Moon is the biggest object traveling
through space around Earth, but it's not the only one actually. There are
several rocky objects floating in our inner solar system that sometimes passes
by Earth. Duncan Forgan, a researcher at the University of St. Andrews, lately
wrote about one such object called 3753 Cruithne on The Conversation, where
he's calling it a "second moon." Image shown below is the best
picture we have of this little, rocky "moon" that's only about 3
miles across. Because of its tiny size, astronomers need powerful telescopes to
see Cruithne. The telescope at Powell Observatory captured the image below,
where it only shows up as a small speck of light. The space-based instrument
NEOWISE captured five pictures of Cruithne that are assembled into a single
image below. NEOWISE searches the sky for near-earth things like asteroid and
comets.
“The reason the object seems
red in this image(below) is because it is radiating light at lower energies than the
white stars in the background,” explains James Bauer, a researcher who studies
comets at NASA's Jet Propulsion Laboratory. Cruithne is a kind of object called
an Aten asteroid, which is a category of asteroids that live inside the inner
solar system between Earth and the sun. It has a strange path through space
where it circles both the sun and the Earth in a bizarre kidney-shaped path.
Aten asteroids are comparatively small, which is also the reason why
astronomers only recently found them. The first Aten asteroid was discovered in
1976 and Cruithne was not discovered till 1986.
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| Image Courtesy of James Bauer |
Cruithne’s Orbit
Cruithne’s orbit is also called
a horseshoe orbit. In order to understand why it’s called a horseshoe orbit,
let’s imagine we’re looking down at our solar system, spinning at the same rate
as the Earth goes round the sun. From our perspective, the Earth appears
stationary. A body on a simple horseshoe orbit around the Earth travels toward
it, then goes round and moves away. Once it’s moved so far away it’s
approaching Earth from the other side, it turns around and moves away again.
Horseshoe orbits are essentially
quite mutual for moons in the solar system. What’s distinctive about Cruithne is how it trembles
and sways along its horseshoe. If you look at Cruithne’s path in the solar
system, it makes a disordered ring around Earth’s orbit, swaying so wide-ranging
that it comes into the region of both Venus and Mars. Cruithne circles the sun
about once a year, but it requires nearly 800 years to complete this confused
ring shape orbit around the Earth. Learn more in the video below:
