Tag Archives: habitable planet

How TRAPPIST-1 could unveil its secrets to James Webb Telescope

Set to launch in 2021, the James Webb Space Telescope could be able to learn key facts about TRAPPIST-1 planetary system even in its first year of operation, according to a new study.

The James Webb Space Telescope is set to be launched in 2021. Credit: NASA

The research by Jacob Lustig-Yaeger, a doctoral study in astronomy, used TRAPPIST-1 as a kind of laboratory to model not the planets themselves, but how the coming telescope might detect and study their atmospheres.

“The Webb telescope has been built, and we have an idea how it will operate,” said Lustig-Yaeger. “We used computer modeling to determine the most efficient way to use the telescope to answer the most basic question we’ll want to ask, which is: Are there even atmospheres on these planets, or not?.”

Astronomers have had their eye on TRAPPIST-1 for a while now because of its seven-orbiting rocky, Earth-like, planets. Three of these worlds are in the star’s habitable zone—that swath of space around a star that is just right to allow liquid water on the surface of a rocky planet, thus giving life a chance.

The star, TRAPPIST-1, was much hotter when it formed than it is now, which would have subjected all seven planets to the ocean, ice and atmospheric loss in the past.

“There is a big question in the field right now whether these planets even have atmospheres, especially the innermost planets,” Lustig-Yaeger said. “Once we have confirmed that there are atmospheres, then what can we learn about each planet’s atmosphere—the molecules that make it up?”

The paper, published in the Astronomical Journal, said that the James Webb Space Telescope could learn quite a lot in a short period of time, given the way it might do its search.

Exoplanets are detected by astronomers when they pass in front of or “transit” their host star, resulting in a measurable dimming of starlight. Planets closer to their star transit more frequently and so are somewhat easier to study. When a planet transits its star, a bit of the star’s light passes through the planet’s atmosphere, with which astronomers can learn about the molecular composition of the atmosphere.

Astronomers can see tiny differences in the planet’s size when they look in different colors, or wavelengths, of light, Lustig-Yaeger said.

“This happens because the gases in the planet’s atmosphere absorb light only in very specific colors. Since each gas has a unique ‘spectral fingerprint,’ we can identify them and begin to piece together the composition of the exoplanet’s atmosphere,” he added.

The team’s modeling indicates that the James Webb telescope, using a versatile onboard tool called the Near-Infrared Spectrograph, could detect the atmospheres of all seven TRAPPIST-1 planets in 10 or fewer transits—if they have cloud-free atmospheres, Lustig-Yaeger said.

NASA Scientists find 20 potentially habitable planets

Trick or treat? NASA’s Halloween gift really is something everyone should be excited of. Astronomers have discovered a trove of 20 planets, some of which seem very Earth-like.

The latest catalog represents Kepler’s final survey from the Cygnus constellation and spans the spacecraft’s first four years of data. The Kepler spacecraft has detected 219 new exoplanet candidates – and ten could be habitable. Image credits: NASA.

The findings were made by the Kepler telescope and feature several planets orbiting stars much like our Sun. Their orbits vary between 18 and 395 Earth days, with the 395-day planet being one of the most promising candidates. It’s 97 percent the size of Earth, but a bit farther from its star, meaning it’s almost certainly colder. This would translate into more Arctic or tundra-like areas, but all things being equal, it would still be able to hold liquid water — the main prerequisite for life as we know it.

All planets are between 20 and 50 percent larger than Earth by diameter, and all of them orbit the M dwarf star K2-72 some 181 light years away. K2-72 is an M-type star that is approximately 27% the mass of and 33% the radius of the Sun. Its name comes from being the 72nd star discovered by the K2 (2nd Kepler) mission.

Kepler employs the transit method, which involves detecting dips in brightness in stars (as one planet passes between its star and the telescope, there’s a dip in luminosity). These dips in brightness can be interpreted as planets whose orbits move in front of their stars from the perspective of Earth.

Scientists are “between 70 and 80 percent” certain that these are solid Earth-like candidates. The main cause of uncertainty is the long orbit time of these planets. All the data comes from the original Kepler mission, which means that we’ve only seen these planets once or twice, and the signal could be a bit wobbly. Having more data points from other observatories could allow researchers to confirm these planets. Even if they turn out to be fake, such errors allow researchers to calibrate their data for future measurements.

I believe that this is a much improved catalogue so I’m eager to explore it further,” says Abel Mendez, director of the Planetary Habitability Lab at Arecibo Observatory.

So far, the Kepler telescope has done an amazing job. Kepler is a space observatory launched by NASA to discover Earth-size planets orbiting other stars in 2009. The NASA mission has discovered over 4,000 potential planet candidates, some 2,300 of which have been already confirmed by other observations. Out of these, 21 are Earth-sized and in the so-called habitable zone. Data from the Kepler telescope is publicly available, open for anyone to access. As researchers comb through it more and more, we can almost certainly expect more exciting findings.

Journal Reference: Susan E. Thompson et al. Planetary Candidates Observed by Kepler. VIII. A Fully Automated Catalog With Measured Completeness and Reliability Based on Data Release 25. 

Earth-sized planets all have relatively circular orbits, study finds

For decades, researchers have studied our planet’s orbit with growing interest: is there something special about the way the Earth revolves around the Sun, is it a necessary condition for life to emerge? A team of researchers from MIT studied 74 Earth-sized exoplanets and reports that all of them have fairly circular orbits around their stars.

Circular vs Eccentric

Image courtesy of NASA.

The study, published in the Astrophysical Journal, reports that the 74 exoplanets revolve their 28 stars at relatively circular trajectory, standing in stark contrast to larger exoplanets, which have much more eccentric orbits.

“Twenty years ago, we only knew about our solar system, and everything was circular and so everyone expected circular orbits everywhere,” says Vincent Van Eylen, a visiting graduate student in MIT’s Department of Physics. “Then we started finding giant exoplanets, and we found suddenly a whole range of eccentricities, so there was an open question about whether this would also hold for smaller planets. We find that for small planets, circular is probably the norm.”

It’s not clear why this happens, or whether this has something to do with with their size, or whether it’s a coincidence. Having a circular orbit is one of the proposed requirements for supporting life; otherwise, the climatic swings between seasons are simply too massive. It’s not impossible for life to exist on planets with eccentric orbits, but it just seems much more unlikely.

“If eccentric orbits are common for habitable planets, that would be quite a worry for life, because they would have such a large range of climate properties,” Van Eylen says. “But what we find is, probably we don’t have to worry too much because circular cases are fairly common.”

All in all, the study brings good news for detecting life outside our solar system.

Detecting Planets

Artistic representation of the Kepler Telescope. Image via Wikipedia.

Artistic representation of the Kepler Telescope. Image via Wikipedia.

Most earth-sized planets are detected with the transit method – astronomers study the light given off by a star and record eventual dips in starlight when a planet transits in front of that star. To obtain actual transit data, the team looked through data collected over the past four years by NASA’s Kepler telescope. Kepler is a space observatory launched by NASA to discover Earth-like planets orbiting other stars. The telescope monitored the brightness of over 145,000 stars, only a fraction of which have been studied in detail. For this study, they focused on 28 stars orbited by 74 earth-like planets.

Their results came out pretty surprising: all the planets run (approximately) circular orbits around their stars.

“We found that most of them matched pretty closely, which means they’re pretty close to being circular,” Van Eylen says. “We are very certain that if very high eccentricities were common, we would’ve seen that, which we don’t.”

However, David Kipping, an astronomer at the Harvard-Smithsonian Center for Astrophysics, notes that while interesting, a 74 planets sample size is not large enough to draw some definite conclusions.

“I think that the evidence for smaller planets having more circular orbits is presently tentative,” says Kipping, who was not involved in the research. “It prompts us to investigate this question in more detail and see whether this is indeed a universal trend, or a feature of the small sample considered.”

The logical thing to do next is study more planets and see if these initial results stand up. Kepler has a huge database, and much of that data hasn’t been studied to begin with. Just decades ago we didn’t know any exoplanets, and now we’re studying the orbits of exoplanets and we want a greater sample size – it’s a great time to be alive.

 

 

 

 

New Study Suddenly Makes Billions of Exoplanets Habitable

Astronomers hunting for habitable Earth-like planets now believe that the best place to look is not around stars like our Sun, but rather around smaller, cooler stars—orange and red dwarfs. These are by far the most abundant stars in our galaxy, and all of them have at least one exoplanet.

Artist representation of a red dwarf surrounded by 3 planets. Image via Wiki Commons.

Red Dwarfs are smaller and cooler than our Sun, ranging from a mass of of 0.075 solar masses to about 0.50 solar masses. Red dwarfs are by far the most common stars in the Milky Way galaxy and in the entire Universe, but due to their low luminosity they are pretty hard to observe. It’s estimated that some 75 percent of all stars in the universe are red dwarfs, and all of them host planets.

The habitability of red dwarfs has been discussed many times, and is still a matter of debate. Of course, knowing if the most common stars in the universe can host habitable planets is a big deal. Among the problems raised against habitability is the so called tidal locking: just like our planet sees only one side of the moon at all times, so do the red dwarfs; they only see one side of the planet, which means that one side is likely a desertic landscape, while the other is a frozen nightmare.

Above: How heat is distributed on a spinning planet versus a rotationally locked one. Image via Popular Mechanics.

 

This happens when the planet is close to its star, as planets would have to be closer to red dwarfs to be habitable. Naturally, in this case the chances for life are much smaller (though it’s not completely impossible). However, this new study challenges this idea, and claims that not all planets are engaged in tidal locking.

The simple existence of an atmosphere, researchers argue, is enough to ensure that the planet is rotating and revolving around its star, making it much more likely to be habitable. According to Jérémy Leconte, the theoretical astrophysicist at the University of Toronto who lead the study, this means that we may have already discovered many habitable planets – we just don’t know it yet.

“Planets with potential oceans could thus have a climate that is much more similar to the Earth’s than we’ve previously expected,” he says.

So how does the atmosphere play into this problem? Jeff Coughlin, a SETI astronomer working with Kepler planet-hunting mission, who was not involved in the study explains it like this:

“On Earth, light from the sun is what drives the weather in our atmosphere. And that weather, in the form of wind, constantly pushes against the planet—running into mountains, for example, or creating waves on the ocean. This friction is deposited in the rotation rate of our planet, helping to speed it up or slow it down.”

Astrophysicists have known this for quite a while, but according to initial calculations, the atmosphere would have to be incredibly massive to have this impact. We have a good case study very close to us: Venus. Venus’ atmosphere is just big enough to escape lockup, and Venus’ atmosphere is absolutely huge – about 90 times heavier than our own. So scientists discarded the idea.

But when Leconte and his team ran simulations to see how the atmosphere would play into gravitational locking, they surprisingly found that thinner atmospheres actually have a larger rotational effect on their planets. This may seem counterintuitive, but it happens because a thinner atmosphere scatters less sunlight. This creates extra heat which in turn creates a stronger atmospheric tide (a bulging of atmosphere, much like our ocean’s tides). This results in a stronger planetary rotation. If Venus were to have an atmosphere like Earth’s, it would spin 10 times faster.

Armed with the results of this model, the team showed that Earth-sized planets can spin quite healthily around a red dwarf if they have an atmosphere.

“More and more, we’re discovering that there’s a lot of ways to have a very nice, habitable planet around dwarf stars,” Coughlin says. But there’s something more at play here. “We really shouldn’t be so narrow-minded in our assumptions about what types of planets could or could not be habitable,” he says. Coughlin says that even a locked-up rotation is not necessarily a killer for a planet in terms of habitability—strong winds could help smooth out the temperature between the two sides.

It would be nice if we’d be able to confirm this model with some observed information, but until that, the results of this study are pretty convincing.

“Every time we’ve made simple assumptions about habitability,” he says, “we find out new ways why and how they don’t apply.”

Journal Reference: Jérémy Leconte, Hanbo Wu, Kristen Menou, Norman Murray. Asynchronous rotation of Earth-mass planets in the habitable zone of lower-mass stars. Science DOI: 10.1126/science.1258686

An artist's impression of an Earth-like planet with two moons orbiting around a red dwarf star. (c) David A. Aguilar (CfA).

Earth-like planets closer than previously thought. Nearest one might lie 13 light-years away

After researchers surveyed data from the Kepler mission tasked with identifying possibly habitable planets outside our solar system they found that 6% of red dwarfs – the most common type of planets – are within this zone. This new adjustment would mean that the nearest Earth-like planet might lie just 13 light years away.

An artist's impression of an Earth-like planet with two moons orbiting around a red dwarf star. (c) David A. Aguilar (CfA).

An artist’s impression of an Earth-like planet with two moons orbiting around a red dwarf star. (c) David A. Aguilar (CfA).

Astronomers at the Harvard-Smithsonian Center for Astrophysics (CfA) first took a look at the entire Kepler catalog of 158,000 target stars to identify all the red dwarfs. Then a more refined method was used to assess the stars’ temperature and size, an analysis that showed that these were generally smaller and cooler than previously thought.

An exoplanet is discovered and has its properties determined based on its transient orbit in plane with its parent star. This implies that the exoplanet’s size and properties are the same time determined based on its host star, since they’re based relative to the star’s properties. Thus, cooler dwarf stars means cooler planets and a tighter habitable zone.

“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).

A new Earth might be closer to us than thought

Red dwarfs make up three out of every four stars in our galaxy for a total of at least 75 billion. The astronomers involved in the present study identified 95 planetary candidates orbiting such red dwarf stars. Upon closer inspection most of them didn’t fit the right size and temperature requirements needed for them to be considered Earth-like, though. Three candidate planets, however, were considered both warm and Earth-sized. This would statistically imply that some 6% of all red dwarfs should have an Earth-like planet orbiting.

“We now know the rate of occurrence of habitable planets around the most common stars in our galaxy,” said co-author David Charbonneau (CfA). “That rate implies that it will be significantly easier to search for life beyond the solar system than we previously thought.”

It so has it that our solar system is located in a cloud of red dwarfs, which is why more than 75% of all neighboring stars are red dwarfs. With this new analysis in play, this all adds up implying that the nearest Earth-like planet might lie just 13 light years away.

Actually locating an Earth-like planet, with all its perks, would require an analysis of its atmosphere, something not possible with today’s technology. Once with the deployment of massive space telescopes like the James Webb Space Telescope or ground based telescope arrays like the Giant Magellan Telescope probing a distant world’s chemistry will be possible – expect some of humanity’s greatest discoveries to be made once this happens.

The three habitable-zone planetary candidates identified in this study are Kepler Object of Interest (KOI) 1422.02, which is 90 percent the size of Earth in a 20-day orbit; KOI 2626.01, 1.4 times the size of Earth in a 38-day orbit; and KOI 854.01, 1.7 times the size of Earth in a 56-day orbit. All three are located about 300 to 600 light-years away and orbit stars with temperatures between 5,700 and 5,900 degrees Fahrenheit. (For comparison, our Sun’s surface is 10,000 degrees F.)

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

source: press release

New ‘Habitable Zone’ for alien planets redefined

As our search for alien planets improves and intensifies, astronomers are starting to pay more and more attention to one crucial aspect of alien planets:  whether they fit into the ‘habitable zone‘ – the so-called Goldilocks area in which a planet is not too close and not too far from its star – just perfectly placed to support liquid life, which is the basis of life as we know it.

The old definition of the habitable zone. According to the new one, Mars falls just inside it - highlighting the difference between astronomic and geologic habitability.

The old definition of the habitable zone. According to the new one, Mars falls just inside it – highlighting the difference between astronomic and geologic habitability.

Of course non-carbon based life could exist in a solvent different to water, but so far, astronomers are focusing on whatever signals they can detect. Now, they have redefined the borders for this area, potentially kicking out some exoplanaets that were thought to fall within it, but on the other hand, maybe adding some new ones.

“This will have a significant impact on the number of exoplanets that are within habitable zone,” said research team leader Ravi Kumar Kopparapu of Penn State University.

The new definition of the habitable zone takes into consideration updated atmospheric databases – HITRAN (high-resolution transmission molecular absorption) and HITEMP (high-temperature spectroscopic absorption parameters), which give the absorbtion parameters of both water and carbon dioxide, two properties important for the planets’ atmosphere, significantly influencing their capability to host water.

However, scientists warn, this still doesn’t take into consideration feedback effects from clouds, which will also affect a planet’s habitability. Also, there is a difference between what habitable means from an astronomic point of view, and from a geologic point of view.

The previous definition of the habitable zone was derived about 20 years ago by Penn State researcher James Kasting, who also worked to conduct these updates.

“At the time when he wrote that paper no exoplanets were discovered,” Kopparapu explained. “In 20 years, hundreds, maybe thousands have been discovered.” – which makes his initial work all the more admirable, but it also means changes are necessary.

The new changes aren’t dramatic; considering an Astronomical Unit (AU) as the distance between the Earth and the Sun, the limits for the habitable zone have been changed from between 0.95 and 1.67 AU to 0.99 AU to 1.7 AU. Even so, this slight change will probably have significant consequences.

“It’s a surprise that Earth is so close to the inner edge of the habitable zone,” said astronomer Abel Méndez of the University of Puerto Rico at Arecibo, who was not part of the team behind the redefinition.

He mentioned one planet in particular, Gliese 581d, was thought to lie at the outer edge of its star’s habitable zone – with the new definition, Gliese 581d falls exactly in the middle, making it an even better candidate.

“That will be a big change for that particular planet,” Méndez said. “That means the prospects for life on the planet will be much better.”

The changes will be published in the future edition of the Astrophysical Journal.

You can browse the catalog of Habitable Planets directly here.

Habitable planet in Tau Ceti system

Another Earth could be just 12 light years away

Astronomers have discovered five planets orbiting Tau Ceti, the closest single star that resembles our Sun in terms of temperature and luminosity.

Finding our cosmic neighbors

Habitable planet in Tau Ceti system

An artist’s depiction of a planet in the Tau Ceti system.

If the planets are indeed there and no error was involved in the study, then there’s a good chance one of them is the right distance from the star to sport adequate temperatures, liquid oceans – and even life. But don’t pack your bags just yet – there is still some skepticism surrounding the find.

Tau Ceti has about 78% of the Sun’s mass, and it is “just” 3 times as far as our closest neighbor – Alpha Centauri; however, unlike Alpha Centauri, who also has a G-type star and even a planet that could host life, Tau Ceti is single – there is no other star that could yank planets away.

Earth, water and fire

All of the five planets are closer than to Tau Ceti than the Earth is to the Sun, but that’s actually a good thing – since the star only emits 45% as much light and warmth as the sun, the planets have to be significantly closer to harbor life. The five candidates for life are relatively small, but still bigger than the Earth – with masses ranging from 2 to 6.6 times that of Earth.

The Earth is a rocky planet – also known as terrestrial or telluric planet; the best candidate for life in the system of Tau Ceti, which completes one lap around its star in 168 days, however, is unlikely to be a rocky planet.

“It is impossible to tell the composition, but I do not consider this particular planet to be very likely to have a rocky surface,” lead author Mikko Tuomi, of the University of Hertfordshire in England, explained. “It might be a ‘water world,’ but at the moment it’s anybody’s guess.”

An ocean planet (also termed a waterworld) is a type of planet whose surface is completely covered with an ocean of water – but don’t despair: life is at least just as likely to appear on those worlds. However, researchers are still awaiting the confirmation for the results.

Via Space.com

Earth-sized lava world found in Alpha Centaury – closest find yet

The search for other planets gets more and more exciting and fruitful, and now, researchers have found an exoplanet which lies truly close to us – in cosmic terms.

Alpha Centauri

Alpha Centauri is the closest solar system to our own, at only 4 light years away, so finding an Earth-sized planet there really is a big thing, and it shows that the myriad of writers inspired weren’t really far away from the truth. However, don’t get any hopes up – the planet is closer to its star than Mercury is to the Sun, so it’s basically just a scorched and barren rock. To make things even worse, despite of its astronomic proximity to Earth which sparks dreams of interstellar travel, we are nowhere near able to travel to it at the moment.

Alpha Centauri seems to be a single star to the unaided eye, but it is actually a binary system, with Alpha Centauri A and B – both comparable in terms of size with our Sun; the newfound planet orbits Alpha Centauri B.

Finding planets

The planet, which is the closest we’re ever going to find, was observed using a technique that monitors a star for a subtle back-and-forth ‘wobble’ in its motion as seen from Earth, caused by a gravitational effect. Neither the star nor the planet are unusual in any way, aside for their proximity to Earth. However, even though it isn’t habitable according to what we know now, an Earth twin could also be hiding in the area, says Ralph McNutt, a planetary scientist at Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland.

Geoff Marcy, an astronomer at the University of California, Berkeley, who leads another ground-based search effort, says that the discovery should bolster calls for a space-based tele­scope that could image any other planets near α Centauri B, if they have large enough orbits.

Source
The study was published in Nature

First rocky habitable Earth-like planet

A recently discovered planet is just about the right size and is in the right place to host life; as a matter of fact, astronomers seem quite sure it hosts life, and we’re talking more than microbes. Still, current technology doesn’t allow scientists to search for chemical markers of life.

About 20 light years away, it revolves around a red dwarf, and has been nicknamed Gliese 581g – the “g” stands for Goldilocks.

“Personally, given the ubiquity and propensity of life to flourish wherever it can, I would say that the chances for life on this planet are 100 percent. I have almost no doubt about it,” Steven Vogt, professor of astronomy and astrophysics at University of California Santa Cruz, told Discovery News.

The discovery comes as a result of an 11 year program to get as much information as possible with ground-based instruments and telescopes; these instruments work by measuring minute variations caused by gravitational tugs of orbiting planets.

Red Dwarf

“This is really the first ‘Goldilocks’ planet, the first planet that is roughly the right size and just at the right distance to have liquid water on the surface,” astronomer Paul Butler, with the Carnegie Institution in Washington, D.C., told reporters during a conference call Wednesday.

“Everything we know about life is that it absolutely requires liquid water,” he added. “The planet has to be the right distance from the star so it’s not too hot, not too cold… and then it has to have surface gravity so that it can hold on to a substantial atmosphere and allow the water to pool.”

The planet is roughly three times larger than Earth, so it’s big enough to hold an atmosphere. It’s also quite old, and even more interesting, it’s tidally locked to the Sun, in a similar fashion to the Moon locked to the Earth: the planet’s star always ‘sees’ the same side, which is perpetually warmer and lighted, while the other one is dark and cold. As a result, temperatures are pretty stable, and vary greatly, which also encourages life.

“This planet doesn’t have days and nights. Wherever you are on this planet, the sun is in the same position all the time. You have very stable zones where the ecosystem stays the same temperature… basically forever,” Vogt said. “If life can evolve, it’s going to have billions and billions of years to adapt to the surface.”

“Given the ubiquity of water, it seems probable that this thing actually has liquid water. On the surface of the Earth, everywhere you have liquid water you have life,” Vogt added.

Astronomers seem quite convinced that many more such planets will be discovered in the not so distant future, and we will be entering a new stage in studying Earth-like planets.

“That being said, it is so close and we have found this thing so soon that it suggests we will start finding a lot of these things in the future and eventually we will find systems that do transit. This is a harbinger of things to come.”

The research will be published in the Astrophysical Journal

Easier (but still not easy) way to other habitable planets

 

planet

The hunt is on for finding other planets we can live on; this is probably the next step for us as a species, and may just be crucial, considering how things are developing on Earth. But we haven’t had much luck with that so far. Now, scientists are using a method which is claimed to be more precise in calibrating the measurement of spectra should make it possible to identify Earth-sized planets around stars outside our Solar System.

For that, they used ground telescopes. The technique which involves these telescopes practically make laser “combs”, which are fine-toothed spectra of light that used along with atomic clocks give scientists a pretty good idea about the reference point for measuring the wavelengths of light.

According to Nature, this method will be 60 times more effectiv than the state of the art method used now. Extending this technique’s sensitivity will improve astronomers’ picture of what other stellar systems look like.

Velocity measurements are not the only way to detect planets; there is also another way to find them, perhaps as good as this one. They can be seen by detecting the changes they induce in the stars’ position in the sky. Whatever the method, finding another habitable planet is definetly something of crucial importance.