Still unidentified, WT1190F falls to Earth tonight

Unidentified object WT1190F is thought to be a spent third stage, called the S-IVB, of the Saturn V rocket used to propel nine manned missions to the Moon. Photo Credit: NASA

An unidentified object discovered by the Catalina Sky Survey on Oct. 3 will fall to Earth tonight, burning up in the sky about 60 miles (100 km) off the coast of Sri Lanka.

Designated WT1190F, the six-foot (two-meter) wide object is believed to be man-made, possibly an old rocket booster used to launch one of the Apollo Moon missions, China’s Chang’e 3 Moon lander, or an older Chinese or Russian Moon mission.

While the first two stages of the Saturn V rockets used in the nine Apollo Moon missions fell back to Earth, the third stage of each one, which took the spacecraft into lunar orbit, did not.

Three 90-second exposures show WT1190F crossing the Rosette Nebula. These images were taken on Nov. 11, 2015, at the Konkoly Observatory in Hungary. (Click to view GIF.) Photo Credit: Krisztián Sárneczky / Konkoly Observatory

The object’s size and its low density were determined from astronomers’ observation of its orbit.

With a density ten percent that of water, WT1190F is pushed around in space more easily than denser objects. This is because the radiation pressure, or push exerted by photons of light from the Sun, is proportional to any celestial object’s area-to-mass ratio.

Scientists have not completely ruled out the possibility of WT1190F being a small asteroid, but the low density suggests it more likely is something with a hollow shell, a description that fits a rocket’s upper stage.

It was first observed in 2013 in a trans-lunar orbit, meaning an orbit around the Earth that takes it beyond the Moon.

At 6:20 GMT (1:20 a.m. EST) on Friday, Nov. 13, it will re-enter Earth’s atmosphere, where all or most of the object is likely to burn up and create a bright fireball.

The exact time of impact was confirmed over the last few days by astronomers who observed its last decaying orbits.

Three 90-minute exposures of WT1190F, taken last night by the Konkoly Observatory in Hungary, show it racing in front of the Rosette Nebula.

Over the last week and a half, the European Space Agency’s Near-Earth Object’s Coordination Center has been conducting observation campaigns to gather as much data as possible on the object.

Such studies could test our ability to prepare adequately for an actual asteroid impact.

WT1190F will be traveling very fast as it enters Earth’s atmosphere, at a rate of three arc minutes per second or three degrees per minute.

Viewers in Europe should be able to spot it about an hour before impact.

In the single minute from 6:18 to 6:19 GMT (1:18 to 1:19 EST), the object will move one hour of right ascension and fall 34 degrees in declination and will brighten from a magnitude of +8 to +4.5. The latter puts it well within view of the naked eye.

To follow the object, visit Project Pluto or JPL’s Horizons site.

The impact point of WT1190F is expected to be about 60 miles south of Sri Lanka. Image Credit: Bill Gray / Project Pluto

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Laurel Kornfeld

Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.