Astronomy and Cosmology

Is here a good reference that gives me the periods involved in the formation of the Sun? I'm finding the various sites talk of when the Sun "formed" but I'm not sure what stage they are describing. We start off with a nebula, how long to the stage where the Sun goes Alpha Tauri (if it did)? Then how long before it becomes a main sequence star? I once tried to calculate how long matter would take to free fall into the Sun from an estimate of the size of the nebula and from memory it was about 150,000 years and that was if each particle did not collide with any other particle or have any angular motion, so it was a direct "straight line". So I suppose that is an …

Sorry for the interrupt. However, I have few questions: 1. Why do we need a nebula in order to form a star/Sun? 2. What about star forming in a galaxy core? For example star forming activity in the Milky Way galaxy: https://en.wikipedia.org/wiki/Milky_Way#Galactic_Center "The bar may be surrounded by a ring called the "5-kpc ring" that contains a large fraction of the molecular hydrogen present in the Milky Way, as well as most of the Milky Way's star-formation activity." 3. Does it mean that the core of the Milky way galaxy has the power to form much more new stars than all nebulas in the galaxy? 4. Is it possible that our sun had been for…

I apologise for this somewhat obvious question, but does a telescope's limiting magnitude increase when using time-lapse photography - this compared to real-time viewing?

Let's take as an example a Deuterium-Deuterium fusion spacecraft. The estimated exhaust velocity is fairly high, an estimated 19,000 km/s (0.063 c) which means a 120,000 ton starship attached to 12,000,000 tons of deuterium can do a delta-vee of ~0.29 c. With an efficient magnetic sail that means the journey speed approaches ~0.29 c, albeit with the mass-penalty of the sail. Is it really possible to flight at speed of 0.063*c or faster through Kuiper belt, Hill's cloud and Oort cloud to, say Proxima Centauri and not collide with something. There is an opinion that we are going to collide in case of fast interstellar travel - http://boards.straightdope.com/sdmb/sho…

Question: If the model of the universe is based on Relativity, doesn't it follow that the model is relative? IOW that the Big Bang and expansion is a relative observation and not an absolute model: that any observer in the universe, be it today here or there or 10 billion years in the future and the past, will observe the universe having an age of 13.799±0.021 billion years?

http://www.space.com/17884-universe-expansion-speed-hubble-constant.html "The most precise measurement ever made of the speed of the universe's expansion is in, thanks to NASA's Spitzer Space Telescope, and it's a doozy. Space itself is pulling apart at the seams, expanding at a rate of 74.3 plus or minus 2.1 kilometers (46.2 plus or minus 1.3 miles) per second per megaparsec (a megaparsec is roughly 3 million light-years)." So, the expansion rate is about 74 kilometer per second per 3 million LY. Let's verify if it is correlated with some other evidences. For example – Andromeda galaxy which is located 2.5 Million LY from Earth: https://en.wikipedia.org/wiki/A…

How does the recent discovery of gravitational waves presage time travel ?

I heard about a theory that our universe may exist inside a black hole, and I was wondering if someone could help explain this to me. My teacher didn't say much about it but just from thinking I can gather that since a supermassive black hole's immense gravity can distort spacetime, so an entire universe could fit inside. But what I don't get is how a universe could possibly get INSIDE the black hole in the first place. Does the black hole condense enought matter into so small of a space that when the gravity of the black hole ceases to act on the matter, it expands, giving us the Big Bang? Just need an explanation because this has really been bothering me.

https://en.wikipedia.org/wiki/Timeline_of_telescopes,_observatories,_and_observing_technology http://www.projectrho.com/public_html/rocket/spacewardetect.php The second link specifies calculations for the following: chemical rockets; fusion engines, ion drives, steady-state plasma drives - most types of torchships. Taking into account the aforementioned links could somebody please answer me at which point of astronomic observations (the year, or decade) was it possible for Terran astronomers to detect the incoming spacecraft (interstellar or interplanetary) by its exhaust plume?

i am asking it because i have found that astrology is based on geocentric model of cosmos. we test it on heliocentric model and it failed. is not it obvious? something is tested on a model on which it is not based. is not it bound to fail? but if we took geocentric astrological data and convert them into heliocentric data, will astrology fail?

20.66 earth masses of ice inside Saturn if density of metallic hydrogen = 2.2 g/cm^3 The surface of the gas giant is defined as the point where the pressure of the atmosphere is 1 bar, Scale height = the vertical distance over which the density and pressure fall by a factor of 1/e. saturn Scale height: 59.5 km jupiter Scale height: 27 km https://en.wikipedia.org/wiki/Frenkel_line Below the Frenkel line the fluids are "rigid" and "solid-like", whereas above it fluids are "soft" and "gas-like". (1-((1.326/2.2)^0.333)) * (76850km-160km) * (0.08g/cm^3) * 2.53 * (10m/s^2) * (1/((1.326/2.2)^0.333)) in bar = 285 047 bar (according to google) = pressure at which hydrogen …

I am trying to understand the composition of solar flares: whether they are purely electromagnetic, for example, which to say they ALL propagate through space at the speed of light, or else composed of (or include) high-energy particles. The reason for the 'ALL' is because I keep coming across conflicting descriptions of solar flares, with many accounts actually referring to CMEs, or else discussing solar flares and CMEs as if they were merely two terms for the same phenomena. For example, did Richard Carrington (and most of the world) witness in 1859 a solar flare or a CME? I've come across both explanations. Finally, it seems that solar flares cause aurorae, and at the …

Hello community, Recently I was looking into dark matter and upon pondering its illusiveness, I had a sudden epiphany. I would like to have a discussion with someone who is both adept in the fields of physics and cosmology, and would be interested in aiding me to express certain information using formulas. I do not wish to waste anyones time, but if one of you have time to spare, please feel free to contact me via email. Thank you very much, Kindest regards, Robert removed by mod

News of the day, Earth comprises the merged remains of Theia. According to a recently published article in Science, Theia--the Mars sized planet at first believed to have caused our Moon's creation through a "glancing" impact with Earth about 4.6 billion years ago--is now believed to have directly impacted and completely merged with Earth, which "indistinguishable" oxygen isotopic studies appear to suggest. Could there be another explanation for Earth/Moon shared isotopic profile? I welcome your thoughts.

The Paradigm of Types represents all cosmological can biological constructions. The paradigm indicates that there are 7 types of stars and 9 types of planets, and that all solar systems begin with 9 planets. The ultimate proof that all solar systems begin with 9 planets is yourself. The paradigm represents all of biology from its beginning with 3 early eukaryotes and the first archaea up to and including you. The paradigm is the ultimte objective science and is introduced in the essay "Discovering the Universe with the Paradigm of Types", which is located at home.spin.net.au/paradigm/211.pdf

I am aware that the dwarf planet Ceres has a mean orbital radius of 2.77AU so obviously at it's closest to Earth the distance would be 1.77AU. But obviously if Earth and Ceres are on opposite sides of the Sun then this distance would be much greater Theoretically if you could build a spacecraft capable of accelerating indefinitely at say one quarter of Earth's gravity, taking the fastest possible route to the planet. One further thing to consider would be that due to safety, you wouldn't be accelerating all the way across we're assuming you need to stop at Ceres, so halfway across you can begin to decelerate the ship at the same rate. With the acceleration/decele…

Hi all. Is the sun position at longitude 000 00' 00" the exact geographic south at 12:00:00N time every and any day of the year ? Does the seasonal earth rotation axis angle alters anything regarding azimuth ?

In which ranges of the E.M. spectrum was the Geospace and interplanetary space scanned? And to which distance? And to which distance was the outer space scanned by radars in order to avoid obstacles for unmanned interplanetary flights?

I know it is done by measuring the time it takes a signal to reach the earth, but how do we know the time it takes to reach earth ?

The Cosmic Microwave Background of our Universe is as follow: https://en.wikipedia.org/wiki/Cosmic_microwave_background "The CMB has a thermal black body spectrum at a temperature of 2.72548±0.00057 K." Therefore, does it mean that the Universe is a black body?

I am supposed to deliver a six-seven minutes speech on "Space and Mankind". Requesting you all to share your opinion and ideas on the same!

It's my understanding that anti-matter travels backwards in time. I think that while this may not make much sense to us in our universe, (such as reducing entropy when our universe increases entropy) it seems to make perfect sense for antimatter that was created from the Big Bang. If we put our time datum of 0 at the instant of the Big Bang and counted time forward as matter and energy "inflated" after the Big Bang, then any antimatter that was created in the same Big Bang would then "inflate" in negative time counting backwards from 0. While we would say that antimatter was moving backwards in time, an antimatter version of us in the anti-universe would simply d…

How large could a rocky planet be? It seems that at some point the planet would hold onto too much gas to be a rocky planet. Even figuring lower average density than the Earth I would think there is a point of no return from being a mini Neptune at least...

I was wondering about gravitational lensing as an alternative to inflation to account for the smooth nature of the CMB, If our observable segment of the universe was surrounded by a vast dense patch of matter, couldn't light travelling towards us be lensed by this and spread evenly so that we observed a homogenous background. To clarify, our CMB would in this case be a magnified section of a smaller area, the lensing effect spreading this local point evenly across our view of the universe as we look back in time. IE the CMB is just a small area smudged out across the sky. So rather than inflation spreading the radiation out rapidly, gravitational lensing spr…

Black hole or stars?