Category: Planetary Systems (page 1 of 14)

The Cosmos, As Viewed By The James Webb Space Telescope

The iconic “Pillars of Creation” image, on left, was taken in visible light by the Hubble Space Telescope in 2014. A new, near-infrared-light view from NASA’s James Webb Space Telescope, at right, helps us peer through more of the dust in this star-forming region. The thick, dusty brown pillars are no longer as opaque and many more red stars that are still forming come into view.  The pillars of gas and dust seem darker and less penetrable in Hubble’s view, and they appear more permeable in Webb’s. (NASA)

The James Webb Space Telescope was developed to allow us to see the cosmos in a new way — with much greater precision, using infrared wavelengths to piece through dust around galaxies, stars and planets, and to look further back into time and space.

In the less than four months since the first Webb images were released,  the pioneering telescope has certainly shown us a remarkable range of abilities.  And as a result, we’ve been treated to some dazzling new views of the solar system, the galaxy and beyond.  This is just the beginning and we thankfully have years to come of new images and the scientific insights that come with them.

Just as the Hubble Space Telescope, with its 32 years of service and counting, ushered in a new era of space imagining and understanding, so too is the Webb telescope revolutionizing how we see and understand our world writ large.  Very large.

Neptune as seen by Voyager 2 during a flyby more than three decades ago, the Hubble Space Telescope last year, and the JWST this summer. ( NASA/ESA/CSA))

The differences between the Webb’s image and previous images of Neptune are certainly dramatic, in terms of color, precision and what they tell us about the planet.

Surely most striking in Webb’s new image is the crisp view of the planet’s rings, some of which have not been seen since NASA’s Voyager 2 became the first spacecraft to observe Neptune during its flyby in 1989. In addition to several bright, narrow rings, the Webb image clearly shows Neptune’s fainter, never-seen dust bands as well.

Neptune is an ice giant planet. Unlike Jupiter and Saturn, which consist primarily of hydrogen and helium, Neptune has an interior that is much richer in heavier elements (“heavier is the sense of not hydrogen or helium.) One of the most abundant heavy molecules is methane, which appears blue in Hubble’s visible wavelengths but largely white in the Webb’s near-infrared camera.… Read more

The Juno Spacecraft Images Jupiter’s Moon Europa as it Speeds Past

The first image from NASA’s Juno spacecraft as it passed close by Europa as part of its extended mission.  (NASA)

For NASA to extend its space science missions well past their original lifetime in space has become such a commonplace that it is barely noticed.

The Curiosity rover was scheduled to last on Mars for two years but now it has been going for a decade — following the pace set by earlier, smaller Mars rovers.  The Cassini mission to Saturn was extended seven years beyond it’s original end date and nobody expected that Voyager 1, launched in 1977,  would still flying out into deep space and sending back data 45 years later.

The newest addition to this virtuous collection of over-achievers is the Juno spacecraft, which arrived at Jupiter in 2016.  Its prime mission in and around Jupiter ended last year and then was extended until 2025, or beyond.

And now we have some new and intriguing images of Jupiter’s moon Europa thanks to Juno and its extension.

Traveling at a brisk 14.7 miles per second, Juno passed within 219 miles of the surface of the icy moon on Thursday and images from the flyby were released today (Friday.)  That gave the spacecraft only a two-hour window to collect data and images, but scientists are excited.

“It’s very early in the process, but by all indications Juno’s flyby of Europa was a great success,” said Scott Bolton, Juno principal investigator from Southwest Research Institute in San Antonio, in a NASA release.

“This first picture is just a glimpse of the remarkable new science to come from Juno’s entire suite of instruments and sensors that acquired data as we skimmed over the moon’s icy crust.”

Candy Hansen, a Juno co-investigator who leads planning for the Juno camera at the Planetary Science Institute in Tucson, called the released images “stunning.”

“The science team will be comparing the full set of images obtained by Juno with images from previous missions, looking to see if Europa’s surface features have changed over the past two decades,” she said.

An image of Europa taken by the Galileo spacecraft as it passed the moon in 1998. (NASA/JPL-Caltech)

During the flyby, the mission collected what will be some of the highest-resolution images of the moon (0.6 miles per pixel) taken so far and obtained valuable data on Europa’s ice shell structure, interior, surface composition, and ionosphere, in addition to the moon’s interaction with Jupiter’s magnetosphere.… Read more

How Planetary Orbits, in Our Solar System and Beyond, Can Affect Habitability

Varying degrees of orbital eccentricity around a central star. (NASA/JPL-Caltech)

As scientists work to understand what might make a distant planet habitable, one factor that is getting attention is the shape of the planet’s orbit, how “eccentric” it might be.

It might seem that a perfect circular orbit would be ideal for habitability because it would provide stability, but a new model suggests that it is not necessarily the case.  The planet in question is our own and what the model shows is that if Jupiter’s orbit were to change in certain ways, our planet might become more fertile than it is.

The logic play out as follows:

When a planet has a perfectly circular orbit around its star, the distance between the star and the planet never changes and neither does the in-coming heat. But most planets — including our own — have eccentric orbits around their stars, making the orbits oval-shaped. When the planet gets closer to its star it receives more heat, affecting the climate.

Using multi-factored models based on data from the solar system as it is known today, University of California, Riverside (UCR) researchers created an alternative solar system. In this theoretical system, they found that if Jupiter’s orbit were to become more eccentric, it would in turn produce big changes in the shape of Earth’s orbit.  Potentially for the better.

“If Jupiter’s position remained the same but the shape of its orbit changed, it could actually increase this planet’s habitability,” said Pam Vervoort, UCR Earth and planetary scientist and study lead author.

The paper upends two long-held scientific assumptions about our solar system, she said.

“Many are convinced that Earth is the epitome of a habitable planet and that any change in Jupiter’s orbit, being the massive planet it is, could only be bad for Earth,” Vervoort said in a release. “We show that both assumptions are wrong.”

Size comparison of Jupiter and Earth shows why any changes relating to the giant planet would have ripple effects. (NASA)

 

As she and colleagues report in the Astronomical Journal, if Jupiter pushed Earth’s orbit to become more eccentric based on its new gravitational pull, parts of the Earth would sometimes get closer to the sun.  As a results, parts of the Earth’s surface that are now sub-freezing would get warmer, increasing temperatures in the habitable range.

While the Earth-Jupiter connection is a focus of the paper and forms a relationship that’s not hard to understand, the thrust of the paper is modeling how similar kinds of exoplanet orbits and solar system relationships can affect habitability and the potential for life to emerge and prosper.… Read more

New Research Finds The Very Early Solar System Went Through an Especially Intense Period of Asteroid Collisions

An artist’s view of the very early solar system, where dust was collecting into small rocks, which smashed into each other and some became larger. The height of the crash-ups took place during a surprisingly short period of time. (Tobias Stierli, flaeck / PlanetS)

In the earliest days of our solar system — before any planets had been cobbled together — the recently formed Sun was circled by cosmic gas and dust. Over time, fragments of rock formed from the dust and many of these orbiting rocks smashed together and some became the gradually larger components of planets-to-be.  Others were not part of any planet formation and became asteroids orbiting the Sun, and sometimes falling to Earth as meteorites.

Scientists have found that these asteroids (and their Earth-bound pieces) remained relatively unchanged since their formation billions of years ago.

And so they provide an archive of sorts, in which the conditions of the early solar system are preserved.

Alison Hunt, a planetary scientist at ETH Zurich in Switzerland, led a team that looked at some of that early solar system history and came up with some surprising results.

She and her team at the Swiss National Centre of Competence in Research (NCCR) PlanetS found that almost all of the asteroidal-cores-turned-meteorites they studied had been formed in a short four-million-year period starting almost eight million years the solar system first came into being.  A four million-year time span is short in astronomical terms and also unusual in terms of the precision achieved for the dating.

These results, and some inferences about why this period was so chaotic in the early solar system, were reported in Nature Astronomy late last month.

But before we look at why this might have happened, let’s explore a bit about how the team achieved such precise data about when many asteroids were formed.

One of the iron meteorite samples the team analyzed that was, long ago, the core of an asteroid. (Aurelia Meister)

To access this asteroid/meteorite archive, the researchers had to prepare and examine the extraterrestrial material from iron meteorites that had fallen to Earth.  Once part of the metallic cores of asteroids, samples from 18 different iron meteorites were used in the analysis.

The researchers first had to dissolve the samples to be able to isolate the elements palladium, silver and platinum — the key to their efforts.

Using a mass spectrometer they measured abundances of different and identifiable isotopes of these elements, and with their results they could put tighter constraints on the timing of events in the early solar system.

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A Clue Into The Makeup of Jupiter’s Moon Europa Provided by the Greenland Ice Sheet

Double ridge ice formations seen on Europa are similar to formations detected on the Greenland Ice Sheet. This artist’s rendering shows how double ridges on the surface of Jupiter’s moon Europa may form over shallow, refreezing water pockets within the ice shell. This mechanism is based on the study of an analogous double ridge feature found on Earth’s Greenland Ice Sheet. (Justice Blaine Wainwright)

Europa’s ice crust is crossed by thousands of double ridges, pairs of long parallel raised lines with a small valleys in between, sometimes as much as hundreds of miles long and skyscraper-height tall rims. While these double ridges are ubiquitous on Europa’s surface, how they form remains something of a mystery to scientists.

Dustin Schroeder, an associate professor of geophysics at Stanford University’s School of Earth, Energy & Environmental Sciences, was working on an issue related to climate change when he saw double ridges similar to those seen on Europa here on Earth.  The ridges, in Northwest Greenland, were tiny when compared with those on Europa, but the found the same “M”-shaped crest as found everywhere on that Jovian moon.

“We were working on something totally different related to climate change and its impact on the surface of Greenland when we saw these tiny double ridges – and we were able to see the ridges go from ‘not formed’ to ‘formed,’ ” Schroeder said.

Could the double ridges be forming as a result of processes similar to those that form the double ridges on Europa?

If so, then Greenland would provide a possibly important new window into a central question about Europa:  Is that thick ice shell surrounding the subsurface ocean completely solid, or does it have what are called “water sills” within the shell?

This is important because, as the Nature Communications paper concludes, “If the same process is responsible for Europa’s double ridges, our results suggest that shallow liquid water is spatially and temporally ubiquitous across Europa’s ice shell.”

Or as Schroeder put it, “If the mechanism we see in Greenland is how these things happen on Europa, it suggests there’s water everywhere,” he said in a release.

They can make this inference because the double ridges formed in Greenland are the known, and detectable, result of the dynamics of subsurface water surrounded by the ice sheet.

Surface imagery comparison of a double ridge on Europa (a) and on Earth (b), on the Northwest Greenland Ice Sheet.

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The World’s Most Capable Space Telescope Readies To Observe. What Will Exoplanet Scientists Be Looking For?

This artist’s concept shows what the TRAPPIST-1 planetary system may look like, based on available data about the planets’ diameters, masses and distances from the host star.  The James Webb is expected to begin science observations this summer. (NASA/JPL-Caltech)

The decades-long process of developing, refining, testing, launching, unfurling and now aligning and calibrating the most capable space telescope in history is nearing fruition.  While NASA has already released a number of “first light” images of photons of light moving through the James Webb Space Telescope’s optical system, the  jaw-dropping “first light” that has all the mirrors up and running together to produce an actual scientific observation is a few months off.

Just as the building and evolution of the Webb has been going on for years, so has the planning and preparation for specific team observation “campaigns.”   Many of these pertain to the earliest days of the universe, of star and galaxy formation and other realms of cosmology,  but an unprecedented subset of exoplanet observations is also on its way.

Many Worlds earlier discussed the JWST Early Release Science Program, which involves observations of gigantic hot Jupiter planets to both learn about their atmospheres and as a way to collect data that will guide exoplanet scientists in using JWST instruments in the years ahead.

Now we’ll look at a number of specific JWST General Observation and Guarantreed Time efforts that are more specific and will collect brand new information about some of the major characteristics and mysteries of a representative subset of the at least 100 billion exoplanets in our galaxy.

This will be done by using three techniques including transmission spectroscopy — collecting and analyzing the light that passes through an exoplanet’s atmosphere as it passes in front of its Sun.  The JWST will bring unprecedented power to characterizing the wild diversity of exoplanets now known to exist; to the question of whether “cool” and dim red dwarf stars (by far the most common in the galaxy) can maintain atmospheres; to newly sensitive studies of the chemical makeup of exoplanet atmospheres; and to the many possibilities of the TRAPPIST-1 exoplanets, a seven rocky planet solar system that is relatively nearby.

An artist’s interpretation of GJ 1214b,one of a group of super-Earth to mini-Neptune sized planets to be studied in the JWST Cycle1 observations. The planet is known to be covered by a thick haze which scientists expect the JWST to pierce as never before and allow them to study atmospheric chemicals below.

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Venus, as Never Seen Before

The darkside of Venus, as imaged by an optical and near infrared camera on NASA’s Parker Solar Probe. (NASA)

For the first time, the surface of Venus has been imaged in visible wavelengths from space. The camera on the Parker Solar Probe pierced through the thick Venusian cloud cover and captured blurred but extremely valuable images of the highlands and lowlands of the planet.

The breakthrough images came thanks to a spacecraft with an entirely different mission — the Parker Probe, which has been exploring and progressively nearing the Sun in unprecedented ways.  And to get ever closer, it uses trips around Venus to slow down and thereby fly closer to the Sun.

It was during two of those trips around Venus in 2000 and 2001 that the Parker camera, which sees in visible and near infrared wavelengths, was able to  image the night side of Venus.  This was a first and totally unexpected, since Venus is known to have a dense cover of clouds.

The planet is also, of course, stunningly hot, with a mean temperature of 867 degrees Fahrenheit on the surface.  But the temperatures are lower on the elevated Aphrodite Terra, the largest highland region on the Venusian surface, and that is the area that shows as being dark in the images.

“Venus is the third brightest thing in the sky, but until recently we have not had much information on what the surface looked like because our view of it is blocked by a thick atmosphere,” said Brian Wood, lead author on the new study in Geophysical Research Letters and a physicist at the Naval Research Laboratory in Washington.  “Now, we finally are seeing the surface in visible wavelengths for the first time from space.”

The presentation below, put together by NASA, the John’s Hopkins University Applied Physics Lab and Naval Research Lab, is a stitched together video of the Parker Probe’s  Feb. 20, 2021 pass by the dark side of the planet.

Clouds of sulfur dioxide and sulfuric acid obstruct most of the visible light coming from Venus’ surface and so observing from both the ground and from space has relied on radar and observing wavelengths in the infrared that can pierce through the clouds.

But on two passes, the the Parker Probe’s Wide-field Imager for Solar Probe (WISPR) picked up a range of wavelengths from 470 nanometers to 800 nanometers. Some of that light is the near-infrared – wavelengths that we cannot see, but sense as heat – and some is in the visible range, between 380 nanometers and about 750 nanometers.… Read more

More On The Very Hot Science of Stellar Flares and Their Implications For Habitability

A solar flare, imaged by NASA’s Solar Dynamics Observatory.

Among the many scientific fields born, or reborn, by the rise of astrobiology and its search for life beyond Earth is the study of stars, including our own Sun.  Now that we know that planets — from the large and gaseous to the small and rocky — are common in our galaxy and number in the many, many billions, there is suddenly vast amount of real estate where life potentially could arise.

We already know that many of those planets large and small are not candidates for habitability for any number of reasons, and that makes the understanding of what general conditions are required for life all the more pressing.

And as the astrobiological effort speeds ahead, it has become clear that the make-up, behavior and location of the stars that host exoplanets is central to that understanding.

Many stellar issues are suddenly important, and perhaps none more so than the nature, frequency and consequences of the constant stellar eruption of  flares, superflares and coronal mass ejections.

Created as intense bursts of radiation coming from the release of magnetic energy following reconnections in stars’ coronas, flares and related coronal mass ejections are the largest explosive events in solar systems. The energy released by a major flare from our Sun is about a sixth of the total solar energy released each second and equal to 160,000,000,000 megatons of TNT

The current focus of study is flares coming off red dwarf stars — much smaller and less energetic than our Sun, but the most common stars in the galaxy, by a lot.  Many are already known to have multiple rocky planets within a distance from the star termed the “habitable zone,” where in theory water could sometimes be liquid.

But red dwarf stars universally experience intense flaring in their early periods, and the planets orbiting in the those red dwarf habitable zones can be 20 times closer to their stars than we are to the Sun.

The crucial question is whether those flares forever sterilize the planets in their systems, which is certainly a possibility.  But a related question is whether the flares might also deliver amounts of ultraviolet radiation that may be essential to the formation of the chemical building blocks of life.

Not surprisingly, this is a subject of not only intense study but of heated debate as well.

Violent stellar flares from young red dwarf stars, as illustrated here, could potentially evaporate the atmosphere of a planet.

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What The James Webb Space Telescope Can Do For Exoplanet Science and What It Cannot Do

The James Webb Space Telescope, as rendered by an artist. The telescope is scheduled to launch later this month. (NASA)

When the James Webb Space Telescope finally launches (late this month, if the schedule holds) it will forever change astronomy.

Assuming that its complex, month-long deployment in space works as planned, it will become the most powerful and far-seeing observatory in the sky.  It will have unprecedented capabilities to probe the earliest days of the universe, shedding new light on the formation of the first stars and galaxies.  And it will observe in new detail the most distant regions of our solar system.

Deep space astrophysics is what JWST was first designed for in the early 1990s, and that will be its transformative strength.

But much is also being made of what JWST can do for the study of exoplanets and some are even talking about how it just might be able to find biosignatures — signs of distant life.

While it is probably wise to never say never regarding an observatory with the power and capabilities of JWST,  the reality is that it was not designed to look for the exoplanets most likely to be habitable.  Actually, when it was first proposed, the observatory had no exoplanet-studying capabilities at all because no exoplanets had yet been found.

What was added on is substantial and exoplanet scientists say JWST can help advance the field substantially.  But there are definite limits and finding biosignatures — life — is almost certainly a reach too far for JWST.

When starlight passes through a planet’s atmosphere, certain parts of the light are absorbed by the atmosphere’s elements. By studying which parts of light are absorbed, scientists can determine the composition of the planet’s atmosphere. (Christine Daniloff/MIT, Julien de Wit)

Astronomer Jacob Bean of the University of Chicago, who has played a leadership role in planning JWST exoplanet observations for the telescope’s early day, says that people need to know these limitations so the pioneering exoplanet science that will be possible with JWST is not seen as somehow disappointing.

As he explained, it is essential to understand that the kind of exoplanet observing that the JWST will mostly do is “transit spectroscopy.”  This involves staring at a star when an exoplanet is expected to transit in front of it.  When that happens, light from the star will pass through the atmosphere of the exoplanet (if there is one) and through spectroscopy scientists can determine what molecules are in that hoped-for atmosphere.… Read more

Why Does Our Solar System Have No Super-Earths, and Other Questions for Comparative Planetology

An artist’s impression of the exoplanet LHS 1140b, which orbits a red dwarf star 40 light-years from Earth. Using the European Southern Observatory’s telescope at La Silla, Chile, and other telescopes around the world, an international team of astronomers discovered this super-Earth orbiting in the habitable zone around the faint star LHS 1140. This world is a little larger and much more massive than the Earth. (ESO)

Before the explosion in discovery of extrasolar planets, the field of comparative planetology was pretty limited  — confined to examining the differences between planets in our solar system and how they may have come to pass.

But over the past quarter century, comparative planetology and the demographics of planets came to mean something quite different.  With so many planets now identified in so many solar systems, the comparisons became not just between one planet and another but also between one solar system and another.

And the big questions for scientists became the likes of:  How and why are the planetary makeups of distant solar systems often so different from our own and from each other; what does the presence  or absence of large planets in a solar system do to the distribution of smaller planets;  how large can a rocky planet can get before it turns to a gas giant planet; and on a more specific subject, why do some solar systems have hot Jupiters close to the host star and others have cold Jupiters much further out like our own

Another especially compelling question involves our own solar system, though as something of an outlier rather than a prototype.

That question involves the absence in our solar system of anything in the category of a “super-Earth” — a rocky or gaseous extrasolar planet with a mass greater than Earth’s but substantially below those of our solar system’s planets next in mass,  Uranus and Neptune.

The term “super-Earth” refers only to the mass and radii of the planet, and so does not imply anything about the surface conditions or habitability. But in the world of comparative planetology “super-Earths” are very important because they are among the most common sized exoplanets found so far and some do seem to have planetary characteristics associated with habitability.

Yet they do not exist in our solar system.  Why is that?

Artist rendition of Earth in comparison to one of the many super-Earth planets. (NASA)

In a recent article in The Astrophysical Journal Letters,  planetary demographer Gijs D.… Read more

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