1994 PC1

Look up this week to see asteroid 1994 PC1 pass by Earth

Look up this week to see asteroid 1994 PC1 pass by Earth

The appearance of asteroid 1994 PC1 this week allows watchers to witness a moving space rock in real-time.

1994 PC1

Look up this week to see asteroid 1994 PC1 pass by Earth.

Asteroids provide a unique opportunity to view things moving in real-time in a slow-moving cosmos. On the evening of Tuesday, January 18th, the 1.1-kilometer asteroid (7482) 1994 PC1 will pass 1.23 million miles (1.98 million kilometers) from Earth, providing us with such an opportunity. This is roughly five times the distance from the Earth to the Moon, and just a shade over the distance to the anti-sunward Earth-Sun Lagrange 2 point, shortly to be the home of the James Webb Space Telescope.

Fortunately, both the Earth and the space telescope will be safe from the asteroid during this approach and will be for generations to come. Astronomer Robert McNaught, watching from the Siding Spring Observatory, found the asteroid on the night of August 9th, 1994. The Apollo asteroid is an Earth-crossers, with an orbital period of 572 days with a perihelion close to our planet at 0.9 Astronomical Units (AU) from the Sun and an aphelion out in the asteroid belt at 1.8 AU. Its 33.5-degree orbital inclination relative to the ecliptic causes it to pass far from the Earth in most years.

Fun fact: while browsing through sky plates, 1994 PC1 may be found in photographs dating back to 1974.

1994 PC1 is a stony-type asteroid of the S-class, and it’s only slightly bigger than another well-known NEO asteroid, 101955 Bennu, which is the subject of NASA’s Osiris-Rex sample return mission, which will return to Earth with its valuable payload late next year.

This week’s flyby is the asteroid’s closest since pre-discovery on January 17, 1933, at 0.00752 AU, and the closest for the next two centuries, while they pass on January 18, 2105, is almost as close, at 0.01556 AU.

The Asteroid Is Being Pursued

The asteroid’s near approach this week allows onlookers to glimpse it for themselves. 1994 PC1 will be at its closest on the night of January 18th at 21:51 Universal Time (UT), crossing the Cetus/Pisces boundary and traveling at a blazing 2 degrees per hour (covering a patch of the sky four times the size of tonight’s Full Moon each hour) or 2 arc minutes per minute. After only a minute or two of looking through the eyepiece, you can see the motion of the speeding asteroid against the starry backdrop. At its brightest, 1994 PC1 should be at magnitude +9, making it visible with a modest telescope or binoculars.

In 2004, I was ecstatic to see the near approach of asteroid 4179 Toutatis. Watching as the space asteroid drifted slowly over the starry backdrop was remarkably similar to this week’s passage.

The good news is that you may start looking for 1994 PC1 tonight: the asteroid is still a respectable +12th magnitude plus on either January 17th or January 19th, the evening before or after the closest approach. In addition, unlike closer approaches, parallax vs observer location will not have a significant impact on the asteroid’s real position in the sky.

To capture it, you’ll need a telescope that can accurately aim at the right ascension and declination coordinates. Enter ‘1994 PC1’ on the NASA/JPL Horizons portal to receive these ephemerides for your time and location. Asteroid 1994 PC1 is seen low to the south at nightfall near the boundary of the southern hemisphere constellations Fornax and Eridanus on Monday, January 17th. For North American watchers, it’s a difficult but not unattainable target.

The asteroid will make its closest approach to Earth this century on Tuesday, January 18th. The Earth would appear as a 22′ half-full disk, a little smaller than a Full Moon if you stood on the surface of the asteroid Tuesday night. Though the exact moment of closest approach favors Africa and European longitudes, nightfall provides a decent view of North America. Another method for following the asteroid is to predict when it will pass close to a bright star, stake out a location, and wait until the opportune moment. Once such a chance comes in the hours around 21:05 UT Tuesday night when 1994 PC1 passes 43’ from the +3.8 magnitude star Alrescha (Alpha Piscium) (Alpha Piscium).

The asteroid will be significantly further north in the constellation Andromeda on Wednesday night, January 19th. Wednesday has the benefit of providing a narrow time for viewing after twilight finishes and before the waning gibbous Moon rises, despite its distance of over 1.7 million miles.

Do you feel hazy? With a live webcast tracking 1994 PC1 commencing at 20:00 UT on the 18th, astronomer Gianluca Masi and the Virtual Telescope Project have you covered.

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Look up this week to see asteroid 1994 PC1 pass by Earth
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