The Great Unnamed Masses (of Asteroids)

Ever since I started studying asteroids in grad school, I've been saving a daily copy of the Minor Planet Center's Orbit Database, "MPCORB."  To save hard drive space, I store them in a subversion repository that only saves the changes since the previous version. (That's why you may see references to "revision numbers" alongside dates on my website.) This archive makes it possible to answer questions like:  What did we know about Asteroid X on Date Y?  How many new asteroids in Category Z are discovered every year?

But there was one question I couldn't answer with this archive, because it only reaches back to mid-2006. That question:  How many asteroids have been "numbered" but not "named" for at least the last 10 years?  Perhaps a bit more explanation is in order. When an asteroid is first discovered, it's given a provisional designation based on the date it was first reported, e.g., "2005 RN43". Some become lost at this point, because insufficient observations are made of the object, and our certainty in predicting its position degrades to the point where the object essentially has to be rediscovered all over again. But when the object is properly tracked and its position is well-known for the coming decade or longer, it gets a number, e.g., "(145452) 2005 RN43".  At this point, the object is eligible for naming, but that privilege is reserved for the discoverer for the first 10 years after numbering. 

So back to the question:  How many asteroids have been "numbered" but not "named" for at least the last 10 years?  These would be eligible to be given proper names, but the privilege of the discoverers to do so would have expired. Anyone could suggest names for these objects, although it's up to the Committee on Small Body Nomenclature of the International Astronomical Union to approve or deny them.

As I said, my MPCORB archives don't go back a decade, but I recently stumbled on a resource that could help me answer this question. The Wayback Machine (https://archive.org) contains old archived versions of various webpages, including about 28 old versions of MPCORB from 2001-2007. One of these was from 2004 October 10th, about 10 years and 2 months ago.

So, how many asteroids that were numbered by Oct 2004 still lack a proper name today? How many nameless space-rocks are just waiting for a clever suggestion from us, the hoi-paloi?

Over 73,400!

And I suspect that number is growing, although I haven't done the necessary analysis to prove it. 

Explaining Meteor Shower Radiants [VIDEO UPDATE]

I made a video today to use in my Astro 3105 course, "Physics, Chemistry, and Geology of the Solar System."  There's no narration because I plan to explain it myself in-class, but I'll give a quick explanation in the text below.  The goal is to explain the dates and radiants of a few of the big meteor showers.

We begin by looking at the orbits of Halley's Comet and the Earth.  Although the orbits don't intersect directly due to the comet's orbital inclination, the closest approach between the two paths occurs in early May every year.  Now picture the Earth moving along the green orbit circle counterclockwise, the direction indicated by the arrows.  And visualize a long elliptical ribbon of comet-chunks left behind like breadcrumbs all along the comet's orbit, each chunk moving along the orbit clockwise (again according to the arrows).  This is a nearly head-on collision, so the chunks would appear to be coming at us from the bottom of the image...  And as we change perspective we see that they will appear to come from the constellation Aquarius.  We've just discovered the Eta Aquariids meteor shower, which peaks in early May.

Now we move to the other close-approach point between the two orbits, in late October.  This is again a near-head-on collision, and the meteors would appear to come at us from the upper-right.  Changing perspective, we see that this points to the Orionids shower in late October.

Now we switch to a different comet, 55P/Tempel-Tuttle, whose orbit appears nearly tangent to but slightly inclined to Earth's orbit.  Actually, the inclination is nearly 180 degrees; in other words, the comet and its debris-ribbon again move clockwise around the orbit, whereas the Earth moves counterclockwise.  The meteors should appear to come from directly in front of the Earth - which in mid-November points to radiant of the Leonids shower.

And finally, we switch to the numbered asteroid (3200) Phaethon, which orbits counterclockwise like any respectable asteroid should.  But we are discussing Phaethon because it's not a respectable asteroid - it must be some sort of dead comet or "rock comet" that has spread debris all along its orbit like a comet would.  Now since the Earth is moving mostly "upward" and the debris is moving mostly "leftward," we would expect the meteors to seem to come from the upper-right. And when we change perspective, we see the radiant of the Geminid meteor shower of mid-December.

I've always had a hard time visualizing how debris left behind by a comet could appear to hit the Earth's atmosphere from the same direction at the same time of the year, year after year.  Hopefully this animation has helped you as much as it's helped me.

Map of All Asteroid Observatories (MPC Obs Codes)

In my previous blog post, I made a very rough map of all MPC Observatory Codes (sites who are approved to submit asteroid measurements to the Minor Planet Center).  Not being one to waste effort figuring something out once and forgetting about it, I made a little extra effort.  What I ended up with was this:

Click here to view in Google Maps.

In the process, I remembered a little bit of trigonometry, learned a little bit about geocentric vs. geodetic latitudes, and discovered some cool new capabilities in Google Maps.  Speaking of which, I had to divide the world into 4 regions to upload it into Google without paying a monthly premium:  North America, Western Europe, Eastern Europe, and Everyone Else.  I made very basic latitude/longitude cuts to accomplish this, with only slight attention to common geographic divisions. In particular, I doubt most people would put Italy, Germany, and Turkey in "Eastern Europe," but it was quickest and easiest to do so.  Apparently, the eastern French border is roughly the center of mass of asteroid-observing sites in Europe.

Mystery Maps

Would anyone like to guess what data set I'm mapping in the images below?  Answer below the fold.......

Vizualizing Alternate Orbits for 2014 NZ64

Last month, this article was published on the website of the Express, a tabloid paper in the U.K.  A few days later, Phil Plait caught wind of it and debunked the article on his Bad Astronomy blog at Slate.com.  Essentially, the author of the Express article completely misinterpreted the real data on a newly discovered asteroid, turning this one object into an entire unknown asteroid belt that would wreak repeated havoc on the Earth over the next century. I don't want to repeat Phil's excellent analysis of the situation and how the original author got it so wrong. I just thought I'd bring some simple visualization to bear on the problem, and maybe do a little educating.

The asteroid is 2014 NZ64, and it was discovered on July 3, 2014. It was observed 4 times that night by the Pan-STARRS survey in Hawaii, and then 4 more times on July 5th by my friends at the Astronomical Research Observatory in Illinois. Eight observations over two days, that's it!  That's not very much to go on. In fact, the Minor Planet Center says that by July 9th, its predictions were so uncertain that you wouldn't be guaranteed to see the asteroid within a typical telescope's 10-arcminute field of view.  And by the article's publication on Sept. 5th, the uncertainty radius had increased to 75 degrees. That's half the sky!!  So it's pretty crazy to say we know much about this asteroid at all. 

On the other hand, we do know it was seen on those two nights, and we can do our best to extrapolate its motion from there. But we need to be honest about how good those extrapolations are!  So we won't just fit one orbit to the observations, but many orbits, and we'll use them to map out our uncertainties.  See my previous posts for more discussion about my methods. Let's jump straight to the results!  In the animation and simulation below, the best-fit orbit of the asteroid is shown in bright blues, with the alternate possible orbits shown in faded colors.  The portion of each orbit that is "above" the plane of the solar system is colored cyan, while the part "below" the plane is darker blue.  

Click here to control the simulation yourself!

The animation starts on July 5th, during the very short time period when the asteroid was observed.  See how the possible positions of the asteroid on this date all line up to point directly away from the Earth?  As I love to say, "Astronomers have horrible depth-perception!"  At that point, we knew how to point in the direction of the asteroid in the sky, but we had very little idea of how far away it was.  We had the best-fit position of the asteroid, but as you can see, the distance was quite uncertain.  And as time goes on, Kepler's 3rd Law causes the potential orbits that are on-average closer to the Sun to get ahead, and those on-average farther from the Sun to move more slowly.  So, rather quickly, that initially horrible depth perception turns into a huge uncertainty in the predicted position in the sky.

No further observations of this asteroid have been made after July 5th.  Today it is simply too faint to register on any but the largest and most powerful of telescopes on (or above) the Earth.  If (or when) another successful observation is made, all potential orbits that don't agree with the new observation will be rejected, and the best-fit orbit will be refined.  But at this point, we won't even be able to predict its next close approach of the Earth!  When we see it again, it will be because we got lucky.  We basically have to discover this space rock all over again.

So no, 2014 NZ64 is NOT a swarm of asteroids that will pummel us time and again over the next century - although this simulation may appear that way to the uneducated eye.  These are just the possible predicted positions of a single asteroid as it moves along its orbit into the future.  No wonder the JPL Impact Risk Table shows almost 400 possible collisions between the years 2017-2113!  We really just have no idea where this asteroid is and where it's headed at this point. 

Observing the Oct 8th, 2014 eclipse from Columbus, GA

Eastern Daylight Time is 4 hours behind UT/GMT. So for example, I'm writing this at 00:15 UT = 20:15 EDT (8:15pm). So we'll subtract 4 hours from any UT times to get our EDT.

The Penumbra is pretty weak, so you probably won't notice when the moon enters it (4:15am). It starts to enter the Umbra at 5:15am, and you should see this as the Earth's shadow taking a dark fuzzy bite out of the Full Moon. At 6:25am the whole Moon is in the Umbra, at which point what you had thought was a dark shadow actually turns out looking blood-red, now that the bright uncovered part of the Moon goes away. Greatest eclipse is at 6:56am, but the Moon doesn't cut straight through the center of the Umbra - you'll probably still notice that one side of the Moon is darker red and the opposite side is lighter. Umbral eclipse ends at 7:24am - but sunrise is at 7:39 and moonset is at 7:45, so that's when our show ends.

In other words, the show starts around 5:15am, but 5:30 or 5:45 would be pretty satisfying time to check in on the progress, too.

Image from http://eclipse.gsfc.nasa.gov/LEplot/LEplot2001/LE2014Oct08T.pdf

OrbitMaster Improvements and Sample Scenarios

I've had the opportunity over the past few days to make a few changes to my OrbitMaster applet, so I thought I would outline them here.  The major changes were to the graphical interface, making it look and function better on small screens (like the low-resolution format my MacBook Pro usually defaults to when I plug it into a projector).  Anyway, here's what it looked like on a smallish screen BEFORE the recent tweaks:

As you can see, the time-controls and the orbit-parameter labels were taking up far too much space; the actual orbit-parameter sliders had shrunk to be almost unusable; and the "Fine Control" checkbox disappeared completely.  Here's what I've done to make it better:

Fonts are smaller, but I don't think they're too small when you look at the actual applet.  And everything remains functional at 80% of the width shown, too.  (The "Lock" function disappears, but being able to lock down the orbit-parameter sliders isn't something you need to do frequently.)  How does it look?  Let me know if you have any feedback.

If you're still reading this, then perhaps you'd be interested in some sample orbit I've visualized in the past?

• OrbitMaster - This default page is really the orbit for asteroid Ceres, but without any of the stress of feeling like you're messing with another rock's orbit.  Feel free to play around!
• 2008 TC3 - The object that hit over Sudan with only 24 hours' notice.  Let it orbit a few times at perhaps 10-day time steps and in October 2008, watch OrbitMaster's impact-detection algorithm jump into action!  The applet does also calculate how much speed the object gains as Earth's gravity pulls it in, although it doesn't actually alter the orbital parameters in the process.
• Apophis - Named for the Greek god of darkness and chaos, thanks to the 2.7% probability of Earth impact that had at one time been predicted for April 2029.  Run time forward at time steps of 1 month or less and you'll see that there's a close-approach detection algorithm as well!  Center on the Earth, click the "Fine" checkbox and zoom all the way in, and you'll see Apophis cross the Moon's orbital distance (yellow circle) and that of the Earth's geosynchronous satellites (red circle).
• Killer Asteroid - A fictional asteroid on an Earth-like orbit, constructed to have minimal speed with respect to the Earth for most of its orbit.  But you'll see that when the impact-detection algorithm kicks in around April 2009, the speed increases until impact due to Earth's gravitational pull.  The impact speed is approximately 11.2 km/s, the escape velocity from the Earth's surface.  Which is exactly what you'd expect from an object dropped "from rest" up in space!  This is the slowest that anything from up in space can hit the Earth - without atmospheric deceleration, that is.
• Killer Comet - A fictional comet on a retrograde orbit, constructed to hit Earth with maximal speed..  It doesn't pick up much speed from Earth's gravity (less than 1 km/s), but this is still an escape-velocity scenario!  Because the comet was "dropped from rest" from the outer solar system, when it reaches 1 AU from the Sun it is traveling the same 42 km/s that would be necessary to escape from the Sun's gravity if you started at 1 AU.  Add this to the Earth's 30 km/s orbital speed and you get the 72 km/s impact speed of this comet.  It's the fastest that anything from up in space can hit the Earth - unless it came from outside the solar system!