When you walk outside and look at the horizon, you can’t immediately tell that the Earth is round. That’s because we can’t observe it on a scale that really gives us an honest look at the whole Earth.
Of course when we leave the surface, it becomes clearer. Likewise, if we can take certain measurements from different vantage points, geometry can tell us a lot about the size of our planet. Eratosthenes did this in ancient Egypt, over two millennia ago.
Ethan Siegel, in his typically great fashion, tells you all about if we can use similar methods to measure the shape of our universe at Starts With A Bang.
December 05, 2011
Imaged Above: This artist’s conception illustrates Kepler-22b, a planet known to comfortably circle in the habitable zone of a sun-like star. Image credit: NASA/Ames/JPL-Caltech
NASA’s Kepler mission has confirmed its first planet in the “habitable zone,” the region around a star where liquid water could exist on a planet’s surface. Kepler also has discovered more than 1,000 new planet candidates, nearly doubling its previously known count. Ten of these candidates are near-Earth-size and orbit in the habitable zone of their host star. Candidates require follow-up observations to verify they are actual planets.
The newly confirmed planet, Kepler-22b, is the smallest yet found to orbit in the middle of the habitable zone of a star similar to our sun. The planet is about 2.4 times the radius of Earth. Scientists don’t yet know if Kepler-22b has a predominantly rocky, gaseous or liquid composition, but its discovery is a step closer to finding Earth-like planets.
Previous research hinted at the existence of near-Earth-size planets in habitable zones, but clear confirmation proved elusive. Two other small planets orbiting stars smaller and cooler than our sun recently were confirmed on the very edges of the habitable zone, with orbits more closely resembling those of Venus and Mars.
“This is a major milestone on the road to finding Earth’s twin,” said Douglas Hudgins, Kepler program scientist at NASA Headquarters in Washington. “Kepler’s results continue to demonstrate the importance of NASA’s science missions, which aim to answer some of the biggest questions about our place in the universe.”
Kepler discovers planets and planet candidates by measuring dips in the brightness of more than 150,000 stars to search for planets that cross in front, or “transit,” the stars. Kepler requires at least three transits to verify a signal as a planet.
“Fortune smiled upon us with the detection of this planet,” said William Borucki, Kepler principal investigator at NASA Ames Research Center at Moffett Field, Calif., who led the team that discovered Kepler-22b. “The first transit was captured just three days after we declared the spacecraft operationally ready. We witnessed the defining third transit over the 2010 holiday season.”
Cosmic Civilizations: The Kardashev Scale
A civilization that is able to harness all of the power available on a single planet — has approximately 1016 or 1017 Watts available. Earth specifically has an available power of 1.74 ×1017 W (174 peta watts, see Earth’s energy budget). Kardashev’s original definition was 4 ×1012 W — a “technological level close to the level presently attained on earth” (“presently” meaning 1964).
A civilization that is able to harness all of the power available from a single star, approximately 4 ×1026 W. Again, this figure is variable; the Sun outputs approximately 3.86 ×1026 W. Kardashev’s original definition was also 4 ×1026 W.
A civilization that is able to harness all of the power available from a single galaxy, approximately 4 ×1037 W. This figure is extremely variable, since galaxies vary widely in size; the stated figure is the approximate power output of the Milky Way. Kardashev’s original definition was also 4 ×1037 W.
A civilization that has harnessed the power of its supercluster, or “the largest gravitationally bound structure it originated in.” For the Local Supercluster, this would be approximately 1042 W. Dr. Michio Kaku has discussed a type IV civilization, which could harness “extragalactic” energy sources such as dark energy, in his book Parallel Worlds.
A civilization that uses the entire resources of its respective universe.
“We had no equals. We controlled the fundamental forces of the entire universe. Nothing could communicate with us on our level.”
Flame Nebula Close-Up
Also known as NGC 2024, the nebula’s suggestive reddish color is due to the glow of hydrogen atoms at the edge of the giant Orion molecular cloud complex some 1,500 light-years away.
Image Credit & Copyright: Adam Block, Mt. Lemmon SkyCenter, U. Arizona
Large spiral galaxy Messier 74 lies 30 million light years away from the Earth, positioned face-on to us. Astronomers call Messier 74 a “grand design” spiral galaxy with well defined spiral arms. From here we see Messier 74 through a screen of foreground stars in our galaxy, the Milky Way, which bears resemblance to it.
Credit: Canada-France-Hawaii Telescope/Coelum
Some interesting new additions to the exoplanet family were announced last week by astronomers from Penn State University. While finding exoplanets these days may be considered “just another day at the office,” astronomers discovered three unique planets and an additional “mystery” object. What’s unique about these planets is the fact that the stars they orbit are all old and dying – red giant stars which have swollen up as they near the end of their lives, which ordinarily would consume any unlucky planets which may be too close to escape.
The three stars are HD 240237, BD +48 738, and HD 96127; the second one also has the mystery object orbiting it, which may be another planet, a low-mass star or a brown dwarf — something whose mass is in between that of a smaller, cooler star and a giant planet.
“We will continue to watch this strange object and, in a few more years, we hope to be able to reveal its identity,” said team leader, Alex Wolszczan.
The subject of planets orbiting dying stars will also be the focus of an upcoming conference, Planets Around Stellar Remnants, in Puerto Rico next January. It is organized by Penn State’s Center for Exoplanets and Habitable Worlds, and will take place exactly 20 years since Wolszczan made his discovery.