Pulsar... https://en.wikipedia.org/wiki/Pulsar
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Pulsar... https://en.wikipedia.org/wiki/Pulsar
It puzzles me why the radiation is not global over the pulsar but localized like a light in a lighthouse that rotates the beam.
I am afraid I don't understand what pulsars are, and I have read the wikipedia item on it.
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.Quote:
Originally Posted by tailor STATELY
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.
Thanks for that clear explanation, tailor. It was in the wikipedia item, but made much clearer by your description.
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.
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.Quote:
Originally Posted by 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/
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/
I think the theoretical EM Drive is the most interesting way to get to the asteroid belt. However, I don't think we would be able to send humans there, so robotics would have to also advance before it is feasible to mine on the asteroids.
The Universe Today published an article on how many moons there are in the solar system. You can read the article here: http://www.universetoday.com/15516/h...-solar-system/. The question is not as simple as one might think...
Earth-like planet discovered around Proxima Centauri: http://www.universetoday.com/130276/...ri-discovered/
Having an Earth-like exoplanet so close is good news. The article mentioned that the data is at the limit of current measurement abilities. So before sending a nanocraft there we need to improve our ability to measure what is out there.
Another contribution from Journal of Popular Astronomy:
NEW DISTANT DWARF PLANET BEYOND NEPTUNE
University of British Columbia
Astronomers have discovered a new dwarf planet orbiting in the disc of
small icy bodies beyond Neptune. The new object is about 700 km in
diameter and has one of the largest orbits for a dwarf planet.
Designated 2015 RR245 by the International Astronomical Union's Minor
Planet Center, it was found with the Canada-France-Hawaii Telescope on
Mauna Kea, Hawaii, as part of the ongoing 'Outer Solar System Origins
Survey' (OSSOS). The OSSOS project uses computers to hunt for the
images, and the team was presented with a bright object moving at such a
slow rate that it was clearly at least 120 times further from the Sun
than the Earth. The size of RR245 is not yet exactly known, as its
surface properties need further measurement. The vast majority of dwarf
planets like RR245 were destroyed or thrown from the Solar System as the
giant planets moved out to their present positions. RR245 is one of the
few that survived to the present day, along with Pluto and Eris, the
largest known dwarf planets. RR245 now circles the Sun among the remnant
population of tens of thousands of much smaller trans-Neptunian bodies,
most of which orbit unseen. RR245 has been on its highly eccentric orbit
for at least the last 100 million years. After hundreds of years further
than 80 astronomical units (AU) from the Sun, RR245 is travelling towards
its closest approach at five billion km (34 AU), which it will reach
around 2096. As RR245 has been observed for only one of the 700 years it
takes to orbit the Sun, where it came from and how its orbit will slowly
evolve in the far future is unknown. Its precise orbit will be refined
over the coming years, after which RR245 will be given a name. As
discoverers, the OSSOS team can submit their preferred name for RR245 to
the International Astronomical Union for consideration. RR245 is the
largest discovery and the only dwarf planet found by OSSOS, which has
discovered more than five hundred new trans-Neptunian objects.
This will take 700 years to orbit the sun. Planet 9 a giant planet which would orbit the sun in 10,000 to 20,000 years, looks increasingly unlikely.
Pluto is about 2370 km in diameter: http://www.space.com/18568-how-big-is-pluto.html So 700 km is pretty small.
This could be on the lower edge of what constitutes a dwarf planet although having enough gravity to have a spheroidal shape is what counts: https://www.spaceanswers.com/solar-s...-dwarf-planet/
That's true, YesNo. Many are still smarting from the demotion of Pluto from a planet to a dwarf planet. Ceres is also a dwarf planet, spheroid, but without any moons of its own, unlike Pluto.
Cassini is still orbiting the only moon (Saturn's Titan) with extensive regions of open seas. See http://earthsky.org/space/saturns-mo...looded-canyons
The SOCIETY for POPULAR ASTRONOMY
Electronic News Bulletin No. 427 2016 August 14
Also has a post on the above,more detailed. Copied it below:
CASSINI FINDS FLOODED CANYONS ON TITAN
NASA
The Cassini spacecraft has found, on Saturn's large moon Titan, deep,
steep-sided canyons that are flooded with liquid hydrocarbons. The
finding represents the first direct evidence of the presence of liquid-
filled channels on Titan, as well as the first observation of canyons
hundreds of metres deep. The Cassini observations reveal that the
channels -- in particular, a network of them named Vid Flumina -- are
narrow canyons, generally a bit less than a kilometre wide, with slopes
steeper than 40 degrees. The canyons also are quite deep -- those
measured are 240 to 570 metres from top to bottom. The branching
channels appear dark in radar images, much like Titan's methane-rich
seas. That suggested to scientists that the channels might also be
filled with liquid, but a direct detection had not been made until now.
Previously it was not clear if the dark material was liquid or merely
saturated sediment -- which at Titan's frigid temperatures would be made
of ice, not rock. Cassini's radar is often used as an imager, providing
a window to see through the dense haze that surrounds Titan to reveal the
surface below. But during a recent pass, the radar was used as an
altimeter, sending pings of radio waves to the moon's surface to measure
the height of features there. The researchers combined the altimetry
data with previous radar images of the region to make their discovery.
The key to understanding the nature of the channels was the way Cassini's
radar signal reflected off the bottoms of the features. The radar
instrument observed a glint, indicating an extremely smooth surface like
that observed from Titan's hydrocarbon seas. The timing of the radar
echoes, as they bounced off the canyons' edges and floors, provided
direct measures of their depths. The presence of such deep cuts in the
landscape indicates that whatever process created them was active for a
long time or eroded down much faster than in other areas of Titan's
surface. The researchers' proposed scenarios include uplift of the
'terrain' and changes in sea level, probably both. It is likely that a
combination of those processes led to the formation of the deep canyons,
but it is not clear to what degree each was involved. What is clear is
that any description of Titan's evolution needs to be able to explain how
the canyons got there. Terrestrial examples of both of those types of
canyon-carving processes are found along the Colorado River in Arizona.
An example of uplift powering erosion is the Grand Canyon, where the
terrain's rising altitude caused the river to cut deeply downward into
the landscape over the course of several million years. For canyon
formation driven by variations in water level, look to Lake Powell. When
the water level in the reservoir drops, it increases the river's rate of
erosion. While the altimeter data also showed that the liquid in some of
the canyons around Ligeia Mare is at sea level -- the same altitude as
the liquid in the sea itself -- in others it sits tens of metres higher
in elevation. The researchers interpret the latter to be tributaries
that drain into the main channels below. Future work will extend the
methods used in this study to all the other channels that Cassini's radar
altimeter has observed on Titan. The researchers expect their continued
work to produce a more comprehensive understanding of forces that have
shaped Titan's landscape.
It is interesting that the terrain needs to rise as the water erodes the surface for the canyons to get as deep as they are. That sort of makes sense. I normally think of the process as just the effect of water rather than the rising ground.
What would happen if the fluid keeps digging but the ground does not rise?Quote:
Originally Posted by YesNo
It would take a longer time to dig the same size hole because more ground further along the water way would have to be moved out of the way.Quote:
Originally Posted by desiresjab
I remember watching Deneb as the Swan constellation descended into the waters of Green Bay last autumn. I was sheltered by a warm cabin and with a large window facing south-west. Nice sunsets as well.
What amazes me is the margin of error reported in the article. Deneb could be between 1425 and 7000 light years away. That means that other estimates, including those about its size, should have similar ranges.
Yes, that comment struck me too. They are vast ranges. How much else is that far out in terms of estimated distances? I mean 1,425 light years versus 7,000 light years.
http://www.universetoday.com/130357/...-for-bad-news/
It looks as if the latest proposals to investigate the moon of Saturn with liquid seas (the probe Europa Clipper) may not get funding. It looks to be an interesting project.
Europa is more interesting as a source of life than other places. It would be nice to find living organisms there that are not related to those on Earth. I was hoping they might have found evidence of life on Mars, but I haven't heard of anything.
Still, being forced to keep to a tighter budget may be a good thing in the long run. That could lead to new technologies allowing more missions to be sent for the same cost.
Another idea is the possibility of a dyson sphere to collect the energy from a sun/star. See http://earthsky.org/space/tabbys-star-more-weirdness. So called out of a science fiction book: https://en.wikipedia.org/wiki/Dyson_sphere. Interesting discussion, still unresolved...
spectacular conjunctions in the sky at the moment:
http://www.universetoday.com/130283/...-conjunctions/
On Google Star Map, I see Mercury, Venus and Jupiter should be close together along with Saturn and Mars in a different portion of the sky. I'll have to pay attention tonight.
I like the idea of those tiny probes that ride laser beams the best, but I don't see why we would want to send humans there. Robot technology needs to get better than it is. Come to think of it I don't understand why we aren't contemplating going to the Moon to practice new technologies rather than thinking about manned landing on asteroids. Even there I don't see why humans need to be the ones going to those places.
What we need to find is not just an Earth-like planet, but one that suggests there already is life on the planet. As the second article you linked to mentioned, we don't even know if those current Earth-like candidates are really Earth-like.
No, its true, the technology is not there yet, it is a long way away still. That's my feeling too.
http://www.universetoday.com/130419/...uri-exoplanet/
The above link deals with the chance that an earth-like planet is orbiting the nearest star to our own (Proxima Centauri). A statement will be made from the European Southern Observatoryhttp://www.eso.org/public/about-eso/esoglance/ around midday today.
It looks like the ESO confirmed the planet's discovery: http://futurism.com/eso-confirms-ear...xima-centauri/
Great, well done YesNo. The link to the ESO post itself finally came out yesterday evening after I logged off:
http://www.universetoday.com/130427/...-nearest-star/
There are risks in long-distance space journeys made by tiny sail propulsion. This post in Universe Today discusses them:
http://www.universetoday.com/130458/...nherent-risks/
Something else I have been questioning is the description of a planet as "earth-like". It just means rocky and that it is within the habitable zone in terms of distance from its sun: http://www.universetoday.com/130469/...ma-centauri-b/.
We also have only "life on earth" as a yardstick.
Of course it is encouraging that Proxima Centauri b does fulfil the basic criteria, but then so does Mars...
The problem with Proxima Centauri, among other things, is that it periodically flares, and unless I'm mistaken is part of a distant binary star system... most people don't understand just how unlikely Life is, even on our extremely "earth-like" planet. Any solar system that falls short of our rather amazing circumstances, would be hard pressed to support higher lifeforms.Quote:
Originally Posted by Dreamwoven
Also consider, when our sun was much younger and burned cooler, it was Venus that was in that habitable "goldilocks zone".