Local Bubble
Encyclopedia
Interstellar medium
In astronomy, the interstellar medium is the matter that exists in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, dust, and cosmic rays. It fills interstellar space and blends smoothly into the surrounding intergalactic space...
(ISM) of the Orion Arm
Orion Arm
The Orion–Cygnus Arm is a minor spiral arm of the Milky Way galaxy some 3,500 light years across and approximately 10,000 light years in length. The Solar System is within the Orion–Cygnus Arm...
of the Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
. It is at least 300 light years
Light Years
Light Years is the seventh studio album by Australian recording artist Kylie Minogue. It was released on 25 September 2000 by Parlophone and Mushroom Records. The album's style was indicative of her return to "mainstream pop dance tunes"....
across and has a neutral hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
density of about 0.05 atoms per cubic centimetre, or approximately one tenth of the average for the ISM in the Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
(0.5 atoms/cc), and half that for the "Local Fluff", or Local Interstellar Cloud
Local Interstellar Cloud
The Local Interstellar Cloud is the interstellar cloud roughly 30 light years across through which the Earth's solar system is currently moving. The Solar System is thought to have entered the Local Interstellar Cloud at some time between 44,000 and 150,000 years ago and is expected to remain...
(0.1 atoms/cc). The hot diffuse gas in the Local Bubble emits X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
s.
The very sparse, hot gas of the Local Bubble is the result of supernova
Supernova
A supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...
e that exploded within the past ten to twenty million years. It was once thought that the most likely candidate for the remains of this supernova was Geminga
Geminga
Geminga is a neutron star approximately 250 parsecs away from the Sun in the constellation Gemini. Its name is both a contraction of "Gemini gamma-ray source", and gh'è minga "it's not there" in the Lombard dialect of Milan .- Pulsar :...
("Gemini gamma-ray source"), a pulsar
Pulsar
A pulsar is a highly magnetized, rotating neutron star that emits a beam of electromagnetic radiation. The radiation can only be observed when the beam of emission is pointing towards the Earth. This is called the lighthouse effect and gives rise to the pulsed nature that gives pulsars their name...
in the constellation Gemini
Gemini (constellation)
Gemini is one of the constellations of the zodiac. It was one of the 48 constellations described by the 2nd century astronomer Ptolemy and it remains one of the 88 modern constellations today. Its name is Latin for "twins", and it is associated with the twins Castor and Pollux in Greek mythology...
. More recently, however, it has been suggested that multiple supernovae in subgroup B1 of the Pleiades moving group were more likely responsible.
Description
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...
has been traveling through the region currently occupied by the Local Bubble for the last five to ten million years. Its current location lies in the Local Interstellar Cloud
Local Interstellar Cloud
The Local Interstellar Cloud is the interstellar cloud roughly 30 light years across through which the Earth's solar system is currently moving. The Solar System is thought to have entered the Local Interstellar Cloud at some time between 44,000 and 150,000 years ago and is expected to remain...
, a minor region of denser material within the Bubble. The cloud formed where the Local Bubble and the Loop I Bubble
Loop I Bubble
The Loop I Bubble is a cavity in the interstellar medium of the Orion Arm of the Milky Way. From our Sun's point of view, it is situated towards the Galactic Center of the Milky Way galaxy. Two conspicuous tunnels connect the Local Bubble with the Loop I cavity .The Loop I Bubble is located...
met. The gas within the LIC has a density of approximately 0.1 atoms per cubic centimeter.
The Local Bubble is not spherical, but seems to be narrower in the galactic plane
Galactic plane
The galactic plane is the plane in which the majority of a disk-shaped galaxy's mass lies. The directions perpendicular to the galactic plane point to the galactic poles...
, becoming somewhat egg-shaped or elliptical, and may widen above and below the galactic plane, becoming shaped like an hourglass. It abuts other bubbles of less dense interstellar medium (ISM), including, in particular, the Loop I Bubble. The Loop I Bubble was created by supernovae and stellar wind
Stellar wind
A stellar wind is a flow of neutral or charged gas ejected from the upper atmosphere of a star. It is distinguished from the bipolar outflows characteristic of young stars by being less collimated, although stellar winds are not generally spherically symmetric.Different types of stars have...
s in the Scorpius-Centaurus Association
Scorpius-Centaurus Association
The Scorpius-Centaurus Association is the nearestOB Association to the Sun. This stellar association is composed of three subgroups The Scorpius-Centaurus Association (sometimes called Sco-Cen or Sco OB2) is the nearestOB Association to the Sun. This stellar association is composed of three...
, some 500 light years from the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
. The Loop I Bubble contains the star Antares
Antares
Antares is a red supergiant star in the Milky Way galaxy and the sixteenth brightest star in the nighttime sky . Along with Aldebaran, Spica, and Regulus it is one of the four brightest stars near the ecliptic...
(also known as Alpha Scorpii), as shown on the diagram above right. Other bubbles which abut the Local Bubble are the Loop II Bubble and the Loop III Bubble.
Observation
Launched in 2003 and active until 2008, a small space observatory mission called Cosmic Hot Interstellar Plasma SpectrometerCHIPSat
CHIPSat is a now-decommissioned, but still-orbiting, microsatellite. It was launched on January 12, 2003 from Vandenberg Air Force Base aboard a Delta II with the larger ICESat, and had an intended mission duration of one year...
(CHIPS or CHIPSat) looked for the Local Bubble.
See also
- Gould BeltGould BeltThe Gould Belt is a partial ring of stars in the Milky Way galaxy, about 3000 light years across, tilted toward the galactic plane by about 16 to 20 degrees. It contains many spectral class O- and B-type stars, and may represent the local spiral arm to which the Sun belongs—currently the Sun is...
- Perseus ArmPerseus ArmThe Perseus Arm is one of two major spiral arms of the Milky Way galaxy. The second major arm is called Scutum–Centaurus Arm. Perseus Arm begins from the distal end of the long Milky Way....
- SuperbubbleSuperbubbleSuperbubble is the astronomical term used to describe a cavity hundreds of light years across filled with 106 K gas blown into the interstellar medium by multiple supernovae and stellar winds...
- List of nearest stars
- Shiva HypothesisShiva HypothesisNamed after the Hindu god of destruction, the Shiva Hypothesis is a hypothesis that purports to explain an apparent pattern in mass extinctions caused by impact events....
- Orion–Eridanus SuperbubbleOrion–Eridanus SuperbubbleThe Orion–Eridanus Superbubble, or Eridanus Soft X-ray Enhancement is a superbubble in the Orion Nebula. The region is formed from overlapping supernova remnants that may be be associated with the Orion OB1 stellar association; the bubble is approximately 1200 ly across...