2015-10-22

How to find 'Halloween Asteroid' 2015 TB145 using Stellarium

A 'halloween asteroid' is approaching. First off, regardless what you might hear on 'the internet', there is no danger of a collision with 2015 TB145. The 400-something-meter space rock will pass Earth on October 31, 17:12 UT, at a safe distance of 494,000 kilometers, which is 1,3 times the distance to the moon. Close enough however to be seen with small backyard telescopes - if you know where to look.

2015 TB145 will be indistinguishable from faint stars, but it is moving fast. Between October 30 and 31, it will change position with respect to the fixed stars within hours or even minutes. You'll need good finding charts to identify it, though. Here's a short tutorial how to find this (or any other) asteroid with the free program Stellarium (available also as smartphone app).

At my location, 2015 TB145 will be visible in Orion's shield on the morning of October 31.
2015 TB145 was discovered just recently, so its orbital data probably won't be stored in your local Stellarium database yet. This data is provided by the Minor Planet Center. To load it, in Stellarium press F2 to open the "configuration" window and select the "Plugins" tab. Select "Solar System Editor" and hit  "Configure" at the bottom of the tab. Choose "Solar System" and click "Import orbital elements in MPC format". 

Mark "Asteroids" and select "Download a list of objects from the internet". As "Source from the list" select "MPCORB: near-Earth asteroids (NEAs)" and hit "Get orbital elements". After the download is finished, search for "2015 TB145", mark the asteroid and hit "Add objects". (You may, of course, add more objects.)

Almost done. Close the Solar system editor and go back to the main screen. To find 2015 TB145, just hit F3 and enter "2015 TB145". The asteroid will be marked with a red, pulsating cross,

By choosing date and time, you can now easily find out if, when and where 2015 TB145 can be seen from your specified loaction. Zoom in to see nearby stars.

Stellarium also supplies an estimation of the asteroid's apparent magnitude at any moment. Note that due to geometry reasons, 2015 TB145 will be brightest around 12:30 UT on October 31, when Europe is in daylight.

Clear Skies!

Update: It has been pointed out to me that due to deflection by Earth's gravitation, the orbital elements of the asteroid will change on October 30/31. There may be deviations up to several arcminutes. So positions given by Stellarium will not be accurate to the arcsecond, but nevertheless should suffice to point a telescope/camera to the right direction.


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