The Great Atacama Millimeter/submillimeter Array recently photographed a pair of very young protostars – newborn stars in the first few hundred thousand years of their lives, still feeding off a nearby disc of gas and dust that surrounds the stars.
What’s new – Astronomers have noticed that three points in the star’s disc seem abnormally hot. Data from other telescopes showed that two of the three hotspots also had more organic molecules than the rest of the cloud.
In a recent study, astrophysicist María José Maureira of the Max Planck Institute for Astronomical Physics and her colleagues suggest that shock waves from the two close-orbiting protostars heated these patches of dust – and created the right conditions for the formation of organic molecules, the seeding of the building blocks of a solar system with organic chemistry.
Astrophysicists recently published their work in the Astrophysical Journal Letters.
Dig into the details — The two protostars share an unwieldy name (IRAS 16293-2422 A) and a very close orbit around their common center of gravity. They are only 54 astronomical units apart, or 54 times the distance between the Earth and the Sun. For comparison, Pluto sits an average of 39 astronomical units from the Sun, which seems like a big distance when you’re talking about a dwarf planet – but it suddenly seems very crowded if you’re talking about a second star.
Because the two young stars, A1 and A2, orbit so close to each other, the gravity situation in their vicinity is quite complex, and simulations suggest that it can produce powerful and fast shock waves in the disk of gas and dust that surrounds them. . Imagine two huge fish swimming around each other in a pond, causing ripples. As a bonus, these young stars are always feasting on material that is nearby – and the stars are messy eaters, sometimes throwing discarded bits into the surrounding disk of gas and dust. It also creates shock waves in the disc.
As these shock waves pass through the cloud of gas around the two young stars, the gas compresses. This does two things: first, it heats the gas, and second, it smashes the molecules into a tighter space, giving them a chance to connect and form more complex molecules. And when the dust grains collide with the heated gas, the dust also gets hotter.
The hotspots spotted by ALMA are too far away from protostars to draw all their heat from radiation, but according to Maureira and his colleagues, their locations and temperatures match exactly what models predict when shock waves heat up the disk of material around stars. stars. .
In other words, the two infant stars that tightly surround the dusty disk’s core send ripples across the disk that leave a trail of hotspots and chemical reactions in their wake.
Why is it important – Some of the molecules produced by these chemical reactions include isocyanic acid, which is the simplest possible combination of hydrogen, nitrogen, carbon, and oxygen, the four elements that make up organic molecules. Thanks to the impulse given by the shock waves crossing the disk, the solar system which takes shape around A1 and A2 is seeded with complex organic molecules very early in its evolution. And some of these molecules could eventually become the building blocks of life.
No planet has yet formed from the cloud of dust and gas; the star system is in the first 500,000 years of its life, but according to another recent study, the building blocks of the planets – small clumps of dust called planetesimals – may begin to merge from the disk of matter around A1 and A2 in the relatively near future. And shock waves from the two protostars at its center could play a role in planet formation.
“The high temperatures of these shocks can also change the way dust particles clump together, changing how quickly planetary core formation can occur,” the European Southern Observatory says in an announcement.