SLOOH Skylog

For the first time in history, an incoming near-Earth object has been discovered and its impact point known before it reached our planet. Making this feat all the more significant is the object’s small 3m size. Three meters is remarkable. In fact, some would say serendipitous - not the large threat that survey programs seek to discover and yet so small as to underscore the remarkable capability of our “spaceguard” systems.

At the time of its discovery, this incoming object - catalogued as 2008 TC3 - was just 450,000km from our planet and approaching at 12km per second. With less than twenty-fours before “impact”, scientists had to quickly fine-tune trajectory calculations and immediately dispatch notices. And they did it with great success. The calculations were so precise, and the news dispersed so efficiently, that astronomers all across the world were able to track and even photograph the incoming object. More importantly, the information was shared and received responsibly - without inciting panic or prompting end-of-world discourse.

Serendipity turned to good fortune when it was learned that the entry event would occur in a nighttime sky. The object’s small size and likely stony composition meant that it would not survive passage through the Earth’s atmosphere; thus, it would be a sight-and-sound fireball event rather than an actual impact. Of course, fireball events are far more spectacular against a darkened sky. Pilots flying near the expected entry zone - over Northern Sudan, Africa, to be exact - were notified, and at least one pilot did report seeing a bright fireball. However, no actual fireball images are yet known, nor has anyone yet reported hearing the estimated 1.1-2.1 kiloton explosion.

Nonetheless, the approach images are as impressive as any fireball picture. Again, this was a 3-meter object discovered only hours before Earth-entry and traveling at tremendous speed. Photographing it posed a formidable challenge. But that challenge was met with equally striking results. Among the small handful of public images, Slooh achieved the only known non-scientific observatory images and, even more exciting, provided the only real-time observing and imaging opportunity to the non-scientific community.

Although there was little time to prepare, and not every mission was successful, Slooh members did witness the object’s approach just two hours before Earth entry, and a few images even reveal its track across the sky. Again, serendipity played some role. With such short notice, only two random mission slots remained open; and it was exactly those two missions that proved successful. Even those last unsuccessful missions, which had been quickly swapped out for a final attempt just minutes before impact, united the Slooh community in a common passion - that love of space-science and a desire to better understand our universe. Watching the live event provided a very unique opportunity, perhaps even a once-in-a-lifetime experience, for Slooh members.

NEO 2008 TC3 entered the Earth’s atmosphere October 7, at 0243 UTC. It was discovered barely 24-hours earlier, on Monday morning, October 6, by Richard Kowalski of the Catalina Sky Survey team. His discovery was made using Mt. Lemmon’s 60-inch Cassegrain reflector. The Catalina Sky Survey, a NASA-funded project and part of the University of Arizona’s Lunar and Planetary Laboratory, consists of three cooperating surveys utilizing facilities in both Australia and the United States, including the Mt. Lemmon telescope located just north of Tucson, Arizona. The survey is one of several worldwide working toward greater NEO discoveries and better PHA threat assessment.

In this Slooh FITS image, processed by TonyE, we see 2008 TC3’s path revealed as a multi-colored segmented line intersecting a bright background star. This image was acquired 2008Oct07, at 00:43 UTC, exactly 2 hours before entry.