1. Asteroids, Asteroid Belt, and Dwarf Planets
Lindsay Visher
EGR 491 A – Telescope Design

2. Asteroids
Described by NASA: Rocky, airless worlds that orbit our sun, but too small to be called planets
Debris left over the formation of our solar system
As old as 4.6 billion years
Current known count: 781,692 asteroids
Majority are gathered in the main asteroid belt
Located between Mars and Jupiter
Can range in size: 33ft to 329 miles
Usually irregularly shaped
Few have moons
Sometimes called “minor planets”
Vesta – brightest and second largest object in the asteroid belt
Image taken by Nasa’s Dawn spacecraft in 2012
Vesta’s North Pole

3. Composition of Asteroids
3 main types of composition: C-, S-, and M-
C-type: (Chondrite)
Most common type
Composed of clay, silicate rocks – dark appearance
S-type: (Stony)
Composed of silicate materials, nickel-iron
M-type: (Metallic)
Composed of nickel-iron
Different Compositions are related to how far from the sun that the asteroid was formed
Image: Asteroid Ida and its moon Dactyl; S-type asteroid; the first asteroid found that has its own moon orbiting it
Image taken by Galileo spacecraft in 1994
Ida and its moon Dactyl

4. Asteroid Belt Between Mars and Jupiter
Formed when Jupiter’s gravitational pull caused small bodies to collide
Location of most known asteroids
Contains between 1.1 to 1.9 million asteroids
Largest - Ceres
Width = 1 km or 0.6 miles
Total mass of all the asteroids in the solar system = less than the Moon
Same circular orbit that the planets follow
Asteroids can also orbit planets – called Trojan Asteroids

5. Video https://www.youtube.com/watch?v=BKS0yW8dGcQ
Give an idea of how many asteroids there are in our solar system
And a timeline of how many we've found in the last couple of decades
Orange = main belt of asteroids

6. Observation of Asteroids
Can be seen from Earth with a decent telescope
Asteroids reflect some light
Dimmer than stars and planets
In opposition: appear brighter
Often “wandering” fast against starry background
~0.5 arcseconds/minute
Ecliptic plane
Take several images in the course of an hour
Can see dot(s) moving
Around 150x to 200x magnification
Might be able to see dots moving like this one
Specific Asteroid – Need to know its specific location
Opposition: When an astronomical body is on opposite side of the celestial sphere than the sun
Moving quickly = because they are much closer than stars
(Need bigger telescope and ~500x see shape of asteroid)
Ecliptic plane – easiest to see

7. Dwarf Planets According to the IAU, "dwarf" planet has 3 criteria:
1,2: Round object with a significant mass that orbits a star
3: Does not clear their orbital path
Definition was revised in 2006
Demoted Pluto and elevated Ceres to a Dwarf planet
Meaning:
- the status of a planet kind of depends on the area surrounding it
- Depends on size of the planet relative to the other objects around it
Pluto didn’t meet the third criteria – it does not have "gravitational dominance" over other large objects in its vicinity of space

8. Dwarf Planets in our Solar System
Five recognized dwarf
planets in our
solar system:
1. Ceres
2. Pluto
3. Eris
4. Makemake
5. Haumea
All located in the Kuiper Belt, excluding Ceres, which is located in the Asteroid Belt
Many more unconfirmed objects that could be classified as dwarf planets
As of 2014

10. Ceres Discovered in 1801 by Guiseppe Piazzi
Largest object in the Asteroid Belt
Compiles 25% of the asteroid belt's mass
Classified as a Dwarf Planet in 2006
Only one in the inner solar system
"Embryonic Planet" - did not complete its formation
NASA's spacecraft Dawn – actively exploring since 2015
Named after the ancient roman goddess of corn and harvests

11. Ceres Diameter = 588 miles Angular size = 0.9 arcseconds
Located 2.3 AU away from the sun
One orbit around the sun = 1682 days or 4.6 Earth years
One day on Ceres = 9 hours
Mantle is composed of water and ice
Said to contain more water than Earth
If Earth = size of nickel, Ceres would be the size of a poppy seed
Speculated that Ceres has a solid core and a mantle composed of water and ice
Contains more water than Earth does

12. How to Observe Ceres and Other ‘Dwarf’ Planets
Apparent Magnitude = +9.3
Magnitude +6.7 in opposition
Need at least 10x50 binoculars to view
Dwarf planets reflect some light
Have the same appearance as stars
Appear as a point with amateur scopes
Exact locations of dwarf planets are known
Point to the general region of the known dwarf planet
Compare with a good star chart
Can identify points in the sky that don’t appear on the chart  Dwarf planets
Magnitude 6.7 = will just be able to see with the naked eye

13. Provided by Dr. Lulay
Path of Ceres in June of next year

14. References:

15. References https://www.spacetv.net/asteroids/
from-your-backyard/

16. Questions?