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The 'megacomet' Bernardinelli-Bernstein is the find of a decade (space.com)
334 points by wglb 38 days ago | hide | past | favorite | 68 comments

For the HN crowd, it may be especially interesting to note that this was pretty much a software discovery.

The dataset here was DES, the Dark Energy Survey. It’s a big dataset that has been around for a few years, and probably thousands of astronomers have worked with it. But its just a huge amount of data, covering a lot of the sky.

Bernardinelli’s software discovered a blip in that big pile of data. He crunched through the dataset and got a weird answer for the size of the solar system (basically - its a bit more complicated). Almost everyone, when they get something like that, tweaks the parameters of their analysis code: “I must have the threshold for object detection set too low.” The real discovery comes from trusting the software and pursuing the question.

This is a lot like software developers and their persistence. When your production service has a mysterious error in the logs, do you shrug and say “well, probably some transient network bug, it won’t matter” or do you dig in to understand what’s going on? Both approaches are reasonable, and it takes a balance of pragmatism and curiosity to be effective.

But anyway - there is an increasing demand for applying rigorous software engineering techniques to astronomical datasets. A problem that we are facing in astronomy software today is that the datasets have gotten way too large for astronomers to just pull up images in DS9 and eyeball stuff to make sure it’s right, so they need software that is much more trustworthy and bug-free than before.


Edit to add: DES data is completely public access: https://www.darkenergysurvey.org/the-des-project/data-access...

I love this point, and I have to go on a tangent on this:

> This is a lot like software developers and their persistence. When your production service has a mysterious error in the logs, do you shrug and say “well, probably some transient network bug, it won’t matter” or do you dig in to understand what’s going on? Both approaches are reasonable, and it takes a balance of pragmatism and curiosity to be effective.

I find that it really depends on how harried I am. Am I (or someone on my team) able to dedicate time to this issue, or do we have other higher priority concerns?

Every single time I can think of where we've had a "that's weird", it was a bug in the software. But it would take days to weeks for someone find the root cause (these were 1 in 100,000 race conditions), and we just can't afford to dedicate that amount of time to each.

So we have to pick our battles.

When the system is the Solar System, or the human nervous system, I say society has an ROI worth multiple PhDs to invest - but for an ad service that is likely to be completely replaced in a decade - yeah it's a lower ROI

But this raises the interesting (to me) question - almost every enterprise I know operates at the "harried" level - no one is so well funded they can saunter around

But science is basically saying "we trust you to find something worthwhile. Go saunter"

Maybe it's all about trust

There's plenty of sauntering in industry. Especially enterprise. "Enterprise" is notorious for not actually getting anything done, even though many of the individuals may feel stressed most of the time.

> "Enterprise" is notorious for not actually getting anything done, even though many of the individuals may feel stressed most of the time.

Enterprise is also way more driven by personal egos and certainties about being right. I doubt too many scientists would say "I'm going to reform the department, let's throw away the last 5 years of work and start again" – but decisions like that are commonplace in enterprise software.

> But science is basically saying "we trust you to find something worthwhile. Go saunter"

Not... quite.

Typically, scientist in academia are underfunded and overloaded with teaching and management duties. The way to get round to actual research is to hire phd students / postdocs. But there is no institutional funding, so you have to write a grant proposal. Since every academic is in the same boat, project calls are swamped with proposals and can only funds 10-20%. Since you want to get funding, you create a very clear project proposal with detailed timeline of expected publications. Because funders don't award mediocrity, your proposal is ambitious in this.

Now if you get the funding, you suddenly have a significant, detailed, ambitious research obligation to fulfil for the next #PhD years. You get to do research, but there's not much leeway.

No project funding? Here are stacks of committee work and teaching load. Oh, but we do expect you to keep publishing actively. Maybe make time on the evenings and weekends for research?

All in all, not really "go saunter".

> When your production service has a mysterious error in the logs

...such as a 75 cent accounting discrepancy? ;)

Please say more. How does a software engineer with a data engineering background and interest in astronomical phenomena learn about/start contributing to this area?

There is huge need for these skills in astronomy, but it can be tricky to find the right way to plug in.

There is plenty of opportunity to contribute to open-source —-astropy is one of the most active projects, as a starting point.

Deeper (volunteer) engagement probably requires finding a willing scientist to plug you in to a project. That can be tricky get going and to make mutually beneficial.

There are full time research software engineer positions—these will pay less than industry, of course; for some folks the subject matter and environment make that trade worthwhile.

No option sans degree, I assume? Or at least reasonable compensation while pursuing one.

Most of such jobs pay peanuts (relatively speaking). Academia is something to consider as a hobby or after you retire.

I've always wondered that and would probably do it for free, but my guess is that you run into the problem that all those gigs are reserved for grad students.

I do remember seeing a website that attempted to connect SW engineers willing to volunteer with scientists but I think that effort died out. Not a bad idea.

One of the most exciting phrases uttered in Science isn't "Eureka!" but rather

> "'This is weird — what is this thing?'"

John Ringo's Live Free or Die starts with a nice explanation:

“It is said that in science the greatest changes come about when some researcher says "Hmmm. That's odd." The same can be said for relationships: "That's not my shade of lipstick . . ."—warfare: "That's an odd dust cloud . . ." Etc.”

--Fires in California: "That's a strange cloud..."

Not making it up, this is exactly what we thought when the Oakland Hills fire of 1991 started. Our confusion was short-lived, I'm sad to say.

Today at work: "What's that smell?" after a quick look around "There's a bit of smoke coming off that transformer." Bigger problem averted.

There is very little substitute for spending lots of time in your lab, so that you notice the tiny shifts in mechanical sounds that indicate a change in the health of an instrument.

Same thing for me. I was having brunch in Pacifica and when I headed back to San Francisco, I saw this weird cloud where it shouldn't be. It was an otherwise clear day and it was blowing backwards, towards the ocean, due to whatever the Northern California equivalent of a Santa Ana wind is.

I think they're the Diablo winds in the Bay area?

Unfortunately the principle does not hold up for software development. If people made discoveries every time they encountered some strange code, we'd have The Matrix running in no time.

You think that's air you're breathing now?

Software is “This could be better…”

Perhaps we did ;-)

Such a great series. Word is he's working on book 4, but motivation is low. Can't say I blame him, he has a large body of work...which is also part of the problem; too many projects.

Or: "How on earth could this code possibly work?"

Thats the worst. The moment the problem flips from "whats wrong with this code?" to "Why does this even work?" and you learn how little you really know.

This is super cool. I studied comets for a while when I was in academia, and my favorite was one called Humason [0]. There are other great photos of it, some in google images, though the ones I had in the research lab in a a few books about comets were even more surprising. It had a very odd tail appearance because the comet tail is primarily created by an interaction with the solar wind / magnetic field, and at distances far from the Sun, that field is much weaker, so the tail becomes less straight, and this effect is even more pronounced when the comet is very large, as smaller comets just don't have an easy to detect visible tail from such great distances from Earth.

Humason is less than half the size of this comet and is considered abnormally large.

[0] https://en.wikipedia.org/wiki/Comet_Humason

Wikipedia link for those who want more detail: https://en.wikipedia.org/wiki/C/2014_UN271_(Bernardinelli-Be...

The important bit:

> It will make its closest approach to Earth around 5 April 2031 at a distance of 10.11 AU

The sad bit:

> Once at perihelion, the comet is not expected to get brighter than Pluto (mag 13–16)... Even if it reaches the magnitude of Pluto, it will require about a 200 mm telescope to be visually seen

For reference, 10 AU is the distance of Saturn's orbit, that's why so dim, it's really not coming near the sun at all.

For those more familiar with photography than astronomy, 200mm referrers to the aperture of the telescope, not the focal length. This is a telescope roughly 8 inches in diameter.

If you're looking to see it, Orion's XT8 would be a great starting telescope with aperture enough to see the comet

I would emphasize that 8 inches is the point at which it becomes possible to see a 14th magnitude object. This requires a very dark sky, excellent weather, and possibly averted viewing.[1] Pluto is mag 14.4 right now and Celestron describes observing it as "the ultimate challenge". https://www.celestron.com/blogs/knowledgebase/the-ultimate-g... They recommend a telescope of 11 inches. (Though they do sell telescopes...)

Also note that the XT8 is a manual, non-motorized scope, so you'll need to find Pluto by hand, navigating from neighboring stars. This can be unexpectedly difficult. The sky is big!

And just to be really annoying, to address people who have never looked through a telescope before: an amateur telescope will give you the ability to see the comet, but it won't look like a photograph from Hubble. It'll just be a dim white dot. If you spend $500 and expect to see jaw dropping astronomical vistae, you will be disappointed.

1: https://en.wikipedia.org/wiki/Averted_vision

200mm are 7.9 inches. Are the focal length and the diameter roughly the same?

Not at all, my 9.25” telescope has a focal length of about 2.4 metres - a focal ratio of f/10.

You’ll recognise f/x from camera lenses and such.

The diameter does control how much light the telescope “swallows” though, you’ll need a larger telescope to see less bright objects (or longer exposures, although when you are using your eye, that has a limit of course!)

So in this case, the post about is saying you’ll need something about 200mm diameter to see the comet. Anything smaller, and you’re just not getting enough light to see it.

That said, if you don't care about seeing it in real time you can use a MUCH smaller lens and stack exposures. You'll likely want a star tracker (MASSIVE decrease in effort) to go with your camera, lens, tripod, intervalometer, and Bahtinov mask (cheap, makes focusing MUCH easier). https://www.youtube.com/watch?v=iuMZG-SyDCU is an excellent tutorial on how to do this without the tracker.

Nope. Focal length is how far the light has to travel, diameter is the aperture, or how big the opening is to collect light.

The XT8 telescope I references has an 8 inch aperture, and a 1200mm focal length

GP is trying to point out that "200mm telescope" here means 200mm in diameter, not whatever arbitrary thing "200mm" apparently means in photography. The unit conversion adds more confusion, I don't know why they did that.

In photography, 200mm is the focal length of the lens. f/X is the focal ratio, with X being some number/ So a 600mm f/4 lens means it's got a 600mm focal length and 600/4 = 150mm aperture diameter. The reason for this is that camera lenses have an "iris" that reduces the aperture; that blocks some light but increases the depth of field. This means that unlike a telescope a camera lens's aperture can vary, so it doesn't make much sense to specify the absolute aperture for most situations.

It's also because the focal ratio tends to be a more accurate way to estimate how bright an image will be than the absolute aperture. A 35mm f/4 lens will take an image with just about the same brightness (LV) as a 600mm f/4 lens, even though the 35mm f/4 is only 8.75mm in diameter compared to the 150mm diameter of the 600mm f/4. The shorter focal length means light gets gathered onto the sensor from a wider angle, which exactly compensates for the decreased diameter. Since photographers typically can't take hours-long exposures (or stack hundreds of photos to get the same effect) the way astronomers can, this system works better for photography.

Sounds close enough in distance and far enough away in time that we could muster a robot intercept mission; would that be likely to be useful enough to warrant the cost?

Yes, and there have been (unofficial) proposals. With SLS or Starship as launch vehicle a fast intercept mission is feasible within 10 years and no corners cut on mission design.

> ("It's not like this is the Pedro and Gary show at all," Bernstein said. "In fact, we wanted the comet to be called Comet DES, but apparently that's against the rules.")

Des is a name here (short for Desmond). Hacky alternate reality solution: Hire a guy named Des to have the comet "officially" named after.

Most working astronomers doing original work (often looking for "something weird) do their own coding. That always impresses me. I have hard enough time with code but these guys not only code but do hard science. "Damn" I say under my breath, "that rules".

Lots of scientists in general. I help a neuroscientist friend with his from time to time and was surprised at how much custom code is running in his lab.

I enjoyed the writing of this article.

Serendipity, or luck if you prefer, seems to play such a big role in these things.

I would say good timing versus luck. They didn't just happen upon it staring through a telescope at the right time...their research was setup to find objects similar to a comet but slightly further away from the sun than where they found it.

Serendipity, or luck if you prefer, seems to play such a big role in things.

Wow I had to disable ublock origin and pi-hole to make that page load, wth.

Weird, works for me with UBO + Firefox ETP + Privacy Badger

It's nice to have a comet named after you right up to the point when you realise it's en-route to Earth! Mum and Dad were so proud...

(It's not)

Is anyone else disappointed to learn that it won't be impacting the Earth?

"Megacomet" is exaggeration. Chiron, which is anomalous in its own way, is of similar size.

I studied comets, and published some original research on comet tail interaction with the solar wind, not that my opinion matters much, but in my experience for what most researchers classify comets, this is absolutely a megacomet. It's more than twice as large as the one I kept in my mind from a decade ago that I considered one of the larger comets and Humason [0] was only about 40km in diameter.

Yes, cold bodies that have the properties of a comet may have lived the life of a comet at some point, or will again in the future, but currently something that shares a common center of mass with another object in a pretty stable orbit is not really going to get the full comet red carpet at the comet awards :)

[0] https://en.wikipedia.org/wiki/Comet_Humason

Chiron is not a comet.

Wikipedia more-or-less disagrees with you.

I like how it's "Wikipedia" that disagrees. Not the rando(s) who wrote or edited the article.

Well, it's the randos who wrote or edited the article, and the greater number of randos who read it afterwards and didn't edit it.

Chiron is a planet.

Chiron is a comet.

"Wikipedia" agrees with both of those statements.

Since it cannot be both, "Wikipedia" also agrees with the statements that Chiron is not a comet and is not a planet.

tldr: we don't know, it could be either

2060 Chiron /ˈkaɪərɒn/ is a small Solar System body in the outer Solar System, orbiting the Sun between Saturn and Uranus. Discovered in 1977 by Charles Kowal, it was the first-identified member of a new class of objects now known as centaurs—bodies orbiting between the asteroid belt and the Kuiper belt.


In Greek mythology, Chiron (/ˈkaɪrən/ KY-rən; also Cheiron or Kheiron; Ancient Greek: Χείρων means 'hand') was held to be the superlative centaur amongst his brethren since he was called the "wisest and justest of all the centaurs".


Chiron – A centaur with a white stallion body[9] and a son of Kronos. He is the mentor of Percy Jackson and the activities director at Camp Half-Blood. In The Lightning Thief, he first appears, disguised as a Latin teacher at Percy's school. He uses an enchanted wheelchair to conceal his horse half.[7] Chiron is played by Pierce Brosnan in the first film and by Anthony Head in the second film. In the musical, he is portrayed by Jonathan Raviv.


Also, it's fair to say systems based on classification based on subjective criteria will always have grey area, so any absolute statement about them will be difficult to defend :)

Oh great another comet...Neo-wise was the harbinger for COVID-19. I wonder what kind of doom this thing is bringing us for 2031?

What I would like to know is whether there is any indication from the DES whether there is, in fact, any Dark Energy activity at all.

Last I heard, DE was discovered to be, probably, a product of a pervasive miscalibration. I have not heard of any retraction or rebuttal. The recognition coincides with evaporation of galactic rotation curves as an indication of Dark Matter, also not, to my knowledge, rebutted. Cosmology is not unique in systematically ignoring evidence against the existence of its favorite phenomena -- Nessie and Bigfoot fans, either -- but its claims are the biggest.

https://en.wikipedia.org/wiki/Dark_energy doesn't contain the word "calibration" at all, so perhaps you could cite a source?

Huh? There is zero argument about the existence of dark energy in the scientific community. It's existence is obvious because you can actively see galaxies accelerating, on average, away from each other in all kinds of datasets observing the sky.

The questions are all about what actually causes it / the mechanism behind it, and details about its workings.

> There is zero argument about the existence of dark energy in the scientific community.


> It's existence is obvious because you can actively see galaxies accelerating, on average, away from each other in all kinds of datasets observing the sky.

No. Acceleration is inferred by fitting observed values of other quantities to the Friedmann equations.



I gather the precise validity of the Friedman equations depends on the universe being "homogeneous and isotropic", on a large-enough scale, yet not so large a scale as to render the terms meaningless.

But we keep finding the universe not to be uniform, even on a 100M parsec scale. A much larger scale would be uncomfortably close to the perceived size of the universe itself, flirting with that meaninglessness. So, it seems hard to know how the results are affected by such non-uniformity, or how much correction is needed.

There is plenty of debate still about Dark Energy.

...and it's been getting stronger lately as we've been finding more evidence that the visible universe is not homogeneous as we thought - which is one of the pieces of evidence for dark energy. We seem to be in a local empty area, and thus dark energy may no longer be needed to explain post-big-bang inflation.

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