This week marked a grand occasion for Pluto enthusiasts. Astronomers and sky watchers enjoyed a very rare opportunity to take a closer look at Pluto through their telescope, as the dwarf planet crossed the plane of the solar system for the first time in nearly a century, reports Popular Mechanics.
Although demoted from its planet status in 2006 — a position it had enjoyed for more than 70 years as the ninth planet of our solar system — Pluto remains a fascinating odd-ball.
Unlike the rest of our planets, which orbit the sun on the same plane, known as the “ecliptic,” Pluto has a 17-degree tilt with respect to the plane of the solar system. This makes the dwarf planet orbit the sun either from above or below the ecliptic, periodically transitioning from one direction to the other.
One such transition has just recently occurred, bringing Pluto in almost perfect alignment with the Earth and the sun.
Known as opposition, the astronomical phenomenon took place on July 12, when Pluto and the sun formed a neat line with Earth in the middle and could be seen on opposite sides of our planet.
This was the first time that Pluto crossed the plane of the solar system in 87 years and the best chance to see the dwarf planet up close for another century and a half.
— Popular Mechanics (@PopMech) July 13, 2018
The moments in which Pluto crosses from one side of the ecliptic to the other are referred to as “nodes” — either an ascending node or a descending node, depending on whether the dwarf planet is moving up or down across the solar system’s plane.
This particular venture through the ecliptic took Pluto to a descending node, as the dwarf planet slid down to align with Earth.
The last time that Pluto crossed from one node to the other, going upward to the ascending node, was in 1931 — a year after the dwarf planet was discovered by astronomer Clyde Tombaugh.
Today, Pluto is crossing the solar system’s plane for the first time since 1931, only a year after its discovery. It won’t do so again for 161 years. (???? Anne Verbiscer) pic.twitter.com/F6EHV9CoVu
— Andrew Rader (@marsrader) July 12, 2018
The July 12 opposition event has enabled the world’s telescopes to see Pluto in greater detail than before.
In fact, professional astronomers had been looking forward to his rare encounter with Pluto for more than a year and prepared both the Hubble Space Telescope and several ground-based observatories for the study of the dwarf planet.
The View From Earth
“When the sun, Earth, and Pluto all line up perfectly, Pluto reflects more light back toward the Earth through a process known as the opposition effect,” explains Popular Mechanics, noting that this phenomenon can reveal more details about the dwarf planet.
Given that we’ve only recently found out exactly what Pluto looks like, thanks to NASA’s pioneering New Horizons mission, this great opportunity to take a closer look at the dwarf planet from Earth was all the more significant.
As humanity’s first spacecraft sent to investigate this distant icy world in the Kuiper belt, New Horizons beamed back the first-ever close-up images of Pluto on July 14, 2015 — almost three years ago to the date.
The View From Pluto
If Pluto was certainly an interesting sight to behold from Earth, our planet would have put on a great show as well for any Plutonians hypothetically watching the opposition event from the other venue, notes EarthSky.
The news outlet presents the crossing of the ecliptic as seen from Pluto, which witnessed Earth and the moon transit the sun. The video below, credited to David Dickinson of the blog AstroGuyz, shows what an Earth transit would look like on Pluto.
Pluto is now bound for another crossing of the ecliptic, this time to move back to the ascending node.
While this last documented journey took Pluto 87 years to complete, the next one, which will carry the dwarf planet upward through the plane of the solar system, is expected to last for 161 years and will be completed in 2179. Only then will Pluto find itself again in a neat alignment with our planet.