Advertisement.

EnchantedLearning.com is a user-supported site.
As a bonus, site members have access to a banner-ad-free version of the site, with print-friendly pages.
Click here to learn more.

ad
(Already a member? Click here.)


You might also like:
Astronomers-Zoom Astronomy GlossaryZoom Astronomy Glossary: AAfrican-American History: Black History MonthTHE EARTHToday's featured page: Beaver (Castor canadensis)


Table of Contents Enchanted Learning
All About Astronomy
Site Index
Our Solar System Stars Glossary Printables, Worksheets, and Activities
The Sun The Planets The Moon Asteroids Kuiper Belt Comets Meteors Astronomers

Astronomy Dictionary
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Click on an underlined word for more information on that subject.

J


JANSKY

The jansky (abbreviated Jy) is a unit of radio flux density (the rate of flow of radio waves); 1 Jy = 10-26 watts/m2/Hz. A typical radio source has a spectral flux density of roughly 1 Jy. The jansky was named to honor Karl Gothe Jansky who developed radio astronomy in 1932.

JANSKY, KARL

Karl Gothe Jansky (1905-1949) was an American radio engineer who pioneered and developed radio astronomy. In 1932, he detected the first radio waves from a cosmic source - in the central region of the Milky Way Galaxy. Jansky's work was continued by Grote Reber.


JANUS

Janus is one of the smaller of the 18 moons of Saturn. This heavily-cratered moon orbits at a mean distance of about 94,000 miles (151,472 km) and revolves around Saturn in about 18 hours. Janus has a diameter of about 185 miles. Janus shares an orbit with Epimetheus (they are only separated by about 50 kilometers (31 miles)). Once every four years they approach each other, exchange some momentum and switch orbits. This icy moon was discovered by the French astronomer Audouin Dollfus in 1966.


JEMISON, MAE C.

Mae C. Jemison (October 17, 1956 - ) was the first African-American woman in space. Dr. Jemison is a medical doctor and a surgeon, with engineering experience. She was accepted into NASA's astronaut program in 1987. She flew on the space shuttle Endeavor (STS-47, Spacelab-J) as the Mission Specialist; the mission lifted off on September 12, 1992 and landed on September 20, 1992. Dr. Jemison founded the International Science Camp in Chicago in 1994, a program designed to interest children in science and space.

JETS

Jets are blasts of particles that are emitted by an active galactic nucleus or a pulsar. Jets only occur in pairs, going in opposite directions.

JET STREAM

The jet stream is a high-speed wind that is usually found at high altitudes, between 25,000 and 45,000 feet (just below the tropopause). It is called the jet stream because the first people who encountered the jet stream were pilots who described it as though the wind was being propelled from a jet engine.

JEWEL BOX

The Jewel Box - NGC 4755 (also known as Kappa Crucis) is an open cluster of about 100 stars in the Southern Cross (a constellation in the Southern Hemisphere). Located near Beta Crucis, it was discovered by Abbe Lacaille when he was in South Africa from 1751 to 1752. This very young cluster is estimated to be under 10 million years old and is about 7500 light-years away from us.

JODRELL BANK

Jodrell Bank in northeastern Cheshire, England, is the location of a radio astronomy observatory, Nuffield Radio Astronomy Laboratories. The radio telescope's size is 250 ft (76 m).

JOVIAN

Jovian means of or relating to the planet Jupiter.

JOULE

A joule is the amount of work done by a force of one newton acting through one meter.

JPL

JPL stands for Jet Propulsion labratory. JPL is managed for NASA by the California Institute of Technology. JPL develops robotic devices for exploring the Solar System. JPL's main site is in the San Gabriel Mountains near Pasadena, California.

JUNO

Juno is a large asteroid, and one of the four brightest asteroids. It is about 240 km in diameter and its mass is roughly 2.0 x 1019 kg. It is about 2.7 AU from the Sun and takes 4.36 years to orbit the Sun once (its year). Juno was discovered by K. Harding in 1804; it was the third asteroid discovered.


JUPITER

Jupiter is the largest planet in our solar system and the fifth planet from the sun. This gas giant has a thick atmosphere, 17 moons, and a dark, barely-visible ring. Its most prominent features are bands across its latitudes and a great red spot (which is a storm).

Jy

Jy stands for "jansky (named to honor Karl Gothe Jansky who developed radio astronomy in 1932)". The jansky (abbreviated Jy) is a unit of radio flux density (the rate of flow of radio waves); 1 Jy = 10-26 watts/m2/Hz. A typical radio source has a spectral flux density of roughly 1 Jy.
Astronomy Dictionary
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Click on an underlined word for more information on that subject.
If the astronomy term you are looking for is not in the dictionary, please e-mail us.

Enchanted Learning®
Over 35,000 Web Pages
Sample Pages for Prospective Subscribers, or click below

Overview of Site
What's New
Enchanted Learning Home
Monthly Activity Calendar
Books to Print
Site Index

K-3
Crafts
K-3 Themes
Little Explorers
Picture dictionary
PreK/K Activities
Rebus Rhymes
Stories
Writing
Cloze Activities
Essay Topics
Newspaper
Writing Activities
Parts of Speech

Fiction
The Test of Time
iPhone app
TapQuiz Maps - free iPhone Geography Game

Biology
Animal Printouts
Biology Label Printouts
Biomes
Birds
Butterflies
Dinosaurs
Food Chain
Human Anatomy
Mammals
Plants
Rainforests
Sharks
Whales
Physical Sciences: K-12
Astronomy
The Earth
Geology
Hurricanes
Landforms
Oceans
Tsunami
Volcano
Languages
Dutch
French
German
Italian
Japanese (Romaji)
Portuguese
Spanish
Swedish
Geography/History
Explorers
Flags
Geography
Inventors
US History

Other Topics
Art and Artists
Calendars
College Finder
Crafts
Graphic Organizers
Label Me! Printouts
Math
Music
Word Wheels

Click to read our Privacy Policy

E-mail


Enchanted Learning Search

Search the Enchanted Learning website for:



Advertisement.



Advertisement.



Advertisement.


Copyright ©1999-2016 EnchantedLearning.com ------ How to cite a web page