Category: comets

Urban Astronomy – Comet Leonard

Unmasked and Unafraid

Posted December 19, 2021

The night sky is pretty much a mystery to most City Dwellers.  The glare of city light drowns out all but the brightest stars – and planets don’t do much better.  If you are interested, I can tell you where to look to see these far-off worlds.  If you were not interested, you would have stopped reading after the first sentence. 

So, at this point, I know my audience. 

Comet 2021 A1 – Leonard

There is another “Eyes Only Visible” comet to be seen in the Southwestern sky, just after sunset. The current magnitude of Leonard is +4.6, so in the city, it is only just visible and would be better seen with binoculars.  Once again, do not use telescopes or binoculars to view the Sun – blindness will result!  I said “after sunset” so you should be OK if you listen to me. 😉

As is usual in these cases, the comet gets brighter not only because it gets close to the Earth.  It also gets brighter because it gets closer to the Sun.  The third brightening influence is the material that the closer sun vaporizes.  That stuff makes a cloud around the comet and is it also partially blown away by what is called the Solar Wind – in a comet’s tail.

Figure 1, above shows the location to view, which is conveniently close to Venus, which is the brightest thing in the sky.  If you can see the Planet, you should be able to see the comet – although you may need those binoculars to do so.  

We have had very cloudy weather here in Houston (today, Dec 19) is “Mostly Cloudy” at 4 PM, changing to “Cloudy” around Sunset at 5:26 PM.  Tommorow at Sundown the prediction is “Mostly Cloudy” and the comet will have moved slightly relative to Venus.  These next few days are literally the last chance to see Leonard, as it is on a hyperbolic orbit – which is a nerdy way to say that it will never return to the Solar System.  (Please see figure 2 below)

Figure 2. Comet Leonard is diving through the Solar System, never to return.

For readers not in the Houston area, just look for Venus (and Jupiter for orientation) and use the chart above to find the comet.  We are lucky to be able to have the two brightest objects in the sky (now that the moon is not around in the early evening) as our reference points.

Hasta Luego,

Steve

Comet Update 7/31/2020

7/31/2020 Comet 2020 F3 is now receding back into the distant reaches of the Solar System.  As yet, however, it is still closer to the Earth than the Sun and closer to the Sun than the Earth is.  This should make one appreciate just how rare and fleeting is the opportunity to see these events with “Eyes Only”. 

In point of fact, I – your humble narrator – did not actually see this comet without the use of binoculars.  And even then, it was only a fleeting glimpse – out of the corner of my watering eye (1).

“Above the planet on a wing and a prayer
My grubby halo, a vapour trail in the empty air
Across the clouds I see my shadow fly
Out of the corner of my watering eye
A dream unthreatened by the morning light
Could blow this soul right through the roof of the night”

That was on July 24th when a rare cloudless Northern sky presented itself and I was awake at the proper time.  I attempted to show this to all the immediate   family.  For the record, it is painfully difficult to describe how to point the binoculars to another person, despite placing the student in the recently vacated footprints of the Astronomy Nerd and the use of tree branches as reference points.  And even when it works, the family member is underwhelmed by the dim little streak that is seen.

Figure 1:  The “Standard” graphic updated for July 30, 2020.  Green series: calculated for distance alone.  Blue series: Daily average of Observations (COBS)

In  figure 2, below is seen the orbital configuration of the comet as of July 31st.  The comet – known by the mundane press as ”NEOWISE”   (which is the name of the space probe that discovered the comet, modified by its extended mission prefix) is actually named only “C/2020 F3”

Figure 2: Orbit Diagram of C/2020 F3 as of7/31/2020

A Norwedian collegue and reader was also able to spot the comet – despite being so far North that he had to wait until a half-hour before Midnight for the sky to be dark enough.  As he pointed out, that left him with about one hour of observation time until the sky woould be brightening again.

“Wola.

Spotted it now with a Nikon 10-22×50

Still hard, but knowing where to look is key.

Thanks…”

I have searched for a definition of “Wola” and can only come up with a Polish district:

“First mentioned in the 14th century, it became the site of the elections, from 1573 to 1764, of Polish kings by the szlachta (nobility) of the Polish-Lithuanian Commonwealth

The Wola district later became famous for the Polish Army’s defense of Warsaw in 1794 during the Kościuszko Uprising and in 1831 during the November Uprising, when Józef Sowiński and Józef Bem defended the city against tsarist forces.”

I would continue to search, but I am busy now making Uber commerce at an accelerated rate to fund the difficulties chronicled in Uber Ally   – where I owe an update to my Norwegian colleague. 

This Comet update is also overdue and I hasten to publish same.

Hasta Luego,

Steve

Comet Update 7/19/2020

Comet 2020 F3 is creeping up in the post-sunset sky.  On July 14, I may have seen it dimly through the distant haze – in moments when the nearer and opaque clouds drifted out from in front.  In those 20 seconds, I saw what could be the nucleus of the comet through a pair of binoculars.  Any hint of a tail was not to be seen.  But, the sky map doesn’t show anything else in that part of the sky that would be bright enough to show through the haze.

I don’t call out family or friends for these desperate attempts at observation.  Mostly because – when asked to point out this astronomical wonder – I am forced to say,

“See that cloud over there?”

“Yes, I see it.”

“The comet is behind that cloud.”

“How do you know?”

“Because that’s where the sky map says it should be.”

“I mean, how do you know for sure?”

“…I don’t.”

That’s why astronomers have been considered lunatics – for centuries.  You may think I’m joking, so look up a Danish fellow named Tycho Brahe.  (Teak – oh  Bra-hay)

Figure 1:  The “Standard” graphic updated for July 19, 2020.  Green series: calculated for distance alone.  Blue series: Daily average of Observations (COBS)

Figure 2:  Sky map as found at the July 14 link on the previous update.

Figure 3: Sky map as modified by your humble narrator to reflect actual field conditions.

On the next day, July 15, the forecast was for clear skies after sunset, but I made the Rookie Mistake of not setting an alarm and slept through the opportunity.  Astronomers have to set their schedule by when the observation presents itself. 

As Shakespeare wrote, “It is the stars, the stars above us, govern our condition.”

Shakespeare also wrote, “The fault, dear Brutus, is not in our stars, but in ourselves”. 

So, I have no excuse for not setting the alarm.

July 16-19, 2020    9:00 PM  See that cloud? The comet is behind it.

In a message from my long-time reader and cousin:

My friend is in OK right now. I gave her all the info last week. I just got this message:

“WE SAW NEOWISE!!!!!

It was so awesome!!  I was so excited like a kid walking into Disney World!! 
It took us awhile to see it but it has to be very dark and we were out in the country..
The tail was very clear and all the stars around it just highlighted the beauty…”

My reply:

I am happy to hear that someone has seen this comet.  It is starting to dim now as it recedes from the Sun.  It has yet to make its closest approach to the Earth, but any brightening by proximity is more than canceled by a more distant Sun and a calming of gas and dust emissions due to less Solar heat and radiation.

Sky maps (from  Spaceweather.com): July 18, 19, 20.

And a 3 ½ minute exposure by James W. Young – also from spaceweather.com

Figure 4 Three and ½ minute exposure (tracked – or the stars would smear) by James W, Young – from Spaceweather.com

Clear Skies!

Steve

SpaceWeather.com

https://spaceweathergallery.com/indiv_upload.php?upload_id=165446

COBS:  https://cobs.si/analysis

Comet Update 7/13/2020

Comet 2020 F3 is making the promised rise in the Northern sky. It shows no sign of breaking up. It is approaching its closest point to Earth and should hold its brightness until then.

Figure 1: Orbit of Comet 2020 F3 generated by JPL Small Body Database Orbit Diagram Widget. Augmented and annotated by your humble narrator.
Figure 2: The “standard” graphic for my updates

Now is your chance.

The comet is as bright as can be expected.  It is coming into a position where it should be visible in the early evening sometime in the next week or two.  Infra-red observations indicate that the nucleus of the comet is about five kilometers (three miles) across, so it is not likely to fall apart.  The brightness should be comparable to the stars of the Big Dipper, at least.

Sky Maps for July 13 through 17 (from SpaceWeather.com) are linked here: 

Morning sky maps: July 13, 14, 15, 16, 17; Evening sky maps: July 13, 14, 15, 16, 17

Here is another SpaceWeather.com photo taken by Petr Horálek on July 12, 2020 @ Seč, Czech Republic

Figure 3: Petr is using time exposure here so this may be better than you might see. He claims that he rowed out while leaving his expensive camera taking photos automatically and didn’t realize he had drifted into the field of view. I think this was posed, since his oars were out of the water long enough for the ripples to have died down.

Clear Skies!

Steve

SpaceWeather.com https://spaceweathergallery.com/indiv_upload.php?upload_id=165446

COBS:  https://cobs.si/analysis

Comet Update 7/3/2020

stevetrucker2

Comet 2020 F3 is still in one piece and still brightening.  As in the previous update it is rounding the Sun in the fast, sharp curve that includes the Perihelion (closest approach to the Sun).

See Figure 1, below

C2020_F3_Orbit_July 2
Figure 1:  Orbit of Comet 2020 F3 generated by JPL Small Body Database Orbit Diagram Widget.  Augmented and annotated by your humble narrator.

Spaceweather.com features a four-day movie of the comet’s appearance in  the LASCO instrument onboard the Sun-watching SOHO probe.

There were at some observations, after the comet left SOHO’s field of view.  Seven are now documented in the COBS database as bright as magnitude 1.0  – comparable to the brightest stars in the sky.

See it also in the now “standard” graphic for my updates- below.

LightCurve_Calc_OBS_2020F3_7-3_ANOT
Figure 2:  The Standard Graphic.

After the SOHO data (red circle) are “conventional” telescope observations and you might think that a decline is happening.  Don’t take that to the bank, because these observations are from telescopes looking just above the horizon and just before dawn.  That is a lot of atmosphere to look through and a lot of twilight interfering.   Estimates of brightness of the comet might be inexact.

Note that:

The “Calibrated Prediction” (green dots) has about July 17th as the peak brightness.  That is based solely on the distances (Sun to Comet to Earth) and assumes that the comet reflection characteristics never change.  That is – of course – never true of comets when they warm up near the sun – emitting gas and dust chaotically.  So, why do the “prediction”?  Because then we know how much of the brightness variation may be attributed to distance alone.  We can take that effect out to study the changes in reflection characteristics…including periodic variations that must be due to rotation. 

If this sounds like an “inexact science” – good!  All Science is inexact!   However, a good Scientist can give you some idea of just how inexact his science is.   😉

Challenging the Dawn

Oscar Martín Mesonero of Salamanca, Spain, also saw the comet in morning twilight.  See his photo below (also from Spaceweather.com)

F3_low_tel_photo
Figure 3:  Mesonero’s photo of C/2020 F3

The comet is here seen as more-or-less “head on” and seems to vaguely show a bifurcated (two part) tail.  That is not unusual as gas particles may be ionized and affected by the Sun’s magnetic fields and solar wind.  The dust particles tend to stream out behind the orbital direction of the comet’s path, while still blown around by solar wind.  Sometimes the two line up as viewed from Earth, other times, not so.

Hasta Luego,

Steve

Comet Update – 6/26/2020

Comet C/20020 F3 (hereinafter mostly referred to simply as “F3”) is now very close to the Sun as viewed from Earth.  Pointing highly complicated and hideously expensive telescopes near the sun is a process to be avoided and so there have been few observations of F3 lately. 

Let me make this perfectly clear – do not try to see the comet at this time when it is near the Sun!

On the other hand, some instruments are specifically designed to look at the part of the sky around the Sun.  One is aboard a probe called Solar and Heliospheric Observatory (SOHO*) that orbits between Earth and Sun in what is called a “halo orbit” around a “Lagrange point” (which has nothing to do with any personal service establishments in the City of La Grange, Texas).

*Note that the acronym should be SHO or SAHO, but SOHO sounded cooler so they use that.

The short story is that SOHO studies the Sun and its atmosphere and comets appear in its field of view from time to time.  F3 has made an appearance there and somebody has measured the brightness about once per day and added that to the COBS (another fractured acronym) database. 

As the comet nears the Sun, it heats up, emits more gas and dust and brightens in excess of distance effect. In the figure below, you can see that the brightness has come close to second magnitude.  Nevertheless – do not try to see it!  SOHO is out in Space and has specially designed instruments – you aren’t and don’t. There will come a time when you can look at it safely and I will be glad to tell you when.

Figure 1: Predicted vs. observed magnitude for Comet C/2020 F3

Below is the SOHO image of the comet for today, June 26.    

Figure 2: SOHO image of Comet 2020 F3 (they call it NEOWISE)

NEOWISE is a project name associated with the Wide Field Infrared Survey Explorer (WISE) which has discovered 28 comets and 313 Near Earth Objects.  That is why Your Humble Narrator does not use “NEOWISE” or any other project or imaging system name as the name of a comet (or other object), like the mundane press so often do.  Because…which one?!  You would think that the SOHO people would realize this…but NO! 😉

Update: I find that the text additions on this graphic are not from the SOHO folks, but added by a third party who shall remain nameless!

In the future, I will quote SOHO graphics myself and add any text for clarification – with attribution to myself alone.

Hasta Luego,

Steve

Comet Update 6/16/20

Comet Update C/2020 F3

Yet another comet approaches and has already been promoted as an “eyes only” event.  Not by me, of course – because I have learned the hard way that comets almost always disappoint – mostly because astronomy nerds are too quick to get excited about such things.

It is called C/2020 F3 and is approaching from the southern part of the Solar System.  I include (figure 1 below) a diagram  (made with JPL’s Small Body Orbit Diagram Utility and appropriately annotated by your Humble Narrator.)

Figure 1. Comets can originate from most any part of the sky. Many orbit near the plane of the solar system. This one does not.

As before, I have calculated the expected change of brightness due to distance alone (green curve on the graph below) and plotted the observed brightness (blue dots) for the comet. See figure 2 below.

Figure 2. You can see why comet nerds are predicting this as a spectacular sight – it has far exceeded expectations already Remember Magnitude 6 is “eyes only” brightness. One prediction in “cometnerdland” is 2 to 3.

I will be watching this one as well.  Updates as they occur.

No, you can’t see it yet and neither can I.

Hasta Luego,

Steve

Comet Update 5/26/2020

Comet 2020 F8 has dimmed well below “eyes only” visibility and seems destined for obscurity.  Now that it has passed Perigee (closest distance to the Earth) and is passing Perihelion (closest distance to the sun), there can be no expectation of brightening, based on distance alone.  Another outburst of erupted gas and dust also seems unlikely, so this is probably the end of the story for C/2020 F8. -Update: Yes, it was the end.

Figure 1. Predicted “distance only” brightness and actual observations
Figure 2: Comet’s path through the Solar System.

Next, I am thinking of a project to confirm the rotation period of a historical comet using the phase analysis as described in my  Comet Update of April 26 This will utilize that data at the Comet Observation database. It will serve as proof that I am doing this analysis correctly.

Comet Observation database (COBS) saw first light in 2010 and is maintained by Crni Vrh Observatory. It is a free and unique service for comet observers worldwide which allows submission, display and analysis of comet data in a single location.

Amateur astronomers can make valuable contributions to comet science by observing comets and submitting their observations to COBS as professional astronomers typically do not have telescope time required to acquire regular observations. We therefore encourage comet observers worldwide to submit their observations and contribute to the COBS database.”

COBS homepage

Orbit diagrams and distance info: https://ssd.jpl.nasa.gov/sbdb.cgi#top

Comet Observation database: https://cobs.si/analysis

Hasta Luego – Steve

Comet Update 5/19/2020

Comet 2020 F8 has dimmed from its last outburst and is now just barely qualified to be “eyes only visible”.  I call it that only in the abstract since I have attempted to spot it several times with binoculars without success.  I live on the west side of Houston and the place where the comet is theoretically visible is in the northeastern sky – which is awash in city-light at best – just before dawn.  My carefully chosen location is down south on a road that leads to Brazos Bend State Park where I was a volunteer telescope operator at the George Observatory.

You may ask why I did not use that telescope to view the comet.  It is that the public viewing program at “The George” was suspended late last year for renovations to the observatory and museum facilities.  It was all set for a grand re-opening when the current disruption concerning the Communist Chinese Xi Jinping Virus began.   

My attempts at viewing the comet took place on mornings this past week when skies were allegedly clear.  None were successful – due mostly to the aforementioned urban skies. The path of the comet is from the southern extreme of the Solar System – crossing into the northern skies – where it is now found – and exiting back to the south.  Because it is closer to the Sun now, it can only be seen in the early morning.  Later this month it will appear in the evening sky just after sunset.  More on that later.

The diagram in Figure 1 shows the current positions of the comet and Earth.  Mercury and Venus are seen but not labeled.  I dotted the comet’s path when it occupies the southern part of the Solar System.  With a considerable imaginative effort (and taking into account the direction of Earth and the comet), you can understand why it only appears in the early morning sky now and will appear just after sunset later. 

Figure 1: Comet’s path through the Solar System. Orbits of Mercury and Venus are shown but not labeled.

Figure 2 is the updated light curve and shows the decline in brightness.  Since it has now passed its closest point to the Earth, we could expect it to dim – if it were not still approaching the Sun.  The Sun will illuminate the comet more – and heat it, which may induce another outburst of brightness.  

Or…it could fall apart and disappear.  No guarantees, you understand. 😉

The observations are being “handed over” from southern hemisphere observers to those in the north.  That gap near the 15th is a result.  There were single observations each day, but so far from the norm that I did not bother to plot them.

Figure 2. Predicted “distance only” brightness and actual observations

Hasta Luego – Steve