What'll happen when 3200 Phaethon sweeps past Earth?


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3200 Phaethon will sweep close to Earth – just 0.069 astronomical units (6.4 million miles, 10.3 million km, 26 lunar-distances) on December 16, 2017 at 23 UTC; translate to your time zone. Image via Osamu Ajiki (AstroArts)/ Ron Baalke (JPL) / Ade Ashford (AN)/ AstronomyNow. It will not be visible to the eye.

On the peak mornings of the 2017 Geminid meteor shower – December 13 and 14 – the moon will be in a waning crescent phase, visible only shortly before dawn, and near two planets before dawn. Even more importantly, a curious body known as 3200 Phaethon – sometimes called a rock-comet, thought to be the source of the Geminid meteor shower – will be gliding through space relatively near to Earth. It’ll come closest to Earth in its 523.5-day orbit only a few days after the Geminids’ peak, on December 16.

What will happen? No one knows for sure how many meteors you might see, or if 2017’s shower will be extra special because 3200 Phaethon is nearby. But it’s a fact that, when a parent comet is nearby, a meteor shower can be spectacular.

So plan to watch this shower in 2017!

Here’s everything you need to know about the 2017 Geminid meteor shower

Click for 10 tips on how to watch the 2017 Geminids.

Click here to see the Geminids online, via Virtual Telescope Project

The object 3200 Phaethon is located between the red tick marks at the center of this photo. Image acquired November 20, 2017 by Gianluca Masi of the Virtual Telescope Project. Gian will be hosting an online view of 3200 Phaethon. Click here for more details.

3200 Phaethon is a very interesting and mysterious object. It was one of the first known bodies in space that blurred the distinction between asteroids and comets. All the other meteors in annual showers are known to be icy debris left behind by comets, after all, but the Geminids are known to come from this strange asteroid-comet hybrid, which some call a rock-comet.

Asteroids are rockier, or more metallic, than comets. Their orbits tend to be more circular, while comets tend to have more elongated orbits. 3200 Phaethon, with its asteroid name, has an orbit that more closely resembles that of a comet than an asteroid. It also has mysterious ejections of dust, and dust tails, and astronomers have said it’s possible that the sun’s heat causes fractures on the surface of 3200 Phaethon, similar to mudcracks in a dry lake bed.

This closeup of an image of 3200 Phaethon by NASA’s STEREO A spacecraft shows a tail extending faintly toward lower left. Image via NASA/ SkyandTelescope.com.

3200 Phaethon was the first asteroid to be discovered via spacecraft on October 11, 1983. Astronomers Simon F. Green and John K. Davies noticed it while searching Infrared Astronomical Satellite (IRAS) data for moving objects. Charles T. Kowal confirmed it optically and said it was asteroid-like in appearance. The object received the provisional designation 1983 TB. Two years later, in 1985, using the convention for naming asteroids, astronomers assigned it its number and name: 3200 Phaethon.

An interesting feature of the orbit of 3200 Phaethon is that it comes very close to the sun, closer than any other named asteroid (though there are numerous unnamed asteroids that do sweep closer to the sun). That’s why it was given the name Phaethon, for the mythological son of the Greek sun god Helios.

Today, it’s classified as a potentially hazardous asteroid, which doesn’t mean it’s a threat to Earth. It just means two things. First, 3200 Phaethon is big – about 3 miles (5 km) wide – big enough to cause significant regional damage if it were to strike Earth. Second, it’s known to make periodic close approaches to Earth. A “close approach” in 2017 means 26 times farther than the moon. And, by the way, the orbit of 3200 Phaethon is exceedingly well studied, and astronomers know of no upcoming strike by this object in this foreseeable future.

In fact, in December 2017 – according to NASA NEO Earth Close Approaches – there are no fewer than 30 objects that’ll come closer than 3200 Phaethon. The closest of these will be 2017 WV12, a 20- to 40-meter-wide object that’s miss us by about a million miles (1.6 million km) on December 9.

The composition of 3200 Phaethon resembles that of asteroid 2 Pallas. Both are dark, B-type asteroids comprised of materials that have been modified by water. The first in this series of Hubble images is marked with the asteroid’s spin axis (top) and south pole. Image via B. E. Schmidt et. all / NASA / ESA/ SkyandTelescope.com.

On the peak nights of the 2017 Geminid meteor shower – nights of December 12 and 13, mornings of December 13 and 14 – the meteors will be radiating from near the star Castor in Gemini. On those nights, 3200 Phaethon won’t be far from Gemini on the sky’s dome. It’ll sweeping across a neighboring constellation, Perseus the Hero. Will you be able to see it with the eye? Not even kinda. Its magnitude is predicted to be around +10.7, making it far too faint to see with the eye alone.

Telescope users will be following 3200 Phaethon, however.

AstronomyNow has charts for telescope users, to help you track 3200 Phaethon

SkyandTelescope.com offers this chart of 3200 Phaethon’s track

And don’t forget to watch for 3200 Phaethon online, via Virtual Telescope Project

The Virtual Telescope Project will be offering online viewing this year of both the Geminids and 3200 Phaethon. Check out the times listed in the poster above. Click here to translate to your time zone. Click here to go to Virtual Telescope Project’s site.

Bottom line: 3200 Phaethon will brush relatively close to Earth on December 16, just a few nights after the peak of the 2017 Geminid meteor shower. Will 2017 be a fantastic year for the Geminids?

Deborah Byrd


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