Category: Exoplanets (page 1 of 12)

Introducing Hycean Planets

A so-called Hycean planet is one featuring large oceans and a hydrogen atmosphere. A new report from the University of Cambridge suggests this kind of planet, sized between a super-Earth and a mini-Neptunes, could potentially support life. The image features a red dwarf star as the planet’s host star. (Artist rendering by Amanda Smith, University of Cambridge)

Planets beyond our solar system, we now know, come in all shapes, sizes and consistencies.  There are rocky planets, water worlds, gaseous planets, super-Earths, hot Jupiters, tidally locked planets, planets in orbital resonance with each other,  and so much more.

A group of exoplanet researchers at the University of Cambridge have recently proposed a new category of planet, one that has seldom been considered even potentially habitable.  They call them Hycean planets due to the presence of substantial hydrogen in the atmospheres and large oceans (hydrogen and ocean = Hycean) on their surfaces.

And in an article in The Astrophysical Journal, they make the case that under certain conditions, some Hycean planets could, indeed, be habitable.

“Hycean planets open a whole new avenue in our search for life elsewhere,” said Nikku Madhusudhan from Cambridge’s Institute of Astronomy, who led the research.

Many of the prime Hycean candidates identified by the researchers are bigger and hotter than Earth, but the researchers argue that they still have the characteristics to host large oceans that could support microbial life similar to that found in some of Earth’s most extreme watery environments.

Hycean planets, Madhusudhan said in a release, offer a new paradigm for the search for life beyond Earth.

“Essentially, when we’ve been looking for these various molecular signatures, we have been focusing on planets similar to Earth, which is a reasonable place to start,”  he said. “But we think Hycean planets offer a better chance of finding several trace biosignatures.”

Co-author Anjali Piette, also from Cambridge, added: “It’s exciting that habitable conditions could exist on planets so different from Earth.”

An artist rendering of what a possible Hycean planet would look like.  This image is of K2-18b, which has a radius twice that of Earth and is more than eight times as massive as our planet.  The heavy hydrogen atmosphere is present, as is the red dwarf star that it orbits. (Alex Boersma)

There are no planets of this size and type in our solar system, but planets in the Hycean range are quite common in the galaxy.… Read more

Findings Suggest that Red Dwarf Stars May Not Sterilize Many Exoplanets As Feared

An illustration of a red dwarf star with orbiting exoplanet. The question of whether this very common type of star can support habitable planets is a much debated one. (NASA)

Red dwarf suns are the most common in the universe, and many of the exoplanets officially discovered so far orbit this type of “cool” star.  Red dwarfs are much smaller and less powerful than the G type stars such as our own sun, and it is easier to detect exoplanets orbiting them because of their reduced size and energy.

As a result, a number of relatively nearby red dwarf stars — in the Trappist-1 system, Proxima Centauri and Barnard’s star, for instance — are avidly studied for their potential habitability.  The exoplanets of red dwarfs tend to orbit much closer than around other larger stars, but the suns have that lower radiative power and so some are considered habitable candidates.  And if they are indeed habitable, they could be for a very long time because red dwarfs live much longer than most other stars.

But there have been two (at least) problems with the habitable red dwarf exoplanet scenario.  The first is that many of the planets so close to their star are tidally locked, meaning that only one side ever faces the sun.  Some have argued a tidally locked planet can still be habitable, but it would not be easy.

More crucial, however, is that red dwarf stars are known for sending out many, many powerful solar flares, especially during their solar infancy and childhood.  These high radiation and particle flares could and would potentially kill any life emerging on a dwarf exoplanet, and the stellar flares could even sterilize the planets’ atmosphere for all time.  Although direct observations have not shown this deadly scenario to be inevitable or even present, the red dwarf flaring is well documented.  And so potentially the flares have seemed to rule out, or make improbable, life on an estimated 75 percent of the stars in our galaxy.

This is why there is interest in the astrobiology world about a new paper that addresses a particular kind of stellar flare that would hit red dwarf exoplanets.  Such studies of how the behavior of a star effects orbiting planets is one of the less well studied aspects of the exoplanet field, and so the paper is especially welcomed.

And the results suggests that the red dwarf flares would strike orbiting exoplanets from an angle rather than straight on, and therefore would land in a way that would theoretically minimize damage to potential atmospheres and life.… Read more

The Many Ways The James Webb Space Telescope Could Fail

Artist rendering of the James Webb Space Telescope when it has opened and is operating. The telescope is scheduled to launch in November, 2021. (NASA)

When a damaged Apollo 13 and its crew were careening to Earth, mission control director Gene Kranz famously told the assembled NASA team that “failure is not an option.”  Actually, the actor playing Kranz in the “Apollo 13” movie spoke those words, but by all accounts Kranz and his team lived that phrase, with a drive that became a reality.

That kind of hard-driving confidence now seems to be built into NASA’s DNA, and with some tragic exceptions it has served the agency well in its myriad high-precision and high-drama ventures.

So it was somewhat surprising (and a bit refreshing)  to read the recent blog post from Thomas Zurbuchen,  NASA’s Associate  Administrator for the Space Science Directorate, on the subject of the scheduled November launch of the James Webb Space Telescope.

Thomas Zurbuchen, NASA’s Associate Administrator of the Space Science Directorate, with the new eyeglasses he introduced in his blog. (NASA)

“Those who are not worried or even terrified about (the challenges facing the JWST mission) are not understanding what we are trying to do,” he wrote.

“For most missions, launch contributes the majority of mission risk – if the spacecraft is in space, most risk is behind us. There are few types of missions that are very much different with most risk coming after launch.

“We have already performed one such mission in February when we landed on Mars. For the Perseverance rover, only 10-20% of the risk was retired during launch, perhaps 50% during the landing, and we are in the middle of the residual risk burn down as we are getting ready to drill and collect the precious Mars samples with the most complex mechanical system ever sent to another planet.

“The second such mission this year is Webb. Like a transformer in the movies, about 50 deployments need to occur after launch to set up the huge system. With 344 so-called single point failures – individual steps that have to work for the mission to be a success – this deployment after launch will keep us on edge for 3 weeks or so. For comparison, this exceeds single point failures for landing on Mars by a factor of 3, and that landing lasted only 7 minutes.”

Zurbuchen is confident that the Webb team and technology is up to the challenge but still, that is quite a risk profile.… Read more

A Young Planet Found That May Well Be Making Moons

An image made by the Very Large Telescope in Chile shows a forming planet, the bright spot at right. The overpowering light of the host star is blocked out by a coronagraph inside the telescope. (ESO/A. Müller et al.)

Astronomers have many theories about how planets are formed within the gas, dust, pebbles and gradually rocks of the circumstellar disks that encircle a star after it has been born.  While the general outlines of this remarkable process are pretty well established, many questions large and small remain unanswered.

One is how and when exomoons are formed around these planets, with the assumption that the process that forms planets must also give birth moons.  But the potential moons have been far too small for the current generation of space and ground telescopes to identify.

Now astronomers have detected something almost as significant:  a circumplanetary disk surrounding a young planet that appears to be in the process of making moons.  The moon itself has not been detected, but a forming planet has been found with a ring of dust and gas that surrounds it.  And within that circumplanetary disk, astronomers infer, a moon is possibly being formed.

“Our work presents a clear detection of a disk in which satellites could be forming,” said Dr. Myriam Benisty, an astronomer at the University of Grenoble and the University of Chile.

“The new … observations were obtained at such exquisite resolution that we could clearly identify that the disk is associated with {the exoplanet} and we are able to constrain its size for the first time,” she said in a release.

While the first detection of the planet was made via the European Southern Observatory’s Very Large Telescope in Chile, the more granular observation of the forming planet and its moon-forming disk was made with the Atacama Large Millimeter/submillimeter Array (ALMA), also in Chile.

This ALMA image shows the young PDS 70 planetary system. The system features a star at its center and at least two planets orbiting it, PDS 70b (not visible in the image) and PDS 70c, surrounded by a circumplanetary disk (the dot to the right of the star). Image credit: ALMA / ESO / NAOJ / NRAO / Benisty et al.)

The finding, published in the Astrophysical Journal Letters, came via direct imaging — in effect through extremely high power photography rather through the indirect methods much more common in exoplanet astronomy.… Read more

Earth as a Transiting Exoplanet

A view of Earth and Sun from thousands of miles above our planet. Stars that enter and exit a position where they can see Earth as a transiting planet around our Sun are brightened. (OpenSpace/American Museum of Natural History)

Exoplanet scientists and enthusiasts spend a lot of time trying to find, measure and understand distant planets that can — under specific conditions — be detected as passing in front of their host star.  A majority of the 4000-plus exoplanets discovered so far were indirectly detected this way, by measuring the diminishing of stellar light as the exoplanet passes between the star and us.

In a conceptual turnaround, two researchers have now asked the question of how common it might be for beings on distant exoplanets to be able to similarly detect and measure Earth as it transits in front of our sun.

Astronomers call this special vantage point in space – the point from which Earth transits can be seen – the Earth transit zone.  Because the cosmos is dynamic and ever-changing, they looked for not only stars that are in that zone now, but have also passed through over the past 5,000 years and will in the next 5,000 years.

“From the exoplanets’ point-of-view, we are the aliens,” said Lisa Kaltenegger, director of the Carl Sagan Institute at Cornell University.

“We wanted to know which stars have the right vantage point to see Earth, as it blocks the sun’s light.  And because stars move in our dynamic cosmos, this vantage point is gained and lost.”


Transit data are rich with information. By measuring the depth of the dip in brightness and knowing the size of the star, scientists can determine the size or radius of the planet. The orbital period of the planet can be determined by measuring the elapsed time between transits. Once the orbital period is known, Kepler’s Third Law of Planetary Motion can be applied to determine the average distance of the planet from its stars. (NASA/Ames)

How many stars (and their orbiting planets) have this proper vantage point, have had in the past and will in the future?

In Kaltenegger’s paper, published in Nature with Jackie Faherty of the astrophysics department of the American Museum of Natural History, the numbers reported are quite low.

They found that since the earliest human civilization about 5,000 years ago, only 1,715 stars among the 300,000-plus that shine within 300 light years of our sun are in the right geometric alignment for an observation of Earth passing in front of our sun. Read more

Will The Habitable Exoplanet Observatory (HabEx) — Or Something Like It — Emerge As NASA’s Next Great Observatory?

Artist impression of HabEx spacecraft and a deployed starshade 47,000 miles away, with an exoplanet made visible by the starshade’s blocking of stellar light. (NASA)

Some time later this summer, it is predicted, the National Academy of Sciences will release its long-awaited Decadal Survey for astrophysics, which is expected to recommend the science and architecture that NASA should embrace for its next “Great Observatory.”

Many Worlds earlier featured one of the four concepts in the running — LUVOIR or the Large UV/Optical/IR Surveyor.  With a segmented mirror potentially as wide as 50 feet in diameter, it would revolutionize the search for habitable exoplanets and potentially could detect one (or many) distant planets likely to support life.

Proposed as a “Great Observatory” for the 2030s in the tradition of the Hubble Space Telescope and the James Webb Space Telescope (scheduled to launch later this year), LUVOIR would allow for transformative science of not only exoplanets but many other fields of astronomy as well.

Also under serious consideration is the Habitable Exoplanet Observatory, HabEx, which would also bring unprecedented capabilities to the search for life beyond Earth.  Its mirror would be considerably smaller than that proposed for LUVOIR and it would have fewer chances to find an inhabited world.

But it is nonetheless revolutionary in terms of what it potentially can do for exoplanet science and it could come with a second spacecraft that seems to be out of science fiction,  designed to block out starlight so exoplanets nearby can be observed. That 52-meter (or 170-foot) petal-rimmed, light-blocking disc is called a starshade or an occulter, and it would fly 76,600 kilometers (or 47,000 miles) away from the HabEx spacecraft and would work in tandem with the telescope to make those close-in exoplanet observations possible.

While the capabilities of HabEx are fewer compared to LUVOIR and the potential harvest of habitable or inhabited planets is less, HabEx nonetheless would be cutting edge and significantly more capable than the Hubble Space Telescope in nearly every way, while also being less expensive than LUVOIR and requiring less of a technology reach.

Scott Gaudi, an Ohio State University astronomer, was co-chair of the NASA-created team that spent three years studying, engineering and then proposing the HabEx concept. He put the potential choice between HabEx and LUVOIR this way:  “Do you want to take a first step or a first leap?  HabEx is a major step; LUVOIR is a huge leap.”… Read more

Return to Hell: NASA Selects Two Missions to Venus to Explore the Pathway to Habitability

Artists’ renderings show the VERITAS spacecraft (left) and DAVINCI+ probe (right) as they arrive at Venus (Lockheed Martin).

For NASA scientists, Venus missions must feel like buses. You wait thirty years for one, and then two come along at once.

Last week, NASA selected two Venus missions for the space agency’s Discovery Program; solar system exploration missions that can tuck under a lower cost cap than candidates for NASA’s New Horizons or Flagship categories. The first of these is DAVINCI+, which is an orbiter equipped with a descending probe that will take a big whiff of Venus’s stifling atmosphere. The second is the VERITAS orbiter that plans to peer through the clouds to scrutinise the Venusian surface.

While Europe and Japan have both visited Venus more recently than NASA (in fact, the Japanese orbiter is still there), there is little doubt that our inner neighbor is dramatically under-explored compared to Mars. But why the past neglect, and why go twice now?

The answer to the first question is perhaps the easiest.

Venus is hell.

The planet is wrapped in a thick atmosphere consisting of carbon dioxide and clouds of sulfuric acid that beat down on the Venusian surface with pressures nearly one hundred times higher than on Earth and create temperatures sufficient to melt lead.

These conditions have made it difficult to follow the usual pattern of planetary exploration from fly-bys and orbiters to landers and rovers. The Venusian surface is so inhospitable that a rover like NASA’s Mars Perseverance would become rover goop. Although recent engineering combined with high-temperature electronics means that the surface is no longer impossible, it does greatly add to the challenge (and therefore cost) of a lander mission.

Professor Stephen Kane, University of California, Riverside.

Hell-scape conditions have also resulted in Venus being overlooked for any astrobiological studies compared to (the still rather nasty but at least you can stand a rover on the surface) Mars. This makes the urgency to explore Venus now particularly surprising. The missions are a quest to understand habitability. The bottom line is that the hell world of Venus is essential to understanding how a planet becomes habitable and to discovering other habitable worlds outside our solar system.

“Imagine you live in a small town full of life,” explains Professor Stephen Kane from the DAVINCI+ team. “The nearest town is the same size and seems it was once identical. But now, it’s burned to the ground with no sign of life.… Read more

Sure UFOs Exist. But There’s No Reason To Conclude That Aliens Are Flying Them

An apparently unidentified object detected on a Navy plane’s infrared camera. (U.S. Department of Defense/Navy Times)

It seems to happen with some regularity.  Claims that Unidentified Flying Objects are visiting us have captured the public imagination once more and a big reveal is expected soon.

That will come, oddly, from a government report required to be released by the end of June that will supposedly detail the many sightings made by high-flying military pilots and unexplained detections by satellites.  The requirement was added to the Covid relief package that was passed by Congress in December and orders the Department of Defense and the Office of the DIrector of National Intelligence to release their unclassified findings on the subject, information that has been apparently collected for decades.

In terms of national defense, these reports could indeed be meaningful.  If other nations are sending

This well known poster was first introduced during an episode of the 1990s television show, “The X Files.” and featured in a subsequent movie.

drones or satellites of some sort (true UFOs) to get close to and study American assets, then that’s important news.

But, of course, the UFO drama is overwhelmingly about something else:  The claimed presence of intelligent aliens that are scoping out Earth for reasons ranging from awe-inspiring or extremely worrisome.

The report — which sources say concludes that there is insufficient evidence to confirm or conclusively rule out extraterrestrial UFO sightings —  will no doubt be widely consumed by a population with many “UFO believers.”  After all, a 2019 Gallup poll found that 33 percent of American adults said that alien spacecraft from distant planets and galaxies have been visiting us.

I find all this to be not only unfortunate but also misguided and potentially damaging.  The moment will pass with no intelligent aliens identified, and then will return again some time in the future for another round.

The potential damage is to the very real, very challenging, very cutting-edge science being conducted around the world that seeks to identify actual signs of actual extraterrestrial life in the cosmos, or at least to know what to look for when we have space telescopes and instruments with the necessary power.

And I’m concerned that a focus on UFOs imagined to be carrying intelligent alien life takes away from the hard-won seriousness of their enormous and so compelling scientific effort.  This is especially true now that the scientific search for extraterrestrial life is on the front burner for the National Academy of Sciences, which will soon make recommendations about a next grand observatory for the 2030s.… Read more

Breakthrough Listen Searches The Crowded Center of the Milky Way for Possible Signals From Intelligent Beings

The Galactic Center from radio to X-ray frequencies.  ( X-Ray: NASA, CXC, UMass, D. Wang et al.; Radio: NRF, SARAO, MeerKAT)

Searching for technologically advanced civilizations inhabiting distant exoplanets is the astrobiological equivalent of swinging for the fences.

While much of the search of extraterrestrial life is now focused on microbes and chemical biosignatures in exoplanet atmospheres that would likely be byproducts of life, the search for extraterrestrial intelligence (or SETI) takes a very different approach.

SETI practitioners scan the skies for radio signals, and now laser signals, that are irregular and different from what is naturally produced.  Were such a signal to be detected, then it would be studied as the potential work of extraterrestrial life that is highly advanced — perhaps far more so than we Earthlings.

This search has been going on since Cornell University astronomer Frank Drake began it 1960 and has advanced (in steps large and small) ever since.  The biggest financial boost to the search took place five years ago when techno-billionaire Yuri Milner, in partnership with Stephen Hawking and other prominent scientists,  set up the Breakthrough Listen project with $100 million to buy telescope time and to greatly expand the SETI search.

And as part of that expanded search, radio telescopes focused on the crowded galactic center of the Milky Way for 600 observing hours.  The thinking was that stars and likely exoplanets are most plentiful in that central region — some 60 million  stars in the line of sight into the galactic center at low astronomical frequencies; 500,000 at higher frequencies  — and so the chances of finding a signal were perhaps higher.

Some preliminary and partial results of that effort were recently released and, unfortunately, no signals were found.  That has been the fate of all SETI searches so far.

But as SETI scientists explain, the night sky is huge and the percentage of stars (and their exoplanets) that have been sampled remains quite small.

The Green Bank Radio Observatory in West Virginia is one of the two main sites for the Breakthrough Listen galactic center campaign.  The other is the Parkes Telescope in Australia . (NRAO)

This latest effort was unique in that it was the “most sensitive and deepest targeted SETI” survey ever done of the galactic center, as the SETI scientists write in a study set to be published in the Astronomical Journal (a preprint is currently available on the arXiv).… Read more

The Space Telescope That Could Find a Second Earth

This rare picture of an exoplanet (called 2M1207B) shows a red world several times Jupiter’s size orbiting a brown dwarf much smaller and dimmer than our sun. LUVOIR is after more elusive targets: small, rocky planets around bright stars. (ESO)

What will it take to capture images and spectra of a distant world capable of harboring life?
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For all the excitement surrounding the search for distant exoplanets in recent years, the 4,000-plus planets confirmed so far have been unseen actors on the cosmic stage. Except for a handful of very large bodies imaged by ground-based telescopes, virtually all exoplanets have been detected only when they briefly dim the light coming from their host stars or when their gravity causes the star to wobble in a distinctive way. Observing these patterns and using a few other methods, scientists can determine an exoplanet’s orbit, radius, mass, and sometimes density—but not much else. The planets remain, in the words of one researcher in the field, “small black shadows.”

Scientists want much more. They’d like to know in detail the chemical makeup of the planets’ atmospheres, whether liquid water might be present on their surfaces, and, ultimately, whether these worlds might be hospitable to life.

Answering those questions will require space telescopes that don’t yet exist. To determine what kinds of telescopes, NASA commissioned two major studies that have taken large teams of (mostly volunteer) scientists and engineers four years to complete. The results are now under review by the National Academy of Sciences, as part of its Decadal Survey for Astronomy and Astrophysics that will recommend government funding priorities for the 2030s. Past and current NASA mega-projects, from the Hubble Space Telescope launched in 1990 to the James Webb Space Telescope, which is scheduled for launch this year, have all gone through this same vetting process. Sometime this spring, the Decadal Survey is expected to wrap up its deliberations and make recommendations.

That puts four proposals in the running to become NASA’s next “Great Observatory” in space: an X-ray telescope called Lynx; the Origins Space Telescope for studying the early universe; and two telescopes devoted mostly, but not exclusively, to exoplanets. One is called HabEx, for Habitable Exoplanet Observatory. The other—the most ambitious, most complex, most expensive, and most revolutionary of all these concepts—is called LUVOIR, for Large UV/Optical/IR Surveyor.… Read more

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