Mayur's Posterous

Spectacular Pictures of Earth as Seen from the International Space Station | International Space Fellowship

These spectacular pictures are  shot by the Expedition 25 crew members aboard the International Space Station flying 220 miles above Earth on Oct. 28.  The Expedition 25 astronauts used the ESA-built Cupola  observatory module to make these amazing nighttime pictures of planet Earth.

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How many habitable planets are there in the galaxy? | Bad Astronomy | Discover Magazine

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By now you may have heard the report that as many as 1/4 of all the sun-like stars in the Milky Way may have Earth-like worlds. Briefly, astronomers studied 166 stars within 80 light years of Earth, and did a survey of the planets they found orbiting them. What they found is that about 1.5% of the stars have Jupiter-mass planets, 6% have Neptune-mass ones, and about 12% have planets from 3 – 10 times the Earth’s mass.

This sample isn’t complete, and they cannot detect planets smaller than 3 times the Earth’s mass. But using some statistics, they can estimate from the trend that as many as 25% of sun-like stars have earth-mass planets orbiting them!

 

 

Like mass?

Now, there’s a very important caveat here: these are planets that have the same mass as Earth, but that doesn’t mean they are very earth-like. The planets the team could find were very close to their parent stars, so they’d be very hot, and uninhabitable. But the good news is that if that trend in mass they saw is correct, the Milky Way is littered with planets the mass of the Earth! If some of them are in the habitable zone of their star… well.

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So a funny thing: I was thinking about this very problem a couple of days ago, but from a different angle. How many habitable planets are there in the Milky Way? Not just earth-mass, but also orbiting their star in the so-called Goldilocks Zone, where temperatures are right for liquid water?

There’s a way to estimate it. And it involves the planet recently announced, Gliese 581g. This planet is about 3 times the Earth’s mass, and it orbits its star in the right place. We don’t know what it’s made of, if it has an atmosphere, or really very much about it at all! But given its mass and temperature, it’s potentially habitable.

The distance to the Gliese 581 system is what gets me excited: it’s 20 light years away. That’s close, compared to the vast size of our galaxy. So let’s assume Gliese 581g is the closest potentially habitable planet to us. Given that assumption, we can estimate the number of potentially habitable planets in the entire Milky Way! And the math’s not even that hard.
 

 

The not-so-hard math

Extrapolating from our one example, let’s say that habitable planets are roughly 20 light years apart in the galaxy (as we’ll see, that number can be a lot bigger or smaller, and the end result is still cool). That means there’s one star per cube 20 light years on a side:

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In the drawing, each box is centered on a star, and the two stars are 20 light years apart. That means the cubes are 20 light years on a side, right? If we assume stars with livable planets are distributed throughout the galaxy like this, then there is one star per 20 x 20 x 20 = 8000 cubic light years. That’s the density of habitable planets in the galaxy.

So how many cubic light years are there in the galaxy?

A lot. Let’s say the Milky Way is a stubby cylinder 100,000 light years across, and 2500 light years thick. The equation of volume of a cylinder is

volume = π x radius of disk2 x height of disk

so

volume = π x 50,0002 x 2500 = 2 x 1013 cubic light years

Holy wow! That’s 20 trillion cubic light years!

Now we just divide the volume of the galaxy by the density of stars with planets to get

2 x 1013 / 8000 = 2,500,000,000 planets

Oh my. Yeah, let that sink in for a second. That’s 2.5 billion planets that are potentially habitable!

 

 

What does this mean?

Well, that’s a whole lot of planets! That’s what it means.

What’s cool, too, is that this number isn’t all that far off from what you can estimate using the report from yesterday. Something like 25% of the stars in the galaxy are like the Sun (that’s a rough estimate, but close enough). That’s 50 billion stars. If 25% of those have earth-mass planets, that’s about 13 billion total, about five times the number I got. I’d call that pretty close! We made a lot of guesses here, so even a factor of ten isn’t so bad. And we’re not really comparing apples to apples, either, since they were looking for earth-mass planets, and I was looking for earth-like planets.

So think about it: 2.5 billion habitable planets is roughly enough for every man, woman, and child on Earth to each have a planet. You can see why I’m not too concerned with the exact math. Even if my numbers are way off, there could be as few as hundreds of millions of planets, or as many as maybe hundreds of billions in our galaxy alone that we could live on!

Again, the point being that mathematically speaking, there may be a lot of habitable planets out there. And who knows; some may be marginally habitable and we can terraform them. And then there are moons of worlds, too… I don’t think I’m speaking too far out of school if I were to speculate that for every perfect Terra Nova out there, there might be three or four more planets we could live on with some work.

Of course, I’m ignoring how we’d get there! But that’s an engineering problem, and given enough time — oh, say, a century or two — I imagine we can overcome a lot of those issues.

If, and when, we do, there will be a lot of real estate out there to poke around in.

Per ardua, ad astra!

 

 

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Japan from outer space

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Both pictures taken by Soichi Noguchi during his stay with the ISS (posted to his Twitter account http://twitter.com/Astro_Soichi) The first picture is Tokyo, the second one is Kyoto, Osaka and Kobe.

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That's what she said.

0r2vm

 

 

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BBC News - UN's outer space chief on extra terrestrial life

The United Nations has a little-known agency called the UN Office for Outer Space Affairs.

Head of the agency, Professor Mazlan Othman, dismissed recent reports that she was to become the first port of call for alien visitors.

But the Malaysian astrophysicist said the possibility of discovering extra terrestrial life, even if just microbes, was increasing.

 

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BBC News - Virgin Galactic's spaceship makes solo flight

Virgin Galactic's spaceship makes solo flight

By Jonathan Amos Science correspondent, BBC News
Drop test (Virgin Galactic)  

The Enterprise spaceship is released from underneath the Eve carrier plane

Virgin Galactic's suborbital spaceship, Enterprise, has made its first solo test flight, in California.

The spaceship was carried to an altitude of 45,000ft (13,700m) by an aeroplane and then dropped to glide back to the Mojave Air and Space Port.

Enterprise will soon be taking people prepared to pay $200,000 (£126,000) on short hops above the atmosphere.

The British billionaire behind the project, Sir Richard Branson, was on hand to witness the drop test.

"This was one of the most exciting days in the whole history of Virgin," the entrepreneur said.

"For the first time since we seriously began the project in 2004, I watched the world's first manned commercial spaceship landing on the runway at Mojave Air and Space Port and it was a great moment."

Virgin Galactic is aiming to become the world's first commercial space line, and has already taken deposits from 370 customers who want to experience a few minutes of weightlessness on a suborbital flight.

The Enterprise ship is based on the X-Prize-winning SpaceShipOne vehicle, which made history in 2004 by successfully flying to 100km (60 miles) in altitude twice in a two-week period.

The new ship, built by Mojave's Scaled Composites company, is bigger and will be capable of carrying eight people - two crew and six passengers.

When it eventually enters service, Enterprise will be carried to its launch altitude by the "Eve" carrier plane before being released in mid-air. Enterprise will then ignite its single hybrid rocket engine to make the ascent to space.

Although Eve and Enterprise have made several test flights together, Sunday was the first time the spaceplane had been released at altitude.

Two pilots were at the controls, Pete Siebold and Mike Alsbury. They guided the ship back to the Mojave runway.

The entire flight took about 25 minutes. On later test flights, Enterprise will fire its rocket engine.

Only when engineers are satisfied all systems are functioning properly will passengers be allowed to climb aboard.

 

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All of human history

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Earth-Like Planet Can Sustain Life : Discovery News

A new member in a family of planets circling a red dwarf star 20 light-years away has just been found. It's called Gliese 581g, and the 'g' may very well stand for Goldilocks.

Gliese 581g is the first world discovered beyond Earth that's the right size and location for life.

"Personally, given the ubiquity and propensity of life to flourish wherever it can, I would say that the chances for life on this planet are 100 percent. I have almost no doubt about it," Steven Vogt, professor of astronomy and astrophysics at University of California Santa Cruz, told Discovery News.

The discovery caps an 11-year effort to tease out information from instruments on ground-based telescopes that measure minute variations in starlight caused by the gravitational tugs of orbiting planets.

Planet G -- the sixth member in Gliese 581's family -- orbits right in the middle of that system's habitable region, where temperatures would be suitable for liquid water to pool on the planet's surface.

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"This is really the first 'Goldilocks' planet, the first planet that is roughly the right size and just at the right distance to have liquid water on the surface," astronomer Paul Butler, with the Carnegie Institution in Washington, D.C., told reporters during a conference call Wednesday.

"Everything we know about life is that it absolutely requires liquid water," he added. "The planet has to be the right distance from the star so it's not too hot, not too cold...  and then it has to have surface gravity so that it can hold on to a substantial atmosphere and allow the water to pool."

With a mass three times larger than Earth's, the newly discovered world has the muscle to hold atmosphere. Plus, it has the gift of time.  Not only is its parent star especially long-lived, the planet is tidally locked to its sun -- similar to how the moon keeps the same side pointed at Earth -- so that half the world is in perpetual light and the other half in permanent darkness.  As a result, temperatures are extremely stable and diverse.

"This planet doesn't have days and nights. Wherever you are on this planet, the sun is in the same position all the time. You have very stable zones where the ecosystem stays the same temperature... basically forever," Vogt said. "If life can evolve, it's going to have billions and billions of years to adapt to the surface."

"Given the ubiquity of water, it seems probable that this thing actually has liquid water. On the surface of the Earth, everywhere you have liquid water you have life," Vogt added.

The question wouldn't be to defend that there is life at Gliese 581g, says Butler. "The question," he said, "would be to demonstrate that there isn't."

Current technologies won't allow scientists to study the planet's atmosphere for chemical signs of life, but astronomers expect many more similar life-friendly planets to be discovered soon. If one or more of those cross the face of their parent star, relative to our line of sight, then it's possible to gather atmospheric data.

"This system is not in an orientation such that this planet would ever transit, so unfortunately this is not a case where nature has thrown us a bone," Vogt noted. "That being said, it is so close and we have found this thing so soon that it suggests we will start finding a lot of these things in the future and eventually we will find systems that do transit. This is a harbinger of things to come."

The research appears in this week's issue of Astrophysical Journal.

I want to go there.

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Around the Solar System - The Big Picture

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Naked Black Hole Builds Future Galactic Dream Home | Wired Science

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Astronomers have spied a distant black hole in the act of creating the galaxy that will eventually become its home.

By sending a jet of gas and highly energetic particles into a neighboring galaxy, the black hole has touched off star formation at a rate 100 times the galactic average.

“Our study suggests that supermassive black holes can trigger the formation of stars, thus ‘building’ their own host galaxies,” David Elbaz, lead author of a paper on the work in the journal Astronomy and Astrophysics, said in a press release. “This link could also explain why galaxies hosting larger black holes have more stars.”

phot-46b-09-fullresThe quasar HE0450-2958, located about 5 billion light-years from Earth, is powered by a supermassive black hole. Unlike all other known quasars, this one did not appear to be surrounded by a galaxy, which had puzzled astronomers. They thought perhaps the quasar’s surrounding galaxy was obscured by dust.

So, in the latest observations they looked in the mid-infrared part of the spectrum, in which dust shines brightly, using the European Southern Observatory’s Very Large Telescope. But they didn’t see dust, confirming the idea that the quasar really is “naked.”

Instead of a surrounding galaxy, Elbaz’s team found the black hole was blasting its neighbor with energy and matter. That injection has caused the observed flurry of star births: 350 new suns are bursting into existence each year in the region.

Eventually, the black hole will merge with its neighbor. The two objects are located 22,000 light-years apart and are moving towards each other at less than 125 miles per second. In tens of millions of years, HE0450-2958 will finally get a home.

“This would provide a natural explanation for the missing host galaxy,” Elbaz and his co-authors wrote.

Images: 1) Artist’s rendering of HE450-2958 and its galactic neighbor.
2) Composite image of HE450-2958 composed of imagery from Hubble, Very Large Telescope, and the Advanced Camera for Surveys.

See Also:

WiSci 2.0: Alexis Madrigal’s Twitter, Google Reader feed, and green tech history research site; Wired Science on Twitter and Facebook.

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