Many Worlds

Tag: planet formation

A New Twist On Planet Formation

January 30, 2023 / / 1 Comment

This image of the nearby young star TW Hydrae reveals the classic rings and gaps that signify planets are being formed in this protoplanetary disk. {ESO, Atacama Large Millimeter/submillimeter Array (ALMA)}

Before the first exoplanets were discovered in the 1990s,  our own solar system served as the model for what solar systems looked like.  The physical and chemical dynamics that formed our system were also seen as the default model for what might have occurred in solar systems yet to be found.

As the number of exoplanets identified ballooned via the Kepler Space Telescope and others, and  it became clear that exoplanets were everywhere and orbiting most every star, the model of our own solar system became obviously flawed.  The first exoplanet identified, after all, was a “hot Jupiter” orbiting very close to its star — a planetary placement previously thought to be impossible.

With the growing number of known exoplanets and their most unusual placements, the field of planet formation — focused earlier on understanding on how the planets of our system came into being and what they were made of — expanded to take in the completely re-arranged planetary and solar system menagerie being found.

This was basic science seeking to understand these newfound worlds, but it also became part of the fast-growing field of astrobiology, the search for planets that might be habitable like our own.

In this context, planet formation became associated with the effort to learn more about the dynamics that actually make a planet habitable — the needed composition of a planet, the nature of its Sun, its placement in a solar system and how exactly it was formed.

So the logic of planet formation became the subject of myriad efforts to understand what might happen when a star is born, surrounded by a ring of gas and dust that will in time include larger and larger collections of solids that can evolve into meteors, planetesimals and if all goes a particular way, into planets.

A thin section of primitive meteorite under a microscope. The various colors suggest different minerals that comprise meteorites. The round-shaped mineral aggregates are called chondrules, which are among the oldest known materials in our solar system. (Science)

As part of this very broad effort to understand better how planets form, meteorites have been widely used to learn about what the early solar system was like. Meteorites are from asteroids that formed within the first several million years of planetary accretion.… Read more

Many Planets Form in a Soup of Life-Friendly Organic Compounds

October 14, 2021 / / 0 Comments

Artist’s depiction of a protoplanetary disk with young planets forming around a star. The right-side panel zooms in to show various organic molecules that are accreting onto a planet. (M.Weiss/Center for Astrophysics | Harvard & Smithsonian)

One of the more persuasive arguments in favor of the potential existence of life beyond Earth is that the well-known chemical building blocks of that life are found throughout the galaxy.  These chemical components aren’t all present in all examined solar systems and planets, but they are common and behave in ways familiar to scientists here.

And when it comes elements and compounds found on distant planets but not found here, there just aren’t many. That doesn’t mean they don’t exist — some unstable compounds in interstellar space, for instance — but rather that the cosmos holds many surprises but none have involved extraterrestrial elements or compounds near planets or stars.

This is in large part the result of how elements are formed in the universe.  Other than hydrogen and helium, all other elements are forged in the thermonuclear explosion of stars that have exhausted their supply of fuel.  These massive explosions (supernovae) then shoot the newly-formed elements out into space where they can and do collect in gas and dust clouds that will form other new stars.  They are spread throughout the disks that form around new stars and over time they become components of new planets in formation.

This galactic evolution includes the bonding together of carbon-based organic compounds — the building blocks of life as we know it.  They are an essential component to any theory of a planet’s habitability and,  while their presence in space and star nurseries has been known for some time,  they have remained a subject of great interest but limited detailed knowledge.

That is why an international team from the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass. set out to intensively study five disks forming around young stars to determine more precisely what organic compounds were present and available for objects developing into planets.

And the results are striking:  The abundance of organic material detected was 10 to 100 times more than expected.

“These planet-forming disks are teeming with organic molecules, some of which are implicated in the origins of life here on Earth,” said team leader Karin Öberg. “This is really exciting; the chemicals in each disk will ultimately affect the type of planets that form and determine whether or not the planets can host life.”… Read more

A Young Planet Found That May Well Be Making Moons

July 27, 2021 / / 0 Comments

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

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