Red Dwarf

Earth-like Planets Are Right Next Door
Cambridge, MA - Using publicly available data from NASA's Kepler space telescope, astronomers at the Harvard-Smithsonian Center for Astrophysics (CfA) have found that six percent of red dwarf stars have habitable, Earth-sized planets. Since red dwarfs are the most common stars in our galaxy, the closest Earth-like planet could be just 13 light-years away.

"We thought we would have to search vast distances to find an Earth-like planet. Now we realize another Earth is probably in our own backyard, waiting to be spotted," said Harvard astronomer and lead author Courtney Dressing (CfA).

Dressing presented her findings today in a press conference at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.

Red dwarf stars are smaller, cooler, and fainter than our Sun. An average red dwarf is only one-third as large and one-thousandth as bright as the Sun. From Earth, no red dwarf is visible to the naked eye.

About Stars: Red DwarfsSpectral class: M, K

Red dwarfs are the most frequent and most inconspicuous stars in the universe. Red dwarfs have between eight percent and the half of the mass of the Sun and shine in red. The reason for this is their low surface temperature of 2500 - 4000 kelvin.

Red dwarfs live very long, in any case longer than the universe is old now. Therefore they are so numerous. In groups of new born stars they haven't got this frequency, because the bigger stars are all still there.

Many red dwarfs should have planets. But with red light photosynthesis is more difficult and less effective. So life there would have different conditions. Furthermore planets, that are near enough to get sufficient energy, are tidally locked. This means, they show their star always the same side. It is debatable if under such conditions the planet could keep an atmosphere, but if so there would be very strong storms.

Stars aren't quiet on their surface. There are often eruptions, so called flares. Many young red dwarfs are flare stars with frequent and heavy eruptions, increasing their brightness enormously for a short time.

Subdwarfs are very old stars which lie below the main sequence. So they are too dim for their color. The reason for this is that due to their age they contain only very few heavy elements.

A pair of red dwarfs, Gliese 623 A and the tiny B. Photo: C. Barbieri (Univ. of Padua), NASA, ESA

Red dwarfs – also called M-dwarfs after of their classification on the Hertzsprung–Russell diagram – are stars that are smaller and cooler than our Sun, and therefore the planetary systems around them are scaled down accordingly. McKay and Gilliam calculate that a planet would have a surface temperature of –179 degrees Celsius in a zone between 0.63 and 1.66 astronomical units (99 million and 248 million kilometers around the star Gliese 581, an M3-type red dwarf located 20.5 light years away. Four planets have already been confirmed orbiting Gliese 581, but none within the ‘liquid methane habitable zone’. Two more planets have been claimed to exist in the system, and one of these would fall within the zone, at 0.76 astronomical units, but evidence for the existence of this world has provenhighly controversial. Alternatively, the liquid methane habitable zone around a cooler M4 type red dwarf would be even closer in, between 0.084 astronomical units and 0.23 astronomical units (12.6 million kilometers to 34.4 million kilometers.

A radar image revealing a large methane/ethane sea on Titan (the black areas) with islands and a shoreline. Image: NASA/JPL

Astronomers Find Super-Earth Orbiting Red Dwarf Star; May Have Atmosphere 16/12/09
A super-Earth is defined as a planet between one and ten times the mass of the Earth. The newfound world, GJ1214b, is about 6.5 times as massive as the Earth. Its host star, GJ1214, is a small, red type M star about one-fifth the size of the Sun. It has a surface temperature of only about 4,900 degrees F and a luminosity only three-thousandths as bright as the Sun.
"Despite its hot temperature, this appears to be a waterworld," said Zachory Berta, a graduate student at the Harvard-Smithsonian Center for Astrophysics (CfA) who first spotted the hint of the planet among the data. "It is much smaller, cooler, and more Earthlike than any other known exoplanet."

Light Warping/Mass Transfer Interactions Red/White Dwarf Binarys 05/04/13
The dead star, also called a white dwarf, is the burnt-out core of what used to be a star like our sun. It is locked in an orbiting dance with its partner, a small "red dwarf" star. While the tiny white dwarf is physically smaller than the red dwarf, it is more massive. When the white dwarf passed in front of its star, its gravity caused the starlight to observably bend and brighten.

13.5 Billion Exo-earths Orbiting Red Dwarfs Across the Galaxy 14/03/13

Many red dwarfs are flare stars, occasionally increasing significantly in brightness. Flares seen on these little red stars can put the solar flares we see on the sun to shame. They’re also correspondingly more lethal, brightening the star’s electromagnetic output from radio waves all the way up to x rays!

Paradoxically, the same magnetic activity powering these flares also causes dramatic starspot activity — just like sunspots, only much much more so.

Because a red dwarf is so much smaller than the sun, and its magnetic fields are so much stronger, starspots can cause the brightness of these grouchy little stars to drop by up to 40 percent. I hasten to add that not all red dwarfs are quite so volatile. But many of them are.

Red Dwarf Stars May Be Best Chance for Habitable Alien Planets 23/02/12

Red dwarfs, also known as M stars, are dim compared to stars like our sun and are just 10 to 20 percent as massive. They make up roughly three-quarters of the stars in the galaxy, and recently scientists found red dwarfs are far more common than before thought, making up at least 80 percent of the total number of stars.
The fact that red dwarfs are so very common has made astrobiologists wonder if they might be the best chance for discovering planets habitable to life as we know it. More and more planets are getting discovered around red dwarfs — for instance, a potentially habitable "super-Earth" at least 4.5 times the mass of Earth, GJ 667Cb, was recently found orbiting the red dwarf GJ 667C.

Red Dwarfs Luminosity Between 1/10,000 and 10% of Sun 30/09/08

According to the Hertzsprung-Russell diagram, a red dwarf star is a small and relatively cool star, of the main sequence, either late K or M spectral type. They constitute the vast majority of stars and have a mass of less than one-half that of the Sun (down to about 0.075 solar masses, which are brown dwarfs) and a surface temperature of less than 3,500 K. Red dwarfs are very low mass stars with no more than 40% of the mass of the Sun. Consequently they have relatively low temperatures in their cores and energy is generated at a slow rate through nuclear fusion of hydrogen into helium via the proton-proton (PP) chain mechanism. Thus these stars emit little light, sometimes as little as 1/10,000th that of the Sun. Even the largest red dwarf has only about 10% of the Sun's luminosity. In general red dwarfs transport energy from the core to the surface by convection.

Red Dwarfs Compromise 70% of stars in Milky Way With Habitable Life Zones 11/01/08

The researchers were looking for habitable zones around red dwarf stars, which can be 50-90% smaller than the Sun and much cooler. The comprise 70% of the stars in the Milky Way, but they’re harder to spot because they put out less light.

They were surprised to learn that these red dwarf stars have tiny habitable zones. When they added up the habitable zones of 44 red dwarf stars nearby the Sun, they found they didn’t add up to equal the habitable zone of a single Sun like star.

Read more: http://www.universetoday.com/12423/red-dwarfs-have-teeny-tiny-habitable-zones/#ixzz2gsdgVid8

Red Dwarf Kids Astronomy

Red Dwarf stars are smaller than our sun. And since they are smaller, they also have less mass. Because of their small size, these stars burn their fuel very slowly, which allows them to live a very long time. This also causes these stars to not shine as brightly as others. Some red dwarf stars will live trillions of years before they run out of fuel.

Why are red dwarf stars red?
Because red dwarf stars only burn a little bit of fuel at a time, they are not very hot compared to other stars. Think of a fire. The coolest part of the fire is at the top of the flame where it glows red, the hotter part in the middle glows yellow, and the hottest part near the fuel glows blue. Stars work the same way. Their temperature determines what color they are. Thus, we can determine how hot a star is just by its color.

Red dwarf stars are by far the most common type of star in outer space. However, very few stars that you see in the sky are red dwarfs. This is because they are so small and make very little light. Imagine standing on a mountain. Pretend that there are one million kids 5 miles away holding flashlights, and 20 miles away there is a lighthouse for ships. You will most likely not see any of the flashlights, while you will very easily see the lighthouse. If the flashlights all glowed as brightly as the lighthouse they would blind you. Likewise, if all the red dwarf stars glowed as bright as the bigger stars, our nighttime sky would be very bright.

Ancient Red Dwarf Pass by~ Smithsonian photo link