The University of Texas at Arlington

UTA Planetarium

Ask the Astronomer Q&A

Tag: "pluto"

• Gliese 710, an Orange dwarf star, will be headed our way in 1.5 million years. Gliese﻿ 710 is expected to come within 1.1 light years of our Solar System, perturbing the Oort Clouds and its comets. Can it grab some of the moons of the giant gas planets (Jupiter, etc) and make them satellites for itself, re-arranging our Solar System?
• It is not likely that Gliese 710 will have any effect on the moons of the gas giant planets because 1.1 light years is still a very long way away. For reference, the Sun is about 8 light minutes away from Earth. Pluto is about 5.6 light hours away from the Sun. At 1.1 light years away, Gliese will be over 5 trillion miles from the solar system. This may be close enough for the star’s gravity to have an effect on the edge of the Oort Cloud, as you mentioned, but this will likely mean an increase in meteor showers and comets. It would not completely rearrange our solar system.

(Tags:  brown dwarf  earth  gravity  jupiter  meteor  planet  pluto  saturn  solar system)
• How does the Sun's gravity keep Pluto in orbit, since it is so far away?
• The Sun’s gravitational effect extends infinitely away from an object. The size and distance of the objects does not matter. In order to stay in orbit around the Sun, an object just has to follow Kepler’s Law of Motion: a^3=p^2. Where a is the semi-major axis and p is the period of rotation. In Pluto’s case a=39.264 AU (1 AU is equal to the distance between the Earth and the Sun – so Pluto is 39 times farther from the Sun than Earth is) and it’s period, p, is just over 246 years.

(Tags:  gravity  pluto  sun)
• I know that Mars cannot hit Earth because it is so far away, but is there another reason why this is not scientifically possible?
• Mars can never hit Earth because the two planets are in stable orbits around the Sun. The orbits do not intersect with each other, so there is no way the two objects could collide. But it is possible that Neptune and Pluto may someday collide with each other due to their intersecting orbits. We would need a catastrophic event to happen, like a star or black hole passing through our solar system, to change the orbits of the planets enough to cause Mars and Earth to collide.

(Tags:  earth  mars  neptune  pluto)
• If Jupiter had developed into a brown dwarf star what effects would that have had on Earth's development? How visible would Jupiter be during the day and at night as a star?
• If Jupiter was a brown dwarf star, it would not affect Earth very much. Brown dwarfs do not create much light, and since Jupiter is an average of 5 AU from the Earth (5 times the distance between the Earth and the Sun) it would appear as a pinpoint of light, a little brighter than Venus in the night sky. The farther away from the object you get, the dimmer and smaller it appears in the sky. For example, if we were to travel to Pluto, there would be no daytime. The Sun appears as a very bright star compared to the other stars in the night sky. But because it is so far away, it does not cast enough light on Pluto’s surface to have a bright daytime sky.

(Tags:  brown dwarf  jupiter  pluto  star  sun)
• Is Pluto a planet, or what?
• It's more of an "or what." When Pluto was discovered, it was thought that it was bigger than the Earth. But it was figured out that Pluto was even smaller than the Earth's Moon. But that's not what did it in. Starting in 1992 icy objects similar to Pluto were found past Neptune, many in similar orbits to Pluto. It was discovered that there was a second asteroid belt, but made of icy objects, instead of rock. Pluto was still called the smallest planet, and the biggest Kuiper Belt object (Kuiper Belt is named for Dutch-American astronomer : Gerard Kuiper), or KBO. In 2005 a KBO slightly bigger than Pluto was discovered (now called Eris). In light of the new evidence, the voting members of the naming committee to the International Astronomical Union decided to reclassify Pluto.

(Tags:  planet  pluto  solar system)
• Isn't it possible that other planets rotate in and out of our solar system on longer cycles in elliptical orbits. E.G. Nibiru at 3,600 year cycles that our current civilization has not observed?
• Although it is theoretically possible that more planets exist in our solar system that we have not detected, it is very unlikely. Everything in the universe has gravity, and this gravity effects everything in the universe. The closer 2 objects are to each other, the more their gravity effects surrounding objects. The same is true for large objects. The larger the object, the more gravity will effect surround objects. These effects are measurable by astronomers, even outside our own solar system. Astronomers have used this technique to find hundreds of planets in orbit around other stars. Since we have never seen any gravitational interaction on our Sun or the planets in our solar system, astronomers believe there are not any very large planets beyond the orbit of Pluto.

(Tags:  2012  gravity  nibiru  physics  planet  pluto  solar system  sun)
• What is a "dwarf planet" exactly?
• An unfortunate name. Many people have an emotional tie to Pluto being a planet. They even have "When I was your age Pluto was still a planet" t-shirts. The pro- "Pluto is a planet" group was strong, so a compromise was made and "dwarf planet" was born. A planet now has to meet three criteria. First, it is big enough to make itself round (Pluto is), goes around the Sun, and not a planet (Pluto does), but also has to clear its orbit (Pluto does not). A dwarf planet meets the first two conditions but not the third. A better term would have been "big asteroid."

(Tags:  planet  pluto  solar system)
• What is the size and brightness of the Sun as viewed from the different planets in the Solar System?
• We have a few simple calculations that you can use to find the size (in degrees) and the brightness of the Sun on each planet. In fact, these calculations will work for the brightness and size of the Sun from anywhere in the universe, as long as you know the distance of the object from the Sun in AU. To find the size of the Sun in degrees: a = 0.5/distance (in AU) where a is the size in degrees and 0.5 is the size of the Sun as seen from Earth. To find the brightness of the Sun as compared to its brightness as seen on Earth: M = 2.5 * log(distance)^2 – 26.74 Where M is the apparent magnitude of the Sun and 26.74 is the magnitude of the Sun as seen on Earth.

(Tags:  earth  jupiter  mars  moon  planet  pluto  saturn  solar system  star  sun  venus)
• Why is Pluto so cold?
• Planets are warm because they trap heat from the Sun, but Pluto is so far away that it doesn't get much heat or light from the Sun. Light from the Sun takes 6 hours to reach Pluto. Compare that to the 4 minutes that it takes light from the Sun to reach Earth. In fact, Pluto is so far away that the Sun would begin to resemble all the other stars that we see at night.

(Tags:  earth  light  pluto  solar system  star  sun)