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The Sun, the closest star

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Title: The Sun, the closest star Author: Steven/Spangler Last modified by: Steven/Spangler Created Date: 9/12/2010 10:20:48 PM Document presentation format – PowerPoint PPT presentation

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Title: The Sun, the closest star


1
The Sun, the closest star
  • Background for next weeks lab

2
What are the absolute magnitudes of some stars
Star M (abs. mag)
Sun 4.8
Tau Ceti 5.8
Altair 2.2
Vega 0.5
Deneb -6.9
UV Ceti A 15.3
Apparent magnitude of Jupiter right now -2.9
  • Remember this is how bright they would be if
    they were all lined up at the same distance

3
What is the meaning of this huge range in the
intrinsic brightness (absolute magnitudes) of
stars?
4
The Sun.our chance to see a star up close
5
The Sun Basic physical properties
  • Mass 1.989E30 kg (330,000 mass of Earth)
  • Radius 696,000 km (109 times than of Earth)
  • Density 1.5 g/cc
  • Surface temperature 5800K

6
A question (no clickers this time)
  • How do we know the radius (or diameter) of the
    Sun?
  • How do we know the mass of the Sun?

7
The Sun and the other stars are in a different
class of size than the planets
8
Further properties of the Sun
  • The chemical composition of the Sun cosmic
    composition
  • The luminosity of the Sun 3.85E26 Watts
  • The age of the Sun (how could we know this?)
  • Comparison with other objects (Vega, Arcturus,
    stars in M13, etc)

9
What is the Sun made of?
The stuff of the universe The recipe of Jupiter
and Saturn
10
The changing face of the Sun
11
In contrast to today, there can be many sunspots
on the Sun
Sun of October 30, 2003
12
Structure of a Sunspot
Sunspots are regions of very strong magnetic
field (2000 Gauss)
Demo
13
Solar magnetic fields reach far out into space
14
The 11 Year Solar Cycle
  • The Sun has a heartbeat its properties change
    on a period of 11 years

15
Latest data on this sunspot cycle
16
An indication that our knowledge of the solar
cycle is far from perfect
17
(No Transcript)
18
Predictions in 2007
Observations and predictions as of today
19
The Sunspot Cycle has been going on for a long
time
Observations show cycle persisting, but turning
off from 1650 to 1730 (Maunder Minimum)
20
The Structure of the Solar Atmosphere
  • Photosphere
  • Chromosphere
  • Corona
  • Temperature increases as you go up
  • Outermost layer flows out into space to form the
    Solar Wind

21
The Solar Wind
  • A wind past the Earth at 400 km/sec
  • The Sun is melting away
  • Density 19 orders of magnitude less than
    atmosphere
  • A medium for solar events
  • May have sandblasted the early atmosphere of
    Mars

22
The Lesson for Other Stars
  • Do they also have sunspots, sunspot cycles, etc?
  • How does all this (magnetic fields, solar wind,
    rotation) relate to the age of a star?
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