2 magn/sq.arcsec. U-B)0 (U-B)0 color index 52 -55 F1.2 magn/sq.arcsec. ...

Authors: V.A. Marsakov , Yu.G. Shevelev , . Journal: 1988, Astron Zh. ... Absolute magnitudes, metallicities, effective temperatures, surface gravities, distances, and tangential velocities are calculated for 5498 F stars with homogeneous data on uvby photometry and proper motion, and placed within 80 pc from the Sun. Components of space velocities, eccentricities of galactic orbits, perigalactic and apogalactic distances, and maximal remotness from galactic plane are presented for 1787 stars. ...

... Star altitudes at upper culmination depends on the latitude and on the precession period phase. That altitudes can be easily calculated for any epoch. ... The adopted extinction coefficient of 0.25 mag leads to the conclusion that the catalogue data has been obtained at the middle of 2-nd century b.c. at the latitude of +31 deg. Besides it is quite impossible for the catalogue to be worked out at more northern latitudes or to the south of + 26 deg. nor later than 2-nd century b.c. ...

... Since moonshine is really reflected sunlight, the full Moon is on the average slightly brighter in mid-winter, when Earth is closest to the Sun. In addition, the distance of the full Moon also varies, due to the ellipticity ("eccentricity") of the Moon's orbit. On 22 December, 1999, the two effects combined to produce the brightest full Moon of the century. ... This year will be the first full moon to occur on the winter solstice, Dec. 22nd, commonly called the first day of winter. ...

... ARTICLE: The Adventurous Search For The Astronomical Unit . ... Kepler himself had suggested to use the rare occasions of Venus transiting (crossing) the solar disk to measure our distance to the planet. ... Due to the orbital inclination of Venus against the ecliptic of 3.5°, a Venus transit is so rare that it happens only at intervals of 121.5 years, 8 years, 105.5 years, 8 years and so on. ... Crabtree witnessing the transit of Venus 1639 . ... Transits of Venus - The Quest for the Solar Parallax...

... PUBLIC LECTURE - APRIL 12, 2016 . New Discoveries in the Outer Solar System: Ceres, Pluto and Planet X . ... Dr. Green will talk about "New Discoveries in the Outer Solar System: Ceres, Pluto, and Planet X". ... Beginning in 1992 planetary astronomers began to find Pluto like objects beyond the orbit of Neptune showing us that Pluto was a member of an entirely new family of objects we now call the Kuiper Belt. ... Amateur Astronomers Association of Princeton, Inc., ...