Focusing On ‘Second-Earth’ Candidates In The Kepler Catalog

Artist’s impression of how an infant earth might look. Credit: ESO.

The ongoing hunt for exoplanets has yielded some very interesting returns in recent years. All told, the Kepler mission has discovered more than 4000 candidates since it began its mission in March of 2009. Amidst the many “Super-Jupiters” and assorted gas giants (which account for the majority of Kepler’s discoveries) astronomers have been particularly interested in those exoplanets which resemble Earth.

And now, an international team of scientists has finished perusing the Kepler catalog in an effort to determine just how many of these planets are in fact “Earth-like”. Their study, titled “A Catalog of Kepler Habitable Zone Exoplanet Candidates” (which will be published soon in the Astrophysical Journal), explains how the team discovered 216 planets that are both terrestrial and located within their parent star’s “habitable zone” (HZ).

The international team was made up of researchers from NASA, San Francisco State University, Arizona State University, Caltech, University of Hawaii-Manoa, the University of Bordeaux, Cornell University and the Harvard-Smithsonian Center for Astrophysics. Having spent the past three years looking over the more than 4000 entries, they have determined that 20 of the candidates are most like Earth (i.e. likely habitable).

As Stephen Kane, an associate professor of physics and astronomy at San Fransisco University and lead author of the study, explained in a recent statement:

“This is the complete catalog of all of the Kepler discoveries that are in the habitable zone of their host stars. That means we can focus in on the planets in this paper and perform follow-up studies to learn more about them, including if they are indeed habitable.”

In addition to isolating 216 terrestrial planets from the Kepler catalog, they also devised a system of four categories to determine which of these were most like Earth. These included “Recent Venus”, where conditions are like that of Venus (i.e. extremely hot); “Runaway Greenhouse”, where planets are undergoing serious heating; “Maximum Greenhouse”, where planets are within their star’s HZ; and “Recent Mars”, where conditions approximate those of Mars.

From this, they determined that of the Kepler candidates, 20 had radii less than twice that of Earth (i.e. on the smaller end of the Super-Earth category) and existed within their star’s HZ. In other words, of all the planets discovered in our local Universe, they were able to isolate those where liquid water can exist on the surface, and the gravity would likely be comparable to Earth’s and not crushing!

This is certainly exciting news, since one of the most important aspects of exoplanet hunting has been finding worlds that could support life. Naturally, it might sound a bit anthropocentric or naive to assume that planets which have similar conditions to our own would be the most likely places for it to emerge. But this is what is known as the “low-hanging fruit” approach, where scientists seek out conditions which they know can lead to life.

“There are a lot of planetary candidates out there, and there is a limited amount of telescope time in which we can study them,” said Kane. “This study is a really big milestone toward answering the key questions of how common is life in the universe and how common are planets like the Earth.”

Professor Kane is renowned for being one of the world’s leading “planet-hunters”. In addition to discovering several hundred exoplanets (using data obtained by the Kepler mission) he is also a contributor to two upcoming satellite missions – the NASA Transiting Exoplanet Survey Satellite (TESS) and the European Space Agency’s Characterizing ExOPLanet Satellite (CHEOPS).

These next-generation exoplanet hunters will pick up where Kepler left off, and are likely to benefit greatly from this recent study.

Further Reading: arXiv

The post Focusing On ‘Second-Earth’ Candidates In The Kepler Catalog appeared first on Universe Today.

Life On Kepler-62f?

Exoplanet Kepler 62f would need an atmosphere rich in carbon dioxide for water to be in liquid form. Artist's Illustration: NASA Ames/JPL-Caltech/T. Pyle

A team of astronomers suggests that an exoplanet named 62f could be habitable. Kepler data suggests that 62f is likely a rocky planet, and could have oceans. The exoplanet is 40% larger than Earth and is 1200 light years away.

62f is part of a planetary system discovered by the Kepler mission in 2013. There are 5 planets in the system, and they orbit a star that is both cooler and smaller than our Sun. The target of this study, 62f, is the outermost of the planets in the system.

Kepler can’t tell us if a planet is habitable or not. It can only tell us something about its potential habitability. The team, led by Aomawa Shields from the UCLS department of physics and astronomy, used different modeling methods to determine if 62f could be habitable, and the answer is, maybe.

According to the study, much of 62f’s potential habitability revolves around the CO2 component of its atmosphere, if it indeed has an atmosphere. As a greenhouse gas, CO2 can have a significant effect on the temperature of a planet, and hence, a significant effect on its habitability.

Earth’s atmosphere is only 0.04% carbon dioxide (and rising.) 62f would likely need to have much more CO2 than that if it were to support life. It would also require other atmospheric characteristics, .

The study modelled parameters for CO2 concentration, atmospheric density, and orbital characteristics. They simulated:

  • An atmospheric thickness from the same as Earth’s up to 12 times thicker.
  • Carbon dioxide concentrations ranging from the same as Earth’s up to 2500 times Earth’s level.
  • Multiple different orbital configurations.

It may look like the study casts its net pretty wide in order to declare a planet potentially habitable. But the simulations were pretty robust, and relied on more than a single, established modelling method to produce these results. With that in mind, the team found that there are multiple scenarios that could make 62f habitable.

“We found there are multiple atmospheric compositions that allow it to be warm enough to have surface liquid water,” said Shields, a University of California President’s Postdoctoral Program Fellow. “This makes it a strong candidate for a habitable planet.”

As mentioned earlier, CO2 concentration is a big part of it. According to Shields, the planet would need an atmospheric entirely composed of CO2, and an atmosphere five times as dense as Earth’s to be habitable through its entire year. That means that there would be 2500 times more carbon dioxide than Earth has. This would work because the planet’s orbit may take it far enough away from the star for water to freeze, but an atmosphere this dense and this high in CO2 would keep the planet warm.

But there are other conditions that would make 62f habitable, and these include the planet’s orbital characteristics.

“But if it doesn’t have a mechanism to generate lots of carbon dioxide in its atmosphere to keep temperatures warm, and all it had was an Earth-like amount of carbon dioxide, certain orbital configurations could allow Kepler-62f’s surface temperatures to temporarily get above freezing during a portion of its year,” said Shields. “And this might help melt ice sheets formed at other times in the planet’s orbit.”

Shields and her team used multiple modelling methods to produce these results. The climate was modelled using the Community Climate System Model and the Laboratoire de Me´te´orologie Dynamique Generic model. The planet’s orbital characteristics were modelled using HNBody. This study represents the first time that these modelling methods were combined, and this combined method can be used on other planets.

Shields said, “This will help us understand how likely certain planets are to be habitable over a wide range of factors, for which we don’t yet have data from telescopes. And it will allow us to generate a prioritized list of targets to follow up on more closely with the next generation of telescopes that can look for the atmospheric fingerprints of life on another world.”

There are over 2300 confirmed exoplanets, and many more candidates yet to be confirmed. Only a handful of them have been confirmed as being in the habitable zone around their host star. Of course, we don’t know if life can exist on other planets, even if they do reproduce the same kind of habitability that Earth has. We just have no way of knowing, yet.

That will change when instruments like the James Webb Space Telescope are able to peer into the atmospheres of exoplanets and tell us something about any bio-markers that might be present.

But until then, and until we actually visit another world with a probe of some design, we need to use modelling like the type employed in this study, to get us closer to answering the question of life on other worlds.

The post Life On Kepler-62f? appeared first on Universe Today.

Starshade Prepares To Image New Earths

Artist's concept of the prototype starshade, a giant structure designed to block the glare of stars so that future space telescopes can take pictures of planets. Credit: NASA/JPL

For countless generations, people have looked up at the stars and wondered if life exists somewhere out there, perhaps on planets much like ours. But it has only been in recent decades that we have been able to confirm the existence of extrasolar planets (aka. exoplanets) in other star systems. In fact, between 1988 and April 20th of 2016, astronomers have been able to account for the existence of 2108 planets in 1350 different star systems, including 511 multiple planetary systems.

Most of these discoveries have taken place within just the past three years, thanks to improvements in our detection methods, and the deployment of the Kepler space observatory in 2009. Looking ahead, astronomers hope to improve on these methods even further with the introduction of the Starshade, a giant space structure designed to block the glare of stars, thus making it easier to find planets – and perhaps another Earth!

While some planets have been observed directly with telescopes (a process known as “Direct Imaging”), the vast majority have been detected through indirect methods such as the Transit Method. This method attempts to spot planets as they cross in front of the parent star’s disk – during which time there will be a temporary drop in observed brightness – and can also reveal the radius of a planet and sometimes yield information on its atmosphere (with the help of spectrometers).

https://youtu.be/ALGI0ex0-ac?list=PLTiv_XWHnOZp2Wmmd3gVSiKAVyXk9Rh14

This method remains the most widely-used means of detection and is responsible for more exoplanet discoveries than all other methods combined. However, due to interference from other light sources, it also suffers from a substantial rate of false positives, and generally requires that part of the planet’s orbit intersect a line-of-sight between the host star and Earth.

To address this, NASA is developing some key technologies that will help block out light interference so that future astronomers can detect exoplanets more easily. For instruments here on Earth, they are developing chronographs, single instruments that fit inside telescopes to block light. But looking to space, NASA’s Jet Propulsion Laboratory is also developing the Starshade.

This concept calls for a giant, flower-shaped spacecraft that would be launched with one of NASA’s next-generation space telescopes. Once deployed, it would fly around in front of the telescope in order to obscure the light of distant stars. This way, the light being reflected off of planets in orbit around them will be detectable, thus making it that much easier to confirm the presence of exoplanets.

The project is led by Prof. Jeremy Kasdin of Princeton University, in conjunction with the JPL and support from Northrop Grumman (which leads the mission and system design for Starshade). As Kasdin explained to Universe Today via email:

“The starshade works just like your thumb when trying to block the Sun; it blocks the starlight from entering the telescope but allows light from he planet close by to pass unimpeded.  Since planets are so much dimmer than their host stars, this technology eliminates the problem of glare from the star swamping light from the planet.  And because the starlight never enters the telescope, any conventional telescope can be used; no special attention needs to be paid to stabilities and precision in the telescope.”

https://youtu.be/Hn0VtQ3FqCw

The shade, which is about the  size of a baseball diamond, would be deployed as part a single mission. As the video above shows, the large shade would be mounted at the end of a space telescope – in this case, NASA’s upcoming Wide Field Infrared Survey Telescope (WFIRST) – and then detaches and deploys to a distance of several thousands kilometers in front of it.

Such a large shade operating at such a long distance from of its paired telescope is essential when dealing with distant stars.”Because stars are so far away the angular distance between the planet and star is quite small,” said Kasdin, “requiring a very large starshade (20 to 50 meters in diameter) flying very far from the telescope (up to 50,000 km). Nevertheless, many astronomers believe this is the best technology to detect an Earthlike planet in the near future, a belief aided by the fact that few special requirements are placed on the telescope.”

Paired with other instruments, like spectrometers, devices like the Starshade will not only allow astronomers to be able to spot planets more easily, but also obtain information about their atmospheres. By studying their chemical compositions – i.e. looking for the presence of oxygen/nitrogen, water vapor, etc. – we would be able to tell with a fair degree of certainty whether or not life exists on them.

The Starshade technology is one of the top candidates for a flagship-level mission in the next decade and a top Astro2010 priority for technology development. In addition to working with WFIRST, it is possible it will be paired with missions like the Transiting Exoplanet Survey Satellite (TESS) and the James Webb Space Telescope.

“We are hoping that a starshade capable of Earth detection will be recommended to fly with the upcoming WFIRST mission,” Kasdin added, “allowing the first image of an Earth in the next decade.”

 

Further Reading: JPL News

The post Starshade Prepares To Image New Earths appeared first on Universe Today.

Starshade Prepares To Image New Earths

Artist's concept of the prototype starshade, a giant structure designed to block the glare of stars so that future space telescopes can take pictures of planets. Credit: NASA/JPL

For countless generations, people have looked up at the stars and wondered if life exists somewhere out there, perhaps on planets much like ours. But it has only been in recent decades that we have been able to confirm the existence of extrasolar planets (aka. exoplanets) in other star systems. In fact, between 1988 and April 20th of 2016, astronomers have been able to account for the existence of 2108 planets in 1350 different star systems, including 511 multiple planetary systems.

Most of these discoveries have taken place within just the past three years, thanks to improvements in our detection methods, and the deployment of the Kepler space observatory in 2009. Looking ahead, astronomers hope to improve on these methods even further with the introduction of the Starshade, a giant space structure designed to block the glare of stars, thus making it easier to find planets – and perhaps another Earth!

While some planets have been observed directly with telescopes (a process known as “Direct Imaging”), the vast majority have been detected through indirect methods such as the Transit Method. This method attempts to spot planets as they cross in front of the parent star’s disk – during which time there will be a temporary drop in observed brightness – and can also reveal the radius of a planet and sometimes yield information on its atmosphere (with the help of spectrometers).

https://youtu.be/ALGI0ex0-ac?list=PLTiv_XWHnOZp2Wmmd3gVSiKAVyXk9Rh14

This method remains the most widely-used means of detection and is responsible for more exoplanet discoveries than all other methods combined. However, due to interference from other light sources, it also suffers from a substantial rate of false positives, and generally requires that part of the planet’s orbit intersect a line-of-sight between the host star and Earth.

To address this, NASA is developing some key technologies that will help block out light interference so that future astronomers can detect exoplanets more easily. For instruments here on Earth, they are developing chronographs, single instruments that fit inside telescopes to block light. But looking to space, NASA’s Jet Propulsion Laboratory is also developing the Starshade.

This concept calls for a giant, flower-shaped spacecraft that would be launched with one of NASA’s next-generation space telescopes. Once deployed, it would fly around in front of the telescope in order to obscure the light of distant stars. This way, the light being reflected off of planets in orbit around them will be detectable, thus making it that much easier to confirm the presence of exoplanets.

The project is led by Prof. Jeremy Kasdin of Princeton University, in conjunction with the JPL and support from Northrop Grumman (which leads the mission and system design for Starshade). As Kasdin explained to Universe Today via email:

“The starshade works just like your thumb when trying to block the Sun; it blocks the starlight from entering the telescope but allows light from he planet close by to pass unimpeded.  Since planets are so much dimmer than their host stars, this technology eliminates the problem of glare from the star swamping light from the planet.  And because the starlight never enters the telescope, any conventional telescope can be used; no special attention needs to be paid to stabilities and precision in the telescope.”

https://youtu.be/Hn0VtQ3FqCw

The shade, which is about the  size of a baseball diamond, would be deployed as part a single mission. As the video above shows, the large shade would be mounted at the end of a space telescope – in this case, NASA’s upcoming Wide Field Infrared Survey Telescope (WFIRST) – and then detaches and deploys to a distance of several thousands kilometers in front of it.

Such a large shade operating at such a long distance from of its paired telescope is essential when dealing with distant stars.”Because stars are so far away the angular distance between the planet and star is quite small,” said Kasdin, “requiring a very large starshade (20 to 50 meters in diameter) flying very far from the telescope (up to 50,000 km). Nevertheless, many astronomers believe this is the best technology to detect an Earthlike planet in the near future, a belief aided by the fact that few special requirements are placed on the telescope.”

Paired with other instruments, like spectrometers, devices like the Starshade will not only allow astronomers to be able to spot planets more easily, but also obtain information about their atmospheres. By studying their chemical compositions – i.e. looking for the presence of oxygen/nitrogen, water vapor, etc. – we would be able to tell with a fair degree of certainty whether or not life exists on them.

The Starshade technology is one of the top candidates for a flagship-level mission in the next decade and a top Astro2010 priority for technology development. In addition to working with WFIRST, it is possible it will be paired with missions like the Transiting Exoplanet Survey Satellite (TESS) and the James Webb Space Telescope.

“We are hoping that a starshade capable of Earth detection will be recommended to fly with the upcoming WFIRST mission,” Kasdin added, “allowing the first image of an Earth in the next decade.”

 

Further Reading: JPL News

The post Starshade Prepares To Image New Earths appeared first on Universe Today.

First Exoplanet Discovered Beyond the “Snow Line”

Data from NASA’s crippled Kepler space telescope has unleashed a windfall of hot Jupiters — sizzling gas giants that circle their host star within days — and only a handful of Earth-like planets. A quick analysis might make it seem as though hot Jupiters are far more common than their smaller and more distant counterparts. […]