Asteroid 99942 Apophis was identified as one of the most dangerous asteroids that could
impact Earth after its detection in 2004.
However, when astronomers observed Apophis and learned more about its orbit, their assessment
of its influence changed.
Now, astronomers have concluded that there is no risk of Apophis reaching our planet
for at least a century, thanks to the results of a new radar observation campaign paired
with precise orbit analysis.
Apophis is a huge near-Earth asteroid, approximately 1,100 feet or 335 meters wide.
It rose to prominence in 2004 when early observations revealed that it might collide with Earth
around 2029.
Though it will pass spectacularly close to Earth in 2029, a collision has been deemed
out.
Apophis is expected to pass Earth on Friday, April 13, 2029, at a nominal distance of 19,662
miles (31,643 kilometers).
This is in comparison to the moon’s average distance of about a quarter-million miles
(380,000 km).
On April 13, 2029, when the stadium-sized asteroid 99942 Apophis passes uncomfortably
near to Earth, a team of South Korean scientists plans to greet it in space and return a sample
to Earth.
The South Korean plan is to approach Apophis in January 2029, just before it makes its
close approach to Earth.
A spacecraft launching from Earth in late 2027 would follow the asteroid as it passes
by our planet.
The objective is to study and map Apophis the entire way, looking for possible structural
changes resulting from its close encounter with Earth and the gravitational forces of
our planet.
Young-Jun Choi from the Korea Astronomy and Space Science Institute, who presented the
concept at the Korea Space Forum, explained that they would have real-time data from the
asteroid when gravity has the greatest impact on the rock.
For example, earthquakes or landslides occurring on the asteroid.
Choi also highlighted the possibility of landing on the asteroid and returning to Earth with
a sample, similar to Japan’s Hayabusa missions and NASA’s Osiris-Rex missions, which have
both sampled other asteroids.
For the record, Apophis will approach Earth at a distance of 20,000 miles (32,000 kilometers),
which is extremely rare for such a massive object.
However, there’s zero chance of impact.
At a 2020 conference on Apophis and its 2029 visit, the Korean team noted that with a dedicated
rendezvous mission to Apophis, they should be able to fill in the knowledge gaps in their
scientific understanding of gravitational effects that could be employed for planetary
defense when there is a real threat.
Earlier this year, NASA described the 2029 flyby as a “unique opportunity for astronomers
to acquire a close-up view of a solar system relic that is now merely a scientific curiosity
and not a direct threat to our planet.
To arrive at the latest Apophis calculations, astronomers used the 70-meter (230-foot) radio
antenna at the Deep Space Network’s Goldstone Deep Space Communications Complex near Barstow,
California, to carefully track Apophis’ motion.
As the team analyses data from the radio antenna, they hope to learn more about the asteroid’s
shape.
Previous observations have suggested that Apophis has a “bilobed” or peanut-like
look.
This is a relatively frequent shape among the near-Earth asteroids larger than 660 feet
(200 meters) in diameter; at least one out of every six has two lobes.
Astronomers are also seeking to learn more about the asteroid’s rotation rate and the
axis it spins around, known as its spin state.
They’ll be able to determine the asteroid’s orientation with Earth when it collides with
our planet’s gravitational field in 2029, which could change its spin state and potentially
cause “asteroid quakes”.
According to NASA, Apophis will first be seen in the Southern Hemisphere, appearing as a
speck of light traveling across Australia during this close encounter.
It will be above the Atlantic Ocean at its closest approach to Earth.
It will travel so fast that it will span the Atlantic in less than an hour and will traverse
the United States in the late afternoon/early evening within the next hour.
Calculations show that Apophis will reach a visual magnitude of 3.1 during this approach,
comparable to the stars in the Little Dipper.
In 2029, Apophis is anticipated to be visible without a telescope from parts of Australia,
Western Asia, Africa, and Europe.