Stellar Clusters are very useful laboratories for empirically studying stellar evolution. ... All cluster stars are at the same distance . All cluster stars have the same physical age . ... CM diagram Young Cluster In this case we see the Main Sequence fully represented. The blue dots represent massive stars with short main sequence lifetimes. ... Thus, identifying the most massive star which is still on the main sequence is an effective means of determining the age of a stellar cluster. ...

... The first time you acquire an object you must include the overhead for the guide star acquisition. ... If it is larger, then the observer can choose to maintain pointing through the gyros (drop-to-gyro) or re-acquire the guide stars (3 minute overhead per re-acquisition-note that this is not the 6-minute orbit re-acquisition) every time the telescope goes back to the target; with the first option the pointing uncertainty is about 1 milliarcsec/second due to telescope drift. ... Exposure overheads: ....

... 2013 April 8 . A Redshift Lookup Table for our Universe . ... One such table is listed above , where redshift z is listed in the first and last columns, while the corresponding universe age in billions of years is listed in the central column. ... Although stars in our galaxy are effectively at cosmological redshift zero, the most distant supernova e seen occur out past redshift one , which the above chart shows occurred when the universe was approximately half its present age. ... About APOD | ...

... Colours of stars and galaxies hold information on intrinsic and extrinsic parameters, such as stellar temperatures and galaxy populations, selective absorption and colour changes due different dust contents and inclination angles of galaxies, as well as galaxy redshifts and evolution. ... The colour magnitude diagram of 65000 galaxies to which all above-mentioned quantities and others contribute can only be explained by comparison with simulations. ... Colours are also of technical help. ...

... The first part of the Astropark that most people see represents our own Solar System. The Sun and the nine main planets are laid out here, so that you can compare their distances and sizes. ... The Sun - the closest star to Earth, represented by a giant archway at the same scale as the planets beyond. ... They move in orbits around the Sun, also marked out in the Astropark. Moons - in orbit around nearly seven of the planets, but not represented in the Astropark. ...

... Circle area is proportional to the number of tweets + retweets tweets retweets . Order accounts: by user number (effectively random) by number of tweets (includes retweets) by number of followers by number of followers that also tweeted about AAS223 by number of friends that also tweeted about AAS223 . ... The top/left position is for the user with the largest number of followers, and the bottom/right is for the smallest number of followers. by number of followers that also tweeted about AAS223 . ...

A visual impression of the data used in the study. The relevant extra-galactic maps are represented as shells of increasing distance from Earth from left to right. ... After this are six shells containing maps of the millions of distant galaxies used in the study. These maps are produced using different telescopes in different wavelengths and are color-coded to show denser clumps of galaxies as red and less dense regions as blue. There are holes in the maps due to data quality cuts. ...

Guest Editorial , July 2006 . Past ? Present ? Future . ... SETI, the quest for reasonable signals from Space, is aimed at the Past. ... From here on Earth, we can say with good reason that conducting both searches (SETI) and transmission (METI) of reasonable signals, we appear poised just halfway between the Past and the Future: namely, in the Present! ... This editorial was submitted in response to Their Past, Our Future , by SETI League executive director emeritus H. Paul Shuch. ...

... Next | Index . A window can display multiple, independently scrollable frames on a single screen, each with its own distinct URL. ... The Frame object is provided a convenience for referring to the objects that constitute frames. However, JavaScript actually represents a frame using a window object. Every Frame object is a window object, and has all the methods and properties of a window object. ... JavaScript 1.1: added blur and focus methods; added onBlur and onFocus event handlers . ...

The Mars Flag has a different design on the reverse side. obverse side of flag . ... The orbit lines on the obverse cross the Sun on the lower half of the flag and appear to go behind the Sun on the upper half of the flag. The reverse side has the orbits lines continuing around the Sun on the upper half of the flag. ... The Mars Flag reverse side is a continuation of the obverse side and not just a different design on the back and not a mirror image of the obverse. Main Flag Background Color . ...

... Formulas are very similar to equations. Consider for now only equations with one unknown variable , denoted by some letter, which can be x but can also be different. An equation is an equality between two mathematical expressions containing the unknown number (maybe in several places), as well as other numbers which are known. ... For instance--if you multiply two sides of a formula by the same number, the result is still a valid formula, even if what you multiply contains unknown numbers. ...