ASTR 1345 LAB 8 Kuiper Belt Objects Pre-Lab

What is the semi-major axis?

Half the total width of a planetary orbit as measured along the longest axis

Pluto was considered a planet until

It was found to share an orbit with many other large objects

If a dwarf planet has a semi-major (a) axis given as 71.1 AU, what is its period (the time required for one full revolution around the Sun) in years (stated with three significant figures)?

600. years (Kepler's Third Law can be used to calculate a travel time around the Sun with nothing more than the object's semi-major axis. In this case, that is given as 17.1 AU. So using Kepler's equation: a^3=P^2 --> square root of a^3=P --> square root of 17.1^3=square root of 359425.431= 599.521 years So the period is 599.521 years. Since the answer is needed with only 3 significant figures, 599.5 rounds up to 600. The decimal at the end of the number - specifically written as 600. - shows that all of the zeros are significant, and are not simply unknown values. The orbit is exactly 600 years, to three significant figures (not a little more than 600, like 602 or 603, and not a little less, like 598 or 597, but a spot-on 600. years)

Working with the ancient fossil record, paleontologists noticed that it appeared that Earth suffered major extinctions every 27,000,000 years. In turn, astronomers have found evidence of large impacts on the surface - marked by left-over craters - with spacings of 27,000,000 years. It was theorized that the Sun might have had a companion star - a small, dim, red dwarf class star with a mass around 100 times that of Jupiter - lurking out far beyond the Kuiper Belt. Further, if the orbit of this small star - dubbed Nemesis - passed close to the Kuiper belt during perihelion, its gravitational disturbance could upset some KBO orbits, launching asteroids on orbits that brought them crashing into the Earth. If there was a mini-companion star to the Sun named Nemesis, how far away would it have to be to periodically cause a bombardment (and mass extinctions) on Earth?

90,000 AU

A KBO is found to have a semi-major axis of 47.81 AU and an eccentricity of 0.35. What species of KBO is this?

A Plutino

The KBO 2008 KV42 is nicknamed "Drac" after the character Dracula who, in the original Victorian novel, could walk on walls and ceilings. This KBO has an orbital inclination of 103.5 degrees, an eccentricity of 0.553, and a period of 306.5 years. What kind of KBO is Drac?

A Scattered Disk Object

What is the aphelion and perihelion for Orcus?

Aphelion is its greatest distance from the sun at 48.07 AU; perihelion is its smallest distance from the sun, at 30.27 AU

According to the definition of a planet, which of the following is expressly critical for being considered a true planet in our solar system?

Being spherical (Having a moon is irrelevant to planetary status (in fact, Mercury and Venus would fail that test, since neither has a moon, whereas Pluto has 5 that we know of). Having a substantial atmosphere is also unnecessary, as Mercury has no permanent atmosphere and Mars's atmosphere is razor thin. All of the major planets have a period less than 200 years (just barely for Neptune) but that doesn't determine planet status either. If distance between planets was required to be at least 3AU, Mercury, Venus, Earth, and Mars would fail, since those four planets are all located less than 1AU from one another. To be a planet, an object must meet three physical and orbital criteria, of which one is: the planet must be spherical.)

Some of the largest KBOs known so far are the following: 2000 WR106 (Varuna), 2001 KX76 (Ixion), 2002 LM60 (Quaoar), 2003 EL61 (Haumea), 2003 UB313 (Eris), 2003 VB12 (Sedna), 2004 DW (Orcus), and 2005 FY9 (Makemake). Which of the following has those Kuiper Belt objects placed in order of descending diameter? (Ordered from largest to smallest)

Eris, Orcus, Sedna, Makemake, Quaoar, Haumea, Ixion, Varuna

What is Earth's discriminant?

Greater than one and a half million Earth's discriminant - a measure of a planet's mass compared to the combined mass of everything it shares an orbit with, such as asteroids, dust grains, and other assorted debris - is the largest in the solar system at 1.7 million. That means that the planet Earth outweighs everything else around it for tens of millions of miles by 1.7 million times. By contrast, Pluto's discriminant is 0.07, meaning that Pluto is only 0.07 times (or 7%) the size of everything which it shares an orbit with, including the large dwarf planets Eris and Orcus.

What does the discriminant measure, in terms of its astronomical usage?

It is a measure of a planet's dominance in its orbital vicinity (The discriminant - mathematically - is a measure of a planet-candidate's mass divided by the mass of everything which crosses its orbit (with the exception of moons, which are clearly bound to and dominated by the planet). The larger the discriminant, that greater the dominance of the planet. The smallest discriminant for a major planet - Neptune's discriminant - is ~25,000. So Neptune is 25000 times more massive than the things which cross its orbit. In turn, the next smallest discriminant after Neptune's is a tiny 0.33, the discriminant of the large asteroid and dwarf planet Ceres, which is only 0.33 times (33%) as massive as the rest of the Asteroid Belt)

Where is the Kuiper Belt?

Just beyond the orbit of Neptune, extending out to about 50 AU

If a dwarf planet has a semi-major (a) axis given as 71.1 AU and an eccentricity (ε) of 0.17, which of the following equations will give you the aphelion (aaph or Q) of the orbit?

Q = a (1 + ε)

Which of the following is not considered a "dwarf planet" by the International Astronomy Union?

Sedna