... The Round Earth . ... Aristarchus around 270 BC derived the Moon's distance from the duration of a lunar eclipse (Hipparchus later found an independent method). ... Let R be the radius of that circle and T the time it takes the Moon to go around once, about one month. ... Viewed from Earth, a "new Moon" (occuring between the time a thin crescent is last seen before sunrise and the time one is seen shortly after sunset) happens when the Moon in its apparent motion around the sky overtakes the Sun. ...

Replica of the flagship of Columbus, . ... When Christopher Columbus proposed to reach India by sailing west from Spain, he too knew that the Earth was round. ... The Greek philosopher Erathosthenes went one step further and actually estimated how large the Earth was. ... Erathosthenes established that the direction of the noon Sun differed from the zenith by an angle that was 1/50 of the circle, that is, 7. 2 degrees, and from that he estimated the circumference of the Earth to be 250,000 stadia. ...

... Posts tagged ?distance estimation? ... Since I began to subscribe arxiv/astro-ph abstracts, from an astrostatistical point of view, one of the most frequent topics has been photometric redshifts . ... Tags: cosmology , distance estimation , Lutz-Kelker bias , machine learning , Malmquist bias , Photometric Redshift , spectrum , survey , VO . ... Comment . ... Entries RSS . Comments RSS . ... General comments . ... vlk on [MADS] Parallel Coordinates . ... Entries (RSS) and Comments (RSS) . ...

... Stars Forming in Serpens . ... At that estimated distance, this sharp, near-infrared close-up of the active Serpens star-forming region spans about 2 arcminutes or just over half a light-year. Dark Lunar Eclipse . ... The Moon passed close to the center of Earth's shadow on August 28th. Seen best by skywatchers in western North America, and the Pacific region, the resulting total lunar eclipse was a dark one, lasting about 90 minutes. ... Could Hydrogen Peroxide Life Survive on Mars . ...

... Home Education Classes AAA Winter Astronomy Class: Measuring Distances in Space тАУ Dec 2015 тАУ Feb 2016 . ... Classes . AAA Fall Astronomy Class: Astronomy Basics тАУ October-November 2015 . AAA Winter Astronomy Class: Measuring Distances in Space тАУ Dec 2015 тАУ Feb 2016 . AAA Spring Astronomy Class: The Physics of Astronomy тАУ February - March 2016 . ... This MonthтАЩs Sky тАУ April 2016 . ... Dec. ... Observing Resources for Amateur Astronomers - Part 1: Beginning Observers . ...

... The absolute magnitude of the RCBs in the LMC and the small number of Galactic RCBs implies that they are very rare stars. Together with statistics for related stars, the total number of hydrogen-deficient stars in the Galaxy is estimated to be about 1000. Whilst the luminosity of RCBs is similar to that of other low-mass stars as they evolve rapidly from the asymptotic RED GIANT branch to become WHITE DWARFS , their frequency is much lower. ...

Apollo 12 astronaut Alan Bean holds a special environmental sample container which holds soil collected during the second moonwalk EVA. ... Central Latitude/Longitude (deg): -3.01, 23.42 . ... Instrument: Hasselblad Camera . ... Instrument Field of View (deg): 60 mm Focal Length . ... Illumination Incidence Angle (deg): N/A . ... NASA Image ID number: AS12-H-49-7278 . ... Code 633, NASA Goddard Space Flight Center . Greenbelt, MD 20771, USA . ... Code 630, NASA Goddard Space Flight Center . ...

... 2013 February 10 . Asteroids in the Distance . ... Explanation: Rocks from space hit Earth every day. ... Many kilograms of space dust pitter to Earth daily. ... Further, just last year the 50-meter wide asteroid 2012 DA14 was discovered that will pass inside the orbit of Earth's geosynchronous satellites this coming Friday. A collision with a large asteroid would not affect Earth's orbit so much as raise dust that would affect Earth's climate . ... About APOD | ...

Russian SHAREABLE DATA CENTER Institute of Solar-Terrestial Physics SB RAS . ... The algorithm and appropriate program for decametric radiosignal propagation conditions prediction for paths from 500 to 9000 km have been developed at ISTP SB on the basis of normal wave method (AltyntsevaB.I,Iliyin N.V., Kurkin V.I. and others //Decameters channel simulation on the base of normal wave method . ... Solar activity indices are chosen automatically from the prediction date from the database . ...

. Mars is "behind" the sun from the earth's point of view and is therefore not visible in the nighttime sky (i.e. its up in the daytime). Venus it at greatest elongation and appears in the western sky as a bright object for 2-3 hours after sunset .

Pulkovo NEO Page . Central Astronomical Observatory at Pulkovo . ... Control of Observations . ... NEA Accuracy Estimation . ACCURACY OF THE WORLD NEA OBSERVATIONS . Pulkovo method of accuracy estimation was applied to NEA observations. ... 2005 . 2006 . ...

Estimates for the Set-theoretic Distance between Orbits of Celestial Bodies . ... It is reasonable to use preliminary simple criteria for the proximity to intersection based on estimates of set-theoretic distance ( , 0 ) between orbits , 0 of celestial bodies , 0 . ... We describe here two simple criteria and one more complicated one. ... The third one requires calculation of the distance itself and it amounts to solving a trigonometric equation of the 8-th degree. ...

... In this paper we present the results of detailed B, V, R, I, and H study of the isolated nearby blue compact dwarf (BCD) galaxy NGC6789. Judging from the literature the observed galaxy has not been resolved into stars up to now. ... The distance of the galaxy, estimated from the tip of the red giant branch (TRGB) is 2.1 Mpc which places NGC6789 close to the Local Group. ... Key words: nearby galaxies: dwarf galaxies (NGC 6789): distance moduli: star content . ... Distance. ...

DETERMINATION OF THE HUBBLE CONSTANT FROM THE GRAVITATIONAL STABILITY CRITERION OF THE GASEOUS DISKS, by A.V.Zasov, D.V.Bizyaev. ... Following proposition has been put forward: a total surface density of gas at radius $R_H$, where the mean densities of atomic ($\sigma_{HI}$) and molecular ($\sigma_{H_2}$) hydrogen are equal, corresponds (or proportional to) the critical gas density $\sigma_c$ for gravitational stability of gaseous disk. ...

... Ciel Espace, le magazine qui vous guide toujours plus loin . ... des actualitГїs . ... des interviews, des portraits . les plus belles images de l'Univers dГїcryptГїes pour vous . ... des pages consacrГїes Г la publication de vos photos Mais c'est aussi une vraie communautГї avec laquelle partager votre passion et nourrir votre curiositГї. Accueil Г? la une A quelle distance sont les Гїtoiles ? ... A quelle distance sont les Гїtoiles ? ... 23/05/2014 - Les cratГЕres de Mars sont-ils Г vendre ? ...

... George Benedict, University of Texas at Austin . ... Abstract . ... Quasars at Redshift z=6 and Early Star Formation History . ... The cosmic distance scale and dark energy are two key issues in modern astrophysics, and HST has played a vital role in probing both. On the one hand, HST has been involved in cosmic distance measurements since its inception, largely through the H 0 Key Project, which used WFPC2 to identify and photometer Cepheids in 31 spiral galaxies at distances from 60 to 400 Mpc. ...

... In 1930, Trumpler noticed that linear diameters (LD) of open clusters increase with distance (D) from the Sun. ... Since that time, the interstellar absorption has become one of the best studied factor in astrophysics, and we may hope that current OCL distance scales are free from this LD-D correlation. To verify if this is the case we have chosen several modern OCL distance scales and test them with the same clusters and the same angular diameters that Trumpler had used back in 1930. ...

... We can help students grasp the significance of Hubble's extremely keen eye, and learn a bit about angles and math in the process, with the following in-class activity. ... Looking through binoculars or telescopes allows us to magnify a small section of the sky. To measure sizes or distances in that small section, astronomers divide a degree into 60 smaller pieces called arcminutes, and further subdivide minutes into 60 smaller sections called arcseconds. ... 30 feet = . ... 36 seconds . ...

The redshift distance modulus modz , in mag, is derived from the Virgo infall vvir , it can be used to determine the absolute magnitude knowing the apparent one. It is defined as modz = 5 log(D L ) + 25 where D L is the luminosity-distance in Mpc, defined by the law of dimming of the observed flux: F L / D L 2 . ... D L is derived from the cosmological redshift, assuming the following values for the Hubble constant and other cosmological parameters: H 0 = 70 km/s/Mpc . ...