Posted on 12/17/2015 12:46:11 PM PST by Red Badger
Graphic of what a asteroid of this type would look like - Nasa/ESA/M A Garlick/University of Warwick/University of Cambridge
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An asteroid will flyby Earth on Christmas Eve and should be visible with a telescope so long as skies are clear. The 2003 SD220 asteroid was discovered in 2003 and its 24 December appearance will be the first of five encounters with our planet over the next 12 years.
Very little is currently known about the asteroid, other than it is travelling at around five miles per second and has an absolute magnitude of around 16.9. Initially scientists had thought it measured around 1.3km in diameter, but now Nasa has said it is more likely to be 0.7km.
This suggests it measures around 1.3km in diameter. The Christmas Eve flyby is nothing to be concerned about – it will pass Earth at a distance of around 0.073 au (6.7 million miles) – in comparison the moon sits 238,900 miles from the planet.
Nevertheless, it is on Nasa's list of Near-Earth Object Human Space Flight Accessible (NHATS) Targets programme, meaning observations of it are important. "The 2015 apparition is the first of five encounters by this object in the next 12 years when it will be close enough for a radar detection.
"By obtaining radar ranging measurements at each observing opportunity, it may be possible to detect non-gravitational perturbations due to the Yarkovsky effect. If so, then we can obtain an estimate of the object's mass, information that is invaluable for understanding the object's bulk density and internal structure."
The December encounter will be close enough for ranging and some imaging but also serves as an "important preview" for the 2018 flyby, which will be much closer. At this time, the asteroid will come within 0.019 au (1.7 million miles) from Earth – so still not close enough to pose a threat but far nearer than most asteroids. It will then visit again three years later in 2021.
The effect appears to be similar to the 'solar sail', where "pressure" from sunlight pushes a spacecraft.
From wikipedia...
Solar sails (also called light sails or photon sails) are a form of spacecraft propulsion using the radiation pressure (also called solar pressure) from stars to push large ultra-thin mirrors to high speeds. Light sails could also be driven by energy beams to extend their range of operations, which is strictly beam sailing rather than solar sailing.
Solar sail craft offer the possibility of low-cost operations combined with long operating lifetimes. Since they have few moving parts and use no propellant, they can potentially be used numerous times for delivery of payloads.
Solar sails use a phenomenon that has a proven, measured effect on spacecraft. Solar pressure affects all spacecraft, whether in interplanetary space or in orbit around a planet or small body. A typical spacecraft going to Mars, for example, will be displaced by thousands of kilometres by solar pressure, so the effects must be accounted for in trajectory planning, which has been done since the time of the earliest interplanetary spacecraft of the 1960s. Solar pressure also affects the attitude of a craft, a factor that must be included in spacecraft design.[1]
The total force exerted on an 800 by 800 meter solar sail, for example, is about 5 newtons (1.1 lbf) at Earth's distance from the Sun,[2] making it a low-thrust propulsion system, similar to spacecraft propelled by electric engines."
Some of us have already read it. Hint: Time travelers find that Islamic Masters have enslaved our progeny.
Pertty much!...................
Well, the output of the sun is not constant, so we have a situation like Global Warming, IOW, they don’t know..........................
I was thinking of that while in Wal-Mart. Just think of how many drones we will have around in a few years. Better make that blind a bunker.
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Not only that, I need to start working on my Tractor Beam....
I bet they wouldn’t tell us if it was gonna hit........................
“1.36 AU, or 1.36 x 92.5 million miles = 125 million miles”
Too many decimals! Make it an even 9 million furlongs.
Yes of course! Who doesn't know THAT, pfft...(makes a "sure I knew that" face)
Oh!! You WILL cut that hair son! What are you a hippie??
< /childhood memories >
It’s that danged Yarkovsky effect! It’ll get you every time. Must be a Soviet trick, all part of their plan to steal our vital bodily fluids.
To put it in layman’s terms, The smaller the body the larger the effect of photons hitting it. But the sun’s output is not constant so it will take many years of measurements to average it out to determine the orbit accurately..............
Yes everything we needed to know.
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