Comets are particularly unpredictable phenomena. The current case is C/2019 Y4, which has apparently broken up into at least three pieces – which at last sight were drifting away from each other. It’s visual magnitude has gone from a sudden brightening to 7.8, but then dropped to 8.8 after the break-up and shows no sign of recovering. This, despite the fact that is nearer to the Sun and the Earth than before. It is not visible to the naked eye, even in clear, dark skies. You might find it with a medium amateur telescope.
There is another, more recently discovered comet in the Solar System called C/2020 F8. It, too has undergone a sudden brightening, but is still a bit to dim to see – even in that theoretical dark, clear sky. Since it is in the Southern sky right now, you could not see it anyway.
I have made some diagrams of both comets with the JPL Small-Body Database Browser and added some explanatory text. The planets are all in the same orientations and positions in both.
“So, what next? “, you may ask. Well, as these comets approach the Earth and Sun – at different rates since the Earth and Sun are 1 AU apart – they will brighten. We cam predict the change due to distance alone. Below is a graph of distances predicted over time for C/2019 Y4 (refer to figure 1). The data are from the aforementioned JPL Small-Body Database Browser The graph was generated by your humble narrator in Excel.
The increase of brightness to be expected (if nothing about the comet itself changes) can be predicted by the total distance involved. Keep in mind that light spreads out such that a reduction of ½ the distance will result in 4 times the brightness. Remember that on this stellar Magnitude scale a reduction of 1 magnitude is the equivalent of more than a doubling (about 2.5 times) in brightness. I don’t make these rules, OK?
This needs some calibration since it calculates only differences. That calibration is taken from a recent observation as noted on the graph (also Excel) that follows.
The conclusion is that the peak brightness will be still below naked-eye visibility – around May 28th. Having said that, you will remember that this exercise assumes that the comet itself will not change. But that’s silly! We just saw it increase suddenly in brightness (far in excess of expectation) and then dim again! That was from eruptions of vaporizing ices, that apparently broke this comet into pieces. I told you these things are unpredictable, did I not?
So, why do this calculation of brightness due to proximity? Because it is all we can do! Keep that in mind the next time someone tells you they can predict the climate. 😉
The same sort of calculation can be done for this Johnie-come-lately comet that just showed up. I will skip all the intermediate explanations and go straight to the prediction chart.
You see that the new comet is likely to be brighter than poor old C/2019 Y4. It will probably become magnitude 6.3 – bright enough to see without binoculars or a telescope – out of city lights, in a dark clear sky -but just barely!
And, just now we have news of an observation from the Comet Observation Database . For April 19th (late in the day) the brightness was measured at magnitude 6.8. You can see the red cross on the graph. That is, however, one of four observations on that day – the other three were all magnitude 7.5. To change the whole prediction on a single observation would not be reasonable, so I will wait to do so until a few more observations are made. Did I mention that these things are unpredictable?
You may ask, “Steve, why did you choose such an uncertain occupation?”
I did not choose Astronomy. Astronomy chose me. It is actually a hobby because, while I wanted to be Carl Sagan, I found out they already had one. So, I wound up looking down through the Earth instead, because someone would pay me for that. Now I have nothing better to do. Well, I have other things to do – yes. But, who wants to mow the yard again?
Before you write me to say, “Why didn’t you photograph the comet, Steve?” – this image is from a telescope with 8 times the light-gathering power of mine. Add to that, the fact that they took 120 second exposures…twenty of them. To do that they had to track the comet as it moved through the background stars that make the streaks you see. Their telescope is guided by sophisticated computerized servos, while my ‘scope is on a mount made from a plywood box and is guided by “pushing with your hand”. Then they stacked those 20 photos together to make this image. These are professional Astronomers in a Swiss observatory while I am just a guy in a driveway in Houston.
I warn you that this is what Literature students call “a bear”! But my preliminary read tells me that the comet fragmentation could pre-sage a disappearance or it may be associated with sudden eruptions of activity that result in a brightening. A long-winded way of saying “Anything could happen”, this is. 😉
There are many reasons a comet might break up but the main two in this case (in my humble opinion) are probably thermal stress and gaseous eruptions of sub-surface ice bodies.
Update: A recently discovered comet in the Southern sky has undergone an “outburst” and is already as bright as Y4. It is not yet in the databases, so no cool diagrams, yet. Details in the next post.
Comet 2019 Y4 (hereinafter called simply “Y4”) is still approaching the inner Solar System and still being observed. It occurs to me that I have not posted an actual image of this comet, So, that will be figure 1:
I promised a diagram to explain Y4’s path through the Solar System. To quote my previous comment:
“ I’ll include a diagram in the next update. But, for now, imagine yourself as very small and standing on an old-school LP record. The gaps between songs are the orbits of the planets. You are on the third gap and the comet is at the 4th gap but high above the LP. It will come in past all the rings and dive into the record inside Mercury’s orbit (1st gap) on May 30th. It will emerge on the bottom side and make a similar, but mirrored, exit path. It is moving at a tremendous velocity because it has been falling toward the Sun since about 1844. -Steve”
With this verbal imagery and the diagram below (figure 2), I hope the situation is well-explained.
I have plotted the position of the Y4 on March 13th and April 10th. Those dates were chosen from the a magnitude chart because the comets was at the same brightness on both. In the meantime, the comet has moved much closer to the Sun. Please see the magnitude chart below and pick up the story below that.
Comets don’t shine like stars, they only reflect the sunlight that shines on them. Before I go further, please remember that magnitude is a smaller number for brighter objects.
If the comet were unchanging, then the fact that it is closer should mean that the brightness would increase from magnitude 8.7 to about 7.9 (just take my word for that:-). Clearly, something did change, because the comet brightened too quickly and then dimmed again. What happened is why comets are so unpredictable.
The comet body, warmed by the sun will begin to “evaporate”. Frozen gasses are vaporized and form a gas cloud around the “nucleus” and are blown away by the radiation from the Sun and the rush of sub-atomic particles called the “solar wind”. That is what makes the comet’s “tail”. The bigger ball of gas reflected more light and so the brightening.
The dimming? Maybe:
The vaporizing gas may have “unglued” the body of the nucleus and it started falling apart.
The stuff beneath the frozen gasses is darker rock and reflects less light.
The ice that was volatile at this temperature has all vaporized.
What will happen next? Maybe:
The comet may fall apart completely and disappear.
Less volatile ices may vaporize when the comet is closer – and therefore hotter – and that will renew the brightness
That last option at least leaves open the possibility that the show is not over.
So, you were warned – and that last part may well be happening now. Below is a collection of all photometric (CCD) observations of Comet 2019Y4 from March 7. Below that is a graph of the distance from the comet to the Sun (orange) and from the comet to Earth (blue) for the same period. The distances are in Astronomical Units – the distance from the Earth to the Sun – about 93 Million miles
You see that:
* The comet was brightening until about April first. Then it declined rapidly until today April 7th.
* In that time, it has gotten closer to the sun, which illuminates the comet better than before and closer to the Earth – where we should see it brighter than before – even without the additional illumination by the Sun.
* See the Conclusions below the charts
One expects a comet to lose mass as it is blown away by the solar wind – that is what makes the “tail”. That would cause a dimming due to a smaller reflective surface and smaller “gas ball” surrounding. This will be offset by brightening by being nearer to the Sun and Earth.
In this case, the dimming is faster than the brightening due to being nearer. The comet is probably wasting away quickly – on its way to disappearing for good.
But, I could be wrong. 🙂
Hasta Luego, Steve
P.S. If you have any questions please use the comments section (Leave a Reply) below and I will answer for all the readers who may have had the same question. Thanks SBC
The weather has been even worse than usual for astronomy. Don’t misunderstand – around here, there are just awful conditions for viewing at the best of times. But cloudy weather has been unusually frequent lately. The comet is still not very bright, in an area of the sky that is devoid of any bright stars for guidance and in a direction that is particularly afflicted with trees and city-light. Nevertheless, I have attempted to spot the comet with binoculars several times – without success.
Attempting to photograph what could not be seen visually of Comet 2019 Y4, I am struggling with an unfamiliar DSLR (digital single lens reflex) camera. Just the camera on a tripod and guessing at various settings of exposure, “film” speed, focus and aperture. No, I didn’t see the comet. I was barely able to detect any stars in the city-light washed-out sky.
One thing that stood out was some much more concentrated and colorful points of light. I wondered what these could be since they were far to point-like to be anything in the sky that was not even properly focused. Despite that these were intense and focused bits of light.
The bright spot in the red circle of figure 1 – what could make such undeniable point-like events? The answer came back – after considerable snaky-eyed concentration – these must be traces of cosmic rays. As it turns out – I was right. The lens of the camera has nothing to do with these images. The high-energy particles pass through the camera body from any and all directions. If at a low angle to the “chip”, the image extends to an oblong shape, like the examples below.
The irony is that the comet, which is right here in the Solar System – along with stars that are in the visible “neighborhood” are so elusive, while cosmic rays, which may originate half-way across the universe, are showing up clearly as “volunteers”
It has become clear that I will have to make a trip out to a dark sky location to see this comet. That may take a while, so I will hone my skills with the binoculars and camera, in the meantime.
Others are not so unfortunate in their efforts to see this comet. Collected observations of the comet show that it has dimmed in the last week. Please see figure 4.
Comets show up all the time and are observed by telescope. The rarity is of “naked eye visible” comets. My personal experience is that they show up aboutonce per decade (click here).
I was due for another comet and it has shown up.
The media are incorrectly calling it “Comet Atlas”. Search for that name and about three dozen comets will pop up because ATLAS is the acronym for the name of the observing system that discovered it, not that of the comet itself. The Asteroid Terrestrial-impact Last Alert System is – as the name reveals – a project to find asteroids. It does occasionally discover a comet and it finds thousands of supernovas – in other galaxies – none are even close to “naked-eye objects”.
As most nerdy people know, comets frequently defy prediction and disappoint millions of viewers. Thus far, Comet 2019 Y4 has only defied prediction by rapidly brightening far in excess of prediction. Please see graphic below.
The green line plots the predicted brightness. Points in blue are from actual observations. Note that this comet has grown to near naked eye visibility (from a dark sky, not in city lights).
Where to see this? A screen grab of a sky map from Heavens-Above.com for 3/25 to 3/27 (with text and markings by your humble narrator to “Un-nerd” same) appears below.
Update: I tried, unsuccessfully, to see this comet with binoculars – in glaringly lit-up Houston skies on March 24. The latest brightness observed (by professionals) is Mag. 7.6 as of 3/25. But, it will get brighter, soon.
Steve Campbell November 2015 – Updated: July 7, 2020
Sunspots have been studied for over 400 years by such notable scientists as Galileo. Many earlier observers had noticed that the sun was occasionally marked with darker spots. But, Galileo spread the word about sunspots and many of his contemporaries subsequently took up regular observations of same.
Observation of Sunspots
Right here is where I will repeat a warning that you may have heard a hundred times before: Do not look directly at the Sun and especially DO NOT look at the Sun in a telescope. The only exception to that last part is where a Qualified Astronomer is using a proper solar filter or is projecting an image from a telescope onto a screen.
That Galileo made use of a telescope around this time was strictly coincidental. Observations of the Sun were done during sunrise and again at sunset when it is possible to notice large sunspots with minimum damage to the eye. The sunlight passes obliquely through the atmosphere and is very much attenuated.
An image of the sun can be projected by a “camera obscura” which is essentially a darkened room with a tiny opening – literally, a “pin hole”- through which the sunlight enters. For reasons we won’t go into here, a pin hole acts like a lens and focuses light. By careful placement of a screen of cloth or paper, a focused image appears, large and bright enough to sketch. The astronomer Johannes Kepler was known to have used this system to view the sun. In an interesting side note, Kepler thought he was seeing the planet Mercury passing between the Earth and the Sun, instead of a spot on the sun itself. Had he checked on the following day, he would have seen the same spot and because he knew that a Mercury transit would not last a day, he would have seen his error.
The method of projecting an image from a telescope onto a screen was developed by a protégé of Galileo named Benedetto Castelli.
“It was Castelli who developed the method of projecting the Sun’s image through the telescope, a technique that made it possible to study the Sun in detail even when it was high in the sky”. (1)
The following quote explains a bit about the “Sunspot Number” which was established as the metric of sunspot activity.
“Continuous daily observations were started at the Zurich Observatory in 1849 and earlier observations have been used to extend the records back to 1610. The sunspot number is calculated by first counting the number of sunspot groups and then the number of individual sunspots.” (2)
I would be remiss if I did not include actual images of sunspots with this discussion. Figure A shows a recent image of the sun taken by the Solar and Heliospheric Observatory (SOHO). This is a NASA space probe that orbits between the Sun and the Earth constantly monitoring the Earth-facing side of the Sun.
By the method described (Count the groups and multiply by ten then add the number of individual spots), I would estimate the sunspot number to be between 35 and 45. Don’t quote me. I know there are limits to how small individual spots can be and still be counted, but I don’t know what those rules are.
Figure B shows an image of the Sun during the Cycle 23 Maximum.
I am not sure of the origin of this image, it may not be from the SOHO probe, but in any case, it illustrates the difference between high and low sunspot counts. Again, I don’t do this for a living, but I would guess the count here to be well over 100.
Update April 8, 2020:
The solar minimum continues unabated. This count is obviously zero and is typical lately. Some spots from the next solar cycle have shown up, but they don’t last long. In this image, the count is zero.
Update 07/07/2020: Spotless Days plot:
The following graph confirms the continuing solar minimum, but requires some explanation. For the complete version, go to the SILSO Spotless Days Page
For the mercifully short version read my explanation, below the graph.
The solar cycle, in all its years of observed activity, has had (arguably) two types of cycles. Those with large peaks and short minimums between – and those with small peaks and long minimums between. The graph above segregates the two types as averages (the solid red and blue lines) and plots the number af spotless days accumulated in the current cycle (solid green line). The dotted pale blue and magenta lines are the “standard deviation” plots for the low-peak minimua (cyan) and high-peak minima (magenta). “Standard deviation” is what science nerds say instead of “what is reasonable to expect”. As you see, the current Solar Minimum has made it obvious that this is a major departure, not just from the big-peaks variety, but also it is the outlier from the big minimum/low maximum cycles. In short, like nothing in living memory.
Summary: Confirmed: Expect colder temperatures for the next decade or three.
The following is from the NOAA Space Weather Prediction Center
Below: The latest is still from Dec 2019. Your humble narrator predicts that the double peak will again show up. – no doubt with greater separation as indicated by the last 3 cycles. (see figure D)
Updated July 7, 2020
The following prediction by Irina Kitiashvili at the NASA Ames Research Center predicts even less activity for Solar Cycle 25 – the least in 200 years. It turns out to be a bit before the NOAA prediction, but not by much.
So, the “experts” disagree. But, there is undoubtedly something unprecedented going on.
Figure below shows the accumulated sunspot numbers over the last 400 years of solar observations.
It is ironic that Galileo took an interest in sunspots and popularized such observations just in time for the Maunder Minimum when sunspots gradually became rare phenomena. The Maunder Minimum is associated with the Little Ice Age, when weather was cooler than today. The numbers of that time are yearly averages due to the sparsity of observations. From about 1750 onward monthly averages are plotted – results of sustained, systematic observation. The Maunder Minimum is still a valid conclusion, but the data cannot be said to be “high resolution”. The later Dalton Minimum is much better defined and typically associated historically with “Dickensian Winters”. In recent years, those types of winters are returning to England.
Magnetism and the Climate Connection
It is the changing magnetic field of the Sun that drives the existence or absence of sunspots. The Solar magnetic field changes on a long time scale and with different periods of oscillation. The most obvious of these is an eleven-year cycle that dominates in Figures C &D. The magnetic properties actually reverse in polarity in each new cycle, which makes it a twenty-two-year cycle in reality. Periods of high sunspot activity are associated with high magnetic field strength and a dearth of sunspots is an indication of low magnetic intensity.
A plot of terrestrial magnetic field strength in Figure E demonstrates the cyclical nature of the terrestrial magnetic field as influenced by the sunspot cycle. (3)
As indicated by the note in the seventies, periods of lower terrestrial magnetic field strength are associated with colder weather. This effect has been explained by the work of Henrik Svensmark (6) who demonstrated that magnetism effectively blocks cosmic rays. But, when the field strength is low, the increase of cosmic rays makes cloud formation increase and global temperatures drop. Now that the Ap index has dropped to unprecedented lows and the global temperatures have failed to increase as predicted by many, this association would seem to be confirmed.
The fact that ”official” temperatures have not actually dropped may have something to do with the manipulation of those datasets by certain individuals who have reduced the number of weather stations averaged from over 6000 to about 400 and shifted the average latitude of those stations from that of Oklahoma City to that of Hawaii (5). Please note that before they began eliminating stations (circa 1975), the average was indeed, dropping! See figure F.
An examination of sunspot trends clearly indicates a new Solar Minimum (of Dalton or Maunder proportions) is in the works. A cooler environment is to be expected in the coming decades.
When climate considerations come into a subject, a thorough search always seems to reveal data manipulation has occurred. All with the same result – a cooler past and a warmer present.
October 13, 2016 “Reprinted” August 31, 2019 from WordPress
Last Chapter, there was a load assignment waiting and it was a good one. I pick up a load of meat in Sioux Falls South Dakota and deliver it to Stockton, California. Wyoming, Utah and Nevada are in between.
I am still starting my driving day just after midnight and it is working well. The roads are clear and the truck stops uncrowded when I arrive. The deadhead from Roberts Wisconsin goes smoothly. I made a 30 minute break in a rest area near Blue Earth Minnesota. At 4 AM it was eerily silent and empty. I have been puzzled about the origin of the name Blue Earth since I encountered it in 1973 while traveling to Minnesota to meet the family of my step mother. I cannot yet tell you where it comes from, since I cannot manage an internet connection from this dusty little town in Northern Nevada where I am writing.
(From Ripon, California) Blue Earth gets its name from the Blue Earth River that surrounds the town. The river was given the Native American name “Mahkota” (meaning Blue Earth) for the blue-black clay found in the river banks.
The stars are particularly bright and the Milky way is plainly visible when I can put the truck between me and the flood lights. The Astronomer in me is not yet lost, but he does not get much time on the field
Above: Orion is a constant of the winter sky. Go see it if you get a chance. The red star is Betelgeuse. The three stars down by the “x” are called Orion’s Sword”. There is a technique called “averted vision” which I will teach you now. Look at those three stars in Orion’s Sword. They will look like ordinary dim stars. Now look away just a little bit – about where the “x” is. Notice that the middle star will go “fuzzy” on you. That is the Orion Nebula. Averted vision works because the light detecting cells in your peripheral vision are more sensitive than in the direct line of view. Weird, but true.
I tried to grab photos by blindly clicking the camera at these majestic sights without taking my eyes off the road. This is a very inefficient process that produces a lot of reject pictures that are either blurry, full of dashboard reflections or just don’t live up to the scenery. For each one you see here, there are ten or more that don’t make the cut.
This state starts off as rolling hills of dry grassland and ends that way. Even after my vigorous culling, there is a beauty to which this picture still does not do justice.
There must be a better way to capture images. I am looking into a time-lapse dash camera. Recommendations?
Some of you readers are aware that I have been working as a Telescope Operator at the George Observatory at Brazos Bend State Park. There are three domed instruments that are open to the public for viewing on Saturday nights – weather permitting. I get to operate the smallest to these — a 14 inch Schmidt Cassegrain instrument. For non-Astronomy Nerds, the 14 inch number refers to the diameter of the mirror that is inside the big, black tube.
BTW: Brazos Bend State Park, where the George Observatory is located, was closed for flooding until early July. It re-opened just briefly but is now closed for long-overdue renovation. So, this activity of mine is “on hold”. I volunteered over at the Museum of Natural History – more about that later
We might have forty or more visitors on an average night, but even so there are occasional intervals when I can make some photographs. There was one night when the atmospheric conditions made the “seeing” miserable, but I still managed to catch some images of Saturn. Most detail of the planet and rings was lost, but a couple of satellites were captured in one long time-exposure where the planet and rings were overexposed. You might need to zoom to see the moons.
More recently, on a night with better seeing, the Orion Nebula was captured in a series of different exposure times. I include two below.
There are methods, these days, to stack (combine) multiple images and get far more impressive results. I am looking in to that.