In which direction would Earth escape the Sun's orbit?

Stompbox

Now, I believe that the Earth will be engulfed by the expanding Sun before it could theoretically escape the Sun's orbit (or maybe it won't at all, I'm a layman here) but I was wondering would the Earth fall towards the Sun or venture away from it should it occur? Myself and the boys were chewing the fat over some pints last night and this came up. One of the chaps informed me that the Earth could, hypothetically speaking, escape the Sun's orbit (which I was not aware of) and that if it did, it would move away from the Sun. I would have assumed that the attractive gravitation pull would be the only force that could eventually disrupt the Earth's orbit and bring it into the Sun but one of of the other lads disagreed and supported the initial argument.

Any of you kind folk willing to impart some knowledge on the unenlightened?

Popoutman

The only things that determine the Earth's orbit are its velocity/location at any point, and the mass of the larger object (in this case the sun). This is slightly simplified, but it's enough for this discussion.

When the sun ages to the red giant stage, it is expected to have lost a certain amount of mass through the solar wind and through the conversion of matter to energy via fusion.

Because the Sun will have dropped in mass, this would mean that the earth's orbit would be at a greater radius, and longer time to orbit than it is currently.

The interesting question is that will the earth's orbit have moved outwards enough to have escaped the actual "surface" of the red giant stage of the Sun's evolution. Astrophysicists have not yet (to my knowledge) agreed on which scenario is more likely - that the Earth will be absorbed into the the Sun as the Sun expands, or whether the Earth will be just above the "surface" of the red giant, getting all the water boiled off and leaving a molten silicate/lava ball. Once the Sun becomes a white dwarf at the centre of an expanding planetary nebula, if the Earth still exists as a cooling dead rock ball, it will still be in orbit around the dead core of the Sun at a greater distance than it is currently.

In the first scenario, the gravitational effect is unchanged, the Earth will still be orbiting the Sun albeit inside the Sun's atmosphere, and most likely being boiled away. The physical size of the Sun won't have a substantial effect on the orbit of the Earth.

Either way - there's no mechanism by which the Earth will escape the Sun without any outside influence on it. The Sun won't lose enough mass for the Earth to be perturbed away by the movement of nearby stars, and there isn't a known mechanism by which the Earth could be accelerated to move its orbit outwards enough that it would be effectlvely in interstellar space.

(Note that this ignores the Yarkovsky effect of acceleration from night-time cooling effects of spinning bodies - this shouldn't have much effect in a body the size of the Earth anyway.)

slade_x

Stompbox wrote: »

Any of you kind folk willing to impart some knowledge on the unenlightened?

You might find the below links of particular interest:

http://www.universetoday.com/11763/planet-survives-its-star-becoming-a-red-giant/

http://en.wikipedia.org/wiki/Sun#Life_cycle

Its looking more and more likely that considering the earths mass and tidal interactions with the sun, earth will eventually be engulfed below the suns photosphere. The sun not being selective enough it will not have passed enough of its angular momentum to the earth to make an escape fast enough even in the time given. it has however lost most of it to all the planets etc. (but most to the largest planets obviously; jupiter, saturn, neptune, etc) While the sun still has most of its mass about 99.9% of the solar systems it only has about 2% of its angular momentum. the loss of mass and angular momentum, at present is believed to not be enough for the earth to make an escape as it were

Either way the earth will not survive as it is regardless. The future of the earth more closely resembles mercury than it does mars and as the sun continues to become larger and more luminous earths eventual fate becomes more bleak. Just as the Sun, our star's presence has contributed to the continuation and propering of life on this planet, it will ultimately end what is has so long sustained. Although the expansion wont be sudden, it will be a slow process.

And i wouldnt worry about it just yet, approximately under 5 billion years is a long time, Man (including its evolutionary ancestors) is only maybe 7-10 millions years old ("modern man; homosapien is only around 200,000 years old") The Most successful animals we know of to walk the face of this earth lasted around 185 millions years, with some of the more famous of these animals like the Tyrannosaurus and triceratops in its period of about 80 million years in the cretaceous

Which gives mammals up to around 145 million years from the cretaceous period to have lived (this is probably a gross exaggeration) as im not saying mammals were given rise to right at the start of the cretaceous but merely at some point in that period, so a maximum of 145 million years for mammals

So basically at present its a time frame exponentially longer than any species that we know of has ever survived on this planet. We shouldnt become so preoccupied with the timescales of the vast universe as our lives are so much less than a fraction of the fraction of time our entire species has existed including our ancestry that trying to express our existance in a fraction of time on the scale of how long the universe has existed, well suffice to say it couldnt properly be expressed in such a way that it would readily mean anything to anyone. even though it would be easy enough to do

Popoutman wrote: »

the Earth will still be orbiting the Sun albeit inside the Sun's atmosphere, and most likely being boiled away.

The earth and all the other orbiting bodies are presently inside the suns atmosphere. The earth couldnt exist as it is now if it were not, at its present orbit inside the Suns heliosphere. There are many different layers to the suns atmosphere much like the earths atmosphere, and this atmosphere will change as the star does

http://www.universetoday.com/18447/suns-atmosphere/

http://en.wikipedia.org/wiki/Sun#Atmosphere

Capt'n Midnight

If you remove gravity the earth flies away on a tangent to the Sun

But that ain't going to happen unless the sun looses all it's mass.


gravity wells - A 3,038 ton Saturn V rocket can get 47 tons to a translunar orbit , that's just over 1.5% of take off weight , and you have to go a lot higher on the page to get to mars etc.

http://xkcd.com/681/

As for the energy need to leave the Sun
For the 478Kg New Horizons probe to Pluto the launch mass was 587 tons
a payload of 0.08 %

http://en.wikipedia.org/wiki/New_Horizons
http://www.astronautix.com/lvs/atlsv551.htm

RichieC

The earths orbit is decaying isnt it?

Popoutman

RichieC wrote: »

The earths orbit is decaying isnt it?

No. The Earth's orbit is actually quite stable..

The Earth's rate of spin is changing mostly due to tidal interactions with the Moon. The Earth's orbit is not affected by changes in the spin of the Earth

Popoutman

Popoutman wrote: »

the Earth will still be orbiting the Sun albeit inside the Sun's atmosphere, and most likely being boiled away.

slade_x wrote: »

The earth and all the other orbiting bodies are presently inside the suns atmosphere. The earth couldnt exist as it is now if it were not, at its present orbit inside the Suns heliosphere. There are many different layers to the suns atmosphere much like the earths atmosphere, and this atmosphere will change as the star does

Perfectly true. I wanted to avoid saying the surface of the Sun. Should have said photosphere for accuracy. Good catch.

RichieC

Popoutman wrote: »

No. The Earth's orbit is actually quite stable..

The Earth's rate of spin is changing mostly due to tidal interactions with the Moon. The Earth's orbit is not affected by changes in the spin of the Earth

yes, but it is not 100% efficient, so I just mean technically it is decaying.

though honestly, I'm a layman and just repeating something i heard or read somewhere.

Myrddin

Is it possible, that given certain circumstances, planets can actually break free of their parent star & in essence become rogue planets?

Theoretically, if an earth like planet were to do this, what would such a place be like? Obviously the whole planet would freeze over, & be completely dark...but what of the atmosphere? Also, could inner thermal activity provide pockets or areas that could support life?

Popoutman

EnterNow wrote: »

Is it possible, that given certain circumstances, planets can actually break free of their parent star & in essence become rogue planets?

If a planet were in orbit around a double star system, where one of the pair lost enough mass (e.g. supernova explosion) the orbit of said planet may change enough to end up no longer orbiting the star that's left. Another scenario would be where a planet is interacting with another planet and the interaction between the two planets robs momentum from one and transfers to the other (same as a gravitational slingshot by a spaceprobe past Jupiter) such that one gains enough momentum to escape the gravity well of the central star.

EnterNow wrote: »

Theoretically, if an earth like planet were to do this, what would such a place be like? Obviously the whole planet would freeze over, & be completely dark...but what of the atmosphere? Also, could inner thermal activity provide pockets or areas that could support life?

The atmosphere would freeze out onto the surface, and you'd have a layer of water ices, with a layer of CO2 ice, a layer of N2 ice, then O2 ice. It's possible that extremophiles could live in places that would not be affected by the freezing - e.g. near smoker vents where the hot location would not freeze for a very long time, or at the bottom of the ocean trenches where heat from the core may be enough to stop the freezing of the water in the area. Nothing safe though for air-breathing lifeforms it would appear.

Capt'n Midnight

the moon causes a tide of about 40cm in the land (yes the earth bulges) so a star coming close enough to affect the pull of the sun would cause a greater effect

this is the film - when worlds collide
http://www.imdb.com/title/tt0044207/


once the ocean surface froze over there would still be plenty of heat in the oceans for a long time, geothermal heat , pressure and smokers would keep a large volume liquid for a time

http://en.wikipedia.org/wiki/Icy_moon