Asteroid 2007 TU24

Asteroid 2007 TU24 streaked across almost ½° of sky during this 10-minute exposure taken at 1:00 Universal Time on January 29th. North is up in this view obtained with a Tele Vue-NP127is (5-inch f/5) refractor and Apogee Alta U16M CCD camera. Click on the image for a larger view.

S&T: Dennis di Cicco

In a rare bit of meteorological cooperation, metropolitan Boston had clear, albeit cold, skies for last night’s flyby of the asteroid 2007 TU24. And even as an observer experienced in hunting down moving targets, I had to stay on my cold toes to follow this speedy chunk of rock as it crossed nearly 3° of sky per hour.

The image here is a 10-minute exposure centered on 8:00 p.m. EST (1:00 Universal Time on the 29th), during which 2007 TU24 appeared to cross a Moon’s diameter of sky. Estimated to be about 800 feet across, the asteroid was then about 370,000 miles from Earth and closing. Closest approach wasn’t for another 7½ hours, when the distance would narrow to 340,000 miles, about 1.4 times the Moon’s distance.

Visually the asteroid was a little brighter than 12th magnitude and brightening about 0.2 magnitude per hour. Observing with a 7-inch reflector about an hour after this photograph was taken, my S&T colleague Tony Flanders estimated 2007 TU24 to be about magnitude 11½ — fainter than he expected. In fact, Roger Sinnott, another S&T editor, was unable to spot it with a 5-inch scope.

Asteroid 2007 TU24 animation

Asteroid 2007 TU24 zipped along quickly during this 23-minute animation centered at 00:49 Universal Time on January 29, 2008. Each little streak shows the asteroid’s movement during a 60-second exposure with a 4¼-inch f/4 Faworski astrograph and ST10-XE CCD camera. The field here is 1.1° wide.

Don Parker

Did you look for this speedy interloper? If so, did you see it? Let me know via the Comments section below.


Image of Steve Gagnon

Steve Gagnon

January 29, 2008 at 10:39 am

I did not see the asteroid visually, but I did photograph it with a Canon 20D using a 200mm lens at f/4.

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Image of John Scarfone

John Scarfone

January 29, 2008 at 2:14 pm

I saw it visually with a Celestron CPC 800 in Clifton, VA. I had help from the goto combined with JPLs ephemeris calculator. It was moving quite fast at just past 8PM ET. It took some studying with a 40mm eyepiece to find something moving. Then, higher magnification really showed some nice movement.

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Image of Rick Blaisdell

Rick Blaisdell

January 29, 2008 at 2:42 pm

I was able to visually observe it here in Northern NY State on Monday the 28th. Using the scope control program RTGUI I downloaded the co-ordinates to my 8" LX90.As soon as it was dark enough to align the scope I started my hunt.Soon I saw motion from one of the dimmer "Stars" in my FOV.Around 7PM I followed it for a few minutes.This was the first good night of viewing in weeks and my first asteroid.

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Image of Donald Collins

Donald Collins

January 29, 2008 at 6:54 pm

I caught this asteroid on Sunday night, Jan 27 (0130 - 0230 UT on Jan 28) when the weather was clear. Animation is posted at website:

Images obtained with 8-inch SCT and SBIG ST7 camera. Very windy and the telescope was blowing around. We were clouded out on the night of the closest approach.

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Image of stevespeeves


January 29, 2008 at 8:11 pm

I tried very hard, and came so close! I created a pretty cool animation and wrote up my experiences in my astronomy observation blog. The particular link is


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Image of Rick Lentz

Rick Lentz

January 29, 2008 at 9:56 pm

I spent almost three hours looking for it but didn't see it. I've seen Pluto in my 12.5" reflector so an 11.5 magnitude asteroid should have been a piece of cake.

I created a finder chart using Xephem and it showed stars down to 12th magnitude. I could see those stars, and noted several distinctive asterisms along the plotted path. So I was looking in the right place according to the chart. I've concluded that there must have been something wrong with the chart I made, but I don't know what. I'd appreciate if anybody has any ideas or suggestions as to how I might have gone wrong.

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Image of Peter Rice

Peter Rice

January 29, 2008 at 11:22 pm

It's 10pm on Tuesday evening and utilizing a 16" Nightsky with laptop controlled Servocat, the asteroid was easy in Mag 5 skies from Southern California. Estimated magnitude is 11.5. The asteroid's motion as it passes a star is amazing; as obvious as the second hand on a clock.

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Image of Tom Richter

Tom Richter

January 30, 2008 at 7:12 am

I saw the asteroid last night (Tuesday) from my suburban driveway. I pulled down an ephemeris from the NASA-JPL Horizons site, then made a finder chart for the predicted 11 pm location from the STScI Digitized Sky Survey site. I star hopped to the predicted spot and then just looked around for something moving. It only took a few minutes to notice the asteroid moving against the stars. It was dim but not particularly difficult to see in my C5. I would guess the ephemeris estimate of magnitude 10.74 was pretty good.

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Image of Rudolf


January 30, 2008 at 7:47 am

I was lucky to get some CCD imaging of the fly-by which are accessible via my blog at: It was funny to watch the asteroid on 1 sec exposures moving fast through our telescope.

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Image of Stephen Lawrence

Stephen Lawrence

February 1, 2008 at 1:50 pm

I observed the asteroid visually around 9:25 PM EST on Monday, 1/28, using one of Hofstra University's Celestron 11" SC telescopes at 180x. Hofstra is on Long Island, 25 miles from downtown Manhattan in heavily light-polluted skies (the lights from two nearby athetic fields didn't help either). Skies were clear but seeing was poor. Using the NASA JPL-Horizons ephemeris and the telescope's go-to functionality, I was able to find the asteroid on my first pointing attempt and track it visually for roughly 10 minutes before the seeing worsened and it became unable to detect by eye. At 180x the motion was obvious after 15 to 30 seconds relative to other brighter stars. Comparing with Saturn's moons and stars in NGC 752 (after the seeing had worsened), I would crudely estimate the asteroid was around 11th magnitude when I saw it, in line with predictions.
Steve Lawrence
Assoc. Prof. of Astronomy, Hofstra U.

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Image of Frank Klosowski

Frank Klosowski

February 4, 2008 at 11:09 am

I failed to see tu24 also. I focused on the 8pm est location. Just for the record, could you give the coordinate boundaries of the picture taken then. This would let me know how far off I was looking.

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Image of Dennis di Cicco

Dennis di Cicco

February 4, 2008 at 11:54 am


The view on our Web page is heavily cropped from my original frame, which is 3.2 degrees square. The version on the Web is just about 3/4 degree tall. In 2000.0 coordinates, the center of the asteroid's trail is about 1h 43.8m, +38d 20'. Bear in mind, however, that this is the position as seen from my observatory in the western suburbs of Boston. Because of 2007 TU24's close passage to Earth, parallax would significantly displace its position as seen from different locations.

Thanks for your comment.

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Image of Nick Evetts

Nick Evetts

February 5, 2008 at 7:05 am

I caught and photographed TU24 during a Slooh (Mt Teide) session it was awsome

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