From today’s New York Times (winner of 101 Pulitzers, far more than any other news organization):
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Astronomers Find Planet Closer to Size of Earth

By DENNIS OVERBYE
Published: April 21, 2009

European astronomers said Tuesday that they had discovered the smallest planet yet found orbiting another star. The planet could be as little as only 1.9 times as massive as the Earth and belongs to a dim red star known as Gliese 581, which lies about 20 light-years from Earth in the constellation Libra.

The star was already known to harbor at least three more massive planets. The new planet, known as Gliese 581e, is probably rocky like the Earth, but it lies in such a close orbit — only three million miles from its star — that it is surely blasted with too much radiation and heat to be livable.

Michel Mayor, of Geneva Observatory, and his colleagues announced their results at a conference at the University of Hertfordshire in Britain and in a paper submitted to the journal Astronomy and Astrophysics.

Astronomers said the discovery was more encouragement that the galaxy was full of small-mass planets and that with more time and improved instruments like the Kepler satellite, recently launched by NASA, they would eventually find Earth-like planets in orbits suitable for life around other stars.

“Finding Earth-like planets with lukewarm temperatures is the next great goal,” Geoff Marcy, of the University of California, Berkeley, a planet-hunting rival of Dr. Mayor’s, said in an e-mail message.

“This is the most exciting discovery in exoplanets so far,” Dr. Marcy said.

Dr. Mayor’s group also discovered the first exoplanet, a gas giant 160 times the mass of the Earth, in 1995, using a technique known popularly as the “wiggle” method that detects planets by a slight gravitational tug they give their stars. The method is most sensitive to massive planets in close orbits. In a statement, Dr. Mayor noted that the new planet is only one-eightieth of the mass of the first one, saying, “This is tremendous progress in 14 years.”

The discovery also cements the Gliese system as one of the most promising exoplanet systems. Two years ago, the third planet from that star was hailed as a ”Goldilocks” planet, where liquid water and thus life might be possible, until calculations showed that the greenhouse effect would broil it.

But the new data also shifted the orbit of the star’s outermost planet inward so that it now appears to revolve in the so-called habitable zone where liquid water is possible, according to Stéphane Udry of Geneva University, one of the team members.

That planet, 581d, is about seven times as massive as the Earth, Dr. Udry explained, which is too big to be just rock. It probably formed as a combination of ice and rock farther out in the Gliese system and then migrated inward, according to various planetary formation models, and melted. He called it the first serious “water world candidate.”

Sara Seager, a planet theorist at the Massachusetts Institute of Technology, said in an e-mail message that the Gliese planetary system “is like the gift that keeps on giving.”

Nice, and how do you get there?

;JOOP!

Since it’s twenty light years away, a round trip will take at least four decades. It might be a good idea to take your rocketship in for a tune-up today.

I beg your pardon; 4 decades?
Let’s assume you find a way and energy to constantly accelerate
to a (say) 90% of the speed of light.
Now, how many G-forces can you stand and for how long?
I made the calculations when I was a schoolboy and ....
.... instantly gave up and never watched Startrek again.

;JOOP!

Well, if you accelerate at 1G, you’d get to the speed of light in, oh, about a year.  Then you need to decelerate at the same rate; that’s another year (assuming the relative velocity between us and Gliese is near 0...)

The problem is the size of your fuel tanks… They have to be infinite in capacity to accelerate to the speed of light, since as your velocity increases, your mass increases exponentially (that whole pesky E=mc2 thing).

But wait.  Einstein’s theory of General Relativity also postulated that time itself is relative, so the faster you go, and thus the more massive you become, the slower your own frame of reference becomes with respect to time.  Thus, as you approach infinite mass, your time asymptotically slows to zero, meaning you never get there.

That’s why Roddenberry’s explanation in Trek-land was so “elegant.” For the non-Trekkers that might happen to care (not scotch, since TV is the antichrist.. :) ) - Roddenberry’s explanation was that the Warp ships never exceeded the speed of light, or anything near it.  They just changed space around the vessel to a form in which the speed of light was MUCH MUCH MUCH MUCH faster than normal space.  Same thing was later postulated by Hawking, Sagan, etc.

we are not alone!

Trust NO ONE!!!

[sciuriware] I beg your pardon; 4 decades?
Let’s assume you find a way and energy to constantly accelerate
to a (say) 90% of the speed of light.
Now, how many G-forces can you stand and for how long?

Notice I said at least four decades. The universal speed limit is 186,000 miles per second (approximately), which is a law of physics. (Exceed the speed of light and God will write you a citation.) How fast and much your particular rocketship can accelerate and how many G’s you can withstand and whether you arrive and return alive or dead is your own affair.

[Mogut] we are not alone!

Here we are closer to the point. The significance of more and more exo-planets (only a bit more than a decade ago quite a few self-appointed experts scoffed at the idea of a galaxy or universe filled with planets of any kind) and more and more earth-like planets has nothing necessarily to do with space travel (which is why my original reply to sciuriware dripped sarcasm).

[LovemyMotif] Trust NO ONE!!!

And here we are further from the point. The difficulties apply both ways.

[TonyPhillips] That’s why Roddenberry’s explanation in Trek-land was so “elegant.” For the non-Trekkers that might happen to care (not scotch, since TV is the antichrist.. :) ) -

I do consider television an abomination, but I’m not religious about it. It so happens I’ve seen every episode of both Star Trek Classic and Next Generation at least once at some point or other. Since I’ve twice referred in this forum to an incident in one particular episode, had you been around longer and paying close attention, you might have remembered my familiarity with the series.

The episode in question had to do with a Romulan prison camp in which two generations of Klingons were held, the younger of which grew up with little exposure to Klingon culture, Klingon religion especially--speaking of religion. Worf, having infiltrated the camp, attempts to ameliorate the situation by giving Sunday school lessons. One of his charges asks if the events Worf recounts really happened, if the lore he imparts is “true”. Worf answers sagely that he “[finds] many truths” in it.” Although the Klingon religion is a fictitious religion (no one actually practices it), the Star Trek writers are obviously making a didactic point about real religions. This is the sort of thing Star Trek at its best was good at. The many truths you may find in it have little to do with physics.

Roddenberry’s explanation was that the Warp ships never exceeded the speed of light, or anything near it.  They just changed space around the vessel to a form in which the speed of light was MUCH MUCH MUCH MUCH faster than normal space.  Same thing was later postulated by Hawking, Sagan, etc.

You seem to have a knack for getting in over your head (and our heads) in technical matters. Carl Sagan was an astronomer, not a physicist. His novel Contact, which is work of fiction, has his protagonist evade the speed of light problem by traveling through a wormhole.

The problem is the size of your fuel tanks… They have to be infinite in capacity to accelerate to the speed of light, since as your velocity increases, your mass increases exponentially (that whole pesky E=mc2 thing).

Its just a small thought but as your speed increases and the mass of your spaceship increases thus making it harder to push, nonetheless, the mass of your fuel also increases by the same rate, so surely the two effects are cancelled out or at least relatively cancelled out.

Heinlein explored this whole space travel/time dilation in many of his Juveniles - they were a lot of fun and he had a reasonable grasp of the science.

These days, Star trek nothwithstanding, most writers seem to resort to the now tried and tested route of the wormhole to move personel and machinery from one end of the universe to the other. Peter F hamilton’s writings are great space operas of the modern era and they lean heavily on this idea.

Realistically, getting to those planets would most likely be a one way trip made in relatively slow but rather huge ‘ark’ ships - whole colonies of people on a voyage that would take possibly more than one generation to achieve. Why? Because at this point in time no one knows how to make wormholes and get there any quicker.

Cheers

This thread was not supposed to be about exo-planets, but since we seem to be stuck on space travel for now, let’s examine the non-science-fiction part of Tony’s post a little more carefully:

[TonyPhillips] Well, if you accelerate at 1G, you’d get to the speed of light in, oh, about a year.  Then you need to decelerate at the same rate; that’s another year (assuming the relative velocity between us and Gliese is near 0...)

A quibble: Close to the speed of light in about a year.

The problem is the size of your fuel tanks… They have to be infinite in capacity to accelerate to the speed of light, since as your velocity increases, your mass increases exponentially (that whole pesky E=mc2 thing).

Since your mass increases the faster you travel, a body (defined as a thing with mass) can never quite reach the speed of light, so add an infinitesimal quantity to my “four decades”.

But wait. Einstein’s theory of General Relativity also postulated that time itself is relative, so the faster you go, and thus the more massive you become, the slower your own frame of reference becomes with respect to time.  Thus, as you approach infinite mass, your time asymptotically slows to zero, meaning you never get there.

Reminiscent of Zeno’s paradox (of motion). In fact, you get there sooner in respect to your frame of reference than in respect to a stationary frame of reference. My “four decades” apply to a hypothetical observer on earth, not necessarily to the traveler.

As always: don’t buy tickets yet.

;JOOP!

Carl Sagan was an astronomer, not a physicist.

He was both.  He earned a PhD in astrophysics from the University of Chicago in 1960.  I understand and stipulate to the argument that astrophysics is a branch of astronomy, but I don’t think it’s fair to the holder of those credentials to say they’re not physicists…

Things relativistic make my noggin implode, but I enjoy discussing the consequences.

What happens if I travel near the speed of light (say, 0.99% of c), and you do the same, but in the opposite direction (a vector that is collinear, but opposite in magnitude) at the same velocity.  Newtonian physics say that if I measure your closing speed, you should appear to be traveling at 1.9800… of c, but Special Relativity says you’d only appear to be traveling at 0.999949498.. of c…

Then we have the direct evidence of particles actually traveling faster than light (but not in a vacuum) such as the Cherenkov Radiation seen when electrons hit water and are forced to slow down by about 25% because they’re going faster than allowed. 

I can make something travel faster than light.  If I put a laser on a turntable, and oriented the turntable such that the plane intersected the moon, as long as the turntable is rotating faster than 6 rpm, the “dot” moves across the moon’s surface faster than the speed of light… But that’s a “Thing,” not a body with mass.  No real practical notion there.

It’s fun… Most of my interest is purely the layman’s theory.  But occasionally practice as well.  For example, if you have a GPS in your car:  That system has to take into account the shifts in the atomic clocks due to varying gravity fields and motion vectors to arrive at a stable solution of position.  For a “THEORY” of relativity, there sure are a lot of practical consequences…

Fun stuff…

Oh, and to keep this on topic, that quoted article made no mention of the method they used to discover this object.  Was it an occulting phenomenon or a wobble?  It HINTED that it was “Wobble,” but the direct reference was to something detected that was MUCH larger.

[TonyPhillips] He was both.  He earned a PhD in astrophysics from the University of Chicago in 1960.  I understand and stipulate to the argument that astrophysics is a branch of astronomy, but I don’t think it’s fair to the holder of those credentials to say they’re not physicists…

I’ve actually read two biographies of Sagan, and as I remember, his doctorate (from the University of Chicago, yes--which he entered at age sixteen) is in astronomy. He was living in downtown Madison with his first wife Lynn Margolis (the famous biologist, then finishing her doctorate at UW-Madison) and doing research in northern Wisconsin. It looks, however, as if you’ve checked this and I’m willing to take your word. Might he have got a dual degree? I do remember also that he studied both biology and physics at a lower level. As long as we’re fussing, though, it’s worth pointing out that a degree is not a profession, and I think we can agree that Sagan worked primarily as a planetary astronomer (not counting teaching, writing, and appearing on television). I have no idea what you mean by “stipulate to”.

Anyway, the point is that you need to specify where Sagan “postulated” the “[changing of] space around [a] vessel to a form in which the speed of light was MUCH MUCH MUCH MUCH faster than normal space.” I’ve read all of Sagan’s books except Comet--which I skimmed. (I haven’t read any of his scientific papers, but one of his later popular works lists them by title--a bit defensively, I suppose.) While you’re at it, you might specify where Stephen Hawking “postulated” it as well. I’ve read his A Brief History of Time and have a copy handy.

Then we have the direct evidence of particles actually traveling faster than light (but not in a vacuum) such as the Cherenkov Radiation seen when electrons hit water and are forced to slow down by about 25% because they’re going faster than allowed.

It might be clearer if you’d said “but not traveling faster than light does in a vacuum” rather than just “but not in a vacuum.” These particles don’t help us with space travel. In a vacuum is implicit in the phrase the speed of light as heretofore used in this thread. Light can appear to travel more slowly through certain media, and it is this lower speed exceeded in this case.

[sciuriware] As always: don’t buy tickets yet.

To Gliese 581e? Who is selling them? (Who proposes that we travel there?) What do you mean by “as always”? (If we never buy tickets to or for anything “yet”, then we never buy them at all, which means we never go anywhere or to anything unless admission is free or we sneak in illegally.)

You said it.

;JOOP!