aesmael: (tricicat)

arly in the week a girl (probably early high school but maybe late primary school) asked for help finding varied sources to site for her assignment about the solar system and that was fun. She's asked a similar question about different schoolwork months back and it is not often I get asked to deploy that much educational assistance on a topic.

Also interesting getting asked for help about a topic I've been relatively expert on when the appropriate response is not to display that - even if I had my peak knowledge on that subject it wouldn't have been helpful to her to display that. What she actually needed was for me to show her stuff like how to use library website database access to find stuff like Scientific American articles, and the astronomy section on the junior non-fiction shelves.

This got brought back to mind seeing a tweet by Mike Brown pointing to some new research on planetary system evolution. Felt good to read about that and to be excited again, despite that I probably will never be able to claim that expertise.

Mouth has been hurting again recently, despite having got another filling. Had strongly hoped that would resolve the matter for months if not years but it looks like I will be needing that root canal. Minor but persistent pain, so I put up with it last week through electrolysis. Pain got worse on Sunday, but nothing I couldn't handle with the painkiller regiment my dentist had recommended while treating me for an infection in this area a few weeks ago.

Called up on Tuesday (Sunday they weren't open and Monday I was at work during bankers' hours) to make an appointment. Disappointed to learn they had no spaces left this week, but I got a spot to have that root canal done on Thursday next week (2017-07-27). Of course by Thursday this week it decided to ramp up again so that even with painkillers in full effect I wasn't able to function through it.

This morning: went to dentist's office, got appointment moved to Monday, requested prescription for a stronger painkiller for the meanwhile. Got recommended a slightly stronger over-the-counter painkiller instead. Hoping that will be enough. Only three days now instead of another week. I really don't want this procedure done, am dreading it, but it is clearly not feasible for me to refrain.

Perhaps this is to a degree my fault - might have gotten the cavity seen to when I first noticed there was a problem, and maybe it wouldn't have reached so deeply that I'm needing to have the nerve itself removed if only I'd taken some time to decline additional shifts and got it looked at back in summer or early autumn. Maybe then it could have been caught before it so deep. Instead I thought I didn't need to stake time out to care for myself, that I could rely on gaps in the flow of time requested of me by the library

aesmael: (it would have been a scale model)

I miss programming. It was the last thing I was good at. Which is not to claim any particular demonstrable level of skill or aptitude. But that one class I took in 2012 I worked hard at, and I got good grades for my hard work. I miss having something I could work at and feel I was making progress in understanding and skill. Unfortunately I keep being too occupied with work and school or otherwise insufficiently self-directed - as well as lacking in inspiration - to pursue further development in learning to program. Or rather, given the long gap of inactivity, re-learning to program.

As one might guess, today I did have some inspiration on a suitably scaled project I might undertake when I am able, and am writing this partially as a reminder to myself that I should do so. In this case I was wondering about where a stationary orbit around Ceres might be located and whether it would be stable.

I realised I could define a succession of more complex versions of the problem which I could automate the solving of. Simplest version would just take mass and rotation period for input and give an orbital radius as output. More complex versions could relate that to the Hill sphere of the synchronous-orbited body and identify whether the radius for a synchronous orbit falls within that range or whether it is outside (and therefore not stable). That would require additional inputs such as the ~planet's semi-major orbital axis and the mass of the star (or other parent body).

Then if getting that working, could add further complexity in trying to get a range of values computed, frex "as the orbited body's rotation is slowed, at what point does the radius of a synchronous orbit fall outside its Hill sphere?" or "at this rotation rate, how near to its parent body can this object orbit and still retain a synchronously orbiting satellite?"

Should be nice sort of project. Fairly simple, already solved problems (I could verify them with pen and paper), well-defined goals that are definitely outside my current skillset. I hope I will manage to get myself the time for working on this. Could feel proud of success.

aesmael: (sudden sailor)

List of planets with weirdly transparent atmospheres:

  1. Earth
  2. Mars
  3. Triton [ish]


List of planets with normal, cloudy atmospheres:

  1. Jupiter
  2. Saturn
  3. Neptune
  4. Uranus
  5. Venus
  6. Titan
aesmael: (Electric Waves)

Finished listening to the first year of Planetary Radio, into the second year. Will miss the old theme music which sounded to me a lot like music from the SNES version of SimCity

Although the new theme puts me a lot in mind of Unicron's theme from the 1986 Transformer's theme, so that also amuses.

Still finding it remarkable how much things have changed or been anticipated since that first year of the show.

The Galileo mission was at the end of its mission at Jupiter and, during the, plunged into the planet's atmosphere to avoid contaminating Europa. They had project manager Claudia Alexander on the show to talk about this, and mentioned her next mission waiting to launch, Rosetta - which is just now nearing its target 67P/Churyumov-Gerasimenko.

They had Alan Stern on, anticipating the future launch of New Horizons (arriving at Pluto next year), and the rumours that some astronomers think maybe Pluto should no longer be counted a planet. Of the radio show: "Let's hope we're still doing this when you arrive" - looks likely from 2014.

They had Marc Rayman on, talking about recently concluded mission Deep Space 1 and the prospect of using technology tested then on a future mission, Dawn, which has now visited Vesta and will be arriving at Ceres next year.

The two Mars Exploration Rovers Opportunity (still functioning more than a decade later) and Spirit were launched and en route to Mars for their 90 sol mission.

Low key anticipation for the arrival of Cassini the next year, and all its findings and beautiful imagery as yet unrealised.

So much change, so much, and also so much continuity. Missions anticipated at the birth of the program coming to fruition now. I wonder what else has been anticipated during its run so far, and worry the answer is not much - not much to come but what's been coming the whole time.

aesmael: (tricicat)

Listening to an episode of Planetary Radio, the guest was asked where, if not Mars, in the solar system might life be found. I was surprised his answer was Europa - I've become accustomed to scientists saying Enceladus.

Then I realised that of course, this episode was recorded early 2003. The geysers of Enceladus had not yet been discovered. In fact, Cassini had not yet reached Saturn and Galileo still orbited Jupiter.

This also reminded me that Mike Brown had not yet discovered Eris, nor most of the other dwarf planets he is famous for, the Kuiper Belt is far less populated in our knowledge and Pluto as yet relatively firmly regarded as a planet is.

So much has changed in our understanding of the solar system over the past decade.
aesmael: (haircut)

Originally published at a denizen's entertainment. You can comment here or there.

About a week ago I was listening to the Skeptic's Guide to the Universe episode wherein they interview Pamela Gay and Fraser Cain about their podcast, Astronomy Cast.

I only relatively recently got access to enough bandwidth to make listening to podcasts practical, have been catching up as far back as the various feeds I've subscribed to will let me, so this particular episode was from the first half of 2007.

It was quite disappointing from my perspective six years in their future to listen to them rattling off lists of future space missions which would hopefully be able to better characterise exoplanets and say of each "Nope". All cancelled or delayed or otherwise have not eventuated.

On the other hand, no mentioned that I noticed of NASA's Kepler mission, which has produced amazingly fantastic results over the past few years. So not all bad news.

Originally published at a denizen's entertainment. You can comment here or there.

First of all, nifty article from Bad Astronomy on the Moon's youngest known natural crater. This was not present in Apollo 15 images from 1971, but was present in images from the Lunar Reconnaisance Orbiter dating to 2009. So that is very new! The actual object responsible would have been tiny, and harmless to Earth thanks to our atmosphere, but still. Isn't it cool that things still change in the solar system? Not even our moon is static.

Second of all, I don't know anything about them but these planned ESA missions sound like they could provide us with a lot of exciting information once they get underway. Particularly the LISA precursor - I'd had the impression that LISA, which might get us our first direct detection of the gravity waves predicted by general relativity, had been canned.

Finally, here is a pretty video of the sun:

Originally published at a denizen's entertainment. You can comment here or there.

This is intriguing news.

Am amused by the number of people in comments pointing out Kepler has a selection bias toward detecting multi-planet systems in which the orbital plane is relatively 'flat' compared to our solar system. It certainly does, since the closer planets are to orbiting in the same plane, the better the chance that if one is seen to transit from our perspective, others in the same system will too.

But, the team was expecting to find only a couple of systems where planetary orbits were so closely aligned. So far, they've exceeded that expectation by a factor of 50. That's significant! More than 100 systems with multiple planets observed to transit, when only two or three were expected. Means something new-to-us is going on, because we're seeing a lot more than we expected to even _with_ Kepler's bias toward detecting them.

It is certainly intriguing that these flatter systems have found-planets all sub-Neptune in size. Of course, Kepler wouldn't have detected our Jupiter or Saturn yet, so it may be a bit premature to conclude it's due to a lack of giant planets shaking the systems up. I do wonder if it is true.

Originally published at a denizen's entertainment. You can comment here or there.

A fun paper I came across a while ago - The Steppenwolf: A Proposal for a Habitable Planet in Interstellar Space. The question at hand is, what are the optimal conditions for a planet ejected from its star system to retain liquid water?

Unfortunately it has been a few months since I read through the paper itself, so I've forgotten a lot, and I'm not willing to do it again just now. However, the results are surprisingly optimistic. A terrestrial planet with an Earthlike composition would be able to retain liquid water under a layer of insulating ice for significant periods if its mass were approximately 3.5 times that of Earth. And since more massive planets could potentially retain a higher mass of volatiles I wouldn't be surprised if isolated planets below that threshold retained liquid water too.

Meanwhile, this sentence - "If a rogue planet had about ten times higher water mass fraction or a thick cryo-atmospheric layer, it would need to be only ~0.3 times the mass of Earth to maintain a liquid ocean." - seems a bit more theoretical, since I am not sure are likely to encounter planets of such low mass with such large amounts of the appropriate materials. Unless I un-forget about the possibility of predominantly icy planets.

The whole paper is fascinating and worth a read. It's just a shame it is so difficult to detect these planets if they are out there. I am not sure we ever will without some form of interstellar travel (if nothing else, even slow automated exploration would give our descendants more vantage points from which to potentially observe one). Or we could get lucky and find one in the neighbourhood. Not betting on that.

Originally published at a denizen's entertainment. You can comment here or there.

Old news again! Evidence for Rain on Titan. I find it rather wonderful to think that all this time Titan has had seasonal rains and we didn't know. When I was in high school, rain on Titan. When Pluto was discovered, unobserved rain on Titan.

Back in 1655 when Titan was first discovered, quite possibly there was a downpour of methane happening that Huygens couldn't see. Amazing. Wonderful.


2011-04-27 22:51

Originally published at a denizen's entertainment. You can comment here or there.

I disagree with the IAU's decision on defining planets, sure. But articles like Should The Cluttered Skies Demote Earth? (and comments of a similar style) make me want to ask people to please stop helping.

Pluto and other 'dwarf planets' have crossed a threshold. Their mass is sufficient that gravity[1] dominates their shape. They are probably all differentiated bodies. So I consider them interesting in ways different to other small bodies, the smaller asteroids, comets, kuiper belt objects, and irregular moons. Besides, in astronomical terms our sun is a dwarf star, but it is still a star.

However. If one looks at the dynamical properties of these bodies, differences between these 'dwarf planets' and the others become sharply apparent. They just don't have the same heft. Looking at the table in that article it is clear that one of the most common arguments against the dwarf planet categorisation - that if you put Earth or some other planet out in the kuiper belt, it would be called a dwarf planet (and that location should not determine what an object is) and thus the whole dwarf planet thing must be nonsense. But according to those figures Earth would have to be moved nearly 3,000 times further from the sun before it would even approach the dynamical insignificance of Pluto or Eris, and that doesn't account for the effect Earth would have had on that region had it been orbiting out there these several billion years - I am pretty sure those figures are derived from the solar system as it is now, not as it might have been.

I do think for planetary bodies a combination of physical and dynamical properties ought to be considered when deciding what to call them. If Ganymede or Titan orbited the sun we'd probably call them planets. If Mercury orbited one of the other planets, we'd probably call it a moon (actually we might call it a double planet if it orbited Earth or anything smaller, but never mind). So I think location matters. Context matters. And arguments like "If we moved X it would / wouldn't be a planet" aren't convincing because they're trivial or false. Nor, to say Earth should be a dwarf planet on account of the stuff around our orbit because the total mass of it is insignificant - in any interaction between them Earth will do the scattering, not be knocked around or much affected. As arguments go, they're pathetic, and I'm embarrassed to see people somewhat on my side using them.

There is an article by S. Alan Stern and Harold F. Levison proposing a planetary classification scheme which meets all of my requirements, and adds some new dimensions I had been hoping for but had not thought of. Although I am partial to major and minor planets rather than über and unter planets the latter set is probably a better choice for not conflicting with our existing use of minor planets. I recommend reading the linked pdf for anyone interested in this topic. It is clear and straightforward, and I doubt I could express it better here. If I were Tyrant of Astronomy I might make that document law and then abdicate. Maybe.

I keep trying to write a description of the proposed scheme here despite what I said immediately above. Probably because I worry people won't follow the link. So, short of copy-pasting large chunks, we simplify: a planet is defined as an object massive enough that its shape is dominated by gravity, but which does not ever sustain fusion. A mathematical test is proposed to decide whether a particular planet is über (dynamically dominant) or unter (not dynamically dominant) in its orbit. Some planetary satellites are considered planetary bodies themselves. Further classification subdivisions are proposed according to composition (rock, ice, or hydrogen) and mass (subdwarf, dwarf, subgiant, giant and supergiant[2]). In this scheme, Earth would for example be a rocky dwarf über planet.

Much of what pleases me about this scheme is its scope for recognising both the variety and the similarities of planets. Pluto is different from Mercury is different from Earth is different from Uranus is different from Jupiter. They're all different from Titan, Triton, Mars and Ceres. But they're all interesting, and have qualities in common which non-planets do not have. Plus, it feeds my sense of wonder and excitement about the universe.



[1] Along with other details such as their material properties and angular momentum, e.g. 20000 Varuna. Also happens with stars, for example Achernar.

[2] This is fairly directly taken from how we classify stars according to size.

Originally published at a denizen's entertainment. You can comment here or there.

First unequivocally 'solid' extrasolar planet has been confirmed. Others we've found I'm pretty sure qualify, but this is the first pinned well enough it can't be hiding non-terrestrial nature in statistical outlier.

Further details and my news source at Bad Astronomy.

Originally published at a denizen's entertainment. You can comment here or there.

Increasingly less recently I had been discussing with Pazi a game project. I wanted to do something useful so I offered to craft a little program module which could generate 'realistic enough' star systems. Something that would not simulate stellar formation and evolution directly, but which could use information derived from those simulations. I suspect such a tool could find a few uses, all of roughly the same sort, but apart from being useful I mainly think it a pretty nifty idea. Of course I would need to first finish my current project, but that is badly in need of finishing anyway.

Trying to determine what I would consider a 'first finished' version, not the first steps I would take in writing it but what it would need to do for me to consider it getting to completed. That, and some sorting out in my mind of how to approach the workings of this thing.

My thinking is to start with the star itself and build up the system around it in a sort of abbreviated history. Presumably, get it working for single stars before worrying about multiple systems, unless those turn out not really harder to put in. We get a few basic figures for the star, stuff like mass, spectral type, luminosity, then use those to proceed. Stellar mass typically correlates with disk mass available immediately after its formation, determining how much material is available to form planets and potential early migration activity for them. Plus, the distances at which various sorts of planets can form. I think we can relate those figures to get some nice functions for populating planets from. Start by placing giant planets, unless consensus has changed on the order of formation, then the little ones, abstract some pseudo-orbital-evolution and there we have our own impromptu planetary system.

Each planet's numbers - semi-major axis, eccentricity, mass, composition - get to interact with the host star's numbers, and we get a rough guide to the world's likely surface conditions, atmosphere and chemistry of note. There might be more than one class a given world could fall into.

I find the prospect of this fairly daunting. I imagine for an experienced programmer it would fall into the class of 'relatively simple' but for me, it's not. I'm only just barely learning, still. But I look forward to accomplishing this. I suspect the first thing needing doing is collecting papers with relevant modelling statistics to use; been wondering if it might be much harder too to get information for moons and small bodies.

I worry I have somehow done badly by describing my goals in the terms I have, rather than some technical description of coding intentions, but suspect this to be a silly worry. Am expecting to be learning a lot of how in the doing, and believe it is advantageous to have clear ideas on what I want the outcome to be.

Once that 'first finished' version is working I would want to add some fancier abilities, like aging. This would be needed anyway to incorporate giant stars since those again modify their planets as they age and expand and brighten, but also would be useful for incorporating very young stars still in the process of forming planets and details like at what point terrestrial worlds are likely to become tectonically dead. I suppose an approach that might work is to generate values for the whole system's duration (at least, mark points when things change and the values before and after). I suppose it is unlikely this program would get used for anything that depicts time-spans long enough for stars to visibly age, but at least for some sort of manual editing or inspection it would not end up generating a new history every time the age is tweaked. Perhaps too much, but I cannot help but feel it would be a useful approach somehow.

As for populating a larger 3- or 2-dimensional space, I suspect that would be harder to do, maybe want for another tool that talks to this one. Currently I'm thinking finding a good way to place stars in a field would be a more difficult thing to do than getting population kind distributions for various stellar environments. Hopefully by the eventual time I get to attempting that I will know much better.

That's main thoughts and plans on this for now.

[At Systemic can be found an excellent example of why this will likely be difficult to do. At the moment our models aren't reliably predicting the sizes of giant planets in some important situations. And we're still finding situations where our models are in error, which is why I suspect I will have to aim for 'realistic enough' and post refinements as astronomers make refinements. Or as soon after as I am able to.]

Originally published at a denizen's entertainment. You can comment here or there.

[due to slowness of writing, all todays are now yesterdays]

Today was filled with expectations contrary to my expectations. What I expected was a brief morning visit to the offices where my case manager, who handles me so Centrelink doesn't much have to, then to return home and participate in clearing out a dungeon in World of Warcraft, followed by an evening of composing an application for the latest library job I found going.

It was unusually tricky finding a parking space there, but at least I got to hear the end of Margarent Throsby's interview with Dr Peter Bowden, although it was a bit awkwarder than usual - I think he was not prepared to handle digressions from the topic of whistleblowing and ethics.

Contrary to the interactions I'd expected, talking briefly of what I'd been up to job-searchingly and what I planned to be up to, the only topic was that they'd found a possible job I could go interview for and preparing me to do this once I agreed I had some interest. That job was of an inbound call centre sort, handling account inquiries on behalf of a cable television company. I figured I would have to cancel the dungeoning to make that on time, but it turned out to be anyway already cancelled.

Spent a few hours having lunch and researching and getting changed, then set off to drive. That was a bit of a nervous drive, on the motorway, since the car I have use of is 21 years old and rattles a bit when it travels faster than 80 kph. I felt a bit like if I were standing at the top of a ladder and unsure of its steadiness. Rain grew heavier near my busier urban destination, peaking at one of the more stressful driving experiences I've had making the exit onto a quite busy main road.

I ended up mistakenly in a lane too far to the left, one marked 'must turn left', so spent several minutes poking around side streets until finding my way back to the road I needed, pushing 'about ten minutes early' into 'just on time'. Unfortunately the group had already gone in and the staff who met me didn't quite know what was going on, so it was a couple of minutes until I was directed to the right room. Not the last to arrive, either.

Interview was simple enough. Bit of impromptu self-introduction public speaking, a group task, then one on one interviews and we were done. Was annoyed that in the group with other candidates a lot of my communications were ignored until someone else expressed the same thing, although some were taken up with enthusiasm (we were supposed to diagram what customer service is and why it is important), but otherwise I felt I did pretty well. At least, that I did about as well as I was able, and if I don't get the position it won't be for any lack or fault on my part. Which is about all I'm after really.

Driving back I got to diagnose the problem with the motorway in that direction - too many lanes being created and then ended, congesting the drive by forcing repeated traffic integration. Also got another surprise on the radio travelling back when they played the 14th symphony by Sir William Herschel, more famous as the discoverer of Uranus and infrared radiation. Was fun to listen to, too, so now I want to try and collect the music of this famous astronomer. Am sure I must have known he was also a composer, since I read a lot of science history books and they'd be likely to mention such a detail, but I'd completely forgotten it.

Later in the evening my sister contacted me, requesting collection from the station. Despite coordinating activity I arrived some minutes early and spent a tense while watching a cat walk along the track, fearing a train would come along any moment and hoping the cat knew how to keep safe. But it vanished into the darkness long before anything happened, and that is all I know of that cat. A while later I saw behind me some queer green reflection which revealed a train coming from the other way. It stopped briefly, signed prominently as a prototype which no one should board, then departed in high unpleasant screeching. I saw a party of railway workers aboard, presumably testing the user experience, and then not long after my sister arrived to be collected.

The last and least pleasant upturning of expectation came watching again the series 2 finale of Ashes to Ashes and being informed that no, we still do not get to see series 3.

Okay, that's a day, done.

aesmael: (haircut)

Originally published at a denizen's entertainment. You can comment here or there.

Large in extent image behind cut )

A new month, so time for a new desktop background. I had been using art shared from other people, but this time chose a screenshot I'd taken in Celestia a few days before.

The perspective is from the surface of Deimos, looking down to Mars below. Much closer than our moon to Earth. If you look along the terminator marking day from night, a white spot is visible. That is Phobos, the other moon, caught in its (less than) 8 hour orbit at a dramatic moment.

Apart from its large crater Stickney (not shown), Phobos is famous for its low and fast orbit, which contrary to that of our moon is decaying lower and faster. When it drops not much lower, tidal forces from Mars will tear it apart and for awhile Mars may be ringed until those fragments rain down upon its surface.

Deimos gets much less love, but perhaps when it is the last moon remaining this will change.

aesmael: (probably quantum)
"What we see today, when we look out at the Universe, is that the farther away things are from us, the faster they move away from us. "

Let's rephrase that. Let's say "the farther away things are from us, the faster we observe our separation increasing". The standard phrasing encourages misunderstandings about the nature of the universe's expansion.
aesmael: (haircut)
Lately have been using this image as my desktop background:

It is an image I took with Celestia two years ago and, coming across again, seemed like good background material.

The main object in the foreground is of course Europa, mostly eclipsing Jupiter in the background. To the left is the Sun, and to the left of that another disk is visible. I recreated this shot in Celestia recently to verify (the time displayed in the image is local to Sydney, so I had to adjust the clock settings in Celestia to get to the right moment, but if you leave them unaltered and enter the time shown you get a shot which is nearly a mirror image of this one) that the other disk visible is indeed Io and not one of the other Galilean moons.

I think it is wonderful that there are places in the solar system we could go and see more than two objects visible in the sky as more than points.
aesmael: (Electric Waves)

  • There weren't ads insisting it were really possible and could happen

  • The plot weren't an annoying apocalyptic myth going around for years already

  • And if astronomers and others weren't having to reassure terrified people that the end of the world is not imminent, thanks partly to the film's advertising

Originally published at a denizen's entertainment. You can comment here or there.

In the past week I have been surprised by two pieces of news concerning Saturn and rings.

First, from the Planetary Society Blog: findings which might be evidence for a posited ring around Rhea. As described in that article, a series of equatorial spots on Rhea bright in ultaviolet light might be evidence of collisions from ring particles orbiting the moon. These particles, if they exist, would occupy a size and distribution which makes them particularly difficult to detect visually directly with the instruments we currently have available.

It seems the idea of rings around Rhea has been around longer than I have been aware of. Apparently they were originally proposed to explain a decreased electron flux in the vicinity of Rhea back in 2005, and I sure didn't realise there was this much evidence already. Would be very exciting indeed to get a direct and definite confirmation about this.

Sadly given how difficult these rings are proving to image, it is unlikely there will ever be beautiful views of the Rhean ringscape. We shall just have to comfort ourselves with the knowledge of something wonderful.

The other news is the discovery of a new ring around Saturn itself. This one, discovered by the Spitzer Space Telescope, is the largest and most diffuse planetary ring yet discovered. The details can be found in this press release. Basically it is very large and very faint, and only detected because of its cool infrared glow. I am concerned that the end of the release specifies this information was gathered before Spitzer ran out of coolant, and whether this means we won't be able to obtain further observations of the ring for a while. It might take us a long time to discover if this ring 'only' spans from six to twelve million kilometres from Saturn, or if that were merely its brightest, densest part.

Apart from the amazement of a whole new feature being discovered, this is particularly intriguing because Saturn's moon Phoebe orbits within this ring and is thought to be the source of its material (via dust knocked off from impacts, most likely). If so, and depending on what else is found, this ring could be a key part of one of astronomy's longer-standing mysteries: the two faces of Iapetus. Although it has long been suspected that material from Phoebe deposited on Iapetus is the reason that moon has one bright hemisphere and one dark (more or less), I think this ring is the first actual detection of a possible mechanism for the transfer of this material.

If that bears out I think I will finally have an answer to a mystery I have been intrigued by since I was a young child; for a long time Iapetus has been one of the solar system bodies I was most fascinated by.

aesmael: (haircut)

Originally published at a denizen's entertainment. You can comment here or there.

Last week seems to have been a good week for news in astronomy. At the least of the sorts that capture my especial interest.

From Universe Today, Spot Discovered On Haumea Rich With Organics And Minerals.

Haumea, one of those planets called dwarfs, is notable for its extremely rapid rotation (a bit less than four hours) distorting its shape well out of spherical and its pair of moons (and the origin of those moons being a probable collision early in Haumea's history which stripped much of its mantle and originated the Haumea collision family). I was thrilled to see such a headline, although on further reading of the article it seems a touch premature:

Possible interpretations of the changes in the light curve are that the spot is richer in minerals and organic compounds, or that it contains a higher fraction of crystalline ice.

So although it appears there is a dark patch on Haumea's surface, we won't know its composition until next year at the earliest. Still, I'm excited to learn just about any new details about these worlds.

Via the Extrasolar Planets Encyclopedia (currently 374 planets and counting), a preprint of a paper submitted to The Astrophysical Journal: The Formation Mechanics of Gas Giants on Wide Orbits.

Presently there are two major theories concerning the formation of giant planets. The core accretion model holds that if a planetesimal can accumulate at least ten Earth masses before the gas of the surrounding protostellar disk dissipates, it will be able to rapidly accumulate a massive envelope of gas. Meanwhile the disk instability model proposes giant planets form when part of the disk becomes unstable and collapses in on itself like a version in miniature of how stars form from giant molecular clouds.

For a while now the core accretion model appears to have prevailed, I think largely because the two models produce different sorts of planets with only a bit of overlap, and most of the planets we have been finding so far suit the core accretion model far better. That is, planets with up to a few times the mass of Jupiter, on orbits less than 10 - 20 AU (Astronomical Units) from their host star.

This paper reminds that there are now planets being found which the disk instability model explains far better than the alternatives - more massive planets approaching the realm of brown dwarves, on orbits too distant for core accretion to have produced them in situ, with orbital dynamics suggesting they were unlikely to have arrived there by scattering from interactions with other planets.

After reading it, I would not be surprised of Fomalhaut b did turn out to originate from core accretion and scattering, but I think they are probably right about the planets of HR 8799 and that there are many more such systems to be found. Would be very interested to learn if there are inner planets to these systems yet undiscovered, and what happens when both planetary formation modes are at work in the same system.

Another quick bit from Universe Today: Smallest Exoplanet Yet Has Rocky Surface. CoRoT-7 b may not turn out to be the smallest planet orbiting an actively fusing star yet discovered, but it is the one with the lowest mass we are currently sure of. The article is definitely worth reading, as some of the details about that planet are amazing.

A picture from Astronomy Picture of the Day, the Andromeda galaxy in UV. Was thrilled to note that in the mouseover comparison, the correlation of UV areas with bright blue starforming areas.

From The Planetary Society, "Richard Kowalski is the first person in history to possess a piece of an object that he discovered in space", an asteroid detected in space and tracked to its impact in Sudan last year. I don't know how I managed not to hear of this at the time it happened, but here is an account from shortly after it happened.



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