Astronomy

[Dreamwoven]

I'm not convinced by the arguments in the link of the previous post. We all know that the larger the object the more likely it will capture meteorites, in part by its much greater gravitational pull. This is why the big outer planets have many moons and why Jupiter sucks to it larger meteorites. A small dwarf planet, without even a moon, will have a relatively quiet and calm history. Nothing strange about that.

[desiresjab]

What I most expect and predict as the connundrum is failure of the model to accurately reflect the personal history of each asteroid. No surprise at all, since their lives do not look to have been so quiet to me. Belts still have thickness. An interior portion is hit by less debris, certainly by fewer large chunks hurling in from outside the belt. This, as well, means fewer big collisions on these interior bodies of the belt. I have to assume these scientists are top guns and have already considered all this and more, which would make the solar flyby coming up quite exciting to them.

[Dreamwoven]

Here is a double-double star: http://earthsky.org/brightest-stars/...le-double-star

Apparently they can be seen with binoculars!

[YesNo]

I've noticed Vega before in the constellation Lyra, but I didn't realize there were double double stars like Epsilon Lyrae.

[Dreamwoven]

This item in EarthSky was published today: http://earthsky.org/space/star-lashe...th-mystery-ray.

No idea what they mean by pulsing neutron star.

[tailor STATELY]

Pulsar... https://en.wikipedia.org/wiki/Pulsar

[YesNo]

It puzzles me why the radiation is not global over the pulsar but localized like a light in a lighthouse that rotates the beam.

[Dreamwoven]

I am afraid I don't understand what pulsars are, and I have read the wikipedia item on it.

[tailor STATELY]

See the wiki picture of the magnetic alignment of the beam... then consider the misalignment theory (underlined below) (think wobble) that causes the pulse... rather than being exactly straight on, both magnetic and rotational axes perfectly in line with each other in direction, to the observer where the energy would be in constant view - which is theoretically possible for other systems.

"The events leading to the formation of a pulsar begin when the core of a massive star is compressed during a supernova, which collapses into a neutron star. The neutron star retains most of its angular momentum, and since it has only a tiny fraction of its progenitor's radius (and therefore its moment of inertia is sharply reduced), it is formed with very high rotation speed. A beam of radiation is emitted along the magnetic axis of the pulsar, which spins along with the rotation of the neutron star. The magnetic axis of the pulsar determines the direction of the electromagnetic beam, with the magnetic axis not necessarily being the same as its rotational axis. This misalignment causes the beam to be seen once for every rotation of the neutron star, which leads to the "pulsed" nature of its appearance. The beam originates from the rotational energy of the neutron star, which generates an electrical field from the movement of the very strong magnetic field, resulting in the acceleration of protons and electrons on the star surface and the creation of an electromagnetic beam emanating from the poles of the magnetic field."

Ta ! (short for tarradiddle),
tailor STATELY

[desiresjab]

See the wiki picture of the magnetic alignment of the beam... then consider the misalignment theory (underlined below) (think wobble) that causes the pulse... rather than being exactly straight on, both magnetic and rotational axes perfectly in line with each other in direction, to the observer where the energy would be in constant view - which is theoretically possible for other systems.

"The events leading to the formation of a pulsar begin when the core of a massive star is compressed during a supernova, which collapses into a neutron star. The neutron star retains most of its angular momentum, and since it has only a tiny fraction of its progenitor's radius (and therefore its moment of inertia is sharply reduced), it is formed with very high rotation speed. A beam of radiation is emitted along the magnetic axis of the pulsar, which spins along with the rotation of the neutron star. The magnetic axis of the pulsar determines the direction of the electromagnetic beam, with the magnetic axis not necessarily being the same as its rotational axis. This misalignment causes the beam to be seen once for every rotation of the neutron star, which leads to the "pulsed" nature of its appearance. The beam originates from the rotational energy of the neutron star, which generates an electrical field from the movement of the very strong magnetic field, resulting in the acceleration of protons and electrons on the star surface and the creation of an electromagnetic beam emanating from the poles of the magnetic field."

Ta ! (short for tarradiddle),
tailor STATELY

A good explanation. It is mere happenstance if their magnetic poles are at right angles to their spin, which is the only time we would see one of them appear to be on all the time, if the line through its magnetic poles pointed straight at us.

Concerning planets with molten magnetic cores, their spin has something to do with where the magnetic poles are, I believe. Probably no one knows why the magnetic poles are where they are in a pulsar. I do not anyway. Perhaps they are vestigial.

[Dreamwoven]

Thanks for that clear explanation, tailor. It was in the wikipedia item, but made much clearer by your description.

[desiresjab]

The revolutions per minute of most neutron stars being what they are, any with rpm faster than 30 per second will indeed appear to be on all the time to a naked eye through a telescope. Most spin many times that rate, requiring delicate instruments to determine there is a period at all.

[Dreamwoven]

This 5 minute video shows how difficult it was to land a rover (Curiosity) on the surface of a
Mars: http://earthsky.org/space/mars-curio...utes-of-terror so it was fit to explore.

[desiresjab]

This 5 minute video shows how difficult it was to land a rover (Curiosity) on the surface of a
Mars: http://earthsky.org/space/mars-curio...utes-of-terror so it was fit to explore.

Wow, what a dance that was.

[Dreamwoven]

A couple of items on the asteroid belt. It lies between Mars and Jupiter.

http://www.universetoday.com/130231/...asteroid-belt/

http://www.universetoday.com/130136/...id-belt-earth/