Another planet, called Keplerb, turns out to orbit two stars. A sunset there would provide a view of two setting stars! An illustration that shows what it might look like to stand on the surface of Keplerb.
The planets are relatively close together, too. It has also made a list of more than 3, additional potential exoplanets that astronomers need to study more carefully to be sure that they are indeed planets.
While Kepler primarily searched within one particular patch of the sky, TESS is observing the entire sky to locate thousands of planets orbiting the nearest and brightest stars. The James Webb Space Telescope, set to launch in , will also observe many of the exoplanets we have discovered and help scientists reveal details about these distant worlds. Who knows? One day, by studying exoplanets and distant solar systems, astronomers hope to answer the intriguing question: Is there life elsewhere in our galaxy?
The Short Answer:. Over the course of thousands of years, gravity causes pockets of dense matter inside the nebula to collapse under their own weight. Because the dust in the nebulae obscures them, protostars can be difficult for astronomers to detect. As a protostar gets smaller, it spins faster because of the conservation of angular momentum—the same principle that causes a spinning ice skater to accelerate when she pulls in her arms. Increasing pressure creates rising temperatures, and during this time, a star enters what is known as the relatively brief T Tauri phase.
Most of the stars in our galaxy, including the sun, are categorized as main sequence stars. They exist in a stable state of nuclear fusion, converting hydrogen to helium and radiating x-rays.
This process emits an enormous amount of energy, keeping the star hot and shining brightly. Some stars shine more brightly than others. Their brightness is a factor of how much energy they put out—known as luminosity —and how far away from Earth they are. Color can also vary from star to star because their temperatures are not all the same.
Hot stars appear white or blue, whereas cooler stars appear to have orange or red hues. By plotting these and other variables on a graph called the Hertzsprung-Russell diagram, astronomers can classify stars into groups. Along with main sequence and white dwarf stars, other groups include dwarfs, giants, and supergiants. Supergiants may have radii a thousand times larger than that of our own sun.
Stars spend 90 percent of their lives in their main sequence phase. Now around 4. As stars move toward the ends of their lives, much of their hydrogen has been converted to helium. Helium sinks to the star's core and raises the star's temperature—causing its outer shell of hot gases to expand.
These large, swelling stars are known as red giants. The red giant phase is actually a prelude to a star shedding its outer layers and becoming a small, dense body called a white dwarf. White dwarfs cool for billions of years. Some, if they exist as part of a binary star system , may gather excess matter from their companion stars until their surfaces explode, triggering a bright nova.
Eventually all white dwarfs go dark and cease producing energy. At this point, which scientists have yet to observe, they become known as black dwarfs. Massive stars eschew this evolutionary path and instead go out with a bang—detonating as supernovae. While they may appear to be swelling red giants on the outside, their cores are actually contracting, eventually becoming so dense that they collapse, causing the star to explode.
These catastrophic bursts leave behind a small core that may become a neutron star or even, if the remnant is massive enough, a black hole.
The familiar eyeball shape of the Helix Nebula shows only two dimensions of this complex celestial body. But new observations suggest it may actually be composed of two gaseous disks nearly perpendicular to each other. See Subscription Options. Go Paperless with Digital. Laurence A. Marschall in the department of physics at Gettysburg College in Gettysburg, Pa. Get smart.
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