Thursday, July 9, 2020

The mysterious and beautiful Comet NEOWISE







































image: Wikimedia commons (link).

I've just returned from getting my first view of Comet NEOWISE, which is the first naked-eye visible comet I've seen since Comet Hale-Bopp in 1997. 

At present, it is nowhere near as easily visible to the naked eye as was Comet Hale-Bopp all those years ago, but it is certainly spectacular nonetheless and well worth the effort to go see it in person, if it is at all possible for you to do so. Additionally, we have been told that the comet may become even more visible in the days and weeks ahead.

You will definitely want to use binoculars. The comet is gorgeous through binoculars but not easily visible with the naked eye. After finding it with binoculars, I was able to see it with the naked eye (actually I wear either glasses or contact lenses, so not exactly the naked eye) but it was not at all obvious in the sky and would not be something you would likely notice while driving, for example. I did find it easier to see with the naked eye when looking at a point not directly at the comet, which is a trick that can be used to help observe fainter objects in the night sky (I also use this technique sometimes when looking for the Beehive Cluster, although the Beehive is not visible at this time of year -- wait a month or two).

The comet (dubbed C/2020 F3 NEOWISE, or simply Comet NEOWISE, after the name of the space-based telescope which first discovered the comet on March 27 of this year) is presently visible before dawn, leading the sun from our perspective on the turning earth. 

After July 11, the comet will transition from being visible in the pre-dawn sky (in the east) to being visible just after sunset (in the west): there will be a period during that transition in which the comet will not be visible but it is expected to reappear in the post-sunset western sky around July 14 or 15.

I have to drive to get to a good unobstructed view of a relatively flat eastern horizon, so I got up early this morning (July 09) and drove to a place looking over a wide open field with clear views of the eastern horizon, parked my car and turned off the lights to await the appearance of the comet.

The moon is waning now, having already passed full moon over the July 4 - July 5 weekend, but is still gibbous (larger than a "half-moon" shape, which is technically called a "quarter" rather than a "half-moon"). The planets Jupiter, Saturn, Mars and Venus are all very visible and range across the sky from west to east in that order like a long string of jewels which traces out the general path of the ecliptic. Below I've created a screen-shot from the free open-source planetarium app Stellarium to show the sky as you would see it from the perspective of a viewer in the northern hemisphere (I am at a latitude of about 35 degrees north). This screenshot is created for the morning of July 10, tomorrow morning:























In the screenshot above, the viewer is facing roughly towards the east, but the view is centered almost directly southeast. The comet is actually found in the northeast, to the left of the image as you face it. Ranging across the sky you can see the bright planet Jupiter on the far right of the image, sinking down towards the west following the constellation Sagittarius. Close behind Jupiter is the planet Saturn, not nearly as bright in the sky as Jupiter but clearly visible to the naked eye (you will need a telescope if you want to spot its rings, of course).

Continuing across the sky you will of course be able to easily see the moon, glowing brightly and enlarged in the screenshot above to approximately the size that it would appear when you go outside into the predawn sky. Not far behind the moon in its path along the ecliptic you will also be able to easily identify the red planet Mars, which was very bright when I went out this morning to observe the comet.

I have included the constellation outlines in the above screenshot, using the outlining system of H. A. Rey. I have drawn in the outline of the Great Square of Pegasus, which is very easy to find almost directly above Mars and which can serve as a landmark for you in the sky (you may need to block out the moon with your hand in order to see the Square).

Continuing towards the west you should have little difficulty identifying the dazzling star-cluster of the Pleiades, which are located not far below the "foot" of the constellation Perseus and almost directly above the bright planet Venus, which is rising in the east and is currently found very close to the reddish star Aldebaran in the constellation Taurus. I have labeled the Pleiades on the star-chart above and you should take some time to look at them with your binoculars.

I use a set of Barska 10x50 WA binoculars, shown below, which are excellent for star-gazing purposes. I do not get any incentive to endorse this product, in case anyone is wondering if that recommendation is biased in any way.































Once you have located Venus and Aldebaran in the eastern sky, you are ready to find the location of Comet NEOWISE. The comet is located well to the north of due east, about halfway between due east and due north. I used the compass feature on my smartphone to shoot a rough azimuth towards the comet once I had located it, and estimated it to be on an azimuth of about 323 degrees from my observation point on the planet, but a phone app compass is not a very precise tool for shooting an azimuth: I wish I had brought a good solid old-school lensatic compass like we used in the army, with has a handy sight-window for shooting a more precise azimuth.

The comet is located almost directly below the bright star Capella in the constellation of Auriga, the Charioteer. It is actually a bit to the north of Capella, but trailing Capella in the sky, as shown in the star-chart above. 

The way I usually find the constellation Capella is to follow the V-shaped Hyades, a "V" in the sky which contains the star Aldebaran -- but because bright Venus is situated right next to Aldebaran, the "V" of the Hyades is not so easy to see right now. The two tips of the "V" point to the two stars which make up the "horns" of Taurus the Bull (at least, the way I myself like to outline the constellation, which in this case differs from the outline suggested by H. A. Rey, one of only a very few constellations where I use a different approach than that suggested by Rey). Below is a close-up of the region of the sky with Auriga and Aldebaran and the comet to show how I usually find the outline of Auriga:


























The "V" of the Hyades is usually very easy to identify, and it points almost straight towards the two stars which make up the "horn tips" of Taurus, which are labeled in the close-up screenshot above. Finding these horn tips helps you to distinguish between the stars of Auriga and the stars of Taurus. The constellation Auriga, as outlined by H. A. Rey and shown in the image above, looks like an enormous disembodied head, with the bright star Capella as the eye (and a kind of "broken-nose" just below the eye of Capella). I have added a single red line to indicate what I call the "jawline" of the constellation Auriga, which is easy enough to identify in the sky if you can find the two "horn tips" of the constellation Taurus as shown in the above image.

You won't actually need to find the horn tips in order to find the comet, however, or even the "jawline" of Auriga, and you don't need to see the V-shaped Hyades which is difficult to identify right now because of the location of Venus. All you really need to see is the bright star Capella, which is pretty easy to identify in relation to Venus, Aldebaran and the Pleiades as shown in the chart above. From Capella, you will actually be able to see the comet well before the second "horn tip" of Taurus even clears the eastern horizon as the stars are rising.

I did not see the comet when I first arrived at my observation spot shortly after 4am. However, about ten minutes later, as I was training my binoculars towards the horizon at roughly the location indicated by the large red arrow in the above diagram, I saw what looked like the upward-pointing glow of a distant spot-light pointing almost straight up from the horizon. I said to myself, "If that 'spot-light' glow is the comet rising over the horizon, then I am impressed."

It was.

The tail of Comet NEOWISE is very long and beautiful and easily visible with binoculars. As the earth continued to turn on its axis, the entire comet rose above the horizon at about 4:17 am. The time will vary based on your exact latitude and also based on the terrain of your eastern horizon where you are located.

As the minutes went on, the comet rose higher and higher above the horizon. It was spellbinding to gaze at it, the bright head of the comet clearly visible and the ghostly tail rising up above for a very long distance, much longer even than what you see in the top photograph from the Wikimedia commons collection, which was taken closer to sunrise by a photographer in Landers, California on the morning of July 07 using a 200mm lens.

I've tried to approximate the size of the comet's tail in the star-chart images above. The tail is pointing almost straight upwards but slightly leaning towards the north, from where I was observing it (in other words, the top of the tail is slightly north in relation to the head of the comet at the bottom, or "leaning towards the left" as we face towards the east). That orientation will change as the earth turns and the comet rises, however.

This is a very beautiful comet, but definitely one which at this time requires binoculars to really appreciate. I was able to see it with the naked eye but only as a kind of chalk-line of haze, and could not make out the head of the comet without the binoculars (but the entire comet is clearly visible as a classic comet-shape, with distinct bright head and mysterious hazy glowing tail, using the 10x50 binoculars mentioned earlier).

I hope that this description of the location of the comet will help you find Comet NEOWISE and see it in person, if you are able to do so over the next few days.