Tuesday, June 4, 2013

"Movie Posters" for NASA planetary missions

In the next few years, several NASA missions to the outer solar system will be arriving at their destinations: New Horizons flies by Pluto in 2015, and Juno enters orbit around Jupiter in 2016. 

These two spacecraft also have fairly distinctive silhouettes, and I thought I could highlight them and their destinations with some moody backlighting. So I made these two posters:

New Horizons in the Pluto system

Juno entering the Jupiter system

Friday, May 31, 2013

Our Evolving View of the Cosmic Microwave Background - Revolving!

After putting together my Spinning Moons post, I didn't want my cosmologist friends to feel left out - so I constructed some spinning maps of the Cosmic Microwave Background (CMB) from different observational eras.

Thursday, May 30, 2013

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.

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].

Wednesday, May 22, 2013

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!

Friday, April 26, 2013

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.

Thursday, April 18, 2013

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?

Tuesday, April 2, 2013


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
that fills each dt
no matter how minute

they fall out trivially
in the end

Monday, March 18, 2013

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. 

Friday, March 1, 2013

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.

Friday, February 22, 2013

Observatory Interior: Interactive Panorama!

Have you ever wondered what the inside of a world-class observatory looks like?

On a run at the Magellan Baade 6.5-meter observatory in Chile last year, I took a full 4π steradian spherical panorama of the dome interior using Photosynth on my iPhone. The result is the interactive, scrollable panorama below:

Below the telescope you can see two of my colleagues coming down from one of the instrument platforms; they are both well over 6' tall and make good scale references. This is a huge machine.

I will post later about some of the data we collected on that run. Spoiler: Neptune has a new friend!

Alex H. Parker

Planetary Popularity

I have wanted to do something with the Google n-gram data for a while, and I've finally caved.

For those who haven't seen it yet, the Google n-gram browser allows you to see and compare the historic popularity of various phrases in books throughout history.

The default browser is fun and fast to play with, but I decided to take a crack at some of the raw data.

How about comparing the popularity of various planets (including the now-dwarf planet Pluto) in literature across the last few hundred years?

I give you "Planetary Popularity in Recent History:"

Click to enlarge!
Details and a little interpretation below the fold.

Accidental Geoengineering

There are a lot of big numbers associated with climate change. The sheer scale of human activity is often lost in the numbers needed to describe it; millions, billions, and trillions.

Perhaps we need to contextualize our carbon dioxide production by comparing it to something else with similar bogglingly-big numbers: space.

To place human greenhouse-gase production into an astronomical context, I assembled a few choice comparisons into a convenient infographic. See it below the fold.

Punchline for the impatient: we produce a lot of CO2. One Halley's comet every decade, and one Martian atmosphere in 200-700 years (depending on assumptions about growth).

A Golden Age for Exoplanet Discoveries

After making a similar plot in my PhD thesis for the discoveries of minor planets throughout history, I thought it would be interesting to compare the rate of discovery of exoplanets to that of asteroids.

We are clearly in a golden age of exoplanet discoveries. In the past 23 years we have discovered over 800 confirmed planets in stellar systems outside out own; it took 114 years from the discovery of Ceres to find as many asteroids.

Alex H. Parker

A Hubble Starry Night

Around the time of the Hubble Space Telescope's 22nd birthday, I created an homage to its legacy by assembling the Top 100 most popular Hubble images into a photomosaic of Van Gogh's famous "Starry Night" image.

Hubble Starry Night
Hubble Starry Night mosaic. Click to enlarge, or view a full-size 4400x3600 version.
Somewhat fittingly, I made this while waiting for clouds to part and reveal the stars during a night of remote observing.

I got a lot of requests to make the image available as a poster, so you can now order a print of it from Zazzle.

Alex H. Parker

New Horizons Kuiper-Belt Fly Through

Fly with the New Horizons spacecraft as it cruises by dozens of newly-discovered Kuiper Belt Objects (KBOs) near its trajectory. These objects were found by our survey team (gray points) as well as by members of the public through Ice Hunters (purple points) during a search - still under way - to find a KBO for New Horizons to approach close enough to take detailed images and measurements of its surface. See below the break for details.

New Horizons Mission: Kuiper Belt Fly-Through from Alex Parker on Vimeo.

Worlds: The Kepler Planet Candidates

Worlds: The Kepler Planet Candidates from Alex Parker on Vimeo.

This animation shows the 2299 high-quality (multiple transits), non-circumbinary transiting planet candidates found by NASA's Kepler mission so far. These candidates were detected around 1770 unique stars, but are animated in orbit around a single star. They are drawn to scale with accurate radii (in r / r* ), orbital periods, and orbital distances (in d / r*). They range in size from 1/3 to 84 times the radius of Earth. Colors represent an estimate of equilibrium temperature, ranging from 4,586 C at the hottest to -110 C at the coldest - red indicates warmest, and blue / indigo indicates coldest candidates.

Watching in full screen + HD is recommended, so you can see even the smallest planets! Animation details below the break.

Kepler 11: A Six-Planet Sonata

Sonification of the transits of the remarkable Kepler 11 planetary system.

Located roughly 2000 light-years from Earth, the star Kepler 11 has a compact system of six planets, detected by the Kepler space observatory through their transits of their host star.

Kepler 11: A Six-Planet Sonata from Alex Parker on Vimeo.

Here, I've taken each transit seen by the observatory and assigned a pitch and volume to it. The pitch (note) is determined by the planet's distance from its star (closer=higher), and they are drawn from a minor 11 chord. The volume is determined by the size of the planet (larger=louder).

The near-4:5 mean-motion resonance of the innermost two planets is audible as the notes "beat" against each other.

A triple-transit (three planets crossing the face of the star at once) in August 2010 is also audible. This event is what is illustrated in the artist's impression of the system used in the cover photo.

Creative Commons license - 2012 - Alex Harrison Parker, Harvard-Smithsonian Center for Astrophysics.

[ Migrated from original post. ]

Wednesday, February 13, 2013

The Supernova Sonata

Supernova Sonata from Alex Parker on Vimeo.

From April, 2003 until August, 2006, the Canada-France-Hawaii Telescope watched four parts of the sky as often as possible. Armed with the largest digital camera in the known universe, CFHT monitored these four fields for a special type of supernova (called Type Ia supernovae) which are created by the thermonuclear detonation of one or more white-dwarf stars. These explosions are extremely energetic, and can be seen across vast distances in space.

These four fields covered roughly 16 times the area of the full Moon on the sky, or roughly 1/10,000 of the entire sky. Even though such a small fraction of the sky was monitored, 241 Type Ia supernovae were seen during the period of observation.

This video is a compilation of the 241 Type Ia supernovae seen in these fields during the CFHT Legacy Survey. The four Deep Fields are shown in color, and the positions of all the supernova are illustrated as time progresses. The animation is rendered at 15 frames per second, and each frame corresponds to just under a single day (one second in the animation corresponds to roughly two weeks of real time).

Each supernova is assigned a note to be played; details are below the break.