The 2017 PDC Hypothetical Asteroid Impact Scenario
A hypothetical asteroid impact scenario will be presented at the 2017 IAA Planetary Defense Conference (PDC), to be held in Tokyo, Japan, May 15-19, 2017. Although this scenario is realistic in many ways, it is completely fictional and does NOT describe an actual potential asteroid impact. The scenario is as follows:
An asteroid is discovered on March 6, 2017, at magnitude 21.1, and confirmed the following day. It is assigned the designation "2017 PDC" by the Minor Planet Center. (To reinforce the fact that this is not a real asteroid, we are using three letters in the designation, something that would never be done for an actual asteroid.)
Initial calculations indicate that 2017 PDC's orbit approaches well within 0.05 au to that of the Earth, and it is therefore classified as a Potentially Hazardous Asteroid (PHA). (The unit "au" stands for "astronomical unit", which is the mean distance of the Earth from the Sun, 149,597,870.7 km, or 92,955,807 miles.) The orbit is eccentric, extending from a distance of 0.88 au from the Sun at its closest point to 3.60 au at its farthest point. The asteroid's orbital period is 1225 days (3.35 years), and its orbital plane is inclined 6.3 degrees to the orbit of the Earth.
The day after 2017 PDC is discovered, JPL's Sentry impact monitoring system, along with ESA's similar CLOMON system, both identify several future dates when this asteroid could potentially impact the Earth. The date of the most likely potential impact is July 21, 2027 - over ten years away - but the probability of impact is very low, about 1 chance in 40,000.
When first detected, the asteroid is about 0.36 au (54 million kilometers or 33 million miles) from Earth, approaching our planet and getting brighter. It is observed extensively, and as the observational dataset grows, the impact probability for 2027 increases. The asteroid peaks in brightness at magnitude 20.4 on April 7, by which time the impact probability has risen to nearly 0.2 percent.