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Tuesday, July 14, 2015

New Horizons has made the first visit to Pluto

Planets in astrology have a meaning different from the modern astronomical understanding of what a planet is. Before the age of telescopes, the night sky was thought to consist of two very similar components: fixed stars, which remained motionless in relation to each other, and "wandering stars".  Since the invention of the telescope, Western astrology has incorporated Uranus, Neptune,  Pluto, and other bodies into its methodology. The Indian  astrologists  have tended to retain the ancient seven-planet system.

The World is reading the fly-by and just  minutes before the long-awaited flyby took place at 7:49AM ET, NASA "teased" the final full-frame color image of Pluto set to be released before the event by publishing it on Instagram. It was taken at about 4PM ET on July 13th, according to NASA, from 476,000 miles away. The full-resolution image will be released after the flyby countdown is complete.

Nasa's New Horizons spacecraft has made the first visit to Pluto, speeding past at 14km per second. The probe was set to grab more pictures and other data as it passed 12,500km from Pluto.  Controllers got a last health status report, before the robotic craft turned its antenna away from the Earth to concentrate on its target. Only when New Horizons has its trove of images safely in its onboard memory will it call home again. This is not expected to happen until just after midnight (GMT) into Wednesday.  It means there will be a long, anxious wait for everyone connected with the mission, as they hold out for a signal that will be coming from almost five billion km away.

New Horizons' flyby of 2,370km-wide Pluto is a key moment in the history of space exploration.  "It's really historic what the US has done, and the New Horizons team is really proud to have been able to run that anchor leg and make this accomplishment." Says  Nasa science chief.  It marks the fact that every body in that system - from Mercury through to Pluto - will have been visited at least once by a space probe.

Pluto,  is the largest known object in the Kuiper belt, the second-most massive known dwarf planet in the Solar System and the tenth-most massive known body directly orbiting the Sun. Pluto is believed, to be  primarily made of rock and ice and is relatively small—about one-sixth the mass of the Moon and one-third its volume. Light from the Sun takes about 5.5 hours to reach Pluto at its average distance.

Pluto was discovered in 1930 and was originally considered the ninth planet from the Sun. After 1992, its status as a planet fell into question following the discovery of the Kuiper belt, a ring of objects beyond Neptune that includes Pluto among other large bodies. In 2005, Eris, which is 27% more massive than Pluto, was discovered, which led the International Astronomical Union (IAU) to define the term "planet" formally for the first time the following year.  This definition excluded Pluto and reclassified it as a member of the new "dwarf planet" category (and specifically as a plutoid).  Pluto has five known moons: Charon (the largest, with a diameter just over half that of Pluto), Styx, Nix, Kerberos, and Hydra.

Today, i.e., on  14 July 2015, the New Horizons probe will fly by Pluto, the first spacecraft to do so.  NASA plans for New Horizons to take detailed measurements and images of Pluto and its moons.  After this, there are plans for New Horizons to visit another object in the Kuiper belt.  When  New  Horizons makes its historic flyby of Pluto, it will be focusing in on just one face of the dwarf planet.  In the image NASA released of Charon yesterday, astronomers pointed out a collection of vaguely-defined features on the surface of Pluto’s biggest moon. Now, with the latest capture, the New Horizons team has confirmed that the big dent in the icy rock’s surface is in fact an impact crater, surrounded by a couple of deep canyons—one larger than Earth’s Grand Canyon.

At a press conference, New Horizons’ top dog Alan Stern announced that his team has calculated Pluto’s most accurate diameter yet: about 736 miles from one end to the other, give or take 6 miles.  Yet it is  impossible to measure Pluto’s size without also knowing its distance from Earth.  New Horizons is literally aiming for the unknown. The reason nobody knows Pluto’s exact location is because humans have only known about the planet for 85 years, which is about a third of the time it takes for Pluto to orbit the sun. The uncertainty is relatively small, but it affects all kinds of things.

New Horizons images have dramatically reduced uncertainty in Pluto's diameter. Stern reported Pluto's radius to be 1185 +/- 10 kilometers, so its diameter is 2370 +/- 20 km.  A larger diameter than thought means a lower density than thought, which means it has a higher proportion of ice to rock than thought. At the moment these comparisons are all qualitative; we'll see quantitative ones eventually.  New Horizons compositional measurements have confirmed that Pluto has a polar cap made of methane and nitrogen ices.

Astro-scientists are eagerly waiting for more closer images and that is very interesting.

With regards – S. Sampathkumar

14th July 2015.

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