Posts Tagged ‘exoplanets

Michio Kaku: The Search for Earth’s Twin (video)

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Written by physicsgg

January 24, 2012 at 7:28 am


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A Galaxy Full of Alien Planets

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160 billion alien planets fill our galaxy in this infographic.

Written by physicsgg

January 11, 2012 at 7:15 pm


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At Last, Earth-Sized Alien Worlds

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Learn about the latest Kepler space telescope discovery of alien Earths, Kepler-20e and Kepler-20f, in this infographic.

NASA Discovers First Earth-size Planets Beyond Our Solar System

NASA’s Kepler mission has discovered the first Earth-size planets orbiting a sun-like star outside our solar system. The planets, called Kepler-20e and Kepler-20f, are too close to their star to be in the so-called habitable zone where liquid water could exist on a planet’s surface, but they are the smallest exoplanets ever confirmed around a star like our sun.

The discovery marks the next important milestone in the ultimate search for planets like Earth. The new planets are thought to be rocky. Kepler-20e is slightly smaller than Venus, measuring 0.87 times the radius of Earth. Kepler-20f is a bit larger than Earth, measuring 1.03 times its radius. Both planets reside in a five-planet system called Kepler-20, approximately 1,000 light-years away in the constellation Lyra.

Kepler-20e orbits its parent star every 6.1 days and Kepler-20f every 19.6 days. These short orbital periods mean very hot, inhospitable worlds. Kepler-20f, at 800 degrees Fahrenheit, is similar to an average day on the planet Mercury. The surface temperature of Kepler-20e, at more than 1,400 degrees Fahrenheit, would melt glass.

Transit light curves

“The primary goal of the Kepler mission is to find Earth-sized planets in the habitable zone,” said Francois Fressin of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., lead author of a new study published in the journal Nature. “This discovery demonstrates for the first time that Earth-size planets exist around other stars, and that we are able to detect them.”

The Kepler-20 system includes three other planets that are larger than Earth but smaller than Neptune. Kepler-20b, the closest planet, Kepler-20c, the third planet, and Kepler-20d, the fifth planet, orbit their star every 3.7, 10.9 and 77.6 days. All five planets have orbits lying roughly within Mercury’s orbit in our solar system. The host star belongs to the same G-type class as our sun, although it is slightly smaller and cooler.

Mass versus radius relation for small planets. Kepler-20 e and Kepler-20 f theoretical mass and observed radius ranges (1σ) are plotted as orange- and greenshaded areas, while the other transiting planets with dynamically determined masses are plotted in black, with 1σ error bars. The curves are theoretical constant-temperature mass–radius relations.

The system has an unexpected arrangement. In our solar system, small, rocky worlds orbit close to the sun and large, gaseous worlds orbit farther out. In comparison, the planets of Kepler-20 are organized in alternating size: large, small, large, small and large.

“The Kepler data are showing us some planetary systems have arrangements of planets very different from that seen in our solar system,” said Jack Lissauer, planetary scientist and Kepler science team member at NASA’s Ames Research Center in Moffett Field, Calif. “The analysis of Kepler data continue to reveal new insights about the diversity of planets and planetary systems within our galaxy.”
Scientists are not certain how the system evolved but they do not think the planets formed in their existing locations. They theorize the planets formed farther from their star and then migrated inward, likely through interactions with the disk of material from which they originated. This allowed the worlds to maintain their regular spacing despite alternating sizes.

The Kepler space telescope detects planets and planet candidates by measuring dips in the brightness of more than 150,000 stars to search for planets crossing in front, or transiting, their stars. The Kepler science team requires at least three transits to verify a signal as a planet.

The Kepler science team uses ground-based telescopes and the Spitzer Space Telescope to review observations on planet candidates the spacecraft finds. The star field Kepler observes in the constellations Cygnus and Lyra can be seen only from ground-based observatories in spring through early fall. The data from these other observations help determine which candidates can be validated as planets.

To validate Kepler-20e and Kepler-20f, astronomers used a computer program called Blender, which runs simulations to help rule out other astrophysical phenomena masquerading as a planet.

On Dec. 5 the team announced the discovery of Kepler-22b in the habitable zone of its parent star. It is likely to be too large to have a rocky surface. While Kepler-20e and Kepler-20f are Earth-size, they are too close to their parent star to have liquid water on the surface.

“In the cosmic game of hide and seek, finding planets with just the right size and just the right temperature seems only a matter of time,” said Natalie Batalha, Kepler deputy science team lead and professor of astronomy and physics at San Jose State University. “We are on the edge of our seats knowing that Kepler’s most anticipated discoveries are still to come.”

Written by physicsgg

December 20, 2011 at 7:37 pm

Kepler-22b: A 2.4 Earth-radius Planet in the Habitable Zone of a Sun-like Star

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Read also: Kepler 22-b: Earth-like planet confirmed

William J. Borucki et al

Folded light curve with model fit in red. Black dots represent individual observations. Dark blue points represent 30-minute binned data, and cyan points represent residuals after fitting. Red asterisk represents the mid-transit times based on the model fit with eccentricity value allowed to float

A search of the time-series photometry from NASA’s Kepler spacecraft reveals a transiting planet candidate orbiting the 11th magnitude G5 dwarf KIC 10593626 with a period of 290 days. The characteristics of the host star are well constrained by high-resolution spectroscopy combined with an asteroseismic analysis of the Kepler photometry, leading to an estimated mass and radius of 0.970 +/- 0.060 MSun and 0.979 +/- 0.020 RSun. The depth of 492 +/- 10ppm for the three observed transits yields a radius of 2.38 +/- 0.13 REarth for the planet.
The system passes a battery of tests for false positives, including reconnaissance spectroscopy, high-resolution imaging, and centroid motion.
A full BLENDER analysis provides further validation of the planet interpretation by showing that contamination of the target by an eclipsing system would rarely mimic the observed shape of the transits.

Image of the star field near Kepler-22

The final validation of the planet is provided by 16 radial velocities obtained with HIRES on Keck 1 over a one year span.
Although the velocities do not lead to a reliable orbit and mass determination, they are able to constrain the mass to a 3{\sigma} upper limit of 124 MEarth, safely in the regime of planetary masses, thus earning the designation Kepler-22b.
The radiative equilibrium temperature is 262K for a planet in Kepler-22b’s orbit.
Although there is no evidence that Kepler-22b is a rocky planet, it is the first confirmed planet with a measured radius to orbit in the Habitable Zone of any star other than the Sun.

Characteristics of Kepler-22 and -22b

Read more: ttp://

Written by physicsgg

December 8, 2011 at 7:11 am


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Kepler 22-b: Earth-like planet confirmed

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Astronomers have confirmed the existence of an Earth-like planet in the “habitable zone” around a star not unlike our own.

The planet, Kepler 22-b, lies about 600 light-years away and is about 2.4 times the size of Earth, and has a temperature of about 22C.

It is the closest confirmed planet yet to one like ours – an “Earth 2.0”.

However, the team does not yet know if Kepler 22-b is made mostly of rock, gas or liquid.

During the conference at which the result was announced, the Kepler team said that it had spotted some 1,094 new candidate planets.

The Kepler space telescope was designed to look at a fixed swathe of the night sky, staring intently at about 150,000 stars. The telescope is sensitive enough to see when a planet passes in front of its host star, dimming the star’s light by a minuscule amount.

Kepler identifies these slight changes in starlight as candidate planets, which are then confirmed by further observations by Kepler and other telescopes in orbit and on Earth.
Kepler 22-b was one of 54 candidates reported by the Kepler team in February, and is just the first to be formally confirmed using other telescopes.

More of these “Earth 2.0” candidates are likely to be confirmed in the near future, though a redefinition of the habitable zone’s boundaries has brought that number down to 48.

Kepler 22-b lies at a distance from its sun about 15% less than the distance from the Earth to the Sun, and its year takes about 290 days. However, its sun puts out about 25% less light, keeping the planet at its balmy temperature that would support the existence of liquid water.

The Kepler team had to wait for three passes of the planet before upping its status from “candidate” to “confirmed”.

“Fortune smiled upon us with the detection of this planet,” said William Borucki, Kepler principal investigator at Nasa’s Ames Research Center.

“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.”

The results were announced at the Kepler telescope’s first science conference, alongside the staggering number of new candidate planets. The total number of candidates spotted by the telescope is now 2,326 – of which 207 are approximately Earth-sized.

In total, the results suggest that planets ranging from Earth-sized to about four times Earth’s size – so-called “super-Earths” – may be more common than previously thought.

Written by physicsgg

December 5, 2011 at 7:59 pm


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The Periodic Table of Exoplanets

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click on this image to see an enlargement

This table summarizes in eighteen thermal-mass categories most of the current known exoplanets (as of October 2011). Planets are divided in six mass classes as mercurians, subterrans, terrans, superterrans, neptunians, and jovians. Planets in the hot zone (first row) are too close to the stars to support liquid water. Planets in the habitable zone (second row) can sustain liquid water if large enough. Planets in the cold zone (third row) are icy-rich bodies. The mean mass (M) and radius (R) of the exoplanets in each category is shown at the bottom of the frames.
    In the Solar System Mercury is an example of a hot mercurian, Venus is on the edge of a hot and warm terran, Mars is on the edge of a warm subterran and mercurian, Jupiter and Saturn are cold jovians, and Uranus and Neptune cold neptunians. Only warm subterrans, terrans, and superterrans are potentially habitable, although warm jovians might have habitable exomoons. The only known mercurian was discovered in the Arecibo Observatory. You can click the image for a higher resolution version. An updated of this table will be available for the Habitable Exoplanets Catalog.

Written by physicsgg

December 5, 2011 at 1:27 pm


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One-Third of Sun-Like Stars Have Earth-Like Planets In Habitable Zone

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Astronomers have calculated the likelihood of finding Earth-like planets around other stars using the latest data from the Kepler mission.

The period and radius of Kepler planets in the sample, around bright stars, are plotted. The lower right corner is relatively empty, probably owing to low SNR there, not because small planets are absent from long periods. The upper left corner is relatively sparse, in spite of an expected high SNR there, implying a deficit of large planets on shortperiod orbits. The left side of the diagram is relatively empty owing to an apparent paucity of planets of all sizes at periods less than 3 days. The right side of the diagram is not completely sampled in the current database, so should be ignored here.

The Kepler orbiting observatory is specifically designed to find Earth-like planets around nearby stars.

Earlier this year, the Kepler team released the mission’s first 136 days of data and it has turned out to be a veritable jackpot. In that time Kepler looked at some 150,000 target stars and found evidence for 1,235 potential exoplanets. That’s quite a haul….. Read the rest of this entry »

Written by physicsgg

September 28, 2011 at 2:08 pm


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The blackest planet

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Astronomers uncover alien world so ‘extraordinarily dark’ it makes coal look shiny
Astronomers have discovered the darkest known planet.
The exoplanet, known as TrES-2b, reflects less than 1 per cent of light, which makes it darker than any other planet or moon.
The discovery, detailed in the journal Monthly Notices of the Royal Astronomical Society, was made by analysing data from Nasa’s Kepler spacecraft, which provides extremely precise measurements on the brightnesses of faraway stars.

Black planet: This artist's impression shows TrES-2b, a planet so hot it glows red like embers, but is also officially the darkest known planet

‘TrES-2b is considerably less reflective than black acrylic paint, so it’s truly an alien world,’ David Kipping of the Harvard-Smithsonian Center for Astrophysics (CfA) told Science Daily.
TrES-2b, a gas exoplanet roughly the size of Jupiter, is around 750 light years away and was discovered in 2006 by the Trans-Atlantic Exoplanet Survey; hence its less-than-catchy name.
The reason it differs from other similar-sized planets is that Jupiter, for example, is surrounded by ammonia clouds that reflect more than one third of its sunlight.
TrES-2b has no ammonia clouds to reflect light because it is extremely hot….. Read the rest of this entry »

Written by physicsgg

August 12, 2011 at 9:25 am


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