A team of planet hunters has announced the discovery of a planet with three times the mass of Earth orbiting a nearby star at a distance that places it squarely in the middle of the star’s “habitable zone.”
This discovery was the result of more than a decade of observations using the W. M. Keck Observatory in Hawaii, one of the world’s largest optical telescopes. The research placed the planet in an area where liquid water could exist on the planet’s surface. If confirmed, this would be the most Earth-like exoplanet yet discovered and the first strong case for a potentially habitable one.
To astronomers, a “potentially habitable” planet is one that could sustain life, not necessarily one where humans would thrive. Habitability depends on many factors, but having liquid water and an atmosphere are among the most important. The new findings are based on 11 years of observations of the nearby red dwarf star Gliese 581 using the HIRES spectrometer on the Keck I Telescope. The spectrometer allows precise measurements of a star’s radial velocity (its motion along the line of sight from Earth), which can reveal the presence of planets. The gravitational tug of an orbiting planet causes periodic changes in the radial velocity of the host star. Multiple planets induce complex wobbles in the star’s motion, and astronomers use sophisticated analyses to detect planetsand determine their orbits and masses.
“Keck’s long-term observations of the wobble of nearby stars enabled the detection of this multi-planetary system,” said Mario R. Perez, Keck program scientist at NASA Headquarters in Washington. “Keck is once again proving itself an amazing tool for scientific research.” Steven Vogt, professor of astronomy and astrophysics at UC Santa Cruz, and Paul Butler of the Carnegie Institution lead the Lick-Carnegie Exoplanet Survey.
“Our findings offer a very compelling case for a potentially habitable planet,” said Vogt. “The fact that we were able to detect this planet so quickly and so nearby tells us that planets like this must be really common.”
The paper reports the discovery of two new planets around Gliese 581. This brings the total number of known planets around this star to six, the most yet discovered in a planetary system outside of our own. Like our solar system, the planets around Gliese 581 have nearly-circular orbits.
The new planet designated Gliese 581g has a mass three to four times that of Earth and orbits its star in just under 37 days. Its mass indicates that it is probably a rocky planet with a definite surface and enough gravity to hold on to an atmosphere. Gliese 581, located 20 light years away from Earth in the constellation Libra, has two previously detected planets that lie at the edges of the habitable zone, one on the hot side (planet c) and one on the cold side (planet d). While some astronomers still think planet d may be habitable if it has a thick atmosphere with a strong greenhouse effect to warm it up, others are skeptical. The newly-discovered planet g, however, lies right in the middle of the habitable zone.
The planet is tidally locked to the star, meaning that one side is always facing the star and basking in perpetual daylight, while the side facing away from the star is in perpetual darkness. One effect of this is to stabilize the planet’s surface climates, according to Vogt. The most habitable zone on the planet’s surface would be the line between shadow and light (known as the “terminator”).
- adapted from a NASA news announcement
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This week’s stargazing news includes observing Jupiter at its best, finding elusive Uranus and watching Northern Lights on the web with project Auroramax.
Tags: AuroraMax, Jupiter, Uranus
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Viewing the northern lights just hit primetime this week with the launch of a LIVE online observatory installed on the outskirts of the city of Yellowknife in the Northwest Territories, Canada and run by the Canadian Space Agency. Called AuroraMax, a camera equipped with a fish eye lens snaps an image of the entire overhead sky every 10 seconds, making near real time views of auroras available to anyone with an internet connection.
Check out the entire website AuroraMax here
The hope is that it won’t just offer an entertainment alternative to the late night TV talk shows but actually help demystify some of the science behind the Northern Lights and bring attention to research being done on the solar-terrestrial relationship. When night-time falls in Yellowknife the camera is turned on…I have the live feed from that camera you can check out at the bottom of my rightside column….
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Officially changing seasons at 11:09 pm ET tonight, Autumn will be welcomed in by a giant full Moon for the first time in 20 years! The word equinox comes from Latin meaning “equal night” and refers to the 12 hour long day and night that occurs only on this particular day of the year.
Skywatchers looking at the mid-day position of the sun over the summer season will notice that it has been slowly sinking closer to the southern horizon, resulting in ever longer shadows. On the autumnal equinox the Sun reaches its halfway point in its migration towards its lowest point in the midday sky, which happens on the December solstice. It’s only on the spring and autumnal equinox that the Sun rises due east and sets due west.
Astronomically speaking the September equinox marks one of the four major turning points in the cycle of seasons. The Earth spins on its axis, which is tilted at 23.5 degrees with respect to its orbital plane. On these days however the Earth’s axis is neither tilted away nor towards the Sun, but has both northern and southern hemispheres experiencing equal amounts of sunshine.
The equinox is really a geometrical alignment of the Earth with the Sun, when the sun appears positioned right above our planet’s equator. As autumn progresses the Sun appears to continue its travels south until the winter solstice, when it slowly begins its journey north.
As the golden orb rises in the eastern sky as the sun sets int he west you may notice a superbright star next to it – that is the planet Jupiter. Together the pair will ride high into the southern sky int he overnight hours and set in the west as the sun rises in the east.
Adding to the celestial delight will be Jupiter parking itself as close as it will get this year to the seventh and most elusive planet in the solar system – Uranus. The planetary duo will be separated by less than 1 degree – meaning they will only be 2 full moon disks apart! Promises to be quite a sight in binoculars and particularly through small telescopes. don’t worry if you miss the show tonight – the two planets will remain close for the upcoming few months - but what’s a few million miles between friends, eh?
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Big skywatching news this week is that planet Jupiter is at its best -biggest and brightest- in the evening sky for the next two weeks. While there has been a lot of buzz surrounding the fact that the gas giant is the closest to Earth on Sept.20th – at closest opposition since the year 1951 – it really won’t be the only chance to see it at its best. In fact any clear night the next couple months will offer up amazing views of the largest planet in the solar system. Here is a little observers guide I wrote up for National Geogprahic this week.
To find Jupiter just look towards the eastern horizon around sunset and higher up the southern sky later at night. You can’t miss it because it will be the brightest star-like object in the entire night sky. Don’t forget to use your binoculars – they will show off the four largest moons of Jupiter lined up beside it. Even the smallest of telescopes will show you the cloud bands that encircle the gas giant and you might even be able to glimpse the famous Great Red Spot – the giant hurricane three times the size of Earth. Definitely worth stepping outside any clear night!
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Two asteroids will pass within the Moon’s distance from Earth on Wednesday, Sept. 8. and should be visible with moderate-sized amateur telescopes, say scientists . But no need to fret, neither will hit Earth. But the numbers will raise eyebrows I think… RX30 is estimated to be 32 to 65 feet in size and will pass within 154,000 miles of Earth at 5:51 a.m. EDT Wednesday. The second object, RF12, estimated to be 20 to 46 feet in size, will pass within 49,000 miles at 5:12 p.m. EDT.
Wired.com is reporting “According to NASA’s Near Earth Object impact risk tables, the odds that 2010 RF12 will hit the Earth are about 1 in 50, and the odds of an impact with 2010 RX30 are less than 1 in 1000. Both objects are too small to do much damage even if they were to smack into the Earth; much of their rocky mass probably wouldn’t survive the trip through Earth’s atmosphere. Because of their small sizes, they won’t be visible with the naked eye. But they should be bright enough to observe with a modest-sized telescope…”
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For the next two weeks keen skywatchers in the Northern Hemisphere can hunt down one of the most elusive astronomical phenomena visible in the sky – the Zodiacal Light. This pyramid-shaped beam of light is easily mistaken for lights of a far-off city just over the dark horizon in the countryside and has also been called the ‘false dawn’. But this light is more ethereal; it is caused by sunlight reflecting off cosmic dust between the planets.
The next two weeks in September will be the best time to track down this ghostly light in the eastern sky before morning twilight. But you will have to head out of the city into a dark location to spot it because it can be easily lost in light pollution. Look towards the eastern horizon, where the sun rises, about an hour before it comes up.
Ancient Romans thought this ghostly glow was due to far-off camp fires below the horizon, while the ancient Greeks speculated that it must be caused by distant volcanic explosions. Centuries later, by the mid sixteenth-century people thought that the Zodiacal Light was the outstretched atmosphere of our Sun.
Zodiacal Light results from sunlight reflecting off a vast field of meteoric dust that lies in the plane of the solar system and stretches out far beyond Earth. It actually formed when the solar system was first evovling . Billions of dust-sized particles that were left behind, after the planets formed about 5 billion years ago. It’s amazing to think that about 40% of the overall light in the night sky can be attributed to this Zodiacal dust cloud.
Tags: False Dawn, Zodiacal Lights
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