House-sized Asteroid Makes Close Earth Flyby Monday / See Dawn’s Ghostly Finger

Gianluca Masi used a 17-inch telescope to track the motion of asteroid 2014 UF56 on October 25. The small space rock will pass just 102,000 miles from Earth Monday afternoon CDT. Credit: Gianluca Masi

Discovered only yesterday, Earth-approaching 2014 UF56 will violate our planet’s personal space on Monday October 27th. At around 4 p.m. Central Daylight Time the ~45-foot-wide (14-m) boulder will tumble by at less the half the distance of the Moon.

With 90% of near-Earth asteroids larger than 0.6 miles (1 km) discovered, surveys are now focusing on finding 90% of objects larger than 460 feet (140-m). We have to take it a step at a time because the total number of near-Earth asteroids is in the millions. That’s why objects like 2014 UF56 pop up regularly in surveys each month. Every discovery adds one more piece to the grand puzzle that astronomers have been painstakingly assembling since the very first Earth-approaching asteroid, 433 Eros, was discovered in 1898.

The speedy boulder was found only yesterday. Despite passing so close to Earth, few if any of us will see the flyby with our eyes in a telescope. At brightest, 2014 UF56 will only reach magnitude +16, the limit for a 16-inch telescope, as it zips from Scutum through Capricornus. But you’ll be able to watch its mad dash all the same. Gianluca Masi, an Italian astrophysicist, will have his observatory open for business and stream the close passage live on his Virtual Telescope Project site starting at 2 p.m. CDT (7 p.m. UT) Monday October 27.

A cone of soft light tilts up from the eastern horizon about 2 hours before sunrise on October 22. The planet Jupiter is seen near its tip. Called zodiacal light, it’s sunlight reflecting off dust left by passing comets and asteroid collisions. Now through about November 4 is the best time to see the sight for northern hemisphere observers. Credit: Bob King

Earlier this week I went out before dawn to watch the Orionids, an annual meteor shower that originates from bits of dust and rock shed by Halley’s Comet. Every year during the third week of October we encounter Halley’s dregs and watch them fire up as meteors when they strike the atmosphere 70 miles over our heads. While only a few streaked the sky that morning, my outing coincided with the best display of another much larger phenomenon intimately tied to dust left behind by passing comets – the zodiacal light.

I look forward every fall to seeing the subtle beauty of this large, finger-shaped glow poking up from the eastern horizon. For northern hemisphere observers, it’s best visible before the start of dawn or about 2 hours to 90 minutes before sunrise. Then it towers more than halfway up in the eastern sky titled at about a 60-degree angle to the horizon.

The zodiacal light cone, which is centered on the Sun’s path through the zodiac called the ecliptic, tilts upward in late October reaching up to and even beyond the bright planet Jupiter. Credit: Bob King with Stellarium

To see the zodiacal light, you’ll need a dark, light pollution-free sky view of the eastern sky. and the will to arise “in the darkest hour”. It’s broadest and brightest near its base – similar to the summer Milky Way – but fades and tapers as you lift your gaze toward the bright planet Jupiter, now stationed near its tip.

The phenomenon gets its name from the “zodiac”, a band of a dozen constellations the Sun, Moon and planets pass through during their monthly, yearly and multi-year travels across the sky. When a comet’s orbit takes it within the inner solar system, the Sun vaporizes a portion of its ice, releasing dust and small rocks into space to create the comet’s coma and tail. Much of this dust is left behind in and near the mid-plane of the solar system where it forms a cloud of debris. Illuminated by scattered sunlight, we see it as the skinny-tipped finger of zodiacal light.

Crossed swords of light! The zodiacal light (left) meets the Milky Way in this beautiful image taken on October 1 this year. Though they’re similarly bright and large, the zodiacal light has a smooth texture without the clumpiness that characterizes the Milky Way. Credit: Damian Peach

During fall mornings and spring evenings, northern hemisphere skywatches see that mid-plane tilted up at a steep angle, high above the horizon hazes that would otherwise block the light from view. That’s what makes now an ideal time to set out for a look.

Much of the glowing comet dust will spiral into to the Sun over time and vaporize; a constant stream of comets, old and new, keeps it replenished. Near as I can figure, the zodiacal light is the single, largest visible structure in the solar system.  And to think it’s built of something as insubstantial as comet dust.

6 Responses

  1. jane

    I Was wondering if anyone mentioned the hoax about the 3 day blackout in Dec that snopes said was false but wanted to see what you know… I hate seeing people talk on social media spreading stories so is there anything in Nov or Dec that we should be concerned with??

    1. astrobob

      Hi Jane,
      Just more Internet hogwash. Goes back to the nonsense some folks predicted during the Mayan calendar rollover with the Sun lining up with the center of the galaxy. Of course, absolutely nothing happened then either except a few charlatans getting rich writing books and lecturing about the end of the world.

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