Note : For context, first read my article Oumuamua Shape Debunked or my twitter thread : Why 1:10 ratio for Oumuamua is absolute rubbish !
Date : June, 2018
(last updated in June, 2020)
The
lightcurve method used to predict the shape of Oumuamua has a very poor
track record at predicting shapes of asteroids & comets.
Spectacular Failure - 1
(Comet 67P, 2014)
The most spectacular failure of this method was in the shape prediction of the famous Comet 67P. This comet was the most closely studied ever, among asteroids/comets & a European spacecraft Rosetta had orbited it & even landed a probe on it (Philae).
Estimate : Watch its very wrong shape prediction below :
https://www.aanda.org/articles/aa/full_html/2012/12/aa20116-12/aa20116-12.html#abs (see Fig.5)
Reality : Peanut Shape / Rubber Ducky
http://news.nationalgeographic.com/2015/09/150928-comet-67p-rubber-duck-shape-space-science/
Estimate vs. Reality
Totally wrong shape prediction of Comet 67P
https://www.spacetelescope.org/images/heic0310a/
Spectacular Failure - 2
(Asteroid 69230 Hermes, 2003)
The lightcurve method could not even detect that it is a binary asteroid. Instead, it predicted Hermes to be a single body, with a spherical shape -
https://en.m.wikipedia.org/wiki/69230_Hermes (see under physical characteristics)
Estimate vs. Reality
Credit : Arecibo Radar Observatory
When the lightcurve method does not even know what it is looking at (whether 1 object or 2), then how can it predict the shape of it ? To give a doctor analogy, without even a proper diagnosis (detecting if the asteroid is 1 object or multiple), how can scientists hope to find a cure (of predicting the shape) ? They are just guessing. It is NOT science.
Here is a crime analogy - imagine a bank security guard telling the cops that he was robbed by a really fat man, while the CCTV footage later shows the robbers to be 2 thin men ! Its a BIG difference & changes EVERYTHING ! It means, the guard's story has no credibility left !
Spectacular Failure - 3
(Asteroid Ryugu, 2018)
Estimate : Using the same lightcurve method, scientists got the shape prediction of asteroid Ryugu also wrong, despite all the space expertise, math, science, multiple observations and 9 years of team study, across multiple countries ! Their prediction : spherical shape
http://www.isas.jaxa.jp/en/topics/000566.html
https://arxiv.org/pdf/1804.03734.pdf (April 2018, page 9)
Reality - Asteroid Ryugu's shape is a square / rhombus / diamond / spinning top (as described in media. none described it as spherical)
https://www.msn.com/en-us/video/mma/japans-hayabusa2-spacecraft-arrives-at-diamond-shaped-asteroid-ryugu/vp-AAzfkqa
Estimate vs. Reality
Here is a news extract, showing an indirect admission of failure from the Japanese space agency, JAXA itself : "The distinctive diamond shape of Ryugu initially took the team by surprise, despite its years of careful planning."
Why was the JAXA team surprised ? Bcos they were sure that their predicted shape model was correct. But even after having 9 years of data from several sources, they still got it wrong. While JAXA's achievement in asteroid exploration is fantastic, my focus here is on lightcurve based shape estimation only.
In the case of hastily measured data of an extremely fast moving & distant Oumuamua, there is all the more reason to be skeptical of the shape prediction, and the original team of scientists themselves should have tilted towards a less sensational claim. But sensationalism took over genuine science & polluted the minds of everyone, right from the scientific community to the masses, with a fantasy visual that is now hard to erase. It has captured everybody's imagination & the shape is deeply etched into their minds now.
Spectacular Failure - 4
(Arrokoth, 2018)
In the latest case, the lightcurve method totally failed to predict the very elongated shape of Arrokoth / Ultima Thule (2014 MU69).
GIF credit : Vinny Chirayil
Photo credit : NASA / Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute
Lightcurve study of Ultima Thule with the Hubble space telescope :
https://arxiv.org/abs/1812.04758 - Dec 12, 2018
https://arxiv.org/ftp/arxiv/papers/1812/1812.04758.pdf
Extract - "The mean variation in our data is 0.15 magnitudes which suggests that MU69 is either nearly SPHERICAL (a:b axis ratio of 1:1.15), or its pole vector is pointed near the line of sight to Earth ... We report with CONFIDENCE that MU69 is not rapidly rotating and (not) highly elongated (which we define as a lightcurve amplitude greater than or equal to 0.5 magnitude)."
The confident claim of MU69 not being highly elongated (based on lightcurve analysis) has already been royally debunked by New Horizons spacecraft itself ! Ultima Thule has an axis ratio just under 1 : 2, which is considered very elongated. 1 : 3 is the maximum ratio, for which we have photographic evidence of. Also, the above definition / understanding of "highly elongated" is seriously flawed bcos Saturn's moon iapetus proves that the lightcurve amplitude can go up as high as 2.12 magnitudes (4.24 times greater than 0.5) & still be spherical in shape.
In the absence of stellar occultation data (below), scientists would have clearly predicted a spherical shape for Ultima Thule & would have been proven very wrong. The lightcurve method routinely assumes uniform albedo, equatorial view, smooth surface & a convex shape, with no self shadowing over large areas. Due to the last point, it failed miserably in predicting Comet 67P's shape.
The basic assumption of the lightcurve method is that brightness variations are due to shape only, which is horribly wrong, as proven repeatedly.
The basic assumption of the lightcurve method is that brightness variations are due to shape only, which is horribly wrong, as proven repeatedly.
Credit : NASA/JHUAPL/SwRI/Alex Parker
New Horizons scientists puzzled by lack of a 'light curve' from their Kuiper Belt flyby target - Dec 20, 2018
http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20181220
"Among its approach observations over the past 3 months (Sept-Nov, 2018), the spacecraft had been taking hundreds of images to measure Ultima's brightness and how it varies as the object rotates. Even though scientists determined in 2017 that the Kuiper Belt object isn't shaped like a sphere – that it is probably elongated or maybe even two objects – they haven't seen the repeated pulsations in brightness that they'd expect from a rotating object of that shape."
Why were they puzzled ? Bcos despite the team knowing that the pole axis could be facing Earth / New Horizons, as early as 2017 (Benecchi et al 2017) they still expected some brightness variation, which did not happen & the lightcurve remained flat. So, the pole axis direction is just a lame excuse for the failure of lightcurve method & clearly, a slow 15+ hour rotation was also not responsible for it.
Lightcurve analysis from both Hubble Space Telescope (2016) & New Horizons spacecraft (2018) failed to predict an elongated shape, despite occultation data of 2017 strongly suggesting that the object is elongated / contact binary / binary. So, I look at this as further proof of the unreliability of lightcurve based shape estimations.
http://pluto.jhuapl.edu/News-Center/News-Article.php?page=20181220
"Among its approach observations over the past 3 months (Sept-Nov, 2018), the spacecraft had been taking hundreds of images to measure Ultima's brightness and how it varies as the object rotates. Even though scientists determined in 2017 that the Kuiper Belt object isn't shaped like a sphere – that it is probably elongated or maybe even two objects – they haven't seen the repeated pulsations in brightness that they'd expect from a rotating object of that shape."
Why were they puzzled ? Bcos despite the team knowing that the pole axis could be facing Earth / New Horizons, as early as 2017 (Benecchi et al 2017) they still expected some brightness variation, which did not happen & the lightcurve remained flat. So, the pole axis direction is just a lame excuse for the failure of lightcurve method & clearly, a slow 15+ hour rotation was also not responsible for it.
Lightcurve analysis from both Hubble Space Telescope (2016) & New Horizons spacecraft (2018) failed to predict an elongated shape, despite occultation data of 2017 strongly suggesting that the object is elongated / contact binary / binary. So, I look at this as further proof of the unreliability of lightcurve based shape estimations.
Spectacular Failure - 5
(Binary comet 288P, 2016)
Lightcurve analysis failed to identify 288P as a binary comet & predicted it to be a single object of 2.6 km diameter, as per this paper - http://www2.ess.ucla.edu/~jewitt/papers/2016/AJW16.pdf
Credit : NASA, ESA, and J. DePasquale and Z. Levay (STScI)
The paper, did briefly consider the possibility of it being a binary object, to explain certain anomalies, but the abstract & conclusion of the paper finally predicted 1 object, not 2.
In 2016, Hubble telescope confirmed its binary status.
Spectacular Failure - 6
(Binary asteroid 617 Patroclus, 2001)
Lightcurve analysis failed to identify it as a binary asteroid. Instead, a brightness amplitude of less than 0.1 mag, was strongly suggestive of a single body of spherical shape. Wikipedia states :
"Since 1989, several rotational lightcurves of Patroclus have been obtained from photometric observations. Analysis of the best rated lightcurves gave a rotation period between 102.8 and 103.5 hours with a brightness amplitude of less than 0.1 magnitude"
Note : Since binary status was confirmed as early as 2001, I could not find a paper before that time, which specifically claimed its shape to be spherical. But low amplitude = spherical is an accepted thing in the scientific community. To understand the significance of failures 5 & 6, read failure 2 again.
Summary
Basic problem of the lightcurve method : BLINDNESS
- it could not identify whether it is looking at 1 object or 2 (in the case of asteroid Hermes, comet 288P & asteroid Patroclus)
- it could not identify Arrokoth as an elongated body
- even when body is not elongated, it predicted wrong shapes for asteroid Ryugu & comet 67P.
Predicting the shape of an object by looking at a tiny dot of fluctuating light (lightcurve analysis) is NOT genuine science !
It is just a guessing game, not very different from seeing aliens, pyramids, fossils, crashed spacecrafts etc, on pictures of Martian terrain, due to shadows creating certain patterns. Sure, it is fun & entertaining but a light flicker cannot possibly tell you the shape of the object causing it.
Those who naively believe that lightcurve based shape prediction is a science, need to furnish 6 examples of successful & verified shape predictions & also give an intelligent explanation for the 6 failures listed above. I hope some competent scientist on Earth can accept my challenge. Good luck :-)
Want to see more examples ? My Twitter thread has documented 17 failures of the lightcurve inversion method. It is a pseudoscience.
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