Astronomy 103: 4-Light and Matter

Artemis II Mission Overview

Launch Details

  • Scheduled Launch Date: February 8, 2026 at 10:20 CST (check for updates)

  • Nature of Mission: First crewed flight beyond low Earth orbit since Apollo 17 in 1972

  • Crew Composition: 4 Astronauts; mission duration 10 days

Mission Objectives and Specifications

  • Key Milestones:

    • ICPS (Interim Cryogenic Propulsion Stage) Operations:

    • Deployment and Earth disposal

    • Cubesat maneuvers

    • No plans for a moon landing, similar to Apollo 8 mission

    • Launch Procedures:

    • Steps Include:

      • Perigee raise maneuver

      • Apoogee raise burn to high Earth orbit

      • Orion separation from ICPS, followed by proximity operations demonstration

      • High Earth orbit checkout, life support evaluations, and hab equipment evaluations

      • Trans-lunar injection (TLI) initiated

      • Outbound transit to Moon; travel time approximately 4 days

      • Lunar flyby at an altitude of 4,047 mi (6,513 km)

      • Return trajectory corrections as needed for Earth's atmosphere

      • Crew module separation from service module

      • Entry interface into Earth’s atmosphere

      • Splashdown for astronaut recovery

Artemis Program Overview

  • Artemis I (2022): Uncrewed test of SLS and Orion capsule

  • Artemis II (Scheduled for Feb 2026): Crewed flight beyond the Moon

  • Upcoming Artemis Missions:

    • Artemis III (Mid-2027): First crewed Moon landing since Apollo 17 using SpaceX's Starship HLS

    • Artemis IV (Sept 2028): Delivery of Gateway lunar space station core module and another crewed Moon landing

    • Artemis V (March 2030): Expansion of the Gateway station and a third crewed landing using Blue Origin's Blue Moon lander

U.S. Presence and Competition

  • Objective: Establishing permanent US presence near the moon

  • Competition: China aims for a manned lunar landing in 2030, raising the question of a new space race.

  • Critical Bottleneck: Development of Lunar landers by private companies.

Properties and Nature of Light

Importance of Light

  • Primary Tool in Astronomy: Light is crucial for understanding stellar properties such as velocity, temperature, and chemical composition.

  • Transport Mechanism: Light is the primary means for energy transport throughout the universe (e.g., sunlight warming Earth).

Definition of Light

  • Electromagnetic Radiation: Light is a disturbance in an electric field that creates a corresponding magnetic field, resulting in the transfer of energy.

Light Behavior

  • Wave-Particle Duality:

    • Light is described both as a wave and a particle, depending on the phenomenon in study.

    • Example: NIRSpec on the James Webb Space Telescope utilizes wave properties through a spectrograph and captures light as photons in a digital camera.

Wave Behavior of Light

Wave Properties

  • Compares light behavior to waves in water:

    • A pebble's impact on a pond creates ripples that transfer energy without the water molecules moving outward.

  • Energy Transfer: Light waves transfer energy similar to water waves.

Electromagnetic Fields and Light

  • Charged Particles Influence: Protons and electrons create electromagnetic fields.

  • Movement of Charge: A moving charge results in oscillation of the electric field, generating light waves that travel perpendicularly to the field direction.

Light Traveling Through Space

  • Traveling Medium: Unlike sound or water waves, light does not require a medium to travel.

  • Speed of Light:

    • Travels in a vacuum at a constant speed of c=299,792,458extm/sc = 299,792,458 ext{ m/s}.

    • Einstein’s Theory of Relativity: Establishes that nothing can travel faster than the speed of light.

Wavelength and Frequency of Light

Definitions

  • Wavelength (λ): Distance between successive crests in a wave.

  • Frequency (f): Number of wave crests passing a point per second, measured in Hertz (Hz). Denoted by ff or sometimes using the Greek letter <br>u<br>u.

  • Relation Between Speed, Wavelength, and Frequency:
    c=<br>uimesextλc = <br>u imes ext{λ}

  • Implications: Longer wavelengths correspond to lower frequencies and vice versa.

Photons

  • Photons: Light also resembles particles termed photons, characterized by energy directly proportional to frequency.

  • **Photons travel at speed cc (3.00 x 108extm/s10^{8} ext{ m/s}).

Energy of Photons

Formula

  • Energy of a photon is expressed as:
    Eextphoton=hfE_{ ext{photon}} = h f
    where hh is Planck's constant (h=6.626x10−34extJsh = 6.626 x 10^{-34} ext{ J s}).

  • Alternate form:
    Eextphoton=rachcextλE_{ ext{photon}} = rac{h c}{ ext{λ}}

Photoelectric Effect

Description

  • When light hits metal, it can free electrons, termed photoelectrons.

  • The photon energy correlates to light frequency; this phenomenon supported the particle nature proposed by Einstein in 1905, and was confirmed experimentally in 1914.

Review Questions

  • Comparing lasers: A red laser at 650 nm and a green laser at 532 nm.

    • Possible assertions include the speed and frequency relationship between red and green light.

Light & Color Perception

Wavelength and Color

  • Longer wavelengths (red) correspond to lower frequencies, and shorter wavelengths (violet) correspond to higher frequencies.

  • White Light: Mixture of wavelengths, can be split with a prism, then recombined with a lens.

Spectroscopy

Analyzing Spectra

  • Spectrum Measurement: Measures light intensity as a function of wavelength and depicts brightness at each detected wavelength.

  • Measurement Units: Wavelength is often expressed in nanometers (nm), where 1extnm=10−9extm1 ext{ nm} = 10^{-9} ext{ m}.

  • Visible light spectrum: Only a small portion of the electromagnetic spectrum; other wavelengths include X-rays and radio waves.

Special-Telescopes

  • Designed for different electromagnetic spectrum parts:

    • Chandra Space Telescope: X-ray

    • Hubble Space Telescope: Visible

    • Spitzer Space Telescope: Infrared

    • Arecibo Observatory: Radio

X-ray vs Blue Light

Energy Comparison

  • X-ray photon example with energy of 2800 eV vs blue light photon at 2.8 eV. This relationship indicates differences in penetration and wavelength calculations based on formulas for light speed and energy.

Nature of Matter

Atomic Structure

  • Composition: Nucleus contains protons (positive) and neutrons (neutral); electrons (negative) orbit the nucleus at variable distances.

  • Forces at Play: The electrical attraction holds electrons in orbit.

Quantum Mechanics and Electron Behavior

Electron Orbitals

  • Electrons do not have a fixed path; they occupy probability clouds around the nucleus termed orbitals.

  • Quantized States: Orbitals exist only at specific energy levels, transitioning requires energy input or release.

  • Absorption and Emission: When electrons absorb photons that match their energy difference, they become excited; emission occurs when they drop to lower energy levels, releasing photons.

Chemical Elements and Spectra

Identification via Spectra

  • Elements are identified through their unique emission or absorption spectra, resulting from their atomic composition.

  • This enables astronomers to determine elemental composition of distant objects based on light analysis.

Wrapping Up: Homework and Activities

  • Readings: Assigned textbook Chapter 5.4 for the next lecture.

  • Homework:

    • Quiz #2 due Thursday

    • Discussion section exercises due one week after meeting.

    • Math Review assignments due Mon-Tues.

    • Celestial Motions assignments due Wed-Fri.

  • Public Observations: Washburn Observatory nights scheduled every other Wednesday, weather permitting.