There's an intriguing class of objects out there known as "variable nebulae", the most famous of which is probably Hubble's Variable Nebula. They are primarily reflection nebulae illuminated by various stars, with variation in brightness occuring on timescales as short as weeks and months.
An amateur astronomer Julian "Jay" McNeil discovered a nebula with a 3-inch refractor from his backyard in Paducah, Kentucky, on January 23rd 2004. Days later after processing he noted substantial but not totally unfamiliar nebulosity in this region! He spotted it in a CCD image he had taken of familiar reflection nebula M78 in Orion. Although not visible in several photographic plates dating back from 1966, this new nebula is present in one of the image from 1966, providing early hints of its variability. His amazing discovery is now recognized as a newly visible reflection nebula surrounding a new born star -- McNeil's Nebula.
The emergence of McNeil's Nebula is rare event to witness and astronomers are eagerly following its development, but orion will soon lie too close to the sun in the sky, interrupting further observations for several months. The Orion nebula, complex in itself, is around 1,500 light-years away.
So when McNeil's Nebula was identified, astronomers, both amateur and professional, anticipated that it would fade and then re brighten around 2042, based on the interval during which it was dark between 1966 and 2004. Since discovery, it had varied brightness but never vanished altogether . It had presumably been obscured by associated gas and dust from molecular clouds.
Mike Harlow (Orwell Astronomical Society Ipswich) reports that McNeil's nebula in Orion has disappeared from view in an image taken using the University of Iowa's 500 mm Gemini telescope. Followed up by Nick Hewitt (Northampton, UK) using iTelescope 24 (a 610 mm CDK Planeware reflector at Sierra Remote telescope, California, USA) on November 6th, 2018 at 0920 UT and this confirmed the absence. Another observer using a 30-inch Dobsonian telescope on November 3 also failed to detect the nebula
Who knows when McNeil's Nebula will be illuminated again? Will it surprise us by reappearing in few weeks? or have we seen its last puff, never to be seen again?