The Bubble Nebula, including the bright star that powers it, the “shell” of material blown away by the stellar winds and the surrounding molecular cloud. Image credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA).

Hubble’s bubble illuminates the interstellar rubble

A shining bauble among a diffuse cloud of stellar debris has a tremendously interesting physics story behind it.


“Truth is tough. It will not break, like a bubble, at a touch; nay, you may kick it about all day like a football, and it will be round and full at evening.” -Oliver Wendell Holmes

From 7,100 light years away, the Bubble Nebula is one of the most clearly identifiable deep-sky objects of all.

Instead of matter blown off from a dying star, this structure arises from a massive, young and incredibly luminous star shining in a dense, matter-rich region of space.

A portion of the Bubble Nebula as imaged by the Hubble Space Telescope. Image credit: NASA, ESA, Hubble Legacy Archive; Processing & License (cc-by-3.0): Judy Schmidt.

Molecular clouds are where new stars often form, in groups or in isolation, and the Bubble Nebula is deep inside exactly one such region.

The Bubble Nebula and its surroundings, as taken via ground-based imaging. Image credit: NASA, ESA, Digitized Sky Survey 2; Acknowledgement: Davide De Martin.

Powering the Bubble is the massive O-class star BD+60 2522, which burns with a temperature of 37,500 K and a luminosity nearly 400,000 times that of our Sun.

The star powering the bubble itself, estimated at approximately 40 times the mass of the Sun. Image credit: NASA, ESA, Hubble Heritage Team.

The star is off-center from the Bubble’s center due to the fact that the interstellar medium is denser on the “short” side, making it more difficult to push matter out in that location.

The Bubble Nebula from NOAO. Image credit: Brad Ehrhorn & Adam Block, NOAO, AURA, NSF.

Emitting stellar winds at approximately 1,700 km/s, or 0.6% the speed of light, is how the bubble is created at all.

The Bubble Nebula is on the outskirts of a supernova remnant occurring thousands of years ago, potentially the source for much of the debris that lights it up. Image credit: T.A. Rector/University of Alaska Anchorage, H. Schweiker/WIYN and NOAO/AURA/NSF.

The blue color comes from partially ionized oxygen atoms, while the cooler yellow color highlights hydrogen (red) and nitrogen (green).

The Bubble Nebula, also known as NGC 7635, is an emission nebula photographed here by the Hubble Space Telescope for its 26th anniversary. Image credit: NASA, ESA, Hubble Heritage Team.

In 10 million years, this helium-burning star will finally go supernova, creating a different type of spectacular light show.


Mostly Mute Monday tells the story of a single astronomical phenomenon or object in visuals, images and video in no more than 200 words.

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