Description: General physics and astronomy discussions not directly related to Celestia
V is the Roman numeral for 5.rrrraygun wrote:(luminosity class V, aka 4)
Your guess is almost as good as anyone's Using a ruler or equivalent on the (highly speculative) maps that are available on Wikipedia probably would be as accurate as any other method.1. How many light-years (or parsecs) are we to where the Orion spur connects to the Persius arm?
2. How many light-years (or parsecs) are we to where the Orion spur connects to the Sagittarius arm?
I found three very different answers.3. How many light-years (or parsecs) are we to "Turner 5"
Of course there are appropriate stars on the other side of the cluster, regardless of where it's located (or if it exists). Whether any of their distances have been measured accurately is another matter entirely. To put it another way, any G2V stars in that area of the sky were too dim for Hipparcos to measure.and are there GVs there just beyond "Turner 5" at the end of what seems to be a sort of mini-spiral arm's terminating end?
I'm sure there are some. Further research would be required.4. What major unique sights are to be found 4,000-6,000 light-years along the Orion spur? I mean, what exists only once (in either direction up or down the Orion spur or toward the direction of "Turner 5") in 4,000-6,000 light-years (which is 1,227-1,840.5 parsecs)?
The Milkyway template that I have prepared for the Celestia distribution as part of my 10000+ NGC/IC galaxies was carefully shaped by implementing all known scientific constraints. It is not strictly factual, since a number of facts are simply still unknown. I still consider the amazing coincidence of Selden's add-on of known pulsar locations with the Milkyway arms as highly remarkable.Selden wrote:The colorful maps on Wikipedia are "artists' conceptions" and should not be considered strictly factual.
And we figured the G-type stars were roughly 10-15 light years (a.k.a. 3.26-4.6 parsecs) apart. Strictly G2s or even G2Vs though... I'd have to go through the catalogue. Doing the permutation calculation: G-type (yellow) stars could be one of ten classes (ours being 2, meaning a 'yellow' two tenths towards 'orange'), multiplied by 5 luminosity classes (ours being Roman #5 = a dwarf, or more properly, a main sequence star), and you get fifty variations of G-type stars. Ergo, 10-15 light years becomes looking more like 500-750 light years (163-230 parsecs) for distances between just two earth-bearing solar systems of strictly G2V type.
rrrraygun wrote:1.The Perseus Transit is in the direction of what constellation?
2. Cygnus X is found in what constellation?
3. The galactic central point is found in what constellation?
What's the difference between the two?rrrraygun wrote:What are your thoughts of this happening regarding the supercomets and Megacomets?
No. Why would such an explanation be necessary when we know planet formation here formed comets long ago? And if we need an extraterrestrial origin for comets, why extragalactic? Aren't solar systems (and especially galaxies) capable of keeping most of their own comets?rrrraygun wrote:Do you think they could be from matter coming in from long-ago ancient events from outside of the Galaxy?
It's impossible to travel at light speed. Be sure you're incorporating relativity into your equations if you're aiming for maximum believability.I don't know about the robot actually going the speed of light... maybe taking into consideration the mass of the giant robot, the mass of fuel it can carry and the acceleration it can achieve the limit would be evident. In the story I had initially figured 1000 years would be the time it took the robot to go from outside of one earth-bearing solar system to just outside of another one. That would mean the robot went roughly half to 75% the speed of light to get there. And that's not accounting for the amount of time and distance it would take to accelerate to that speed. I've gotta dig out my physics formulas so I can work this out.
That equation applies only to objects at rest. If you're applying it to things at relativistic velocities, try the full verison.There's a formula that tells you that at a higher speed, an amount of mass has a greater amount of potential force or something like that...which equates to mass (e=mc squared i believe).
But I like the idea of a nasty, intelligent fungus wanting to take over! (Although at least a couple of authors have written about something similar to that. Neal Asher comes immediately to mind.)rrrraygun wrote:Disregard what I said about sub-periodic table fungus.
The idea of "hitching a ride" in itself has never made any sense to me. The spacecraft would have to use an amount of energy to catch up to and fly alongside (more to land on) a body which is comparable to what would be needed to make the trip by itself. Grabbing a comet along the way to mine its raw materials and to use its mass for shielding or housing, sounds quite reasonable, though.I'm now trying to figure out the scientifically plausible way to send a robot from just one star to the next.
I did some research on comets and it turns out that the Ikeya-Zhang comet has an orbital period of 366.57 years to go 101.9 AU (15,244,017,500 km). Therefore, a one-way trip starting from near the sun on its way to Pluto then will take 183.3 years to go 50.95 AU (7,622,008,750 km ...approximately 0.00008 of a light-year). This includes the distance and time it takes to travel from the sun to halfway between the orbit distances of Earth and Mars where the robot will attach itself.
That seems plausible.I was thinking the robot ship could nuclear blast accelerate and latch onto this thing. Then it could mine it for ~180 years, and then at the furthest point detach itself.
I don't know where you got the "10-15 light years apart". I'm not saying it's wrong, just unfamiliar to me. I'm not sure I'd trust that value enough to extrapolate to other star densities. There's a lot of local variability. No matter the spacing, though, there are always lots of dim stars in between the bright ones.Now here's the thing, we think that G-type stars are about 10-15 light years apart from each other. And seeing as there are 50 different types of G-type stars, average distance could be more like 500-750 light-years apart between the stars we catagorize our sun to be. Buuuut, between those G2V stars, there are many other stars.
yup.There are two ways to travel in space given a limited amount of fuel: one way is to use half the fuel to accelerate as much as possible initially to reach a decent rate of travel in the frictionless vaccuum of space out there, and then using the rest to decelerate once within a certain distance of the destination (docking with another Ikeya-Zhang comet to mine it as it rides into the solar system
a) slingshoting doesn't work so well in the interstellar situation. To first approximation, the speed a spacecraft has at a particular distance from a star while falling in toward it is the same speed it'll have later when it get to that same distance from that star while falling away from the star (although it'll be going in a different direction) ... unless the spacecraft accelerates itself while down in close to the star. To second approximation, it could gain some speed since both star and spacecraft are orbiting around the galactic center. The spacecraft could be gravitationally accelerated into a higher energy orbit around the galaxy while the star is slowed to a lower energy orbit around the galaxy. I don't know how much that would help, but I don't think it would significantly reduce interstellar travel times.#2); the other way is to use other great chunks of mass out there as gravity wells to slingshot off of. Just like the space probes NASA has sent, but using the event horizons of stars instead of planets for this effect.
Sorry: I can't help there.I'm thinking that a combination of the two would be cool, using "Project Orion"-type successive nuclear blasts to accelerate the bot from the Ikeya-Zhang comet drop-off point to reach a maximum speed, then possibly slingshoting from stars between us and the next G2V star as an artifical comet itself.
It would be handy to know approximately how many stars are between two G2V stars on average.
All types of stars are present, from brown dwarfs to supernovae -- although the latter aren't around for long -- just an expanding shell of gases and a neutron star are left afterward.What is the range of star types found in Orion's Spur?
I think "the rocket equation" is the one you need. It takes into account the mass that's lost as fuel is expended.It takes a year to travel a light-year at the speed of light. I don't know about the robot actually going the speed of light... maybe taking into consideration the mass of the giant robot, the mass of fuel it can carry and the acceleration it can achieve the limit would be evident. In the story I had initially figured 1000 years would be the time it took the robot to go from outside of one earth-bearing solar system to just outside of another one. That would mean the robot went roughly half to 75% the speed of light to get there. And that's not accounting for the amount of time and distance it would take to accelerate to that speed. I've gotta dig out my physics formulas so I can work this out.
More than half the mass needs to be expended in order to get up to speed. Remember that you have to accelerate all the fuel that'll be thrown away during the later stages of acceleration.[The physics would be as follows in four equations...done twice to calculate for both the minimum and maximum estimated distances of 500-750 light-years:
1. To find the length of time and distance travelled from starting at a speed of zero in a frictionless vaccuum to get to maximum speed dependent on acceleration from successive nuclear blasts given the mass of the bot, the rate of fuel used to half of the supply, and total mass of fuel.
Your description is a little too simplified, since so much fuel mass is needed to get up to speed compared to the total mass that it started with.2. The same as above, but with the rest of the fuel being used at the fuel use rate to decelerate the robot back to zero.
3. The entire distance minus the above distances to give you the distance cruising the middle bit with zero acceleration at a specific speed in order to find out how long that part takes.
4. The amounts of time accelerating and decelerating, plus the amount of time spent cruising the middle bit with zero acceleration to find out how long the entire trip would take.]
Umm. Well, not quite. That's the equivalent energy of a body's rest mass.Maybe the idea of using other stars to slingshot around is bogus. Maybe it could help a little. There's a formula that tells you that at a higher speed, an amount of mass has a greater amount of potential force or something like that...which equates to mass (e=mc squared i believe).
You might want to try to get a copy of the book _Project Orion_ by George Dyson . It has a lot more usable information than the video and is available from your favorite book store or library. Some links to other references about Project Orion are available at http://www.lepp.cornell.edu/~seb/celest ... index.htmlMaybe if we knew the speed and mass of the bot from the above equations, we'd be able to know how much it compares to the masses of certain sized stars, or their larger orbiting planets (like Jupiter, which I learned that other one-time-only comets whip around and are ejected from our solar system for good by) that orbit stars.
I'll do the physics myself once I review the documentary "Code Name Project Orion", do some more internet browsing, and find those physics formulas. Then I'll post what I get.
It was a guestimate I threw out earlier.Selden wrote:I don't know where you got the "10-15 light years apart". I'm not saying it's wrong, just unfamiliar to me.
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