Solar Neighborhood

1
Solar Neighborhood

• We have explored the Solar System from the Sun
  outward
• Today, we will take a little tour of nearby stars
  in the solar neighborhood
• In 1020, you will look at stars in more depth and
  gradually work your way out deeper and deeper
  into the universe

2
Do We Know Our Neighbors?

• One would think that we should know all there is
  to know about the nearest stars
• Unfortunately, there are many problems which
  complicate the situation
• The nearest stars are a varied bunch of many
  different spectral types and their may be many
  more left to discover

3
Alpha Centauri System

• The nearest known star system is Alpha Centauri
  (the brightest star in the Centaur constellation)
• The bright star is easily visible to naked eye
• When looked at through a telescope, the star is
  actually resolved into two components
• Alpha Centauri A B
• Further study has revealed a third component to
  the system, Proxima Centauri

4
What Do Our Neighbors Look Like?

• Alpha Centauri A B are both somewhat similar to
  our Sun
• Alpha Centauri A is slightly larger than our Sun,
  but of the same spectral type, while B is
  slightly smaller and cooler
• Proxima, the nearest known star, is a very small
  red dwarf, only about a tenth of the mass of the
  Sun

5
Alpha Centauri System
6
Life in Alpha Centauri?

• As the nearest known star system, Alpha
  Centauri's similarities bring up the question of
  habitable planets
• Components A B should both have areas where
  Earth-like planets are possible

7
Barnard's Star

• The next closest star is Barnard's Star, at a
  distance of about 6 light years away
• Barnard is also the star with the highest proper
  motion moving across the sky
• Like Proxima, Barnard's Star is a small red
  dwarf, much dimmer and cooler than our Sun
• In time, Barnard's Star will get within 3.8 light
  years of the Sun

8
Wolf 359

• The next closest star (third known system) is
  Wolf 359
• Wolf 359 is another small red dwarf much fainter
  than the Sun
• These small red dwarfs have a tendency to be very
  active with many large flares
• Wolf 359 is about 7.8 light years away in the
  constellation of Leo

9
Sirius - The Brightest Neighbor

• Sirius, the Dog Star, is the brightest star in
  the sky (except for the Sun)
• Closer inspection reveals that Sirius also has a
  small companion
• Sirius A is a main sequence star a little more
  than twice the mass of the Sun
• Sirius B is a white dwarf, the burnt out core of
  a former star

A
B
The Sirius system is 8.6 light years away
10
Neighborhood Comparisons

• Nearby stars come in a variety of forms both
  larger and smaller than the Sun
• The majority of the stars are smaller, with red
  dwarfs taking up a significant fraction
• Also notice that many of the nearby systems are
  binary or even triple systems

11
Neighborhood Photo
12
Biases in the Neighborhood

• Cataloguing the stars in the nearby neighborhood
  is harder than one would think
• What determines if we will be able to see a star
  or not?
• The brightness of the star
• Small stars will only be seen if they are close
  up
• Large stars will be easily seen from a distance
• These factors combine to make it easier to find
  large stars instead of nearby small stars

13
The Little Guys Rule
14
Will More Be Found?

• Currently, there are about a dozen stars known to
  be within 10 light years of the Sun
• A few students and professors at Georgia State
  are attempting to find all stars within 25
  parsecs of the Sun
• Keep in mind that there may be very faint objects
  closer than Proxima that we just can't see!