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magazine of universe
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Supermassive black hole
Planetary center in Chile
Comet halley…
INDEX
ALMA; Atacama Large Millimeter/submillimeter Array
Centrurus A; the star with a Supermassive black hole at its core
Halley's Comet
The Atacama Large Millimeter/submillimeter Array (ALMA) will be unique in its ability to detect the signature of
protostellar collapse on solar-system size scales. We know that star formation involves gravitational collapse, but infall
motions forming a new star have yet to be found. To observe unambiguous evidence for collapse, we require high
spatial and velocity resolution (to map the velocity field across small structures) and high sensitivity (to take advantage
of the spatial and velocity resolution). Furthermore, this must be available at a wavelength at which the collapsing
object emits, and at which the surrounding material is transparent. Of current and planned instruments, only ALMA
has these characteristics.
Further, ALMA will be ideal for studying the
diversity of objects and physical processes
involved in star formation. Its excellent
mapping precision will allow astronomers to
study the characteristics of parent molecular
clouds from which stars form. Its sensitivity,
angular and velocity resolution, and high
frequency performance will allow the study of
smaller structures, including protostellar
fragments, outflows, and disks.
Wolf Simulation. A simulation of ALMA observations
at 950 GHz of a disc shows an embedded protoplanet of
Jupiter Mass around a 0.5 Solar Mass star.
D E T E C T I N G E X T R A S O L A R P L A N E T S W I T H A L M A
Detecting planets circling other
stars is a particularly difficult
task. In order to answer
fundamental questions about
planetary systems, such as their
origin, their evolution, and their
frequency in the Universe,
scientists need to find and study
many more extrasolar planets.
According to scientists, ALMA
will provide valuable information
about extrasolar planetary
systems at all stages of their
evolution.
Millimeter and submillimeter
waves occupy the portion of the
electromagnetic spectrum
between radio microwaves and
infrared waves. Telescopes for
observing at millimeter and
submillimeter wavelengths
utilize advanced electronic
equipment similar to that used
in radio telescopes observing at
longer wavelengths.
Millimeter/submillimeter-wave observations offer a
number of advantages in the search for extrasolar
planets. Multi-antenna millimeter/submillimeter-wave
telescope such as ALMA can provide much higher
resolving power, or ability to see fine detail, than
current optical or infrared telescopes. Observations in
millimeter and submillimeter wavelenghts would not be
degraded by interference from the "zodiacal light"
reflected by interplanetary dust, either in the extrasolar
system or our own solar system. Another important
advantage is that, at millimeter and submillimeter
wavelengths, the star's brightness poses less of a
problem for observers because, while it is still brighter
than a planet, the difference in brightness between the
two is far less. Because of the physical nature of the
objects themselves, protoplanets in different stages of
formation could readily be detected by ALMA.
Centaurus A is a prominent galaxy in the constellation of Centaurus. There is
considerable debate in the literature regarding the galaxy's fundamental properties such
as its Hubble type (lenticular galaxy or a giant elliptical galaxy) and distance (10-16
million light-years). 5128 is one of the closest radio galaxies to Earth, so its active galactic
nucleus has been extensively studied by professional astronomers. The galaxy is also the
fifth brightest in the sky, making it an ideal amateur astronomy target, although the
galaxy is only visible from low northern latitudes and the southern hemisphere.
The center of the galaxy contains a supermassive black hole weighing in at 55 million solar
masses, which ejects a relativistic jet that is responsible for emissions in the X-ray and
radio wavelengths. By taking radio observations of the jet separated by a decade,
astronomers have determined that the inner parts of the jet are moving at about one half
of the speed of light. X-rays are produced farther out as the jet collides with surrounding
gases resulting in the creation of highly energetic particles. The radio jets of Centaurus A
are over a million light years long.
Like other starburst galaxies, a collision is suspected to be responsible for the
intense burst of star formation. Spitzer Space Telescope studies have confirmed
that Centaurus A is colliding with and devouring a smaller spiral galaxy.
Halley's Comet or Comet Halley ,officially designated 1P/Halley, is the best-known of the
short-period comets and is visible from Earth every 75–76 years.
Halley was the first comet to be recognized as periodic. Until the Renaissance, the
philosophical consensus on the nature of comets, promoted by Aristotle, was that they
were disturbances in the Earth's atmosphere. This idea was disproved in 1577 by Tycho
Brahe, who used parallax measurements to show that comets must lie beyond the Moon.
Many were still unconvinced that comets actually orbited the Sun, and assumed they must
instead follow straight paths through the Solar System.
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