APOD: Alpha Centauri: The Closest Star System (2011 Jul 03)

[neufer]

In the information brought up through the Rigel Kentaurus link it states "Rigel Kentaurus is the 3rd brightest star in the sky". However, in the explanation to the APOD it states it is the "fourth brightest star in the night sky". I would be grateful if someone could please let me know which is correct.

The APOD should have equated:

• 3rd brightest star Rigil Kentaurus with Alpha Centauri (A+B)
  NOT just with 4th brightest star Alpha Centauri A.

[DavidLeodis]

In the information brought up through the Rigel Kentaurus link it states "Rigel Kentaurus is the 3rd brightest star in the sky". However, in the explanation to the APOD it states it is the "fourth brightest star in the night sky". I would be grateful if someone could please let me know which is correct.

The APOD should have equated:

• 3rd brightest star Rigil Kentaurus with Alpha Centauri (A+B)
  NOT just with 4th brightest star Alpha Centauri A.

Thanks neufer.

PS. I'm surprised that you made no fun response to my Clark Kentaurus quip.

[neufer]

The real reason Hooter Girl is going to wear bicycle
safety glasses is to maintain her secret identity.

I'm surprised that you made no fun response to my Clark Kentaurus quip.

Astronomy is easy, comedy is hard
(...especially early in the morning).

Kent Taylor

Rigil ("left foot") Kent

[owlice]

Oh, Art, I knew I couldn't fool you!

Of course, if you never go biking with me, I don't really need to work very hard to maintain my secret identity, do I?

[Ann]

In the information brought up through the Rigel Kentaurus link it states "Rigel Kentaurus is the 3rd brightest star in the sky". However, in the explanation to the APOD it states it is the "fourth bightest star in the night sky". I would be grateful if someone could please let me know which is correct. Thanks.

PS. There should be a Clark Kentaurus star (perhaps there is!).

Mmmm, I'm an old Superman fan. Clark Kentaurus, indeed. I googled "Clark Kent Alpha Centauri", but I found nothing. I'll post this image, all the same. Reach for Alpha Centauri, Clark Kent - or at least, try to stop that building from falling!

Click to view full size image

Ann

[neufer]

<<In the early years of Superman comics, the sun of Krypton was unnamed and was given no effect on Superman's powers, which were attributed first to greater evolution, and then to a combination of innate powers and Earth's lower gravity. Starting in 1960, the fact that Earth's sun was yellow while Krypton's was red became the explanation for Superman's powers, with our sunlight fueling them like the charge of a battery. This new Krypton was approximately one and a half times larger than the Earth and orbited a red supergiant called Rao, 50 light-years from our solar system. In the standard Silver Age continuity existing up until Crisis on Infinite Earths, Rao's red sun radiation actively suppressed the superhuman abilities of Kryptonians, as their powers only worked in the radiation of a yellow sun. The post-Crisis version created by John Byrne stated that Kryptonians absorbed solar energy, with the dim output of Rao being just enough to sustain them, and a yellow sun producing enough energy to "supercharge" a Kryptonian metabolism to levels of power not seen in their native environment, though it takes years for Clark Kent to build up enough energy to reach the level of power he displays as Superman.

Krypton's primordial era produced some of the most dangerous organisms in the Universe. [These sexless bugs would occasionally fly into owlice's mouth & eyes.] It was for this reason that Krypton was chosen as the place to create Doomsday through forced evolution. Up until its destruction, many dangerous animals, including ferrophage moles, still existed on Krypton. Kryptonians had to use their advanced technology [e.g., bicycle safety glasses] to survive. Over 100,000 years ago, Krypton had already developed scientific advancements far beyond those of present-day Earth, and within a few millennia had conquered disease, learned to delay the aging process, and perfected cloning; vast banks of non-sentient clones held multiple copies of each living Kryptonian so that replacement parts were always available in the case of injury. All Kryptonians were effectively immortal, "with all the strength and vigor of youth maintained", and enjoyed an idyllic, sensual existence in an Arcadian paradise.>>

[DavidLeodis]

Thanks all for your responses.

Is it a bird? Is it a plane? No, it's Superstar (aka Clark Kentaurus).

[cwb]

From an interested novice.

While looking at the explanation of this photo, APOD: 2011 July 3 - Alpha Centauri: The Closest Star System , it says that the two stars are separated by only 23 times the Earth- Sun distance .

What keeps them apart? Are they orbiting around each other? At what speed? Seems to me that if they got that close a collision would be almost automatic.

[Chris Peterson]

What keeps them apart? Are they orbiting around each other? At what speed? Seems to me that if they got that close a collision would be almost automatic.

Yes, they are in orbit. Actually, every body in the Universe (if they are causally connected) is in orbit about every other body (mostly in open orbits). This is why collisions are extremely rare- two bodies that collide have to have their position vectors nearly collinear. There are double stars orbiting even closer than this pair- some orbit so closely they exchange material. Those eventually collide because they experience drag, and their orbits decay. But otherwise, even closely orbiting bodies that aren't perturbed by other bodies will typically have stable orbits for many billions of years.

[neufer]

two bodies that collide have to have their position vectors nearly collinear.

That is a strange way of putting it.

"A set of points is collinear if they lie on a single straight line or a projective line."

Do anti-ballistic missiles do that with their targets

[Chris Peterson]

two bodies that collide have to have their position vectors nearly collinear.

That is a strange way of putting it.

Is it? I guess that is just one of two possibilities. Two bodies acting under the influence of gravity alone need to be on paths that result in their being at the same place at the same time. In Euclidian space, those vectors need not be lines, of course. But you might generalize the problem to geodesics, in which case they would be treated as lines, and would necessarily be collinear or intersecting if the bodies were on a collision course (with a margin of the radii of the bodies). Does that make sense?

In any case, two bodies in orbit won't collide (unless the orbital radius reaches the radius of one of the bodies, of course). It's a bit of a trick to get two bodies on a collision course, and requires perturbation by at least one other body.

Do anti-ballistic missiles do that with their targets :?:

Anti-ballistic missiles are themselves either ballistic or under thrust, so they can't really be compared to bodies influenced only by mutual gravitational forces.

[neufer]

two bodies that collide have to have their position vectors nearly collinear.

That is a strange way of putting it.

Is it? I guess that is just one of two possibilities. Two bodies acting under the influence of gravity alone need to be on paths that result in their being at the same place at the same time. In Euclidean space, those vectors need not be lines, of course. But you might generalize the problem to geodesics, in which case they would be treated as lines, and would necessarily be collinear or intersecting if the bodies were on a collision course (with a margin of the radii of the bodies). Does that make sense?

I think know what you are trying to say but I also know that if you gave it another 24 hours you could state it much better than you have thus far. (Perhaps something along the lines of the relative position vector and the relative velocity vector being collinear.)

I, myself, would have said something about the angular momentum around the center of gravity being negligible but that's probably not the simplest way to explain it to a non-physicist type.

[Chris Peterson]

I think know what you are trying to say but I also know that if you gave it another 24 hours you could state it much better than you have thus far.

I don't doubt it. That's often the case, isn't it?

Anyway, I think the implication of the original question was that gravity somehow tries to pull bodies together, and therefore close binaries should collide. Hopefully between us we got across the idea that unless the bodies have no tangential velocity with respect to one another, the attraction of gravity creates an orbit, not a collision. (Still not perfectly rendered, I'm afraid; sometimes math is so much simpler than English.)

[Ramses]

Has anyone noticed how there are small lumps of dark stuff outlined by background starlight? There's one in the upper-left and at least four in the upper right images. Would those be asteroids? Of the Centauri-system? Comets? Failed planets?

[Chris Peterson]

Has anyone noticed how there are small lumps of dark stuff outlined by background starlight? There's one in the upper-left and at least four in the upper right images. Would those be asteroids? Of the Centauri-system? Comets? Failed planets?

They are just imaging artifacts. It would be impossible to see even a large planet at the resolution of these images.

[neufer]

New Kids On The Block – The Brown Dwarfs
by Tammy Plotner on July 14, 2011

False-colour images of the two brown dwarf discoveries WISE J0254+0223 and WISE J1741+2553. (Credit: AIP, NASA/IPAC Infrared Science Archive)

---

<<When it comes to being close to “home”, there’s not a lot of stars out there in our general neighborhood. Proxima Centauri is 4.2 light years away and Rigil Kentaurus is 4.3. There’s Barnard’s Star, Wolf 359, Lalande 21185, Luyten 726-8A and B and big, bright Sirius A and B. But what about a celestial neighbor that’s not quite so prominent? Try a pair of newly discovered brown dwarfs.

Scientists from the Leibniz Institute for Astrophysics Potsdam (AIP) using the NASA satellite WISE (Wide-field Infrared Survey Explorer) have discovered this unlikely duo just 15 and 18 light years from our solar system. “We have used the preliminary data release from WISE, selected bright candidates with colours typical of late-T dwarfs, tried to match them with faint 2MASS and SDSS objects, to determine their proper motions, and to follow-up them spectroscopically.” says RD Scholz, et al.

Named WISE J0254+0223 and WISE J1741+2553, the pair drew attention to themselves by their very disparity – one very bright in infrared and the other very faint in optical light. Even more attractive was the speed at which they’re moving – the proper motion changing drastically between observations. “The very large proper motions are a first hint that these objects should be very close to the Sun. Both objects are only detected in the SDSS z-band which is typical of nearby late-T dwarfs.” says Scholz.

Because the pair were optically visible at the time of the discovery, the team employed the Large Binocular Telescope (LBT) in Arizona to determine their spectral type and home in more accurately on their distance. They wanted to know more about the coolest representatives of T-type brown dwarf – the ultra-cool ones. Better known as failed stars because they lacked the mass to ignite nuclear fusion, the duo required study because their magnitude decreases sharply with time. Because they fade so quickly, there’s a strong possibility of a brown dwarf being much closer than we realize.

Like maybe next door…

[Paul Gilster] gives some Sci Fi refs to Neptune and a short H.G. Wells story

H.G. Wells » The Star

<<Simultaneously from three observatories, that the motion of the planet Neptune, the outermost of all the planets that wheel about the sun, had become very erratic. Ogilvy had already called attention to a suspected retardation in its velocity in December. Such a piece of news was scarcely calculated to interest a world the greater portion of whose inhabitants were unaware of the existence of the planet Neptune, nor outside the astronomical profession did the subsequent discovery of a faint remote speck of light in the region of the perturbed planet cause any very great excitement. Scientific people, however, found the intelligence remarkable enough, even before it became known that the new body was rapidly growing larger and brighter, that its motion was quite different from the orderly progress of the planets, and that the deflection of Neptune and its satellite was becoming now of an unprecedented kind.
......................................................
Neptune it was, had been struck, fairly and squarely, by the strange planet from outer space and the heat of the concussion had incontinently turned two solid globes into one vast mass of incandescence. Round the world that day, two hours before the dawn, went the pallid great white star, fading only as it sank westward and the sun mounted above it. Everywhere men marvelled at it, but of all those who saw it none could have marvelled more than those sailors, habitual watchers of the stars, who far away at sea had heard nothing of its advent and saw it now rise like a pigmy moon and climb zenithward and hang overhead and sink westward with the passing of the night.
......................................................
The star grew--it grew with a terrible steadiness hour after hour, a little larger each hour, a little nearer the midnight zenith, and brighter and brighter, until it had turned night into a second day. Had it come straight to the earth instead of in a curved path, had it lost no velocity to Jupiter, it must have leapt the intervening gulf in a day, but as it was it took five days altogether to come by our planet. The next night it had become a third the size of the moon before it set to English eyes, and the thaw was assured. It rose over America near the size of the moon, but blinding white to look at, and hot; and a breath of hot wind blew now with its rising and gathering strength, and in Virginia, and Brazil, and down the St. Lawrence valley, it shone intermittently through a driving reek of thunder-clouds, flickering violet lightning, and hail unprecedented. In Manitoba was a thaw and devastating floods. And upon all the mountains of the earth the snow and ice began to melt that night, and all the rivers coming out of high country flowed thick and turbid, and soon--in their upper reaches --with swirling trees and the bodies of beasts and men. They rose steadily, steadily in the ghostly brilliance, and came trickling over their banks at last, behind the flying population of their valleys.

And along the coast of Argentina and up the South Atlantic the tides were higher than had ever been in the memory of man, and the storms drove the waters in many cases scores of miles inland, drowning whole cities. And so great grew the heat during the night that the rising of the sun was like the coming of a shadow. The earthquakes began and grew until all down America from the Arctic Circle to Cape Horn, hillsides were sliding, fissures were opening, and houses and walls crumbling to destruction. The whole side of Cotopaxi slipped out in one vast convulsion, and a tumult of lava poured out so high and broad and swift and liquid that in one day it reached the sea.

So the star, with the wan moon in its wake, marched across the Pacific, trailed the thunderstorms like the hem of a robe, and the growing tidal wave that toiled behind it, frothing and eager, poured over island and island and swept them clear of men. Until that wave came at last--in a blinding light and with the breath of a furnace, swift and terrible it came--a wall of water, fifty feet high, roaring hungrily, upon the long coasts of Asia, and swept inland across the plains of China. For a space the star, hotter now and larger and brighter than the sun in its strength, showed with pitiless brilliance the wide and populous country; towns and villages with their pagodas and trees, roads, wide cultivated fields, millions of sleepless people staring in helpless terror at the incandescent sky; and then, low and growing, came the murmur of the flood. And thus it was with millions of men that night--a flight nowhither, with limbs heavy with heat and breath fierce and scant, and the flood like a wall swift and white behind. And then death.

China was lit glowing white, but over Japan and Java and all the islands of Eastern Asia the great star was a ball of dull red fire because of the steam and smoke and ashes the volcanoes were spouting forth to salute its coming. Above was the lava, hot gases and ash, and below the seething floods, and the whole earth swayed and rumbled with the earthquake shocks. Soon the immemorial snows of Thibet and the Himalaya were melting and pouring down by ten million deepening converging channels upon the plains of Burmah and Hindostan. The tangled summits of the Indian jungles were aflame in a thousand places, and below the hurrying waters around the stems were dark objects that still struggled feebly and reflected the blood-red tongues of fire. And in a rudderless confusion a multitude of men and women fled down the broad river-ways to that one last hope of men--the open sea.

Larger grew the star, and larger, hotter, and brighter with a terrible swiftness now. The tropical ocean had lost its phosphorescence, and the whirling steam rose in ghostly wreaths from the black waves that plunged incessantly, speckled with storm-tossed ships.

And then came a wonder. It seemed to those who in Europe watched for the rising of the star that the world must have ceased its rotation. In a thousand open spaces of down and upland the people who had fled thither from the floods and the falling houses and sliding slopes of hill watched for that rising in vain. Hour followed hour through a terrible suspense, and the star rose not. Once again men set their eyes upon the old constellations they had counted lost to them forever. In England it was hot and clear overhead, though the ground quivered perpetually, but in the tropics, Sirius and Capella and Aldebaran showed through a veil of steam. And when at last the great star rose near ten hours late, the sun rose close upon it, and in the centre of its white heart was a disc of black.

Over Asia it was the star had begun to fall behind the movement of the sky, and then suddenly, as it hung over India, its light had been veiled. All the plain of India from the mouth of the Indus to the mouths of the Ganges was a shallow waste of shining water that night, out of which rose temples and palaces, mounds and hills, black with people. Every minaret was a clustering mass of people, who fell one by one into the turbid waters, as heat and terror overcame them. The whole land seemed a-wailing and suddenly there swept a shadow across that furnace of despair, and a breath of cold wind, and a gathering of clouds, out of the cooling air. Men looking up, near blinded, at the star, saw that a black disc was creeping across the light. It was the moon, coming between the star and the earth. And even as men cried to God at this respite, out of the East with a strange inexplicable swiftness sprang the sun. And then star, sun and moon rushed together across the heavens.

So it was that presently, to the European watchers, star and sun rose close upon each other, drove headlong for a space and then slower, and at last came to rest, star and sun merged into one glare of flame at the zenith of the sky. The moon no longer eclipsed the star but was lost to sight in the brilliance of the sky. And though those who were still alive regarded it for the most part with that dull stupidity that hunger, fatigue, heat and despair engender, there were still men who could perceive the meaning of these signs. Star and earth had been at their nearest, had swung about one another, and the star had passed. Already it was receding, swifter and swifter, in the last stage of its headlong journey downward into the sun.

And then the clouds gathered, blotting out the vision of the sky, the thunder and lightning wove a garment round the world; all over the earth was such a downpour of rain as men had never before seen, and where the volcanoes flared red against the cloud canopy there descended torrents of mud. Everywhere the waters were pouring off the land, leaving mud-silted ruins, and the earth littered like a storm-worn beach with all that had floated, and the dead bodies of the men and brutes, its children. For days the water streamed off the land, sweeping away soil and trees and houses in the way, and piling huge dykes and scooping out Titanic gullies over the country side. Those were the days of darkness that followed the star and the heat. All through them, and for many weeks and months, the earthquakes continued.

But the star had passed, and men, hunger-driven and gathering courage only slowly, might creep back to their ruined cities, buried granaries, and sodden fields. Such few ships as had escaped the storms of that time came stunned and shattered and sounding their way cautiously through the new marks and shoals of once familiar ports. And as the storms subsided men perceived that everywhere the days were hotter than of yore, and the sun larger, and the moon, shrunk to a third of its former size, took now fourscore days between its new and new.

But of the new brotherhood that grew presently among men, of the saving of laws and books and machines, of the strange change that had come over Iceland and Greenland and the shores of Baffin's Bay, so that the sailors coming there presently found them green and gracious, and could scarce believe their eyes, this story does not tell. Nor of the movement of mankind now that the earth was hotter, northward and southward towards the poles of the earth. It concerns itself only with the coming and the passing of the Star.

The Martian astronomers--for there are astronomers on Mars, although they are very different beings from men--were naturally profoundly interested by these things. They saw them from their own standpoint of course. "Considering the mass and temperature of the missile that was flung through our solar system into the sun," one wrote, "it is astonishing what a little damage the earth, which it missed so narrowly, has sustained. All the familiar continental markings and the masses of the seas remain intact, and indeed the only difference seems to be a shrinkage of the white discoloration (supposed to be frozen water) round either pole." Which only shows how small the vastest of human catastrophes may seem, at a distance of a few million miles.>>

[Ann]

neufer wrote:

I, myself, would have said something about the angular momentum around the center of gravity being negligible but that's probably not the simplest way to explain it to a non-physicist type.

That's me!

Ann

[Beyond]

In the information brought up through the Rigel Kentaurus link it states "Rigel Kentaurus is the 3rd brightest star in the sky". However, in the explanation to the APOD it states it is the "fourth bightest star in the night sky". I would be grateful if someone could please let me know which is correct. Thanks.

PS. There should be a Clark Kentaurus star (perhaps there is!).

What a Super idea I don't know how i missed this post almost a year ago. Must have went by me like a speeding bullet.