Explosive brightening of approaching green comet – may be plainly visible in August

A comet that could become visible to the naked eye in August has just exploded in brightness. Amateur astronomer Michael Jäger‎ of Austria reports that Comet PANSTARRS (C/2017 S3) brightened 16-fold during the late hours of July 2nd, abruptly increasing in magnitude from +12 to +9. He took this picture of the comet’s expanding green atmosphere shortly after the outburst:

Image by Michael Jäger on July 2, 2018 @ Weißenkirchen Austria. Click to enlarge.

“The gas cloud around the comet’s nucleus is about 4 arc minutes wide,” says Jäger‎. That means the comet’s atmosphere is 260,000 km in diameter, almost twice as wide as the planet Jupiter. These dimensions make it a relatively easy target for backyard telescopes.

Comet PanSTARRS is falling toward the sun from the Oort cloud, a vast reservoir of fresh comets in the distant outer solar system. It has never visited the inner planets before, and, as a result, no one can say what will happen when its fragile ices are exposed to solar heat as it approaches the sun in August. Previous estimates of the comet’s brightness max out at magnitude +4–that is, barely visible to the unaided eye from dark-sky sites. Additional outbursts could boost its visibility even more.

The comet was discovered on Sept. 23, 2017, by the PanSTARRS telescope on the summit of the Haleakalā volcano in Maui. PanSTARRS’s primary mission is to detect near-Earth asteroids that threaten our planet. In the process,it sweeps up variable stars, supernovas, and comets like this one. With almost a year of data in hand, astronomers have been able to nail down the comet’s orbit. Click on the image to launch an interactive 3D visualization from JPL:

Comet PanSTARRS is approaching the sun on a hyperbolic orbit–a narrow open-ended path that will ultimately fling it back to the outer solar system. At perihelion (closest approach to the sun) on August 15-16, the comet will be inside the orbit of Mercury, blasted by solar radiation at point-blank range. What will happen then?

Via NASA Spaceweather.com

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Taylor Pohlman
July 4, 2018 4:37 pm

Hard to tell from the diagram what the inclination is to the planetary plane. Per the diagram it is briefly below. Mostly above one try and exit. Anybody have that info? I’m assuming the Oort Cloud is reasonablely aligned with the plane, but not sure of that either

Taylor Pohlman
Reply to  Taylor Pohlman
July 4, 2018 4:38 pm

‘On entry and exit’ – darn autocomplete

Lucius von Steinkaninchen
Reply to  Taylor Pohlman
July 4, 2018 5:01 pm

We don’t really now *that* much about the Oort Cloud, but it seems that it is spherical but with a higher concentration of objects roughly around the Ecliptic Plane.

Reply to  Lucius von Steinkaninchen
July 4, 2018 8:12 pm

Outer Oort Cloud, spherical (we think) and extends out to about 1 ly. Inner Oort Cloud sort extends from the end of the Kuiper Belt and blends into the outer cloud. Lots and lots of guesswork here. https://space-facts.com/oort-cloud/

Reply to  Taylor Pohlman
July 4, 2018 5:03 pm

The orbital elements, including the inclination, are below.
Epoch 2018 Aug. 30.0 TT = JDT 2458360.5
T 2018 Aug. 15.94470 TT MPCW
q 0.2084538 (2000.0) ……………..P…………………. Q
z -0.0004259 Peri. 255.88986 +0.21708526 -0.96396021
+/-0.0000042 Node 171.04060 +0.20807535 +0.19963280
e 1.0000888 Incl. 99.03829 -0.95371832 -0.17586207
From 116 observations 2017 Aug. 17-2018 May 21, mean residual 0″.4.

Reply to  jorgekafkazar
July 4, 2018 7:56 pm

Thanks jorge but which bit of that jumble answers the questions about inclination?

on a hyperbolic orbit–a narrow open-ended path that will ultimately fling it back to the outer solar system.

If it’s hyperbolic it’s not an “orbit”. It will not just “fling it back to the outer solar system.” , it will be ejected from the solar system. Sloppy science.

Reply to  Greg
July 4, 2018 8:03 pm

could this ejection trajectory be a result of an interaction with the hypothesised planet 9 ?

Bryan A
Reply to  Greg
July 4, 2018 9:19 pm

could this ejection trajectory be a result of an interaction with the hypothesised planet 9 ?

More than likely (99.99999999999+++%) Not.
The hypothetical planet 9, to be a planet by the Astronomical Society definition needs to be in the same plane of orbit as the other 8. This would make it virtually impossible to be what dislodged this comet from the Ort. It has a better chance of being dislodged by the much ballyhooed and equally nonexistent Planet X Nibiru.
The origin of this comet is far north of the Solar systems planetary orbital plane

richard verney
Reply to  Bryan A
July 5, 2018 12:51 am

Given the latest definition of planet, is it not the case that it is extremely unlikely that there is a planet 9?

The powers at be have almost certainly defined such a possibility out of existence, since it is almost certainly the case that if there is a large body in the outer regions of the solar system, and given the size and length of the orbit, that body could not have cleared debris and small objects from its path.

I suspect that if there is a large body (yet to be discovered) no matter its size, it is now likely to fall within the dwarf planet definition/category.

Johann Wundersamer
Reply to  Greg
July 4, 2018 8:11 pm


and which bit of that jumble answers the questions about inclination?

on a hyperbolic orbit–a narrow open-ended path that will ultimately fling it back to the outer solar system.

If the orbit is hyperbolic, it will not just “fling it back to the outer solar system.” , it will be ejected from the solar system.”

Shortsighted as always, Greg.

“hyperbolic orbit” means :

Yes, it will be ejected from the solar system.

No, it won’t make it back to the Oort Cloud.

We have a new intermittent approaching visitor.

Reply to  Greg
July 4, 2018 8:25 pm

I just checked the NASA article and the words “hyperbolic orbit” link to a WonkyPedia page entitled “hyperbolic trajectory”.

What has happened to NASA, they can not even get the science right when copying from WP ?!

Roy Everett
Reply to  Greg
July 5, 2018 1:11 am

Surely approximations like “elliptical”, “hyperbolic” and distinguishing between an “orbit” and a “trajectory” are not that useful when dealing with such loosely-bound objects in a more-than-two-body system over long timescales. While the trajectory of the comet over the coming months might usefully be *approximated* by an ellipse, parabola, or hyperbola, taken over a much longer period it will be a much more complicated shape with elements of chaos. It might return; it might escape; it might lurk.

Reply to  Roy Everett
July 5, 2018 11:08 am

Yes, there’s not much difference from where we stand.

Reply to  Greg
July 5, 2018 11:01 am

The number in boldface, 99.03829, following the word “Incl.” is the inclination. Note that the eccentricity, e, is estimated at slightly greater than one, so the orbit is hyperbolic. From our minuscule viewpoint, there isn’t that much difference between a huge ellipse, a hyperbola, or a parabola. One thing is certain: you won’t see this comet come back again.

D. J. Hawkins
Reply to  Taylor Pohlman
July 5, 2018 7:26 am

If you want the inclination, go to the JPL web site linked to the orbital illustration. You can zoom in, zoom out, and shake it all about. To answer your question directly, it’s about 75-80 degrees to the plane of the ecliptic.

July 4, 2018 4:40 pm

I’m just staggered, and very grateful, that planet earth isn’t assaulted by large space rocks regularly. I know we’re a small target, but there’s an awful lot of debris out there looking for a place to land.

Reply to  HotScot
July 4, 2018 8:45 pm

Part of the definition of a planet is that it clears it’s orbit. ie it either absorbs or ejects all other bodies in the zone of its orbit.

That all happened a long time ago.

Reply to  Greg
July 5, 2018 11:12 am

Our orbit still has 1080 mile diameter ball in it. Are we no longer a planet?

July 4, 2018 4:41 pm

Bye Bye Mars !! LOL

July 4, 2018 4:56 pm

I wonder just how visible it will be. Previous predictions for comets have been rather off (remember Kohotek?).

Clair Kiernan
Reply to  Tom Halla
July 4, 2018 5:09 pm

Kohotek was a disappointment, but I have fond memories of seeing a Hyakutake surprise.

Jean Meeus
Reply to  Clair Kiernan
July 4, 2018 11:34 pm


Reply to  Tom Halla
July 6, 2018 7:33 am

I saw Kohoutek with ordinary 10×50 binoculars. I was a young kid at the time age 10. It was VERY low to the horizon. But you are right, it was nothing like the predictions.

July 4, 2018 5:00 pm

” abruptly increasing in magnitude from +12 to +9.”
“Previous estimates of the comet’s brightness max out at magnitude +4–that is, barely visible to the unaided eye”

ok…this is very confusing
In the first it went from +12 lower to +9…..but says that makes it brighter….increases

…but then says lower is less bright…..+4 barely visible

Is that a typo? should it be … went from +9 to +12…and that made it brighter??

John West
Reply to  Latitude
July 4, 2018 5:28 pm

comment image

Reply to  Latitude
July 4, 2018 5:59 pm

I think it’s consistent. Got brighter (12 to 9) using a telescope, but still not so bright to the naked eye (I think). Check this out:


Reply to  philincalifornia
July 4, 2018 8:11 pm

I’m guessing that this is a logarithmic scale but how does a factor or 16 make a difference of 3?

Is it totally arbitrary scaling?

Reply to  Greg
July 5, 2018 2:01 am

Each magnitude means a factor of 2.5 in brightness, so an increase of 3 magnitudes is 2,5^3 = about 15 times brighter.
But magnitude 6 is just barely visible to the naked eye, so it’s still about 15 times too weak to be seen without a telescope.

Reply to  tty
July 6, 2018 6:00 am

The definition is 5 magnitudes is a factor of 10. See my other comment on the topic.

John Harmsworth
Reply to  Greg
July 5, 2018 3:28 pm

It’s Green, so uses Michael Mann Math.

Reply to  Latitude
July 4, 2018 6:15 pm

That’s one of the goofy things about astronomy. I think someone started a list with bright stars at the top and dimmer ones below, then wrote numbers from 1 to bigger on the way down.

A few stars of note and their magnitudes:

-1.47 Sirius (trails constellation Orion)
0.58 Betelgeuse (in Orion’s shoulder)
0.03 Vega (“summer triangle” star)
0.77 Altair (ditto)
1.25 Deneb (ditto)
1.97 Polaris (North Pole star)
-26 Sol (Our sun)

Reply to  Latitude
July 4, 2018 6:18 pm

A difference of 5 magnitudes was assigned a factor of 100.

Worth reading: https://www.skyandtelescope.com/astronomy-resources/the-stellar-magnitude-system/

They blame Hipparchus.

High Treason
July 4, 2018 5:28 pm

Will be a pretty hot view from Mercury. Something to look forward to in the cold of August in Australia. Almost as exciting as Nigel Farage visiting in September and possibly Donald Trump visiting in November.
Dare say the predictions of the exact viewing schedule for the comet will become more clear over the next few weeks as well as more accurate, unlike climate “science” which not only becomes more opaque with time, but also less accurate.

Joel O'Bryan
July 4, 2018 6:02 pm

Needs a better name.

Reply to  Joel O'Bryan
July 4, 2018 6:23 pm

Comets are named after their discoverer. When automated tools and orbiting observatories joined the fray, comets still get named after the discoverers.

Joel O'Bryan
Reply to  Ric Werme
July 4, 2018 6:26 pm

My point still stands.

Reply to  Joel O'Bryan
July 4, 2018 6:44 pm

Marketing by whom?

Perhaps you can start your own catalog and sell that.

Gunga Din
Reply to  Ric Werme
July 4, 2018 6:54 pm

“Green Lantern” marketed by DC Comics?

Joel O’Bryan
Reply to  Ric Werme
July 4, 2018 6:58 pm

The Weather Channel is on it no doubt.

If they can name a cold front, they can name an Oort Cloud body in the inner solar system.

Reply to  Joel O’Bryan
July 4, 2018 8:15 pm

Yes, but they must have gender neutral names with lots of “diversity”.

John Harmsworth
Reply to  Joel O'Bryan
July 5, 2018 3:29 pm

Comet “Green Doom”!

July 4, 2018 6:04 pm

Hey, wait a minute.
Are we sure this is a comet?
I recall that last year we were warned that the planet Nabiru(?) was on a collision course with earth; it apparently does this every 3,600 years. The reason we couldn’t see it at the time was because it was sneaking up on us from behind the sun.
And notice how it very sneakily increased its brightness?
Has it now thrown off its disguise, and is bearing down to have its wicked way with us?
Inquiring minds want to know.

High Treason
Reply to  William
July 4, 2018 6:09 pm

Remember the green colour. It does appear that green policy is what is likely to destroy our energy based civilization.
Perhaps the Nabiru legend is a metaphor for the destruction of humanity by the green monster.

Rainer Bensch
Reply to  William
July 5, 2018 4:01 am

very sneakily increased its brightness

They started the braking rockets. Like the mote in god’s eye.

July 4, 2018 6:50 pm

From http://www.aerith.net/comet/catalog/2017S3/2017S3.html :

Sky map – good for northern hemisphere viewers until the comet gets lost in the dawn light:


Expected and observed magnitude, looks like adjusted for the recent brightening, or perhaps curve fit to the observations:


July 4, 2018 6:52 pm

“Comet PanSTARRS is approaching the sun on a hyperbolic orbit–a narrow open-ended path that will ultimately fling it back to the outer solar system.”

Question: Wouldn’t a hyperbolic orbit ultimately cause the comet to leave the Solar System all together?

Reply to  RicDre
July 4, 2018 8:18 pm

Indeed and it’s not an “orbit” , it is a trajectory as I just commented above.

More sloppy science and half-assed press releases.

Jean Meeus
Reply to  Greg
July 4, 2018 11:48 pm

Yes, it is an orbit. You have circular orbits, elliptical orbits, parabolic orbits, and hyperbolic orbits.
Unfortunately, many authors use the word “orbit” with the meaning “revolution”. The orbit is a path, while revolution means motion along that path. For instance, some authors write that the planet Mercury makes 4 orbits per years. But Mercury has only ONE orbit, its orbit, which is an ellipse with an eccentricity of 0.206. In one year, the planet performs 4 revolutions on this orbit.

Reply to  RicDre
July 4, 2018 8:19 pm

Velocity also plays a part. The comet is not moving fast enough to be falling in from interstellar space, so the theory is it was perturbed from the outer Oort Cloud. It’s velocity will carry it back out (to a different region) but not beyond.

D. J. Hawkins
Reply to  LarryD
July 5, 2018 8:47 am

I thought parabolic and hyperbolic orbits were by their nature “one and done”. When it heads back out, it ain’t stopping.

Reply to  D. J. Hawkins
July 5, 2018 10:43 am

But as it moves back out of the Sun’s gravity well, it loses velocity (exchanging it for potential energy). When it gets back to the distance it fell in from, its outward velocity will drop to zero. There being a lot (in theory) of other object out there, we can’t predict its trajectory past that point.

Parabolic and hyperbolic “orbits” aren’t closed, but if an object doesn’t have solar escape velocity, it’s not getting outside of the Sun’s Hill Sphere.

John Harmsworth
Reply to  LarryD
July 5, 2018 3:32 pm

Makes sense! Thanks Larry!

Reply to  RicDre
July 4, 2018 10:18 pm

When the article treats a hypothetical entity such as the Oort Cloud as a Fact, its safe to assume that all other conjecture will be dealt with similarly.

I do love good science fiction, too bad references to global warming couldn’t have found their way into the narrative.

Reply to  AWG
July 4, 2018 11:48 pm

All entities are hypothetical.

What matters is how much they explain and how much the sensory data does not refute their existence

Reply to  AWG
July 5, 2018 7:45 am

Comets are not four-and-half billion-year-old icy leftovers of the early solar system.

Reply to  Robertvd
July 5, 2018 10:44 am

Argue your proposition.

Reply to  AWG
July 5, 2018 7:47 am

Prepare for a coronal mass ejection .

Dan Kurt
Reply to  Robertvd
July 5, 2018 8:50 am

Instead of a hint, why not say that the comet is electrically linked to the sun and that linkage caused the brightening?

Dan Kurt

Reply to  Dan Kurt
July 5, 2018 11:35 am

Like a fluorescent tube.

Peter Morris
July 4, 2018 10:15 pm

I hope another comet like Hale-Bopp comes through sometime. My daughter likes astronomy and I know she would go outside every night to check out something like that. I was living in the middle of Atlanta at the time and it was ridiculously visible, even with all the buildings and lights around. What happened to the Heaven’s Gate folks was sad, but the view of that comet was simply unforgettable.

Roger Collier
Reply to  Peter Morris
July 5, 2018 12:48 am

I have forgotten it.

Reply to  Roger Collier
July 6, 2018 6:04 am

Pity, it was a great comet. Possibly the best of your entire life.

Reply to  Ric Werme
July 7, 2018 4:20 pm

After much fanfare, the return of Halley was a complete disappointment. On the other hand, Hale-Bopp not only met expectations but easily exceeded them. It was an eerie spectacle–very hard to explain.


July 4, 2018 11:25 pm

It’s a harbinger of Doom

July 5, 2018 3:53 am

Now THIS is science I grok! Hopefully northeast wont be clouded over on those nights. Oh, snap, I be done jinxed it!

Any ideas what is causing the green coloration? Seems a bit odd.

John Harmsworth
Reply to  2hotel9
July 5, 2018 3:35 pm

It is an ablating shield to brake its entry into our system before it ejects its army of invading organisms down to Earth. I guess.

Reply to  John Harmsworth
July 5, 2018 5:33 pm

Hope they got the proper permits for use in our system, EPA will be on their a$$ otherwise.

July 5, 2018 6:49 am

Under the effect of solar radiation this artificial object is becoming active, that’s why it suddenly increased its brightness. This was all described by Arthur C. Clarke in Rendezvous with Rama. It is using the Sun’s gravity to increase its speed and steer its trajectory. We should remain very quiet in case it is reporting system activity back home. We should immediately cease every type of radiation that leaves the planet or risk undesired attention from potentially dangerous ETs. The precautionary principle demands it. Quickly, shut down everything! They are listening!

Reply to  Javier
July 5, 2018 10:40 am

right, better safe than sorry, shut it all down.

If we don’t shut it all down by … Friday at 3:00 am (NY time) … we will reach the tipping point of alien invasion.

Think of all the future generations (not just your grandchildren) of slaves to the alien overlords. It will be a small precautionary price to pay … shut it down for a few months.

John Harmsworth
Reply to  Javier
July 5, 2018 3:39 pm

They may just stop and ask if we saw a Oumuamua pass through recently

Dave Crosby
July 5, 2018 8:30 am

Hyperbolic does not always remain hyperbolic when tugged by planets.
Do your own thinking. SOME Comets DO come from outside the solar system.

John Harmsworth
Reply to  Dave Crosby
July 5, 2018 3:40 pm

It’s \green so hyberbole is expected.

Reply to  Dave Crosby
July 6, 2018 3:54 pm

From the orbital parameters up above, the eccentricity is just barely over 1, 1.0000888. This means that its exit and entry speed to this visit to the center of the solar system was very nearly zero (insert some hand waving there, it’s not quite what I should say) and that it wouldn’t take much of a perturbation to direct it inward. (Or outward! I think we shed more comets out of the solar system than we direct inward.)

Oumuamua has an eccentricity 1.196, surprisingly low perhaps, but I’d need to think about it some to determine its speed outside the solar system. The semi-major axis plays a big role too. Perhaps Jean Meeus already has.

https://voyager.jpl.nasa.gov/frequently-asked-questions/fast-facts/ says:

Voyager 1 is escaping the solar system at a speed of about 3.6 AU per year.
Voyager 2 is escaping the solar system at a speed of about 3.3 AU per year.

https://voyager.jpl.nasa.gov/mission/science/hyperbolic-orbital-elements/ says
Voyager 1: a = -480,926,000 km, e = 3.724716
Voyager 2: a = -601,124,000 km, e = 6.284578

Those eccentricities seem awfully high to me. I definitely need to review conic section theory.

Dr. Strangelove
July 6, 2018 4:52 am

Carolyn Shoemaker – one of the best astronomers today. Co-discoverer of Comet Shoemaker-Levy, she held the record for most comets discovered by any person. Discovered 32 comets, 377 minor planets, over 800 asteroids

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