Moons of Minor Planets: Revisiting an old visualization

With the news that the Near-Earth Asteroid 1998 QE2 has a small natural satellite of its own percolating through the 'net, I thought it might be a good time to re-visit one of my first animated visualizations. During my PhD, I studied a sample of very widely-separated binary objects in the Kuiper Belt - these are like distant asteroids with moons of their own, but in many cases the moon (the 'secondary') is nearly as large is the main object (the 'primary'). One of the objects I was studying was 2006 CH69, which at the time had a temporary designation of L5c02. After a series of very careful observations, I measured the orbit of the secondary of 2006 CH69 around the primary. It turned out that the system was remarkably eccentric, with e=0.90±0.02 - making it the most eccentric binary minor planet with a well-measured orbit. Given the other properties of the orbit, this meant that when they were at their closest, the two bodies in the system were only separated by about 2,800 kilometers, while at the other extreme of their orbit about each other they were separated by over 52,000 kilometers. This huge swing between the two extremes takes place over half an orbital period, or roughly 2 years.

When I discovered this, I wondered what it would be like to stand on the surface of the primary of 2006 CH69 and look up at the secondary over the course of their mutual orbit. Using a rough calculation of the size of the secondary body, I determined its apparent size as seen from the surface of the primary, and compared it to the apparent size of the full moon (our 'secondary') as seen from the surface of the Earth (our 'primary').

At the time, I was just learning the ropes of how to make effective visualizations, but I put the following animation together:

On the right you see the apparent size of the secondary - here referred to with its earlier designation of L5c02b - as seen from the surface of the system primary. The animation starts with the system at their most widely separated, with the secondary appearing roughly 1/5th the size of the full moon. At their closest half an orbit later, L5c02b grows to appear over 3 times the size of the full moon on the sky!

I took some liberties with this animation - we don't know what the rotation period of L5c02b is, nor do we know if it has any surface markings, or even if it has a round shape! Future, more detailed studies will be needed to refine our understanding of the system.

I later made an animation showing the motion of six of the systems I studied, as seen from the Earth, and the observations we collected of them over the course of a decade.

Mutual Orbits of Ultra-Wide Trans-Neptunian Binaries from Alex Parker on Vimeo.

Click through to read the details of the animation. You can also learn more about these systems in an article I wrote for the Gemini Observatory Newsletter [pdf, page 23].

Spinning Moons

This afternoon I was learning a few of the bells and whistles of the matplotlib Basemap toolkit. As a side product, I ended up with a script to animate a wobbling/spinning planet.

So, here's a couple moons!

2011 HM₁₀₂: A new companion for Neptune

This month my latest paper made it to print in the Astronomical Journal. It's a short piece that describes a serendipitous discovery that my collaborators and I made while searching for a distant Kuiper Belt Object for the New Horizons spacecraft to visit after its 2015 Pluto flyby. Last October, at the annual American Astronomical Society Division of Planetary Sciences meeting, I gave a talk about this neat little object we discovered. Now that the paper is out, I thought it might be interesting and fun to assemble a blog post around the slides I prepared for that talk. So without further ado, I give you:

So, what kind of serendipitous discovery did we make? We found a Neptune Trojan, now called 2011 HM102! And it's not just any Neptune Trojan: it makes a list of superlatives. It's the largest trailing Trojan known in the entire Solar System, it's the most inclined Neptune Trojan known, and (as of right now) it is the closest known object of any kind to the New Horizons spacecraft! Read on to learn about how we found 2011 HM102 and what we have learned about this remarkable little world.

Flying from Kepler-62 e to Kepler-62 f

Today NASA announced the discovery of two potentially-habitable planets orbiting a single star. The star is designated Kepler-62, and these two planets are referred to by their place in the five-planet system - e is planet four and f is planet five (a is reserved for the host star).

These planets are both quite small - 1.4 and 1.6 times the radius of the Earth, respectively. In addition, they're both located at relatively comfortable distances from their host star. Depending on what their atmospheres are like, they could potentially host conditions on their surfaces that are amenable to life.

But two planets in (or near) a single star's habitable zone? That made me wonder - if a civilization arose on one of the two planets, how difficult would it be for them to visit the other planet?

#NaPoWriMo

Day 30: Until next time.


Thirty days written:
Worlds in words with friends in prose
under spring skies.

                                          

Day 29: Challenge


not lost.
simply unseen.
out in the deep star-fields
slow-plying, so come, look again:
find me.

                                          

Day 28: Zeroth Order

scratch a few 

marks on a page

trace the big picture

in broad strokes

with small lines

nevermind the human

ephemera

that fills each dt

no matter how minute

they fall out trivially

in the end

anyway.

How big do stars look from habitable planets around them?

Standing on a habitable alien world, how big would that planet's host star look overhead? After a quick Googling, I didn't come up with any nice summaries. So I snagged Allen's Astrophysical Quantities and did a couple quick calculations.

This figure is the result, showing the apparent sizes of stars as seen from hypothetical habitable planets. around them, all scaled to the size our Sun appears in the Earth's sky. The estimates are fairly crude; I just approximated the distance at which the (bolometric) flux from each star would be equal to that which Earth sees from the Sun. This ignores complicating factors like effective albedo changes due to different peak wavelengths produced by each star, or tidal locking for close-in planets around the lowest-mass stars.

I added the approximate masses of a few notable stars on the left-hand side. Only a couple of these are known to have planets. 

New 500px photography account

I have not created any strictly photography-related posts yet. I plan remedy this soon, and to get the ball rolling I have created a 500px account to host my photography.

At this point, I have only uploaded a sample of my photography from the last few years, but feel free to peruse: http://500px.com/alexhp

A couple examples below the fold.