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In the continuing adventures of my son learning about the solar system, I’ve learned how long it takes for each planet, among other solar bodies, to revolve around the sun. It turns out it takes some of them a really, really long time.
Naturally, the further the body is from the sun, the longer it takes. As I learn about these long orbits, I often find myself doing some mental math. What year was it when each planet was last in its current position relative to the sun? And what was happening on Earth back then?
Today, I’m finally tired of guessing. I’m looking it all up. Let’s do this.
Mercury — 88-day orbit
The last time speedy Mercury was at its current position around the sun was actually less than three months ago. The date was November 8. The top news stories of the day included President Trump calling CNN reporter Jim Acosta a “rude, terrible person” and Justice Ruth Bader Ginsburg freaking out the country’s liberals after a fall broke her hip and sent her to the hospital.
Venus — 226-day orbit
Sweltering Venus was last located in today’s spot on June 23, the day a restaurant refused to serve Press Secretary Sarah Sanders because she served the President.
Earth — 365.25-day orbit
Mars — Orbit of 1.88 Earth years, or 687 Earth days
The last time Mars was in its current position around the sun, the date was March 18, 2017. The U.S. Department of Homeland Security formally requested prototype proposals for a “Solid Concrete Border Wall” with Mexico, asking for a “physically imposing wall” standing as tall as 30 feet. In the 1.88 Earth years since, progress on the wall has proceeded without incident.
And, sadly, Chuck Berry died.
Jupiter — Orbit of 11.86 Earth years
As we move to the outer planets, now the numbers are getting up there (though you ain’t seen nothin’ yet!). The last time Jupiter was in its current orbital position, we were in March of 2007. We were back in the Bush Administration, and names like Tony Blair and Lewis “Scooter” Libby were in the headlines. I calculated the date to March 27, which might be off a day or two in either direction. On either end of this possible window were Senate and House bills that promised to balance the budget within five years. This went really well.
On a personal note, I was in my first year of teaching, two months away from meeting my wife, and three months away from buying my first condo. As we all know, mid-2007 was the perfect time to buy a home.
Saturn — Orbit of 29.5 Earth years
From Mars to Jupiter we jumped from Trump in the White House to George W. Bush, skipping Obama. (The Republican dream.) Now from Jupiter to Saturn we skip President Clinton and jump to George H.W. Bush. I guess the planets have something against Democratic administrations. Understandable.
Saturn was last in this spot in 1989, the year the Soviet Union officially cracked, new South African President F.W. de Klerg began to roll back apartheid, and Tienanmen Square’s “Tank Man” had it up to here with the Chinese government.
Most importantly, I turned 6, which is right around the time I learned Saturn was a thing.
Uranus — Orbit of 84 Earth years
As Uranus last plodded past its current solar spot, the year was 1935. A certain German Chancellor named Adolf Hitler (the 17th most influential figure in Western history) announced the rearmament of Germany, an act which violated the 1919 Versailles Treaty that had ended World War I and set Europe on a course toward starting World War II.
Neptune — Orbit of 165 Earth years
When our most distant planet was last in its current position relative to the sun, the year was 1854. Here’s how long ago that was:
- It was the year Alexander Hamilton’s wife died.
- It was the year northern liberals founded the Republican Party. (I know. Times have changed.)
- It was the year Florence Nightingale left for the Crimean War.
- And it was the year the Kansas-Nebraska Act permanently staved off an American Civil War.
Pluto — Orbit of 248 Earth years
We might be out of planets, but that doesn’t mean we don’t have some pretty far out solar system bodies to tack on to this list. Thanks to the demoted Pluto‘s huge orbit, the last time it was in its present position was the year was 1771, when the American colonies were still a part of the British Empire.
Also, the Russians and Turks were fighting in the Russo-Turkish War, which is weird because they were also combatants in the aforementioned Crimean War during Neptune’s current position. And we mustn’t forget that when Uranus was last in its current position, World War I was still fresh in every adult’s memory, and in that conflict Russia and Turkey were at war with each other. Now, what we’re supposed to do with this information I have no idea, but I do recommend keeping an eye on planetary charts before your next visit to the Black Sea.
Pluto is now sadly a dwarf planet, but it’s only the second of five, the most distant of which is…
Eris — Orbit of 558 Earth years
At its furthest distance from the sun — a point astronomers call its “aphelion” — Eris is nearly 100 Astronomical Units (the average distance between the Earth and the sun) from the sun, which is about twice as far as Pluto’s aphelion. Pluto is a bit bigger, but Eris is a bit more massive due to a higher density, so if you want Pluto to be a planet, you have to accept Eris, too (and probably lots more soon).
Eris’s enormous orbit takes 558 years to complete, meaning the last time it was in its present position was 1461! Europeans had no knowledge of the Americas, as Christopher Columbus was just a ten-year-old ragazzo. The War of the Roses, pitting two branches of England’s Plantagenet Dynasty, raged into its sixth year. The Roman Empire had, for the second time, fallen just eight years earlier.
Sedna — Orbit of about 11,400 Earth years
At a solid 1,000 kilometers across, Sedna will probably be classified a dwarf planet once we learn more about it. The problem is its current distance — three times further than Neptune — makes it difficult to study. The highly elliptical orbit brings it as close as 76 AU from the sun — inside Eris’s orbit — but at its most distant it’ll reach nearly 1000 AU. That’s five light-days; in other words, it takes light from the sun over five days to reach Sedna’s aphelion.
To find the last time it was in its current position, its orbit of over 11 thousand years takes us well before recorded history. We think the year 9000 BCE is around the time some human groups started farming, which becomes the first step in creating civilization itself. It’s right around then we started keeping sheep, arriving in Estonia, and founding cities like Jericho— all unrelated but pretty cool nonetheless. Speaking of cool, Sedna is unimaginably cold, with an approximate temperature of 12 Kelvin, or -438 degrees Fahrenheit. They could sure use some of that good old fashioned Global Warming.
2015 TG387 (“Goblin”) — Orbit of 32,117 Earth Years
Oh, you thought we were done with Sedna? Don’t you wish. Behold 2015 TG387!
I know, right? That dark blue circle close to the sun is Neptune’s orbit! The vastness of space, even in just our solar system, is intense.
Nicknamed Goblin because it was discovered near Halloween, 2015 TG387 (most small solar system bodies are just known by scientific designations listed in a catalog) gets nearly 2,000 AU away. It’s extraordinary that it retreats nearly 20 billion miles from the sun then slowly solar gravity overcomes its outward momentum and pulls it back in.
The last time it was at its current orbital position, it was about 30,000 BCE. That’s about when we have the earliest evidence of our ancestors domesticating dogs, making figurative art, twisting rope, and painting on Indian cave walls.
But we’re not done yet!
2014 FE72 — Orbit of about 60,900 Earth years
Interestingly, it arrived at its nearest point to the sun — its “perihelion” of about 36 AU, or just outside Neptune — in 1965. But now it’s getting farther and farther away, as it will until we here on Earth arrive at about the year 32,500 CE. Only then will it begins its journey back, though I hope by then the Space Force will have visited 2014 FE72 so it feels a bit less lonely.
The 61,000-year orbit takes us back to about 60,000 BCE, a popular estimation of when humans first left the continent of Africa and started to spread out to other parts of the globe. It’s as if 2014 FE72 was guiding us out as it receded from the inner solar system.
Okay, last one, I promise…
2017 MB7 — Orbit of about 168,000 Earth years
Though its perihelion actually takes it closer than Jupiter, at which point it can pretend to have some friends for a few thousand years, at its furthest point this isolated little guy finds itself over 6,000 AU away. At that point, it’s more than a light-month from Earth, giving it the most distant aphelion of any planetoid.
The last time it was at its current position, we were a minor African species, numbering only in the tens of thousands. With basic tools, we likely weren’t building any structures. We were only just thinking about wearing clothes. Considering such a sight, you can forgive 2017 MB7 for retreating to the far edges of the solar system.
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