Overhype much?

There has been quite a lot of news coverage suggesting that astronomer have, for the first time, discovered planets in another galaxy. It’s from a paper by Xinyu Dai and Eduardo Guerras called Probing Planets in Extragalactic Galaxies Using Quasar Microlensing.

It uses gravitational lensing, which is a consequence of Einstein’s Theory of General Relativity, which I discussed previously in this post. General Relativity proposes that objects with mass distort spacetime, which then manifests itself as gravity (i.e., objects with mass will fall towards each other in this curved spacetime). Light too is bent if it passes near massive bodies. Therefore, objects with mass can act as lenses, amplifying the light from more distant objects and, in some cases, producing multiple images of these objects.

Gravitational lensing has actually been used to detect planets in our galaxy for quite some time now. Known as microlensing, an example is shown in the figure on the right. If two stars happen to come into alignment (when viewed from the Earth) the nearer star can act as a lens, focusing some of the light from the more distant star, causing it to appear to get brighter. As they move closer and closer into alignment, the amplification increases, and then decreases again as they move apart.

However, if the nearer star (lens) happens to have a planetary companion, it can cause an additional amplification. This is the small blip, about 10 days after 31 July 2005 in the figure on the right, that lasts about a day. This can then be analysed to infer the properties of the planet. In this case, the planet is about 5.5 Earth masses and orbits about 2.6 times further from its star than the Earth is from the Sun.

What they’ve done in this recent paper is related, but somewhat different. In this case, the lensing is of a quasar (the active nucleus of a very distant galaxy) by a nearer galaxy. This event actually produces multiple images of the distant quasar. There also appears, however, to be some variability which they explain as being due to planets in the lens galaxy.

Now, this is certainly plausible. We know there are planets in our own galaxy, so it’s not really a surprise that there are planets in other galaxies. A problem I have, though, is that even if this is a plausible explanation, it seems to be quite a long way from being an actual discovery (and, yes, they appear to use discover in their own press release). They’re also not really discovering specific planets, they’re suggesting that there has to be a population of planets, in addition to a population of brown dwarfs (stellar objects that don’t ignite fusion in their cores), and a population of stars. There are quite a large number of parameters.

Also, these need to either be free-floating planets, or planets on very wide orbits around their parent stars; if they were too close to the star, the influence of the star would dominate over that of the planet. Again, this is certainly possible; we’re aware of free-floating planets in our own galaxy. However, their analysis suggests something like 2000 planets, with masses between that of the Moon and Jupiter, per star. If we assume that planets typically form in discs around stars, then this would seem to be a rather large number of planets per star. Yes, some stars will have formed planets and then died, but I don’t think this is enough to explain these numbers.

Observations in our own galaxy do suggest that most stars host a planet of some kind, and that mult-planet systems are indeed reasonably common. However, we don’t really expect there to be thousands of planets per star. Also, only a fraction of those planets that form in a disc are likely to be ejected – maybe 20-40%. As a rough estimate, we might expect there to be a similar number of free-floating planets, as bound planets – something like a few per star.

Okay, so maybe my title is a little unfair, and maybe I’m missing something. I do think it’s great when people try to find innovative ways to explain observations. However, I also think it’s important to not make claims that are stronger than are warranted (may have found evidence for, rather than discovered). Maybe the only plausible explanation for these observations really is that there are thousands of free-floating planets per star in this galaxy, but I think I’m going to need a bit more convincing. To be clear, I have no real doubt that there are planets in this galaxy (would be very surprised if there weren’t) I’m just not convinced that this analysis has really demonstrated their existence.

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31 Responses to Overhype much?

  1. Michael 2 says:

    “may have found evidence for, rather than discovered”

    I suggest something in between; they definitely found something. Its the conclusion that gets the uncertainty.

    When I read “may have found” it becomes equally plausible that they may have found nothing.

    “An aquarium accident may have given this crayfish the DNA to take over the world”

    Or not. Makes it seem like Science News is filled with guesswork. http://www.sciencemag.org/news/2018/02/aquarium-accident-may-have-given-crayfish-dna-take-over-world

  2. Jon Kirwan says:

    Well, this is certainly a good way to push for added funding and/or scheduling access to scarce resources in a difficult, competitive environment for such funding and access. Make it sound like you discovered a planet in another galaxy!!

    No shock there. Just good marketing and attention-grabbing practice. Maybe they will secure themselves some access to JWST in late 2019 once it reaches L2! Can’t fault them for trying.

    Might make the team seem a little “grabby” to everyone else, though. 😉

  3. Everett F Sargent says:

    I’m wondering who the ‘so called’ peer reviewers (and the process) were for this paper.

    I’m guessing Ben T. Here, Don T. Hat, T. Wice, E. Ven and Neve R. A. Gain. 😉

  4. Everett F Sargent says:


    ArXiv has a “Draft version February 2, 2018”

    Click to access 1802.00049.pdf

    I’m both too dumb and also out of meaningful clock time, but is this closer to five sigma or the inverse of five sigma certainty?

  5. Eli Rabett says:

    Once more Eli points to the wisdom of Ms. Rabett who speculates that they may have actually found the Big Ball of Strings and Eli repeats his recommendation that all grant applications have to be accompanied by press releases from the previous cycle so that reviewers can evaluate the noise.

    Cripes, this is getting to be deja vu all over again


  6. Eli Rabett says:

    Or to quote (with changes) from Peter Woit

    This is following the usual pattern: published article includes only minor references to string theory, since no referee would allow the author to claim that this was a “test of string theory” (since it isn’t). On publication of the article, the author has their university press office issue a press release about how they have discovered a “test of string theory” (I don’t believe in claims that university press offices issue press releases about their faculty’s work without the faculty member’s agreement). The press release then gets spread through various media outlets, often with the outrageousness of the claims increasing as it spreads. Finally, you end up with lots of news stories

  7. Mitch says:

    Throw in the other factor here—NSF keeps demanding “transformational science”, in other words a breakthrough a minute (for no dollars). The funding agency is putting pressure onto PI’s to hyperextend their accomplishments.

  8. Mitch,
    Indeed, it is an environment that encourages people to make their research appear groundbreaking and transformational and doesn’t really reward good solid research that simple helps us to improve our basic understanding.

  9. One of Carl Sagan’s better moments was the discovery of caustic focusing of light from stars occulted by the thin atmospere of Mars

  10. An under-hyped discovery was by amateur radio-astronomer Scott Tilley, who extracted a signal from a long-thought dormant NASA satellite called the Imager for Magnetopause-to-Aurora Global Exploration. NASA confirmed the finding after believing the satellite was dead for over 10 years.

  11. Steven Mosher says:

    Speaking of overhype

    I suppose now ya’ll might reconsider my claim that 8.5 AINT GUNNA HAPPEN


  12. Steven,
    I don’t think people are claiming that RCP8.5 will happen (I certainly don’t). I’m simply not convinced that we can yet rule it out with high confidence (as a concentration pathway, at least).

  13. Everett F Sargent says:


    See (Figure 2. SSP-RCP scenario matrix illustrating ScenarioMIP simulations) …
    The Scenario Model Intercomparison Project (ScenarioMIP) for CMIP6

    Click to access gmd-9-3461-2016.pdf

    SSR5-RCP8.5 is the only RCP8.5 scenario out of a total of twenty five scenarios.
    (I’d need to download some time series from the CMIP6 website or search elsewhere for further FF details for this scenario, if it’s still heavily coal dominated, then I would agree with you, in that this scenario has (or should have) a very low p-value).

    Oh, and thanks for the link, there are several good references (that I probably don’t have the time to fully explore). 😦

  14. Everett F Sargent says:


    OK found one (so far) for SSP5 (includes FF breakdown in Fig. 4) …
    Fossil-fueled development (SSP5): An energy and resource intensive scenario for the 21st century

    Looks like ~50% coal + ~10% oil + ~20% gas (almost entirely FF’s). It’s like humanity got a frontal lobotomy.

  15. John Carpenter says:

    Sounds like you’re lukewarm to this paper. Lol

  16. verytallguy says:

    Steven, your cite doesn’t support your strong conclusions. From the article:

    There are no crystal balls, particularly on the timelines which govern climate-economic models. It’s not impossible that societies will return to coal in the way they are now fleeing it, particularly if population growth continues apace and technological aspirations fall short. “Humans are very hungry for energy,” van Ruijven said. If renewables hit a wall, oil and gas dry up and we punt forever on climate change, “we might well be excavating all the coal we can put our hands on.”

    That’s pretty much a paraphrase of the challenge you got here the last time you raised this.

    Your caps make you seem a little, well, obsessive on your hobby horse.

  17. Steven Mosher says:

    “Fascinating figure.
    Most climate literature on worst case scenarios (RCP8.5), which may not be technically feasible. RCP4.5 is popular as it is a low, but feasible pathway (more likely than RCP2.6, hence easier to justify computer time).”

    Glenn Peters.

    Note Glenn’s comment about compute time

    “If renewables hit a wall, oil and gas dry up and we punt forever on climate change, “we might well be excavating all the coal we can put our hands on.”

    IF Monkeys, and If Unicorns, and IF we go nuts, then yes.

    like I said. Not gunna happen

    If you look at the number of papers written on 8.5 its clear that too much time and energy is being spent on slim to none chance scenarios. Running 8.5 AGAIN will not teach uou a single thing you dont already known. Wont give you one more insight into policy. it will provide exactly Zero information and consume cpu time.

    In a nutshell.
    1. 8.5 is an improbable scenario.
    2. We have already run it and ;learned everything one needs to learn from a policy viewpoint.
    3. There is no open science question it seeks to answer.
    4. Every year that goes by 8.5 becomes more improbable, at some point even you guys have to
    admit that it is a waste of precious compute research. What is your line, what would convince
    you that it is so improbable that the cost of computing it was not justified.

  18. Steven Mosher says:

    “Looks like ~50% coal + ~10% oil + ~20% gas (almost entirely FF’s). It’s like humanity got a frontal lobotomy.”

    ““If renewables hit a wall, oil and gas dry up and we punt forever on climate change, “we might well be excavating all the coal we can put our hands on.”

    Yes. In my argument on this I said that 8.5 requires us to go nuts. The one scientist they dredged up to justify 8.5 says the same thing, but calls it punting

    why not study a scenario where we decide to spend trillions of dollars to suck c02 out of the air?
    I mean if going nuts is ok to waste compuet time on, then lets study other scenarios where
    people go nuts.

    Here’s a thought. ya’ll should do some science and write a paper showing how probable 8.5 is
    and explain why you think we will go nuts

  19. verytallguy says:


    Before resorting to all caps again, you might like to consider why RCP8.5 is used in simulations (hint: it’s not necessarily because it’s likely).

    From a policy perspective, it’s arguable that we’ve already learned all we need to know on any of the scenarios.

  20. Joshua says:

    John Carpenter –

    How are you? Nice to see you here.

    Sounds like you’re lukewarm to this paper. Lol

    Are you saying that Anders is arguing that we should only consider a politically driven truncation of the range range of possible outcomes when planning for future outcomes?

  21. BBD says:


    Making a huge, unwarranted fuss about RCP8.5 could be perceived as fomenting yet another fake controversy intended to cast doubt on the integrity of climate science etc.

    If I inadvertently stirred up a fake controversy, I’d be hugely embarrassed.

  22. John Carpenter says:

    Hi Joshua,

    I’m not saying that. I’m also observing what Mosher is pointing out. What Mitch is pointing out and ATTP agrees with. You gotta make headlines to get funding. Now where else have we heard that? Hype and worst case sells.

    I love me some good irony

  23. Willard says:

    Speaking of irony, one has to appreciate our luckwarm visitors focusing their concerns on climate projections when the name of the game is energy:

    – The 2°C Scenario (2DS) is the main focus of Energy Technology Perspectives. The 2DS lays out an energy system deployment pathway and an emissions trajectory consistent with at least a 50% chance of limiting the average global temperature increase to 2°C. The 2DS limits the total remaining cumulative energy-related CO2 emissions between 2015 and 2100 to 1 000 GtCO2. The 2DS reduces CO2 emissions (including emissions from fuel combustion and process and feedstock emissions in industry) by almost 60% by 2050 (compared with 2013), with carbon emissions being projected to decline after 2050 until carbon neutrality is reached.

    – The 4°C Scenario (4DS) takes into account recent pledges by countries to limit emissions and improve energy efficiency, which help limit the long-term temperature increase to 4°C. In many respects the 4DS is already an ambitious scenario, requiring significant changes in policy and technologies. Moreover, capping the long-term temperature increase at 4°C requires significant additional cuts in emissions in the period after 2050.

    – The 6°C Scenario (6DS) is largely an extension of current trends. Primary energy demand and CO2 emissions would grow by about 60% from 2013 to 2050, with about 1 700 GtCO2 of cumulative emissions. In the absence of efforts to stabilise the atmospheric concentration of GHGs, the average global temperature rise above pre-industrial levels is projected to reach almost 5.5°C in the long term and almost 4°C by the end of this century.


  24. Here’s a blurb by one of the authors describing their just-published paper in the Journal of Geology : “Extraordinary Biomass-Burning Episode and Impact Winter Triggered by the Younger Dryas Cosmic Impact ∼12,800 Years Ago” by (27 co-authors)

    “The work posted in Two Parts below and published in the Journal of Geology is a masterpiece. Michelangelo’s sense of relief and accomplishment on the last brush stroke of the Sistine Chapel can compare to the satisfaction enjoyed by the lead authors of this paper. I will allow the history books to provide details, but please understand this publication has been under development for seven years. It took Mike only four years to paint the church ceiling — and the Pope had his back.

    The Burn Paper, like a masterpiece painting, is impossible for me to adequately summarize. Others will try and I sincerely wish them well.

    This paper is a woke moment. There will soon be others. The heavens have burned and they very nearly buried us. We are here to find out because it happened.”

  25. Willard says:


    The Burn Paper will humble the critics who have feasted on the uncertainties of science rather than celebrating and nurturing them. Dr. Jaqueline Gill comes to mind. Starting in 2009 this highly political young PhD in the Geosciences (with 42,000 tweets on all manner of issues) attacked the idea of evidence in lake sediments for North American continental wildfires. She made fun of the science and even belittled the peer-review process.

    After reading the Burn Paper perhaps Ms. Gill can find a location on Planet Earth where there is no evidence in lake sediment of intense fire at ~12,900 — but she will need to go to Antarctica or Greenland — and there be Platinum.


    Perhaps I should ask JaquelynG over the tweeter.

  26. John,

    I’m not saying that. I’m also observing what Mosher is pointing out. What Mitch is pointing out and ATTP agrees with. You gotta make headlines to get funding. Now where else have we heard that?

    Not quite what I’m ageeing with. Getting funded requires doing something that others think will have some kind of impact and will also require demonstation that you can do research that has impact. That doesn’t, however, excuse presenting results that are clearly overblown/over-hyped. Having said that, it’s not easy to simply define where the appropriate boundary should be.

  27. Willard says:

    Take a look at that:

    GeorgeH appreciated the plug:

  28. Willard says:

    Small world:

  29. Magma says:

    I don’t know anything about George Howard and I wasn’t bowled over by Firestone et al. (2007) when I read it five or six years ago, but a 50-year-old quote from Vince Lombardi seems relevant to Howard’s aggressively boastful blog post: “The next time you make it to the end zone, act like you’ve been there before.”

  30. Eli Rabett says:

    Steve Mosher

    Yes. In my argument on this I said that 8.5 requires us to go nuts. The one scientist they dredged up to justify 8.5 says the same thing, but calls it punting

    BREXIT, Trump, Kim

  31. Like Scott Tilley above, is this too much hype for an amateur astronomer?


    “Buso, a self-taught astronomer, had just witnessed the surge of light at the birth of a supernova — something no other human, not even a professional scientist, had seen”

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