The Most Mysterious Star In The Milky Way

The First Photograph of the Dark Side of the Moon from 1959

With the launch of Sputnik in 1957, the Soviet Union kicked off the Space Race and for the first several years (arguable up until the Moon landing in ‘69), they dominated the United States. One of their “firsts” in the early years was taking the first photo of the dark side of the Moon 60 years ago this month.

Astronomer Kevin Hainline wrote a fascinating account of how the Soviet’s Luna 3 spacecraft took the photo and then transmitted it back to Earth.

First off, Luna 3, the first three-axis stabilized spacecraft, had to reach the Moon to take the pictures, and it had to use a little photocell to orient towards the Moon so that now, while stabilized, it could take the pictures. Which it did. On PHOTOGRAPHIC FILM.

And it gets WILDER because these photos were then moved to a little CHEMICAL PLANT to DEVELOP AND DRY THEM. That’s right, Luna 3 had a little 1 Hour Photo inside. Now you’re thinking, well, how do you get those actual photos back to the Earth?

How indeed? The spacecraft faxed the photos to Earth. A few years later, when the Soviets’ Luna 9 took the first photo on the Moon’s surface and went to transmit it back to Earth, a group in the UK was able to read the signal with a fax machine and the resulting image was published the next day on the front page of the Daily Express.

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).

February 19, 2010 – The Space Shuttle Endeavour as seen  from the ISS after undocking. (NASA)

Strange moons

The northern pole of Pluto, in full high-resolution. Yes, that’s ice–methane ice. 

Stunning.

Vote for Place of the Year 2015

Was 2015 the year of Pluto? Or does its exit from the Eurozone make Greece Place of the Year? Now is the time to vote and tell us which place made the most history this year.

In the meantime, reflect on 2014 Place of the Year, Scotland.

Image: Public Domain via Wikimedia Commons.

Space Robot Roll Call

Emily Lakdawalla of the Planetary Society filed a report on humanity’s current roster of spacecraft currently exploring the solar system (and beyond).

Chang'e-4 and Yutu-2 are now past their prime mission and are in their extended mission phases. Their companion SmallSat, Longjiang-2, will crash into the Moon on 31 July to bring its mission to an intentional end. Parker Solar Probe is near aphelion as of 1 July and will reach its third death-defying solar perihelion on 1 September. BepiColombo completed its near-Earth commissioning phase on 5 April and is now settling into its long-cruise phase. Earlier this year, the ESA-JAXA Mercury mission was racing ahead of Earth on an inside track, but its elliptical orbit has now taken it farther from the Sun than Earth, allowing Earth to catch up. It will return to Earth’s neighborhood in April 2020 for a flyby.

I counted roughly 30 different probes and rovers in operation, most of them gathered around the Moon and Mars. Sure, where’s my jetpack and flying car and all that, but the fact that humanity has more than two dozen robots currently exploring the solar system seems pretty futuristic to me.

Wikipedia also has a page listing currently active probes and of course there’s the lovely & informative spaceprob.es as well.

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