Many Worlds

Category: What a Menagerie (page 1 of 4)

Icy Moons and Their Plumes

December 5, 2019 / / 1 Comment

The existence of water or water vapor plumes on Europa has been studied for years, with a consensus view that they do indeed exist.  Now NASA scientists have their best evidence so far that the moon does sporadically send water vapor into its atmosphere.  (NASA/ESA/K. Retherford/SWRI)

Just about everything that scientists see as essential for extraterrestrial life — carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur and sources of energy — is now known to be pretty common in our solar system and beyond.  It’s basically there for the taking  by untold potential forms of life.

But what is not at all common is liquid water.  Without liquid water Earth might well be uninhabited and today’s Mars, which was long ago significantly wetter, warmer and demonstrably habitable,  is widely believed to be uninhabited because of the apparent absence of surface water (and all that deadly radiation, too.)

This is a major reason why the discovery of regular plumes of water vapor coming out of the southern pole of Saturn’s moon Enceladus has been hailed as such a promising scientific development.  The moon is pretty small, but most scientists are convinced it does have an under-ice global ocean that feeds the plume and just might support biology that could be collected during a flyby.

But the moon of greatest scientific interest is Europa, one of the largest that orbits Jupiter.  It is now confidently described as having a sub-surface ocean below its crust of ice and — going back to science fiction writer extraordinaire Arthur C. Clarke — has often been rated the most likely body in our solar system to harbor extraterrestrial life.

That is why it is so important that years of studying Europa for watery plumes has now paid off.   While earlier observations strongly suggested that sporadic plumes of water vapor were in the atmosphere, only last month was the finding nailed, as reported in the journal Nature Astronomy.

“While scientists have not yet detected liquid water directly, we’ve found the next best thing: water in vapor form,” said Lucas Paganini, a NASA planetary scientist who led the water detection investigation.

 

As this cutaway shows, vents in Europa’s icy crust could allow plumes of water vapor to escape from a sub-surface ocean. If observed up close, the chemical components of the plumes would be identified and could help explain the nature and history of the ocean below. ( NASA) 

The amount of water vapor found in the European atmosphere wasn’t great — about an Olympic-sized pool worth of H2O.  … Read more

A Southern Sky Extravaganza From TESS

November 7, 2019 / / 0 Comments

Candidate exoplanets as seen by TESS in a southern sky mosaic from 13 observing sectors. (NASA/MIT/TESS)

NASA’s Transiting Exoplanet Survey Satellite (TESS) has finished its one year full-sky observation of  Southern sky and has found hundreds of candidate exoplanets and 29 confirmed planets.  It is now maneuvering  its array of wide-field telescopes and cameras to focus on the northern sky to do the same kind of exploration.

At this turning point, NASA and the Massachusetts Institute of Technology — which played a major role in designing and now operating the mission — have put together mosaic images from the first year’s observations, and they are quite something.

Constructed from 208 TESS images taken during the mission’s first year of science operations, these images are a unique  space-based look at the entire Southern sky — including the Milky Way seen edgewise, the Large and Small Magellenic galaxies, and other large stars already known to have exoplanet.

“Analysis of TESS data focuses on individual stars and planets one at a time, but I wanted to step back and highlight everything at once, really emphasizing the spectacular view TESS gives us of the entire sky,” said Ethan Kruse, a NASA Postdoctoral Program Fellow who assembled the mosaic at NASA’s Goddard Space Flight Center.

Overlaying the figures of selected constellations helps clarify the scale of the TESS southern mosaic. TESS has discovered 29 exoplanets, or worlds beyond our solar system, and more than 1,000 candidate planets astronomers are now investigating. NASA/MIT/TESS

The mission is designed to vastly increase the number of known exoplanets, which are now theorized to orbit all — or most — stars in the sky.

TESS searches for  the nearest and brightest main sequence stars hosting transiting exoplanets, which are the most favorable targets for detailed investigations.

This animation shows how a dip in the observed brightness of a star may indicate the presence of a planet passing in front of it, an occurrence known as a transit. This is how TESS identified planet.
(NASA’s Goddard Space Flight Center)

While previous sky surveys with ground-based telescopes have mainly detected giant exoplanets, TESS will find many small planets around the nearest stars in the sky.  The mission will also provide prime targets for further characterization by the James Webb Space Telescope, as well as other large ground-based and space-based telescopes of the future.

The TESS observatory uses an array of wide-field cameras to perform a survey of 85% of the sky.… Read more

The Remarkable Race to Find the First Exoplanet, And the Nobel Prize It Produced

October 10, 2019 / / 1 Comment

Rendering of the planet that started it all — 51 Pegasi b. It is a “hot Jupiter” that, when discovered, broke every astronomical rule regarding where types of planets should be in a solar system. (NASA)

Earlier this week, the two men who detected the first planet outside our solar system that circled a sun-like star won a Nobel Prize in physics.  The discovery heralded the beginning of the exoplanet era — replacing a centuries-old scientific supposition that planets orbited other stars with scientific fact.

The two men are Michel Mayor,  Professor Emeritus at the University of Geneva and Didier Queloz, now of Cambridge University.  There is no Nobel Prize in astronomy and the physics prize has seldom gone to advances in the general field of astronomy and planetary science.  So the selection is all the more impressive.

Mayor and Queloz worked largely unknown as they tried to make their breakthrough, in part because previous efforts to detect exoplanets (planets outside our solar system) orbiting sun-like stars had fallen short, and also because several claimed successes turned out to be unfounded.  Other efforts proved to be quite dangerous:  a Canadian duo used poisonous and corrosive hydrogen flouride vapor in the 1980s as part of their planet-hunting effort.

But since their 1995 discovery opened the floodgates, the field of exoplanet science has exploded.  More than 4,000 exoplanets have been identified and a week seldom goes by without more being announced.  The consensus scientific view is now that billions upon billions of exoplanets exist in our galaxy alone.

While Mayor and Queloz were pioneers for sure, they did not work in a vacuum.  Rather, they were in a race of sorts with an American team that had also been working in similar near anonymity for years to also find an exoplanet.

And so here is a human, rather than a purely scientific, narrative look — reported over the years — into the backdrop to the just announced Nobel Prize.  While Mayor and Queloz were definitely the first to find an exoplanet, they were quite close to being the second.

 

Swiss astronomers Didier Queloz and Michel Mayor are seen here in 2011 in front of the European Southern Observatory’s ’s 3.6-metre telescope at La Silla Observatory in Chile. The telescope hosts the High Accuracy Radial Velocity Planet Searcher (HARPS), one of the world’s leading exoplanet hunters.  After the discovery of 51 Pegasi b, Mayor led the effort to build the HARPS planet-finding spectrometer.

… Read more

Exoplanets Discoveries Flood in From TESS

August 1, 2019 / / 0 Comments

NASA’s Transiting Exoplanet Survey Satellite (TESS) has hundreds of “objects of interest” waiting to be confirmed as planets in the data from the space telescope’s four cameras.  These three were the first confirmed TESS discoveries, identified last year during its first three months of observing. By the time the mission is done, TESS’s wide-field cameras will have covered the whole sky in search of transiting exoplanets around 200,000 of the nearest (and brightest) stars. (NASA / MIT / TESS)

The newest space telescope in the sky — NASA’s Transiting Exoplanet Survey Satellite, TESS — has been searching for exoplanets for less than a year, but already it has quite a collection to its name.

The TESS mission is to find relatively nearby planets orbiting bright and stable suns, and so expectations were high from the onset about the discovery of important new planets and solar systems.  At a meeting this week at the Massachusetts Institute of Technology devoted to TESS  results,  principal investigator George Ricker pronounced the early verdict.

The space telescope, he said,  “has far exceeded our most optimistic hopes.”  The count is up to 21 new planets and 850 additional  candidate worlds waiting to be confirmed.

Equally or perhaps more important is that the planets and solar systems being discovered promise important results.  They have not yet included any Earth-sized rocky planet in a sun’s habitable zone — what is generally considered the most likely, though hardly the only, kind of planet to harbor life — but they did include planets that offer a great deal when it comes to atmospheres and how they can be investigated.

This infographic illustrates key features of the TOI 270 system, located about 73 light-years away in the southern constellation Pictor. The three known planets were discovered by NASA’s Transiting Exoplanet Survey Satellite through periodic dips in starlight caused by each orbiting world. Insets show information about the planets, including their relative sizes, and how they compare to Earth. Temperatures given for TOI 270’s planets are equilibrium temperatures, (NASA’s Goddard Space Flight Center/Scott Wiessinger)

One of the newest three-planet system is called TOI-270, and it’s about 75 light years from Earth. The star at the center of the system is a red dwarf, a bit less than half the size of the sun.

Despite its small size, it’s brighter than most of the nearby stars we know host planets. And it’s stable, making its solar system especially valuable.

… Read more

A Grand Global Competition to Name 100 ExoWorlds

June 7, 2019 / / 0 Comments

Within the framework of its 100th anniversary commemorations, the International Astronomical Union (IAU) is organising the IAU100 NameExoWorlds global competition that allows any country in the world to give a popular name to a selected exoplanet and its host star. Exoplanet rendering by IAU.

Four years ago, the International Astronomical Union organized a competition to give popular names to 14 stars and 31 exoplanets that orbit them.  The event encouraged 570,000 people to vote and the iconic planet 51 Pegasi b became “Dimidium, ” 55 Cancri b became “Galileo,” and (among others) Formalhaut b became “Dagon.”

It remains unclear how often those popular names are used in either scientific papers or writing about the papers.  But the idea of giving mythical names, names that describe something unique about the planet (or star)  or that nod to famous astronomer or iconic writers has caught on and the IAU has a new naming contest up and running.

This one is the IAU NameExoWorlds global campaign, and almost 100 nations have signed up to organize public national campaigns that will  give new names to a selected exoplanet and its host star.

“This exciting event invites everyone worldwide to think about their collective place in the universe, while stimulating creativity and global citizenship,” shared Debra Elmegreen, IAU President Elect. “The NameExoWorlds initiative reminds us that we are all together under one sky.”

From a large sample of well-studied, confirmed exoplanets and their host stars, the IAU NameExoWorlds Steering Committee assigned a star-planet system to each country, taking into account associations with the country and the visibility of the host star from most of the country.

The national campaigns will be carried out from June to November 2019 and, after final validation by that NameExoWorlds Steering Committee, the global results will be announced in December 2019. The winning names will be used freely in parallel with the existing technical scientific names.

The bulge of the Milky Way, as imaged by the Hubble Space Telescope. Our galaxy is inferred to have hundreds of billions of stars, and even more planets. (NASA, ESA, and T. Brown (STScI);

 

The naming contest flows from the well-established fact that exoplanets are everywhere — at least one around most stars, scientists have concluded.  Some 4,500 exoplanets have been identified so far, but this is but the beginning.  Astronomers are confident there are hundreds of billions of exoplanets — ranging from small and rocky like Earth to massive gas giants much larger than Jupiter — in our galaxy reaches into the many billions.… Read more

Our Ever-Growing Menagerie of Exoplanets

April 18, 2019 / / 0 Comments

While we have never seen an exoplanet with anything near this kind of detail, scientists and artists now do know enough to represent them with characteristics that are plausible, given what is known about them..  (NASA)

With so many exoplanets already detected, with the pace of discovery continuing to be so fast, and with efforts to find more distant worlds so constant and global,  it’s easy to become somewhat blase´ about new discoveries.  After so many “firsts,” and so many different kinds of planets found in very different ways, it certainly seems that some of the thrill may be gone.

Surely the detection of a clearly “Earth-like planet” would cause new excitement — one that is not only orbiting in the habitable zone of its host star but also has signs of a potentially nurturing atmosphere in a generally supportive cosmic neighborhood.

But while many an exoplanet has been described as somewhat “Earth-like” and potentially habitable, further observation has consistently reduced the possibility of the planets actually hosting some form of biology.  The technology and knowledge base needed to find distant life is surely advancing, but it may well still have a long way to go.

In just the last few days, however, a slew of discoveries have been reported that highlight the allure and science of our new Exoplanet Era.  They may not be blockbusters by themselves, but they are together part of an immense scientific exploration under way, one that is re-shaping our understanding of the cosmos and preparing us for bigger discoveries and insights to come.

 

Already 3,940 exoplanets have been identified (as of April 17) with an additional 3,504 candidates waiting to be confirmed or discarded.  this is but the start since it is widely held now that virtually every star out there has a planet, or planets, orbiting it.   That’s billions of billions of planets.  This image is a collection of NASA exoplanet renderings.

What I have in mind are these discoveries:

  • The first Earth-sized planet detected by NASA’s year-old orbiting telescope TESS (Transiting Exoplanet Survey Satellite.)  TESS is designed to find planets orbiting massive stars in our near neighborhood, and it has already made 10 confirmed discoveries.  But finding a small exoplanet — 85 percent the size of Earth — is a promising result for a mission designed to not only locate as many as 20,000 new exoplanets, but to find 500 to 1,000 the rough size of Earth or SuperEarth. 
… Read more

Weird Planets

January 2, 2019 / / 1 Comment

 

 

Artist rendering of an “eyeball world,” where one side of a tidally locked planet is always hot on the sun-facing side and the back side is frozen cold.  Definitely a tough environment, but  might some of the the planets be habitable at the edges?  Or might winds carry sufficient heat from the front to the back?  (NASA/JPL-Caltech)

The very first planet detected outside our solar system powerfully made clear that our prior understanding of what planets and solar systems could be like was sorely mistaken.

51 Pegasi was a Jupiter-like massive gas planet, but it was burning hot rather than freezing cold because it orbited close to its host star — circling in 4.23 days.  Given the understandings of the time, its existence was essentially impossible. 

Yet there it was, introducing us to what would become a large and growing menagerie of weird planets.

Hot Jupiters, water worlds, Tatooine planets orbiting binary stars, diamond worlds (later downgraded to carbon worlds), seven-planet solar systems with planets that all orbit closer than Mercury orbits our sun.  And this is really only a brief peak at what’s out there — almost 4,000 exoplanets confirmed but billions upon billions more to find and hopefully characterize.

I thought it might be useful — and fun — to take a look at some of the unusual planets found to learn what they tell us about planet formation, solar systems and the cosmos.

 


Artist’s conception of a hot Jupiter, CoRoT-2a. The first planet discovered beyond our solar system was a hot Jupiter similar to this, and this surprised astronomers and led to the view that many hot Jupiters may exist. That hypothesis has been revised as the Kepler Space Telescope found very few distant hot Jupiters and now astronomers estimate that only about 1 percent of planets are hot Jupiters. (NASA/Ames/JPL-Caltech)

 

Let’s start with the seven Trappist-1 planets.  The first three were detected two decades ago, circling a”ultra-cool” red dwarf star a close-by 40 light years away.  Observations via the Hubble Space Telescope led astronomers conclude that two of the planets did not have hydrogen-helium envelopes around them, which means the probability increased that the planets are rocky (rather than gaseous) and could potentially hold water on their surfaces.

Then in 2016 a Belgian team, using  the Transiting Planets and Planetesimals Small Telescope (TRAPPIST) in Chile, found three more planets, and the solar system got named Trappist-1. … Read more

Probing The Insides of Mars to Learn How Rocky Planets Are Formed

November 8, 2018 / / 0 Comments

An artist illustration of the InSight lander on Mars. InSight, short for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport, is designed to look for tectonic activity and meteorite impacts, study how much heat is still flowing through the planet, and track Mars’ wobble as it orbits the sun. While InSight is a Mars mission, it will help answer key questions about the formation of the other rocky planets of the solar system and exoplanets beyond. (NASA/JPL-Caltech)

In the known history of our 4.5-billion-year-old solar system,  the insides of but one planet have been explored and studied.  While there’s a lot left to know about the crust, the mantle and the core of the Earth, there is a large and vibrant field dedicated to that learning.

Sometime next month, an extensive survey of the insides of a second solar system planet will begin.  That planet is Mars and, assuming safe arrival, the work will start after the InSight lander touches down on November 26.

This is not a mission that will produce dazzling images and headlines about the search for life on Mars.  But in terms of the hard science it is designed to perform, InSight has the potential to tell us an enormous amount about the makeup of Mars, how it formed, and possibly why is it but one-third the size of its terrestrial cousins, Earth and Venus.

“We know a lot about the surface of Mars, we know a lot about its atmosphere and even about its ionosphere,” says Bruce Banerdt, the mission’s principal investigator, in a NASA video. “But we don’t know very much about what goes on a mile below the surface, much less 2,000 miles below the surface.”

The goal of InSight is to fill that knowledge gap, helping NASA map out the deep structure of Mars.  And along the way, learn about the inferred formation and interiors of exoplanets, too.

Equitorial Mars and the InSight landing site, with noting of other sites. (NASA)

The lander will touch down at Elysium Planitia, a flat expanse due north of the Curiosity landing site.  The destination was selected because it is about as safe as a Mars landing site could be, and InSight did not need to be a more complex site with a compelling surface to explore.

“While I’m looking forward to those first images from the surface, I am even more eager to see the first data sets revealing what is happening deep below our landing pads.” Barerdt said.… Read more

Water Worlds, Aquaplanets and Habitability

September 20, 2018 / / 0 Comments

This artist rendering may show a water world — without any land — or an aquaplanet with lots of more shallow water around a rocky planet. (NASA)

 

The more exoplanet scientists learn about the billions and billions of celestial bodies out there, the more the question of unusual planets — those with characteristics quite different from those in our solar system — has come into play.

Hot Jupiters, super-Earths, planets orbiting much smaller red dwarf stars — they are all grist for the exoplanet mill, for scientists trying to understand the planetary world that has exploded with possibilities and puzzles over the past two decades.

Another important category of planets unlike those we know are the loosely called “water worlds” (with very deep oceans) and their “aquaplanet” cousins (with a covering of water and continents) but orbiting stars very much unlike our sun.

Two recent papers address the central question of habitability in terms of these kind of planets — one with oceans and ice hundreds of miles deep, and one particular and compelling planet (Proxima Centauri b, the exoplanet closest to us) hypothesized to have water on its surface as it orbits a red dwarf star.

The question the papers address is whether these watery worlds might be habitable.  The conclusions are based on modelling rather than observations, and they are both compelling and surprising.

In both cases — a planet with liquid H20 and ice many miles down, and another that probably faces its red dwarf sun all or most of the time — the answers from modelers is that yes, the planets could be habitable.   That is very different from saying they are or even might be inhabited.  Rather,  the conclusions are based on computer models that take into account myriad conditions and come out with simulations about what kind of planets they might be.

This finding of potential watery-world habitability is no small matter because predictions of how planets form point to an abundance of water and ice in the planetesimals that grow into planets.

As described by Eric Ford, co-author of one of the papers and a professor of astrophysics at Pennsylvania State University, “Many scientists anticipate that planets with oceans much deeper than Earths could be a common outcome of planet formation. Indeed, one of the puzzling properties of Earth is that it has oceans that are just skin deep” compared to the radius of the planet.… Read more

A New Frontier for Exoplanet Hunting

July 18, 2018 / / 0 Comments

The spectrum from the newly-assembled EXtreme PREcision Spectrometer (EXPRES)  shines on Yale astronomy professor Debra Fischer, who is principal investigator of the project. The stated goal of EXPRES is to find many Earth-size planets via the radial velocity method — something that has never been done. (Ryan Blackman/Yale)

 

The first exoplanets were all found using the radial velocity method of measuring the “wobble” of a star — movement caused by the gravitational pull of an orbiting planet.

Radial velocity has been great for detecting large exoplanets relatively close to our solar system, for assessing their mass and for finding out how long it takes for the planet to orbit its host star.

But so far the technique has not been able to identify and confirm many Earth-sized planets, a primary goal of much planet hunting.  The wobble caused by the presence of a planet that size has been too faint to be detected by current radial velocity instruments and techniques.

However, a new generation of instruments is coming on line with the goal of bringing the radial velocity technique into the small planet search.  To do that, the new instruments, together with their telescopes. must be able to detect a sun wobble of 10 to 20 centimeters per second.  That’s quite an improvement on the current detection limit of about one meter per second.

At least three of these ultra high precision spectrographs (or sometimes called spectrometers) are now being developed or deployed.  The European Southern Observatory’s ESPRESSO instrument has begun work in Chile; Pennsylvania State University’s NEID spectrograph (with NASA funding) is in development for installation at the Kitt Peak National Observatory in Arizona; and the just-deployed EXPRES spectrograph put together by a team led by Yale University astronomers (with National Science Foundation support) is in place at the Lowell Observatory outside of Flagstaff, Arizona.

The principal investigator of EXPRES, Debra Fischer, attended the recent University of Cambridge Exoplanets2 conference with some of her team, and there I had the opportunity to talk with them. We discussed the decade-long history of the instrument, how and why Fischer thinks it can break that 1-meter-per-second barrier, and what it took to get it attached and working.

 

This animation shows how astronomers use very precise spectrographs to find exoplanets. As the planet orbits its gravitational pull causes the parent star to move back and forth. This tiny radial motion shifts the observed spectrum of the star by a correspondingly small amount because of the Doppler shift.… Read more

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