Twin asteroids passing by earth

An asteroid with a moon, or a binary asteroid, will pass by Earth tonight NZ time (1105 GMT). This wlil be it’s fourth flyby since it was discovered in in 1999, but it will be quite distant at it’s closest – more than 12 times more distant than our own Moon. An Asteroid with Its Own Moon Will Zip Past Earth Tonight

A very big asteroid with its own little moon is going to zip past Earth tonight (May 25) — close enough that, with some preparation and a decent telescope, amateur astronomers may spot it blotting out the stars.

This moon-and-asteroid system, called 1999 KW4, is made up of two rocks. The big one is about 0.8 miles (1.3 kilometers) wide, according to NASA, and shaped like a spinning top. The smaller one is more elongated and stretches 0.35 miles (0.57 km) along its longest dimension. It points lengthwise toward its much larger twin.

Together, the asteroid and its minimoon will pass Earth at such a strange, steep angle that NASA called them “the least accessible … for a spacecraft mission of any known binary near-Earth asteroid.”

The two asteroids will pass closest to Earth at 7:05 pm EDT (1105 GMT), when they’ll be just 3,219,955 miles (5,182,015 km) from the planet’s surface. That’s more than a dozen times the distance between the Earth and the moon in its orbit around our planet, and much too far for the space rocks to pose any threat. In fact, this is the fourth approach the binary asteroids have made toward Earth since they were discovered in 1999, and not the closest.

“1999 KW4 approaches within 0.05 AU of Earth several times each century,” NASA’s report on the object said. “This trend exists from at least [the year] 1600 [to] 2500.”

“AU” refers to “astronomical units,” a unit equal to the distance between Earth and the sun. So 0.05 AU is equal to one-twentieth the distance between Earth and sun, or about 4,650,000 miles (7,480,000 km). The two asteroids have passed even closer to Earth, without incident.

Bits of rock and ice are zinging around us all the time. The only difference is we are able to detect them now. Or at least some of them.

EarthSky reported that during the space rocks’ closest approach, they’ll be most visible in the Southern Hemisphere, appearing as fast-moving shadows against stars in the constellation Puppis. The two asteroids will remain visible for several days.

Visible for those with good enough telescopes and who know where to look – and have clear skies at night.

I haven’t heard of the Puppis Constellation. It appears to be close to the southern horizon at this time of year near Carina and Vela, lower in the southern sky than the Crux (Southern Cross).

puppis constellation,puppis stars,puppis location,puppis star map


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  1. Kitty Catkin

     /  26th May 2019

    The Puppis must be related to the Dog Star.

  2. Zedd

     /  26th May 2019

    cool pix 🙂


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