## Astronomy

What is what? Everything you always wanted to know.
 Home »

# Arc second

Arc second: Another measure of angular separation, - one sixtieth of an arc minute. (1/3600th of a degree.)
Astronomical unit (AU): A unit of distance equal to the average distance between the Earth and the Sun, or 149.6 million kilometers (93 million miles).
B ...

Arc second - A measure equal to one-sixtieth of an arc-minute.
Asterism - A group of stars that appear to make a recognizable shape, such as the Big Dipper.

Arc Second
A unit of angular measure consisting of 1/60th of an arc-minute. A dime seen from a distance of 2 miles transects 1 arc second. There are 3,600 arc-seconds in a one-degree angle. It is used to measure the separations of double stars or small deep-sky objects, like planetary nebulas.

ARC SECOND
An arc second is equal to one-sixtieth of an arc-minute.
...

arc second A unit of angular measure of which there are 60 in 1 arc minute (or therefore 3600 in 1 arc degree).
astronomy Branch of science dedicated to the study of everything in the universe that lies above Earth's atmosphere.

1 ~ = 0.0175 ÷ 3600 = 4.85 × 10-6 rad.
Since d = R/q, d = 1.496 × 1011 ÷ 4.85 × 10-6 = 3.09 × 1016 m
1 light year = 9.46 x 1015 m ...

One ~ is 1/60 of an arc minute and 1/3600 of an arc degree. The apparent size of a dime about 3.7 kilometers (2.3 miles) away would be an ~. The angular diameter of Jupiter varies from about 30 to 50 ~s, depending on its distance from Earth.
Astronomer ...

9. An ~ is _____ (give the fraction) of an arc minute. HINT
10. When the Sun, Earth, and Moon are positioned to form a right angle at Earth, the Moon is seen in the _____ phase. HINT
11. A _____ eclipse can be seen by about half of Earth at once.

Instead it is always measured in ~s (remember one ~ is 1/3600 of a degree, a very small angle indeed). We know that the size of the parallax shift is related to the distance of the star, so you can use the following relation ...

~ a tiny angle unit = 1/3600th of a degree = 1/60th of an arc minute. asteroid boulder to mountain-sized piece of rock remaining from the early solar system. The largest asteroid is only 1000 kilometers across but most are much smaller.

Arc minutes are further divided into ~s, such that there 60 x 60 or 3600 ~s per degree. So the moon's apparent size can also be expressed as 1/2 degree x 3600 = 1800 ~s.

parsec Unit of distance corresponding to the distance of a body whose parallax equals one ~. partial eclipse Pauli exclusion principle peculiar galaxy abnormally shaped galaxy that emits nonthermal radiation.

For example a 1 meter diameter optical telescope is two million times bigger than the wavelength of light observed giving it a resolution of a few ~s, whereas a radio telescope "dish" many times that size may, depending on the wavelength observed, ...

The nearest stars have an annual parallax of less than 1 ~. In contrast, the diameter of the Sun on the sky is 32 arc minutes, the diameter on the sky of Venus at inferior conjunction is 1 arc minute,2 the diameter on the sky of Jupiter at opposition is 47 ~s, ...

Due to the high spatial (1 ~) and temporal resolution (1-5sec), TRACE has been able to capture highly detailed images of coronal structures, whilst SOHO provides the global (lower resolution) picture of the Sun.

Generally credited to astronomer Herbert Hall Turner (1860-1930), the term "parsec" (pc) -- a contraction of "parallax second" -- is a unit of distance used by astronomers since at least the early 1900s, that is derived from a "parallax of one ~.

The resolving power of a telescope can be calculated with the following formula: Resolving power (in ~s) = 4.56 Ã- aperture of telescope (in inches). In metric units, this is: Resolving power (in ~s) = 116 Ã- aperture of telescope (in millimeters).

3 ~s. The brighter star, Hadar A, is a spectroscopic binary itself. Hadar A is composed of a pair of identical stars with an orbital period of 357 days. At least one of the stars is a Beta Cephei type variable, a star whose brightness varies as a result of the pulsations of its surface.

31 pc, which means that even the nearest star shows a parallax shift of less than one ~. Parallax measurements can be obtained out to distances of about 20 pc. Almost all the stars you see in the night sky are at greater distances than that.

The two stars are separated by 0.86 ~s corresponding to a distance of of 22 AU, that is, slightly more than the separation of the sun from Uranus. The stars revolve with a period of 88 years.
Other Designations For This Star
Flamsteed ...

By using the formula Couteau provides, all variables (ball bearing radius, distance between the lamps, distance from lamps to ball bearing, and distance from telescope objective to ball bearing) are used to define the separation of the artificial pair in ~s.

Due to its larger orbit there are times when Mars is very close to Earth and the angular diameter can be as large as 25 ~s.

Chandra has an angular resolution of 0.5 ~s, so about 10 years.
"It's Praxis, sir."
[...] science goodness: Neutron star racing across space Graphene may make for an efficient way to make salt water into fresh Nice way to explain the [...] ...

The nearest star will only move less than one ~. This is about one two thousandth (0.0005) of the Moon's diameter. This small change was measured near the end of the 19th century and we finally knew how far away are the nearest stars.

The field of view is usually specified as an angle that depends on the size of the sensor. For example, a lens or telescope of 500mm focal length will cover a field of view of 4 degrees, 17 arc minutes, 43 ~s by 2 degrees 51 arc minutes, ...

HETE-2 will be able to pinpoint the location of the burst to a circle of 10 ~s or about 1 / 200 the size of the Full Moon. This is around 10 times better than any previous detector.

The star with the largest known proper motion across the sky. It moves at a rate of about 10 ~s per year.
BARRED SPIRAL
A spiral galaxy in which the arms originate from the ends of linear extensions to the nucleus, rather than from the nucleus itself.

In medieval Islamic astronomy, the Zij-i Ilkhani compiled at the Maragheh observatory set the precession of the equinoxes at 51 ~s per annum, which is very close to the modern value of 50.2 ~s.

Superimposed on the 26,000-year precession is a small nodding motion with a period of 18.6 years and an amplitude of 9.2 ~s.

Many new stargazers have trouble understanding our reference to 'degrees', 'arc minutes', and '~s' when talking about the separation of celestial objects. So here's a primer on measuring angular distances.

A unit of angular measure equal to 60 arc minutes or 3600 ~s. One degree is equal to the diameter of two full Moons.
density
The amount of mass per unit of volume.

The rate at which a star moves across the sky. Measured in ~s per year.
Proton
A positively charged atomic particle contained in the nucleus of an atom. The nucleus of hydrogen atom.

050 ~s) third after Barnard's Star and Kapteyn's Star. In only 511 years it shifts its position by one degree. It's 28.8 light years away, and has a space velocity of 312 km/s. Its Epoch 2000 values are: right ascension 11h, 52m, 58.7s; declination +37 degrees, 43', 07".

"Calculations complied from these events have made it possible to determine the Sun's diameter to several hundredths of an ~." He follows up this data with: "Twenty years of data has shown us that the Sun may be shrinking." ...

In the area of astronomy, proper motion is the term used to describe a star's apparent movement across the celestial sphere, usually measured in ~s per year. The symbol for proper motion is the Greek letter μ - mu.

Hubble's Wide Field Planetary Camera 2 was used in October 1996 to undertake a sensitive search for the optical object, and found a stellar pinpoint of light within only 2 ~s (1/900th the diameter of the Moon) of the X-ray position.

Astrometry. The careful, precise measurement of astronomical objects, usually made with respect to standard catalogues of star positions. For comet orbit computations, astrometry good to 1" or 2" (1 or 2 ~s), or better, is the standard nowadays.

Two images of 2010 ST3 (circled in green) taken by PS1 about 15 minutes apart on the night of 16 September show the asteroid moving against the background field of stars and galaxies. Each image is about 100 ~s across. Image: PS1SC.

The closer a star is to us, the larger its angle of parallax will be. Astronomers have defined a standard unit of distance to be the parsec (pc). One parsec is the distance to a point in space that subtends a parallax angle of one ~. This produces the simple but effective relationship: ...

is should be visible in moderate or larger size telescopes near the border of the constellations Lepus and Columba. It will be a little easier to see in the southern hemisphere, where it will have an apparent movement of 50 ~s per minute, ...

A parsec is the length of the long leg of a right triangle, whose short leg is one astronomical unit when the angle between the Sun and the Earth, as seen from an object in space (a star for example), is one arcsecond The word parsec stands for "parallax of one ~" One kiloparsec (kpc), ...

Also, they are always within 11 ~s, or about 1/350 of a degree away from one another. Look for Sirius (it shouldn't be too hard) in the south/south west skies early in the evening. It will be the brightest object in the area.

Measured in ~s per year.
Proton
A positively charged atomic particle contained in the nucleus of an atom. The nucleus of hydrogen atom.
Proton-Proton Chain
A series of three nuclear reactions that build a helium atom by adding together protons. The main energy source in our sun.

See also: What is the meaning of Astro, Earth, Star, Sun, Astronomer?