University of Arizona scientist and astronomer Douglas Clowe is as excited as a kid who’s just found where his parents hide the presents at Christmas. Years of planning and research have paid off, he believes, in the imaging of a collision between two galaxies that occurred over 100 million years in the past. The image shows something-or rather, a nothing-that scientists have debated for 70 years.

Science News Online is reporting that Clowe was able to capture imagery of dark matter, a substance that scientists say holds 90 percent of the universe together. The converse theory is that the universe is held together by a mutated version of the theory of gravity. The problem with the dark matter proposal is that it’s generally invisible, thus preventing scientists from proving its existence and validating their theory.

However, Clowe was able to use multiple telescopes and observatories to capture a violent merging of two galaxies that he says resulted in the appearance of dark matter that was unfettered by the explosive reaction.

“Dark matter particles don’t experience the same type of drag that slows down gas clouds,” Clowe told Science News.

Gravity works like duct tape for the universe, he says, keeping regular matter and dark matter merged into an existence so close that like Paris Hilton and her miniature dog, science can’t tell where one begins and the other ends. In a galactic collision like the one Clowe witnessed, gases expand and encounter resistance, effectively slowing the movement of both galaxies. Dark matter, however, is unimpeded by the release of force and passes right through. By his estimation, if dark matter didn’t exist, most of the mass from the collision would have accumulated in one spot, but the intrepid scientists witnessed “clumps” of matter scattered throughout the area. Read the rest of this entry »

Astronomers have found a planetary system similar to ours – a Jupiter-like world circling a Sun-like star in roughly the same orbit that Jupiter follows our Sun. Of the 100 or so other planetary systems known, this one more closely resembles our than any other. Reporting this, the BBC science editor Dr. David Whitehouse says that researchers speculate that this system may contain other worlds, such as smaller rocky planets like Earth, either in orbit around the star or around the Jupiter-like world itself. The planet’s parent star, called HD 70642, is too faint to be seen with the unaided eye, but is easily visible in the southern sky using binoculars. At just 95 light-years away (a light year is equal to 9,500,000,000,000 kilometers) the gas giant planet, bathed in the light of a yellow-dwarf star is on our galactic doorstep.

Like Jupiter, its atmosphere could be mottled and streaked with wind patterns and weather systems. Dark red methane clouds may scurry across its face beneath a high altitude frosting of bright ammonia crystals. At its poles, aurora may glisten and lightening bolts pulse across its night-time face. The planet detected orbiting HD 70642 is not the first Jupiter-class world to be found circling another star. All the planetary systems found so far contain gas giants like Jupiter. But the Jupiter like world stirs memories. It circles its parent star at a distance of 467 million kilometers (290 million miles), not a lot different from 778 million kilometer (483 million miles) that Jupiter is away from our Sun. The similarities do not end there. This new world circles its star every 6 years; our Jupiter takes 12 years.

Intriguing certainly, but the interest in this system is not principally because of what we know is there, but rather because of what else we suspect may be lurking unseen around the star and its planet. There could be other worlds smaller and rocky – possibly Earth-like. These are below our detectability. Read the rest of this entry »

You must have realized that the length of a day – as based on daylight or the period between sunrise and sunset, varies over the course of a year. While the days tend to be longer than nights in summer, tables turn in winter wherein days become shorter than nights. The change is so gradual that you fail to notice that there is a longest day and shortest day of the year. Starting from the longest day of the year, the length of a day decreases gradually until it is the shortest day. Similarly, starting from the shortest day of the year, the length of a day increases gradually until it is the longest day of the next calendar year. The entire phenomenon revolves around solstice – one of the basic concepts of geography, which is dependent on the seeming movement of the Sun between the Tropic of Cancer and Tropic of Capricorn.

Winter Solstice: Shortest Day of the Year

The occurrence of the longest or shortest day of the year is attributed to the astronomical event known as ‘solstice’ which occurs twice in a calendar year – first when the apparent position of the Sun is at its northernmost limit (Tropic of Cancer/23.5°North) and again, when the apparent position of the Sun is at its southernmost limit (Tropic of Capricorn/23.5°South.) This event of astronomy is further categorized into two parts – summer solstice, which is the longest day of the year, and winter solstice, which is the shortest day of the year. When the Sun is at its northernmost limit at 23.5°North, it is referred to as summer solstice, and when this solar body is at its southernmost limit at 23.5°South, it is referred to as winter solstice. Similarly, when the Sun’s apparent position is at the equator, it is referred to as equinox – which occurs twice a year. This, however, only applies to the northern hemisphere of the Earth.

In southern hemisphere, summer solstice occurs when the Sun is at its southernmost limit at 23.5°South and winter solstice occurs when the Sun is at its northernmost limit at 23.5°North. Owing to the differences in apparent position of the Sun, each of the two hemispheres experience summer solstice and winter solstice at different times of the year. When the Sun is positioned at the northernmost limit, the northern hemisphere experiences more daylight as compared to southern hemisphere. Contrary to this, when the Sun is at its southernmost extreme the southern hemisphere experiences more of daylight as compared to its northern counterpart. If you happen to be a resident of northern hemisphere – the chances of which are more, you will experience the longest day when the Sun is at Tropic of Cancer, and shortest when it is at Tropic of Capricorn. Read the rest of this entry »