A Star has Grown Spiral Arms

Protostellar disk around a star at the galactic center. Image credit: Lu et al.

Astronomers using the ALMA Observatory have discovered an unusual, massive star near the center of our galaxy, a star that has two spiral arms. The arms are part of an accretion disk, a broad disk of dust and gas surrounding the protostar. While this is not the first star to be seen with such rare arm-like features, researchers say they believe they can track the formation of the spiral arms to a close encounter the star had with another object.

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Recent Supernovae Produced Giant Cavities in the Orion Nebula

This image of the Orion Nebula shows the puzzilng Barnard's Loop feature, a structure made of gas first identified in 1898, Image Credit: Michael Foley

The Orion Nebula is a well-known feature in the night sky and is visible in small backyard telescopes. Orion is a busy place. The region is known for active star formation and other phenomena. It’s one of the most scrutinized features in the sky, and astronomers have observed all kinds of activity there: planets forming in protoplanetary disks, stars beginning their lives of fusion inside collapsing molecular clouds, and the photoevaporative power of massive hot stars as they carve out openings in clouds of interstellar gas.

But supernova explosions are leaving their mark on the Orion Nebula too. New research says supernovae explosions in recent astronomical history are responsible for a mysterious feature first formally identified in the night sky at the end of the 19th century. It’s called Barnard’s Loop, and it’s a gigantic loop of hot gas as large as 300 light-years across.

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Star Formation Simulated in the lab, Using Lasers, of Course

Illustration of the evolution of a massive cloud which indicates the importance of SNR propagation in forming new stars. CREDIT: Albertazzi et al.

The vacuum of space isn’t really a vacuum. A vacuum is defined by Merriam-Webster as “a space absolutely devoid of matter.” However, even empty space has some matter in it. This matter, in the form of dust and gas, tends to collect into what are called molecular clouds. Without anything interfering with them they continue to float as a cloud.

When something happens to interrupt the balance of the molecular cloud, some of that dust and gas starts clumping together. As more and more of this dust and gas clump together gravity takes over and starts forming stars. One way that the balance of a molecular cloud can be interfered with is by a supernova remnant, the remains of an exploded star. Plasma jets, radiation, and other clouds can also interact with these clouds.

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Supermassive Black Holes Shut Down Star Formation

The Cigar Galaxy (M82), which is a starburst galaxy with high star production. Credit: NASA, ESA and the Hubble Heritage Team (STScI/AURA)

One of the key aspects of galactic evolution is star production. On a basic level, stars form within a galaxy’s gas and dust all the time, and where they form can help determine a galaxy’s shape and size. But there seems to be a sweet point when star production in a galaxy is particularly strong. Galaxies often have a period of rapid star production which then drops off. Astronomers are still trying to understand what causes this drop-off.

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Incredible Image Shows Twin Stellar Jets Blasting Out of a Star-Forming Region

The sinuous young stellar jet, MHO 2147, meanders lazily across a field of stars in this image captured from Chile by the international Gemini Observatory, a Program of NSF's NOIRLab. The stellar jet is the outflow from a young star that is embedded in an infrared dark cloud. Astronomers suspect its sidewinding appearance is caused by the gravitational attraction of companion stars. These crystal-clear observations were made using the Gemini South telescope’s adaptive optics system, which helps astronomers counteract the blurring effects of atmospheric turbulence. Image Credit: International Gemini Observatory/NOIRLab/NSF/AURA

Young stars go through a lot as they’re being born. They sometimes emit jets of ionized gas called MHOs—Molecular Hydrogen emission-line Objects. New images of two of these MHOs, also called stellar jets, show how complex they can be and what a hard time astronomers have as they try to understand them.

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Nearby Supernovae Exploded Just a few Million Years Ago, Leading to a Wave of Star Formation Around the Sun

Artist's illustration of the Local Bubble with star formation occurring on the bubble's surface. Scientists have now shown how a chain of events beginning 14 million years ago with a set of powerful supernovae led to the creation of the vast bubble, responsible for the formation of all young stars within 500 light years of the Sun and Earth. Credit: Leah Hustak (STScI)

The Sun isn’t the only star in this galactic neighbourhood. Other stars also call this neighbourhood home. But what’s the neighbourhood’s history? What triggered the birth of all those stars?

A team of astronomers say they’ve pieced the history together and identified the trigger: a series of supernovae explosions that began about 14 million years ago.

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Astronomers Find the Biggest Structure in the Milky Way, a Filament of Hydrogen 1,600 Light-Years Long

Composite image of the Milky Way's core created by Hubble, Spitzer, and Chandra telescopes. Credit X-ray: NASA/CXC/UMass/D. Wang et al.; Optical: NASA/ESA/STScI/D.Wang et al.; IR: NASA/JPL-Caltech/SSC/S.Stolovy

Roughly 13.8 billion years ago, our Universe was born in a massive explosion that gave rise to the first subatomic particles and the laws of physics as we know them. About 370,000 years later, hydrogen had formed, the building block of stars, which fuse hydrogen and helium in their interiors to create all the heavier elements. While hydrogen remains the most pervasive element in the Universe, it can be difficult to detect individual clouds of hydrogen gas in the interstellar medium (ISM).

This makes it difficult to research the early phases of star formation, which would offer clues about the evolution of galaxies and the cosmos. An international team led by astronomers from the Max Planck Institute of Astronomy (MPIA) recently noticed a massive filament of atomic hydrogen gas in our galaxy. This structure, named “Maggie,” is located about 55,000 light-years away (on the other side of the Milky Way) and is one of the longest structures ever observed in our galaxy.

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New Hubble Image Shows Dark Cocoons Where New Stars are Forming

This image shows knots of cold, dense interstellar gas where new stars are forming. These Free-floating Evaporating Gaseous Globules (frEGGs) were first seen in Hubble’s famous 1995 image of the Eagle Nebula. Because these lumps of gas are dark, they are rarely seen by telescopes. Image Credit: NASA, ESA, and R. Sahai (Jet Propulsion Laboratory); Processing: Gladys Kober (NASA/Catholic University of America)

Star formation is a complex process. But in simple terms, a star forms due to clumps and instabilities in a cloud of molecular hydrogen called a Giant Molecular Cloud (GMC). As more and more gas accumulates and collapses inward, the pressure becomes immense, the gas eventually heats up to millions of degrees, and fusion begins.

But what happens to the gas that remains as the young star forms? Some of it can form a type of dark halo called a frEGG—a free-floating Evaporating Gaseous Globule. And, proving that the Universe is indeed strange, the frEGG itself can contain another stellar embryo. The frEGG can be quite opaque, making it difficult to observe the star’s formation process in all its complexity.

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What’s Snuffing Out Galaxies Before Their Time?

The VERTICO—Virgo Environment Traced in Carbon Monoxide—Survey observed the gas reservoirs in 51 galaxies in the nearby Virgo Cluster and found that the extreme environment in the cluster was killing galaxies by robbing them of their star-forming fuel. In this composite image, ALMA’s radio wavelength observations of the VERTICO galaxies’ molecular gas disks are magnified by a factor of 20. They are overlaid on the X-ray image of the hot plasma within the Virgo Cluster. Credit: ALMA (ESO/NAOJ/NRAO)/S. Dagnello (NRAO)/Böhringer et al. (ROSAT All-Sky Survey)

In the Milky Way, the formation rate of stars is about one solar mass every year. About 10 billion years ago, it was ten solar masses every year. What happened?

Stars are born in giant molecular clouds (GMCs), and astronomers think that the environment in galaxies affects these clouds and their ability to spawn new stars. Sometimes the environment is so extreme that entire galaxies stop forming new stars.

Astronomers call this “quenching,” and they want to know what causes it.

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