Barnard's Star is a relatively well-studied astronomical object, and has likely received more attention than any other
M dwarf star given its proximity and favourable location for observation near the
celestial equator. It has also been the subject of some controversy. For a decade from the early 1960s onward, an erroneous discovery of a
planet or planets in orbit around Barnard's star was accepted by astronomers. It is also notable as the target for a study on the possibility of rapid, unmanned travel to nearby star systems. Research has focused on stellar characteristics,
astrometry, and refining the limits of possible planets.
A binary star is a
stellar system consisting of two
starsorbiting around their
center of mass. For each star, the other is its companion star. Recent research suggests that a large percentage of stars are part of systems with at least two stars. Binary star systems are very important in
astrophysics, because observing their mutual orbits allows their
mass to be determined. The masses of many single stars can then be determined by extrapolations made from the observation of binaries.
Binary stars are not the same as
optical double stars, which appear to be close together as seen from
Earth, but may not be bound by
gravity. Binary stars can either be distinguished optically (visual binaries) or by indirect techniques, such as
spectroscopy. If binaries happen to orbit in a plane containing our line of sight, they will
eclipse each other; these are called eclipsing binaries.
The components of binary star systems can exchange mass, bringing their
evolution to stages that single stars cannot attain. Examples of binaries are
Algol (an eclipsing binary),
Sirius, and
Cygnus X-1 (of which one member is probably a
black hole).
The Cat's Eye Nebula (NGC 6543) is a
planetary nebula in the constellation of
Draco. Structurally, it is one of the most complex nebulae known, with high-resolution
Hubble Space Telescope observations revealing remarkable structures such as knots, jets and sinewy arc-like features.
Modern studies reveal several mysteries. The intricacy of the structure may be caused in part by material ejected from a
binary central star, but as yet, there is no direct evidence that the central star has a companion. Also, measurements of chemical abundances reveal a large discrepancy between measurements done by two different methods, the cause of which is uncertain.
Comet Hyakutake (
Japanese: 百武彗星 Hyakutake suisei,
IPA[çakɯtakesɯiseː];
formally designatedC/1996 B2) is a
comet that was discovered in January 1996, and passed very close to the Earth in March of that year. It was dubbed The
Great Comet of 1996, and was one of the closest cometary approaches to the Earth in the previous 200 years, resulting in the comet appearing very bright in the night sky and being seen by a large number of people around the world. The comet temporarily upstaged the long-awaited
Comet Hale–Bopp, which was approaching the inner
Solar System at the time, although Hyakutake was at its brightest for only a few days.
Scientific observations of the comet led to several notable discoveries. Most surprising to cometary scientists was the discovery of
X-ray emission from the comet, the first time a comet had been found to be emitting X-rays. This emission is believed to be caused by ionised
solar wind particles interacting with neutral
atoms in the
coma of the comet. The
Ulysses spacecraft also unexpectedly crossed the comet's tail at a distance of more than
500 million km from the
nucleus, showing that Hyakutake had the longest tail yet known for a comet.
Hyakutake is a
long-period comet. Before its most recent passage through the Solar System, its orbital period was about 15,000 years, but the
gravitational influence of the
giant planets has now increased this to 72,000 years.
Barnard's Star is a relatively well-studied astronomical object, and has likely received more attention than any other
M dwarf star given its proximity and favourable location for observation near the
celestial equator. It has also been the subject of some controversy. For a decade from the early 1960s onward, an erroneous discovery of a
planet or planets in orbit around Barnard's star was accepted by astronomers. It is also notable as the target for a study on the possibility of rapid, unmanned travel to nearby star systems. Research has focused on stellar characteristics,
astrometry, and refining the limits of possible planets.
A binary star is a
stellar system consisting of two
starsorbiting around their
center of mass. For each star, the other is its companion star. Recent research suggests that a large percentage of stars are part of systems with at least two stars. Binary star systems are very important in
astrophysics, because observing their mutual orbits allows their
mass to be determined. The masses of many single stars can then be determined by extrapolations made from the observation of binaries.
Binary stars are not the same as
optical double stars, which appear to be close together as seen from
Earth, but may not be bound by
gravity. Binary stars can either be distinguished optically (visual binaries) or by indirect techniques, such as
spectroscopy. If binaries happen to orbit in a plane containing our line of sight, they will
eclipse each other; these are called eclipsing binaries.
The components of binary star systems can exchange mass, bringing their
evolution to stages that single stars cannot attain. Examples of binaries are
Algol (an eclipsing binary),
Sirius, and
Cygnus X-1 (of which one member is probably a
black hole).
The Cat's Eye Nebula (NGC 6543) is a
planetary nebula in the constellation of
Draco. Structurally, it is one of the most complex nebulae known, with high-resolution
Hubble Space Telescope observations revealing remarkable structures such as knots, jets and sinewy arc-like features.
Modern studies reveal several mysteries. The intricacy of the structure may be caused in part by material ejected from a
binary central star, but as yet, there is no direct evidence that the central star has a companion. Also, measurements of chemical abundances reveal a large discrepancy between measurements done by two different methods, the cause of which is uncertain.
Comet Hyakutake (
Japanese: 百武彗星 Hyakutake suisei,
IPA[çakɯtakesɯiseː];
formally designatedC/1996 B2) is a
comet that was discovered in January 1996, and passed very close to the Earth in March of that year. It was dubbed The
Great Comet of 1996, and was one of the closest cometary approaches to the Earth in the previous 200 years, resulting in the comet appearing very bright in the night sky and being seen by a large number of people around the world. The comet temporarily upstaged the long-awaited
Comet Hale–Bopp, which was approaching the inner
Solar System at the time, although Hyakutake was at its brightest for only a few days.
Scientific observations of the comet led to several notable discoveries. Most surprising to cometary scientists was the discovery of
X-ray emission from the comet, the first time a comet had been found to be emitting X-rays. This emission is believed to be caused by ionised
solar wind particles interacting with neutral
atoms in the
coma of the comet. The
Ulysses spacecraft also unexpectedly crossed the comet's tail at a distance of more than
500 million km from the
nucleus, showing that Hyakutake had the longest tail yet known for a comet.
Hyakutake is a
long-period comet. Before its most recent passage through the Solar System, its orbital period was about 15,000 years, but the
gravitational influence of the
giant planets has now increased this to 72,000 years.