Starship Asterisk*

Snow Leopard wrote:It is thought that Alpha Centauri A has an Earth-like terrestrial world at placement 4 - hence, the name of the planet is designated Alpha Centauri Majorum IIII. Distance of planet to parent star is expected to be approximately 1.47 AU. The planet is thought to have two moons - one large moon with a sparse atmosphere and one small moon which orbits in the distance. The two moons are tidally bound to the planet, like the Earth-Moon system, so that the same side of each faces the planet. Two additional planets must exist beyond Alpha Centauri Majorum IIII. An asteroid field probably exists at about 6 AU. Beyond the asteroid field is the realm of Alpha Centauri B.

Jim Leff wrote:
This is not huge astronomical news, given that we've already found some 842 extrasolar planets. But this may represent a turning point for humanity. If a planet is found within that habitable zone, human imagination will turn toward Alpha Centauri B. It's starting to look like the next destination.

Even at the dizzying speed of our Voyager spacecrafts, it's a 40,000 year journey. But now there's fresh impetus to develop some of the interesting proposed means for human-viable interstellar travel. http://en.wikipedia.org/wiki/Interstellar_travel

• "We choose to go to Alpha Centauri in this millennium and do the other things, not because they are easy, but because they are hard, because that goal will serve to organize and measure the best of our energies and skills, because that challenge is one that we are willing to accept, one we are unwilling to postpone, and one which we intend to win, and the others, too."

• After multiple gravity assists the 5,600 kg Cassini spacecraft finally left the Earth/Moon system at just ~3 km/s shy of Solar System escape velocity. Presumably a Saturn V could place a 47,000 kg spacecraft into a similar (near solar system escape velocity) trajectory.
  
  Such a 47,000 kg spacecraft could (given an effect Xenon ion exhaust velocity (Ve) of 29 km/s) launch a ~800 kg interstellar probe that escapes the solar system at a velocity of 120 to 150 km/s = a relative velocity vis-a-vis α Centauri of 140 to 170 km/s.
  
  Such a probe could reach α Centauri (or Barnard's star) in from 7700 to 9400 years.

Devil Particle wrote:Pardon the crude drawing but does the calculation of the mass of the planet take into consideration the inclination of its orbit?

[3] Using the radial velocity method, astronomers can only estimate a minimum mass for a planet as the mass estimate also depends on the tilt of the orbital plane relative to the line of sight, which is unknown. But, from a statistical point of view, this minimum mass is often close to the real mass of the planet.

neufer wrote: One wouldn't want to send humans for all sorts of reasons

neufer wrote: But it would probably be silly to consider any voyage that would take more than 1,000 years

Though the new world is being branded the planet next door, it's still four light-years away. It would take our best current robotic spacecraft about 40,000 years to travel that distance, estimated Greg Laughlin, an astrophysicist at the University of California, Santa Cruz, who was not part of the Swiss team but who participated in the press conference.

That could change, however, "if there's a public groundswell to get to Alpha Centauri," Laughlin said—for example, if other planets are found orbiting Alpha Centauri B, especially in the system's habitable zone, where temperatures would be friendly to life.

In that case, he said, "it's possible that new technology could be developed to get a spacecraft there from Earth in a human's life span."

Grizzly wrote:
Nipticking, I know, but if the planet's orbit is that close in to the star, shouldn't the star in the image be considerably larger?

Jim Leff wrote:

neufer wrote:
One wouldn't want to send humans for all sorts of reasons

• Such as?

• ________ Scientific American JUNE 1960
  
  "Putting a man in space is a stunt: the man can do no more
  than an instrument, in fact can do less." So said Vannevar Bush,
  chairman of the Board of Governors of the Massachusetts Institute
  of Technology, in a statement to the House Committee on Science
  and Astronautics. "There are far more serious things to do than to
  indulge in stunts. As yet the American people do not understand the
  distinctions, and we in this country are prone to rush, for a time, at
  any new thing. I do not discard completely the value of demonstrating
  to the world our skills. Nor do I undervalue the effect on morale of
  the spectacular. But the present hullabaloo on the propaganda
  aspects of the program leaves me entirely cool."

Jim Leff wrote:

neufer wrote: One wouldn't want to send humans for all sorts of reasons

Such as?

Hukadarn wrote:
I remember that Javiera Guedes (Department of Astronomy and Astrophysics, University of California) in 2008 published a paper in the Astrophysical Journal with the results of simulations ( using the softwares Mercury and Systemic) which indicated that Alpha Centauri B could offer conditions to the formation of a planet with a mass similar to Earth in its orbit (and others some with!).

• Hmmmm......Javiera Guedes

Hukadarn wrote:I remember that Javiera Guedes (Department of Astronomy and Astrophysics, University of California) in 2008 published a paper in the Astrophysical Journal with the results of simulations ( using the softwares Mercury and Systemic) which indicated that Alpha Centauri B could offer conditions to the formation of a planet with a mass similar to Earth in its orbit (and others some with!).

Below the final distribution of orbits in different simulation times, not encouraging?

https://lh5.googleusercontent.com/-1y6H ... oard02.jpg

The paper and additional details of the simulations can be read here:

- http://arxiv.org/abs/0802.3482
- https://webhome.phys.ethz.ch/~jguedes/alphacen.html

[ ]´s

• Astrophysical Journal 679(2) 1582 (2008 Jun 01) DOI: 10.1086/587799
  arXiv.org > astro-ph > arXiv:0802.3482 > 25 Feb 2008 (v1), 17 Mar 2008 (v3)