Planets Plentiful Around Abundant Red Dwarf Stars, Study Says

Good news for planet-hunters: planets around red dwarf stars are more abundant than previously believed, according to new research. A new study — which detected eight new planets around these stars — says that “virtually” all red dwarfs have planets around them. Moreover, super-Earths (planets that are slightly larger than our own) are orbiting in the habitable zone of about 25% of red dwarfs nearby Earth.

“We are clearly probing a highly abundant population of low-mass planets, and can readily expect to find many more in the near future – even around the very closest stars to the Sun,” stated Mikko Tuomi, who is from the University of Hertfordshire’s centre for astrophysics research and lead author of the study.

The find is exciting for astronomers as red dwarf stars make up about 75% of the universe’s stars, the study authors stated.

The researchers looked at data from two planet-hunting surveys: HARPS (High Accuracy Radial Velocity Planet Searcher) and UVES (Ultraviolet and Visual Echelle Spectrograph), which are both at the European Southern Observatory in Chile. The two instruments measure the effect a planet has on its parent star, specifically by examining the gravitational “wobble” the planet’s orbit produces.

An artist's concept of a rocky world orbiting a red dwarf star. (Credit: NASA/D. Aguilar/Harvard-Smithsonian center for Astrophysics).
An artist’s concept of a rocky world orbiting a red dwarf star. (Credit: NASA/D. Aguilar/Harvard-Smithsonian center for Astrophysics).

Putting the information from both sets of data together, this amplified the planet “signals” and revealed eight planets around red dwarf stars, including three super-Earths in habitable zones. The researchers also applied a probability function to estimate how abundant planets are around this type of star.

The planets are between 15 and 80 light years away from Earth, and add to the 17 other planets found around low-mass dwarfs. Scientists also detected 10 weaker signals that could use more investigation, they said.

The study will be available shortly in the Monthly Notices of the Royal Astronomical Society and is available in preprint version at this link.

Source: University of Hertfordshire

Is That Planet Habitable? Look To The Star First, New Study Cautions

Finding Earth 2.0, in the words of noted SETI researcher Jill Tarter, is something a lot of exoplanet searchers are hoping for one day. They’re trying not to narrow down their search to Sun-like stars, but also examine stars that are smaller, like red dwarfs.

A new study, however, cautions that the X-ray environment of these dwarfs may give us false positives. They looked at Earth-mass planets in the neighborhood of four stars, such as GJ 667 (which has three planets that could be habitable), and concluded it’s possible for oxygen to reside in these planets even in the absence of life.

The work builds on a published paper in the Astrophysical Journal that argues that GJ 876, studied by the Hubble Space Telescope, could allow a hypothetical planet to have plenty of oxygen in its atmosphere, even without the presence of life.

This artist's conception shows the newly discovered super-Earth GJ 1214b, which orbits a red dwarf star 40 light-years from our Earth. Credit: Credit: David A. Aguilar, CfA
This artist’s conception shows the newly discovered super-Earth GJ 1214b, which orbits a red dwarf star 40 light-years from our Earth. Credit: Credit: David A. Aguilar, CfA

The researchers themselves, however, caution that the results are preliminary and there is a lot more to study before coming to a definitive conclusion.

For example: “The effects of stellar flares on the atmosphere of the hypothetical Earth-like planet around GJ 876 have not been considered in this work,” stated Kevin France, who is with the University of Colorado at Boulder and also a co-author.

“At this point, we do not have a sufficient understanding of the amplitude and frequency of such flares on older, low-mass exoplanet host stars to make predictions about their impact on the production of biomarker signatures.”

The report was presented at the American Astronomical Society division for planetary sciences meeting in Denver today (Oct. 7). It was not immediately clear from a press release if the newer study has been submitted for peer review.

Source: AAS Division for Planetary Sciences

First Cloudy Alien Planet Spotted From Earth

Call it cloudy with a low chance of meatballs. The alien world Kepler-7b — a very reflective world in big telescopes — has clouds in its upper atmosphere. And scientists have actually been able to map those out, despite the planet’s great distance from Earth (at least 1,000 light-years away.)

It’s the first time scientists have been able to map out clouds on a world outside of the solar system. If we can see clouds, then we can begin to think about what a planet’s climate will be, making this an important milestone in understanding the conditions on other worlds.

“Kepler-7b reflects much more light than most giant planets we’ve found, which we attribute to clouds in the upper atmosphere,” stated Thomas Barclay, Kepler scientist at NASA’s Ames Research Center. “Unlike those on Earth, the cloud patterns on this planet do not seem to change much over time — it has a remarkably stable climate.”

Illustration of the Kepler spacecraft (NASA/Kepler mission/Wendy Stenzel)
Illustration of the Kepler spacecraft (NASA/Kepler mission/Wendy Stenzel)

Here’s how scientists got it done:

  • Preliminary observations with the Kepler space telescope –which was designed to hunt planets until a second reaction wheel failed earlier this year — found “moon-like phases” on Kepler-7b. These showed a bright spot on the western  hemisphere.
  • NASA’s Spitzer Space Telescope measured Kepler-7b’s temperature using infrared light, calculating it at between 1,500 and 1,800 degrees Fahrenheit (815 and 982 degrees Celsius.)
  • Something was clearly going on, as the planet is extremely close to its star; only 0.06 Earth-sun distances away. The temperature was too cool. They figured out that the light was reflected off cloud tops on the planet’s west side.

Another cool fact — Kepler-7b, like Saturn, would float if it was put in a big enough tub of water!

You can read more details in the technical paper online here. The study, which was led by the Massachusetts Institute of Technology, has been accepted to the Astrophysical Journal, but not published yet.

Source: NASA

How Spitzer’s Focus Changed To Strange New Worlds

After 10 years in space — looking at so many galaxies and stars and other astronomy features — the Spitzer Space Telescope is being deployed for new work: searching for alien worlds.

The telescope is designed to peer in infrared light (see these examples!), the wavelength in which heat is visible. When looking at infrared light from exoplanets, Spitzer can figure out more about their atmospheric conditions. Over time, it can even detect brightness differences as the planet orbits its sun, or measure the temperature by looking at how much the brightness declines when the planet goes behind its star. Neat stuff overall.

“When Spitzer launched back in 2003, the idea that we would use it to study exoplanets was so crazy that no one considered it,” stated Sean Carey of NASA’s Spitzer Science Center, which is at the California Institute of Technology. “But now the exoplanet science work has become a cornerstone of what we do with the telescope.”

Of course, the telescope wasn’t designed to do this. But to paraphrase the movie Apollo 13, NASA was interested in what the telescope could do while it’s in space — especially because the planet-seeking Kepler space telescope has been sidelined by a reaction wheel problem. Redesigning Spitzer, in a sense, took three steps.

Classifying Galaxies
An example of Spitzer’s past work: This image from NASA’s Spitzer Space Telescope shows infrared light from the Sunflower galaxy, otherwise known as Messier 63. Spitzer’s view highlights the galaxy’s dusty spiral arms. Image credit: NASA/JPL-Caltech

Fixing the wobble: Spitzer is steady, but not so steady that it could easily pick out the small bit of light that an exoplanet emits. Engineers determined that the telescope actually wobbled regularly and would wobble for an hour. Looking into the problem further, they discovered it’s because a heater turns on to keep the telescope battery’s temperature regulated.

“The heater caused a strut between the star trackers and telescope to flex a bit, making the position of the telescope wobble compared to the stars being tracked,” NASA stated. In October 2010, NASA decided to cut the heating back to 30 minutes because the battery only needs about 50 per cent of the heat previously thought. Half the wobble and more exoplanets was more the recipe they were looking for.

The Spitzer Space Telescope.  Credit:  NASA
The Spitzer Space Telescope. Credit: NASA

Repurposing a camera: Spitzer has a pointing control reference sensor “peak-up” camera on board, which originally gathered up infrared light to funnel to a spectrometer. It also calibrated the telescope’s star-tracker pointing devices. The same principle was applied to infrared camera observations, putting stars in the center of camera pixels and allowing a better view.

Remapping a camera pixel: The scientists charted the variations in a single pixel of the camera that showed them which were the most stable areas for observations. For context, about 90% of Spitzer’s exoplanet observations are about a 1/4 of a pixel wide.

That’s pretty neat stuff considering that Spitzer’s original mission was just 2.5 years, when it had coolant on board to allow three temperature-sensitive science instruments to function. Since then, engineers have set up a passive cooling system that lets one set of infrared cameras keep working.

Source: NASA

Super-Earth’s Probable Water Atmosphere Revealed In Blue Light

Playing with the filters on a telescope can show us amazing things. In a recent case, Japanese astronomers looked at the star Gilese 1214 in blue light and watched its “super-Earth” planet (Gliese 1214 b, or GJ 1214 b) passing across the surface from the viewpoint of Earth. The result — a probable detection of water in the planet’s atmosphere.

Observations with the Subaru Telescope using a blue filter revealed the atmosphere does not preferentially scatter any light. If the Rayleigh scattering had been observed, this would have shown hydrogen in the atmosphere, researchers said. (On Earth, Rayleigh scattering of the atmosphere makes the sky blue.)

“When combined with the findings of previous observations in other colors, this new observational result implies that GJ 1214 b is likely to have a water-rich atmosphere,” stated the National Astronomical Observatory of Japan.

This finding confirms work performed in 2010 (where scientists concluded the planet was mainly made of water) and adds on to information in 2012, where infrared measurements with the Hubble Space Telescope revealed a possible steamy waterworld under a thick atmosphere.

The planet is an ideal candidate for exoplanet observations because it is relatively close to Earth (40 light years away) and is about 2.7 times the size of our planet, allowing for possible comparisons between the worlds.

Three images showing the relationship between the atmosphere's composition and the transmitted colors of light. Top: Hydrogen-dominated atmospheres see much of the blue light scattered, meaning that transits become more visible in blue  light than red light. Middle: Atmospheres with less hydrogen scatter blue wavelengths more weakly. Bottom: Cloud-covered planets make it more difficult for light to make its way up through the atmosphere, even if it is dominated by hydrogen. Credit: NAOJ
Three images showing the relationship between the atmosphere’s composition and the transmitted colors of light. Top: Hydrogen-dominated atmospheres see much of the blue light scattered, meaning that transits become more visible in blue light than red light. Middle: Atmospheres with less hydrogen scatter blue wavelengths more weakly. Bottom: Cloud-covered planets make it more difficult for light to make its way up through the atmosphere, even if the atmosphere is dominated by hydrogen.
Credit: NAOJ

There’s still some debate over whether “super-Earths” are closer in nature to Earth or to Uranus or Neptune (each about four times Earth’s diameter), requiring scientists to scrutinize that class of exoplanets to learn more about their properties.

One area under investigation is where the super-Earths form. It is believed that planets arise out of a protoplanetary disk, or cloud of gas, ice and debris that surrounds a young star at the beginning of its life. Hydrogen is a big part of this disk, as well as water ice beyond the “snow line“, or the region in a planetary system where waning heat makes it possible for ice to form.

“Findings about where super-Earths have formed and how they have migrated to their current orbits point to the prediction that hydrogen or water vapor is a major atmospheric component of a super-Earth,” NAOJ stated. “If scientists can determine the major atmospheric component of a super-Earth, they can then infer the planet’s birthplace and formation history.”

The team acknowledges it’s still possible there is hydrogen in GJ 1214 b’s atmosphere, but add their findings do corroborate with past ones suggesting water.

Source: NAOJ

Smile! This Could Be The Lightest Alien Planet Ever Captured On Camera

We’ve found hundreds of planets outside the solar system, but taking a picture of one is still something quite special. The light of the parent star tends to greatly overwhelm the faint light of the alien planet. (So usually we learn about planets by tracking the effects each planet has on its star, like dimming light when it passes in front or making the star slightly wobble.)

This picture (above) shows HD95086 b, which astronomers believe is one of only about a dozen exoplanets ever imaged. It’s 300 light-years from Earth. The planet candidate is about four to five times the mass of Jupiter and orbiting a very young star that is probably only 10 million to 17 million years old. That’s a baby compared to our own solar system, estimated at 4.5 billion years old.

We still have a lot to learn about this object (and the observations from the Very Large Telescope will need to be confirmed independently), but so far astronomers say they figure that planet formed in the gas and dust surrounding star HD 95086. But the planet is actually very far away from the star now, about twice the distance as the Sun-Neptune orbital span in our own solar system.

The Very Large Telescope (VLT) at ESO's Cerro Paranal observing site.  Located in the Atacama Desert of Chile, the site is over 2600 metres  above sea level, providing incredibly dry, dark viewing conditions. The  VLT is the worldâ??s most advanced optical  instrument, consisting         of four Unit Telescopes with main mirrors 8.2-m in diameter and   four movable 1.8-m diameter Auxiliary        Telescopes. The telescopes  can work together, in groups of two or  three, to form a giant  interferometer, allowing astronomers to see  details up to 25 times  finer than with  the individual telescopes. Credit: European Southern Observatory
The Very Large Telescope (VLT) at ESO’s Cerro Paranal observing site. Credit: European Southern Observatory

“Its current location raises questions about its formation process,” stated team member Anne-Marie Lagrange, who is with the Grenoble Institute of Planetology and Astrophysics in France.

“It either grew by assembling the rocks that form the solid core and then slowly accumulated gas from the environment to form the heavy atmosphere, or started forming from a gaseous clump that arose from gravitational instabilities in the disc.

“Interactions between the planet and the disc itself,” she added, “or with other planets may have also moved the planet from where it was born.”

Astronomers estimate the planet candidate has a surface temperature of 1,292 degrees Fahrenheit (700 degrees Celsius), which could allow water vapor or methane to stick around in the atmosphere. It will take more VLT observations to figure this out, though.

The results from this study will be published in Astrophysical Journal Letters. The paper is also available on prepublishing site Arxiv.

Source: European Southern Observatory

Rocky Alien Planets: What The Heck Is On Their Surfaces?

We don’t have the budget yet to send Star Trek‘s U.S.S. Enterprise to probe the surface of strange new worlds, but luckily for humanity, astronomers are figuring out techniques to do that without even needing to leave Earth.

One of Earth’s prolific planet-hunters, the Kepler Space Telescope, has found a lot of planet candidates with rocky surfaces. That’s exciting for astronomers, as rocky planets tend to be smaller than their gas giant counterparts. Also, learning more about rocky planets could give us more clues as to Earth’s history, and that of other planets in our solar system.

But how the heck, from so far away, can we begin to understand the surface? One idea: Check the heat signature, or in more scientific words, look at exoplanets in the infrared part of the light spectrum.

The visible colors, infrared, radio, X-rays and gamma rays are all forms of light and comprise the electromagnetic spectrum. Here you can compare their wavelengths with familiar objects and see how their frequencies (bottom numbers) increase with decreasing wavelength. Credit: ESA
The visible colors, infrared, radio, X-rays and gamma rays are all forms of light and comprise the electromagnetic spectrum. Here you can compare their wavelengths with familiar objects and see how their frequencies (bottom numbers) increase with decreasing wavelength. Credit: ESA

NASA’s Astrobiology Magazine recently published an article about this method, which we encourage you to check out. In summary, the team behind a new research paper (submitted to the Astrophysical Journal) proposes to check out “airless” exoplanets that have surface temperatures below 3,140 degrees Fahrenheit (1,726 Celsius or 2,000 Kelvin.)

Because different kinds of rocks emit “signature” spectrums in different wavelengths, it’s possible we could pick up the signs of silicate rocks or other types of material. There’s a caveat, though.

“With current technology, however, the team cautions that determining surface composition of exoplanets is a very different process than studying their solar system counterparts,” the magazine wrote. “Due to the limits of technology, the team proposes to concentrate on the most prominent mineral signatures detected from exoplanets.”

Check out more details in the scientific journal article here, or the entire Astrobiology Magazine article at this link.