Monday, June 24, 2024

4511 - ASTEROIDS - close to Earth?

-    4511  -   ASTEROIDS  -   close to Earth?      This asteroid will get closer to Earth than any in human history.   On Friday, April 13, 2029 a massive asteroid passes safely past Earth.   Asteroid “Apophis” is 1,230 feet  across, larger than 90% of space rocks.

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-------------------------------  4511  - ASTEROIDS  -   close to Earth?

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-    Asteroid “Apophis” will pass just 19,635 miles from Earth’s surface, the closest approach of an asteroid of this size that humankind has ever experienced. It will pass between Earth’s geostationary satellites and the Atlantic Ocean, just a tenth of the distance between Earth and the moon.

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-    “Apophis” will be visible to the naked eye. As it crosses the Atlantic, a few billion people in Europe, Africa and Asia can see it for a few hours in the night sky if skies are clear.

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-   “Asteroid 99942”,  “Apophis” was discovered on June 19, 2004, by astronomers at Kitt Peak National Observatory, who revealed that this stony, S-type asteroid orbits the sun every 324 days and comes close to Earth every decade or so. It is calculated that it could strike Earth in 2029, 2036 or 2068. It was, therefore, named after Apophis, the Egyptian demon of chaos and destruction.

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-    Even though there was only a 2.7% chance of a direct hit by Apophis, the devastation caused by it striking Earth led astronomers to try to understand its orbit in more detail.

 An asteroid’s orbit can only be calculated so far into the future. Although the following time it comes close to Earth, in 2044, it will be at a greater distance, astronomers can only rule out an impact for the next 100 years.

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-   The calculations are difficult because a close flyby, such as the one in 2029, will alter Apophis’ orbit so that it could strike Earth in a future orbit. However, astronomers have reduced the uncertainty in Apophis’ orbit from hundreds to just a few miles.

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-   The close pass in 2029 of Apophis is a rare opportunity to visit, so NASA already has a spacecraft in hot pursuit. This close pass is seen as the perfect opportunity to learn more about planetary defense and how an asteroid reacts to passing so close to a body with such enormous gravity. It’s thought that Apophis will be squeezed so much that asteroid quakes and landslides could result.

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-    Watching closely will be NASA’s OSIRIS-Apophis Explorer (OSIRIS-APEX) spacecraft. It’s the identical spacecraft that 2020 visited Asteroid Bennu. Then called OSIRIS-REx, NASA’s first asteroid sample-return mission, it returned a package of samples to Utah in September 2023 before re-directing towards Apophis in a mission extension costing NASA $200 million. OSIRIS-APEX will orbit Apophis for 18 months as it passes Earth in 2029.

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-   The European Space Agency is also considering a mission to Apophis, the Rapid Apophis Mission for SEcurity and Safety (RAMSES) mission, to launch in 2027.  What scientists learn from sending spacecraft to study Apophis in 2029 will be about how a relic of the early solar system reacts to gravity. The findings could be crucial for future Earthlings in hundreds of years when the massive asteroid poses a bigger threat.

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-    The key to protecting Earth from being hit by asteroids is knowing where all these are. More than 27,000 asteroids in our solar system had been overlooked in existing telescope images.   But,  thanks to a new AI-powered algorithm, we now have a catalog of them. The scientists behind the discovery say the tool makes it easier to find and track millions of asteroids, including potentially dangerous ones that might strike Earth someday.

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-    It is for those threatening space rocks that the world would need years of advance warning before trying to deflect them away from our planet.    Most of the newfound asteroids hover in the asteroid belt between Mars and Jupiter, where scientists have already cataloged over 1.3 million such rocky shards over the past 200 years.

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-    The latest bounty includes about 150 space rocks whose paths glide them within Earth's orbit;  however, none of these "near-Earth asteroids" seem to be on a collision path with our planet. Others are “Trojans” that follow Jupiter in its orbit around the sun.

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-    Astronomers conventionally find new asteroids by studying pockets of our sky over and over again, through telescope images gathered multiple times each night, usually every few hours. While planets, stars and galaxies in the background remain unchanged from one image to the next, asteroids are spotted as specks of light that move noticeably, which are then flagged and verified. From there, orbits of these asteroids are determined and monitored.

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-    This is really a job for AI.  In fact, AI tools designed for asteroid searches are already approaching levels attainable by humans.   The algorithm is known as “Tracklet-less Heliocentric Orbit Recovery”, or THOR, analyzed over 400,000 archival images of the sky maintained by the National Optical-Infrared Astronomy Research Laboratory, or NOIRLab.

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-    As long as there are about five observations in 30 days associated with the same pocket of the sky, the algorithm can get to work. It's trained on a large dataset that makes it capable of analyzing as many as 1.7 billion light dots in just a single telescope image. It is designed to scope out and connect a point of light from one image of the sky to another one in a different image, and determine whether both specks represent the same object.  More often than not, that indicates an asteroid moving through space.

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-    The scientists scaled their algorithm using Google Cloud, whose computational heft and data storage services made it easier for the scientists to test out thousands of orbits of asteroid candidates. 

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-    In 2022, the same team of scientists used THOR to discover 100 asteroids that had been undetected in existing telescope images. Other teams of astronomers have also leveraged AI to find new asteroids.

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-   Citizen scientists spearheaded training of an algorithm that led to the discovery of 1,000 new asteroids in archival images clicked by the Hubble Space Telescope. Last July, a software named “HelioLinc3D” designed to hunt for near-Earth asteroids found a 600-foot-wide space rock expected to approach within 140,000 miles of Earth. That's closer than the average distance between our planet and the moon.

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-    Scientists have so far spotted over 2,000 such "potentially hazardous asteroids" and estimate about 2,000 more are yet to be discovered. Detecting these space rocks in an effort to aid planetary defense is one of the tasks of the upcoming Vera C. Rubin Observatory in Chile, for which the asteroid-hunting HelioLinc3D software was developed.

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-    The 8.4-meter telescope, which is scheduled to start operations in 2025, will take images of the southern sky every night for at least a decade, each image covering 40-full-moons of area. Scientists say this cadence, supported by AI-based software like THOR and HelioLinc3D, could help the observatory find as many as 2.4 million asteroids,  double than those now cataloged in its first six months of operations.

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June 23, 2024           ASTEROIDS  -   close to Earth?                    4511

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