PHYS 3380 Astronomy A potentially habitable world orbiting

PHYS 3380 - Astronomy A potentially habitable world orbiting Proxima Centauri, closest star to Earth, was discovered in 2016 using the radial velocity method • Proxima Centauri is a cool red-dwarf slightly older than the Sun Proxima b • minimum mass 1. 3 times that of Earth • suggests a rocky composition • radius between 0. 8 and 1. 4 Earth radii • 11. 2 -day orbit • receives 70% the energy Earth receives from the Sun • equilibrium temperature 227 K • ESI of 0. 87 Probably tidally locked • illuminated side might be too hot - dark side too cold for liquid water or life • thick atmosphere or a large ocean, though, could regulate the temperatures across the planet Most red dwarfs are very active • strong magnetic fields, flares, and high UV and X-ray fluxes • may lead to the atmospheric and water loss, high radiation • magnetic field could potentially provide a shield Ø Either a lucky find or these worlds are more common than previously thought Ø Close enough to Earth for detailed studies in the next years Ø Perhaps a goal for projects like Star. Shot

PHYS 3380 - Astronomy In 2013, Kepler lost the second of its four reaction wheels, rendering it incapable of maintaining precision pointing in three dimensions. Engineers devised a remarkable solution: using the pressure of sunlight to stabilize the spacecraft so it could continue to do science. The K 2 mission began in Mar 2016 The K 2 Mission

PHYS 3380 - Astronomy The Transiting Exoplanet Survey Satellite (TESS) • Launched on April 18, 2018, aboard a Space. X Falcon 9 rocket. • Searching for exoplanets using the transit method like Kepler. • Will survey 200, 000 of the brightest stars near the sun to search for transiting exoplanets. • Will survey the entire sky over the course of two years by breaking it up into 26 different sectors, each 24 degrees by 96 degrees across. • The stars TESS will study are 30 to 100 times brighter than those the Kepler mission and K 2 follow-up surveyed, which will enable far easier follow-up observations with both ground-based and space-based telescopes. • will also cover a sky area 400 times larger than that monitored by Kepler. • So far has found 2240 candidates and 68 confirmed exoplanets

PHYS 3380 - Astronomy Lenses and Mirrors

PHYS 3380 - Astronomy ISNS 4371 Phenomena of Nature Properties of Light Law of Reflection - Angle of Incidence = Angle of reflection Law of Refraction - Light beam is bent towards the normal when passing into a medium of higher Index of Refraction. Light beam is bent away from the normal when passing into a medium of lower Index of Refraction. index of Refraction - Inverse square law - Light intensity diminishes with square of distance from source.

PHYS 3380 - Astronomy Law of Reflection Normal Angle of incidence ( ) = angle of reflection ( ) The normal is the ray path perpendicular to the mirror’s surface.

PHYS 3380 - Astronomy Geometry of a Concave Mirror Focus Principal axis Vertex Focal length Center of curvature - the center of the circle of which the mirror represents a small arc Principal axis - a radius drawn to the mirror surface from the center of curvature of the mirror - normal to mirror surface Focus - the point where light rays parallel to principal axis converge; the focus is always found on the inner part of the "circle" of which the mirror is a small arc; the focus of a mirror is one-half the radius Vertex - the point where the mirror crosses the principal axis Focal length - the distance from the focus to the vertex of the mirror

PHYS 3380 - Astronomy Index of Refraction As light passes from one medium (e. g. , air) to another (e. g. , glass, water, plexiglass, etc…), the speed of light changes. This causes to light to be “bent” or refracted. The amount of refraction is called the index of refraction.

PHYS 3380 - Astronomy Refraction Imagine that the axles of a car represent wave fronts. If the car crosses from a smooth to a rough surface at an angle, one tire of the axle will slow down first while the other continues at normal speed. With one tire traveling faster the other, the car will turn in the direction of the slow tire. This is how refraction works.

PHYS 3380 - Astronomy AIR Car GLASS / WATER Slower Propagating Speed ( Sand /Gravel)

PHYS 3380 - Astronomy AIR Car GLASS / WATER Slower Propagating Speed ( Sand / Gravel )

PHYS 3380 - Astronomy AIR NORMAL GLASS / WATER Slower Propagating Speed

PHYS 3380 - Astronomy NORMAL LIGHT BENDING TOWARDS THE NORMAL AIR LIGHT RAY GLASS / WATER Slower Propagating Speed

PHYS 3380 - Astronomy NORMAL LIGHT BENDING TOWARDS THE NORMAL AIR n 1 Snell's Law ( Next Slide ) n 2 GLASS / WATER Slower Propagating Speed

PHYS 3380 - Astronomy Snell's Law Where: VL 1 is the longitudinal wave velocity in material 1. VL 2 is the longitudinal wave velocity in material 2. Snell's Law describes the relationship between the angles and the velocities of the waves. Snell's law equates the ratio of material velocities VL 1 and VL 2 to the ratio of the sine's of incident and refracting angles.

PHYS 3380 - Astronomy Snell's Law n=(c/v) where : C is the velocity of light and v is the velocity of light in that medium where 1 and 2 are the angles from the normal of the incident and refracted waves, respectively. n 1, n 2 are indices of refraction of the two media respectively.

PHYS 3380 - Astronomy ( Sand / Gravel ) Slower Propagating Speed GLASS / WATER Car AIR

PHYS 3380 - Astronomy ( Sand / Gravel ) Slower Propagating Speed GLASS / WATER Car AIR

PHYS 3380 - Astronomy ( Sand / Gravel ) Slower Propagating Speed GLASS / WATER Car AIR

PHYS 3380 - Astronomy Slower Propagating Speed GLASS / WATER NORMAL AGAIN, LIGHT BENDS TOWARDS THE NORMAL upon entering a region with slower speed. LIGHT RAY AIR

PHYS 3380 - Astronomy AIR Car ( Sand / Gravel ) GLASS /WATER Slower Propagating Speed

PHYS 3380 - Astronomy AIR Car ( Sand / Gravel ) GLASS /WATER Slower Propagating Speed

PHYS 3380 - Astronomy AIR Car ( Sand / Gravel ) GLASS /WATER Slower Propagating Speed

Snell's Law PHYS 3380 - Astronomy LIGHT RAY NOW LIGHT BENDS AWAY FROM THE NORMAL GLASS /WATER Slower Propagating Speed AIR NORMAL

PHYS 3380 - Astronomy Geometry of a Converging (Convex) Lens Focus Optical axis Focal length Optical axis - axis normal to both sides of lens - light is not refracted along the optical axis Focus - the point where light rays parallel to optical axis converge; the focus is always found on the opposite side of the lens from the object Focal length - the distance from the focus to the centerline of the lens

PHYS 3380 - Astronomy Types of Optical Telescopes

PHYS 3380 - Astronomy Refracting Telescope Uses lens to focus light from distant object - the eyepiece contains a small lens that brings the collected light to a focus and magnifies it for an observer looking through it.

PHYS 3380 - Astronomy The largest refracting telescope in the world is the at the University of Chicago’s Yerkes Observatory - it is 40 inches in diameter and 63 feet long.

PHYS 3380 - Astronomy Reflecting Telescope The primary mirror focuses light at the prime focus. A camera or another mirror that reflects the light into an eyepiece is placed at the prime focus.

PHYS 3380 - Astronomy Types of Reflecting Telescopes Each design incorporates a small mirror just in front of the prime focus to reflect the light to a convenient location for viewing.

PHYS 3380 - Astronomy The Keck Telescopes Keck telescopes on Mauna Kea in Hawaii. 36 hexagonal mirrors function as single 10 -meter mirror. Largest in the world is the Gran Telescopio Canarias in the Canary Islands which began operations in May 2009 – 10. 4 m. The European Extremely Large Telescope (E-ELT) is planned to have first light in 2025. The E-ELT will measure close to 40 meters in diameter

PHYS 3380 - Astronomy The Hubble Space Telescope is 43. 5 ft long and weighs 24, 500 lbs. Its primary mirror is 2. 4 m (7 ft 10. 5 in) in diameter.

PHYS 3380 - Astronomy Focus Optical axis Focal length Remember: the focus is the point where light rays parallel to optical axis converge and the focal length is the distance from the focus to the centerline of the lens

PHYS 3380 - Astronomy Geometry of a Simple Lens l 2 Focal Plane l 1 f o i The focal plane is where incoming light from one direction and distance (object distance o greater than focal length) is focused. Lens formula Linear Magnification Using the Gaussian form of the lens equation, a negative sign is used on the linear magnification equation as a reminder that all real images are inverted

PHYS 3380 - Astronomy The image formed by a single lens is inverted.

PHYS 3380 - Astronomy Focal Plane Focal length

PHYS 3380 - Astronomy The Eye The eye consists of pupil that allows light into the eye - it controls the amount of light allowed in through the lens - acts like a simple glass lens which focuses the light on the retina - which consists of light sensitive cells that send signals to the brain via the optic nerve. An eye with perfect vision has its focus on the retina when the muscles controlling the shape of the lens are completely relaxed - when viewing an object far away - essentially at infinity. Farsightedness/Nearsightedness - focus behind/in front of the retina

PHYS 3380 - Astronomy When viewing an object not at infinity, the eye muscles contract and change the shape of the lens so that the focal plane is at the retina (in an eye with perfect vision). The image is inverted as with a single lens - the brain interprets the image and rights it.