Starship Asterisk*

What star/comet?? is at the end of the tail in the upper picture and then has moved in the lower picture.
I used as a reference point the string of 4 background stars, starting at about 12 o'clock above this brighter and larger star than the background and going to the left and down at about a 20 deg.
I have not had a chance to spot our new Comet as yet, but will do so as soon as possible and keep tracking it.
I use a 12 inch Orion Dobs. Intelliscope.
Those are 2 really good pictures

http://apod.nasa.gov/apod/ap090207.html

Fred Pellmann wrote:What star/comet?? is at the end of the tail in the upper picture and then has moved in the lower picture.
I used as a reference point the string of 4 background stars, starting at about 12 o'clock above this brighter and larger star than the background and going to the left and down at about a 20 deg.

Are you sure you're seeing common stars? I don't really see the reference stars you refer to (I think I know the ones in the top, but I don't see them in the bottom). The image caption says that the field is somewhat larger than 2 degrees, but the comet moved close to 3 degrees in the time between the exposures, so I wouldn't expect any common stars.

I also don't believe that there are any common stars in either image. It i probably just chance that there is another bright star in/near/above the tail in the later image.

See also Mike Broussard's pic Comet Lulin, C/2007 N3 on Feb 6, 2009

In the bottom of the two photos, has the comet split into two nucleus?

aristarchusinexile wrote:In the bottom of the two photos, has the comet split into two nucleus?

I don't think so. When you image a comet, you have two choices: track on the comet (which isn't always possible), or track on the stars. These images were obviously made with the latter technique, so the comet itself is slightly motion blurred- more so in the bottom image, which I'm guessing had a longer total exposure time.

Looking at the two pictures, it looks as though the comet has broken into two parts in the lower picture. Does this look to be true?

TEMOHLER wrote:Looking at the two pictures, it looks as though the comet has broken into two parts in the lower picture. Does this look to be true?

As previously noted, this is probably just an illusion caused by motion blur. Images taken a few days later don't show any separation in the nucleus.

Chris Peterson wrote:

TEMOHLER wrote:Looking at the two pictures, it looks as though the comet has broken into two parts in the lower picture. Does this look to be true?

As previously noted, this is probably just an illusion caused by motion blur. Images taken a few days later don't show any separation in the nucleus.

I didn't see that other post, my apologies. However, it will be interesting if there are two pieces to that comet. I'm sure it will be watched very closely.

aristarchusinexile wrote:

Chris Peterson wrote:

TEMOHLER wrote:Looking at the two pictures, it looks as though the comet has broken into two parts in the lower picture. Does this look to be true?

As previously noted, this is probably just an illusion caused by motion blur. Images taken a few days later don't show any separation in the nucleus.

I didn't see that other post, my apologies. However, it will be interesting if there are two pieces to that comet. I'm sure it will be watched very closely.

It is hard to image that Lulin could have broken in half without
some sort of dramatic brightening a la Comet Holmes.

neufer wrote:It is hard to image that Lulin could have broken in half without
some sort of dramatic brightening a la Comet Holmes.

So you'd think, but the fact is that comets do sometimes fragment with little or no change in brightness. Probably something to do with just how many volatiles they have left to vaporize.

And Holmes brightened without any obvious nuclear fragmentation.

Green comet approaches Earth
Astronomy.com - February 9, 2009

Closest approach Feb 24. Near Saturn in Leo.

bystander wrote:Follow the fuzzy blob this month as it races westward from Libra to Leo.

JOAQUIN PHOENIX?

I wonder if it's possible for a comet to have two nuclei which 'orbit' each other .. or tumble together, presenting different faces. Any instances of this? If so, this comet could be one of those.

aristarchusinexile wrote:I wonder if it's possible for a comet to have two nuclei which 'orbit' each other .. or tumble together, presenting different faces. Any instances of this? If so, this comet could be one of those.

Certainly possible- asteroids like this are known, and in many respects, there is little difference between asteroids and comets. But I don't see anything in the images to suggest that Lulin has anything other than a normal, single-body nucleus. It is compact and point-like in images, and there is no cyclical variability in brightness with time.

Chris Peterson wrote:

aristarchusinexile wrote:I wonder if it's possible for a comet to have two nuclei which 'orbit' each other .. or tumble together, presenting different faces. Any instances of this? If so, this comet could be one of those.

Certainly possible- asteroids like this are known, and in many respects, there is little difference between asteroids and comets. But I don't see anything in the images to suggest that Lulin has anything other than a normal, single-body nucleus. It is compact and point-like in images, and there is no cyclical variability in brightness with time.

The escape of cometary gases between the two halves might force cometary nuclei apart.

neufer wrote:

Chris Peterson wrote:

aristarchusinexile wrote:I wonder if it's possible for a comet to have two nuclei which 'orbit' each other .. or tumble together, presenting different faces. Any instances of this? If so, this comet could be one of those.

Certainly possible- asteroids like this are known, and in many respects, there is little difference between asteroids and comets. But I don't see anything in the images to suggest that Lulin has anything other than a normal, single-body nucleus. It is compact and point-like in images, and there is no cyclical variability in brightness with time.

The escape of cometary gases between the two halves might force cometary nuclei apart.

Chris, if you could lend me that telescope of yours, teach me how to point it, do photographs, etc. ... wait .. I'm going canoe tripping soon.

neufer wrote:The escape of cometary gases between the two halves might force cometary nuclei apart.

They might. There's quite a lot of evidence that comet nuclei- or some at least- are little more than rubble piles. And rubble piles that are only a few kilometers across don't have much self gravity to keep them together.

Comets have, of course, been observed to fragment. Usually, this can be explained best by the action of tidal forces as the objects pass close to the Sun or Jupiter, but I think there are also unexplained breakups.

Is it possible that Comet Lulin could be a pocket of ionizing space?

Frenchy wrote:Is it possible that Comet Lulin could be a pocket of ionizing space?

I don't even know what that means. Space doesn't have ionized pockets. It's just a comet. It behaves like one, it moves like one, it has the composition of one. Nothing unusual.