... The Seasons . ... Section #1 Stargazers and Skywatchers described the observed motion of the Sun across the sky, in different seasons of the year. ... If the Earth's axis were perpendicular to the ecliptic, as in the drawings here, the Sun's position in the sky would be halfway between the celestial poles, and its daily path, seen from any point on Earth, would stay exactly the same, day after day. Each point on Earth would be carried around the axis AB once a day. ... The Sun and Seasons . ...

... Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. 2011 July 14 . Neptune: Once Around . Credit: NASA , ESA , Hubble Heritage Team ( STScI / AURA ) . Explanation: Neptune rotates once on its axis in about 16 hours. ... Because Neptune's axis of rotation is tilted to its orbital plane by 29 degrees, compared to Earth's 23.5 degrees, Neptune experiences seasons analogous to Earth's . ...

... Bad Astronomy . Misconceptions . ... Bad Astronomy : The Moon only shows one face to us because it is not rotating. Better astronomy : The Moon only shows one face because it is rotating, once every time it revolves around the Earth. ... Place the Moon model on the table about 30 centimeters (one foot) away with the X facing the Earth model. ... You'll see that to keep the X facing the Earth model, you have to rotate the Moon model as it goes around the Earth model . ... 2008 Phil Plait. ...

Different types of satellite orbits have different uses: while the synchronous orbit is best for communication satellites, Lagrangian point orbits help monitor the solar wind before it reaches Earth. A low altitude polar orbit is widely used for monitoring the Earth because each day, as the Earth rotates below it, the entire surface is covered. ... A different choice was made for MAGSAT, orbited 1979-80 to survey the Earth's own magnetic field near its surface. ...

... In FOS polarimetry mode the incoming beam was split into orthogonal polarization components by a Wollaston prism behind the entrance aperture. ... As with non-polarimetric observations, no concurrent WAVECAL exposure was routinely taken with polarimetry data, so the limiting accuracies of the default pipeline polarimetry wavelength calibration are the same as for the non-polarimetry case described earlier ( See "Wavelength Calibration" on page 32-49. ...

... There are two kinds of people: Those who enjoy the ebb and flow of the seasons, the dapples of autumnal color, the hoary headed frosts of winter, the flowers anew of spring, the live murmur of a summer's day. ... Geometry of the Seasons . ... In the Northern Hemisphere, the coldest temperatures generally occur in January and February, and the hottest in July and August. ... During winter in the Northern Hemisphere, it's summer in the Southern Hemisphere, and vice-versa (see figure 1 ). ...

... More on 51 Peg: . The discovery of a Jupiter--mass planet in orbit around the solar--type star 51Peg has been reported by Michel Mayor and Didier Queloz (Geneva Observatory) on October 6th at the 9th Cambridge workshop on "cool stars, stellar systems, and the sun" held at Florence (Italy). ... Recall that the measurements of radial velocity only yield v sin i which in turn gives us M sin i. For most values of i, sin i will be greater than 0.5 and this gives a mass estimate of 0.5 Jupiter masses. ...

Next: The Scenario Machine: Operational Up: Evolution of Magnetic Rotators Previous: Ejector-propeller hysteresis . ... The length of this segment is determined by the eccentricity. ... In this case no hysteresis occurs and transitions E -- P and the reverse take place in symmetrical points of the orbit. ... Here EP means a mixed state of the rotator at which it is in the ejector state during one part of the orbit, and in the propeller state during the rest of the orbital cycle. ...

It was hypothesized that the size of the cal deflection might depend on the rotation angle of the alfa receiver ( 2004 Dec20 Holistic estimates of Alfa cal values.. ... The data acquisition consisted of moving from rotation angle -90 to +90 in 100 seconds, then +90 back to -90. ... Fig 1: The fractional change in cal versus rotation angle is plotted. ... The cal deflection is not a function of rotation angle down to .3% of the cal value. processing: x101/050601/rot_cal.pro home_~phil ...

... Moon Phase below . ... ARTICLE: Why the moon always shows us the same face . ... Before you continue reading, you should know that this was not always the case, i.e. the Moon once was rotating with respect to the Earth, so that on every night a terrestrial observer (if there was one, because this was long, long before mankind appeared on our planet, and even before any major animals had appeared) saw another face of the Moon. ... Figure 1 (not to scale) shows how we can imagine the system Earth-Moon...

... Armagh Observatory, College Hill, Armagh BT61 9DG, +44 (0)28 3752 2928 . Asteroid 2010 SO16 and the Earth follow similar orbits around . the Sun. ... out a horseshoe shape in space, taking 175 years to go from . ... Asteroid 2010 SO16 takes 175 years to make the trip from one end of the horseshoe to the other. ... Currently, three other horseshoe companions of the Earth are known to exist but, unlike 2010 SO16, these linger for a few thousand years at most before moving on to different orbits. ...

... Hale-Bopp in Stereo . ... Earth, Clouds, Sky, Comet . ... Does a comet's dust tail always orbit behind it? ... Which is closer: the comet or the galaxy? ... Presently, for denizens of the Earth's northern hemisphere, this bright comet is certainly a lovely and inspiring sight -- visible here crowning the sky above Cortina d'Ampezzo, Italy on March 20. ... Undaunted by the artificial glow from one of the most famous urban skylines on Earth, comet Hale-Bopp shines above the city of New York, USA. ...

... Our everyday experience of the world around us is . ... An Inquiry-Based Classroom . I n our Everyday Classroom Tools project, we are seeking to immerse elementary school students in the Spirit of Inquiry, to help them begin to observe and learn from their experience. ... What the Everyday Classroom Tools project wishes to stress is that before there were encyclopedias, there were authors, and before there were scientific facts, there were curious people trying to explain the world around them. ...

... Since the invention of the telescope over 400 years ago, they have been built in many shapes and sizes, and for many different uses. Not many people know this, but the first telescopes were created by the Dutch around 1600 and were used to spot far-off enemy ships. Back then, telescopes were called БЂњlooking glassesБЂќ. ... With his telescope, Galileo became the first person to see many amazing features of our Solar System, including craters on the Moon and Jupiter's four largest moons. ...

In ancient times the solar system was thought to be the whole Universe, so the study of planetary motions was cosmology. ... The planets other than the Moon and Sun generally move West to East through the stars, but occasionally stop and move in the opposite direction ( retrograde motion). In order to explain the retrograde motion of the planets, the geocentric model of the Solar System shown above puts the planets on small circles called epicycles . ...

Here are various colour wedges that illustrate some of the colour schemes possible with `cubehelix' (together with files for use in ds9 or kvis). the `default' scheme: . ds9 or kvis . with different start colours: . ... with different hue values: . ... with different rotations: . ... rotating the other way around: . ... no colour rotation: . ... different gammas: . ... go to: cubehelix page . ...

... High-velocity clouds (HVCs) were discovered by Muller, Oort & Raimond (1963) in the 21-cm line emission of neutral, atomic hydrogen. They are gas clouds which are characterised by high radial velocities incompatible with a participation in the rotation of our Galaxy. ... This suggestion was seized by Braun & Burton (1999) who identified 66 compact high-velocity clouds (CHVCs) with positional and kinematic characteristics being compatible with a distribution across the entire Local Group. ...

... Get used to using the mouse and its buttons for such tasks. Figure out the function of each of the three mouse buttons. ... Fire up textedit application and practice editing text files. ... Figure out basic options like cut and paste of text around the file, saving and loading files, searching for strings in the text and replacing strings. ... Familiarise yourself with other UNIX functions by creating various files of text etc. and trying out the various functions listed in handouts. ...

METAR Wishlist Following is a list of items that I'd like to add to METAR or that others have requested. ... It'd be nice to have a lot of METARs which encompass various weather condition which we can test against. ... Sites around the world use similar (but slightly different) formats for their METARs. There is always a METAR format the parser will fail on. Calculate Heat Index and/or Wind Chill Both would be fairly easy to do, provided you get the formulas correct. ...

... High-resolution Herschel spectroscopy reveals the proto-planetary disk around the young star T Tau N . ... A study led by Linda Podio ( AstroFIt fellow at the Arcetri Observatory) with Inga Kamp (Kapteyn Institute, the Netherlands), Claudio Codella (Observatory of Arcetri) and other collaborators from Grenoble, UK and USA, makes use of high-resolution spectroscopic observations with HIFI on board the Herschel space observatory to characterize the disk around the young star T Tau N . ...