Announcements

1
Announcements

• Observing on the roof of Van Allen Hall, clear
  sky patrol, will begin on Tuesday, September
  7th. For that week, it will run from Tuesday to
  Thursday from 9 pm to 11 pm on clear nights.

2
Planets beyond the solar system

• Yesterdays news
• Life
• The habitable zone
• Evolution of life on Earth
• Communicating with intelligent life
• Reading all of chapter 27

3
(No Transcript)
4
(No Transcript)
5
Researchers don't know the composition of these
new, smaller planets or what they actually look
like. In our solar system, Neptune and Uranus
are of similar size and they are composed of an
icy, rocky core enveloped in a thick atmosphere
of hydrogen and helium. But they sit in the
farthest coldest reaches of our solar system. By
contrast, both of the new planets are very close
to their stars, making them difficult to spot.
6
(No Transcript)
7
One of them orbits very close to the star named
55 Cancri, which is about the same size as our
sun and located 41 light-years away in the
constellation Cancer. The new planet was located
by University of Texas-Austin astronomers using
the Hobby-Eberly telescope in the Davis Mountains
southeast of El Paso. The star already had three
known gas giant planets looping it in orbits that
take anywhere from 14 to 4,520 days. The new
planet is the innermost of the quartet, zooming
around the star in 2.8 days from a distance of
about 3 million miles. Researchers acknowledged
there probably are several different types of
solar systems orbiting distant stars. But for
now, the 55 Cancri system bears the closest
resemblance to ours.
8
(No Transcript)
9
55 Cancri

• Star 60 as bright as the Sun and only 5 less
  massive than the Sun.
• Outermost known planet has an orbit similar to
  that of Jupiter, but is 4 times the mass of
  Jupiter.
• Inner 3 planets all lie within the orbit of
  Mercury one is about the mass of Jupiter.

10
The other new planet discovered by American
scientists orbits a star called Gliese 436, that
lies about 33 light-years from Earth in the
direction of the constellation of Leo. This
Neptune-sized planet also sits 3 million miles
from its star and whips around in a tight
circular orbit once every 2.64 days. Besides the
exoplanet's size, what makes the discovery
remarkable is that Gliese 436 is a red dwarf star
that produces only 2 or 3 percent as much light
as the Sun. Stars in this category account for 70
percent of the stars in the Milky Way galaxy, but
until now, astronomers had not believed that such
faint stars would yield new planets. "We
estimate there is something like 20 billion
planetary systems existing in our Milky Way
galaxy alone," Butler said.
11
Two more exoplanets both gas giants also were
spotted in the past week. One was by the same
European team using a telescope in Chile. The
other was discovered by a U.S.-based team using a
network of small telescopes on California, Texas
and the Canary Islands. Instead of measuring star
wobbles, they measured the tiny amount that a
star dims when a planet passes by in its
orbit. So, a total of 4 new planets were
discovered (really announced) last week.
12
What is Life?

• What are the essential characteristics of life?

13
What is Life?

• Essential elements are
• Life reproduces itself
• Life is able to adapt and pass changes to new
  generations
• This seems to require a genetic code which can
  stores information about how to grow new organism
  and is passed from generation to generation

14
Life on Earth

• Is based on organic molecules those
  containing carbon atoms
• Carbon can combine with hydrogen and other atoms
  to form complex molecules
• Complex molecules appear necessary to store the
  information needed for a genetic code
• Life on Earth uses DNA, a carbon-based molecule,
  to store the genetic code

15
Life on Earth

• Life on Earth appears to require water
• No life is know to exist in the complete absence
  of water
• Water allows other molecules to dissolve, move
  around, and interact with each other

16
Habitable zone

• The requirement for water suggests those planets
  which have liquid water may be the most promising
  havens for life.
• In order to have liquid water, a planet must be
  not too cold and not too hot, i.e. at a
  temperature between freezing and boiling.
• How warm a planet is depends on its distance from
  the sun.

17

18
Are there any exceptions to the habitable zone?

• Yes, if there are sources of energy other than
  the sun to keep a planet (or moon) warm.
• Possible energy sources
• Radioactivity
• Tides
• Liquid water oceans are though to exist on
  Jupiters moon Europa

19
Are 55 Cancris planets in the habitable zone?
20
Evolution of Life on Earth

• Even if we find life on another planet, is it
  likely to be a higher form of life such as
  mammals or something simpler?
• What form of life occupied the Earth for most of
  its history?

21
Evolution of Life on Earth

• 4.6 billion years ago Earth formed
• 3.96 oldest rocks
• 3.5 oldest fossils single celled
  life
• 0.7 multicellular life
• 0.0001 humans (homo sapiens)

22
History of life on Earth in 12 hours
23
Carl Sagans Cosmic Calendar The history of the
Universe in one year
Big bang
Milky Way forms
Sun and planets form
Oldest known life - single cell
First multicellular life
24
(No Transcript)
25
Search for Extraterrestrial Intelligence (SETI)

• We could avoid this whole business of searching
  for planets and primitive forms of life, if
  extraterrestrials would just send us a message.
• There are active searches for such signals,
  mainly in the radio, some using visible light.
• One thing that is needed is more computing power.
  You can volunteer your computer to process SETI
  signals while the screen saver is on at the web
  site http//setiathome.ssl.berkeley.edu/