четверг, 2 июля 2015 г.

Venus, Jupiter, and Noctilucent Clouds


Have you seen the passing planets yet? Today the planets Jupiter and Venus pass within half a degree of each other as seen from Earth. This conjunction, visible all over the world, is quite easy to see -- just look to the west shortly after sunset. The brightest objects visible above the horizon will be Venus and Jupiter, with Venus being the brighter of the two. Featured above, the closing planets were captured two nights ago in a sunset sky graced also by high-level noctilucent clouds. In the foreground, the astrophotographer's sister takes in the vista from a bank of the Sec Reservoir in the Czech Republic. She reported this as the first time she has seen noctilucent clouds. Jupiter and Venus will appear even closer together tonight and will continue to be visible in the same part of the sky until mid-August. via NASA http://ift.tt/1IrMOeT

среда, 1 июля 2015 г.

An Unusual Mountain on Asteroid Ceres


What created this large mountain on asteroid Ceres? No one is yet sure. As if in anticipation of today being Asteroid Day on Earth, the robotic spacecraft Dawn in orbit around Ceres took the best yet image of an unusually tall mountain on the Asteroid Belt's largest asteroid. Visible at the top of the featured image, the exceptional mountain rises about five kilometers up from an area that otherwise appears pretty level. The image was taken about two weeks ago from about 4,400 kilometers away. Although origin hypotheses for the mountain include volcanism, impacts, and plate tectonics, clear evidence backing any of these is currently lacking. Also visible across Ceres' surface are some enigmatic light areas: bright spots whose origin and composition that also remain an active topic of investigation. Even though Dawn is expected to continue to orbit Ceres, officially dubbed a dwarf planet, for millions of years, the hydrazine fuel used to point Dawn's communications antenna toward Earth is expected to run out sometime next year. via NASA http://ift.tt/1U2H5k3

понедельник, 29 июня 2015 г.

All the Colors of the Sun


It is still not known why the Sun's light is missing some colors. Here are all the visible colors of the Sun, produced by passing the Sun's light through a prism-like device. The spectrum was created at the McMath-Pierce Solar Observatory and shows, first off, that although our white-appearing Sun emits light of nearly every color, it does indeed appear brightest in yellow-green light. The dark patches in the above spectrum arise from gas at or above the Sun's surface absorbing sunlight emitted below. Since different types of gas absorb different colors of light, it is possible to determine what gasses compose the Sun. Helium, for example, was first discovered in 1870 on a solar spectrum and only later found here on Earth. Today, the majority of spectral absorption lines have been identified - but not all. via NASA http://ift.tt/1IkZVOI

воскресенье, 28 июня 2015 г.

Stars of a Summer Triangle


Rising at the start of a northern summer's night, these three bright stars form the familiar asterism known as the Summer Triangle. Altair, Deneb, and Vega are the alpha stars of their respective constellations, Aquila, Cygnus, and Lyra, nestled near the Milky Way. Close in apparent brightness the three do look similar in these telescopic portraits, but all have their own stellar stories. Their similar appearance hides the fact that the Summer Triangle stars actually span a large range in intrinsic luminosity and distance. A main sequence dwarf star, Altair is some 10 times brighter than the Sun and 17 light-years away, while Vega, also a hydrogen-fusing dwarf, is around 30 times brighter than the Sun and lies 25 light-years away. Supergiant Deneb, at about 54,000 times the solar luminosity, lies some 1,400 light-years distant. Of course, with a whitish blue hue, the stars of the Summer Triangle are all hotter than the Sun. via NASA http://ift.tt/1Ij77Lp

суббота, 27 июня 2015 г.

Planet Aurora


What bizarre alien planet is this ? It's planet Earth of course, seen through the shimmering glow of aurorae from the International Space Station. About 400 kilometers (250 miles) above, the orbiting station is itself within the upper realm of the auroral displays, also watched from the planet's surface on June 23rd. Aurorae have the signature colors of excited molecules and atoms at the low densities found at extreme altitudes. The eerie greenish glow of molecular oxygen dominates this view. But higher, just above the space station's horizon, is a rarer red band of aurora from atomic oxygen. The ongoing geomagnetic storm began after a coronal mass ejection's recent impact on Earth's magnetosphere. via NASA http://ift.tt/1J9Ei2q

пятница, 26 июня 2015 г.

Star Trails Above Table Mountain


Stars trail above and urban lights sprawl below in this moonlit nightscape from Cape Town, South Africa, planet Earth. The looming form of Table Mountain almost seems to hold terrestrial lights at bay while the stars circle the planet's South Celestial Pole. This modern perspective on the natural night sky was captured in June 2014, the scene composed of over nine hundred, stacked 30 second exposures. The stunning result was chosen as the winner in the Against the Lights category, a selection from over 800 entries in The World at Night's 2015 International Earth and Sky Photo Contest. via NASA http://ift.tt/1e5iHNQ

четверг, 25 июня 2015 г.

Triple Conjunction Over Galician National Park


What are those bright objects hovering over the horizon? Planets -- and the Moon. First out, the horizon featured is a shoreline of the Atlantic Ocean that occurs at the Galicia National Park in northern Spain. Next furthest out, on the left, is the Moon. Easily the brightest object on the night sky, the Moon here was in only a crescent phase. The next furthest out, on the right, is the planet Venus, while planet Jupiter is seen at the top of the triangle. The long exposure from our rapidly rotating Earth made all of celestial objects -- including the far distant stars -- appear as slight arcs. The featured image was taken last Sunday night. Although the Moon's orbit has now taken it away from this part of the sky, the planets Venus and Jupiter can be seen superposed just after sunset until mid-August. The closest apparent separation of Venus and Jupiter will occur in one week, when the two planets will appear separated by less than the angular diameter of the Moon. via NASA http://ift.tt/1fALvPa