Sometime over the next week or so, you may want to pick a clear evening to head outside and look at the sky. If you do, you'll have a chance to see something pretty cool: a comet, streaking past Earth as it orbits the sun.
The comet, called C/2014 Q2 (Lovejoy), appears as a beautiful, fuzzy green ball through binoculars, and in some areas, it's even visible to the naked eye.
It made its closest approach to Earth on January 7, passing within 44 million miles of us. But because it'll continue nearing the sun for the next few weeks — and heating up, creating a tail of vaporized dust and ice — it's brightest and easiest to see right now.
Comets that are visible without telescopes at all only come around about once per year, and most of them are much fainter than this one. So sometime in the next week, go outside and take a look.
How to see the comet
Regardless of where you live, by 8 pm local time, the comet will be high enough above the horizon to be visible — and should stay that way for most of the night.
If you live in a city, you're best off using binoculars or a telescope to get a good view of the comet, and these instruments will give you the most dramatic views anywhere. But in some places, it can be spotted by the naked eye.
The chart above shows where to look for the comet as it moves North and away from the horizon over the course of January. Right now, an easy way of spotting it is to use the three stars that make up Orion's belt as an pointer.
Right now, the comet has an apparent magnitude of 3.8 — far brighter than originally projected — and astronomers predict it'll remain that bright for the entire week. If you look at it through binoculars, it'll look like a hazy blob, and might appear green — the result of its carbon molecules getting hit by ultraviolet sunlight. If you have an especially good view, you may see a faint tail streaking behind the comet, due to vaporization of dust and ice as it nears the sun and heats up.
In late January, as the moon returns, the comet's will begin to dim a bit from our vantage point, and after January 30 — when it passes closest to the sun (within about 120 million miles) — it'll dim further.
What we know about Comet C/2014 Q2 (Lovejoy)
The comet was first spotted in August by Terry Lovejoy, an Australian amateur astronomer who'd already discovered four other comets in his spare time. It wasn't originally predicted to be easily visible, but it's become far brighter than projected.
The comet is two to three miles wide — roughly the size of the comet that Philae landed on in November. The visible stream of vaporized gas emitted from it, though, is estimated to be about 400,000 miles wide
Astronomers have calculated that it's a long-period comet, which means that it has a highly elliptical orbit that takes it far from out to the outer reaches of the solar system, then back in towards the sun, over long periods of time.
In this case, its orbit is calculated to take about 11,500 years, though slight changes to the orbit (due to the gravity of the planets it's passing by on this go-round) will shorten that to 8,000 years for the next orbit. In either case, if you don't see the comet in January, you're not going to have another chance in your lifetime.