APOD: Where is HD 189733? (2008 Mar 21)

Comments and questions about the APOD on the main view screen.

APOD: Where is HD 189733? (2008 Mar 21)

Postby Arramon » Fri Mar 21, 2008 6:05 am

Where is..? car54..? oh.. hd178334? no wait.. 896? (21Mar08)
oh yeah... hd189733..cygnus constellation... what was i thinking... =b

http://apod.nasa.gov/apod/ap080321.html

Image

That is so awesome we can measure that planets orbit other stars and can then actually analyze the atmospheres to see if its livable.

:twisted: muahaha...


:shock: they have been watching us.... d'oh!
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Postby orin stepanek » Fri Mar 21, 2008 12:51 pm

It is hard to imagine a planet orbiting in 2.2 days. It takes the moon almost a month and it is only a quarter of a million miles from Earth. That planet must be really moving. :wink:
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Postby neufer » Fri Mar 21, 2008 1:01 pm

orin stepanek wrote:It is hard to imagine a planet orbiting in 2.2 days. It takes the moon almost a month and it is only a quarter of a million miles from Earth. That planet must be really moving. :wink:
Orin

Anything orbiting that fast is also sun synchronous so the temperatures on the dark side might be somewhat tolerable for life.
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Postby Arramon » Fri Mar 21, 2008 3:19 pm

dang... stuck in darkness. then again, you'd have ultimate energy source just around the corner. =)

and could then make some artificial sunlight hours to turn your nights into days, then click it off to go to bed. =b
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Postby iamlucky13 » Fri Mar 21, 2008 5:13 pm

neufer wrote:
orin stepanek wrote:It is hard to imagine a planet orbiting in 2.2 days. It takes the moon almost a month and it is only a quarter of a million miles from Earth. That planet must be really moving. :wink:
Orin

Anything orbiting that fast is also sun synchronous so the temperatures on the dark side might be somewhat tolerable for life.

There would probably be a really strong wind carrying heat around from the light side to the dark side, however. The temperature might still be reasonable, but the wind would be.
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planet

Postby ta152h0 » Sat Mar 22, 2008 8:23 pm

How do you know if there is only one planet ? and how do you know they are not evenly spread, if so ? pass the beer :shock:
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Re: planet

Postby neufer » Sat Mar 22, 2008 9:30 pm

ta152h0 wrote:How do you know if there is only one planet ? and how do you know they are not evenly spread, if so ? pass the beer :shock:

----------------------------
Counter-Earth From Wikipedia

<<The Counter-Earth is a hypothetical body of the Solar system first hypothesized by the presocratic philosopher Philolaus to support his non-geocentric cosmology, in which all objects in the universe revolve around a Central Fire. The Greek word "Antichthon" means "Counter-Earth."

By 500 BC most contemporary philosophers considered the Earth to be spherical - there was obvious evidence for this from the behaviour of objects near the horizon. This meant that all objects on the surface of the Earth had to be attracted to its centre in some way, otherwise they would fall off. It also required other objects, such as the stars and planets, to float above the earth in relation to its centre, otherwise they would presumably move rapidly away. This argument - reasonable in view of the data available at the time - resulted in a geocentric world view.

When the movements of celestial objects convinced Philolaus that the world must be not only turning on its own axis but revolving around a fixed point elsewhere in space, he was faced with the problem of explaining how a spherical world could move in this way without spilling everything on the surface into space. He came to the conclusion that the directions of up and down do not exist in space, except in that all things must fall towards the center of the universe, around which all things (including the Earth, Sun, and all the planets) must revolve. Our earth must be a practically flat world and the underside of our Earth must face this fiery, central point at all times, otherwise we would fall off.

This created a contradiction within the Pythagorean school of thought. Since planets, in their understanding, were composed of a fiery or ethereal matter having little or no density, they could quite easily rotate eccentric to the Earth without becoming off balance. However, the Earth was obviously made of the dense elements of Earth and Water. If there were a single Earth revolving at some distance from the center of space, the universe's center of balance would not coincide with its spatial center. Since this is the point towards which things fall, the earth must have a counter-balance of the same mass or the universe would be flung apart. This problem led Philolaus to develop idea of a Counter-Earth, a second, flat Earth, identical but opposite to ours in every way. This conception of the solar system is outlined in the diagram at the right, with Counter-Earth referred to as Antichthon. The upper illustration depicts Earth at night while the lower one depicts Earth in the day. (In order to prevent confusion it should be noted that the diagram fails to show that Earth and Counter-Earth are flat and point away from the Central Fire). It is likely that Philolaus believed that the whole orbit of Earth was composed of an ethereal sphere, with the Earth and Counter-Earth being local dense points on the surface.

This theory is a very creditable attempt to incorporate all known cosmological data at the time, and indicates the sophistication of Classical Greek thinking. The ideas of a flat earth, Counter-Earth, and Central Fire were all eventually superseded by the theory of Gravitation which is currently held by the scientific community, that describes a spherical earth rotating around both its own axis and the sun. The Counter-Earth is still a popular motif in science fiction and fantasy writing today, usually serving as an allegory for the real Earth.

In the 1st century A.D., after the idea of a spherical Earth superseded the original Counter-Earth theory, Pomponius Mela, a Latin cosmographer, developed an updated version of the idea, wherein a spherical Earth must have a more or less balanced distribution of land and water. Mela drew the first map on which the mysterious continent of Earth appears in the unknown half of Earth - our antipodes. This continent he inscribed with the name Antichthones.

Scientific analysis

If such a planet actually existed in our current scientific cosmology, as a spherical world that revolved around the sun, it would be permanently hidden behind the sun but nevertheless detectable from Earth, because of its gravitational influence upon the other planets of the Solar System. No such influence has been detected, and indeed space probes sent to Venus, Mars and other places could not have successfully flown by or landed on their targets if a Counter-Earth existed, as it was not accounted for in navigational calculation.

The Sun-Jupiter Trojan asteroid system is an example of a stable Lagrange orbit. However, these linear orbits are not as stable as, for example, the equilateral Lagrange orbits L4 and L5. Hilda asteroids do not visit L3 of Jupiter-Sun system, though they do come close to it in their curious orbits.

Greek Mythology

According to some Greek Mythology, Antichthon was placed between Earth and the center of the universe, the throne of Zeus, to stop man from looking at God directly.>>
------------------------------
Doppelgänger (1969 film)

<<Doppelgänger was a 1969 British science fiction film directed by Robert Parrish. The film was released in the US as Journey to the Far Side of the Sun. The crew of a spacecraft journey to a previously unknown planet far side of the Sun, only to seemingly find themselves returning back to the Earth. The storyline is extremely similar to an hour-long episode of the Twilight Zone entitled, The Parallel.

The film begins with the discovery of an unknown planet orbiting exactly the opposite side of the Sun from Earth (an idea reminiscent of the Antichthon or Counter-Earth proposed by Philolaus in the fifth century B.C). The European Space Exploration Council (EUROSEC) and NASA send British astrophysicist John Kane (Ian Hendry) and American astronaut Col. Glenn Ross (Roy Thinnes) to the new planet in a rocket which resembles a Saturn 5 rocket.

During their long voyage, they are put into hibernation, and are maintained by a pair of on board Heart/Lung/Kidney machines, meaning that they will have no recollection of the journey. When they awaken, they enter orbit of the planet and do an initial survey. They find the planet's atmosphere to be breathable but they see no signs of life. They decide to go forward with a landing. They suit up, and go through an access tunnel to reach their lifting body lander which slides out the rear of the mother ship.

As they enter the atmosphere, the ship's controls begin to short out and malfunction. They lose all control of the craft, which clips a mountaintop before crashing into rocky terrain. After the crew is clear of the burning wreckage, a suited figure picks them up into a hovering unfamiliar ship.

They find they have been taken aboard an air-sea rescue craft. It appears that the crew have somehow returned to Earth instead of going to the planet. They are discreetly returned to the space center, with Kane in critical condition. He later dies of his injuries.

Ross is grilled by EUROSEC officials who accuse him of aborting the mission. Ross denies turning back, saying he and Kane actually arrived at the new planet, and could not explain why he is now on Earth.

Soon, Ross puts together the shocking fact that he is not on Earth at all - but on the planet, which is an identical Earth where everything is a mirror image of our own. At first, his own wife Sharon (Lynn Loring) and others at the space agency think he is insane for claiming signs and even the layout of his apartment on the spaceport's base are backwards, but he convinces the director of EUROSEC, Jason Webb (Patrick Wymark) that it is true by easily reading documents and written directions shown as a reflection in a mirror. Ross theorizes that everything that is done on his Earth is done on the planet at the same time, but opposite to it. If he tries to go back, he will return as if nothing happened.

Concern over whether the duplicate shuttle craft he and Kane used to come to Earth from the spaceship share the same electrical charge is raised, but Ross decides to try. He takes off in a shuttle he has named "DOPPELGANGER," meaning "double," (written in our manner of left to right) to dock with the Earth ship he came in to retrieve its flight recorder. But as he docks, the electrical systems short out -- they were wrong, the polarity of electricity is the same on both worlds. He loses contact with the ground base, and his shuttle craft undocks from the ship, hurtling towards the ground with the automatic approach system locked on. This locks out his controls resulting him having no flight control as he decends into the atmosphere. When ground control realizes his situation, they disengage the system, but too late, resulting in the shuttle crashing into a second mission rocket. He is killed instantly and the crash causes a chain reaction of explosions destroying the space center in a style typical of Gerry Anderson production.

The final scene shows an elderly Webb, long ago dismissed as head of the space agency, institutionalized and telling the staff there about what had happened (the disaster had destroyed all evidence). In his dementia, he sees his reflection in a mirror mounted in front of a window, and in an attempt to touch his mirror self, crashes through the mirror and window to fall to his death.>>
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Postby astrolabe » Mon Mar 24, 2008 1:28 am

The comedian, Father Guido Sarducci, alluded to the dual Earth idea in one of his monologues and mentioned that the two Earths were identical in every respect save one: the people on the "other" Earth ate their corn-on-the-cob vertically.
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moving over

Postby ta152h0 » Mon Mar 24, 2008 1:37 am

i have no idea how ya'll went from what i said to what you are saying :D
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Postby kovil » Mon Mar 24, 2008 11:10 am

They are playing 'pass the cold one' !
It's like a whisper traveling around the campfire.

Nice to see you back, Wolf.

Firesign Theater did something on this didn't they?
something about animals without backbones sitting up, but then they fell over.

Interesting how our sense of ourself and our planet, changes over the millenia.

I still enjoy the film 'Contact' in the ending's voyage to distant places, and how that new perspective gives one pause to see things differently.
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Re: moving over

Postby Arramon » Mon Mar 24, 2008 5:17 pm

ta152h0 wrote:i have no idea how ya'll went from what i said to what you are saying :D


How do scientists know if there are more planets around that star, and at which distances they may be orbitting?

There probably are more planets in that system, the one they are referring to is probably the easiest to pinpoint since its the closet to the parent star, and does the whole 'pass infront of the star and block the light' deal many many times sooner than the other possible planets that take much longer to orbit.

I just wonder if being so close to the star makes the wobble of that star from the fast orbitting planet more or less evident compared to planets that may be bigger yet further away, and taking longer to possibly cross infront of the star's light (transit).

Also, even with the planet so close, couldn't the rotation still occur? Possibly in reverse, or whatnot. Or would the closeness to a parent star, or a moon to its parent planet, really only cause a sun synchronous orbit.
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Re: moving over

Postby neufer » Mon Mar 24, 2008 7:21 pm

Arramon wrote:even with the planet so close, couldn't the rotation still occur? Possibly in reverse, or whatnot. Or would the closeness to a parent star, or a moon to its parent planet, really only cause a sun synchronous orbit.

A small close planet like Mercury may have a large enough elliptical orbit that it is ONLY "sun synchronous" during its perihelion phase where the tidal forces are the greatest.

It would then be allowed to rotate an additional "N" half rotations out at aphelion:

Image
http://www.youtube.com/watch?v=zAlfJc2FqMQ

A large close planet would, itself, kick up such a tide on it's sun during perihelion that it would quickly transform into a circular sun synchronous orbit.
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Postby Arramon » Mon Mar 24, 2008 7:30 pm

So then the proximity of the planet to the sun is just causing it to be whipped around the sun at all times. =)

Making the object keep the same face towards the pull of the sun, like it were tethered as in the video. I've never been on that ride before. =/

Alittle different than the tilt-a-whirl... =b
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Postby neufer » Mon Mar 24, 2008 8:00 pm

Arramon wrote:So then the proximity of the planet to the sun is just causing it to be whipped around the sun at all times. =)

Making the object keep the same face towards the pull of the sun, like it were tethered as in the video. I've never been on that ride before. =/

A little different than the tilt-a-whirl... =b

Right! That would be Hyperion: http://antwrp.gsfc.nasa.gov/apod/ap070128.html
http://en.wikipedia.org/wiki/Hyperion_(moon)

<<Physicists Bret M. Huggard and Richard L. Kautz came up with a mathematical equation that approximates the motion of the Tilt-A-Whirl. Although it was without knowledge of chaos theory that Herbert Sellner invented the ride, in his patent text he clearly demonstrates an appreciation of chaos -- "A further object is to provide amusement apparatus wherein the riders will be moved in general through an orbit and will unexpectedly swing, snap from side to side or rotate without in any way being able to figure what movement may next take place in the car.">>
-----------------------------------------
HAMLET: See, what a grace was seated on this brow; Hyperion's curls:
......................................
<<Herbert Sellner, a woodworker and maker of water slides, invented the Tilt-A-Whirl in 1926, at his Faribault, Minnesota, home. Family legend states that Herbert experimented with a chair placed on the kitchen table. Herbert's son

Art sat in the chair, and Herbert rocked the table back and forth.>> - Wikipedia
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is it possible

Postby ta152h0 » Mon Mar 24, 2008 9:25 pm

Is it possible a train of planets transit in the same orbit giving the illusion of only 2.2 days per orbit ? :idea:
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Re: is it possible

Postby neufer » Mon Mar 24, 2008 10:14 pm

ta152h0 wrote:Is it possible a train of planets transit in the same orbit giving the illusion of only 2.2 days per orbit ? :idea:

You seem to have a problem with the idea of orbits as short as 2.2 days
2.2 hours might be a real problem...but NOT 2.2 days.

At least, Jonathan Swift didn't shy away from such ideas:
---------------------------------
<<The existence of two fictional Martian moons was described in Jonathan Swift's satirical novel Gulliver's Travels, published in 1726, 150 years before their discovery: They [the Laputan astronomers] have likewise discovered two lesser stars, or 'satellites', which revolve about Mars, whereof the innermost is distant from the centre of the primary planet exactly three of his diameters, and the outermost five; the former revolves in the space of ten hours, and the latter in twenty-one and a half...

Phobos and Deimos are in fact about 1.4 and 3.5 diameters from Mars' centre, and their periods are 7.7 and 30.3 hours, respectively. A similar "discovery" was described by Voltaire in his interplanetary romance Micromegas, published in 1752.>>
- http://en.wikipedia.org/wiki/Moons_of_Mars
---------------------------------
In fact. there are a whole host of planetary moons with orbits less than 3 days
none of which involve moons of the same size equally spaced in the same orbit:
Code: Select all
_________     Orbital Period in days   & inclination
-------------------------------------------------------
1    Neptune III    Naiad        0.294    4.7°
2    Neptune IV    Thalassa    0.311    0.2°
3    Neptune V    Despina    0.335    0.1°
4    Neptune VI    Galatea    0.429    0.1°
5    Neptune VII    Larissa    0.555    0.2°
6    Neptune VIII    Proteus    1.122    0.6°

1    Uranus VI    Cordelia    0.335034    0.08479°
2    Uranus VII    Ophelia    0.376400    0.1036°
3    Uranus VIII    Bianca       0.434579    0.193°
4    Uranus IX    Cressida    0.463570    0.006°
5    Uranus X    Desdemona    0.473650    0.11125°
6    Uranus XI    Juliet       0.493065    0.065°
7    Uranus XII    Portia       0.513196    0.059°
8    Uranus XIII    Rosalind    0.558460    0.279°
9    Uranus XXVII    Cupid       0.618       0.1°
10    Uranus XIV    Belinda    0.623527    0.031°
11    Uranus XXV    Perdita    0.638       0.0°
12    Uranus XV    Puck       0.761833    0.3192°
13    Uranus XXVI    Mab       0.923       0.1335°
14    Uranus V    Miranda    1.413479    4.232°
15    Uranus I    Ariel       2.520379    0.260°
---------------------------------
1    Saturn XVIII    Pan       +0.57505    0.001°    in Encke Division
2    Saturn XXXV    Daphnis    +0.59408    ≈ 0°    in Keeler Gap    
3    Saturn XV    Atlas       +0.60169    0.003°    outer A Ring shepherd
4    Saturn XVI    Prometheus    +0.61299    0.008°    inner F Ring shepherd
5    Saturn XVII    Pandora    +0.62850    0.050°    outer F Ring Shepherd

6    Saturn XI    Epimetheus    +0.69433    0.335°    co-orbitals
7    Saturn X    Janus       +0.69466    0.165°    co-orbitals

8    Saturn I    Mimas       +0.942422    1.566°
9    Saturn XXXII    Methone    +1.00957    0.007°   
10    Saturn XLIX    Anthe       +1.03650    0.1°
11    Saturn XXXIII    Pallene    +1.15375    0.181°
12    Saturn II    Enceladus    +1.370218    0.010°    In the thick of E ring

13    Saturn III    Tethys       +1.887802    0.168°
13a    Saturn XIII    Telesto    leading Tethys trojan
13b    Saturn XIV    Calypso    trailing Tethys trojan

16    Saturn IV    Dione       +2.736915    0.002°
16a    Saturn XII    Helene       leading Dione trojan
16b    Saturn XXXIV    Polydeuces    trailing Dione trojan
---------------------------------
1    Jupiter XVI    Metis       +7h 4m 29s       0.06°
2    Jupiter XV    Adrastea    +7h 9m 30s       0.03°
3    Jupiter V    Amalthea    +11h 57m 22.67s      0.374°
4    Jupiter XIV    Thebe       +16h 11m 17s       1.076°
5    Jupiter I    Io       +1.769137786       0.050°
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Postby Arramon » Tue Mar 25, 2008 6:12 pm

I guess it really depends on insertion of the satellite to it's parent. It could be speeding pass the parent then get caught in its gravitational pull, causing a quicker orbit, or it could be a lazy bugger just drifting along and after being caught in the pull of the parent, a slower more casual orbit occurs.

I wonder if the satellites themselves can alter eachother's orbits if they are close enough, or if their orbits cross somehow as they cruise around the parent object.

What about the rotational period of the parent object? Could that cause an orbittal period of a satellite to become altered based on the spin of the parent?

hmmmmmmmmmmm
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Postby bystander » Tue Mar 25, 2008 6:28 pm

The more massive the satellite and/or the closer the orbit, the faster the orbit.
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Re: is it possible

Postby iampete » Tue Mar 25, 2008 6:29 pm

neufer wrote:
ta152h0 wrote:Is it possible a train of planets transit in the same orbit giving the illusion of only 2.2 days per orbit ? :idea:
. . .

none of which involve moons of the same size equally spaced in the same orbit . . .


To a first order, one could consider a single Saturnian ring being a "train of satellites" of roughly equal size in the same orbit. The physics obviously works for very large numbers. Is there a reason why it wouldn't work for much smaller numbers? Or a reason why it wouldn't work for planets around a star? What are the limiting factors?

Not arguing that ta152h0's scenario is even remotely likely, but curious about "possible".
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Postby neufer » Tue Mar 25, 2008 6:40 pm

Arramon wrote:What about the rotational period of the parent object? Could that cause an orbittal period of a satellite to become altered based on the spin of the parent?

-----------------------------------
http://www.astronomynotes.com/gravappl/s10.htm

Tides Slow Earth Rotation

<<As the Earth rotates beneath the tidal bulges, it attempts to drag the bulges along with it. A large amount of friction is produced which slows down the Earth's spin. The day has been getting longer and longer by about 0.0016 seconds each century.

Over the course of time this friction can have a noticeable effect. Astronomers trying to compare ancient solar eclipse records with their predictions found that they were off by a significant amount. But when they took the slowing down of the Earth's rotation into account, their predictions agreed with the solar eclipse records. Also, growth rings in ancient corals about 400 hundred million years old show that the day was only 22 hours long so that there were over 400 days in a year. In July 1996 a research study reported evidence, from several sedimentary rock records providing an indicator of tidal periods, that the day was only 18 hours long 900 million years ago.

Eventually the Earth's rotation will slow down to where it keeps only one face toward the Moon. Gravity acts both ways so the Earth has been creating tidal bulges on the Moon and has slowed it's rotation down so much that it rotates once every orbital period. The Moon keeps one face always toward the Earth.>>

Image
-----------------------------------
Tides slow Earth's rotation and enlarge Moon's orbit

Tides Enlarge Moon Orbit

<<Friction with the ocean beds drags the tidal bulges eastward out of a direct Earth-Moon line and since these bulges contain a lot of mass, their gravity pulls the moon forward in its orbit. The increase in speed enlarges the Moon's orbit. Currently, the Moon's distance from the Earth is increasing by about 3 centimeters per year. Astronomers have been able to measure this slow spiralling out of the Moon by bouncing laser beams off reflectors left by the Apollo astronauts on the lunar surface.

The consequence of the Moon's recession from the Earth because of the slowing down of the Earth's rotation is also an example of the conservation of angular momentum. Angular momentum is the amount of spin motion an object or group of objects has. It depends on the geometric size of the object or group of objects, how fast the object (or group of objects) is moving, and the mass of the object (or the group). Since the Earth's angular momentum is decreasing, the Moon's angular momentum must increase to keep the overall angular momentum of the Earth-Moon system the same. The concept of angular momentum is discussed further in the Angular Momentum appendix.

The slow spiralling out of the Moon means that there will come a time in the future when the angular size of the Moon will be smaller than the Sun's and we will not have any more total solar eclipses! Fifty billion years in the future the Earth day will equal 47 of our current days and the Moon will take 47 of our current days to orbit the Earth. Both will be locked with only one side facing the other---people on one side of the Earth will always see the Moon while people on the other side will only have legends about the Moon that left their pleasant sky.>>
-----------------------------------
Tidal Effects Elsewhere

<<Tidal effects are larger for more massive objects and at closer distances. The Sun produces a tidal bulge on the planet Mercury (the planet closest to the Sun) and has slowed that planet's rotation period so it rotates three times for every two times it orbits the Sun (a ``3 - 2 spin-orbit resonance''). Jupiter's moon, Io, orbits at about the same distance from Jupiter's center as the Earth's moon. Jupiter is much more massive than the Earth, so Jupiter's tidal effect on Io is much greater than the Earth's tidal effect on the Moon. Io is stretched by varying amounts as it orbits Jupiter in its elliptical orbit. This tidal flexing of the rock material creates huge amounts of heat from friction in Io's interior which in turn is released in many volcanic eruptions seen on Io. Galaxies passing close to each other can be severely stretched and sometimes pulled apart by mutual tidal effects.>>
-----------------------------------
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Gateway to Understanding Evolution of Planetary Systems

Postby bystander » Tue Jan 11, 2011 6:13 pm

Discovery Opens Gateway to Understanding Evolution of Planetary Systems
Villanova University | 2011 Jan 11
The discovery of a Hot Jupiter exoplanet that transfers orbital momentum to its host star may hold the key to a clearer understanding of the evolution of common planetary systems, according to findings presented today by Dr. Edward Guinan, a professor of astronomy at Villanova University in Villanova, Pa. Guinan announced the find at a press conference held at the opening of the 217th American Astronomy Society meeting in Seattle, Washington. The discovery is of special interest because it represents a rare case in which a research team was able to make an independent age determination of the planet system by studying the system’s faint red dwarf companion star. The discovery opens a new gateway to learning about the dynamics and evolution of many other planetary systems that also contain close-in hot-Jupiter type planets.

HD189733b, the Hot Jupiter exoplanet, orbits an orange (dwarf K) star HD18973A in the constellation Vulpecula (the Fox). It orbits at only three percent of the distance of the Earth from the Sun: i.e. ~0.03 AU) with an orbital period of only 2.2 days (for comparison the Earth takes 365 days to orbit our Sun). The host star is about 63 light-years away and has a mass and diameter about ~80 percent that of our Sun. This star, invigorated by its hot Jupiter planetary companion, appears to have been spun up (rotating ~ >2x faster than our Sun – having a ~12-day rotation period) and is gaining angular momentum from magnetic and tidal interactions with its close-in Jupiter-size planet. The star, however, is being spun-up at the expense of the planet’s orbital angular energy.

The loss in the planet’s orbital momentum in the past may explain why it (and other similar planetary systems) orbit so close to their host stars. While the planet is spiraling in toward the star, and is most likely doomed, there is a possibility that the interacting magnetic fields of the star and planet could create a tidal-magnetically locked orbit rotation that might allow the planet to survive. The most likely scenario, however, is that the planet will draw closer to the star and its atmosphere will be eroded away by the star’s intense radiation and strong winds. The planet will ultimately be ripped apart by the star’s gravity if it survives the star’s radiation and winds.

HD 189733 Ab is a relatively rare eclipsing planetary system that was discovered in 2005 (by Buchy et al.) and has attracted much attention in astronomical circles because it hosts a transiting Hot Jupiter exoplanet. The system is relatively bright (e.g. can be seen with binoculars). The eclipses by the planet permit substantial information to be gained from observing the system inside and outside the planetary eclipses. For example, spectroscopic studies by other teams (e.g. G. Tinnetti et al.) reveal that its hot atmosphere contains water vapor, carbon dioxide, sodium, and, interestingly, organic molecules of methane and particulate haze.

The Villanova team, which includes undergraduates Thomas Santapaga and Ronald Ballouz, found that this system is about over five billion years old and that the Jupiter-size planet has been estimated to be very hot at ~1,500 degrees Fahrenheit by other researchers. HD189733b has one of the shortest known orbital periods of only P = 2.22 days and is only 0.031AU from its host star (i.e. only ~8.75x the radius of the host star). The exoplanet system includes a cool red dwarf companion star (HD 189733B). This faint companion star is located at ~12” distance to the K-dwarf. At the distance of HD 189733 this corresponds to a separation of ~220 AU/ For comparison this 220x the distance of the Earth from the Sun / or over 5.5x further than the distance of Pluto from the Sun.) The presence of this red dwarf star makes a reliable age estimate of the binary system possible via activity-age relations developed at Villanova.

“Planetary systems like HD 189733 with short period, “hot-Jupiter” planets are very common – over a hundred have been discovered so far,” Guinan noted. He continued, “HD 189733 and dozens of other planetary systems like it, many of which were recently discovered by NASA’s Kepler mission, may also be undergoing the same process of strong magnetic interactions between their close-in large planets and their host stars.”

“The big clue that is different here is that we know the age of HD 189733 from the study of its coeval faint companion star.” This discovery should help in our endeavors to try to better understand the dynamics of other planetary systems like HD 189733, he added.”

Of the over 500 exoplanets that have been discovered to date, HD 189733 is the only one of a handful whose age and physical properties have been well determined.

“This study may help explain how and why hot Jupiters form and evolve. It may help explain this whole class of planets,” Guinan remarked.

In conducting this study the research team, which includes Villanovans Thomas Santapaga, Ronald L. Ballouz, Scott E. Engle, Laurence E. DeWarf, along with Styliani (Stella) Kafka from the Carnegie Institute in Washington, D.C.’s Department of Terrestrial Magnetism, observed the exoplanet system using the Clay Telescope at the Carnegie Institution of Washington’s Las Campanas Observatory in Chile. Observations of the eclipse timings of HD 189733 continue at Villanova using the Four College Automatic Photoelectric Telescope (FCAPT) located in southern Arizona. The eclipse timings made with this telescope over time could provide evidence that the orbital period of the system is indeed decreasing.

The research project is funded through The National Science Foundation‘s Research at Undergraduate Institutions and grants from NASA.

Guinan’s Jan. 10 presentation of the team’s findings at the 217th AAS Meeting are from a paper titled, “Some Like It Hot” – Evidence for the Shrinking Orbit of the 2.2-day Transiting Hot Jupiter Exoplanet HD 189733b – Evidence of Transfer of Planet Orbital Momentum to its Host Star” (AAS 217th Meeting Abstract 343.12, P. 566).

“One of the most amazing results of our team’s research is that a planet-size body that is only 1/1000x times the mass of the host star can make such a large impact by magnetically interacting with its host star to the extent that it causes the star to spin up, activating a strong magnetic dynamo of the star that produces the observed strong X-ray coronal emissions, large starspots and other phenomena,” Guinan concluded.
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