Space: The Final Frontier

[shariqq]

Here, regular articles of interest (to me atleast) about Astrophysics, or speculation based on Fact.

[shariqq]

Sun, Earth, Moon: When the Sun Goes Senile

The Sun is midway through its stable hydrogen burning phase known as the main sequence. But when the Sun enters the red giant phase in around 5 billion years things are going to get a lot rougher in the Earth-Moon system.

During the red giant phase the Sun will swell until its distended atmosphere reaches out to envelop the Earth and Moon, which will both begin to be affected by gas drag-the space through which they orbit will contain more molecules.

The Moon is now moving away from Earth and by then will be in an orbit that's about 40 percent larger than today. It will be the first to warp under the Sun's influence.

'The Moon's actual path is a wiggly line around the Sun, with it moving faster when it is slightly farther out (at full Moon) and more slowly when it is slightly closer (at new Moon),' said Lee Anne Willson of Iowa State University. 'So the gas drag is more effective at the farther part of the orbit and this will put the Moon into an orbit where the new Moon is closer to Earth than the full Moon.'

Willson's idea about the Moon's demise, explained recently to SPACE.com, is an unpublished byproduct of her research into Earth's fate in the face of an expanding Sun.


Moving away

Today, the Moon is on average 239,000 miles (385,000 kilometres) away and has reached this point after a long and dramatic journey.

Earth's  Moon was born around 4.5 billion years ago in a titanic collision between our planet and a Mars-sized sibling, according to the leading theory. The enormous impact threw debris into orbit around the young Earth and from this maelstrom the Moon coalesced.

For the last few billion years the Moon's gravity has been raising tides in Earth's oceanswhich the fast spinning Earth attempts to drag ahead of the sluggishly orbiting Moon. The result is that the Moon is being pushed away from Earth by 1.6 inches (4 centimeters) per year and our planet's rotation is slowing.

If left unabated the Moon would continue in its retreat until it would take bout 47 days to orbit the Earth. Both Earth and Moon would then keep the same faces permanently turned toward one another as Earth's spin would also have slowed to one rotation every 47 days.


Solar influence

The Sun's mutation into a red giant provides a huge stumbling block to the Moon's getaway and is likely to ensure the Moon ends its days the way it began; as a ring of Earth-girdling debris.

'The density and temperature both increase rapidly near the apparent surface (photosphere) of the future giant Sun,' Willson explained. As the Earth and Moon near this blistering hot region, the drag caused by the Sun's extended atmosphere will cause the Moon's orbit to decay. The Moon will swing ever closer to Earth until it reaches a point 11,470 miles (18,470 kilometers) above our planet, a point termed the Roche limit.

'Reaching the Roche limit means that the gravity holding it [the Moon] together is weaker than the tidal forces acting to pull it apart,' Willson said.

The Moon will be torn to pieces and every crater, mountain, valley, footprint and flag will be scattered to form a spectacular 23,000-mile-diameter (37,000-kilometer)  Saturn-like ring of debris above Earth's equator. The new rings will be short-lived. Theory dictates they'll eventually rain down onto Earth's surface.

'Particles of different masses will have different survival times; the smaller particles will be removed first, and the biggest ones last. Most of the ring particles would be gone by the time the Earth reaches the stellar photosphere,' Willson said.

If the Sun's photosphere reaches Earth, our planet too will experience drag and spiral into the Sun to be incinerated.


Possible out

There are possible natural alternatives, however.

If the Sun as a red giant sloughs off enough material before Earth evaporates, our planet will be revealed from its stellar cocoon in a Moon-less guise. Earth,  robbed of its companion, would undertake a lonely vigil as the Sun turns eventually into a stellar corpse called a white dwarf Sun, fading to black over the ensuing trillions of years.

Alternatively, if the swelling Sun loses 20 percent of its mass prior to it reaching our vicinity, both Earth and Moon could be spared incineration and remain together facing each other for eternity. The actual outcome remains a theoretical uncertainty because no red giant star has been observed during this crucial phase.

[shariqq]

10 Strangest Things in Space

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In no particular order:

AntiMatter
Like Superman's alter-ego, Bizzaro, the particles making up normal matter also have opposite versions of themselves. An electron has a negative charge, for example, but its anti-matter equivalent, the positron, is positive. Matter and anti-matter annihilate each other when they collide and their mass is converted into pure energy by Einstein's equation E=mc². Some futuristic spacecraft designs incorporate anti-matter engines.

Mini-Black Holes
If a radical new "braneworld" theory of gravity is correct, then scattered throughout our solar system are thousands of tiny black holes, each about the size of an atomic nucleus. Unlike their larger brethren, these mini-black holes are primordial leftovers from the Big Bang and affect space-time differently because of their close association with a fifth dimension (shq: wtf? fifth dimension??)

Cosmic Microwave Background
Also known as the CMB, this radiation is a primordial leftover from the Big Bang that birthed the universe. It was first detected during the 1960s as a radio noise that seemed to emanate from everywhere in space. The CMB is regarded as one of the best pieces of evidence for the theoretical Big Bang. Recent precise measurements by the WMAP project place the CMB temperature at -455 degrees Fahrenheit (-270 Celsius).

Dark Matter
Scientists think it makes up the bulk of matter in the universe, but it can neither be seen nor detected directly using current technologies. Candidates range from light-weight neutrinos to invisible black holes. Some scientists question whether dark matter is even real, and suggest that the mysteries it was conjured to solve could be explained by a better understanding of gravity.

Exoplanets
Until about the early 1990s, the only known planets in the universe were the familiar ones in our solar system. Astronomers have since identified more than 190 extrasolar planets (as of June 2006). They range from gargantuan gas worlds whose masses are just shy of being stars to small, rocky ones orbiting dim, red dwarfs. Searches for a second Earth, however, have so far turned up empty. Astronomers generally believe that better technology is likely to eventually reveal several worlds similar to our own.

Gravity Waves
Gravity waves are distortions in the fabric of space-time predicted by Albert Einstein's theory of general relativity. The waves travel at the speed of light, but they are so weak that scientists expect to detect only those created during colossal cosmic events, such as black hole mergers. LIGO and LISA are two detectors designed to spot the elusive waves.

Galactic Cannibalism
Like life on Earth, galaxies can "eat" each other and evolve over time. The Milky Way's neighbor, Andromeda, is currently dining on one of its satellites. More than a dozen star clusters are scattered throughout Andromeda, the cosmic remains of past meals. Andromeda and our galaxy colliding will take place in about 3 billion years.

Neutrinos
Neutrinos are electrically neutral, virtually mass-less elementary particles that can pass through miles of lead unhindered. Some are passing through your body as you read this. These "phantom" particles are produced in the inner fires of burning, healthy stars as well as in the supernova explosions of dying stars. Detectors are being embedded underground, beneath the sea, or into a large chunk of ice as part of IceCube, a neutrino-detecting project.

Quasars
These bright beacons shine to us from the edges of the visible universe and are reminders to scientists of our universe's chaotic infancy. Quasars release more energy than hundreds of galaxies combined. The general consensus is that they are monstrous black holes in the hearts of distant galaxies.

Vacuum Energy
Quantum physics tells us that contrary to appearances, empty space is a bubbling brew of "virtual" subatomic particles that are constantly being created and destroyed. The fleeting particles endow every cubic centimeter of space with a certain energy that, according to general relativity, produces an anti-gravitational force that pushes space apart. Nobody knows what's really causing the accelerated expansion of the universe, however.

[kaytee]

Where is Bruce Willis when you need him?

Asteroid threatens Earth

An asteroid may come uncomfortably close to Earth in 2036 and the United Nations should assume responsibility for a space mission to deflect it, a group of astronauts, engineers and scientists said on Saturday.

Astronomers are monitoring an asteroid named Apophis, which has a 1 in 45 000 chance of striking Earth on April 13 2036.

Although the odds of an impact by this particular asteroid are low, a recent congressional mandate for Nasa to upgrade its tracking of near-Earth asteroids is expected to uncover hundreds, if not thousands of threatening space rocks in the near future, former astronaut Rusty Schweickart said.

"It's not just Apophis we're looking at. Every country is at risk. We need a set of general principles to deal with this issue," Schweickart, a member of the Apollo 9 crew that orbited the Earth in March 1969, told an American Association for the Advancement of Science conference in San Francisco.

Schweickart plans to present an update next week to the UN Committee on Peaceful Uses of Outer Space on plans to develop a blueprint for a global response to an asteroid threat.

The Association of Space Explorers, a group of former astronauts and cosmonauts, intends to host a series of high-level workshops this year to flesh out the plan and will make a formal proposal to the UN in 2009, he said.

Schweickart wants to see the UM adopt procedures for assessing asteroid threats and deciding if and when to take action.

Gravity to alter asteroid's course

The favoured approach to dealing with a potentially deadly space rock is to dispatch a spacecraft that would use gravity to alter the asteroid's course so it no longer threatens earth, said astronaut Ed Lu, a veteran of the International Space Station.

The so-called Gravity Tractor could maintain a position near the threatening asteroid, exerting a gentle tug that, over time, would deflect the asteroid.

An asteroid the size of Apophis, which is about 140m long, would take about 12 days of gravity-tugging, Lu added.

Mission costs are estimated at $300m.

Launching an asteroid deflection mission early would reduce the amount of energy needed to alter its course and increase the chances of a successful outcome, Schweickart said.

Nasa says the precise effect of a 140m object hitting the Earth would depend on what the asteroid was made of and the angle of impact.

Paul Slovic, president of Oregon-based Decision Research, which studies judgment, decision-making and risk analysis, said the asteroid could take out an entire city or region.

[shariqq]

What zaniness. When was the last time an asteroid wiped of a race from this planet? They might just as well use those $300M per mission to finance (each time) a Ridley Scott Swords & Sandals movie + a Robert Rodriguez popcorn-fest + 2 Paul Giamatti movies!

Life Free, Die Hard!

[madali]

Another doomsday prediction.

Hope this doesnt get any media attention

[weirdo]

May be doomsday is what the world's countries need right now to get their heads out of its own ass, there is no more life (like space travel) than squabbles over land and religion

Sheesh