After a long wait, a comet called NEAT finally comes far enough north this week to become accessible to sky watchers in the Northern Hemisphere.
Ever since its discovery back in August 2001, this comet has been visible only to those south of the equator. But now as the comet sweeps past Earth en route to its closest approach to the sun, it will appear to race rapidly northward and should be visible to most northern sky watchers starting Wednesday evening.
About an hour after sunset, look low in the southwest for blue-white Sirius, the Dog Star, the brightest star in the night sky. Comet NEAT should be hovering about 10 degrees to the left of Sirius (your clinched fist, held at arm’s length, is roughly equal to 10 degrees). On Thursday evening, the comet will be passing closest to Earth, only 29.8 million miles away.
The comet will move higher in the sky each night. It will likely be shining at its very brightest on these initial evenings, and for perhaps for a few more nights thereafter.
Originally, hopes were that Comet NEAT would become as bright as magnitude 0.9. That would have placed it in the same brightness ranking as the orange star Aldebaran in Taurus, or the reddish star Antares in Scorpius.
Instead, Comet NEAT will probably only get about one-sixth as bright, reaching a plateau in brightness of around third magnitude. On the astronomers' scale, larger numbers represent dimmer objects. The dimmest star that can be seen with the unaided eye, under perfectly dark conditions, is about magnitude 6.5.
If NEAT reaches magnitude 3, that would place it in the category as Megrez, the star that appears to join the handle and the bowl of the familiar Big Dipper.
Observers should look for a fuzzy starlike object of medium brightness with a short, slightly curving tail protruding out from it to the left (eastward). Binoculars will enhance the view.
The fact that Comet NEAT is likely to end up fainter than originally hoped for is not a surprise. As we have noted since last May, NEAT is apparently making its very first approach to the vicinity of the sun, having spent all its life in the deep freeze of the outer solar system. History has shown that most "first-timers" usually fall short of brightness expectations.
Initially, on Wednesday evening, the comet’s low altitude above the horizon, the unpredictable amount of horizon haze, the comet’s uncertain brightness and tail visibility, as well as the skill of the observer, will complicate the picture as to whether a sighting can be made.
Nevertheless, anyone should be able to see Comet NEAT — weather permitting — if they follow some important observing tips:
- Locate a good observing site in advance and get there early, preferably no later than local sunset.
- You will need a clear and open view of the west-southwest horizon. There should be no artificial lights nearby and no cities or towns to illuminate that part of the sky. NEAT will be impressive only from a dark country location where the sky is really black. A rooftop, seashore or hillside facing west-southwest is ideal.
- It is hard to predict just how bright the comet will appear near the horizon. If your sky is really dark, the comet should be visible to the naked eye. In addition, horizon haze (or "schmutz") can absorb much more light. Binoculars ought to show it well. In fact, the tail might be the most readily visible feature, appearing as a narrow, ghostly ray of light protruding out from the fuzzy head of the comet.
The good news is, that in the evenings that follow, Comet NEAT will be getting progressively higher up in the southwest sky and correspondingly easier to see.
The comet will be passing by to the east of the bright yellowish-white star Procyon in Canis Major on Sunday and Monday evening. On May 13, a line drawn from Castor to Pollux (in Gemini) and extended out three times the distance between these two stars will bring you to Comet NEAT.
On May 15, the comet will reach its closest point to the sun, just over 89 million miles away. It will also be positioned just a few degrees from the prominent open star cluster, M44, popularly known as the Beehive. It should then fade rapidly from view as it moves away from both sun and Earth, moving into Ursa Major by month’s end.