Tag: comets

Comet 2019 Y4 4/14/20

April 14, 2020

The comet is breaking up!  I will attempt to imbed this image and its source.  Don’t be surprised if you see it more than once.

Figure 1: Y4 is breaking apart


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.

The pieces are estimated to be spread out over more than two thousand miles.  This is not unprecedented and if you want to learn more try looking at this paper:  Split Comets   H. Boehnhardt Max-Planck-Institut für Astronomie Heidelberg

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.

More Later,


Comet 2019 Y4 04/11/20

Homepage  5 Decades, 5 Comets

 By Steve Campbell     April 11, 2020

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:

Figure 1: This is Y4 as of March 21, 2020. It comes from a 16 inch telescope, see link below.

 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.

Figure 2: The path of Y4 through the Solar System

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.

Figure 3. Note the maximum brightness observed on March 13 the and April 10 are about the same at about magnitude 8.7

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.

Hasta Luego,


Comet 2019Y4 4/7/20

Update on C/2019Y4  April 7, 2020

(See all updates by clicking on the comets icon at the top of my home page)

Readers may remember that I wrote about this comet:

“As it nears the sun, it will brighten quickly.  It could become the brightest object in the sky.  However, it may just break apart and disappear.  See the text on figure  1 at This link

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

Comet 2019Y4 April 3

April 3, 2020 – update on Comet 2019Y4

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.

Figure 1: In the blue circle, a star. Doubt me if you must, but it is there – about half the diameter of that blue circle. In the red circle, an unexplained cluster of bright pixels

Figure 2: Zooming on a longer exposure frame, this is a star, blurred by incompetent focus and unstable air.

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.

Figure 3. Left: the example of a cosmic ray trace in a DSLR camera at the website found by googling cosmic rays. Right: Extreme zoom, on what I found on my DSLR during my attempts to photograph the comet.

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.

Figure 4. It can be seen that the brightness fluctuates, but is in a down trend in the last few days.

Hasta Luego,



Comet 2019 Y4

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 about once per decade (click here).

I was due for another comet and it has shown up.

Figure 1.

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.

Figure 2. Note that “Magnitude” goes to smaller numbers as things get brighter.

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.

Figure 3.

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.

Update: No luck on the 25th, either.

An up-to-date sky map for locating Comet 2019 Y4 is here.

That Heavens-Above.com map is at the link below:

Hasta Luego,