Tag: astronomy

Urban Astronomy

 

October 17, 2020 Introducing a new category

Despite this reporter’s career as a Geophysicist, he was an Astronomer by education.  These fields of study overlap when the Astronomy is “planetary”, since Geophysics involves the study of a particular planet to be found under the feet of a standing Astronomer.

  Your Humble narrator also has the habit of swimming – the only form of exercise he can manage to “stick to”.    If one can manage to show up at the pool early in the morning, a single-use swimming lane is to be obtained.  Large swimmers are particularly disadvantaged when “sharing” lanes – and said narrator is large. 

    Reporters are often instructed – by Editors – to refer to themselves in the third person (as above).  Since I am my own Editor here, I am now putting an end to that.

      If I can snag a lane in the outdoor pool, I am able to swim alone and in relative darkness, but even so there is considerable urban lighting with which to contend – not to mention the glaring lamps in the sides of the pool.  Nevertheless, the Astronomer/Swimmer takes note when there are visible stars and planets available for viewing.  

   A few months back, it happened that there were four planets visible from the outdoor swimming pool.  My natural tendency is to point things like this out perfect strangers.  However, some of the people around at this time of morning know me – by sight at least.  And we are all eccentric individuals, or we would not be swimming at 5 AM.  Since having four “Eyes Only” planets in the sky at once is a fairly rare thing, I pointed these out.  The average reaction was one of surprise.  They had no idea of what was over their heads.

The oldest Astronomer joke in the world is to promise to point out one more than the number of planets actually visible.  So, I promised five and pointed out four.  The punch line of this ancient bit of comedy relies on the audience to ask where the fifth one might be. Then the Astronomer replies,  “You’re standing on it!”.   Of course, no one asked about that fifth planet and the joke went flat.  Don’t you people have any curiosity?  Yes, it is an old joke, but none of them ever heard it before – because it is so old.

   Now, the interesting part about that stale humor – if you think about it – is the point it makes.  Specifically, that all those small round lights that this Swimmer is pointing out are actually massive worlds – a lot like the one we are standing on.  Some of them are stunningly larger, some smaller than our own planet.  Some are closer to – or farther from – the Sun.  There are places where “the world” is profoundly different from the “world” we experience.  With those thoughts, the human imagination is expanded beyond the mundane existence of day-to-day life.

  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 paragraph.  So, at this point, I know my audience.  😉

Some description of how far apart objects in the sky is needed, and “degrees” are another unfamiliar subject for Urbanites.  Extend your thumb and put it at arm’s-length and close one eye.  Now your thumb covers one degree of sky.  For Apollo 13 fans – this is why Jim Lovell was making the same weird gestures.  He was, in fact measuring the sky in degrees.

  Most Sophisticated Urbanites are also unfamiliar with compass directions.   The moon shows up pretty well, however.  So, I will use the moon to “landmark” where you Urbanites should look to find points of interest in the sky.  Those will be planets mostly, since at least four of same are bright enough to be seen in the City Glare.  The moon moves quickly across the starry sky, so pay attention to the dates and times. This first installment is for the night of October 22nd at 20:00 (8PM). 

Skymap from Heavens-Above website:  https://heavens-above.com/SkyChart2.aspx This link is calibrated from my patio. If you are near me, it will work for you. If not, you can change the location to your own house, with one of the links at left of the homepage.

At that date and time the moon will be near Jupiter and Saturn in the South-Southwestern sky.  Jupiter and Saturn are approaching a conjunction which will peak in December when the two planets will be within a tenth of one degree of each other – in the Earth’s sky, only.  They will actual be separated by about five Astronomical Units.  And – an AU is the distance from the Earth to the Sun (about 93,000,000 miles).

   All of my description, the thumb-and-one-eye-closed bit and the skychart are just illustrations.  This is Urban Astronomy – just look where the moon is!  😉

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 7/3/2020

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 5/19/2020

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

NEO 2020 JJ 5/04/20

Another Near Earth Object encounter.  This time with a unique announcement:

Figure 1.

Notice that 2020 JJ has an anomalous distance of encounter of zero AU.  It is rounded off, of course.  The managers of this source will be contacted to encourage more decimal places!  By other sources, I find the “miss” distance to be about 16,200 miles which is indeed less than 0.1 Lunar Distances.

This, again is worthy of a more detailed diagram with a better picture of the Earth (Thanks, NASA!).

The approaching asteroid did not pass across the celestial equator – where all the geosynchronous communication satellites are – but further to the South.

The JPL Small Body Database Browser, which is also the source for the “circle and arrows” diagrams you have seen on these pages, has undoubtedly given us a more accurate figure.  However, it does have some limitations, which are clearly explained in the website:

“This orbit viewer was implemented using two-body methods, and hence should not be used for determining accurate long-term trajectories (over several years or decades) or planetary encounter circumstances.”

https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2000%20CH59;old=0;orb=1;cov=0;log=0;cad=0#orb

The alert readers (most of you) will point out that “planetary encounter circumstances” is exactly what I am talking about.  That statement means that when asteroids get close to a planet, their mutual gravity has a significant effect that is not calculated in this utility.  So, that 16,200 miss distance is not keenly accurate and almost certainly too large.  Not only that, but it also means that the orbit after the near encounter will have been altered.  It will need to be recalculated and replaced in the database.

JPL has a utility for that, called the “Horizons system” and NASA has an organization to keep track of these things (and studies methods to avoid collisions) called the Planetary Defense Coordination Office.  That said, rocks this small (about 13 feet across) are not easily detected far in advance.  They are also less destructive should they fall to Earth.  This one was small compared to the Chelyabinsk meteor.

Comet Update 4/30/20

Comet 2020 F8 is now visible with “eyes only”.  But not from the Northern Hemisphere.  I hasten to explain that the “crosshairs” appearing (below) on the brighter stars are artifacts of the telescope construction – diffractions caused by the mounting bracket of the secondary mirror.

Figure 1:  Taken by Gerald Rhemann on April 27, 2020 @ Farm Tivoli, Namibia

This is when the comet was at about magnitude 6.3.  As of this writing, 2020 F8 is showing at magnitude 5.3.  You will recognize the graph below as my calculation of brightness change due to total distance (Sun/Comet/Earth) with the average daily observed magnitude.  I warned you that comets can’t be predicted with simple models like that and now you see what I meant.

Figure 2.  The “distance only” prediction and the observed (daily average) brightness

Again, the differences are due to eruptions of gas and dust, making a much more reflective target.  The comet now qualifies for “eyes only” visibility.  It is still something for which you would need to take a trip outside your sophisticated urban environment.  But don’t even bother because – except for my readers in the Southern Hemisphere – it is still below the southern horizon.  I am working on some sky charts for Lima, Peru. But that still requires a road trip to a dark sky.  There may be something for you city dwellers later.

Figure 3

Update May 5: In Lima, the comet is in the Eastern sky just before dawn (unfortunately looking right across the well-lit city) at about 25 degrees altitude. The sun will be rising soon so here is the standard warning: Do not look at or near the Sun with binoculars or a telescope! Blindness may result.

There is also a meteor shower this morning, coming out of the West East and streaking across toward the city ocean.* Also, look for Mars, Jupiter and Saturn together in the Southeast. There are conflicting weather reports. One says mostly clear. If that works, “Sigrid, te quito la bruma Limeña!”. Otherwise – same as usual.

*Doh!

Use the reply window below for questions. If you don’t see the reply window, click on the title at the top of the article to make it appear below.

Hasta Luego,

Steve

NEO Encounter April 28, 2020

   In 1979, Skylab – America’s first space station – was falling out of orbit and my sister called me – her space nerd brother – to worry about this thing that she feared would fall on her new baby.  I tried to explain that the Earth is so big and the Skylab so small (relatively speaking) that the chances were nil that any person on Earth would be anywhere near where it fell. 

I went on to point out that there are natural meteorites that fall to Earth constantly and they could amount to the equivalent of thousands of Skylabs every year.  She never worried about those!

After that, she was not just worried – more like terrified!

I have since learned to advise people that they are more likely to be hit by a train, bitten by a shark and struck by lightning – all at the same time – than to be struck by anything falling from the sky.  There is exactly one case of a person being hit by a meteorite.  The lady was badly bruised, but not fatally.

I told you that to blunt the effect of telling you the following:

Another Near Earth Object passed by the Earth on April 28th, 2020.  I have checked a couple of reliable sources and I can tell you that the nearest it came was about 29 thousand miles.  And that sounds like a lot, since the earth itself is only about 8000 miles in diameter,

However, the NEO does come into our “territory” since we have satellites orbiting the Earth.  You might think that satellites are only hundreds of miles above the Earth and that is where you are mistaken.  I decided that those little diagrams with circles and arrows are insufficient for this one.  Please see the diagram in Figure 1 for details.

As you see, the NEO this week is close enough to be of definite interest.  However, it passed to the South of Earth – nowhere near the “belt” of geosynchronous satellites over the equator and over twice as far as the “cloud” of GPS satellites.  And, of course nowhere near the Space Station.

The asteroid is about 60 feet across. Satellites are flimsy aluminum gadgets and would crumble before the NEO. But Space is big and satellites are small.

Hasta Luego,

Steve

https://www.nasa.gov/mission_pages/skylab

Near Earth Object 2020 HF5

April 27, 2020

Another Near Earth Asteroid has zoomed by while no one was looking on April 22nd.   It may surprise the readers to learn that these things are so common that I only consider the ones that pass as close as the Moon to be of interest.  This one was at 0.4 Lunar Distances or about 95,542 miles.

Figure 1

The culprit is 2020 HF5  – a small rock, as asteroids go – that is only 52 feet across.  These encounters are listed at https://spaceweather.com/  – just scroll down a bit to find a table.

The rock in question is very much is roughly the same size as an asteroid that exploded over  Челябинске in Russia on my 58th birthday.  (Feb 15, 2013) . The heat of re-entry, combined with the tremendous air pressure of its hyper-sonic trajectory caused it to explode at 12 to 15 miles above the surface.  

There was a Russian teacher – Yulia Karbysheva – about my age who, like me, had been trained in Civil Defense exercises in elementary school.  They taught us what to do in a nuclear attack. When the meteor lit up the sky, she had her students hide under the desks – as she (and I) had been trained to do.  When the asteroid exploded and the shock wave arrived, it shattered all the windows and sent shards of glass over the desks – with the students safely beneath same.  After almost a half century, that training finally paid off – for the students.  Unfortunately, she was so concerned with the fourth-graders that she remained standing and was seriously injured.  In all, about 112 people were hospitalized, mostly cuts from flying glass.  There were some cases of flash blindness and ultraviolet burns.  Don’t look at the flash!  I learned that instinctively as a welder.

Our more recent visitor was similar in size, but with only about 1/2 the relative velocity as that meteor and would have about the one fourth the explosive potential.  About 117 kilotons – 9 Hiroshima bombs equivalent.

What’s that?   Oh…it’s the town’s name – “Chelyabinsk”.

Hasta Luego,

Steve