Do you know what’s causing massive gas and dust ejections in the Cigar galaxy?

The Cigar Galaxy, also known as Messier 82, is situated roughly 12 million light-years away in the constellation Ursa Major. It is about five times brighter than the entire Milky Way and has a galactic core hundred times more brilliant than our galaxy's centre.

Messier 82 or M82 was first discovered by Johann Elert Bode on 31 December 1774; he described it as a "nebulous patch", " of very pale and elongated shape". We previously believed the cigar galaxy to be an irregular one because it's visible to us only in sideways. But in 2005 we discovered its two symmetric spiral arms through near-infrared (NIR) images. It is prone to many supernova explosions, induced by the collapse of young, enormous stars in it. Also, M82 is an outstanding example of a starburst galaxy.

M82 or the Cigar galaxy, shines brightly at infrared wavelengths and is remarkable for its star formation activity.
The cigar galaxy/ Messier 82

Credits: NASA, ESA and the Hubble Heritage Team (STScI/AURA); Acknowledgment: J. Gallagher (University of Wisconsin), M. Mountain (STScI) and P. Puxley (National Science Foundation)

What is a starburst galaxy?

A galaxy going through an unusually high star formation rate, compared to the average star formation rate in other galaxies, is a starburst galaxy. In a starburst galaxy, stars form so rapidly that it will gobble up all its star-forming fuel much earlier than it's supposed to. Usually, starburst character is just a phase that takes up a short period of a galaxy's evolution. But sometimes it's different. Most starburst galaxies detected are in a merger or close encounter with another neighbouring galaxy.

In our case, M82 is being directly influenced by its gigantic neighbour, the spiral galaxy M81. Tidal forces caused by gravity have distorted the cigar. This process began nearly 100 million years back. This interplay has induced star formation to multiply tenfold compared to regular galaxies.

What is happening in the cigar galaxy?

A phenomenon called galactic superwind, or just galactic wind, are pretty common in starburst galaxies. Thousands of stars popping into existence all at once ejects a mighty superwind that blasts material into intergalactic space. These high-velocity cosmic winds are usually a result of newly formed large stars or supermassive black holes. But that is all the usual stuff. What is new this time?

The latest research reveals that magnetic fields around the galaxy add to the ejection of material from Messier 82.

The discoveries from NASA Stratospheric Observatory for Infrared Astronomy, or SOFIA, describe how dust and gas can travel from within galaxies into intergalactic space. The starburst galaxy enriches this material with elements like carbon and oxygen that support life. Then the winds eject this enriched material into the interstellar space to act as building blocks for new stars and galaxies. They presented this research at the American Astronomical Society meeting held between 9-12th January 2021.

, Bode’s Galaxy (M81), the central galaxy in the M81 Group, which also includes M82 and dozens of other galaxies in Ursa Major.
Messier 81 (left) and Messier 82 (right) in visible light. Image: Anttlers at

How did they do it?

SOFIA has studied the magnetic fields near the Cigar galaxy's core before. But this time it was a novel approach. Scientists used heliophysics instruments, specifically designed to study the magnetic fields around the sun to understand the magnetic field’s strength around the galaxy.

Using the High-resolution Airborne Wideband Camera(HAWK+), SOFIA found that the superwind draws the galaxy's magnetic field perpendicular to the galactic disc.

Stratospheric Observatory for Infrared Astronomy, or SOFIA
Stratospheric Observatory for Infrared Astronomy, or SOFIA

But what researchers really wanted to know something broader than that. The sun exhibits two types of emissions; the solar winds and coronal loops. Solar winds blow outwards from the sun and keep on extending throughout space. But the coronal discharge ejects from the sun and bends back again, forming loop-like structures.

They wanted to know if the magnetic field lines would extend endlessly into space like the solar wind, or simply hit the galaxy again to form coronal loop-like structures we see in the active regions of the sun.

They have found that the galaxy’s magnetic fields indeed spread out like the solar wind, letting the material blown by the superwind to slip into intergalactic space.

Why is this something remarkable?

About half a century ago, scientists developed methods to accurately deduce magnetic fields from the sun’s surface. Using SOFIA data, the research team changed this approach to determine the magnetic field about 25,000 light-years away, around the Cigar galaxy.

These magnetic fields can reveal how gas and dust observed by space telescopes travel so far away from the galaxies. NASA Spitzer Space Telescope detected dusty material 20,000 light-years beyond the galaxy, but it was a mystery why or how it had reached this far away from their stars in both directions.

We now know that the magnetic fields around galaxies have acted as a highway, creating pathways for galactic material to spread far and wide into intergalactic space.

This research helps us understand how the intergalactic space became rich in life-supporting elements for subsequent cosmic generations.

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Source: Magnetic ‘Highway’ Channels Material Out of Cigar Galaxy

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