The Leo Ring is an immense intergalactic cloud of

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...

and

helium Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...

gas some in diameter, in orbit of two

galaxies A galaxy is a system of stars, stellar remnants, interstellar gas, dust, dark matter, bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. ...

, in the center of the

Leo Group The M96 Group (also known as the Leo I Group) is a group of galaxies in the constellation Leo. This group contains between 8 and 24 galaxies, including three Messier objects. It also contains the Leo Ring. The group is one of many groups that ...

of galaxies, within 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 ...

of Leo.

Observation history

Radio astronomers Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. The first detection of radio waves from an astronomical object was in 1933, when Karl Jansky at Bell Telephone Laboratories reported radiation coming f ...

discovered the cloud in 1983. Astronomers had theorized that the ring was primordial gas in the process of forming a galaxy. The

GALEX Galaxy Evolution Explorer (GALEX or Explorer 83 or SMEX-7) was a NASA orbiting space telescope designed to observe the universe in ultraviolet wavelengths to measure the history of star formation in the universe. In addition to paving the way ...

satellite detected

ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...

emissions that astronomers at

Johns Hopkins University Johns Hopkins University (Johns Hopkins, Hopkins, or JHU) is a private university, private research university in Baltimore, Maryland. Founded in 1876, Johns Hopkins is the oldest research university in the United States and in the western hem ...

and the

Carnegie Institution for Science The Carnegie Institution of Washington (the organization's legal name), known also for public purposes as the Carnegie Institution for Science (CIS), is an organization in the United States established to fund and perform scientific research. Th ...

interpret to indicate star creation in newly forming

dwarf galaxies A dwarf galaxy is a small galaxy composed of about 1000 up to several billion stars, as compared to the Milky Way's 200–400 billion stars. The Large Magellanic Cloud, which closely orbits the Milky Way and contains over 30 billion stars, is s ...

in a 19 February 2009 ''

Nature Nature, in the broadest sense, is the physics, physical world or universe. "Nature" can refer to the phenomenon, phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. ...

'' paper. In 2010, it was suggested that the gas was not primordial, but instead the result of a galactic collision between the two galaxies with which the ring is closely associated.

Formation history

It has been suggested that 1.2 billion years ago,

NGC 3384 NGC 3384 is an elliptical galaxy in the constellation Leo. The galaxy was discovered by William Herschel in 1784 as part of the Herschel 400 Catalogue. The high age of the stars in the central region of NGC 3384 was confirmed after analysis of ...

collided with M96, at the heart of the

, expelling a galaxy's worth of gas into intergalactic space. This gas gathered into a vast set of clouds, the Leo Ring. The ring is now wide. The ring is composed of a collection of

H I region An HI region or H I region (read ''H one'') is a cloud in the interstellar medium composed of neutral atomic hydrogen (HI), in addition to the local abundance of helium and other elements. (H is the chemical symbol for hydrogen, and "I" is the Ro ...

s. A bridge of gas connects the ring to M96.

References

{{reflist High-velocity clouds Leo (constellation) M96 Group Astronomical objects discovered in 1983