Register
Page 120 of 120 FirstFirst ... 2070110118119120
Results 1,191 to 1,194 of 1194
  1. #1191
    Moderator at Work ilan's Avatar
    Join Date
    Sep 2015
    Location
    Celestial Fields
    Posts
    8,403
    Rep Power
    250
    Overview of Our Solar System
    NASA | Solar System Exploration

    And now for something completely different: A site to explore our solar system that was created by NASA.


    Code:
    https://solarsystem.nasa.gov/solar-system/our-solar-system/overview/
    Last edited by ilan; 08-14-2019 at 12:18 AM.
    Beginner's Guide for Rocket, NFPS and IKS66...
    http://iptvtalk.net/showthread.php?2...-you-should-do

    Kodi Options for Rocket, NFPS and IKS66...
    http://iptvtalk.net/forumdisplay.php?71-Kodi

    Check the Announcement Section...
    http://iptvtalk.net/forumdisplay.php...-Announcements

  2. #1192
    Moderator at Work ilan's Avatar
    Join Date
    Sep 2015
    Location
    Celestial Fields
    Posts
    8,403
    Rep Power
    250
    A massive star completely destroyed by a supernova is puzzling scientists
    Korey Haynes | Published: Friday, August 16, 201

    The death blast of a star some 200 times the mass of the Sun, challenges theories about how such massive stars die.


    Supernova 2016iet is an example of one of the most extreme types of stellar explosions, though it has some odd features.
    Gemini Observatory/NSF/AURA/ illustration by Joy Pollard
    In November of 2016, the sharp-eyed Gaia spacecraft spied a supernova that exploded some billion light-years from Earth. Astronomers followed up with more telescopes, and quickly realized that this supernova Ė dubbed SN2016iet Ė was an odd one in many ways.

    For one, the star that caused the supernova seemed to orbit far in the hinterlands of its tiny, previously unknown dwarf galaxy, some 54,000 light-years from its center. Most massive stars are born in denser clusters of stars, and itís a puzzle how this one came to form so far out.

    And this star was extremely massive, starting life as some 200 times the mass of the Sun, near the upper limit of what scientists think is possible for a single star to weigh.

    The supernova itself also left what appeared to be the signature of two explosions, separated by about 100 days. Astronomers think this isnít actually due to multiple explosions, but from the explosion hitting different layers of material the star lost in the years leading up to its death and left scattered around it in a diffuse cloud.

    The star meets many of the criteria for something called a pair-instability supernova, a kind of explosion that some extremely massive stars should theoretically undergo. Such an event leaves the star completely destroyed, leaving nothing behind. But finding examples of these rare stellar explosions has been difficult, and this is still one of the first scientists have discovered. And even in that rare company, SN2016iet remains an oddball find.

    Researchers led by graduate student Sebastian Gomez from the Harvard Center for Astrophysics published their results August 15 in The Astrophysical Journal.


    The same patch of sky is shown in 2014, before the supernova exploded, and in 2018,
    highlighting just how far outside the galaxy the explosion occurred.
    _________________________________

    Imagine the amount of energy 2016iet emitted when it gave up the ghost! It's awesome to see an actual image of the supernova's remnants and the host galaxy in the second image. - ilan
    Last edited by ilan; 08-18-2019 at 12:22 PM.
    Beginner's Guide for Rocket, NFPS and IKS66...
    http://iptvtalk.net/showthread.php?2...-you-should-do

    Kodi Options for Rocket, NFPS and IKS66...
    http://iptvtalk.net/forumdisplay.php?71-Kodi

    Check the Announcement Section...
    http://iptvtalk.net/forumdisplay.php...-Announcements

  3. #1193
    Moderator at Work ilan's Avatar
    Join Date
    Sep 2015
    Location
    Celestial Fields
    Posts
    8,403
    Rep Power
    250
    And brief history of Saturn's amazing rings
    Vahe Peroomian, The Conversation | Published: Tuesday, August 20, 2019

    Although the rings of Saturn may look like a permanent fixture of the planet, they are ever-changing. New analyses of the rings reveal how and when they were made ó and whether they'll last.


    With giant Saturn hanging in the blackness and sheltering Cassini from the Sunís blinding glare,
    the spacecraft viewed the rings as never before.
    NASA/JPL/Space Science Institute
    Many dream of what they would do had they a time machine. Some would travel 100 million years back in time, when dinosaurs roamed the Earth. Not many, though, would think of taking a telescope with them, and if, having done so, observe Saturn and its rings.

    Whether our time-traveling astronomer would be able to observe Saturnís rings is debatable. Have the rings, in some shape or form, existed since the beginnings of the solar system, 4.6 billion years ago, or are they a more recent addition? Had the rings even formed when the Chicxulub asteroid wiped out the dinosaurs?

    I am a space scientist with a passion for teaching physics and astronomy, and Saturnís rings have always fascinated me as they tell the story of how the eyes of humanity were opened to the wonders of our solar system and the cosmos.

    Our view of Saturn evolves

    When Galileo first observed Saturn through his telescope in 1610, he was still basking in the fame of discovering the four moons of Jupiter. But Saturn perplexed him. Peering at the planet through his telescope, it first looked to him as a planet with two very large moons, then as a lone planet, and then again through his newer telescope, in 1616, as a planet with arms or handles.

    Four decades later, Christiaan Huygens first suggested that Saturn was a ringed planet, and what Galileo had seen were different views of Saturnís rings. Because of the 27 degrees in the tilt of Saturnís rotation axis relative to the plane of its orbit, the rings appear to tilt toward and away from Earth with the 29-year cycle of Saturnís revolution about the Sun, giving humanity an ever-changing view of the rings.

    But what were the rings made of? Were they solid disks as some suggested? Or were they made up of smaller particles? As more structure became apparent in the rings, as more gaps were found, and as the motion of the rings about Saturn was observed, astronomers realized that the rings were not solid, and were perhaps made up of a large number of moonlets, or small moons. At the same time, estimates for the thickness of the rings went from Sir William Herschelís 300 miles in 1789, to Audouin Dollfusí much more precise estimate of less than two miles in 1966.

    Astronomers understanding of the rings changed dramatically with the Pioneer 11 and twin Voyager missions to Saturn. Voyagerís now famous photograph of the rings, backlit by the Sun, showed for the first time that what appeared as the vast A, B and C rings in fact comprised millions of smaller ringlets.

    The Cassini mission to Saturn, having spent over a decade orbiting the ringed giant, gave planetary scientists even more spectacular and surprising views. The magnificent ring system of Saturn is between 10 meters and one kilometer thick. The combined mass of its particles, which are 99.8% ice and most of which are less than one meter in size, is about 16 quadrillion tons, less than 0.02% the mass of Earthís Moon, and less than half the mass of Saturnís moon Mimas. This has led some scientists to speculate whether the rings are a result of the breakup of one of Saturnís moons or the capture and breakup of a stray comet.

    The dynamic rings

    In the four centuries since the invention of the telescope, rings have also been discovered around Jupiter, Uranus and Neptune, the giant planets of our solar system. The reason why the giant planets are adorned with rings and Earth and the other rocky planets are not was first proposed by Eduard Roche, a French astronomer in 1849.

    A moon and its planet are always in a gravitational dance. Earthís moon, by pulling on opposite sides of the Earth, causes the ocean tides. Tidal forces also affect planetary moons. If a moon ventures too close to a planet, these forces can overcome the gravitational ďglueĒ holding the moon together and tear it apart. This causes the moon to break up and spread along its original orbit, forming a ring.

    The Roche limit, the minimum safe distance for a moonís orbit, is approximately 2.5 times the planetís radius from the planetís center. For enormous Saturn, this is a distance of 87,000 kilometers above its cloud tops and matches the location of Saturnís outer F ring. For Earth, this distance is less than 10,000 kilometers above its surface. An asteroid or comet would have to venture very close to the Earth to be torn apart by tidal forces and form a ring around the Earth. Our own Moon is a very safe 380,000 kilometers away.

    The thinness of planetary rings is caused by their ever-changing nature. A ring particle whose orbit is tilted with respect to the rest of the ring will eventually collide with other ring particles. In doing so, it will lose energy and settle into the plane of the ring. Over millions of years, all such errant particles either fall away or get in line, leaving only the very thin ring system people observe today.

    During the last year of its mission, the Cassini spacecraft dived repeatedly through the 7,000 kilometer gap between the clouds of Saturn and its inner rings. These unprecedented observations made one fact very clear: The rings are constantly changing. Individual particles in the rings are continually jostled by each other. Ring particles are steadily raining down onto Saturn.

    The shepherd moons Pan, Daphnis, Atlas, Pandora and Prometheus, measuring between eight and 130 kilometers across, quite literally shepherd the ring particles, keeping them in their present orbits. Density waves, caused by the motion of shepherd moons within the rings, jostle and reshape the rings. Small moonlets are forming from ring particles that coalesce together. All this indicates that the rings are ephemeral. Every second up to 40 tons of ice from the rings rain down on Saturnís atmosphere. That means the rings may last only several tens to hundreds of millions of years.

    Could a time-traveling astronomer have seen the rings 100 million years ago? One indicator for the age of the rings is their dustiness. Objects exposed to the dust permeating our solar system for long periods of time grow dustier and darker.

    Saturnís rings are extremely bright and dust-free, seeming to indicate that they formed anywhere from 10 to 100 million years ago, if astronomersí understanding of how icy particles gather dust is correct. One thing is for certain. The rings our time-traveling astronaut would have seen would have looked very different from the way they do today.
    __________________________________________

    That is such a cool picture of Saturn and its rings with the sun streaming from behind. At first, I thought it was an artist's conception, but instead it is the real deal! - ilan


    Last edited by ilan; 08-21-2019 at 08:05 PM.
    Beginner's Guide for Rocket, NFPS and IKS66...
    http://iptvtalk.net/showthread.php?2...-you-should-do

    Kodi Options for Rocket, NFPS and IKS66...
    http://iptvtalk.net/forumdisplay.php?71-Kodi

    Check the Announcement Section...
    http://iptvtalk.net/forumdisplay.php...-Announcements

  4. #1194
    Moderator at Work ilan's Avatar
    Join Date
    Sep 2015
    Location
    Celestial Fields
    Posts
    8,403
    Rep Power
    250
    Summer Triangle on August Evenings
    Posted by Bruce McClure in TONIGHT | August 17, 2019




    Weíve recently seen Orionís return to the east before dawn, which means our northern summer is beginning to draw to a close. But the Summer Triangle asterism still rules the skies. It pops out first thing at nightfall and climbs highest up for the night at late evening. From mid-northern latitudes, Vega Ė the Summer Triangleís brightest star Ė shines high overhead around 10 p.m. local daylight saving time (9 p.m. local standard time). Altair resides to the southeast (lower left) of Vega, and Deneb lies to Vegaís east (left).

    The Summer Triangle is not a constellation. It is three bright stars in three different constellations, as the wonderful photo below Ė by Susan Jensen in Odessa, Washington Ė shows.


    As the stars drift westward during the night, Deneb will swing upward to replace Vega as the overhead star some two hours later. Of course, the stars arenít really moving. Itís the Earthís rotation that causes the stars to move westward during the night, and the sun to go westward during the day.

    Because the three stars making up the Summer Triangle are 1st-magnitude stars, you can easily see the brilliant Summer Triangle on moonlit nights. However, you need a dark sky free of moonlight to see the great swath of stars known as the Milky Way passing in between the Summer Triangle stars Vega and Altair. The star Deneb bobs in the middle of this river of stars that meanders through the Summer Triangle, arcing across the sky from horizon to horizon. Although every star that you see with the unaided eye is actually a member of our Milky Way galaxy, the term Milky Way often refers to the cross-sectional view of the galactic disk, whereby innumerable far-off suns congregate into a cloudy trail of stars.

    Make friends with the Summer Triangle and its three brilliant stars Ė Vega, Deneb and Altair Ė tonight. Note the great boulevard of stars that streams right through the Summer Triangle on an inky-dark night. Thatís actually an edgewise view into the flat disk of our Milky Way galaxy.

    By the way, you can see the Summer Triangle in the Southern Hemisphere, too Ė although there do you call it the Winter Triangle? I wonder. South of the equator, people see an upside-down version of tonightís sky scene, in contrast to our northern perspective. Late tonight, Southern Hemisphere residents will see Altair at the top of the Summer Triangle, and Vega and Deneb sparkling at the bottom.
    Beginner's Guide for Rocket, NFPS and IKS66...
    http://iptvtalk.net/showthread.php?2...-you-should-do

    Kodi Options for Rocket, NFPS and IKS66...
    http://iptvtalk.net/forumdisplay.php?71-Kodi

    Check the Announcement Section...
    http://iptvtalk.net/forumdisplay.php...-Announcements

 

 
Page 120 of 120 FirstFirst ... 2070110118119120

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •