What is Apophis? Apophis is a near-Earth asteroid, which means that its orbit around
the Sun places it within 1.3 times the Earth-Sun distance.
It belongs to a group of asteroids known as the Potentially Hazardous Asteroids (PHAs),
which are asteroids with orbits that bring them dangerously close to Earth now and in
the future. After its discovery in 2004, the stadium-sized
asteroid was given a 2.7% chance of hitting Earth in April 2029, causing a lot of media
attention. On the 13th of April, 2029, Earth will have
a dramatic close encounter with Apophis. The 1,120-foot-wide (340-meter) object will pass
close to Earth at approximately 19,000 miles (31,000 kilometers), bringing it closer to
Earth than most geostationary communication satellites.
Because of Apophis’ massive size, its close passage will be so brilliant that around 2
billion people will be able to see it with the naked eye.
The asteroid will first appear in the southern hemisphere as a bright star speeding across
the sky from east to west, passing over Australia, followed by the Indian Ocean, and finally
crossing the equator over Africa. Luckily, this unique historic event will not
be as catastrophic as experts had predicted. Scientists were initially uncertain if Apophis’
passage would result in a collision with Earth. Even after this risk was ruled out, scientists
could not rule out the possibility that Earth’s gravitational effects could influence the
asteroid in such a way that one of its subsequent trips could result in a collision.
Even though we now know Apophis will not strike Earth in the foreseeable future, the asteroid
has occupied the top spot on the European Space Agency’s “impact risk list” of
PHAs and NASA’s Sentry Risk Table for the past 17 years.
And, owing to its upcoming visits, its time as a focus of intense scientific interest
is only getting started. With the threat of an Apophis collision averted,
for the time being, scientists can now concentrate on gathering scientific data from its flybys.
Since there are still seven years of planning remaining until its next visit, the sky is
indeed the limit for Apophis exploration. David Farnocchia, an astrophysicist at NASA’s
Jet Propulsion Laboratory (JPL), and his colleagues, who are investigating the asteroid’s trajectory,
will take advantage of this scientific opportunity by analyzing how Apophis reacts to tidal forces
when it is close to Earth. The rotation rate of Apophis could vary due
to its close approach to Earth. Astronomers are also seeking to learn more about the asteroid’s
rotation rate and the axis around which it spins, referred to as its spin state.
They’ll be able to calculate 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
produce “asteroid quakes”. It’s difficult to predict what an impact
between our planet and an asteroid the size, shape, and density of Apophis would look like.
There’s nothing like it in our planet’s geological history. Furthermore, when assessing
the damage that could result from such a collision, several aspects must be considered.
The size, density, and mass of the asteroid, as well as the angle and velocity with which
it collides, are all aspects to consider. Scientists should be able to determine better
the size, shape, and composition of Apophis in 2029 and model its interior for the first
time. They will understand how Apophis is put together
on the inside by studying how it shakes, rattles, and rolls, even if by just a small bit, just
like how seismic waves passing through Earth, the Moon, and Mars have been used to figure
out what’s underneath their surfaces. The internal structure of a potentially dangerous
asteroid (PHA) has never been measured before. Apophis might just provide scientists that
opportunity and be the first to do so. Considering Apophis appears to be similar
to roughly 80% of the PHAs found thus far, gathering more information on it may help
scientists learn how we can divert other PHAs if they pose a threat to Earth in the future.
Knowing what PHAs are composed of could be one of the most important space physics knowledge
ever acquired. Also, recently, a team of South Korean scientists
announced that they plan to greet Apophis in space and return a sample to Earth.
Their idea is to approach the asteroid 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.
Apophis’ passage in 2029 is a historical event that should not be missed. On average,
objects the size of Apophis pass this close to Earth just once every thousand years.