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Tue, 18 Apr 2017


An asteroid passes Earth


Trach of asteroid 2014 JO25

The sky looking east from the UK at midnight on 19 April, showing the track of 2014 JO25

An asteroid will whiz close to the Earth on Wednesday night. If you’ve been reading scary internet stories you might sleep uneasily, or if you are of a sterner frame of mind, you might look out in case you spot it dashing across the sky. But in fact it is really comparatively distant, and will require quite a bit of searching for using a decent telescope and a good knowledge of the sky. So if you are after a quickie, don’t bother!

The object is called 2014 JO25, and it is believed to be about 650 metres in diameter. That’s big enough to create a real headache if it hit Earth, but in fact it will miss us by a very generous margin of 1.8 million km, which is about four times the distance of the Moon. And no, there’s no danger of it suddenly veering off course. Guaranteed.

Experienced amateur astronomers who want to take a look will need at least a 100 mm telescope, and ideally larger, as the object will be about 11th magnitude. It will look just like a very faint star, and its movement will only be obvious over a period of a minute or two. So much for whizzing. You will need reasonably dark skies if you are observing visually, and will need to be experienced at finding faint objects. Even observers with Go To telescopes may struggle to find the right field of view.

Those equipped with DSLR or CCD cameras on their telescopes will be better off, as it will be well within range of such equipment, but you will still need to track the stars accurately in order to give an exposure time of several seconds.

The good news is that 2014 JO25 is well placed in the sky, and is at its peak brightness of magnitude 10.7 around midnight on April 19–20, though its closest approach to Earth is some 12 hours earlier. The map at top shows its track through the heavens, passing close to Alkaid at the tail end of Ursa Major during the early evening on the 19th when it is still light in the UK, and then moving into Canes Venatici when it gets dark. Click on the map to get a more detailed version.

For those who know how to do such things, here is a map showing its positions from 9 pm BST on 19 April to 4 am BST on 20 April. Stars are shown to magnitude 11. You'll need to click the map to get a full-sized version. The bright star at centre top is Cor Caroli, Alpha Canum Venaticorum.

Here are positions calculated by JPL. Note that they are apparent positions for the epoch of date – that is, at the time of observation, rather than 2000.0, so they are not suitable for plotting on a star chart.

Date__(UT)__HR:MN     R.A.__(a-apparent)__DEC  APmag
*****************************************************
$$SOE
2017-Apr-19 00:00     22 08 21.68 +60 37 40.1  13.56
2017-Apr-19 01:00     21 55 35.86 +62 26 43.8  13.35
2017-Apr-19 02:00  m  21 40 05.37 +64 17 59.6  13.13
2017-Apr-19 03:00 Am  21 21 03.85 +66 08 58.3  12.91
2017-Apr-19 04:00 Nm  20 57 35.06 +67 55 49.8  12.70
2017-Apr-19 05:00 *m  20 28 38.57 +69 32 56.5  12.49
2017-Apr-19 06:00 *m  19 53 27.74 +70 52 35.9  12.28
2017-Apr-19 07:00 *m  19 12 05.86 +71 45 21.2  12.08
2017-Apr-19 08:00 *m  18 26 09.98 +72 01 44.2  11.89
2017-Apr-19 09:00 *m  17 38 57.94 +71 35 19.9  11.70
2017-Apr-19 10:00 *m  16 54 19.66 +70 25 26.7  11.54
2017-Apr-19 11:00 *   16 14 58.85 +68 37 02.6  11.38
2017-Apr-19 12:00 *   15 41 53.34 +66 18 14.5  11.24
2017-Apr-19 13:00 *   15 14 42.81 +63 37 37.2  11.12
2017-Apr-19 14:00 *   14 52 33.01 +60 42 45.3  11.01
2017-Apr-19 15:00 *   14 34 24.84 +57 39 47.9  10.92
2017-Apr-19 16:00 *   14 19 26.66 +54 33 32.9  10.85
2017-Apr-19 17:00 *   14 06 57.18 +51 27 40.2  10.79
2017-Apr-19 18:00 *   13 56 24.67 +48 24 54.4  10.75
2017-Apr-19 19:00 *   13 47 25.12 +45 27 15.7  10.71
2017-Apr-19 20:00 N   13 39 40.35 +42 36 08.8  10.69
2017-Apr-19 21:00 A   13 32 56.59 +39 52 30.4  10.69
2017-Apr-19 22:00     13 27 03.30 +37 16 54.7  10.69
2017-Apr-19 23:00     13 21 52.31 +34 49 38.7  10.69
2017-Apr-20 00:00     13 17 17.19 +32 30 46.2  10.71
2017-Apr-20 01:00     13 13 12.82 +30 20 10.9  10.73
2017-Apr-20 02:00     13 09 35.02 +28 17 39.2  10.76
2017-Apr-20 03:00 Am  13 06 20.31 +26 22 52.5  10.79
2017-Apr-20 04:00 Nm  13 03 25.74 +24 35 28.7  10.83
2017-Apr-20 05:00 *m  13 00 48.79 +22 55 03.2  10.87
2017-Apr-20 06:00 *m  12 58 27.22 +21 21 10.5  10.91
2017-Apr-20 07:00 *m  12 56 19.06 +19 53 24.7  10.96
2017-Apr-20 08:00 *m  12 54 22.55 +18 31 20.0  11.00
2017-Apr-20 09:00 *m  12 52 36.12 +17 14 31.4  11.05
2017-Apr-20 10:00 *m  12 50 58.36 +16 02 34.7  11.10
2017-Apr-20 11:00 *m  12 49 28.02 +14 55 07.2  11.15
2017-Apr-20 12:00 *   12 48 04.01 +13 51 47.3  11.20
2017-Apr-20 13:00 *   12 46 45.38 +12 52 15.2  11.24
2017-Apr-20 14:00 *   12 45 31.34 +11 56 12.5  11.29
2017-Apr-20 15:00 *   12 44 21.23 +11 03 22.3  11.34
2017-Apr-20 16:00 *   12 43 14.54 +10 13 29.3  11.39
2017-Apr-20 17:00 *   12 42 10.86 +09 26 19.5  11.44
2017-Apr-20 18:00 *   12 41 09.92 +08 41 40.5  11.49
2017-Apr-20 19:00 *   12 40 11.53 +07 59 21.1  11.54
2017-Apr-20 20:00 N   12 39 15.59 +07 19 11.0  11.59
2017-Apr-20 21:00 A   12 38 22.07 +06 41 01.2  11.64
2017-Apr-20 22:00     12 37 30.97 +06 04 43.7  11.69
2017-Apr-20 23:00     12 36 42.33 +05 30 10.9  11.74
2017-Apr-21 00:00     12 35 56.17 +04 57 16.2  11.79


 

Added by: Robin Scagell