Extrasolar Planets Archives

October 26, 2012December 23, 2015 by Nancy Atkinson

On Again, Off Again Exoplanet Fomalhaut b is Back from the Dead

This visible-light image from the Hubble Space Telescope shows the vicinity of the star Fomalhaut, including the location of its dust ring and disputed planet, Fomalhaut b. A coronagraphic mask helped dim the star’s brightness. This view combines two 2006 observations that were taken with masks of different sizes (1.8 and 3 arcseconds). (Credit: NASA/ESA/T. Currie, U. Toronto)

Just in time for Halloween, astronomers are bringing an extrasolar planet back from the dead. Another look at the nearby star Fomalhaut reveals that a planet, named Fomalhaut b, is actually, really there, refuting a previous claim against its existence. In 2008, it was announced that a large, Saturn mass planet shepherded a large dust ring and was spotted in visual images from Hubble, and was said to be the first exoplanet ever directly imaged in visible light around another star. But in late 2011 infrared observations called the previous detections into question. A new analysis of data from Hubble, however, brings the planet conclusion back to life.

It’s like a zombie planet that just won’t die.

Fomalhaut is the brightest star in the constellation Piscis Austrinus and lies 25 light-years away.Originally, Fomalhaut b was estimated to be approximately the size of Saturn, and might even have rings. It resides within a debris ring which encircles the star Fomalhaut, located about 25 light-years away from Earth.

Then, later studies claimed that this planetary interpretation is incorrect. Based on the object’s apparent motion and the lack of an infrared detection by NASA’s Spitzer Space Telescope, they argued that the object is a short-lived dust cloud unrelated to any planet.

But still another observation brings this planet back.

“Although our results seriously challenge the original discovery paper, they do so in a way that actually makes the object’s interpretation much cleaner and leaves intact the core conclusion, that Fomalhaut b is indeed a massive planet,” said Thayne Currie, an astronomer formerly at NASA’s Goddard Space Flight Center in Greenbelt, Md., and now at the University of Toronto.

The discovery study reported that Fomalhaut b’s brightness varied by about a factor of two and cited this as evidence that the planet was accreting gas. Follow-up studies then interpreted this variability as evidence that the object actually was a transient dust cloud instead.

In the new study, Currie and his team reanalyzed Hubble observations of the star from 2004 and 2006. They easily recovered the planet in observations taken at visible wavelengths near 600 and 800 nanometers, and made a new detection in violet light near 400 nanometers. In contrast to the earlier research, the team found that the planet remained at constant brightness.

The team attempted to detect Fomalhaut b in the infrared using the Subaru Telescope in Hawaii, but was unable to do so. The non-detections with Subaru and Spitzer imply that Fomalhaut b must have less than twice the mass of Jupiter.

Another contentious issue has been the object’s orbit. If Fomalhaut b is responsible for the ring’s offset and sharp interior edge, then it must follow an orbit aligned with the ring and must now be moving at its slowest speed. The speed implied by the original study appeared to be too fast. Additionally, some researchers argued that Fomalhaut b follows a tilted orbit that passes through the ring plane.

Using the Hubble data, Currie’s team established that Fomalhaut b is moving with a speed and direction consistent with the original idea that the planet’s gravity is modifying the ring.

“What we’ve seen from our analysis is that the object’s minimum distance from the disk has hardly changed at all in two years, which is a good sign that it’s in a nice ring-sculpting orbit,” explained Timothy Rodigas, a graduate student in the University of Arizona and a member of the team.

Currie’s team also addressed studies that interpret Fomalhaut b as a compact dust cloud not gravitationally bound to a planet. Near Fomalhaut’s ring, orbital dynamics would spread out or completely dissipate such a cloud in as little as 60,000 years. The dust grains experience additional forces, which operate on much faster timescales, as they interact with the star’s light.

“Given what we know about the behavior of dust and the environment where the planet is located, we think that we’re seeing a planetary object that is completely embedded in dust rather than a free-floating dust cloud,” said team member John Debes, an astronomer at the Space Telescope Science Institute in Baltimore, Md.

A paper describing the findings has been accepted for publication in The Astrophysical Journal Letters.

And as we reported in April, another team using the Atacama Large Millimeter/sub-millimeter Array (ALMA) indicated they found evidence of Fomalhaut b, and maybe even more planets in the system, giving more credence to the planet’s exitence.

Because astronomers detect Fomalhaut b by the light of surrounding dust and not by light or heat emitted by its atmosphere, it no longer ranks as a “directly imaged exoplanet.” But because it’s the right mass and in the right place to sculpt the ring, Currie’s team thinks it should be considered a “planet identified from direct imaging.”

Fomalhaut was targeted with Hubble most recently in May by another team. Those observations are currently under scientific analysis and are expected to be published soon.

Read the latest team’s paper.

Source: NASA

October 23, 2012December 23, 2015 by Jenny Winder

Cheops – A Little Satellite with Big Ideas

Caption: Artist impression of Cheops. Credit: University of Bern

Big isn’t always better. This is certainly true at ESA’s new Science Programme. They are looking to low cost, small scale missions that can be rapidly developed, in order to offer greater flexibility in response to new ideas from the scientific community, to complement the broader Medium- and Large-class missions. Back in March ESA called for ideas for dedicated, quick-turnaround missions focusing on key issues in space science. From 26 proposals submitted, ESA has now approved a new mission to be launched in 2017. Though small in scale this mission is big on ambition: to search for nearby habitable planets.

Cheops stands for CHaracterising ExOPlanets Satellite. It has a planned mission lifetime of 3.5 years during which it will operate in a Sun-synchronous low-Earth orbit at an altitude of 800 km, free from distortion by Earth’s atmosphere. It will target nearby, bright stars already known to have planets orbiting around them.

By high-precision monitoring of the star’s brightness, Cheops will search for signs of a ‘transit’ as a planet passes across the star’s face, it will also be able to look for smaller planets, impossible to see using ground based telescopes, around those stars.

While NASA’s Kepler mission has confirmed 77 planets so far, with another 2,321 candidate planets, not one is close enough to Earth to be analysed in detail. Cheops on the other hand, will be able to take accurate measurements of the radius of the planet. For those planets with a known mass, this will reveal the planet’s density and provide an indication of the internal structure. It will help scientists understand the formation of planets from ‘super-Earths’, a few times the mass of the Earth, up to Neptune-sized worlds. It will also identify planets with significant atmospheres which can then be analysed for signs of life by ground-based telescopes, and the next generation of space telescopes now being built, such as the ground-based European Extremely Large Telescope and the NASA/ESA/CSA James Webb Space Telescope.

“By concentrating on specific known exoplanet host stars, Cheops will enable scientists to conduct comparative studies of planets down to the mass of Earth with a precision that simply cannot be achieved from the ground,” said Professor Alvaro Giménez-Cañete, ESA Director of Science and Robotic Exploration.

The plan is for Cheops to be the first of a series of similar small missions, that can be rapidly developed at low cost to investigate new scientific ideas quickly. Cheops will be developed as a partnership between ESA and Switzerland, with a number of other ESA Member States delivering substantial contributions.

Find out more about Cheops here

October 16, 2012December 23, 2015 by Nancy Atkinson

Next Door Neighbors? Earth-Sized Planet Discovered in Nearest Star System to Us

Artist’s impression of the planet around Alpha Centauri B. Credit: ESO

Artist’s impression of the planet around Alpha Centauri B. Credit: ESO

Astronomers have discovered an enticing new planet that could be considered our next-door neighbor. The planet is orbiting a star in the Alpha Centauri system — the closest system to our own, just 4.3 light years away — and the planet has a mass about the same as Earth. It is also the lightest exoplanet ever discovered around a sun-like star. While this planet is likely too hot to contain life as we know it, the star system could possibly host other worlds that could be habitable, researchers from the European Southern Observatory at La Silla say.

“This result represents a major step towards the detection of Earth twins in the immediate vicinity of the Sun,” the team wrote in their paper.

“This is the first planet with a mass similar to Earth ever found around a star like the Sun. Its orbit is very close to its star and it must be much too hot for life as we know it,” said Stéphane Udry from the Geneva Observatory, a co-author of the paper that will be published in Nature on Oct. 17, and member of the team that used the HARPS instrument to find the planet. “But it may well be just one planet in a system of several. Our other HARPS results, and new findings from Kepler, both show clearly that the majority of low-mass planets are found in such systems.”

The planet is called Alpha Centauri Bb and it whips around its star every 3.2 days, orbiting at a distance of just 6 million kilometers (3.6 million miles), closer than Mercury’s orbit around the Sun. (Earth orbits at a comfortable 150 million kilometers (93 million miles) from the Sun.) So it is likely very hot and covered with molten rock, the researchers say.

Many astronomers have thought that the Alpha Centauri system would be a perfect candidate to host Earth-sized worlds. In fact, in 2008, a team of astronomers ran computer simulations of the system’s first 200 million years, and in each instance, despite different parameters, multiple terrestrial planets formed around the star. In every case, at least one planet turned up similar in size to the Earth, and in many cases this planet fell within the star’s habitable zone.

But while astronomers have looked for years, previous searches of planets in the Alpha Centauri system came up empty.

Until now.

“Our observations extended over more than four years using the HARPS instrument and have revealed a tiny, but real, signal from a planet orbiting Alpha Centauri B every 3.2 days,” says Xavier Dumusque (Geneva Observatory, Switzerland and Centro de Astrofisica da Universidade do Porto, Portugal), lead author of the paper. “It’s an extraordinary discovery and it has pushed our technique to the limit!”

The European team detected the planet by using the radial velocity method — by picking up the tiny wobbles in the motion of the star Alpha Centauri B created by the gravitational pull of the orbiting planet. The effect is extremely small, as it causes the star to move back and forth by no more than 51 centimeters per second (1.8 km/hour). The team said this is the highest precision ever achieved using this method.

Alpha Centauri is one of the brightest stars in the southern skies and is actually a triple star — a system consisting of two stars similar to the Sun orbiting close to each other, designated Alpha Centauri A and B, and a more distant and faint red component known as Proxima Centauri.

Alpha Centauri B is very similar to the Sun but slightly smaller and less bright. The orbit of Alpha Centauri A is hundreds of times further away from the planet, but it would still be a very brilliant object in the planet’s skies.

A wide-field view of the sky around Alpha Centauri was created from photographic images forming part of the Digitized Sky Survey 2. The star appears so big just because of the scattering of light by the telescope’s optics as well as in the photographic emulsion. Credit: ESO

The first exoplanet around a Sun-like star was found by the same team back in 1995 and there are now 843 Exoplanets with the addition of Alpha Centauri Bb. Most are much bigger than Earth, and many are as big as Jupiter. The previous closest exoplanet was Epsilon Eridani b, 10.4 light years away.

The challenge astronomers now face is to detect and characterize a planet of mass comparable to the Earth that is orbiting in the habitable zone around another star. The first step has now been taken, the team says.

“This result represents a major step,” said Dumusque. “We live in exciting times!”

So, how long would it take for us to get to this planet? Using current technology, our slowest mode of space transportation, ion drive propulsion, it would take 81,000 years. Using the speeds of one of the fastest spacecraft (Helios 2) and traveling at a constant speed of 240,000 km/hr, it would take about 19,000 years (or over 600 generations) to travel the 4.3 light years.

Read the team’s paper (PDF)

Source: ESO

October 16, 2012December 23, 2015 by Nancy Atkinson

Extreme Solar Systems: Why Aren’t We Finding Other Planetary Systems Like Our Own?

Artist concept of a previous multi-planet solar system found by the Kepler spacecraft. Credit: NASA/Tim Pyle

Most planetary systems found by astronomers so far are quite different than our own. Many have giant planets whizzing around in a compact configuration, very close to their star. An extreme case in point is a newly found solar system that was announced on October 15, 2012 which packs five — count ‘em — five planets into a region less than one-twelve the size of Earth’s orbit!

“This is an extreme example of a compact solar system,” said researcher Darin Ragozzine from the University of Florida, speaking at a press conference at the American Astronomical Society’s Division for Planetary Sciences meeting. “If we can understand this one, hopefully we can understand how these types of systems form and why most known planetary systems appear different from our own solar system.”

This new system, currently named KOI-500, was found with data from the Kepler planet-finding spacecraft, and Ragozzine said astronomers have now uncovered a new realm of exo-planetary systems.

“The real exciting thing is that Kepler has found hundreds of stars with multiple transiting planets,” he said. “These are the most information-rich systems, as they can tell you not only about the planets, but also the architecture of how solar systems are put together.”

The fact that almost all solar systems found so far are vastly different than our own has astronomers wondering if we are, in fact, the oddballs. A study from 2010 concluded that only about 10 – 15 percent of stars in the Universe host systems of planets like our own, with terrestrial planets nearer the star and several gas giant planets in the outer part of the solar system.

Part of the reason our dataset of exoplanets is skewed with planets that are close to the star is because currently, that is all we are capable of detecting.

But the surprising new population of planetary systems discovered in the Kepler data that contain several planets packed in a tiny space around their host stars does give credence to the thinking that our solar system may be somewhat unique.

However, perhaps KOI-500 used to be more like our solar system.

“From the architecture of this planetary system, we infer that these planets did not form at their current locations,” Ragozzine said. “The planets were originally more spread out and have ‘migrated’ into the ultra-compact configuration we see today.”

There are several theories about the formation of the large planets in our outer solar system which involves the planets moving and migrating inward and outward during the formation process. But why didn’t the inner planets, including Earth, move in closer, too?

“We don’t know why this didn’t happen in our solar system,” Ragozzine said, but added that KOI-500 will “become a touchstone for future theories that will attempt to describe how compact planetary systems form. Learning about these systems will inspire a new generation of theories to explain why our solar system turned out so differently.”

A few notes of interest about KOI-500:

The five planets have “years” that are only 1.0, 3.1, 4.6, 7.1, and 9.5 days.

“All five planets zip around their star within a region 150 times smaller in area than the Earth’s orbit, despite containing more material than several Earths (the planets range from 1.3 to 2.6 times the size of the Earth). At this rate, you could easily pack in 10 more planets, and they would still all fit comfortably inside the Earth’s orbit,” Ragozzine noted. KOI-500 is approximately 1,100 light-years away in the constellation Lyra, the harp.

Four of the planets orbiting KOI-500 follow synchronized orbits around their host star in a completely unique way — no other known system contains a similar configuration. Work by Ragozzine and his colleagues suggests that planetary migration helped to synchronize the planets.

“KOI” stands for Kepler Object of Interest, and Ragozzine’s findings on this system have not yet been published, and so the system has yet to officially be considered a confirmed planetary system. “Every time we find something like this we give it a license-plate-like number starting with KOI,” Ragozzine said.

When does a KOI become an official planet? Ragozzine said the process is by confirming and validating the data. “Basically you need to prove statistically or by getting a specific measurement that it is not some other astronomical signal,” he said.

This infographic from Space.com supplies more visual details:

Sources: AAS, University of Florida

October 15, 2012April 26, 2016 by Nancy Atkinson

Citizen Planet Hunters Find a Planet in a Four-Star System

A family portrait of the PH1 planetary system that was discovered in part due to crowdsourcing. Image Credit: Haven Giguere/Yale.

A family portrait of the PH1 planetary system: The newly discovered planet is depicted in this artist’s rendition transiting the larger of the two eclipsing stars it orbits. Off in the distance, well beyond the planet orbit, resides a second pair of stars bound to the planetary system. Image Credit: Haven Giguere/Yale.

A planet has been discovered orbiting in a four-star system — and no, that doesn’t mean the accommodations and conditions are excellent. It literally means four stars, where a planet is orbiting a binary star system that in turn is orbited by a second distant pair of stars. This is the first system like this that has ever been found, and its discovery demonstrates the power of citizen scientists, as it was found by a joint effort of amateurs participating on the Planet Hunters website under the guidance of professional astronomers.

This is might be an extremely rare planetary setup, astronomer Meg Schwamb from Yale says, as only six planets are currently known to orbit two stars, and none of these are orbited by other stellar companions. Astronomers are calling the newly found world a ‘circumbinary’ planet.

“Circumbinary planets are the extremes of planet formation,” said Schwamb, Planet Hunters scientist and lead author of a paper about the system presented Oct. 15 at the annual meeting of the Division for Planetary Sciences of the American Astronomical Society in Reno, Nevada. “The discovery of these systems is forcing us to go back to the drawing board to understand how such planets can assemble and evolve in these dynamically challenging environments.”

The planet is called PH1, for the first confirmed planet identified by the Planet Hunters citizen scientists, but it has the nickname of Tatooine, the planet in Star Wars that orbited two suns.

Planet Hunters uses data from the Kepler spacecraft, specially designed for looking for signs of planets.

The volunteers, Kian Jek of San Francisco and Robert Gagliano of Cottonwood, Arizona, spotted faint dips in light caused by the planet as it passed in front of its parent stars, a common method of finding extrasolar planets. Schwamb, a Yale postdoctoral researcher, led the team of professional astronomers that confirmed the discovery and characterized the planet, following observations from the Keck telescopes on Mauna Kea, Hawaii. PH1 is a gas giant with a radius about 6.2 times that of Earth, making it a bit bigger than Neptune.

“Planet Hunters is a symbiotic project, pairing the discovery power of the people with follow-up by a team of astronomers,” said Debra Fischer, a professor of astronomy at Yale and planet expert who helped launch Planet Hunters in 2010. “This unique system might have been entirely missed if not for the sharp eyes of the public.”

PH1 orbits outside the 20-day orbit of a pair of eclipsing stars that are 1.5 and 0.41 times the mass of the Sun. This planet is dense — it has perhaps about 170 times more mass than Earth — and is about half the diameter of Jupiter. It revolves around its host stars roughly every 138 days. Beyond the planet’s orbit at about 1000 AU (roughly 1000 times the distance between Earth and the Sun) is a second pair of stars orbiting the planetary system.

Gagliano, one of the two citizen scientists involved in the discovery, said he was “absolutely ecstatic to spot a small dip in the eclipsing binary star’s light curve from the Kepler telescope, the signature of a potential new circumbinary planet, ‘Tatooine,’ and it’s a great honor to be a Planet Hunter, citizen scientist, and work hand in hand with professional astronomers, making a real contribution to science.”

Jek expressed wonder at the possibility of the discovery: “It still continues to astonish me how we can detect, let alone glean so much information, about another planet thousands of light years away just by studying the light from its parent star.”

Read the paper here.

Source: Planet Hunters

October 11, 2012April 26, 2016 by Jason Major

Nearby Exoplanet Could Be Covered With Diamond

Illustration of 55 Cancri e, a super-Earth that’s thought to have a thick layer of diamond (Yale News/Haven Giguere)

If diamonds are forever then this planet should be around for a very, very long time; it appears to be literally made of the stuff.

55 Cancri e — an exoplanet discovered in 2004 — is more than twice Earth’s diameter and over eight times more massive, making it a so-called “super Earth.” Earlier this year it made headlines by being the first Earth-sized exoplanet whose light was directly observed via the infrared capabilities of NASA’s Spitzer Space Telescope.

Using information about 55 Cancri e’s size, mass and orbital velocity, as well as the composition of its parent star 55 Cancri (located 40 light years away in the constellation Cancer) a research team led by scientists from Yale University created computer models to determine what the planet is most likely made of.

They determined that 55 Cancri e is composed primarily of carbon (as graphite and diamond), iron, silicon carbide, and possibly some silicates. The researchers estimate that at least a third of the planet’s mass — the equivalent of about three Earth masses — could be diamond.

“This is our first glimpse of a rocky world with a fundamentally different chemistry from Earth. The surface of this planet is likely covered in graphite and diamond rather than water and granite.”

– Nikku Madhusudhan, Yale postdoctoral researcher and lead author

So what would one expect to find on a world made of diamond?

“On this planet there would basically be a thin layer below the surface which will have both graphite and diamond,” Madhusudhan told Universe Today in an email. “But, below that there will be a thick layer (a third of the radius) with mostly diamond. For a large part the diamond will be like the diamond on Earth, except really, really pure.

“But at greater depths the diamond could also be in liquid form,” Madhusudhan added.

Scientists had previously thought that 55 Cancri e might have a lot of water — superheated water, due to the planet’s incredibly high 4,000-degree (F) temperatures — based on the assumption that its composition is similar to Earth’s. But this new research indicates that it doesn’t have much water at all.

“By contrast, Earth’s interior is rich in oxygen, but extremely poor in carbon — less than a part in thousand by mass,” said Kanani Lee, Yale geophysicist and co-author of the paper.

This study shows that we can’t assume that planets in other systems are made of the same stuff that ours is, even if they are of similar size (and also that diamonds aren’t necessarily a valuable commodity on all worlds!)

The team’s paper “A Possible Carbon-rich Interior in Super-Earth 55 Cancri e” was accepted for publication in the journal Astrophysical Journal Letters. Read more on Yale News here.

Top image by Haven Giguere. Inset image shows visible location of 55 Cancri, by Nikku Madhusudhan using Sky Map Online.

September 26, 2012April 26, 2016 by Jason Major

Researchers Present the Sharpest Image of Pluto Ever Taken from Earth

A “speckle image” reconstruction of Pluto and its largest moon, Charon (Gemini Observatory/NSF/NASA/AURA)

Real planet, dwarf planet, KBO, who cares? What matters here is that astronomers have created the sharpest image of Pluto ever made with ground-based observations — and developed a new way to verify potential Earth-like exoplanets at the same time.

Here’s how they did it:

After taking a series of quick “snapshots” of Pluto and Charon using a recently-developed camera called the Differential Speckle Survey Instrument (DSSI), which was mounted on the Gemini Observatory’s 8-meter telescope in Hawaii, researchers combined them into a single image while canceling out the noise caused by turbulence and optical aberrations. This “speckle imaging” technique resulted in an incredibly clear, crisp image of the distant pair of worlds — especially considering that 1. it was made with images taken from the ground, 2. Pluto is small, and 3. Pluto is very, very far away.

Read: Why Pluto is No Longer a Planet

Less than 3/4 the diameter of our Moon, Pluto (and Charon, which is about half that size) are currently circling each other about 3 billion miles from Earth — 32.245 AU to be exact. That’s a long way off, and there’s still much more that we don’t know than we do about the dwarf planet’s system. New Horizons will fill in a lot of the blanks when it passes close by Pluto in July 2015, and images like this can be a big help to mission scientists who want to make sure the spacecraft is on a safe path.

“The Pluto-Charon result is of timely interest to those of us wanting to understand the orbital dynamics of this pair for the 2015 encounter by NASA’s New Horizons spacecraft,” said Steve Howell of the NASA Ames Research Center, who led the Gemini imaging study.

See images of Pluto taken by Hubble here.

In addition, the high resolution achievable through the team’s speckle imaging technique may also be used to confirm the presence of exoplanet candidates discovered by Kepler. With an estimated 3- to 4-magnitude increase in imaging sensitivity, astronomers may be able to use it to pick out the optical light reflected by a distant Earth-like world around another star.

Speckle imaging has been used previously to identify binary star systems, and with the comparative ability to “separate a pair of automobile headlights in Providence, RI, from San Francisco, CA” there’s a good chance that it can help separate an exoplanet from the glare of its star as well.

The research was funded in part by the National Science Foundation and NASA’s Kepler discovery mission, and will be published in the journal Publications of the Astronomical Society of the Pacific in October 2012. Read more here.

Main image: the first speckle reconstructed image for Pluto and Charon from which astronomers obtained not only the separation and position angle for Charon, but also the diameters of the two bodies. North is up, east is to the left, and the image section shown is 1.39 arcseconds across. Resolution of the image is about 20 milliarcseconds rms. Credit: Gemini Observatory/NSF/NASA/AURA. Inset: the Gemini North telescope on the summit of Mauna Kea. (Gemini Observatory)

September 19, 2012April 8, 2018 by Nancy Atkinson

Award-Winning Short Film is Set on an Exoplanet

A new short film called “Grounded” portrays an astronaut stranded on another planet. The film combines great storytelling with stunning effects, and the visuals are nothing short of convincingly and stunningly real. But the ethereal, dream-like nature of the film is reminiscent of the ending of the movie “2001,” so, actually understanding the plot is not what the film is about. Instead it invites “unique interpretation and reflection by the viewer,” according to the description of the film. In under 8 minutes, the film explores themes of “aging, inheritance, paternal approval, cyclic trajectories, and behaviors passed on through generations,” which is ambitious for a sci-fi genre short. “Grounded” was written, directed, edited and produced by Kevin Margo. It is perhaps one of the best short films I’ve ever seen.
Continue reading “Award-Winning Short Film is Set on an Exoplanet”

September 18, 2012December 23, 2015 by Fraser Cain

Planets Found in a Cluster of Buzzing Stars

Artist's illustration of a planet within a cluster. Image credit: NASA/JPL-Caltech

Artist’s illustration of a planet within a cluster. Image credit: NASA/JPL-Caltech

There’s a classic science fiction story called Nightfall, written by the late-great Isaac Asimov. It’s the tale of a world with six suns that fill the sky with such brightness that the inhabitants have no concept of night. And then one day, a once-in-a-thousand-years alignment causes all the stars to set at once; and everyone goes crazy!

In another case of science following science fiction, NASA-funded astronomers have discovered planets orbiting within a dense cluster of stars called the Beehive Cluster; a collection of 1,000 stars collected around a common center of gravity – Nightfall worlds?!

Well, not so fast. These worlds are “hot Jupiters;” massive, boiling hot planets that orbit their parent star closer than Mercury in our own Solar System. The two new planets have been designated Pr0201b and Pr0211b after “Praesepe”, another name for the Beehive Cluster. Although they aren’t habitable, the view from those planets in a dense cluster of stars would be awe inspiring, with hundreds of stars within a radius of 12 light-years.

Astronomers had long predicted that planets should be common in star clusters. Consider that our own Solar System probably formed within a star forming complex like the Orion Nebula. Then the individual stars drifted away from each other over time, taking their planets with them. The evolution of the Beehive cluster was different, though, with the mutual gravity of the 1,000+ stars holding themselves together over hundreds of millions of years.

“We are detecting more and more planets that can thrive in diverse and extreme environments like these nearby clusters,” said Mario R. Perez, the NASA astrophysics program scientist in the Origins of Solar Systems Program. “Our galaxy contains more than 1,000 of these open clusters, which potentially can present the physical conditions for harboring many more of these giant planets.”

Until now, only two planets had been uncovered around massive stars in star clusters, but none around sun-like stars within these clusters. So the possibility of life was out of the question. These super-jupiters aren’t habitable either, but it’s possible that smaller planets will turn up in time as well.

Beehive Cluster. Image credit: Tom Bash and John Fox/Adam Block/NOAO/AURA/NSF

The planets were discovered by using the 1.5-meter Tillinghast telescope at the Smithsonian Astrophysical Observatory’s Fred Lawrence Whipple Observatory near Amado, Arizona to measure the slight gravitational wobble the orbiting planets induce upon their host stars.

This discovery might help astronomers with another mystery that has been puzzling them for a few years: how can hot Jupiters form? How can a massive planet form so close to their parent star? Instead of forming close, it’s possible that the constant gravitational interactions among stars in young clusters push planets back and forth. Some are spun out into space as rogue planets, while others spiral inward and settle into these tight orbits.

Could there be life on Earth-sized worlds within these clusters? Are there civilizations out there who have never known the concept of night?

Probably not.

According to other researchers who released their findings just a week before the Tillinghast study, planets within star clusters like the Beehive probably aren’t habitable. In a paper titled, Can habitable planets form in clustered environments?, a team of European astronomers considered the environmental effects of star clusters on the formation and evolution of planetary systems. According to their simulations, there are just too many dynamic gravitational encounters with other stars in the cluster for any planet to remain long in the habitable zone.

Source: NASA News Release

September 10, 2012April 26, 2016 by Nancy Atkinson

Possible Subterranean Life Means More Exoplanets Could Harbor Life

Artistic representations of the only known planets around other stars (exoplanets) with any possibility to support life as we know it. Credit: Planetary Habitability Laboratory, University of Puerto Rico, Arecibo.

Artistic representation of the current five known potential habitable worlds. Will this list broaden under a new habitability model? Credit: The Planetary Habitability Laboratory (PHL)

When we think of life on other planets, we tend to imagine things (microbes, plant life and yes, humanoids) that exist on the surface. But Earth’s biosphere doesn’t stop at the planet’s surface, and neither would life on another world, says a new study that expands the so-called ‘Goldilocks Zone’ to include the possibility of subterranean habitable zones. This new model of habitability could vastly increase where we could expect to find life, as well as potentially increasing the number of habitable exoplanets.

We know that a large fraction of the Earth’s biomass is dwelling down below, and recently microbiologists discovered bacterial life, 1.4 kilometers below the sea floor in the North Atlantic, deeper in the Earth’s crust than ever before. This and other drilling projects have brought up evidence of hearty microbes thriving in deep rock sediments. Some derive energy from chemical reactions in rocks and others feed on organic seepage from life on the surface. But most life requires at least some form of water.

“Life ‘as we know it’ requires liquid water,” said Sean McMahon, a PhD student from the University of Aberdeen’s (Scotland) School of Geosciences. “Traditionally, planets have been considered ‘habitable’ if they are in the ‘Goldilocks zone’. They need to be not too close to their sun but also not too far away for liquid water to persist, rather than boiling or freezing, on the surface. However, we now know that many micro-organisms—perhaps half of all living things on Earth—reside deep in the rocky crust of the planet, not on the surface.”

Location in the night sky of the stars with potential habitable exoplanets (red circles). There are two in Gliese 581. Click the image for larger version. CREDIT: PHL @ UPR Arecibo and Jim Cornmell.

While suns warm planet surfaces, there’ also heat from the planets’ interiors. Crust temperature increases with depth so planets that are too cold for liquid water on the surface may be sufficiently warm underground to support life.

“We have developed a new model to show how ‘Goldilocks zones’ can be calculated for underground water and hence life,” McMahon said. “Our model shows that habitable planets could be much more widespread than previously thought.”

In the past, the Goldilocks zone has really been determined by a circumstellar habitable zone (CHZ), which is a range of distances from a star, and depending on the star’s characteristics, the zone varies. The consensus has been that planets that form from Earth-like materials within a star’s CHZ are able to maintain liquid water on their surfaces.
But McMahon and his professor, John Parnell, also from Aberdeen University who is leading the study now are introducing a new term: subsurface-habitability zone (SSHZ). This denote the range of distances from a star within which planets are habitable at any depth below their surfaces up to a certain maximum, for example, they mentioned a “SSHZ for 2 km depth”, within which planets can support liquid water 2 km or less underground.

If this notion catches on – which it should – it will have exoplanet hunters recalculating the amount of potentially habitable worlds.

The research was presented at the annual British Science Festival in Aberdeen.

Source: University of Aberdeen