Hubble's Variable Nebula: NGC 2261

Hubble's variable nebula is named (like the Hubble telescope itself) after the American astronomer Edwin P. Hubble, who carried out some of the early studies of this object. It is a fan-shaped cloud of gas and dust which is illuminated by R Monocerotis (R Mon), the bright star at the bottom end of the nebula. Dense condensations of dust near the star cast shadows out into the nebula, and as they move the illumination changes, giving rise to the variations first noted by Hubble. The star itself, lying about 2,500 light-years from Earth, cannot be seen directly, but only through light scattered off of dust particles in the surrounding nebula. R Mon is believed to have a mass of about 10 times that of the Sun, and to have an age of only 300,000 years. There is probably a symmetrical counterpart of the fan-shaped nebula on the southern side of the star, but it is heavily obscured from view by dust lying between this lobe and our line of sight.

Judy: "This object lies along the Milky Way's dusty plane in the constellation Monoceros. One of my favorite things about this kind of nebula is that it reminds us that there can be a lot unseen in space. An optical illusion is produced by human intuition: it may look to you as though this is a bright cloud against a dark surface. In reality, this is a small hole in a largely unseen cloud which allows for light from a newly forming star to shine through."

"The variation in the nebula is most likely caused by shadows being cast by blobs of dust accreting near the young star. Note that the accretion process and the star itself are impossible to see in this image, and they occur at a scale too small and too distant for Hubble to see in any detail. The presence of the dusty knots and their close proximity to the star can be inferred by the shadows they cast and how fast they move across the nebula. Because the nebula is around a light year in size, the shadows appear to flow outward, which demonstrates to us the speed of light (or the speed of darkness?) in a way that I find profoundly beautiful. Wouldn't it be wonderful if the telescope could observe this object many more times so we could watch the light flow lazily through the Universe?"

Credit: NASA and The Hubble Heritage Team (AURA/STScI)
Processing: Judy Schmidt
Judy's website: http://geckzilla.com
Release Date: June 13, 2017

Technical details:
Data collected for Proposal 5574 made this image possible.
WF/PC2 Cycle 4: Polarization Proposal

Red: F814W;POLQ
Green: F675W;POLQ
Blue: F555W;POLQ

North is 120° clockwise from up.
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