## “Mister” Sol’s neighborhood

The New Horizons spacecraft is on its way to Pluto. It left Earth back in January 2006. Now it is almost halfway between the orbits of Saturn and Uranus. When will it reach Pluto? Not until July 2015. Why so long? Pluto is “out there.” How “out there” is it? A scale model can help.

For this model we will need a meter stick and something to mark the positions of each planet’s orbit, like a pen, small pieces of masking tape, or pins. The Sun is at the beginning of the meter stick. On this scale it would be the size of the point of a pin.

Mark each planet’s orbit at the distance given below.

Distance (inches)

Mercury 3/8
Venus 3/4
Earth 1
Mars 1 l/2
Jupiter 5 3/16
Saturn 9 9/16
Uranus 19 1/4
Neptune 30 1/8
Pluto 39 l/3 - at the far end of the meter stick.

In this scale model, New Horizons is now about 14 inches from the Sun. As can be seen, it is still a long way from Pluto. How far away are the nearest stars on this scale?

For distances beyond the solar system, a light-year is one of the units of distance that are used. Although it is sometimes confused with a unit of time, a light-year is the distance light travels in one year. Light (in a vacuum) travels 299,792.458 kilometers (186,282 miles) in one second. This is about 7 ½ times around Earth. A light-year is about 9,460,000,000,000 kilometers or 5,880,000,000,000 miles.

In our meter stick model, one light-year is one mile. Since the nearest star to the sun is 4.2 light-years away, in the meter stick model, it is over FOUR MILES AWAY! Pluto now seems very close.

Below is a list and a diagram of all of the stars within 10 light-years of the Sun. The distance to each star in light-years is distance to each star in miles in the meter stick model. With the exception of the stars in the Alpha Centauri and Sirius systems, those within 10 light-years of the Sun are red dwarf stars.

The Sun’s Neighborhood

This image shows the relative sizes of some of these stars.

Models can sometimes help our understanding of difficult concepts. With less than a dozen pinpoint sized stars in a 10 mile radius, our neighborhood is mostly empty space.

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## 2 thoughts on ““Mister” Sol’s neighborhood”

1. Your image above is very interesting to me, if I may ask where and how far in light year would VV Cephei A be from our sun?

2. The distance to the interesting binary star system VV Cephei is very uncertain. It is too far away to accurately determine its distance by triangulation (the method used for nearby stars). It is certainly thousands of light years away.

James Kaler, Professor Emeritus of Astronomy at the University of Illinois, suggests that if VV Cephei is a member of the Cepheus OB2 association of hot blue stars, its distance would be between about 1900 and 2900 light years. If it is not part of the association, it could perhaps be twice as far away. (http://stars.astro.illinois.edu/sow/vvcep.html)