Many Worlds

Tag: super-Earths

What Would Happen If Our Solar System Had a Super-Earth Like Many Others? Chaos.

March 13, 2023 / / 1 Comment

Our solar system’s rocky planets are tiny compared with the larger gas and ice giants. Exoplanet research has found, however, that the most common planets in the galaxy appear to be super-Earths and sub-Neptunes, types of planets not found in our system. Size comparison of the planets. (Alexaldo/iStock/Getty)

Before astronomers began to find planets — many, many planets — orbiting Suns other than ours,  the scientific consensus was that if other solar systems were ever found they would probably look much like ours.  That would mean small, rocky planets closest to the Sun and large gaseous planets further out.

That assumption crash and burned with the discovery of the first discovery of an exoplanet orbiting a star — 51 Peg.  It was a hot, Jupiter-sized planet that circled its Sun in four days.

That planetary rude awakening was followed by many others, including the discovery of many rocky planets much larger than those in our system which came to be called  super-Earths.  And equally common are gaseous planets quite a bit smaller than any near us, given the name sub-Neptunes.

Many papers have been written theorizing why there are no super-Earth or sub-Neptunes in our solar system.  And now astrophysicist Stephen Kane of the University of California, Riverside has taken the debate another direction by asking this question:  What would happen to our solar system planets if a super-Earth or sub-Neptune was present?

The results of his dynamic computer simulations are not pretty: the orbits of many of our planets would change substantially and that would ultimately result in some being kicked out of the solar system forever.  The forces of orbit-transforming gravity set loose by the addition of a super-Earth are strong indeed.

The term super-Earth is a reference only to an exoplanet’s size – larger than Earth and smaller than Neptune – but not suggesting they are necessarily similar to our home planet. The true nature of these planets, such as Gliese 832c, above, remains ambiguous because we have nothing like it in our own solar system. Super-Earths they are common among planets found so far in our galaxy. (Planetary Habitability Laboratory/University of Puerto Rico at Arecibo)

Let’s go back to our actual solar system for some context.

The gap in size between the size of our terrestrial planets and giant gas planets is great. The largest terrestrial planet is Earth, and the smallest gas giant is Neptune, which is four times wider and 17 times more massive than Earth.… Read more

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

March 28, 2022 / / 0 Comments

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.

… Read more

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

December 1, 2021 / / 0 Comments

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

Close and Tranquil Solar System Has Astronomers Excited

June 25, 2020 / / 0 Comments

An artist’s impression of the GJ 887 planetary system of super Earths. (Mark Garlick)

From the perspective of planet hunters and planet characterizers,  a desirable solar system to explore is one that is close to ours, that has a planet (or planets) in the star’s habitable zone,  and has a host star that is relatively quiet.  This is especially important with the very common red dwarf stars,  which are far less luminous than stars such as our sun but tend to send out many more powerful — and potentially planet sterilizing — solar flares.

The prolific members of the mostly European and Chilean Red Dots astronomy team believe they have found such a system about 11 light years away from us.  The system — GJ 887 — has an unusually quiet red dwarf host, has two planets for sure and another likely that orbits at a life-friendly 50-day orbit.  It is the 12th closest planetary system to our sun.

It is that potential third planet, which has shown up in some observations but not others, that would be of great interest.  Because it is so (relatively) close to Earth, it would be a planet where the chemical and thermal make-up of its atmosphere would likely be possible to measure.

The Red Dots team — which was responsible for the first detection of a planet orbiting Proxima Centauri and also Barnard’s star — describes the system in an article in the journal Science.  Team leader Sandra Jeffers of Goettingen University in Germany said in an email that GJ 887  “will be an ideal target because it is such a quiet star — no starspots or energetic outbursts  or flares.”

In an accompanying Perspective article in Science,  Melvyn Davies of Lund University in Sweden wrote that “If further observations confirm the presence of the third planet in the habitable zone, then GJ 887 could become one of the most studied planetary systems in the solar neighborhood.”

An artist’s impression of a flaring red dwarf star and a nearby planet. Red dwarfs are by far the most common stars in the sky, and most have planetary systems.  But scientists are unsure if they can support a habitable planet because many send out more large and powerful flares than other types of stars, especially at the beginnings of their solar lives. (Roberto Molar Candanosa/Carnegie/NASA)

GJ 877 is roughly half as massive as our sun — large for its type of star — and is the brightest red dwarf in the sky.… Read more

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