NGC 2261 (also known as Hubble's Variable Nebula or Caldwell 46) is a variable nebula located in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

Monoceros Monoceros (Greek: Μονόκερως, "unicorn") is a faint constellation on the celestial equator. Its definition is attributed to the 17th-century Dutch cartographer Petrus Plancius. It is bordered by Orion to the west, Gemini to the north, ...

. The nebula is illuminated by the star R Monocerotis (R Mon), which is not directly visible itself.

Observing history

NGC 2261 was discovered in 1783 by William Herschel. NGC 2261 was imaged as

Palomar Observatory Palomar Observatory is an astronomical research observatory in San Diego County, California, United States, in the Palomar Mountain Range. It is owned and operated by the California Institute of Technology (Caltech). Research time at the observat ...

's Hale Telescope's first light by

Edwin Hubble Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an Americans, American astronomer. He played a crucial role in establishing the fields of extragalactic astronomy and observational cosmology. Hubble proved that many objects ...

on January 26, 1949, some 20 years after the Palomar Observatory project began in 1928. Hubble had studied the nebula previously at Yerkes and Mt. Wilson. Hale had taken photographic plates with a 24-inch (60.96 cm) reflecting telescope in 1916. Also, plates were taken using the same telescope in 1908 by FC Jordan, allowing Hale to use of a

blink comparator A blink comparator is a viewing apparatus formerly used by astronomers to find differences between two photographs of the night sky. It permits rapid switching from viewing one photograph to viewing the other, "blinking" back and forth between th ...

to study any changes in the nebula. NGC 2261 was imaged by the Hubble Space Telescope, and an image of the nebula was released in 1999. A timelapse of NGC 2261 was provided showing a period of 6 months, from October 2021-April 2022. This was shot by over 20 astronomers at the Big Amateur Telescope. In August of 2022 the project was resumed as NGC 2261 came out from behind the sun. NGC2261 LRGB season 2021-22 18fps

Descriptions

The star R Monocerotis has lit up a nearby cloud of gas and dust, but the shape and brightness slowly changes visibly even in small telescopes over weeks and months, and the nebula looks like a small comet. One explanation proposed for the variability is that dense clouds of dust near R Mon periodically block the illumination from the star. This casts a temporary shadow on the nearby clouds.

References

External links

European Homepage for the HST
– Hubble photos and information on NGC 2261
wikispaces.com
– Images by amateur astronomers
Astrobiscuit: Seeing The Speed Of Light
fun and educational video about variable nebula and the amateur community observing them * * {{Clear

2261 In contemporary history, the third millennium of the anno Domini or Common Era in the Gregorian calendar is the current millennium spanning the years 2001 to 3000 ( 21st to 30th centuries). Ongoing futures studies seek to understand what is l ...

Monoceros (constellation) 046b Reflection nebulae Astronomical objects discovered in 1949 •

Observing history

Descriptions

See also

References

External links