25 Minutes With Asteroid 2012 KT42

Two photos taken at different times this morning show how 2012 KT42 picked up speed as it approached Earth. In the left image, a picture was taken every 30 seconds starting at 11:48 p.m. CDT. Pictures for the right image were taken every 10 seconds starting at 1:06 a.m. Thanks and credit to: Rolando Ligustri

I set a snare and captured my asteroid this morning. 2012 KT42, a space rock estimated at 10-30 feet across, blew by Earth earlier today at a distance of only 8,700 miles, well below the altitude of geosynchronous satellites we rely on for communications around the globe.

Although it sounds Hollywood-movie-scary, the chance of a random asteroid hitting a satellite is extremely remote. If one were to be hit, the smack-down would far more likely come from one of the thousands of much smaller and more common meteoroids that occasionally arrive on Earth as meteorites.

I’ve seen near-Earth asteroids before but nothing like 2012 KT42. Sure they all look like moving stars, but this one took my breath away. In 40 years of sky watching, I’ve never witnessed anything beyond Earth move faster. My snare consisted of two parts: a chart with two possible paths and passage times and a telescope. After pointing the scope at where 2012 KT42 was predicted to arrive at 1:29 a.m. I sat and waited.

The glowing numbers on my watch dial indicated 1:23 a.m., then 1:26 and 1:28 a.m. No asteroid yet. But seconds later, there it was – a “star” moving like a flung rock entered the field of view stage right (east) and never slowed down. Interestingly, the asteroid showed up a minute early, possible due to a change in its orbit by Earth’s gravity.

I timed the asteroid’s passage. At 1:30 it moved the span of two full moons (one degree) in one minute. By 1:53 a.m., its speed had doubled to one degree every 30 seconds. At 64x in the scope, 2012 KT42 moved about as fast as the space station does when viewed with the naked eye.

My particular telescope and eyepiece combination gave me a field of view of one degree, so you can imagine how often I had to push the scope to keep track of the asteroid. If I’d taken my eye away from the eyepiece for a minute, I would have lost it for good.

Pictures of the asteroid 2012 KT42 taken at discovery. Credit: Catalina Sky Survey/Mt. Lemmon Observatory

While tracking the speedy missile, I happened to look up toward my garage, and it occurred to me that if it were possible to lasso 2012 KT42 and bring it down to Earth, I could park it there with room to spare.

With that image in mind, I returned to the eyepiece and tried to comprehend seeing something that small move so quickly across the sky. A few miles closer and it would be a shower of meteorites.

One other interesting aspect of watching the flyby was the change in the asteroid’s brightness. It was never constant for long. At 1:30 a.m. it varied between 12th and 13th magnitude in an irregular way; by 1:50 a.m. it was varied from about 11 to 12th. I assume this was because it had an irregular shape and was rotating. For the sake of explanation, let’s assume 2012 KT42 were shaped like a cigar.When brightest, we’d be seeing the cigar broadside with a maximum amount of surface exposed to sunlight; when faintest we’d see only the butt of the cigar. The brightness variations may also have been due to the changing angle of sunlight on 2012 KT42 as it zoomed across the sky.

Nothing escapes the clouds. Not even asteroids. By 1:53 a.m. the morning’s clear sky quickly turned overcast and I finally lost the asteroid as it flitted between ribbons of white mist. It was a wonderful ride, those 25 minutes.

13 Responses

  1. Richard Keen

    When I first saw the article on spaceweather (a GREAT site), I thought it was about previous day’s 2012 KP24 flyby (yep, two flybys in two days). But when I read the article, I changed my bedtime plans. Conditions were great here in Colorado – a clear if chilly night, with the asteroid high in the southern sky. So I quickly set up the 12-inch reflector and tracked the little rock for 42 minutes, from 0612 to 0654 UTC, as it swept across 45 degrees of sky and set into the trees to my west. Along the way it brightened from magnitude 11.5 to 10.5, a whole magnitude brighter than predicted. Aside from some meteorites I’ve held in my hands and other meteors flashing though the upper atmosphere, this is the closest astronomical object I’ve ever seen. According to NASA Horizons, 2012 KT42 was just 19158 km from my house when I last saw it, about the same as a plane flight to Australia. AT 3 to 10 meters, the “dwarf planet” is about the size of my living room, or even one of the bathrooms. It would be fun to stand on a world that size and carefully jump into orbit.

    1. astrobob

      Hi Richard,
      Great to hear from you and happy to know you changed bedtime plans too. Thanks for sharing your observation and fun perspective on this little world.

  2. Stephan

    Hi Bob,
    congratulations for your observation – a lovely description of the thrill one feels when the expected object shows up in the telescope’s field of view; although we weren’t able to follow the asteroid’s pass (broad daylight over here) , I liked to follow your story and Richard’s. Whew only 20.000 kilometers away…that was pretty close.
    Greetings from South West Germany

    1. astrobob

      You would have really enjoyed seeing this one. Fortunately we should both be able to watch the upcoming transit of Venus – you in the morning, me in the evening.

  3. Craig King

    Thanks for that Bob. The things that go on above our heads have always been fascinating and your take on this makes it doubly so. I can imagine being at your side thanks to your writeup.

  4. Richard Keen

    Hi Stephan,
    The thrill was compounded by the fact that I was about to go to bed and did my bedtime check of spaceweather – so I suddenly changed my plans, set up the scope, and saw this marvelous stone racing through the stars. It made up tenfold for the disappointment of not finding 2012 KP24 the night before!
    The sky is overperforming these days – an annular eclipse in Santa Fe last week, and a partial lunar eclipse and Venus transit next week.
    Stephan, do you live near the Steinheim crater, and have you ever looked for shatter cones there? It’s on my “hit list” of places to visit down there in Kepler country. In Santa Fe there’s a newly discovered impact structure, and I spent the morning before the eclipse gathering some nice shatter cones from a road cut. Shatter cones are, of course, the earthly expression of asteroid meets earth.

    1. Stephan

      Hi Richard,
      yes Steinheim crater is pretty close to my place – about 88km (55 miles) to the east of where I live. I visited the place once, it’s a nice “old” crater, these days overgrown and inhabited, but you can still see the structure. Equally nice, but even older and more withered, is the “Nördlinger Ries”, also an ancient impact crater a bit further east.
      Yes and I’m getting prepared for the Venus transit next week. It’ll be around sunrise over here, so let’s keep our fingers crossed that the weather will be nice then. The “eclipse glasses” and the little refractor with the screen have been dusted off and are ready and in place.
      I still remember the lovely sight back in 2004 when Venus entertained us throughout an entire sunny morning.
      Greetings from Stuttgart, Germany

  5. Deborah Seavey

    Hi Bob,
    I am no astronomer but happened to step outside on my roof deck around 2:05 AM in north central New Mexico. The Milky Way was extraordinarily clear especially considering the ongoing Gila Wilderness wildfire in the southern part of the state. I was looking towards the south at what I would call Scorpio’s pincers when I saw the white steak of a shooting star starting up and going to the right (west) . This “star ” however did not fade but brightened – into a large Jupiter-like size yellow orange “fireball”, continuing to streak to the west for a good long until it faded out. The whole vision lasted between 5-8 seconds. Wowza! I have been trying to find out through different reports online what exactly did I see. At first I thought it was a meteor landing on earth somewhere (close!), but the more I learn about Asteroid 2012KT42 the more I think the timing coincides with what I saw as it passes through some of the earth’s outer atmosphere ( varying color ). What do you think Bob?

    1. astrobob

      Hi Deborah,
      Sounds like an exciting sight! It was definitely not 2012 KT42 which was only 10th or 11th magnitude (way below the naked eye limit) and in a different part of the sky at the time. If what you saw had a streak-like tail, it was a very bright meteor. If it was a bright “star” that got brighter and brighter until it faded, it was very possibly an Iridium satellite.

      1. Deborah Seavey

        Ah ha. It sounds like it must have been a meteor because of the slightly rough streaking impression it made, unlike the quiet trackless moving of a satellite. Thanks Bob!

  6. Edie Boudoin

    I have been checking out many of your posts and i can state nice stuff. I will surely bookmark your blog.

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