Comet Lulin
© Michael JaegerComet Lulin was still only about 11th or 12th magnitude when Michael Jaeger took this image on Sept. 2, 2008. He used an 8-inch f/2.8 ASA Astrograph with a SXV H9 CCD camera for this stacked pair of 4-minute exposures. Click image for wider view.
Comet C/2007 N3 (Lulin), discovered in July 2007, should be the highlight comet of this season. It's predicted to reach about 5th magnitude in late February, so it should be easily seen in binoculars. It may even become detectable with the unaided eye in a dark, moonless sky.



Click below to download a printable finder chart in PDF format for the appropriate date range:
Jan. 1 - Feb. 14
Feb. 13 - Mar. 2
Mar. 1 - Mar. 20
Mar. 14 - May 1
Here's a calendar of the comet's doings in the coming weeks.

January: Pre-dawn, and brightening

The start of 2009 found Comet Lulin glowing at 8th magnitude in Libra, near Lambda (λ) Librae not far from the border of Scorpius. Day by day Lulin is getting higher in the southeast (as seen from mid-northern latitudes) just before start of dawn. It was hidden in the solar glare during November and December. Prior to that, observers visually followed it from as early as May 2008, when it was 14th magnitude, through late October, when it had risen to 8th.

Moving westward across Libra, the comet passes 0.1° south of 47 Librae, and 0.9° north of Lambda Librae, on the morning of January 8th. The comet is at perihelion (closest approach to the Sun) on January 10th, at a solar distance of 1.2 a.u. (181 million km).

Rather than fading after perihelion, Lulin is expected to brighten further as its diminishing distance from us more than compensates for it moving away from the Sun.

February: Peak brightness, peak speed

As Comet Lulin nears Earth its speed across the sky will increase. The beginning of February sees the 6th- or 7th-magnitude comet rising around midnight, and it passes within 1° of the wide binocular double star Alpha Librae on the night of February 5 - 6. Initially moving at about 1° per day, Lulin will be creeping westward at 2° per day by February 11th, when it crosses into Virgo and passes within a quarter degree of Lambda Virginis.

Five days later, on the 16th, comet Lulin - now perhaps 5th or 6th magnitude - will pass 3° north of Spica, and the comet's speed will have increased to 3° per day.

On the night of February 23rd, near its peak brightness, Comet Lulin is passing 2° south-southwest of Saturn.

Lulin's closest approach to Earth, 0.41 a.u. (61 million km), occurs on February 24th, when the comet may reach a peak of magnitude 5. By now it's visible in late evening (after rising around the end of astronomical twilight) and remains in view for the rest of the night.

And it's speeding along at just over 5° per day! That's about 1 arcsecond every 5 seconds of time, enough to show obvious motion during a short telescopic observing session. Similarly, that's 1 arcminute per 5 minutes of time if you're using binoculars.

After that Lulin moves away from both Earth and the Sun, so it fades quickly. The evening of February 27 will see it at 5th or 6th magnitude within 1° of Regulus.

Weirdly, as you may have noticed, this comet is traveling almost exactly along the ecliptic - backward! Could this really be just be a coincidence? The comet is on a nearly parabolic orbit, suggesting that it has never been greatly perturbed by the planets at all. Yet its orbital inclination is 178.4°, meaning that it's orbiting in the opposite direction from the planets just 1.6 - from the ecliptic plane.

Because the comet stays nearly on the ecliptic, its tail (which points away from the Sun) aligns with the ecliptic and with the comet's own direction of motion across the sky. This is shown by the tail's direction on the comet symbols on the finder charts linked to above.

March: Following Lulin out

Comet Lulin crosses from Leo into Cancer at the beginning of March. The night of March 5 sees the 6th-magnitude comet within 2° of both Delta (δ) Cancri and the Beehive Cluster (M44). It will make for a fine sight, particularly in high-powered binoculars. Think photo opportunity.

Another nice conjunction occurs on March 16th when the comet, now around 7th or 8th magnitude (and setting in the early hours of the morning), is 1° from Delta Geminorum.

As Comet Lulin recedes, its passage across our sky will slow. Indeed, from the end of March to the end of May (when Lulin may have faded to 11th magnitude) it will stay within a narrow, 3° strip of sky bounded by Epsilon (ε), Mu (μ), and 36 Geminorum.

Comet Lulin won't return again to the inner solar system for more than a thousand years.

Discovery

Comet C/2007 N3 (Lulin) was discovered by Quanzhi Ye, a student at Sun Yat-sen University in China, as an apparently asteroidal object on images taken by Chi Sheng Lin (National Central University, Taiwan) with a 16-inch telescope at Lulin Observatory in Taiwan on the night of July 11, 2007. A week later, confirming images revealed the telltale presence of a coma.

Lulin was one of 223 comet discoveries on images taken from the ground and in space in 2007, an all-time record.

For a gallery of images and a frequently updated light curve, check the Comet Lulin page on Seiichi Yoshida's Weekly Information about Bright Comets.

Postscript: What Happened to Comet Boethin?

Another comet was expected to be visible in binoculars around this time: Periodic Comet 85P/Boethin. Discovered in 1975 by the late Rev. Leo Boethin (1912 - 98) in the Phillipines, this comet orbits the Sun every 11 years. Or at least it used to.

Comet Boethin was recovered in 1985 and was predicted to brighten to no more than 12th magnitude during the winter of 1985 - 86 (when comet watchers were enjoying the buzz of Halley). However, it managed to surprise, reaching 7th magnitude in January 1986!

Did this outburst disrupt it completely? Comet Boethin was on track to return in 1997, but the poor circumstances of that return meant it could not be sighted. Nevertheless, astronomers decided in 2005 to redirect the Deep Impact spacecraft (now renamed the EPOXI mission) to study this comet, as its orbital path was ideal for the spacecraft.

In 2007 observers around the world and in space started searching for Comet Boethin, but to no avail. Not even a fragment has been found. Perhaps some tiny faint bit will be picked up by patrol telescopes in early 2009. But as of December 1, 2008, there was still no trace of it to 20th magnitude.

Fortunately, the EPOXI mission has now been redirected to the short-period comet 103P/Hartley 2. This one has been seen at four apparitions, so its orbit is secure.

This is not the first time that a periodic comet has been seen on two returns only to be lost. One example in the last century was 34D/Gale, discovered in 1927 from the inner suburbs of Sydney, Australia. It was recovered in 1938 but never seen again. Like Boethin, it too, coincidentally, had a period of 11 years.