## The Atlas of Moons

From National Geographic comes The Atlas of Moons, an interactive reference to all of the major moons in our solar system, from the Earth’s own moon to the Galilean moons of Jupiter to Charon, which forms a binary system with Pluto.

For whatever reason, I wasn’t fully aware that some of Jupiter’s and Saturn’s major moons orbited their planets so quickly — Europa takes 3.6 days to complete an orbit, Io once every 1.8 days, and Mimas speeds around Saturn every 22.6 hours.

## Actually, Mercury Is Our Closest Planetary Neighbor

If you look at the orbits of the planets adjacent to the Earth’s orbit (Venus & Mars), you’ll see that Venus’s orbit is closest to our own. That is, at its closest approach, Venus gets closer to Earth than any other planet. But what about the average distance?

According to this article in Physics Today by Tom Stockman, Gabriel Monroe, and Samuel Cordner, if you run a simulation and do a proper calculation, you’ll find that Mercury, and not Venus or Mars, is Earth’s closest neighbor on average (and spends more time as Earth’s closest neighbor than any other planet):

Although it feels intuitive that the average distance between every point on two concentric ellipses would be the difference in their radii, in reality that difference determines only the average distance of the ellipses’ closest points. Indeed, when Earth and Venus are at their closest approach, their separation is roughly 0.28 AU — no other planet gets nearer to Earth. But just as often, the two planets are at their most distant, when Venus is on the side of the Sun opposite Earth, 1.72 AU away. We can improve the flawed calculation by averaging the distances of closest and farthest approach (resulting in an average distance of 1 AU between Earth and Venus), but finding the true solution requires a bit more effort.

What the calculation also shows is that Mercury is the closest planetary neighbor to every planet, on average. Also, the authors of the paper don’t explicitly mention this, but the Sun (at 1 AU) is closer on average to the Earth than even Mercury (1.04 AU).

## Heliocentrism vs geocentrism

With hindsight, it seems bloody obvious the Sun and not the Earth is the center of the solar system. Occam’s razor and all that. (via @somniumprojec)

## Time lapse video of a scale model of the solar system

A pair of filmmakers, Wylie Overstreet and Alex Gorosh, built a scale model of the solar system in the Nevada desert and made a time lapse of the result. For orbits, they drove their car in circles around “the Sun”. The Earth they used was the size of a marble, which made Neptune’s orbit seven miles across. (via the kid should see this)

## Sunset on Pluto

The backlit photos of Pluto just posted by NASA are breathtaking. Look at this:

Just 15 minutes after its closest approach to Pluto on July 14, 2015, NASA’s New Horizons spacecraft looked back toward the sun and captured this near-sunset view of the rugged, icy mountains and flat ice plains extending to Pluto’s horizon. The smooth expanse of the informally named Sputnik Planum (right) is flanked to the west (left) by rugged mountains up to 11,000 feet (3,500 meters) high, including the informally named Norgay Montes in the foreground and Hillary Montes on the skyline. The backlighting highlights more than a dozen layers of haze in Pluto’s tenuous but distended atmosphere. The image was taken from a distance of 11,000 miles (18,000 kilometers) to Pluto; the scene is 230 miles (380 kilometers) across.

As they say, best viewed large. Some of those features don’t look like mountains at all, but like reptile scales or huge shards of ice pushed up into the sky. Fantastic.

## Flyby video from latest photos shows Pluto in all its glory

Bjorn Jonsson used the photos taken by NASA’s New Horizons spacecraft to make an animation of the probe’s flyby of Pluto.

The time covered is 09:35 to 13:35 (closest approach occurred near 11:50). Pluto’s atmosphere is included and should be fairly realistic from about 10 seconds into the animation and to the end. Earlier it is largely just guesswork that can be improved in the future once all data has been downlinked from the spacecraft. Light from Pluto’s satellite Charon illuminates Pluto’s night side but is exaggerated here, in reality it would be only barely visible or not visible at all.

Fantastic…and Pluto’s moons flying about in the background is the cherry on the top. (via @BadAstronomer)

## This is the best-ever photo of Pluto. Tomorrow’s will be MUCH better.

This morning, the New Horizons probe zinged safely1 past Pluto. Before it did, it transmitted the best photo we’ve seen of Pluto so far…the last one we’ll get before we get the really good stuff. Look at this:

The probe’s “I’m OK!” message will reach Earth around 9pm ET tonight and we’ll start seeing photos from the flyby Wednesday afternoon…there’s a NASA press conference scheduled for 3pm ET on July 15. So exciting!

Update: The photo above is also the best full-disk image of Pluto that we will get…the rest will be close-ups and such. So that’s the official Pluto portrait from now on, folks.

1. Well, hopefully. The probe is due to transmit a “I’m OK!” message back to Earth later today (at around 9pm ET). *fingers crossed*

## What we’ll see from New Horizons’ flyby of Pluto

As the New Horizons probe nears Pluto, I’ve been reading a bit more about how it’s going to work and what sort of photos we’re going to get. Emily Lakdawalla has a comprehensive post about what to expect when you’re expecting a flyby of Pluto. The post contains an image of approximations of the photos New Horizon will take, using Voyager images of Jovian and Saturnian moons as stand-ins. The highest resolution photo of Pluto will be 0.4 km/pixel…it’ll have this approximate level of detail:

Which is pretty amazing and exciting considering that before the mission started this was our best view of Pluto:

NASA’s Eyes app lets you see a simulation of the probe as it approaches Pluto, but if you don’t want to download anything, you can watch this video of the flyby instead:

I had no idea the probe spun around so much as it grabs photos & scans and then beams them back to Earth. And the flyby is so fast! New Horizons is currently moving at 32,500 mph relative to the Sun…it’s travelling just over 9 miles every second. (via @Tim_Meyer_ & @badastronomer)

## This is the best-ever photo of Pluto. Tomorrow’s will be better.

Pluto is so far away that we haven’t even been able to get a good look at it, not even with the crazy-powerful Hubble telescope. But with NASA’s New Horizons mission closing in on our solar system’ ninth planet,1 we are getting a better and better view of Pluto every day.1Here’s the latest, from just a few hours ago:

New Horizons will reach its closest approach to Pluto in just under 6 days, on July 14. The probe will pass within 7,800 miles of the surface…I can’t wait to find out what that day’s photos look like.

Update: You don’t even need to wait until tomorrow for that better image…here’s one that NASA released just a short while ago. Tune in tomorrow for an even better view.

1. Oh yeah, I’m not letting this one go.

2. New Horizons’ imaging capability of Pluto surpassed Hubble’s on May 15, 2015. So every picture since then has been better than what we’ve had previously.

## The Sweden Solar System

Spanning from comets in the south to the termination shock zone in the northern part of the country, The Sweden Solar System is a scale model of the solar system that spans the entire country of Sweden, the largest such model in the world.

The Sun is represented by the Ericsson Globe in Stockholm, the largest hemispherical building in the world. The inner planets can also be found in Stockholm but the outer planets are situated northward in other cities along the Baltic Sea.

## Super Planet Crash

Super Planet Crash is half game, half planetary simulator in which you try to cram as much orbital mass into your solar system without making any of your planets zing off beyond the Kuiper belt. You get bonus points for crowding planets together and locating planets in the star’s habitability zone. Warning: I got lost in this for at least an hour the other day.

## 1850s poster of the planets

I love this poster:

(via @ptak)