The University of Texas at Arlington

The University of Texas at Arlington

UTA Planetarium

UTA Planetarium

Ask the Astronomer Q&A

Tag: "asteroid"

  • As the Earth orbits around the Sun and goes through the debris fields year after year that produce the meteor showers, has there been any discovery that the number of meteors are diminishing? Are these 'debris fields' running out of debris? If not, why hasn't the number increased?
  • The average number of meteors seen per hour as we pass through debris fields does change from year to year. Sometimes it increases, sometimes it decreases. As we pass through the debris field, we of course are “cleaning up” the debris. So eventually we would expect that the debris field would disappear. However, the debris is actually coming from passing comets. When a comet gets close to the sun, it heats up, creating a tail of gas and dust. It is this dust that we pass through that creates the meteor showers we see. Each time the comet passes the sun it replenishes the debris field, and we can expect an increase in the number of meteors.

    (Tags:  asteroid  comet  meteor)
  • Is anything is space completely stationary? Or is everything moving in some way?
  • Everything in the universe is moving. Planets and stars rotate on their axes. Planets, asteroids, and comets orbit around stars. Stars orbit around the center of the galaxy. Galaxies and the whole fabric of the universe are expanding and moving away from the center of the universe.

    (Tags:  asteroid  comet  planet  star  universe)
  • Is the Earth in danger of being hit by a meteor in 2012?
  • The Earth has always been subject to impacts by comets and asteroids, although big hits are very rare. The last big impact was 65 million years ago, and that MAY have led to the extinction of the dinosaurs. Nothing is predicted to hit in 2012.

    (Tags:  2012  apocalypse  asteroid  dinosaurs  earth  extinction  meteor)
  • Why are planets round?
  • Simply put, planets are round because of gravity. Gravity pulls all the matter of a planet equally towards the center, creating a ball. Objects that are smaller, like asteroids, are not round, because there isn’t enough gravity to compress the object into a sphere. Instead they look like giant potatoes floating in space. In fact, planets themselves are not perfectly round either. We call them oblate spheres. Because they rotate on their axis as they go around the sun, the motion flattens the top and bottom of the planet a little bit, making the diameter at the equator greater than the diameter measured from the poles. This same effect is seen on the Sun and stars.

    (Tags:  asteroid  earth  gravity  planet  star  sun)
  • Why does it always say that the best time to watch for meteorites during a meteor shower is between midnight and dawn? Are there really more meteorites at that time, or is just because the sky is usually darker at that time?
  • It is possible to see meteors before midnight but it can sometimes be more difficult. Meteors are caused by the Earth “running into” debris fields left behind by passing comets. The reason that the best viewing time is generally said to be midnight or later, is not because the sky is darker but because the constellation the meteors appear to come from is higher in the sky at midnight, making the meteors much easier to spot. Before midnight, the constellation tends to be close to the horizon, so spotting meteors isn’t easy.

    (Tags:  asteroid  meteor)
  • Why doesn't Mercury have moons?
  • Most moons are captured asteroids or rocks left over from the formation of the solar system. Since Mercury is so close to the Sun, asteroids and comets that come close by are captured by the Sun’s gravity. They are either pulled in to the Sun and burned up or they go around the Sun as comets. Mercury doesn’t have as strong a pull of gravity as the Sun, so it is unlikely that it would be able to redirect the path of any incoming objects to turn them into moons.

    (Tags:  asteroid  comet  gravity  mercury  moon  sun)
  • Will an asteroid hit the Earth in ___?
  • Asteroids have hit the Earth in the past and will hit the Earth again someday, but not for a long time. Astronomers are keeping an eye on a couple objects. One, which will pass near the Earth in the year 2029, has a small (1:45,000) chance of an impact in 2036. The other object, depending on its spin, has either a 0 or a 1:300 chance of impact in the year 2880.

    (Tags:  asteroid  earth)
  • Will NASA ever get to Mars knowing that it's so far away?
  • I think what you mean to ask is not whether NASA will get to Mars, but will NASA send astronauts to Mars, and I think the answer is yes. We have been sending robotic probes to Mars for decades. Several are on the surface testing the soil and sending beautiful panoramic images back to us on Earth. Others are in orbit, taking high resolution images of the surface from above. The problem with sending astronauts to Mars is that it would be a 1-3 year trip. It all depends on the technology we use and how close Mars and Earth are to each other in our orbits. NASA’s Constellation Program, which was started under the Bush Administration, was a project to take the best of the Apollo and space shuttle missions, and create a spacecraft that could return astronauts to the Moon, and maybe eventually to Mars or some near-Earth asteroids. But the project was over promised, and over budget, so it was removed from the NASA budget. But, the current NASA budget has money set aside for taking us to Mars or near-Earth asteroids, it is just hoping for some help from the commercial market. It may take 10-20 years for the new system to be developed, but we will get to Mars within our lifetime.

    (Tags:  asteroid  astronaut  earth  mars  moon  nasa)