Interstellar Travel Not Possible Before 2200AD, Suggests Study

A new estimate of the amount of energy needed to visit the stars suggests we won't have enough for at least another two centuries

By KFC  @ [Source]

How soon could humanity launch a mission to the stars? That's the question considered today by Marc Millis, former head of NASA's Breakthrough Propulsion Physics Project and founder of the Tau Zero Foundation which supports the science of interstellar travel.

This is a question of increasing importance given the rate at which astronomers are finding new planets around other stars. Many believe that it's only a matter of time before we find an Earth analogue. And when we do find a place with the potential to host life like ours, there is likely to be significant debate about the possibility of a visit.

The big problem, of course, is distance. In the past, scientists have studied various factors that limit our ability to traverse the required lightyears. One is the speed necessary to travel that far, another is the cost of such a trip.

By looking at the rate at which our top speed and financial clout are increasing, and then extrapolating into the future, it's possible to predict when such missions might be possible. The depressing answer in every study so far is that interstellar travel is centuries away.

Today, Millis takes a different approach. He looks at the energy budget of interstellar missions. By looking at the rate at which humanity is increasing the energy it has available and extrapolating into the future, Millis is able to estimate when we will have enough to get to the stars.

To make his extrapolation, Millis looked at the amount of energy the US has used to launch the shuttle over the last thirty years or so, as a fraction of the total energy available to the country. He assumes that a similar fraction will be available for interstellar flight in future. He then calculates how much energy two different types of mission will consume.

The first mission is a human colony of 500 people on a one-way journey into the void. He assumes that such a mission requires 50 tones per human occupant and that each person will use about 1000W, equal to the average amount used by people in the US in 2007.

From this, he estimates that the ship would need some 10^18 Joules for rocket propulsion. That compares to a shuttle launch energy of about 10^13 Joules

The second mission is an unmanned probe designed to reach Alpha Centauri, just over 4 light years away, in 71 years. Such a ship would be some three orders of magnitude less massive than a colony ship so it's easy to imagine that it would require less energy.

But Millis places another constraint on this mission. Not only must it accelerate towards its destination, it must decelerate when it gets there (although why this isn't a requirement for a colony ship isn't clear).

That changes the the numbers significantly. Millis estimates that the probe would require some 10^19 Joules.

The final step in is to determine when humanity will have this kind of energy available for these kinds of missions. By extrapolation, Millis calculates that the required energy will not be available until at least the year 2196. "This study found that the first interstellar mission does not appear possible for another 2 centuries centuries," he says.

That's necessarily a crude calculation but a sobering one nonetheless. It implies that while we will soon be able to gaze with wonder upon other Earths, it will not be possible to visit them within the lifetime of anybody alive today.

In other words, for the foreseeable future, we're trapped.

Ref: arxiv.org/abs/1101.1066: Energy, Incessant Obsolescence And The First Interstellar Missions

 

 

Universe packed with hidden stars

Source

"If, say, one per cent of red dwarfs have an Earth-like planet around them, this one percent now applies to a number that is three times larger than we had so far assumed."

This photo taken by the Hubble Space Telescope shows a cluster of diverse galaxies / AP Source: AP

THE Universe might hold three times as many stars as was previously thought, a new cosmic census of eight galaxies beyond the Milky Way suggested.

US astronomers said that they discovered that small, dim stars known as red dwarfs are more plentiful than previously estimated.

"A best guess at the total number of stars in the universe is about 100 sextillion -- that is, a '1' followed by 23 zeros. We now believe this estimate is perhaps too low by a factor of about three," said Dr Pieter van Dokkum, of Yale University, who led the research.

Even that estimate remains uncertain, he added, because scientists do not know with confidence how many galaxies there are in the universe.

The findings, published in the journal Nature, also boosted the potential for other planets.

"There are possibly trillions of Earths orbiting these stars," Dr van Dokkum said.

The revised estimate of 300 sextillion stars in the universe emerged from a study of eight elliptical galaxies that are between 50 million and 300 million light years away.

In previous observations of the galaxies, it was impossible to detect red dwarf stars, as they are only about one-tenth of the mass of the sun and 1000 times fainter.

Powerful new instruments at the Keck Observatory in Hawaii allowed Dr van Dokkum's team to work out that the proportion of red dwarfs in elliptical galaxies is about 20 times greater than in the Milky Way.

Space over Time

BY MIKE ORCUTT @ technologyreview.com

 

Human exploration is the most visible use of spaceflight, but ­business and defense satellites fill the sky.

The retirement of the space shuttles marks the end of NASA's human spaceflight program, at least for now. But human missions funded by the U.S. government have represented only a small part of the action in space.

Of the 7,000 spacecraft that have been launched into orbit or beyond, more than half were defense satellites used for such purposes as communication, ­navigation, and imaging. (The Soviet Union sent up a huge number, partly because its satellites tended to be much shorter-lived than those from the United States.) In the 1970s, private companies began increasingly adding to the mix, ­launching satellites for telecommunications and broadcasting.

This graphic groups payloads by the nationality of the owner. A satellite, a capsule of cosmonauts, or a deep-space probe would each count as one payload. The data, which run through July 2011, were drawn from hundreds of sources, including space agency documents, academic journals, and interviews. They were compiled by Jonathan ­McDowell, an ­astrophysicist at the Harvard-­Smithsonian Center for Astrophysics and author of Jonathan's Space Report, a newsletter that tracks launches.

[Source]

 

Bright burning star at the birth of King Charles II was supernova, Cassiopeia A

AFP | Source

Cassiopeia A is the remnant of a once massive star that died in a violent supernova explosion. Picture: NASA Source: Supplied

THE legend that a bright star accompanied the birth of English King Charles II, which was thought to be a portent of a powerful monarch, has been proven by scientists.

One of the abiding legends of Britain's royal family is that the noon-day star appeared at Charles II's birth in 1630, who was to restore the English monarchy after the execution of his father.

"The Most Glorious Star... shining most brightly in a Miraculous manner in the Face of the Sun," was how an English writer, Edward Matthew, described the supposed event in a 1661 pamphlet.

"Never any Starre had appeared before at the birth of any (the Highest humane Hero) except our Saviour."

Accounts of the "royal star" have often been written off by historians as propaganda, coloured with Christ-like ornamentation, to cement Charles II's claim to the throne after his father had been overthrown.

But new evidence, to be put to a meeting of Britain's Royal Astronomical Society (RAS) today, suggests that a new star did in fact attend the royal birth.

The star could have been a supernova called Cassiopeia A, say Martin Lunn, former curator of astronomy at the Yorkshire Museum in northern England, and Lila Rakoczy, a US-based independent scholar.

Cassiopeia A was a massive star that eventually collapsed in upon itself and blew apart. Its dramatic flare of light took 11,000 years to cross the cosmos, finally reaching Earth in the 17th century, they say.

Today, the former star is familiar to every radio-astronomer as a seething X-ray ember that is no longer visible to the naked eye.

Numerous but sketchy sources point to a celestial sighting in the 17th century, according to the researchers. These observations, though, stretch over 30 years and cluster in the latter part of the century.

Lunn and Rakoczy take a new look at the evidence and calculate that the supernova could indeed have been seen on May 29, 1630, the day when the future Charles II was born.

"The number and variety of sources that refer to the new star strongly suggest that an astronomical event really did take place," Lunn said.

"Our work raises questions about the current method for dating supernovae, but leads to the exciting possibility of solving a decades-old astronomical puzzle."

The idea is being presented at an RAS conference in Llandudno, Wales, gathering around 500 astronomers and space scientists, the Society said in a press release.

The 1642-1651 English civil war focussed on a revolt by parliament against the monarch's claim to have a divine right to rule.

The parliamentary forces, known as Roundheads, executed King Charles I in 1649 and routed the army of his son in 1651.

Charles II returned from exile in 1660 and became dubbed "the Merry Monarch" for his pleasure-loving ways after the era of puritanism.

But he accepted that the monarch reigns with the consent of parliament, the principle that underpins British democracy today.

In 2006, a team of astronomers estimated that a "guest star" noted by Chinese chroniclers in 185 AD was a supernova whose remnants, RCW 86, still glow today in non-visible parts of the energy spectrum.

A supernova spotted in 1572 by the Danish astronomer Tycho Brahe lingered for 18 months.

Its appearance was traumatic for many astronomers at the time, for it destroyed the notion, set in stone by Aristotle, that the Universe was fixed and unchanged. It reputedly was the inspiration for the terrifying celestial portent in Shakespeare's "Hamlet".

 

The Supernova's Secrets Cracked at Last?

By MICHAEL D. LEMONICK

Hank Childs / Lawrence Berkeley National Laboratory

Most stars end their lives in a whimper — our own sun will almost certainly be one of them — but the most massive stars go out with an impressive bang. When that happens, creating what's known as a Type II supernova, the associated blast of energy is so brilliant that it can briefly outshine an entire galaxy, give birth to ultra-dense neutron stars or black holes, and forge atoms so heavy that even the Big Bang wasn't powerful enough to create them. If supernovas didn't exist, neither would gold, silver, platinum or uranium. The last time a supernova went off close enough to earth to be visible without a telescope, back in 1987, it made the cover of TIME.

Given the Type II supernovas' cosmic importance, you might think astronomers would have figured out how they work — and in a general way, they have. But when it comes to the most critical few moments of the detonation process, says Princeton theorist Adam Burrows, you'd be wrong. "We've been working on this for about 50 years," he explains, "but every time we think we've nailed it, the answer turns out to be ambiguous or wrong." (There's an entirely different kind of a supernova by the way, called a Type I, which astronomers don't fully understand either, but that's a different story.)

Thanks to a new, powerful supercomputer simulation, though, reported in the current Astrophysical Journal, Burrows and a group of colleagues at Princeton and Lawrence Berkeley National Laboratory, in California, are convinced they're getting closer. "We're not there yet," he says, "but victory is in sight."

 

Read more: http://www.time.com/time/health/article/0,8599,2021122,00.html#ixzz1WgCATqIp

Model describes universe with no big bang, no beginning, and no end...

How's about the big bang or the lack thereof for a start!

Lisa Zyga @ PhysOrg.com points out an interesting idea,

By suggesting that mass, time, and length can be converted into one another as the universe evolves, Wun-Yi Shu has proposed a new class of cosmological models that may fit observations of the universe better than the current big bang model. What this means specifically is that the new models might explain the increasing acceleration of the universe without relying on a cosmological constant such as dark energy, as well as solve or eliminate other cosmological dilemmas such as the flatness problem and the horizon problem.

Continue reading here.

More information: Wun-Yi Shu. "Cosmological Models with No Big Bang." arXiv:1007.1750v1
via: The Physics ArXiv Blog