The University of Texas at Arlington

The University of Texas at Arlington

UTA Planetarium

UTA Planetarium

Ask the Astronomer Q&A

Tag: "telescope"

  • Has NASA spotted an exoplanet orbiting Alpha Centauri a and b and proxima centauri?
  • Yes! A planet, known as Alpha Centauri Bb, was discovered orbiting around Alpha Centauri B, which is part of a three-star system just 4.3 light-years away from us. Alpha Centauri Bb zips around its star every 3.2 days, orbiting at a distance of just 3.6 million miles (6 million kilometers) and is approximately the same size as Earth. For comparison, Earth orbits about 93 million miles, or 150 million km, from the sun.

    (Tags:  earth  exoplanet  nasa  observatory  planet  star  telescope)
  • I was wondering if you could recommend a good telescope to get a better look at space. I don't mean a very expensive one, but a reasonable one to get a good look at the stars, planets.
  • If you are just beginning to use a telescope for enhancing your stargazing experience, we would recommend the Celestron FirstScope, which we have available in our gift shop for $60. This is a table-top telescope with a 3-inch diameter, perfect for viewing the planets and bright deep space objects, such as the Orion Nebula and the Andromeda Galaxy. This telescope is easy enough for children to use, but will last a long time. If you would like to get an intermediate or advanced telescope, I would recommend contacting the Texas Astronomical Society at They have a great online resource for finding the perfect telescope for your needs, and experts able to answer all your questions.

    (Tags:  astronomy  jupiter  mars  moon  planet  saturn  solar system  star  telescope)
  • I've always heard about what's OUT in space. But what about celestial objects that may be directly below us. Have we searched down there, or is everything in space at the same relative 'elevation' so to speak?
  • When astronomers talk about what it “out there”, they are not just referring to the objects that are in the same plane as the Earth. We have telescopes and observatories that study objects that are in line with us, but also those that are above and below us as well. Space is 3 dimensions, so we find objects equally scattered about in all directions, and astronomers want to study them all.

    (Tags:  astronomy  observatory  telescope  universe)
  • Is it possible for a satellite to maintain an orbit on the far side of the Moon (always hidden from Earth), given the complicating effects of Earth's gravity? If it is possible, what would the semi-major axis be?
  • No, it would not be possible for a satellite to orbit completely hidden from the Earth. To keep a satellite on the far side of the moon, it would have to orbit the Earth, not the Moon, every 28 days. Using Kepler’s law of planetary orbits, we can find the semi-major axis of the object with this equation (p^2/(a^3). Where a is the semi-major axis and p is the period. We know we want the period to be the same as the moon’s, 28 days. Which means that the semi-major axis would be equal to the moon’s semi-major axis. So the only way for the satellite to remain on the far side of the moon, is to place it on the moon itself. It is possible for the object to share the moon’s orbit (by trailing behind or ahead of the moon), but then we would be able to see it.

    (Tags:  earth  gravity  moon  satellite  telescope)
  • Is it safe to look at Jupiter through a big telescope this month, September 2010?
  • Absolutely! Jupiter is currently near opposition. It is the best time to see Jupiter and the Galilean moons Io, Europa, Ganymede, and Callisto. Unlike the Sun, it is always safe to look at planets with telescopes. To look at the Sun, specially designed filters that take 99.9% of light away must be used. Otherwise permanent damage to the eye will occur. It is even harmful to look at the Sun directly (with unaided eye).

    (Tags:  jupiter  light  planet  solar system  sun  telescope)
  • When will we get actual pictures of the class m planets recently discovered by Kepler? Artist conceptions are cool and optimistic, however the truth is always more amazing.
  • Unfortunately, astronomers do not have the technology to actually see, or take pictures of, exoplanets. Most exoplanets are discovered by indirect methods, like looking for a dimming in a star’s light, or for the wobble in a star’s orbit – which is caused by a planet pulling on the star. In order to directly see the planet, astronomers would need much larger telescopes than have currently been built, in order to see the incredibly small bodies at great distances. One of the closest exoplanets discovered is about 22 light years away – that’s approximately 135 trillion miles away – and is only 4 times the size of Earth (at approximately 32,000 miles in diameter)! This is way too small to be seen by our telescopes. So for now, the best we can do is imagine what the planets look like, with artist conceptions.

    (Tags:  exoplanet  gravity  light  observatory  planet  star  telescope)
  • Why do stars twinkle?
  • Stars twinkle because the light from the stars is passing through Earth’s atmosphere. As it does, it gets bent back and forth due to the turbulence in the air. At really high altitudes (like on a mountain or in a plane) or on very calm nights, the stars will not twinkle as much because there is less turbulence in the air. This is why many observatories are placed high on the mountains or in space, instead of at ground level. The less atmosphere star light has to travel through, the less it will twinkle. In space, stars do not twinkle at all.

    (Tags:  earth  light  observatory  star  telescope)