61. Curricular Resources In Astronomy Athena Curriculum space and astronomy Athena has used geophysical and This site contains information about SEDS and about space science in general for http://www.cln.org/subjects/astronomy_cur.html

Curricular Resources in Astronomy Here are a number of links to Internet sites which contain information and/or other links related to Astronomy. Please read our Amazing Space The Space Telescope Science Institute - the organization responsible for the scientific operation of the Hubble Space Telescope - hired teachers to develop a collection of K-12 web-based interactive astronomy lessons complete with student activities and teacher guides. There are several different units with topics on: Black Holes, Galaxies, Stars, the Solar System, Telescopes, Hubble Space Telescope. Ask an Expert: Astronomy CLN's "Ask an Expert" page has about 100 links to specialists in the field who can serve as a valuable source of curricular expertise for both students and teachers. Questions/answers on Astronomy may be found in our "All Subjects" section at the top of the page, the "Science" section, as well as the general "Reference" section. [An] Astronomy Course for Students Using the Internet An Internet-based course on astronomy that should be adaptable to most age and interest levels. Astronomy Education Resources Here's a meta-list of links to educational astronomy sites with descriptions.

62. General Astronomy And Space: MASPK Educational Resources Find out the astronomy Education resources linked in one place based on astronomysubjects. Get the information you need for studying in fine institutions http://www.maspk.com/Science/Astronomy/Astronomy1.html

MASPK Educational Resources Home Agriculture Arts Business ... Social Science General Organizations Journals History Planetariums ... Astronomy > General Astronomy and Space Here are few links about General Astronomy and Space. A New Universe to Explore: Careers in Astronomy As science professions go, astronomy is a relatively small field, with about 6,000 professional astronomers in North America. Because of its size, astronomers get to know and collaborate with many colleagues across the U.S. and around the world. This can lead to an advantageous dialogue among astronomers. http://www.aas.org/education/career.html Abrams Planetarium - Skywatcher's Diary Each month, the Department of Physics and Astronomy at Michigan State University makes the Skywatcher's Diary available over the Internet. The Skywatcher's Diary for February 2004 has been prepared by David Batch. Credit to the author and to Abrams Planetarium, Department of Physics and Astronomy at Michigan State University, and mention of our Sky Calendar, would be appreciated. http://www.pa.msu.edu/abrams/diary.html

63. Stanford SOLAR Center -- Other Resources space Educator s Handbook. Educational Resources in astronomy and Planetary Sciences.Education World (tm) Subjects Science astronomy general. http://solar-center.stanford.edu/resources.html

@import "/2005/ao.css"; Home SID Monitors Space Weather Student Science Fellow Program Solar Astronomy Resources Quick Jumps About the Sun Astronomy Education Science Information Infrastructure Hands On Universe ... Miscellaneous About the Sun With Peter and Paul Around the Galaxy The Sun A cute website for kids giving brief information about the Sun and planets. Homepage E ducation Astronomy Education NASA Online Interactive Projects SOHO Explore NASA Spacelink NASA Partners in Education. ... Public Outreach, Education, Teaching, and Reaching Youth (POETRY) site of the NASA IMAGE satellite project. Star Facts. Astronomical Records (Sac Peak). Kepler's Laws. The Galileo Project (Historical Astronomy about Galileo Galilei). ... "Bad" Astronomy The Science Information Infrastructure The Science Education Gate-way Web site Science Education Links from Syracuse University Center for Extreme Ultraviolet Astrophysics (CEA) Science Education Home Page. CEA Activity on Solar Rotation. The Hands On Universe Hands On Universe Main Page. Hands On Universe ISE Activities. Multicultural Astronomy and Astronomy History Ancient Cosmology Resource Site Center for Archaeoastronomy at University of Maryland Worldwide Ancient Astronomy.

64. General Interest Astronomy And Space Stuff general Interest astronomy and space Stuff. StarDate This short daily radioprogram about astronomy airs on several central Oklahoma radio stations (KGOU http://observatory.ou.edu/general.html

General Interest Astronomy and Space Stuff StarDate This short daily radio program about astronomy airs on several central Oklahoma radio stations (KGOU 106.3 FM at 6:57AM and 6:57PM, for one). I try to listen every day- it is usually interesting and informative. If you don't catch the radio broadcast, go to the web site to read the radio script. Astronomy Picture of the Day (APOD) . - Every day a different astronomy picture, some from groundbased telescopes, some from satellites, with informative captions and links to more information. You could learn a lot by looking at this every day! There is also an archive of past images for browsing. International Dark-Sky Association Astronomers! Take back the Night! The IDA promotes saving one of our most precious natural wonders - the dark night sky. The IDA has LOTS of info on good lighting practices (we can have a dark sky and light where needed at the same time), and lots of links to astronomy and lighting sites. One of my favorite items is the night-time image of the US. See if you can find your city! (click on "Links and Web Resources", then "IDA's DarkSky Finder" under "W3 Resources" near end of page). Consider joining the IDA. The Planetary Society.

65. Space & Astronomy Links general Interest. Thousands of space and astronomy sites can be found on theInternet. But, only our favourite sites have been listed below. http://www.bigsky.ab.ca/education/links.htm

Sponsored Links Affiliate Programs General Interest Thousands of space and astronomy sites can be found on the Internet. But, only our favourite sites have been listed below. All of these sites have high quality content and are recommended by us. If you know of an exceptional space or astronomy web site that we have overlooked, please let our webmaster know. Canadian Space Agency Heavens-Above Hubble Heritage Project Amazing Space ... Space Day NASA NASA maintains many web sites and our favourite sites have been listed below. If you know of a really good NASA web site that we have overlooked, please tell our webmaster about it. NASA SpaceKids NASA KIDS Eclipse Home Page ... Science @ NASA There are hundreds of observatories around the world, both big and small. The web sites listed below will allow you to learn more about some of the most famous observatories and telescopes in existence today. Please let our webmaster know about any site that you think should be added to our list. Canada France Hawaii Telescope Hubble Space Telescope United States Naval Observatory Green Bank Telescope ... W.M. Keck Observatory

66. Chan Space: Astronomy - General US Geological Survey astronomy and space Science. SkyView Virtual Observatory space Telescope Electronic Infromation Service http://ast.star.rl.ac.uk/sjchan/astro.html

List of Links Useful for Astronomy, Astrophysics and Space Science Networks in Astronomy and Astrophysics AstroWeb: Astronomy on the Internet Ftp-adresses for Astronomy and Astrophysics University College London 's List of Astronomical Information Network Resources for Astronomers Abstracts, Newsletters, Publications and Preprints ADS Abstract Service for Astronomy and Astrophysics (Havard abstract server) CERN Preprint Server (covers several topics, not only HELP) Connection to preprint server babbage.sissa.it List of Scientific Periodicals with Information of the Net Publication Resources of the CfA (Gopher) Star-Formation Newsletter by issue number Astronomy and Astrophyics Data Systems/Centers Atomic Data for Astrophysics (Department of Physics and Astronomy, University of Kentucky) Astronomical Data Center (ADC) CDS MIRROR SITE for the ADS Abstract Service Candian Astronomy Data Centre (CADC) X-ray Astronomy Data Center at MPE ISO Spectrometer Data Center at MPE The World-Wide Web Virtual Library: Astronomy and Astrophysics Astronomical Institutions, Observatories and Individuals Homepage of the American Astronomical Society (contains the AAS job register Homepage of the Royal Astronomica Society (contains the RAS job vacancies Homepage of the Astronomical Society of the Pacific European Southern Observatory(ESO) StarWolds/StarHeads - Index for Web Pages of Astronomical Institutions and Individuals Infrared Processing and Analysis Center (IPAC) Online Services Infrared Space Observatrory (ISO) National Aeronautics and Space Administration (NASA) ... Ames (and the

67. Chan Space: Astronomy - General ISO List of Links Useful for Infrared space Observatory (ISO) Users base atLaboratoy of InfraRed astronomy (LIRA), based at Kanagawa, Japan http://ast.star.rl.ac.uk/sjchan/iso/iso.html

List of Links Useful for Infrared Space Observatory (ISO) Users ISO Data (Science Support) Centers UK ISO Data Center based at Rutherford Appleton Laboratory ( RAL ), Chilton, Didcot, United Kingdom ISO LWS Consortium Server at QMW (Queen Mary and Westfield College, United Kingdom) LWS Principal Investigator: Prof. P. E. Clegg, QMW UKIDC - LWS main page LWS Project Office at RAL ESA ISO Data Center based at Villafranca Satellite Tracking Station ( VILSPA ), Villafranca, Madrid, Spain ISOPHOT Data Centre MPIA ) Heidelberg Germany ISO Spectrometer Data Centre ( ISOSDC MPE ), Garching, Germany Dutch ISO Data Analysis Centre ( DIDAC at the Space Research Organization Netherlands in Groningen, The Netherlands based at the Institut d' Astrophysique Spatiale ( IAS ),Orsay,France U.S. ISO Science Support Centre IPAC ), Pasadena, U.S.A. Japan ISO Support base at Laboratoy of InfraRed Astronomy (LIRA) , based at Kanagawa, Japan RAL SSTD Astrophysics Division UKIDC ... S.J.Chan

68. Astronomy And Astronautics My Pages general Links Sun Planets Extrasolar EarthBased astronomy MannedSpace Future Unmanned International. (This page is under construction.) http://www.io.com/~iareth/space.html

Astronomy and Astronautics My Pages General Links Extrasolar Earth-Based Astronomy ... International (This page is under construction.) My Astronomy Pages: Comet Information What is a Comet: A page I made in 1996 with information on the origin and nature of comets. What Does a Comet Look Like: Also from 1996, this page describes what a comet appears like to the naked eye or through a telescope eyepiece (as opposed to in an overexposed photograph) Comet Hyakutake: A collection of information and links on the Great Comet of 1996. Unfortunately, most information on this comet has expired from the internet. Comet Hale-Bopp: A collection of information and links on the Great Comet of 1997. Comet Photography Page: Contains scans of photographs and drawings I made in 1996 and 1997 of Comets Hyakutake and Hale-Bopp. Other The Galactic Center: An image I made of the Galactic Center in infrared using the SkyView Virtual Observatory at the Goddard Spaceflight Center. My Extensive List of Links: Image and Data Collections and General Information The undying mission to Jupiter and Saturn is now the Voyager Interstellar Mission and their web site on VRAPTOR has information about it and links to nearly every other major space site of interest. True to it's name, this is the best place to start an interstellar mission on the Internet.

69. Singapore Science Centre ScienceNet Astronomy Space Science astronomy space Science general astronomy. Q20337 , Does the EARTH grow bigger?Q20265 , What is the biggest star in the universe? http://www.science.edu.sg/ssc/scinet_browse.jsp?type=6&root=6&parent=6&cat=65

70. SPACE.com -- Dark Energy: Astronomers Still 'Clueless' About Mystery Force Pushi But dark energy is real or at least, a growing number of astronomers think it is . It does exactly what general relativity says it should do, http://www.space.com/scienceastronomy/astronomy/cosmic_darknrg_020115-1.html

advertisement Dark Energy: Astronomers Still 'Clueless' About Mystery Force Pushing Galaxies Apart By Andrew Chaikin posted: 07:00 am ET 15 January 2002 It sounds like something out of a Star Trek episode: Dark energy, a mysterious force that no one understands, is causing the universe to fly apart faster and faster. Only a few years ago, if you'd suggested something like that to astronomers, they would have told you to spend less time in front of the TV and more time in the "real" world. But dark energy is real or at least, a growing number of astronomers think it is. No one, however, can truly explain it. "Frankly, we just dont understand it," says Craig Hogan, an astronomer at the University of Washington at Seattle. "We know what its effects are," Hogan says, but as to the details of dark energy, "Were completely clueless about that. And everybodys clueless about it." Dark energy entered the astronomical scene in 1998, after two groups of astronomers made a survey of exploding stars, or supernovas, in a number of distant galaxies. These researchers found that the supernovas were dimmer than they should have been, and that meant they were farther away than they should have been. The only way for that to happen, the astronomers realized, was if the expansion of the universe had sped up at some time in the past. able > SCIENCE TUESDAY Visit SPACE.com to explore a new science feature each Tuesday.

71. SPACE.com -- Astronomy: Censored In Science Education Kids have a keen interest in astronomy, space sciences, and the search for The general earth and space science content areas are energy in the Earth http://www.space.com/searchforlife/seti_devore_astro_030403.html

advertisement Astronomy: Censored in Science Education By Edna DeVore Director of Education and Public Outreach posted: 07:00 am ET 03 April 2003 Teachers from across the nation converged on Philadelphia for the annual National Science Teachers Association's meeting, March 26 through March 30. NSTA convenes the largest meeting of science educators in the world, and this year more than 13,000 people attended. The meeting spanned the breadth of science: physics, chemistry, biology, earth and space sciences. The SETI Institute education team presented workshops and short courses, and participated in the earth and space science events that share lessons with teachers. We also had our exhibit in the trade show arena of the meeting, adjacent to NASA's exhibits. Throughout the five days, a steady stream of interested teachers talked with us about SETI and our science education materials at the booth. Like NASA, we were always busy interacting with the attendees. Over and over again, teachers remarked that their students are always asking about SETI and astronomy. Kids have a keen interest in astronomy, space sciences, and the search for extraterrestrial intelligence. What's out there? Are we alone? SETI THURSDAY Visit SPACE.com to explore a new SETI feature each Thursday.

72. Oracle Archive: Astronomy & Space This covers astronomy and space. This is for grades 6 to 12. Back one level To the Archive by scientist To the general archive Recent questions http://www.seps.org/oracle/oracle.archive/Earth_Science.Astronomy/

This covers astronomy and space. This is for grades 6 to 12. Please select one of the following choices: Back one level To the Archive by scientist To the general archive Recent questions and answers Sort by: Subject Author Date September 2005 12 entries August 2005 2 entries July 2005 8 entries June 2005 8 entries May 2005 16 entries April 2005 24 entries March 2005 14 entries February 2005 46 entries January 2005 6 entries December 2004 4 entries November 2004 34 entries October 2004 20 entries September 2004 46 entries August 2004 8 entries July 2004 8 entries June 2004 12 entries May 2004 44 entries April 2004 20 entries March 2004 6 entries February 2004 14 entries January 2004 24 entries December 2003 18 entries November 2003 34 entries October 2003 30 entries September 2003 40 entries August 2003 10 entries July 2003 2 entries June 2003 10 entries May 2003 20 entries April 2003 24 entries March 2003 30 entries February 2003 26 entries January 2003 32 entries December 2002 22 entries November 2002 50 entries October 2002 28 entries September 2002 30 entries August 2002 4 entries July 2002 6 entries June 2002 6 entries May 2002 38 entries April 2002 20 entries March 2002 24 entries February 2002 28 entries January 2002 24 entries December 2001 6 entries November 2001 14 entries October 2001 18 entries

73. Euro-Asian Association Of Teachers Of Astronomy, General Information general information. general information in Russian V Russian Olympiad onastronomy and space Physics, April 1998. III International astronomy Olympiad, http://www.issp.ac.ru/univer/astro/eaata/gene_e.html

74. Astronomy Web Links Of The C.S.I. Astrophysical Observatory astronomy Picture of the Day Hubble space Telescope Images Hubble Animations space Image general space Exploration. 30 Years After One Giant Leap http://supernova7.apsc.csi.cuny.edu/weblinks.html

NAVIGATION Faculty and Staff About the Observatory Observing Schedule Student Observing Requirement ... Links Astronomy Web Links International Astronomical Union Observatory Code #294 Astronomy Web Links Astronomy - General Astronomy Picture of the Day Students for the Exploration and Development of Space (SEDS) Physical Constants and Astronomical Data Griffith Observatory Star Award ... SPACEWATCH Astrophysics General Astrophysics Acceleration Astrophysics 29 Basic Physics of Orbits Bode's Law ... Yahoo! Astrophysics Go to TOP OF PAGE Acceleration in One Dimension Can Special Relativity Handle Accelerations? Classic Einstein Train Scenario ... Yahoo! Relativity Go to TOP OF PAGE Aberration of Light All About Spectra Atomic Hydrogen Spectra: Tools for Probing Galaxies ... Yahoo! Gamma Ray Observation Go to TOP OF PAGE Radio Astronomy AstroCapella Cosmic Radio Show Atlas of Double Radiosource Associated with Galactic Nucleus (DRAGN) Cambridge Low Frequency Synthesis Telescope (CLFST) Committee on Radio Astronomy Frequencies ... Yahoo! Radio Astronomy Go to TOP OF PAGE Department of Engineering Science and Physics at the College of Staten Island SETI Institute Space Telescope Science Institute Home Page Clubs and Organizations Rockland Astronomy Club Home Page United Astronomy Clubs of New Jersey, Inc.

75. Neat Sites In Astronomy, Etc Martin Zombeck s Handbook on space astronomy and Astrophysics The Periodic Table of general Astronomical Picture Sites. astronomy Picture of the Day http://homepages.wmich.edu/~korista/astro-etc.html

LINKS TO ASTRONOMY AND OTHER NEAT SITES... Some of my own web pages Homepage of Kirk Korista Links to the webpages of the astronomy courses I teach: Physics 104 Physics 106 Physics 325 What's astronomy all about and what do astronomers do? Careers in Astronomy from the American Astronomical Society FAQs about being an Astronomer 61 FAQs about a career in Astronomy Careers in Astronomy , from "Curious about Astronomy" Astronomical Societies American Astronomical Society Home Page The Astronomical Society of the Pacific International Astronomical Union Home Page The Royal Astronomical Society of Canada ... The American Association of Variable Star Observers The Space Telescope Science Institute (Hubble Space Telescope) Hubble Space Telescope's Homepage Hubble Site : News and Views from the Hubble Space Telescope The European Space Agency's homepage of the Hubble Space Telescope Hubble Space Telescope's Pictures and more The meaning behind color in astronomical images The Hubble Gallery Hubble Heritage Homepage - breath-taking images monthly! The Hubble Space Telescope Data Archive The Digital Sky Survey Where is the HST (and other astronomical orbiting observatories) right now?

76. Johnston's Archive--Astronomy And Space astronomy and space resources. astronomy information links. general.astronomy Picture of the Daydaily astronomy picture with explanation. http://www.johnstonsarchive.net/astro/

Johnston's Archive Astronomy and Space Asteroids with satellites A tenth planet Comparison of the largest TNOs Quick guide to the Mars opposition of October/November 2005 solar system information: Known populations of solar system objects Names of solar system objects and features Some named solar system objects Properties of the planets of the solar system ... Phobos information. Europa information and links. Named features on Europa Icosahedron map of Europa Investigation of evolution of orbits similar to that of (4179) Toutatis Information on Toutatis and asteroids near the 3:1 resonance with Jupiter ... Comets: graphs of orbital data solar system exploration: List of deep space probes (summary) List of deep space probes (listing) Space probe flybys: closest approach data List of space physics satellites ... List of space physics probes beyond Earth orbit stellar and extragalactic information: List of nearby stars (to 20 light years) List of known extrasolar planets and brown dwarfs Black holes part of a discussion of general relativity. List of black hole candidates Binary pulsar PSR 1913+16 List of known pulsars in binary systems Gamma ray bursts other material: Reading the Pioneer/Voyager pulsar map List of gravitational wave detectors Text of President George W. Bush's address on the space shuttle Columbia tragedy

77. Linking Library: Science(general): Astronomy/Space-travel The linking library is a humanities directory for the purpose of finding sitesin service of an alternative timeconsciousness. http://www.theorderoftime.com/cyber/to/s(g)-file/astron.sp.tr.html

LINKING LIBRARY SCIENCE (GENERAL) W W W - D I R E C T O R I E S_ WWW-directories (jumpboxes) Continental-national directories: ...Africa ...Asia ...Australia ...Europe ...Middle East ...N.America ...S.America International directories: A-B International directories: C-G International directories: H-M International directories: N-O International directories: P-T International directories: U-Z Dutch directories A-J Dutch directories K-Z Philosophy directories Religion directories Science directories (miscel.) A-D .Science directories (miscel.) E-L Science directories (miscel.) M-Z Social Sciences directories Spirituality directories _L I N K I N G - L I B R A R Y B U S I N E S S C H A T T I N G D I C T I O N A R I E S I N T E R N E T - S E R V I C E S L I T E R A T U R E L O C A L (E N S C H E D E - E.O.) M E D I A S C I E N C E ( G E N E R A L ) Astronomy/Space-travel Chemistry Geography History Law Mathematics Medical science Miscellaneous ...Directories / linkcollections ...Miscellaneous-general Philosophy ...Directories, linkcoll., bibliogr.. ...Journals / organizations ...Philosophy-general Physics Science Search Engine S P O R T S T I M E Linking Library: Home (index) Linking Bibliotheek: Thuis (index) Linking Library: Frames-English Linking Bibliotheek: Frames-Ned.

78. JAS: Establishment Of An Arab Union For Astronomy And Space Sciences Dr. Hamdi Murad (Assistant Secretary general, Jordanian Ministry of Endowments The Arab Union for astronomy and space Sciences (AUASS) formed a special http://www.jas.org.jo/union.html

The Arab Union for Astronomy and Space Sciences (AUASS) General View Arab Countries Represented in the Conference Higher Board Executive Council ... Photos of the Conference General View Arab Countries Represented in the Conference Palestine, Iraq, Syria, Saudi Arabia, Bahrain, Qatar, United Arab Emirates, Yemen, Egypt, Sudan, Libya, Tunis, Morocco, and Jordan. During the conference, Lebanon and Algeria apologized from attending the conference due to some urgent reasons. Higher Board Dr. Ahmad Ra'fat Ghadieh (Palestine). Dr. Hamid Mijuel Al-Naimiy (Iraq). Eng. Fayez Fawq Al-Adah (Syria). Dr. Moh'd Bakhit Al-Maleki (Saudi Arabia). Dr. Shawqi Al-Dallal (Bahrain). Sheikh Faisal Aal Thani (Qatar). Mr. Esam Al-Kasimi (United Arab Emirates, UAE). Mr. Mahmoud Al-Saghiri (Yemen). Dr. Moh'd Ahmad Suleiman (Egypt). Dr. Mu'awiya Shaddad (Sudan). Mr. Farhat Faraj Farhat (Libya). Mr. Fu'ad Anan (Tunis). Dr. Hamid Touma (Morocco). Eng. Khalil Konsul (Jordan). Photo for the Higher Board Counterclockwise, R to L: Dr. Mu'awiya Shaddad (Sudan), Mr. Farhat Faraj Farhat (Libya), Eng. Fayez Fawq Al-Adah (Syria), Dr. Hamid Touma (Morocco), Dr. Ahmad Ra'fat Ghadieh (Palestine), Dr. Moh'd Ahmad Suleiman (Egypt), Dr. Moh'd Bakhit Al-Maleki (Saudi Arabia), Ms. Nabilah and Ms. Luigia (UAE), Sheikh Faisal Aal Thani (Qatar), Eng. Khalil Konsul (Jordan), Mr. Fu'ad Anan (Tunis), Dr. Hamid Mijuel Al-Naimiy (Iraq), Mr. Mahmoud Al-Saghiri (Yemen), Dr. Shawqi Al-Dallal (Bahrain). Executive Council Eng. Khalil Konsul (Jordan) /

79. The DEEP BLACK The Universe Today general space and astronomy news. SkyViews Jay Respler sexcellent monthly observer s guide. ORGANIZATIONS. National space Science Data http://www.gregburch.net/space.html

Since childhood, I've been drawn to everything and anything connected to space and astronomy. Other boys memorized baseball statistics and idolized NFL quarterbacks; I knew the minute details of spacecraft construction and operation and looked up to the astronauts who were headed to the moon as the ultimate heroes. I'm just begining the process of rebuilding my space and astronomy page here now. I've transferred all the old links, so many of them are dead or out of date. GB 2002-09-13 From the Earth to the Moon, 2050 3d modelling and rendering I've done to illustrate my life-long dream. GENERAL SPACE AND ASTRONOMY LINKS Spaceflight Now : A very good space news and background portal Space Daily . Lots of good news and links. An excellent source of current events, developments and links. Space.com : Slick space news site. Good up-to-date news (but not a lot of depth and few outward-bound links). SpaceRef.com : Good news and background site. " NASA Today " is a good place to check current events in space exploration and observational astronomy. The site has links to other basic NASA web sites and is well worth regular visits. The Universe Today : General space and Astronomy news.

80. Chandra :: Resources :: Q&A: General Astronomy And Space Science Illustrations and other multimedia focusing on the Chandra mission, Xray astronomyand Chandra peopleas well as a glossary of terms, acronym guide, http://chandra.harvard.edu/resources/faq/astrophysics/astrophysics-21.html

Q: I just watched a program on space which quoted that for every grain of sand on the Earth there are a million stars in space. Is this true, and if so, how do we know this? A: We can assume that the program was referring to the number of stars in the observable universe not to be confused with the number of observable stars, since astronomers can observe many distant galaxies that contain billions of stars, but can't resolve the individual stars. From the brightness of the galaxy, and knowing the brightness of an average star at the distance of the galaxy, astronomers can estimate the number of stars in a galaxy. The number of galaxies can be estimated from deep surveys of selected regions of the sky. When these estimates are combined, the number of stars in the universe out to about 13 billion light years, assuming that the average star is about half as massive as the Sun, is in the range of a few hundred million trillion: say 300,000,000,000,000,000,000. A medium-sized grain of sand has a diameter of about 0.3 millimeters, so allowing for a little air space, a sand dune 20 kilometers square and 200 meters deep would contain about 300 million trillion sand grains, or about the same number of stars in the observable universe.

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