Quickie Questions - Astronomy - Other

Date Answered Questioner (age, location) Question Answer
March 20, 2011frankI don't know what the "2012 riddle" is. I read that some people believe there will be a global transformation or catastrophe in 2012. Like many predictions, that one may or may not be true, but I find no scientific basis for believing it. Science is concerned with predictions that can be tested by experiment or observation.
February 21, 2011George(New York)What is the difference between dark matter and dark energy?Matter and energy are equivalent in the sense that either can be converted into the other, such that the total matter plus energy in the universe, M, never changes. "Dark energy" is a hypothetical energy whose existence would help explain the observed accelerating expansion of the universe. Dark energy is about 73% of M, but only 1 gram in a cube 50,000 kilometers wide. "Dark matter" is also inferred to exist to explain cosmological observations, but is about 23% of M, and more variable in density than is dark energy. Both things are called "dark" because only gravity can "see" them, not light or any other forces. [Sources: Wikipedia and recalled lectures.]
May 4, 2010marissa (P.a)how old is the delta aquarii star?Delta Aquarii belongs to the Ursa Major Group, an open cluster with stars that formed about 500 million years ago.
April 22, 2010gabby (california)who discovered the first nebula?I believe it was the Crab Nebula was before observed by John Bevis in 1731; it corresponds to a bright supernova recorded by Chinese and Arab astronomers in 1054. It was cataloged by Charles Messier in 1758 as M1.
April 20, 2010Zoe (Ilinois)What happens if you go in a black hole?From our web page Black Holes: What would it be like to enter a black hole? Not pleasant. First, as you approach the black hole the difference in the gravitaional pull on your head compared to your feet (known as tidal forces) would rip you apart. But suppose you survived that. Once you cross the event horizon there is no turning back. Then the only thing to do is avoid the black hole itself at all costs. If you run into that singularity it will crush your body right out of existence. If people from Earth were watching your journey into a black hole they would never see you cross the event horizon. Albert Einstein's theory of General Relativity says that as you approach a black hole your time slows down. The closer you get to the black hole the more you appear to be in slow motion as seen by Earth. Eventually you appear to be frozen in time as you cross the event horizon. You would notice nothing different whatsoever. If you were to change your mind right before crossing the event horizon and return to Earth you would find it in the very distant future. You've become a time traveler!
April 2, 2010Albie (Kerla/India)What is a Nebule? please explainA nebula (pural nebulae) is an interstellar cloud of dust, hydrogen gas, helium gas and plasma.
March 24, 2010mecca (California)ehat are facts about supergiantsSupergiants can have masses from 10 to 70 solar masses and brightness from 30 000 up to hundreds of thousands times the solar luminosity. Their sizes usually go from 30 to 500, or even in excess of 1000 solar radii. With relatively short lifespans (only 10 to 50 million years) are only observed in young cosmic structures such as open clusters, the arms of spiral galaxies, and in irregular galaxies. Some supergiants are unstable and form the very important Cepheid variables. In their final stages, supergiants may explode into supernovae.
March 19, 2010lee (hong kong)How do you measure the diameter of the star?There are several methods. One of the most important uses eclipses of binary star systems. By carefully examining the light curve, it is possible to determine how long it takes one star to pass in front of the other. This can be used to infer the sizes of the stars. This and other methods are described at the web page Measuring the Diameter of Stars.
January 25, 2010Debra (MD)Relative to the known size of the universe, what is north, south, east and west of the universe?To define cardinal directions a reference frame is needed. This means that cardinal compass directions, like latitude and longitude lines, are just an imaginary referents to define object locations. In other words, there is no intrinsic cardinal directions in space.
December 30, 2009Roshan (Delhi/India)how the astronomy beganSince the first humans! Humans have always been fascinated by the starry sky.
December 23, 2009Beronley (Canada)Is there another planet like earth? If so, when do you think you will find it? And when do you think you will prove if /mars had living beings on it?Although astronomers have been looking all around the universe for a long time, and still do, so far they haven't found a planet similar to our own.
December 23, 2009Malexa (Arizona)Other than our planets in the solar syatem, are their other planets that are being explored? I love science and wanted to find out more! Thank you, MalexaExoplanets, or planets outside our solar system, are being studied through remote observations. We are still far from being able to visit them.
December 22, 2009douglas (united states/CA)can there be another sun some were in another galaxy that we dont know ofAbsolutely! All the stars are suns! Just in our galaxy there are about 400 billion stars (very rough calculation).
October 6, 2009Narayanan (India)IS black hole the last form of a star?Is there any change of form for black hole again?Yes, Black Holes may form as the result of the collapse of a very massive star at its death, so massive that nothing could stop its gravitational collapse. All the matter of the star's core is crushed to an infinitely small point, a singularity.
August 18, 2009Gayathry (India)I heard that when Dark matter changes into dark energy,Universe expands.Now it is happening.Then if Dark energy changes into Dark matter will Universe contracts to a Singularity?Can we assume this as the end of the Universe?This topic is still being debated among the scientists. See the following pages for a good discussion: http://skyserver.sdss.org/dr1/en/astro/universe/universe.asp http://csep10.phys.utk.edu/astr162/lect/cosmology/expansion.html http://archive.ncsa.uiuc.edu/Cyberia/Cosmos/ExpandUni.html
August 12, 2009walter (texas)ARE THERE OTHER PLANETS INSTEAD OF THE PLANETS IN OUR SOLAR SYSTEM?Yes they are known as exoplanets, and as of today, 357 have been found. This NASA website have the updated information on this topic.
August 11, 2009oliver (usa)Do galaxies orbit a central mass, such as the earth orbits the sun? It seems very logical that galaxies would be orbiting a mass just as everything else has orbits.Some scientists believe that many if not most galaxies harbor suppermassive black holes in their cores. These black holes have gobbled so much matter that they have the mass of billions of suns. Visit our web page Black Holes for more information.
August 6, 2009Sam (SA)How are clusters and super-clusters formed?Extracted from Supercluster: Formation of superclusters may be the next stage in a process that is shaping and forming fundamental units in the universe. t is believed that the process began after the Big Bang, when matter in the universe expanded out rapidly. Some matter clumped together to form stars. Then gravity took over and the stars formed galaxies, then groups, then clusters and, now, superclusters.
July 28, 2009alexandra (los angeles)Are there other planets in the other galixis?As of today, 353 exoplanets (planets outside our solar system) have been found. This NASA website have all the information on this topic.
July 24, 2009Miguel (Puerto Rico)If the nebulae are regions that form stars from the remaining materials of dead stars, why the nebulae will not supposed to form new stars in the cosmological decades from 15 to 37 (Degenerate era)?When stellar evolution, the current Era, comes to an end, we enter the Degenerate Era, where most ordinary stars will have finished nucleosynthesis as stellar bodies. Lots of information about this topic can be found here.
July 22, 2009justice (kentucky)how much mass is missing in a galaxyThe first person to provide evidence and infer the existence of a phenomenon that has come to be called "dark matter" was Swiss astrophysicist Fritz Zwicky, of the California Institute of Technology in 1933.[8] He applied the virial theorem to the Coma cluster of galaxies and obtained evidence of unseen mass. Zwicky estimated the cluster's total mass based on the motions of galaxies near its edge and compared that estimate to one based on the number of galaxies and total brightness of the cluster. He found that there was about 400 times more estimated mass than was visually observable. The gravity of the visible galaxies in the cluster would be far too small for such fast orbits, so something extra was required. This is known as the "missing mass problem". Based on these conclusions, Zwicky inferred that there must be some non-visible form of matter which would provide enough of the mass and gravity to hold the cluster together. Extracted from Dark matter.
June 2, 2009Cara (U.S.A)Since our solar system is only one among millions, is it possible for there to be a planet similar to Earth? In the Bible, it only mentions God making Earth. So...?
P.S. I don't believe in the Big Bang Theory- God made everything!!
Yes, Earth-like planets have been found outside our system. See, for example, this article about the exoplanet Gliese 581d.
May 11, 2009Narayanan (INDIA)How dark matter & dark energy related to the expansion of universe ?In physical cosmology and astronomy, dark energy is a hypothetical form of energy that permeates all of space and tends to increase the rate of expansion of the universe. Dark matter, on the other hand, is hypothetical matter undetectable by its emitted radiation, but whose presence can be inferred from gravitational effects on visible matter.
April 27, 2009Joe (Ayrshire, Scotland)If the stars and galaxies are moving away from us, does that mean we are at the center of the universe? (which i very much doubt)No. Imagine a balloon being inflated. If we draw points on its surface with a marker, we will see that they get separated one from each other while the balloon is growing. A similar idea applies to an expanding universe.
April 21, 2009claire (MO)Has an undiscovered planet been mistaken as a star?Planets don't shine as stars do. They are so different that it is almost impossible to mistake them.
April 15, 2009morgan (united kingdoms)How often are stars born?Scientists use the concept of "star formation rate". In our galaxy, the Milky Way, the star formation rate is about 3 solar masses per year, in other words, three times the mass of the Sun's worth of star is produced each year. Keep in mind that the stars formed can either be more or less massive than the Sun, although less massive stars are more numerous.
March 25, 2009Jessica (Canada)How big is Kiepier Belt in kilometers?The Kuiper belt extends from the orbit of Neptune (at 30 AU) to approximately 55 AU from the Sun. Therefore, it covers 25 AU in a radial direction. 1 AU = 149 598 000 kilometers.
March 25, 2009muhammad (karnataka,india)by which instument that we know that the inside of sun is core?There are different methods to study the interior of a star. This website presents an interesant discussion on this topic.
March 25, 2009sammy (sc)if the earth has one sun,how many sun are there in the milk wayOur sun is just a common star. It has been calculated that there are maybe 400 billion stars in our galaxy.
March 25, 2009Carlos (Nj, USA)what causes different stars to appear in the sky at different times of the year?The combination of the rotation of our planet on its axis and its revolution around the Sun produces the ever changing sky.
March 25, 2009Adam (California)How many parsecs away from the Earth is the Oort cloud?The Oort cloud is a hypothetical cloud of comets which may lie roughly 50 000 AU (roughly a light-year) from the Sun.
March 24, 2009N KARTHEEK (INDIA)WHAT IS THE SHAPE OF OUR UNIVERSE?The answer to your question lies in the field of Cosmology. This short although interesting article will give you some answers.
March 19, 2009Jack (USA)Given the modern distance to M31 and Van Maanen's claim to have measured proper motions for objects in M31, why was his calculated speed(km/sec)unreasonable to have the proper Maanen motions?Van Maanen's calculations came in contradiction with Hubble's results. The Cepheid stars would have to move at speeds faster than that of light to satisfy the magnitude of the speed at which he calculated the nebulae to rotate. It is not known the source of van Maanen's calculation errors.
March 16, 2009wah (mas)what is black hole
what planet are rotae by side
Extracted from our web page Black Holes: Black Holes are theoretical objects. A black hole is an object which has such high gravitational pull that not even light can escape. Hence it is black. Which makes it pretty hard to observe directly. Black Holes may form as the result of the collapse of a very massive star at its death. Just as neutron stars form during a supernova explosion of a very massive star so do black holes. But in the black hole case the initial star was so massive that nothing could stop its gravitational collapse. All the matter of the star's core is crushed to an infinitely small point, a singularity.
March 10, 2009Bilal (Canada)Are there solar systems or even stars in intergallactic spce??NASA's Hubble Space Telescope has found stars in the dark emptiness of intergalactic space, more than 300,000 light-years (three Milky Way diameters) from the nearest big galaxy. Read the full articlehere.
February 17, 2009joanna (california)why did astronamers choose 32.6 as a distance to measure the brightness of the stars?Maybe because it makes sense from a trigonometrical point of view. 32.6 light years equals 10 parsecs, and the parsec is defined as the length of the adjacent side of an imaginary right triangle in space. The two dimensions that form this triangle are the parallax angle (defined as 1 arcsecond) and the opposite side (which is defined as 1 astronomical unit (AU), the distance from the Earth to the Sun). Given these two measurements, along with the rules of trigonometry, the length of the adjacent side (the parsec) can be found. See this page for a simple plot.
February 11, 2009Jacob (America)If the big bang was true, why are all the planets spinning in opposite directions? Since the supposed big bang started out as a spinning dot, why,according to the conservation of angular momentum, are all the planets, stars, and moons not spinning in the same direction?After the Big Bang there have been many other interactions among the celestial bodies. Stars and planets are created from a solar nebula which is perturbated by a super nova. Due to the sequencing of all these interactions it is not possible to apply the Conservation of Momentum (as you tried) to each particular element. However, the motion of all known galaxies supports the Big Bang idea. They are all moving away from each other.
February 9, 2009QAMARUL (MALAYSIA)IS THERE OTHER MORE PLANETS?There are other planets found outside our solar system. They are called exoplanets, and scientists continuos the search for new ones. This NASA website offers information on this topic.
February 9, 2009sreemanth (australia)Do Stars Twinkle At NightWe see the star twinnkling due to the presence of the atmosphere around our planet. This happens because we see them through thick layers of turbulent (moving) air in the Earth's atmosphere. This is called stellar scintillation.
February 8, 2009elena (madrid españa)¿de verdad nuestra galaxia se dirige a un abugero negro?Ha sido teorizado que puede existir un hueco (agujero) negro en el centro de nuestra galaxia, y se ha estimado que en unos 7 mil millones de años nuestra galaxia y la galaxia de Andrómeda van a chocar. Quizás de la unión de estas dos ideas proviene la based de tu pregunta.
February 6, 2009nicole (colorado,usa)formation of the solar system is in part due to the explosion of a nearby star. what is star the explosion called?This type of explosion is known as "supernova".
February 4, 2009KAJAL (KARNATAKA/INDIA)WHAT IS THE FORCE THAT KEEPS THA NEBULAS CLOSER TO FORM STARS?AND SIR WHY IS IT THAT EINSTIEN HAS USED THE VEOCITY OF LIGHT IN THE FORMULA E=mc2?PLEASE ANSWER MY QUESTIONS AS FAST AS POSSIBLE I'M VERY INTERESTED TO KNOW WHY??????????The basic force that keeps bodies together in celestial system is gravity. This applies to our solar system, our galaxy, etc.
January 29, 2009kajal (karnataka/INDIA)Sir i wanted to know how stars from distant places are able to send radio waves?are all stars able to send radio waves?please answer my question(i'm very sorry for asking more than 1 question)Radio waves, as any other electromagnetic radiation (including light), are commonly produced by stars. Transient radio emissions are not particularly unusual. They generally occur, at many different wavelengths, in conjunction with large releases of energy such as occur during deaths of stars. Binary systems featuring black holes or neutron stars emit radio and x-ray bursts, while supernovas emit over the entire electromagnetic spectrum. See more information here.
January 27, 2009kajal (karnataka/india)what is the force that makes the nebula come closer to form stars?Stars and planets form as a result of the gravitational collapse of accreting material. The main force is our well known gravity!
November 12, 2008christie (philippines)is there a planet discovered that we could survive?There is not known planet that have the same conditions of Earth. However, a number of distant planets have been found to rotate around stars similar to the Sun and roughly at the "right" distance.
November 11, 2008Jia (California)How does the position of a constellation change in the sky during the night?Constellations are formed by stars, and the apparent motion of a star depends on the location of the observer and the location of the star relative to Earth's rotation axis. Stars appear to travel in circles around the celestial sphere, near the celestial poles they travel in small circles; far from the celestial poles, they travel in large circles. Because all the stars are back to their original positions in 24 hrs., it is posible to calculate the apparent motion of a particular constellation per hour.
November 5, 2008abigail (malaysia)"other than the Milky Way and inside of it ,what things are there outside the Milky Way ?"Other galaxies and Dark Holes, dark matter and clusters, etc.
November 4, 2008bernadette (united kingdom)why are we seeing stars as they were in the past?Because they are so far away that the light from them reaches our planet way long after they left the stars. For example, Proxima Centauri is "only" 4.2 light-years distant fron our system. This means that it takes 4.2 years for the light leaving Proxima Centauri to reach our system.
November 4, 2008kayla (new zealand)How is the Sun different from all the planets/what makes it unique?Essentially, the Sun is a star, not a planet. Stars are luminous celestial bodies, made up of plasma (particularly hydrogen and helium). Planets rotate around a star.
September 25, 2008SHASHWAT (INDIA)WHICH IS THE FARTHEST POINT IN UNIVERSE KNOWN BY HUMANS?Extracted from "Quasars." McGraw Hill Encyclopedia of Science and Technology. 14 1997: 713: "… their red shifts would ambiguously show them (quasars) to be the most distant known objects in the universe, ranging up to about 1010 light-years away."
September 25, 2008Vanessa (California, U.S.A.)What is the name of the star viewed 6 A.D. at Christ's birth?There is no final agreement, but this web page offers an interesting discussion on this topic.
September 18, 2008fara (malaysia)what is the different between star and comet?A star is a massive, luminous and hot body of plasma. The nearest star to Earth is the Sun. A comet is a relatively small extraterrestrial body consisting of a frozen mass that travels around the sun in a highly elliptical orbit
September 17, 2008cya (india)if universe is expanding so why isn't the earth and other planets expand in it?Our galaxy is also moving away, and along it our solar system and planet.
September 12, 2008Zita (Serbia)Are the supernova explosions common? If they are... Is there some way we can find out when its going to happen and see one of them?? Or a program like Stellarium can show it to me? (still: if they are :))No, supernovas, one of the most expectacular phenomena in the Universe are not easily visible. It has been calculated that they occur with certain frequency, but not always at our reach.
September 12, 2008cya (india)why do most of the objects take a spherical shape in space?Celestial objects are round due to their own gravity force. An object's gravity tries to pull all of its material as close to its center as it can. A sphere is the best shape for this because every point on a sphere's surface is as close to the center of the object as any other point on the sphere's surface.
September 10, 2008koli (nigeria)explain the law of plantetary motion stated by johannes kepplerKeppler's Laws describe the motions of objects around the Sun. In their more simple form they can be stated as: Kepler's elliptical orbit law: The planets orbit the sun in elliptical orbits with the sun at one focus. Kepler's equal-area law: The line connecting a planet to the sun sweeps out equal areas in equal amounts of time. Kepler's law of periods: The time required for a planet to orbit the sun is proportional to the long axis of the ellipse raised to the 3/2 power. The constant of proportionality is the same for all the planets.
September 10, 2008ndoma koli (calabar nigeria)explain the law of plantetary motion stated by johannes kepplerKeppler's Laws describe the motions of objects around the Sun. In their more simple form they can be stated as: Kepler's elliptical orbit law: The planets orbit the sun in elliptical orbits with the sun at one focus. Kepler's equal-area law: The line connecting a planet to the sun sweeps out equal areas in equal amounts of time. Kepler's law of periods: The time required for a planet to orbit the sun is proportional to the long axis of the ellipse raised to the 3/2 power. The constant of proportionality is the same for all the planets.
September 10, 2008jessica (washington USA)could you please tell me what a solar nebula is?Scientists believe that the solar system was formed when a cloud of gas and dust in space was disturbed, maybe by the explosion of a nearby star. This explosion made waves in space which squeezed the cloud of gas and dust. Squeezing made the cloud start to collapse, as gravity pulled the gas and dust together, forming a solar nebula.
September 9, 2008jimmy (united kingdom)how many star is there in spaceThat is a question that has fascinated scientist, poets and lovers all along history. And there is not a unique and exact answer to it! A rough calculation states that if we take galaxies as the small representative volumes for the Universe, and assuming that there are something like 1011 to 1012 stars in our galaxy, and that there are perhaps something like 1011 or 1012 galaxies, we get something like 1022 to 1024 stars in the Universe.
September 9, 2008kenneth (louisiana)If the universe is constantly moving outward evenly why is in a couple billion years the andromeda galaxy going to collide with the milky way galaxy?Galaxies and other cosmic objects have been influenced by each other through gravitational forces, energy waves (due, for instance, to a super nova), etc. These interactions could had affected their motions taking them to crossing paths. PLease, visit this site for a very nice animation.
September 3, 2008priyanka (NEPAL/kathmandu)What is the greatest achievement in the asronomy till now?In my personal opinion the greatest achievement in astronomy is the realization of that earth is NOT the center of the universe. Or wait, maybe the Big Bang theory? I am not sure, but in any case I would include these two.
August 21, 2008Ian (Canada)What would happen if the mass of all the matter in a blackhole's 'horizon' exceeded that of it's olber horizon, being the matter in the barrier of sight based on how eventually spacetime moves faster than the speed of light.The mass compressed in a black hole is huge, but with an extremely high density, which is only possible when concentrated in a very small volume. This somehow contradicts the idea of the mass reaching the olber horizon.
August 14, 2008Bethany (Kentucky)When will there be a comet on Earth?As far as scientists know, none of the known asteroids or comets is on a collision course with Earth. However, there surely are other that we still don't know.
July 1, 2008Scott (Iowa)I found your previous answer about how fast the earth is moving. This is great considered relative to the sun. But could you expand by helping me understand how fast the earth is moving relative to the galaxy and relative to the rest of the universe?The Sun, and the whole Solar System, takes about 225–250 million years to complete one orbit of the galaxy (a galactic year). Considering the hypothetical value of the Solar System distance from the Galactic Center of 7.62±0.32 kpc (1 kpc equals approximately 3,262 lightyears), the orbital speed of the Solar System about the center of the Galaxy is approximately 220 km/s.
June 17, 2008Valerie (Florida USA)Are all stars sunsEssentially yes. Our Sun is just an average star.
June 16, 2008Eleanor (Australia)I am doing an assignment for science on astronomy.....and i cant find anything about the Binary star on the internet! So I was wondering can u please send be some information on the binary star? thanks for your help :)Most stars are members of multiple-star systems. Some stars are members of close binary systems where material from one star swirls around the other in an accretion disk. More information at NASA.
June 16, 2008Eleanor Williamson (Australia)I am doing an assignment for science on astronomy.....and i cant find anything about the Binary star on the internet! So I was wondering can u please send be some information on the binary star? thanks for your help :)Most stars are members of multiple-star systems. Some stars are members of close binary systems where material from one star swirls around the other in an accretion disk. More information at NASA.
May 12, 2008bwhygles (New Mexico)Why looking at an object which is 15 billion light years away also means you are looking at the way that object looked 15 billion years ago.The answer resides on the definition of light year. A light year is the distance travelled by light in one year (9.4607x 1012 km). If an object is 1 light year away from us, the light arriving to earth will have taken a full year travelling, so we would see the object as it was a year ago.
May 2, 2008Chris (florida, U.S.A.)If a spacecraft could be built to travel at light speed, wouldn't it be constantly colliding with all sorts of terrestrial bodies it would encounter in such a short space of time? (Or could Lt. Sulu somehow steer around them?)IF it were possible, it would be extremely safe, because the rest of the (non electromagnetic) universe moves at much lower speed, and a safe path would be very easy to calculate.
April 30, 2008jules (philippines)if space is a vacuum.... and refering to the law of... ( i forgot ) which states that an object at rest will remain at rest unless it is acted uppon by an external force... so.. this should apply to a moving object only it need an external force to stop that object...thinking that this object is energy... if a star explodes... shouldnt that energy reach us if nothing is around to stop it? even if its billions of light years away? since space is a vacuum...Yes, if the star is in what is known as "Observable Universe" which has radius equal to the lifetime of the Universe. Objects more than about 13.7 thousand million years old (the latest figure) are too far away for their light ever to reach us. More information about this topic can be found here.
April 29, 2008carrie (illionis/usa)should we be worried about the winter solstice in 2012.What will happen on that date.Not really, it will be just another astronomical event without further consequences.
April 28, 2008Lisa (Canada)Why is it important for scientists to map the space?Through the mapping and observation of the space we can learn much about our own planet, solar system, and galaxy evolution, as well as about other systems and the universe in general.
April 28, 2008Gary (California)As aperture increases, the Airy disk gets smaller and hence a larger lens has greater resolving power. However the Airy disk is always the same size for a given aperture at a given wavelength. If this is true, My Question is: Why do double star images (examples; Alpha Ursa minor and Beta Orion) under high magnification appear to be of different sizes according to their magnitude? Is there a relationship between the size of the Airy disk and the magnitude of the star?The Airy disk is an optical phenomenon derived from the diffraction of light. I don't believe its size is related with the magnitude of the star.
April 21, 2008Mike (Wisconsin)On my science homework, i got recommended to this site. What is the date for the start of "Modern Astronomy?"There are two main events that brought astronomy to the state of modern science: the introduction of the heliocentric (Sun in the center) system, and the invention of the telescope around 1600.
April 21, 2008Mike (Wisconsin)On my science homework, i got recommended to this site. What is the date for the start of "Modern Astronamy?"There are two main events that brought astronomy to the state of modern science: the introduction of the heliocentric (Sun in the center) system, and the invention of the telescope around 1600.
April 9, 2008John (Nv.,U.S.A.)If "dark matter" is pushing all galexies away from each other how is it we are told that andrdomeda and the milky way are on a collision course?The Andromeda and the Milky Way galaxies are part of the Local Group, a group of over 35 galaxies, with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy. because they are so "close" (from a galactical point of view) the gravitational force between them plays an important role, which in no way contradicts the expansion of the universe!
April 9, 2008John S. Hale (Nv.,U.S.A.)If "dark matter" is pushing all galexies away from each other how is it we are told that andrdomeda and the milky way are on a collision course?The Andromeda and the Milky Way galaxies are part of the Local Group, a group of over 35 galaxies, with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy. because they are so "close" (from a galactical point of view) the gravitational force between them plays an important role, which in no way contradicts the expansion of the universe!
April 9, 2008Brady (Canada)How much would a Supernova destroy?Supernovae are one of the most energetic explosions in nature, making them like a 1028 megaton bomb (i.e., a few octillion nuclear warheads). More information can be fond at NASA_Supernovae.
April 3, 2008miley (in north america)what is the distance from the sun from the milky way galaxy?Zero!, we are part of the Milky Way galaxy!
March 28, 2008rr (usa)what is aquasarA Quasar (QUASi-stellAR radio source) is an extremely bright and distant active galactic nucleus.
March 25, 2008Ramanan (Germany)Is Ophiuchus a valid zodiac sign, and if there is a false account of the zodiac?The Zodiac describes an annual cycle of twelve stations along the ecliptic, the apparent path of the sun across the heavens through the constellations. These constellations are: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces.
March 24, 2008Xie (San Francisco)Where is Earth located?Earth is the third planet from the Sun in the Solar System, which is located in the Orion Arm of our galaxy, the Milky Way. The Milky Way is part of the Local Group (group of galaxies close together), which in turn is part of the Virgo Supercluster (a supercluster is a group of galaxies held together by gravity).
March 21, 2008Carla (Maryland)Would the universe still exist, without light?It would, but we wouldn't have any information about it!
March 21, 2008Carla Chase (Maryland)Would the universe still exist, without light?It would, but we wouldn't have any information about it!
March 21, 2008Rosalind (Maryland/USA)Do we, Earth, have a finite or definable limited view of the Universe? To clarify: Does our position in the Universe and taking other objects around us, possibly blocking stellar phenomena, mean our view, though vast, to put it mildly, is still limited. To further clarify: If we lived in another part of the galaxy would our view be different, not totally but some increases or decreases in viewer rangeability?I would agree with you (again). Different positions in the Universe would offer different views.
March 3, 20089th grade D-class CNITV (Romania)Why is there more matter than antimatter in our region of the Universe?The Big Bang Theory suggests that matter and antimatter should have been produced in the same amount. Under the extremely dense conditions of the Big bang, all matter and antimatter should have been mutually destroyed. But this didn't happen, as the galaxies and all the matter in the universe prove. To explain this phenomenon, a new theory, known as CP-violation, has been developed. This theory proposes that nearly all the matter and antimatter would have been annihilated in the Big Bang, but one in a billion particles of matter (and none of antimatter) would have survived. This theory is now being extensively and intensively tested by many groups around the world.
An Eart-like planet has been found at merely 20 light years away.The new planet, which orbits a small, red star called Gliese 581, is about one-and-a-half times the diameter of the Earth, and has a substantial atmosphere and may be covered with large amounts of water. So far there is no evidence of life there.
February 12, 2008Nathan (Alabama,USA)If the sun is in space then why is it dark up there.The answer to your very good question excedes this space. Please, visit here for a comprehensive answer.
February 8, 2008Emil (Denmark)What is the difference between a messier objekt and a ngcMessier objects are a set of astronomical objects catalogued by French astronomer Charles Messier in his catalogue of Nebulae and Star Clusters first published in 1774. The first edition of the Messier catalogue covered 45 objects numbered M1 to M45. The total list consists of 110 objects, ranging from M1 to M110. A new catalogue was compiled in the 1880s by J. L. E. Dreyer using observations mostly from William Herschel, and later expanded to include two Index Catalogues (IC I & IC II), adding nearly 5,000 objects. The New General Catalogue (NGC) is the best-known catalogue of deep sky objects in amateur astronomy. It contains nearly 8,000 objects, known as the NGC objects.
February 7, 2008natalie (california, US)When a star dies, what is the size and mass. And what is the nebula?The mass and size of a dead star depend on what type of stars it was. Nebula is a cloud of gas and dust in space.
February 6, 2008Sidra (Canada)Do other stars have planets around them?(please i really need to know)Yes, more than 200 exoplanets (planets outside the solar system) have been found around other stars. For example, a new planet known as Gliese 581c , orbits a small red star called Gliese 581.
February 6, 2008 Has anyone see the Oort Cloud?There is no confirmed direct observation of the Oort cloud. However, there seem to be a consensus among astronomers which believe that all long period comets entering the inner solar system come from the Oort cloud.
January 31, 2008ashontae(paterson new jersy)what is an orbit?One of the common definition of orbit is "the (usually elliptical) path described by one celestial body in its revolution about another".
January 3, 2008Tage (Sweden)In what a constellation can I find the following object, that I found for some days ago in Google Earth's Sky webb, but have had to loose that place and constellation, please help me if possible.
It is about: Gravitationally Lensed Quasar in Galaxy Cluster SDSS J1004 + 4112
Maybe the news center of Hubblesite can help you.
December 21, 2007Daphne ( Tamilnadu,India.)Is it possible for man to make discoveries at other galaxies?How?Yes, scientists have developed methods to observe very far objects. A good example is the recent discovery of an Earth-like exoplanetknown as Gliese 581 C. This article describes the planet.
December 19, 2007slade (alabama/usa)is the planet earth inside the milkyway? in other words do we live inside the milkyway?Yes! Our solar system is just a small part of the Milky Way.
December 18, 2007nur (malaysia)Can you explain about the new planet which is 120 trilion miles away?The new planet, kmown as Gliese 581c is probably more than 1.5 times the diameter of Earth and five times heavier. It is just 7 million miles from its home star but is not incinerated this is star is a red dwarf, only about one one-hundredth as bright as the sun.
October 18, 2007Maha (Pakistan)Why stars cannot see in day time?They are still there, in the shy, but the Sun light is too intense and we van not see them.
October 16, 2007Ray (Long Island-New York-USA)What is a magnatarAssuming that your question is about a MAGNETAR: A MAGNETAR is a neutron star with an extremely powerful magnetic field, the decay of which powers the emission of copious amounts of high-energy.
September 25, 2007vibhav (u.p./ India)Why do planets revolve in elliptical orbits rather than in circular orbits?The short answer is that the orbits are dominated by the combination of two forces, gravity, pulling to the center and inertia trying to keep the motion on a straight line. Depending on the magnitudes of these two forces, the orbit will be more or less elliptical.
September 19, 2007Matt Larsen I was watching a creation movie the other day, and it said that cloud and dust came together and created the earth or something like that and what i want to know is what created the cloud and dust? and if there was something that created it what created that?Cosmic dust is a type of dust composed of particles in space which are a few molecules to 0.1 mm in size. Cosmic dust can be further distinguished by its astronomical location; for example: intergalactic dust, interstellar dust, circumplanetary dust, dust clouds around other stars, and the major interplanetary dust components to our own zodiacal dust complex (seen in visible light as the zodiacal light): Comet dust, asteroidal dust plus some of the less significant contributors: Kuiper belt dust, interstellar dust passing through our solar system, and beta meteoroids. Extracted from Cosmic Dust.
September 18, 2007Jonathan (Singapore)What is the composition of the atmosphere of Gliese 581c?Although the possibility that Gliese 581c possess water and an atmosphere theoretically exists, there is not (so far) hard evidence of neither.
August 21, 2007Aheli (India)If light is not made of matter, how can gravity effect it? How can it be sucked into black holes if it has no mass?Actually, from Einstein's general theory of relativity, the mass of the photon isn't attracted by the gravity of a black hole, rather, the black hole's mass distorts space and the photon's path changes because the space is curved.
July 26, 2007ssvnissvni (india)how do stars stay in the air without any support ?All celestial bodies are in motion. They are interacting with each other through a gravitational field, the same gravity that keeps us on the surface of our planet.
July 26, 2007maha ( andhra predesh / india)what is a night sky? can you explain?Night sky refers to the view of the sky, with all the stars and constellations, during night conditions. During the day, the bright Sun don't let us see any other celestial body, except, sometimes, the moon.
July 25, 2007Corrie (Toronto, ON Canada)Is the star Arcturus sometimes misnamed as the planet Venus, as they are similiar in colour to our eyes?This confusion shouldn't take long to clarify, planets and stars move differently in our sky.
July 25, 2007maha (india)is there any other solar system found yet ?There are not many solar systems known (here an article about such a discovery), but with the improvements of observation techniques, new systems will certainly be discovered.
July 25, 2007maha (india)is there any other solar system found yet ?There are not many solar systems known (SETI@home.
July 11, 2007sherianne (singapore)Is there such a moon that orbits a gas giant that is called 'Blue Moon',which is potentially habitableThese concepts appeared in a two-part television broadcast called Alien Worlds, aired in the UK by Channel 4. Channel 4 has also released a DVD of the programme. The show was also aired on the National Geographic Channel as Extraterrestrial. The first programme in the series focused on Aurelia, a hypothetical Earth-sized extrasolar planet orbiting a red dwarf star in our local area of the milky way. This fictional world might resemble the recently discovered real exoplanet Gliese 581 c. The second focuses on a moon called Blue Moon, which orbits an enormous gas giant that is itself orbiting a binary star system. The show blurred the lines between science fiction and science fact. Extracted from Wiki-Aurelia and Blue Moon.
July 3, 2007Emili (Illionis/United States of America)PLEASE answer by May 15!: What happens to stars in the day? Where do they go?? Why can't we see them??The don't go anywhere, they are still there, but we can't see them because the light of the Sun.
May 21, 2007Kristen (us michigan)WHO DISCOVERED THAT THERE IS BACKGROUND RADIATION LEFT OVER FROM SOME SORT OF EXPLOSION IN SPACE?The cosmic microwave background was initially predicted in 1948 by George Gamow and Ralph Alpher, and by Alpher and Robert Herman. It was in 1964 that the first published recognition of the CMB radiation as a detectable phenomenon appeared in a brief paper by Soviet astrophysicists A. G. Doroshkevich and Igor Novikov.
March 31, 2007Cara (france)Planets and stars both look like bright dots in the sky, What difference is there in the way they send us light?stars produce their own emmision, including light, planets and moons reflect the light of the stars.
February 12, 2007kalyan (india)stars twinkle, from wherever we see them,i am sure ! why ?Stars twinkle (when seen from the Earth's surface) because we are viewing them through thick layers of moving air in the Earth's atmosphere. The scientific name for this phenomenon is stellar scintillation.
January 17, 2007kuulei (Hawaii/ Waialua)What started our Universe?The Big Bang is the prevailing scientific theory about the origin of the universe. According to the theory, the universe was created (between 10 and 20 billion years ago) from a cosmic explosion that threw matter in all directions.
December 11, 2006Sam (Kentucky/United States)What is the big Bang?The Big Bang is the prevailing scientific theory about the origin of the universe. According to the theory, the universe was created (10 billion and 20 billion years ago) from a cosmic explosion that threw matter in all directions.
December 1, 2006Brianna (Tenness)What is Cosmic microwave background radiationThe cosmic microwave background radiation is a form of electromagnetic radiation discovered in 1965 that fills the entire universe. It is also called the 3 Degree Kelvin Background Radiation, because this radiation is essentially a black body with temperature slightly less than 3 degrees Kelvin, which lies around the microwave portion of the spectrum.
March 7, 2001Maria (Colorado, USA)What is the difference between an astronomical unit and a light year?The astronomical unit (AU) and light year are ways to measure really long distances. But, they are different measurements. It'd be like saying what's the difference between a mile and an inch? They are just defined as different amounts.
A light year is the distance light travels in one year. Since light travels at the speed of 186,000 miles per second, that means that in one year, light travels a distance of approximately 5,870,000,000,000 miles.
An AU is defined as the distance between the Earth and the Sun, which is about 93 million miles.
May 10, 2000J.D. (CA, USA)Is the tempeture of space absolute 0?Actually, space is a little warmer than that. Absolute zero is also known as 0 degress Kelvin, or -273 degrees Celcius.

The coldest parts of space reach the temperature of 3 degrees Kelvin, or -270 degrees Celcius. This is very, very close to absolute zero, but not quite there!

In reality, nothing can actually reach absolute zero. But no one wants me to go into that theory...

June 10, 1999Jeff (British Columbia)Have any other solar systems been discovered?Yes, several other planetary systems have been discovered. The first multi-planet system other than our own was discovered quite recently. Check it out on our headline universe page.
May 5, 1999Brad (Texas, USA)What is the name of the planet they have spotted in the galaxy outside of ours? How far away are to discovering more planets outside our solar system like these?A number of planets have been discovered in other solar systems. At least two, orbiting stars in Virgo and Ursa Major, are in orbits that might allow some liquid water to exist. That brings up the question of life existing on those planets. Details have appeared in the popular press and in scientific journals.
March 29, 1999Eileen (Illinois, USA)What is 'Eagle Nebula'?The Eagle Nebula is a young star cluster surrounded by a cloud of gas produced by the star formation. Here is a picture of it!
October 28, 1998Hugo (Texas, USA)Where was water detected (if any) out of our solar system ?We do not have instruments strong enough to detect water out of our solar system. It was only just recently that we discovered the presence of water on our moon!
September 2, 1998Steve (Manitoba, Canada)What is the temperature in space...what is the concept of equilibrum-state temperature? Since there is no medium for the transfer of heat, how can satellites maintain there interior temperature?The temperature in deep space is 3 degrees Kelvin, or -270 degrees Celsius. Within the solar system, the temperature depends on how close the object is to a radiating object such as the sun. Near the sun, of course, the temperature can be very high. There are three methods of heat transfer: conduction, convection, and radiation. The first two require matter as the transporting agent. In space, which is essentially a vacuum, radiation is the method of heat transfer. This radiation comes in the for m of visible light, infrared, ultraviolet, x-, and gamma-rays. In order to maintain a consistant temperature in a satellite, an equal amount of radiation must be released as is gained. Satellites have sheilds which adjust the amount of radiation is abso rbed or released to keep the satellite at a steady temperature.
August 20, 1998Adam (Minnesota, USA)If a black hole can harness light, and you can travel on air why can't you float or travel on light if light is some sort of matter?The thing about light is that it is not really matter. Light is made of photons. Photons are thought of as massless. Since mass can be converted into energy, you can think of a photon as an object with all of its mass converted to energy. So, alth ough a black hole exerts a tremendous fource and can pull light into itself, we humans don't have power like that. We don't really have much of an effect on the way light moves.
June 8, 1998Jim (North Carolina, USA)I would like to know how Astronomers know how far things are away from us and how big things are. For that matter how was the sizes of our own planets in our own Solar System determined as well as their distance?The method for determining distances to objects actually depends on how far away the object is. Distances to planets were first well-determined by Copernicus using simple observations of the positions of the planets. Relatively nearby objects beyond the solar system will appear to shift position relative to distant objects as the Earth moves from one side of the Sun to the other. This effect is called parallax, and you experience it everyday. Parallax gives reliable distances to stars up to about 1 00 parsecs. But 100 pc isn't very far, little more than the solar neighborhood. Distances to galaxies can be determined via Cepheid variable stars, and many other methods.

Once distances are known, it's not hard to get sizes. Suppose you hold a quarter at arm's length, and then have someone take that quarter 100 yds away. Obviously the quarter appears smaller, though it's real size hasn't changed. If yo u know how big it appears and how far away it is, you can work backwards and figure out how large the quarter really is. Astronomers can measure how big something appears to be on the sky, and if they can figure out it's distance, they can calcul ate how big it really is.

June 3, 1998Kyle (Washington, USA)Please explain what the Large Magellenic Cloud is.The Large Magellenic Cloud is simply the name given to a nearby galaxy. The galaxy was named for the explorer Magellan who discovered the galaxy during his trip around the world in 1519. This galaxy is irregular and measures about 7 kiloparsecs in diameter (it is much smaller than our own galaxy).
June 3, 1998Antonio (Florida, USA)What is a gravitational lense?A gravitational lense is nature's telescope...
May 27, 1998James (USA) What is significant about the Hubble telescope?The Hubble Space Telescope (HST) was the first mission of NASA's Great Observatories program. It was launched in 1990. It is capable of taking observations in the visible, near-ultraviolet and the near-infrared. Probably the most significant thing about the HST is that it is above the Earth's atmosphere, so it is free from distortions that Earth-bound telescopes are plagued with. The HST was also designed to 'see' farther in space than these Earth-bound telescop es.
May 26, 1998Colin (Michigan, USA) What is a nebulae and where do they come from?Nebulae are the dust of stars...
May 22, 1998Anthony (Florida, USA) What is another word for 'moon'?Another common word scientists use for moon is 'satellite'. A satellite is defined as a celestial body orbiting another larger body. So when people say I'm going to look at the satellites of Jupiter tonight using my telescope, they probably mean the y are going to look at the moons of Jupiter.
May 12, 1998Roxana (Sweden) What is a supernova?When really massive stars die they often blow up in a huge explosion called a supernova.
April 24, 1998Katherine (Australia) I live in the southern hemisphere. I've found it difficult to find sky maps or magazines talking about the southern skies. Can you help me with finding some sky maps?Katherine, I found a page on the internet that generates sky maps. If you enter your latitude and longitude, it will generate a map for you. Since you live in the southern hemisphere, the l atitude you enter should be negative (example, -39). Good luck!
April 14, 1998Matthew (California, U.S.A.) What is a quasar and where can I get a picture of one?We have an information page and images right here.
April 7, 1998Elizabeth (Oregon, U.S.A.) I am doing a project for school, and I need to know about dark nebulas. Can you tell me a little about them, and the name and coordinates (right ascention and declanation) of a dark nebula close to earth?Dark nebulae are big blobs of gas or dust in outer space. They are usually only visible because they hide the light of something bright behind them. There are quite a few of these, here is a list of some. One of the easiest to see is the dust obscuring the stars of the Milky Way, especially near Sagittarius(RA 19 hrs, Dec. -25 deg.
April 7, 1998Jason (Rhode Island, U.S.A.) How is the Oort Cloud formed?The Oort Cloud seems to have been formed from small objects near the giant planets. These objects were ejected from the Solar System by gravitational encounters with other objects. The objects that didn't entirely escape the gravitational force of t he Sun formed the Oort Cloud.
March 17, 1998Matt (Maine, USA) Do you know anything about the constellation Chamaeleon?The constellation Chamaeleon can only be seen from the southern hemisphere. Its abbreviation is Cha and its translation is--you got it! The animal, the chameleon. Its right ascension (RA in h) is 11 and its declination (degrees) is -80. That means it is best seen in April around 9 p.m. from the southern hemisphere!
March 17, 1998Anne Rachel (Philippines) Is there an atom in space, any atom in particular?. If none, where do the signals from sattelites pass through?There are many atoms in space, about 5 atoms per cubic centimeter. Most of these atoms come from the sun. In fact the sun is constantly spewing out atoms into space. This stream is called the solar wind. The solar wind is composed of many different atoms and molecules but mostly hydrogen & helium. But oxygen, and carbon dioxide are among the atoms and molecules which are out there.
February 18, 1998Mrs. Lyons (Maryland, USA) If a gamma ray burst happens in a nearby solar system, how long will it take for the rays to reach earth?Gamma rays are particles of light, and therefore travel at the speed of light, about 300,000 km/s. If they were to orignate from a solar system 100 pc away (within our own galaxy), it would take about 328 years for the gamma rays to reach us. But th e true distances to gamma ray bursts are unknown at this time.
February 18, 1998Jim ( Michigan, USA) What is the planet or star in the universe, farthest from the earth that is known(named)?The most distant object for which astronomers know the distance is the quasar PK 1247+3406. At a distance of more than 5000 megaparsecs, it is about 7000 times more distant than our nearest big neighbor, Andromeda . Recalling that looking far away is like looking back in time, this object is at the time astronomers believe galaxies may have first formed. While not fully understood, quasars may be the precursors to present -day galaxies. They are the most luminous and powerful objects in the universe - one reason we can see them so far away.
February 17, 1998Joe (California, USA) Is there anti-matter? How would it work or is it possible?In the 1930's, a scientist named Dirac came up with the first description of the electron that was consistent with both quantum mechanics and special relativity. One result of his description was that an anti-particle of the electron would have to ex ist. The anti-electron would have the same mass as the elctron, but it would have an opposite electric charge and magnetic moment. In 1932, Carl Anderson discovered the first anti-electron. He called this positive electron a positron. By the 1950's, p hysicists were able to produce the anti-proton, a particle with the mass and spin as a proton, but with negative charge and opposite magnetic moment. To create the anti-proton, protons were accelerated and smashed into a target containing other protons. Sometimes, the energy brought into the collision would produce a proton-anti-proton pair in addition to the original protons. This gave credibility to the idea that for every particle there is a corresponding anti-particle! See the ABC's of Nuclear Science for more details.
January 8, 1998Kevin (USA)How far can the Hubble Space Telescope see?When the HST was first sent into orbit, the telescope was nearsighted! Its mirror was improperly curved, allowing it to see only one third as clearly as it should have. Now, however, the problem has been co rrected. The distance the HST is able to see depends upon how big and bright the object is. However, it can see with about ten times the clarity of telescopes on Earth.
December 9, 1997Great Scott (Kentucky, USA)When was the Keck telescope invented?Today Caltech and the University of California operate two Keck telescopes. They premiered in 1995. Both are located in Hawaii. It took 14.4 tons of glass to make the mirrors within just one telescope! These things are big!
December 8, 1997Carole (New Jersey, USA)How many miles are in a light year?Since light travels at the speed of 186,000 miles per second, that means that in one year, light would travel a distance of approximately 5,870,000,000,000 miles. That's roughly 6 million million miles!

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