How To Watch Tonight’s Spooky Flyby Of Asteroid TB145

Asteroid 2015 TB145 will give Earth a close (but safe!) shave overnight when it passes about 1.3 lunar distances from us. The illustration shows the many asteroids of the Main Belt between Mars and Jupiter and the orbit of 2015 TB145. Credit: NASA
Asteroid 2015 TB145 will give Earth a close (but safe!) shave overnight when it passes about 1.3 lunar distances from us. The illustration shows the many asteroids of the Main Belt between Mars and Jupiter and the orbit of 2015 TB145. Credit: NASA

First it’s a Supermoon, then Halloween fireballs hurtling from Taurus and now this — a chunky asteroid that will zip only a little farther than the moon from Earth overnight. Actual time of closest approach by the near-Earth asteroid 2015 TB145 occurs tomorrow morning around noon Central Daylight Time, but if you have a 6-inch or larger telescope, you’ll have a shot at seeing this recent discovery late tonight and before dawn tomorrow.

Map showing the path of near-Earth asteroid 2015 TB145 beginning at 6:00 Universal Time on Oct. 31 hourly through 20:00 UT (1 a.m. – 3 p.m. CDT). Closest approach of 300,000 miles (480,000 km) occurs at 17:05 UT or during afternoon hours for observers in the Americas. The path is only approximate as the asteroid’s orbit continues to be refined. Credit: Chris Marriott’s SkyMap
Map showing the approximate path of near-Earth asteroid 2015 TB145 beginning at 6:00 Universal Time on Oct. 31 hourly through 20:00 UT (1 a.m. – 3 p.m. CDT). Closest approach of 300,000 miles (480,000 km) occurs at 17:00 UT or during late morning and afternoon hours for observers in the Americas. Credit: Chris Marriott’s SkyMap

TB145’s all of 1,300 feet (400 meters) across and will pass us at a distance of 300,000 miles (480,000 km), making it large and close enough to brighten to magnitude +10. Even a small 4.5 inch scope would be able to manage that were it not for the waning gibbous moon nearby for much of the night. The asteroid rises in Orion’s Shield around 10:30 p.m. local time and becomes well-placed for viewing around 11:30-midnight. At that time, an 8-inch scope should show it, but don’t let me scare you off from trying your 4.5-inch on it, especially at the start of dawn.

Map showing TB145’s position for an observer in the north central U.S. at 15-minute intervals starting at 5:00 UT. Subtract 4 hours from UT for EDT, 5 hours for CDT, 6 for MDT and 7 for PDT. Stars are shown to magnitude +12 and north is up in all maps. The asteroid is depicted as a small target. Click to enlarge, then save and make a print out for use at the telescope. Credit: Chris Marriott’s SkyMap software
Map showing TB145’s position for an observer in the north central U.S. at 15-minute intervals starting at 5:00 UT. Subtract 4 hours from UT for EDT, 5 hours for CDT, 6 for MDT and 7 for PDT. Stars are shown to magnitude +12 and north is up in all maps. The asteroid is depicted as a small target. Click to enlarge, then save and make a print out for use at the telescope. Credit: Chris Marriott’s SkyMap software

This speedy, aircraft carrier-sized boulder steadily brightens as it approaches the Earth, rising to around magnitude +10 by Halloween dawn, when Taurus (it’s home at that hour) has tilted over into the western sky. TB145 poses no danger to the planet and will blast out of here in a hurry. Come tomorrow evening, it will have have grown so faint (17th magnitude), only cameras or those with very large telescopes will pick it up.

Map showing the asteroid’s progress across the horns of Taurus from 9-10:45 UT (4 – 5:45 a.m.) October 31st. It passes about 1° northwest of the Crab Nebula around 10:30 UT. Credit: Chris Marriott’s SkyMap
Map showing the asteroid’s progress across the horns of Taurus from 9-10:45 UT (4 – 5:45 a.m.) October 31st. It passes about 1° northwest of the Crab Nebula around 10:30 UT. Credit: Chris Marriott’s SkyMap

That’s why tonight’s the night. I’ve included several maps for observers in the western hemisphere and specifically the United States. They’re hand-plotted based on the latest orbital elements (numbers describing an asteroid’s orbit) and show TB145’s accelerating path across Orion and Taurus starting around midnight tonight (Oct. 30-31) and continuing through the early morning hours.

By this time, TB145 will be around magnitude +10.4 and easier to see than at the start our run. The map covers the time from 11-11:45 UT (6 – 6:45 a.m. CDT). Credit: Chris Marriott’s SkyMap
By this time, TB145 will be around magnitude +10.4 and easier to see than at the start our run. The map covers the time from 11-11:45 UT (6 – 6:45 a.m. CDT). Credit: Chris Marriott’s SkyMap

Because the asteroid approaches Earth so closely, its path against the starry backdrop shifts depending on where you live. Three of the maps show its path for observers in the north central U.S. A fourth map is drawn for the south central U.S, so you can see how much the path shifts. It isn’t much — about 5 arc minutes or 1/6th the apparent size of the full moon — but it’s noticeable. Keep that in mind if you plan to observe this speed demon. Yes, it will be bookin’. Around midnight-1 a.m., TB145 covers about 3° of sky per hour. That doubles by early dawn and expands to around 10° per hour during closest approach. Even at 3° an hour, that’s 1/10th of a “full moon” every minute! Watch closely and you should be able to see it move in real time.

By this time, TB145 will be around magnitude +10.4 and easier to see than at the start our run. The map covers the time from 11-11:45 UT (6 – 6:45 a.m. CDT). Credit: Chris Marriott’s SkyMap
By this time, TB145 will be around magnitude +10.4 and easier to see than at the start our run. The map covers the time from 11-11:45 UT (6 – 6:45 a.m. CDT). Credit: Chris Marriott’s SkyMap

Because of the path shift depending on location, pick a time you want to observe and arrive there 5 minutes in advance. Study and lightly memorize the star field the asteroid will pass through. “Camp” there a while and wait for a “moving star” to make an appearance. That’ll be TB145 doing what asteroids do best – pretending to be stars! I’d suggest after you print out the maps to draw a line connecting the dots, so you have a nice track to sight along. I wasn’t able to do this due to software issues.


Nice video on how astronomers plan to ping the asteroid with radar to create images and study its surface

For more information, especially on how to create your own customized charts for a particular location, please see my earlier article in Universe Today. Hit by bad weather? Don’t have a scope? Check out Gianluca Masi’s live webcast on his Virtual Telescope site starting this evening at 7 p.m. CDT (0 UT) Oct. 30-31. Let us know if you have success (or not) finding this latest near-Earth asteroid. Good luck!

11 Responses

  1. BCstargazer

    All those years waiting in the pumpkin patch for The Great Pumpkin night after night are finally paying off. 🙂

      1. BCstargazer

        Good Grief…. Cloudy last night with some rain and it fell as white stuff at 1300m and above. good thing we have radar to observe it 🙂

  2. Richard Keen

    Got it!
    It was cloudy all evening, but suddenly cleared around 2 am, and it took me an hour to bite the bullet and set up the scope in 76-mph gusts, 30 degrees, and some clear sky snow flakes.
    Thanks for the maps. I was able to zoom right in on TB145 with the 12-inch (shaking in the wind) and track it for 5 minutes. It was a lot easier to see with the electronic I3 eyepiece, so I tracked it for another 5 minutes. Somehow, I couldn’t do my usual multiple hours of tracking, what with the wind and cold and snow.
    Going through a rich star field, there was an occasion to watch TB145 close the gap as it headed straight for – and almost over – a star of similar brightness, and other occasions where it made rapidly rotating “double” stars, morphing triangles and parallelograms, and some quick dashes across open spaces between stars.
    The asteroid’s brightness seemed to change over spaces of a few minutes, but that could have been due to a turbulent atmosphere, shaking telescope, watering eyes, and stray snow flakes. Jupiter and Venus were twinkling as they rose.
    All in all, neat show, worth the cold pinkies.
    Again, thanks for the detailed charts – they helped a lot!

    1. astrobob

      Richard,
      Loved reading your description. Perfect picture of the experience. 76-mph gusts? Wow, that would blow my 15-inch Dob over I’m sure. Also very happy to know the maps were useful. I got up several times overnight hoping for even 10 minutes of clearing, but clouds and rain wouldn’t have it.

      1. Richard Keen

        Bob, 76 mph is nothing for this scope. Its polar axis came from the drive train of a ’65 Mustang, and those axles have gone as high as 135 mph
        http://www.topspeed.com/cars/shelby/1965-shelby-mustang-gt-350-ar859.html
        But at 76 mph it had quite a shimmy! I had to hang on to the tube to keep the scope pointed at the asteroid during some of the bigger gusts, but there were great views during the calms between the gusts. Like the old Mustang, our mountain winds can go zero to 60 in 7 seconds!
        Sorry to hear that you and BC got skunked, but that’s not unexpected in the mid-latitude storm belt as November approaches. And wouldn’t the weather be boring if it were clear all the time? Or like Camelot, where it only rains at night – Ugh!
        Your maps were spot on as seen from Colorado, despite the parallax. Considering the motion of TB145, from SW to NE (or from Colorado to Duluth), it was maybe a minute earlier here but on the same track.
        I wonder if the radar found anything odd on TB145’s surface?

        1. astrobob

          Richard,
          Yes, can’t wait to see the radar images. By the way, were the magnitude estimates for the asteroid close to predicted?

          1. Richard Keen

            At 0955 I gave TB145 a magnitude of 10.8, while the JPL ephemeris prediccted 10.7. Pretty close.
            That estimate was made with the electronic I3 eyepiece as TB145 whipped by an 11.28 magnitude star. The I3 is more red sensistive, like a CCD, and asteroids tend to be a bit brighter in the yellow-red. So the actual Visual magnitude could be slightly dimmer.

          2. Richard Keen

            BTW, when I stepped outside to set up the scope at 0310 Mountain Time the first thing I saw was a long, slow 1st magnitude Taurid, dropping to the western horizon from below the Pleiades. The Taurids come from Comet Encke, whose orbit is not all that different from TB145’s – similar period, eccentricity, etc., except the asteroid’s inclination is 18 degrees greater. Here’s links to the orbit diagrams for TB145, Encke’s, and the Taurids:
            http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2015 TB145&orb=1
            http://ssd.jpl.nasa.gov/sbdb.cgi?ID=c00002_0;old=0;orb=1;cov=0;log=0;cad=0#orb
            http://www.spaceweather.com/images2015/31oct15/orbits.gif?PHPSESSID=siksh0p0s6oiot52l3f1ckg3c5

        2. BCstargazer

          Great work Richard.
          Experienced the sudden short clearings and the high winds here as well
          Bob might have been skunked but I prefer to refer to this kind of experience(s) as been “Pepe “Le Pewed”
          😀

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