Notes 13 – Tools and Notes 13 – Tools and Classification of StarsClassification of Stars

Mrs. Gordon Mrs. Gordon

Earth ScienceEarth Science

Thursday, April 20, 2023Thursday, April 20, 2023

HaHa Funny! HaHa Funny! Sort of…Sort of…

Star light, star brightStar light, star brightFirst star I see tonightFirst star I see tonight I wish I may, I wish I might.I wish I may, I wish I might.Oh, It's just a satellite….Oh, It's just a satellite….

1. Tools of Today1. Tools of TodayA. Electromagnetic SpectrumA. Electromagnetic Spectrum – energy – energy

that travels in wavesthat travels in waves Different wavelengths help determine the Different wavelengths help determine the

composition of objects in space.composition of objects in space. (what they are (what they are made of, how hot they are)made of, how hot they are)

B. TelescopesB. Telescopes (or light buckets)(or light buckets)

OPTICAL OPTICAL telescopes are the telescopes are the most common, most common, however there are however there are also radio, infrared, also radio, infrared, UV and other high-UV and other high-energy telescopes.energy telescopes.

RefractingRefracting – – uses uses lenseslenses

ReflectingReflecting - uses - uses mirrorsmirrors

Why Reflectors are preferred Why Reflectors are preferred over Refractors:over Refractors:

Chromatic aberration – light must pass through a Chromatic aberration – light must pass through a lens, it is difficult to make the glass completely lens, it is difficult to make the glass completely uniformuniform

Glass absorbs some radiation (infrared, UV)Glass absorbs some radiation (infrared, UV) Large lenses can be quite heavy, and can only Large lenses can be quite heavy, and can only

be supported around the edges so the glass can be supported around the edges so the glass can deform under its own weight, mirrors can be deform under its own weight, mirrors can be supported on one whole side.supported on one whole side.

A lens has TWO sides that need to be cared for, A lens has TWO sides that need to be cared for, a mirror only has one a mirror only has one

C. Hubble Space TelescopeC. Hubble Space Telescope World's first space-based World's first space-based

optical telescopeoptical telescope Launched in 1990, orbits Launched in 1990, orbits

Earth about once every 95 Earth about once every 95 minutes minutes at an altitude of at an altitude of about 350 miles. about 350 miles.

The most expensive The most expensive scientific instrument ever scientific instrument ever constructed… Cost ~ $2 constructed… Cost ~ $2 BillionBillion

Hubble transmits about 120 Hubble transmits about 120 gigabytes of science data gigabytes of science data every week. That's equal to every week. That's equal to about 3,600 feet of books about 3,600 feet of books on a shelf. The rapidly on a shelf. The rapidly growing collection of growing collection of pictures and data is stored pictures and data is stored on magneto-optical disks.on magneto-optical disks.

Hubblesite.orgHubblesite.org

D. ObservatoriesD. Observatories

Contain telescopes on the groundContain telescopes on the groundUsually located on high mountain tops, Usually located on high mountain tops,

away from cities.away from cities.Mauna KeaMauna Kea

Other cool TelescopesOther cool Telescopes

Arecibo Radio Arecibo Radio Telescope, Telescope,

Puerto Rico      Puerto Rico      

Very Large Very Large

Array,Array,

New MexicoNew Mexico

2. Classifying Stars2. Classifying Stars A. Astronomers classify stars by:A. Astronomers classify stars by:

colorcolor temperature temperature size size brightness brightness ((and this depends on temp. and sizeand this depends on temp. and size))

B. Apparent magnitudeB. Apparent magnitude - how bright a star - how bright a star looks looks from Earth.from Earth. This depends on how far away it is This depends on how far away it is AND how bright the star actually is (luminosity)AND how bright the star actually is (luminosity)

C. Absolute magnitudeC. Absolute magnitude – how bright a star really – how bright a star really is at a standard distance from Earthis at a standard distance from Earth

D. D. H-R DiagramH-R Diagram Charts stars by Charts stars by temperaturetemperature

and and absolute magnitudeabsolute magnitude.. Used to:Used to:

classify starsclassify stars understand how understand how stars change over timestars change over time

Main SequenceMain Sequence - 90% of all - 90% of all starsstars

Super GiantsSuper Giants – large, cool, – large, cool, brightbright

Red GiantsRed Giants – large, cooler, – large, cooler, medium brightnessmedium brightness

White dwarfsWhite dwarfs – small, hot, dim – small, hot, dim

Hertzsprung-Russell Diagram interactiveHertzsprung-Russell Diagram interactive

Our star – the Sun – Our star – the Sun – is an is an averageaverage star on star on the main sequence.the main sequence.

Betelgeuse is listed as the brightest star in Betelgeuse is listed as the brightest star in the constellation of Orion. Betelgeuse's the constellation of Orion. Betelgeuse's reddish hue is due to it being a well-reddish hue is due to it being a well-developed red giant star.developed red giant star.

The star's outer layers have expanded to The star's outer layers have expanded to such a degree that if it were where the Sun such a degree that if it were where the Sun is, Earth would actually be inside it. When is, Earth would actually be inside it. When Betelgeuse finally uses up all its hydrogen Betelgeuse finally uses up all its hydrogen fuel, the outer layers will be cast out from fuel, the outer layers will be cast out from the main star which will then explode as a the main star which will then explode as a supernova. This event could happen any supernova. This event could happen any time in the next million years or so.time in the next million years or so.

In this ultraviolet image of the Sun, a prominence arcs In this ultraviolet image of the Sun, a prominence arcs thousands of miles above the solar surface and white patches thousands of miles above the solar surface and white patches reveal magneticallly acive regions. The Solar and Heliospheric reveal magneticallly acive regions. The Solar and Heliospheric Observatory, SOHO, returned this image in 1997. It's one of Observatory, SOHO, returned this image in 1997. It's one of many spacecraft dedicated to monitoring our star. many spacecraft dedicated to monitoring our star. NASA / NASA / SOHOSOHO