Fast-moving near-Earth object visible tonight

A kilometre-wide asteroid is due to pass less than 2 million km Earth at 21:30 this evening (18 January 2022). The object will be visible using amateur telescopes and will move noticeably through the field of view, offering a rare opportunity to witness such an event.

The asteroid will be close to the star Alpha Piscium (Alrescha) at the time, making it easy to locate without sophisticated equipment. It will appear as a tiny starlike dot of 10th magnitude. Its change in position will be evident over a period of a minute or so. The almost full Moon will be over 90º away in the sky so should not hinder observations greatly.

Telescopes larger than about 75 mm aperture should show the object, although a magnification of 50 or more will be needed to make the object easily visible.

The asteroid is (7482) 1994 PC1, discovered by Robert McNaught, a former section director of the SPA. Rob was working at Siding Spring Observatory in Australia when he discovered the object in 1994 as part of his regular survey patrols. Although it can come close to Earth, it does not pose any danger to us for the foreseeable future.

To find and view the asteroid use the maps below to first identify the constellations of Cetus and Pisces, in the southern part of the sky. Then use the more detailed chart to locate the right part of the sky to find the faint asteroid.

Photography

Those equipped with driven telescopes could attempt to capture the trail of the asteroid. Driven and guided images using a focal length longer than about 500 mm should reveal the asteroid, and a stack of 30-second images will show its trail.

Above: Wide-field view of the southern part of the sky as seen at 17:30 UT from the UK looking south. The track of 1994PC1 is shown at centre with positions shown every 30 minutes. The circle shows a typical binocular or finder field of view of 5º. All maps taken from Chris Marriott’s SkyMap

By 21:30 UT the area will be lower in the sky towards the south-west.

A close view of the track on 18 January. with stars shown to magnitude 10. Geocentric positions.

A closer view of the track around 21:30 when the asteroid passes Alrescha, with stars shown to magnitude 11.5. Tick marks at 5-minute intervals. The circle shows a field of view of 1º. Positions are corrected for observers in the UK.

Positions

Those requiring accurate positions can use the ephemeris below, calculated at 15-minute intervals using the JPL Horizons system. The positions shown are in apparent RA and Dec (that is, for the current epoch rather than 2000.0 as shown on printed star charts) and are for Greenwich, UK.

 Date__(UT)__HR:MN     R.A.__(a-apparent)__DEC
**********************************************
 2022-Jan-18 17:15 Nm  02 20 36.54 -03 42 55.7
 2022-Jan-18 17:30 Nm  02 19 18.90 -03 19 53.5
 2022-Jan-18 17:45 Am  02 18 01.08 -02 56 47.1
 2022-Jan-18 18:00 Am  02 16 43.08 -02 33 36.5
 2022-Jan-18 18:15 Am  02 15 24.93 -02 10 22.2
 2022-Jan-18 18:30  t  02 14 06.64 -01 47 04.4
 2022-Jan-18 18:45  m  02 12 48.23 -01 23 43.5
 2022-Jan-18 19:00  e  02 11 29.69 -01 00 19.6
 2022-Jan-18 19:15  m  02 10 11.07 -00 36 53.1
 2022-Jan-18 19:30  m  02 08 52.35 -00 13 24.2
 2022-Jan-18 19:45  m  02 07 33.57 +00 10 06.6
 2022-Jan-18 20:00  m  02 06 14.74 +00 33 39.2
 2022-Jan-18 20:15  m  02 04 55.86 +00 57 13.1
 2022-Jan-18 20:30  m  02 03 36.95 +01 20 48.2
 2022-Jan-18 20:45  m  02 02 18.04 +01 44 24.1
 2022-Jan-18 21:00  m  02 00 59.12 +02 08 00.5
 2022-Jan-18 21:15  m  01 59 40.21 +02 31 37.1
 2022-Jan-18 21:30  m  01 58 21.33 +02 55 13.6
 2022-Jan-18 21:45  m  01 57 02.48 +03 18 49.7
 2022-Jan-18 22:00  m  01 55 43.69 +03 42 25.2
 2022-Jan-18 22:15  m  01 54 24.94 +04 05 59.7
 2022-Jan-18 22:30  m  01 53 06.27 +04 29 33.0
 2022-Jan-18 22:45  m  01 51 47.67 +04 53 04.8
 2022-Jan-18 23:00  m  01 50 29.16 +05 16 34.8
 2022-Jan-18 23:15  m  01 49 10.75 +05 40 02.8
 2022-Jan-18 23:30  m  01 47 52.43 +06 03 28.5

Key to third column: N = nautical twilight; A = astronomical twilight; t = object transit meridian; e = object at maximum elevation; m = Moon in sky.