Smallest Extra-Solar Planet Found

[zavvy]

<b>Smallest Extra-Solar Planet Found</b><br /><br />LINK<br /><br />US astronomers say they have found the smallest planet orbiting outside our Solar System to date. <br /><br />The new world, which is about one fifth the size of Pluto, is the fourth planet to be discovered orbiting around a pulsar called PSR B1257+12. <br /><br />A pulsar is a spinning neutron star producing powerful beams of radiation. <br /><br />The new planet is orbiting inside a large cloud of hot, charged gas that surrounds the pulsar and is some 1,500 light-years away from Earth. <br /><br />Details of the work were announced at an astronomy meeting held in Aspen, US. <br /><br />Pulsars are formed from the collapsed cores of so-called "supergiant" stars that have exploded. <br /><br />The discovery was made by Alex Wolszczan of Pennsylvania State University, US, and Maciej Konacki of the California Institute of Technology (Caltech). <br /><br />The orbit of the new planet is close to the average distance from our Sun to the asteroid belt. <br /><br />The orbits of three planets discovered orbiting the same pulsar in 1992 were almost in exact proportion to the spacings between Mercury, Venus and Earth. <br /><br />Wolszczan and Konacki say the new planet could mark the fringes of the pulsar's planetary system, just like Pluto marks the edge of ours. <br /><br />The new planet was discovered with the Arecibo radio telescope in Puerto Rico. <br /><br />

 

[astrophoto]

Ok so what method was used to discover this little guy? I can't imagine the wobble-method is precise enough for something that small, that far from the star. Was it directly measured with Arecibo or simply inferred? Sounds more like an asteroid than a planet to me.

 

[zavvy]

More info here..<br /><br />Home pages of the scientists involved, with contact details..<br /><br />http://www.astro.psu.edu/users/alex/<br /><br />http://www.gps.caltech.edu/~maciej/<br /><br />

 

[astrophoto]

Slightly off-topic, but something bothers me about this. A pulsar is thought to be the remnant of a super massive star explosion right? So either:<br /><br />1. These planets originally orbitted the star and survived the explosion. Wow.<br /><br />2. These planets were formed during/after the explosion. From material ejected from the star? Where else could the material come from? Nearby supernova?<br /><br />3. These planets were captured by the pulsar after the explosion. Not likely.<br /><br />4. There are no planets there and we just didn't realize pulsars weren't as perfect as we thought they were. Heck if I know.<br /><br />Any other ideas? None of the above are particularly comfortable to me and my rudimentary knowledge of planetary formation.

 

[qzzq]

Thanks zavvy. From your link: <ul type="square">These discoveries have been possible because pulsars, especially those with the fastest spin, behave like very accurate clocks. "The stability of the repetition rate of the pulsar pulses compares favorably with the precision of the best atomic clocks constructed by humans," Konacki explains. Measurements of the pulse arrival times, called pulsar timing, give astronomers an extremely precise method for studying the physics of pulsars and for detecting the phenomena that occur in a pulsar's environment.<br /><br />"A pulsar wobble due to orbiting planets manifests itself by variations in the pulse arrival times, just like a stellar wobble is detectable with the well-known Doppler effect so successfully used by optical astronomers to identify planets around nearby stars by the shifts of their spectral lines," Wolszczan explains. <b>"An important advantage of the fantastic stability of the pulsar clocks, which achieve precisions better than one millionth of a second, is that this method allows us to detect planets with masses all the way down to those of large asteroids."</b></ul><img src="/images/icons/cool.gif" /><br /><br /> <div class="Discussion_UserSignature"> <p> </p><p>***</p> </div>

 

[thalion]

The important thing to remember is that this is a millisecond pulsar. Millisecond pulsars are all "old": they (AFAIK) never connected with SN remnants, and even regular pulsars almost never rotate as rapidly as millisecond ones do. <br /><br />The current theory for the development of millisecond pulsars, is that they develop when one star in a binary system goes supernova, leaving a neutron-regular star pair. Material accreted from the other star either keeps the pulsar from spinning down as it usually would, or speeds it up from a previous slow state if there is a sudden increase in material (such as if the larger star becomes a giant).<br /><br />The accretion of the gas from the other star increases the pulsar's angular momentum, speeding it up. If the companion is a low-mass star, the intense radiation from the pulsar will literally slowly vaporize it. Check out the "Black Widow" pulsar:<br /><br />http://chandra.harvard.edu/photo/2003/b1957/closer_look.html<br /><br />http://astrosun2.astro.cornell.edu/academics/courses/astro201/puls_bwidow.htm<br /><br />Eventually, the companion may be completely destroyed. As for the pulsar planets, what they think happened is that the remnants of the companion star broke up into a ring around the pulsar, the debris of which was able to form a few planets before the remainder was presumably blown away.