the night sky (part 2)bergeron/osher92/the_night_sky_2.pdf · venera 9’s half panorama...

The Night Sky (Part 2)

Paul Bergeron

Department of Physics and Astronomy,University of Utah, Salt Lake City

April 20, 2018

Today’s Plan

Non-constellations

I All can be observed with a decent telescope

I What’s what in the solar system

I Comets

I The Sun

I Clusters & Galaxies

What’s in the skyAnncient – Medieval

I Everything is a star!

I Some are weird wanders: planets (7)• Mercury – Saturn, & our Moon

I Some mysteriously appeared and disappeared:• ‘new stars’: comets & Supernovae

Medieval – Modern

I Medieval Period: + Sun (now 8)

I 1800s: 11 planets:• - Sun & Moon, +Uranus, + Ceres, Pallas, Juno, Vesta

I some of these planets are weird :• asteroids! (now 7 planets)

I 1821 (Bouvard): Uranus is weird... it’s being pulled

I 1846: The predicted Neptune discovered (now 8, again)

But... Pluto?

Discovery

I Discovered in 1930

I Named by Venetia Burney11 year old English school girl

I Mass: 7M⊕

but it’s weird

I 1948: 0.1M⊕

I 1964: ...comet?

I 1978: ∼ 0.02M⊕

I 1990s: it’s not alone... Kuiper Belt

I It’s just like Ceres & Eris...

PlanetsDefinition (non-technical)

I Orbits the Sun

I ‘Spherical’

I Alone

Not without problemsWhy “Dwarf” planet?

Image Credit: Wikimedia Commons

8 Planets


5 Dwarf Planets


Planets – Venus

Inner orbit

I Difficult viewing

I Only at evening or morning

I Ancients: two ‘stars’

via Wikimedia Commons:

Venera 9’s half panorama

Observational Significance

I Galileo observed phases⇒ it orbits the Sun

I 1761/1769 Transit of the Sun• Observe from two locations• time the measurements⇒ Distance to the Sun

Halley, 1716

CometsAnatomy

“Comet”: Greek for “fuzzy”

I nucleus: main body

I coma: outgassed atmosphere

I tail: heated gas escaping

I jets: heated gas from geysers Holmes, via Wikimedia Commons

Origin

I Short Period comets: Kuiper Belt

I Long Period comets: Oort Cloud?

Image Credits:Wikimedia Commons

Upcoming Comets

Comets this year

I Now – July: PanStaRRS (C/2016 M1)• Morning Sky

I July – August: PanSTARRS (C/2017 S3)• Morning Sky

I July – November: 21P/Giacobini-Zinner

I October – December: 38P/Stephan-Oterma

I September – December: 46P/Wirtanen• December: naked eye viewing with dark skies

Halley’s Comet: not until 2061

Meteor Showers

What are they?

Comet debris burning up in our atmosphere

Upcoming ones

I Lyrids: Late April• From Thatcher

I Eta Aquariids: Early May • From Halley’s Comet

I Perseids: mid-August• From Swift-Tuttle

I Leonids: mid-November• From Tempel-Tuttle

The Sun

Filters

(Image Credit: Central New York Observers)

Fusion

(Image Credits: Central New York

Observers)

Local Group

The Local Group


Galaxies

Andromeda (M31) Image Credits: Wikimedia Commons

I 780 kpc away(∼ 14000 times the MilkyWay diameter)

I Furthest visible object

I Will collide with us(eventually)

Satellite Galaxies Image Credits: Wikimedia Commons

Triangulum Galaxy (M33) M32 Large & Small Magellanic Clouds

the night sky (part 2)bergeron/osher92/the_night_sky_2.pdf · venera 9’s half panorama...

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