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Comment Re:We Travel through a Crowded Galaxy (Score 1) 217

We Travel through a Crowded Galaxy ... and pass close to other stars. Furthermore the Sun probably evolved in a densely packed globular cluster.

Not a globular cluster. They're a different cluster of stars. Probably the Sun did form in a molecular cloud with many others - see for example, the modern Orion star-forming region. The light from the largest and brightest of the cluster's stars would then have dispersed the remaining gas and dust of the cloud (see both the Orion nebulae and the "Pillars of Creation" photo done by Hubble), eventually leaving an open cluster (see Pleiades, or Praesepe - the Beehive Cluster). And eventually, the cluster would have dispersed to the barely detectable (such as the

) before dispersing beyond the detectable.

Astronomers are looking for stars of the same age, chemistry and motions as the Sun, as potential stars formed in the same molecular cloud. But TTBOMK, they haven't found an example.

Since formation, the Sun - and it's cohort - will have orbited the galaxy on the order of 20 times. So even small initial relative motions would have thoroughly dispersed them by now.

All of which is a typology of different types of stellar cluster. But globular clusters are a different beast, not on that typology.

Comment Re:Say this aloud: "It's so massive..." (Score 1) 217

I believe it was first seen by a comet hunter. So that was a happy accident.

Your memory is faulty, or your original sources were incorrect. Pluto was discovered as the result of a multi-year search programme by the Lowell Observatory, looking for Pluto using calculations made by it's founder (and funder), Lowell. Clyde Tombaugh was hired by the observatory as an observer, and specifically assigned to perform this task. It was as accidental as something completely intentional.

People certainly tried to predict the existence of both Neptune and later Pluto from discrepancies in the orbits of inner planets. And while this approach has the potential to work, it remains unclear if either of the discoveries were more than coincidence. Tombaugh performed a comprehensive search of the anti-solar point, which scans the entire sky once per year (obviously). This covered the areas which Lowell predicted, and a lot of other sky too. By putting the hoped-for object in the darkest sky, the odds of detection are improved.

Charon had nothing to do with the discovery of Pluto. However, Charon's discovery did finally allow the mass of Pluto (and Charon) to be determined accurately for the first time, finding it to be around 1/1000 of earlier estimates.

To have been taught about the discovery of Pluto 3-4 decades before the discovery of Charon, you'd be remembering things you were taught between 1938 and 1948, putting you in your 90s, and possibly the oldest Slashdot reader I've commented to. What did you do in the War?

Comment Re:Say this aloud: "It's so massive..." (Score 1) 217

Has there ever been any evidence that this was once a binary system?

None. The Sun matches the behaviour of similarly massed stars very closely. While about half of all stars are in multiples (and so about 1/3 of star systems are multiple), no evidence of the Sun having a companion star has been reported.

If a putative companion were comparable in size to the Sun, than we'd see it by night. In fact, we'd not really have a night. (ACC played with that in one of the Space Odyssey sequels, IIRC)

If th putative companion were smaller than the Sun, it'd have to be considerably smaller to not be obvious. Smaller stars develop more slowly and last for longer, so it would still be visible. That relation lasts all the way down to the bottom end of "stars" at around 80 Jupiter-masses, when we get into the brown dwarfs. And even for them, we can model the evolution of temperature (from heat released on formation from infalling material) against time, and say "there isn't anything bright enough out there". (We do have adequate whole-sky IR surveys.)

Get down to Jupiter-mass and smaller (Brown-Batygin propose a Planet 9 of around 10 Earth masses/ 1 Neptune mass/ 0.03 Jupiter mass) and the temperatures and luminosities continue to decrease, but remain potentially observable (Brown has recently been complaining about the weather on Hawaii, blinding his telescope time looking for exactly this). Unfortunately, there are other similar-looking sources on the sky, at greater distances than the putative Planet 9, which is going to complicate interpretation of the data.

Astronomers do not reject the idea of "the Sun's companion", "Niburu", or whatever you want to call it out of caprice, malice to SF authors, or because their Mufti tells them to. The hypothesis has been rejected because observational evidence that should be visible if the hypothesis were correct has been looked for and is not there.

Comment Re:the sun is round how is it tilted (Score 1) 217

The answer seems to be that the planets' orbital plane, the ecliptic, is tilted.

It's worse than that. "THE ecliptic" is the projection of the Earth's orbit onto the plane of the sky as seen from the centre of the Sun. Or (equivalently), the projection of the Sun's position onto the plane of the sky from the Earth.

For every object in orbit around the Sun, there is a different ecliptic, similarly defined. We relate them to the Earth-Sun ecliptic purely for the convenience that we are mostly resident on Earth.

Now consider a particle on the Sun's equator, which for some completely incomprehensible reason (let's call it the Noodly Appendage) sits exactly stationary (whatever that means). As seen from the centre of mass of the Sun, it will trace a line on the plane of the sky in the same way as the ecliptics discussed above. That plane is not coincident with the Earth-ecliptic, nor with any of the other planet's respective ecliptics. They do cluster on the plane of the sky - within about 6 degrees as seen from the centre of mass of the Solar System - but they are not coincident. Add Pluto - 17 degrees spread now. Add Planet 9 ... 25 to 30 degrees.

Until recently, planet hunting took place on that 6 degree band. Pluto's discovery tripled the size of the search area. Planet 9 increases it around 6-fold again.

It's a big problem.

Comment Re:Just curious... (Score 1) 217

IANAA but I have an impractical idea that might work. Everything outside solar system is either redshifted or blueshifted by a large margin.

Your last sentence which I quote is where it breaks down. Not everything outside the solar system is considerably red- or blue-shifted w.r.t laboratory standards (at zero relative velocity). Most things that we can see in our galaxy have very little velocity relative to us, because most of the galaxy is invisible to us due to dust and gas in the plane of the galaxy. It's easier to see 10 million light years out of the galactic plane than to see a couple of thousand light years in the plane of the galaxy.

Say that we look towards the galactic centre. Since we're in a nearly circular orbit around the centre of mass of the galaxy, our velocity relative to it is nearly zero. The same applies for any other objects near our radial line from th centre of mass of the galaxy.

Nearby objects ahead of us and behind us in our orbits are also in near-circular orbits, and also have consequently low relative velocities.

Comment Re:Make a phone with a replaceable Battery (Score 1) 33

I want a battery that can be replaced by mere mortals.

Why? No seriously why? I'm interested in the use case, especially since longevity doesn't seem to come into it since you're so keen to replace the device.

He could be planning on selling or gifting the phone after he's used it for a year himself. It's not an uncommon use case. Niche maybe, but not unheard of.

There is probably a good niche out there for a high end phone with a user-replaceable battery, but I don't think Samsung is interested in it. They won't do it unless Apple does it and apple is never, ever even going to consider doing it. The wear and tear is pretty much the only thing that will keep Apple's customers upgrading their iPhones. A replaceable battery would probably cut Apple's future iPhone profits in half by allowing customers to keep their phones for twice as long.

Comment Re:Just curious... (Score 1) 217

And that is assuming it's a bright object reflecting a LOT of light from a very distant sun. If this thing is dark in color at all, the lumens available out at where they guess it is...

The best chance - if you read the papers - is in the fairly far IR, looking for remenant heat of formation from the assembly of the planet. If I remember the papers, which I did read.

It has all been put up on Arxiv, and no small amount of it submitted to this site as news items.

Comment Re:Just curious... (Score 1) 217

Now that there is evidence of a large object outside the elliptic I'm sure someone will try to calculate the period and approximate location of it.

If you follow Brown or Batygin's twitter feeds, you'll find that they've just had a substantial chunk of observing time on one of the big Hawaiian light buckets doing exactly what you suggest. Hint : time on telescopes like this requires a very well-formulated proposal. It's valuable time. And when the fog rolls in ... it's dead time.

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