SKYWATCH: COMET LULIN APPROACHES

I have not been putting up many astronomy posts lately, but, I would be remiss if I did not inform everyone about Comet Lulin (Comet C/2007 N3 (Lulin). It is the highlight comet of the year, and here is a great article to get everyone informed of its approach. It will be 1,000 years before Comet Lulin returns to the inner solar system, so view it while you can.

Enjoy!

**********************************************************************************************

 

CATCH WINTER’S COMET LULIN
 
by Greg Bryant and Alan MacRobert

 

Comet Lulin on Sept. 2, 2008
Comet 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.
Michael Jaeger
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:



 

 

 

 

Below is a calendar of the comet’s doings in the coming weeks (and here’s an ephemeris). But don’t assume that the brightnesses are trustworthy. The comet’s brightness behavior may be unpredictable, because it’s on a nearly parabolic orbit that suggests this is its first visit to the inner solar system. You never know what a pristine comet might do.

 

 

January: Pre-dawn, and Brightening

 

The start of 2009 found Comet Lulin glowing at 7th 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 most of December. Prior to that, observers had 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.

 

 

Weird Orbital Geometry

 

Strangely, as you may have noticed on the charts, this comet is traveling almost exactly along the ecliptic — backward! Could this really be just be a coincidence? The comet’s nearly parabolic orbit indicates that it has never really interacted with 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. (Manipulable 3-D orbit diagram).

 

 

Tails and Antitails

 

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 indicated by the direction the tail is pointed on the comet symbols on the finder charts linked to above.

 

Moreover, because Earth remains in the comet’s own orbital plane, we’re likely to see the comet with a very thin tail and an antitail, a spike pointing in almost the opposite direction from the main tail, for months on end. Why? In three dimensions a comet’s dust tail is often wide but it’s always thin, confined to the comet’s orbital plane. When we are in or near this plane, we can sometimes see parts of the wide, thin dust tail on opposite sides of the comet’s head. We pass through most comets’ orbital planes briefly. But this time, the situation will last and last.

 

And indeed, as of January 7th Lulin did have an antitail, as shown in this image taken by Karzaman Ahmad in Malaysia with a 20-inch scope (image courtesy Spaceweather.com.) Here’s another image, from Ernesto Guido, Giovanni Sostero and Paul Camilleri, taken January 8th. Here’s a photo gallery of more.

 

A comet’s blue-green gas tail, on the other hand, always points nearly in a straight line away from the Sun in space. Cometary gas is blown directly away from the Sun at high speed by the solar wind.

 

 

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.

 

 

Cooperative Discovery

 

Comet C/2007 N3 (Lulin) was discovered by Quanzhi Ye, a student (age 19) at Sun Yat-sen University in mainland 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. In China and Taiwan, the comet has been hailed as the “Comet of Cooperation.”

 

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.

 

 

SOURCE:  http://www.skyandtelescope.com/observing/highlights/35992534.html

RELATED LINKS:  http://www.spaceweather.com/

4 Comments

Filed under Uncategorized

4 responses to “SKYWATCH: COMET LULIN APPROACHES

  1. Al Southern

    I live in zip code 91752, Southern california. Where would I look to see lulin the comet?

    I love comet and look forward to seeing this green comet.

    • Ann

      @Al Southern.

      Sorry for getting back late with you.

      Hopefully here is some help to allow you to find Comet Lulin to observe it.

      On Tuesday morning, Feb. 24th, Saturn and Comet Lulin will converge in the constellation Leo only 2o (2 degrees) apart. (Leo lies between dim Cancer to the west and Virgo to the east.) At the same time, Comet Lulin will be making its closest approach to Earth (38 million miles), while four of Saturn’s moons transit the disk of the ringed planet. Oh, and the Moon will be New, providing dark skies for anyone who wishes to see the show. All you need now … is a telescope.

      So, facing South, West will be on your right, and East will be on your left. In the center area (looking South) will be the area you will scan to view Comet Lulin.

      ONE O’CLOCK IN THE MORNING: Set your alarm for 1 am. That’s the best time to see Comet Lulin riding high in the southern sky pleasingly close to golden Saturn: sky map:

      http://www.spaceweather.com/images2009/22feb09/skymap_north_lulin.gif?PHPSESSID=di3q8m9vedknhb71gichb9ib42

      To the unaided eye, Lulin looks like a faint patch of gas. Point your telescope at that patch and you will see a lovely green comet.

      On Feb. 24th, Comet Lulin will swing past Earth only 38 million miles away. Got clouds? No problem. The Coca-Cola Space Science Center (http://www.ccssc.org/ ) in Columbus, Georgia, plans to webcast the encounter. “We’re going to transmit the view through our observatory’s 16-inch Schmidt-Cassegrain telescope,” says astronomy professor Rosa Williams of Columbus State University. “The webcast begins at 11:30 EST on Monday, Feb. 23rd and will continue until 5 a.m. EST on Tuesday the 24th.” Tune in!

      http://www.ccssc.org/observatory/darksky_cameras/darksky_cam.html

      😉

      For more info on Comet Lulin, and for finder charts to track it, click here:

      http://www.astrodrayer.com/lulin

      UPDATE–SPEEDING COMET: “Last night (Feb.21) Comet Lulin was visible to the naked eye with identical brightness as star b Vigo HP58510 with a magnitude of 5.35,” reports Eddie Irizarry of the Sociedad de Astronomía del Caribe in Puerto Rico. “But what caught our attention most was Lulin’s noticeable speed. Using a telescope, take a good look at the stars that surround Comet Lulin; then look again just 10 minutes later and you will see how Lulin’s position has changed. It is amazing how fast this comet is moving!”

      The experts are right; Lulin is a fast moving comet.

      Try to catch it.

      It will be 1,000 years before it returns to our part of the solar system.

      Good luck!

  2. Chicken Coop

    great post(why i keep getting an error when i try to subscribe to your feed)?thanks

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s