How To Search the Chemical Makeup of Exoplanet Atmospheres for Hints at Their History

Author’s note – this article was written with Dr. Vincent Kofman, a scientist at NASA’s Goddard Space Flight Center (GSFC), working in the Sellers Exoplanet Environments Collaboration (SEEC), and the lead author on the research it discusses.

Thousands of exoplanets have been discovered in the recent decades. Planet hunters like TESS and Kepler, as well as numerous ground-based efforts, have pushed the field and we are starting to get a total number of planets that will allow us to perform effective statistical analysis on some of them.

Not only do the detected number of planets show us how common they are; it exposes our lack of understanding about how planets form, what conditions are present, and when planets may be habitable. The transit detection of an exoplanet primarily yields the orbital period, or the length of a year on the planet, and the relative size of the planet with respect to the star. The next steps are to characterize the planet. This usually requires follow up studies, using different observational strategies and more powerful telescopes.

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Meteorites Hold Early Atmospheres From Across the Solar System

Since they were formed in the early solar system, many meteorites offer an unadulterated view into what that solar system was made out of, or what happened to it as we reported before.  Recently a team of researchers led by Maggie Thompson at University of California Santa Cruz (UCSC) took a look at the chemical composition of three different chondritic meteorites, which have largely been untouched since before the planets were formed.  Their composition was different than current models predicted, and could lead to a better understanding of early planetary atmospheres.

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If Astronomers see Isoprene in the Atmosphere of an Alien World, There’s a Good Chance There’s Life There

Artists’s impression of the rocky super-Earth HD 85512 b. Credit: ESO/M. Kornmesser

It is no exaggeration to say that the study of extrasolar planets has exploded in recent decades. To date, 4,375 exoplanets have been confirmed in 3,247 systems, with another 5,856 candidates awaiting confirmation. In recent years, exoplanet studies have started to transition from the process of discovery to one of characterization. This process is expected to accelerate once next-generation telescopes become operational.

As a result, astrobiologists are working to create comprehensive lists of potential “biosignatures,” which refers to chemical compounds and processes that are associated with life (oxygen, carbon dioxide, water, etc.) But according to new research by a team from the Massachusetts Institute of Technology (MIT), another potential biosignature we should be on the lookout for is a hydrocarbon called isoprene (C5H8).

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Astronomers Find a Planet Like Jupiter, but It Doesn’t Have any Clouds

artist's depiction of the exoplanet WASP-62b from the perspective of an observer nearby to the planet

Can you picture Jupiter without any observable clouds or haze? It isn’t easy since Jupiter’s latitudinal cloud bands and its Great Red Spot are iconic visual features in our Solar System. Those features are caused by upswelling and descending gas, mostly ammonia. After Saturn’s rings, Jupiter’s cloud forms are probably the most recognizable feature in the Solar System.

Now astronomers with the Center for Astrophysics | Harvard & Smithsonian (CfA) have found a planet similar in mass to Jupiter, but with a cloud-free atmosphere.

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Astronomers Capture a Direct Image of a Brown Dwarf

First direct image of a brown dwarf star in a system not unlike our own.

The field of exoplanet photography is just getting underway, with astronomers around the world striving to capture clear images of the more than 4000 exoplanets discovered to date. Some of these exoplanets are more interesting to image and research than others.  That is certainly the case for a type of exoplanet called a brown dwarf.  And now scientists have captured the first ever image of exactly that type of exoplanet.

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If a Planet Has a Lot of Methane in its Atmosphere, Life is the Most Likely Cause

This artist’s impression shows the planet K2-18b, it’s host star and an accompanying planet in this system. K2-18b is now the only super-Earth exoplanet known to host both water and temperatures that could support life. UCL researchers used archive data from 2016 and 2017 captured by the NASA/ESA Hubble Space Telescope and developed open-source algorithms to analyse the starlight filtered through K2-18b’s atmosphere. The results revealed the molecular signature of water vapour, also indicating the presence of hydrogen and helium in the planet’s atmosphere.

The ultra-powerful James Webb Space Telescope will launch soon. Once it’s deployed, and in position at the Earth-Sun Lagrange Point 2, it’ll begin work. One of its jobs is to examine the atmospheres of exoplanets and look for biosignatures. It should be simple, right? Just scan the atmosphere until you find oxygen, then close your laptop and head to the pub: Fanfare, confetti, Nobel prize.

Of course, Universe Today readers know it’s more complicated than that. Much more complicated.

In fact, the presence of oxygen is not necessarily reliable. It’s methane that can send a stronger signal indicating the presence of life.

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James Webb Will Look for Signs of Life on Planets Orbiting Dead Stars

A planet orbiting a small star produces strong atmospheric signals when it passes in front, or “transits,” its host star, as pictured above. White dwarfs offer astronomers a rare opportunity to characterize rocky planets. Image Credit: Jack Madden/Carl Sagan Institute

Can the galaxy’s dead stars help us in our search for life? A group of researchers from Cornell University thinks so. They say that watching exoplanets transit in front of white dwarfs can tell us a lot about those planets.

It might even reveal signs of life.

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A Strange Planet has been Found that’s Smaller than Neptune But 50% More Massive

An artist's impression of K2-25b orbiting its host star, and M-dwarf in the Hyades cluster. Image Credit: NOIRLab/NSF/AURA/J. Pollard

Astronomers have found another strange exoplanet in a distant solar system. This one’s an oddball because its size is intermediate between Earth and Neptune, yet it’s 50% more massive than Neptune.

Astronomers have found what they call “puff planets” in other Solar Systems. Those are planets that are a few times more massive than Earth, but with radii much larger than Neptune’s. But this planet is the opposite of that: it’s much more massive than Neptune, but it also has a much smaller radius. Super-dense, not super-puffy.

This oddball planet is calling into question our understanding of how planets form.

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Do the TRAPPIST-1 Planets Have Atmospheres?

Most exoplanets orbit red dwarf stars because they're the most plentiful stars. This is an artist's illustration of what the TRAPPIST-1 system might look like from a vantage point near planet TRAPPIST-1f (at right). Credits: NASA/JPL-Caltech
Most exoplanets orbit red dwarf stars because they're the most plentiful stars. This is an artist's illustration of what the TRAPPIST-1 system might look like from a vantage point near planet TRAPPIST-1f (at right). Credits: NASA/JPL-Caltech

In February of 2017, the scientific community rejoiced as NASA announced that a nearby star (TRAPPIST-1) had a system of no less than seven rocky planets! Since that time, astronomers have conducted all kinds of follow-up observations and studies in the hopes of learning more about these exoplanets. In particular, they have been attempting to learn if any of the planets located in the stars Habitable Zone (HZ) could actually be habitable.

Many of these studies have been concerned with whether or not the TRAPPIST-1 planets have sufficient water on their surfaces. But just as important is the question of whether or not any have viable atmospheres. In a recent study that provides an overview of all observations to date on TRAPPIST-1 planets, a team found that depending on the planet in question, they are likely to have good atmospheres, if any at all.

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What Are Some Clues to the Climates of Exoplanets?

Credit: Cornell Chronicle

In the past few decades, the number of planets discovered beyond our Solar System has grown exponentially. To date, a total of 4,158 exoplanets have been confirmed in 3,081 systems, with an additional 5,144 candidates awaiting confirmation. Thanks to the abundance of discoveries, astronomers have been transitioning in recent years from the process of discovery to the process of characterization.

In particular, astronomers are developing tools to assess which of these planets could harbor life. Recently, a team of astronomers from the Carl Sagan Institute (CSI) at Cornell University designed an environmental “decoder” based on the color of exoplanet surfaces and their hosts stars. In the future, this tool could be used by astronomers to determine which exoplanets are potentially-habitable and worthy of follow-up studies.

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