STEM for TY TeachersDiscovering Our Place in the UniverseDay 2Mark Bailey and Libby McKearney, Armagh Observatory
H&S, Housekeeping etc. • This is a non-smoking building • Morning tea and lunch will be served: • Fire alarm, fire escapes – I will lead you to our fire assembly point, please remain there until I check your name off the register and only return here when advised to do so. • Please be aware of any trip hazards (trailing leads, steps etc.) • Location of facilities • Evaluation – please continue to fill out your evaluation form as we go through today and tomorrow! • Second form on your table.
Reminder: Main Learning Objective To provide TY Teachers/Coordinators with sufficient knowledge of astronomy and related sciences to give them the confidence and skills to introduce some aspects of astronomy to their TY students.
“Earth’s Place in Space: Bringing ‘Heaven’ Down to Earth”Talk by Mark Bailey
Moon: Relative Size and Phases Moon’s diameter (3476 km) is 27%, i.e. roughly one quarter, that of the Earth Lunar phases depend on relative positions of Earth, Moon and Sun as both Earth and Moon revolve around the Sun … From RAS Leaflet Images from NASA
Moon: Orbit Always Concave With Respect to Sun Heliocentric View New Moon Last Quarter Full Moon First Quarter Geocentric View
Orbit Around Common Centre of Mass: Produces Two Tidal Bulges From RAS Leaflet From McCully “Beyond The Moon”
Core Theme 4Sun, Stars and Galaxies Sun as a star; formation and origin of stars, composition etc.; exo-planetary systems; other stars (single, binary etc.); star clusters; galaxies; galaxy clusters etc.; and the Universe (cosmology and new ideas).
Sun, Stars and Galaxies The Nature of the Sun and Other Stars; Stellar Evolution; the Content and Structure of Galaxies and the Universe as a Whole…
Different Types of Stars • Main-Sequence Stars - Young Stars:These stars produce energy through nuclear fusion as they convert Hydrogen to Helium. Most stars (about 90%) are Main-Sequence Stars. For these stars, the hotter they are, the brighter they are. The Sun is a typical Main-Sequence star. • Dwarf Stars: The name “dwarf” can be used to describe stars like our Sun, or tiny (Earth-size) “white dwarfs”, the compact remnants of stars like our Sun. Some main-sequence stars can be up to 20 times more massive than our Sun and much brighter. • Yellow Dwarf Stars: Yellow dwarfs are main-sequence stars like the Sun.
Red Dwarf:The term “red dwarf” usually refers to a small, cool, very faint, main-sequence star whose surface temperature is under about 4,000 K. Red dwarfs are the most common type of star. Proxima Centauri is a red dwarf. • Giant and Supergiant Stars – Evolved, Large Stars • Red Giant: A red giant is a relatively old star whose diameter is about 100 times bigger than it was originally, and has become cooler (the surface temperature is under 6,500 K). They are frequently orange in colour. Betelgeuse is a red giant. It is about 20 times as massive as the Sun, but about 14,000 times brighter than the Sun, and about 600 light-years from Earth.
Blue Giant:A blue giant is a huge, very hot, blue star. It is a post-main sequence star that burns helium. • Supergiant: A supergiant star is the largest known type of star; some are almost as large as our entire solar system. Betelgeuse and Rigel are supergiants. These stars are rare. When supergiants die they explode as a supernova and may produce black holes.
Faint, Virtually Dead Stars: • White Dwarf: A white dwarf is a small, very dense, hot star that is often made mostly of carbon. These faint stars are what remain after a red giant star loses its outer layers. Their nuclear cores are depleted. • They are about the size of the Earth (but around 200,000 times more massive). They will eventually lose their heat and become a cold, dark black dwarf. Our Sun will someday turn into a white dwarf and then ultimately a black dwarf. The companion of Sirius is a white dwarf.
Brown Dwarf: A brown dwarf is a "star" whose mass is too small to have nuclear fusion occur at its core (the temperature and pressure at its core are insufficient for fusion). A brown dwarf is not very luminous. It is usually regarded as having a mass between approximately 1/100 and 1/10 that of the Sun. • Neutron Star:A neutron star is a very small, super-dense star which is composed mostly of tightly-packed neutrons. It has a thin atmosphere of hydrogen. It has a diameter of approximately 10 km and a density of roughly ten million billion times that of water. • Pulsar:A pulsar is a rapidly spinning neutron star with a very powerful magnetic field that emits energy in a very narrow beam as it rotates, leading – like a lighthouse – to intense pulses of observed radiation.
Binary Stars: Many stars are found in pairs (binaries) or multiple systems. • Double Star: A double star is two stars that appear close to one another in the sky. Some are true binaries (two stars that revolve around their common centre of mass); others just appear double because they happen to lie along the same line-of-sight from Earth. • Binary Star:A binary star is a system of two stars that revolve around their common centre of mass (the barycentre). About half of all stars are in a group of at least two stars. Polaris (the pole star of the Northern Hemisphere of Earth) is part of a binary star system.
Neutron Stars and Pulsars: Even More Extreme Matter Roughly same mass as the Sun (2 x 1030 kg); roughly same size as Halley’s comet!
Eclipsing Binary:An eclipsing binary is two stars that appear to be a single star varying in brightness. The variation in brightness is due to the stars periodically obscuring or enhancing one another. Such binary star systems happen to be tilted (with respect to us) so that their orbital plane is viewed from the edge rather than face-on. • X-ray Binary Star: X-ray binary stars are a special type of binary star in which one of the stars is a compact, evolved object such as a white dwarf, neutron star, or black hole. As matter is stripped from the normal star, it falls at very high speed onto the collapsed star, producing X-rays.
Variable Stars - Stars that Vary in Luminosity: Many stars, even the Sun, can vary in luminosity. Some change their light output by a very significant amount in a regular way and can therefore be recognized at very great distances. These can be used as “standard candles” to estimate distances. • Cepheid Variable Stars:Cepheid variables are very luminous stars that regularly pulsate in size and change in brightness. As the star rapidly increases in size, its brightness increases; then, it slowly decreases in size again, and its brightness falls. • Because of their intrinsic luminosity Cepheid stars can be seen millions of light years away and used to calibrate the distance scale of the Universe. Polaris and Delta Cephei are examples of Cepheids. End of star types.
Nova and Supernova • A supernova is a stellar explosion that is more energetic than a nova. Plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months. • During this short interval a supernova can radiate as much energy as the Sun is expected to emit over its entire life span. The explosion expels much or all of a star's material at a velocity of up to 30,000 km/s (10% of the speed of light), driving a shock wave into the surrounding interstellar medium. This shock wave produces an expanding shell of gas and dust called a supernova remnant.
Nova (plural novae) means "new" in Latin, referring to what appears to be a new star shining in the celestial sphere. • Although no supernova has been observed in the Milky Way since 1604, the number of supernova remnants indicates that on average such an event occurs about once every 50 years in the Milky Way. • Supernovae play a significant role in enriching the interstellar medium with the heaviest elements. Furthermore, the expanding shock waves from supernova explosions can trigger the formation of new stars.
EXO Planets • Exoplanets: an extrasolar planet or exoplanet, is a planet outside the Solar System. By early 2012, more than 700 extrasolar planets (in 571 planetary systems and 81 multiple-planet systems) have already been identified. • A substantial fraction of stars have planetary systems - data from the HARPS mission indicates that this includes more than half of all Sun-like stars. Data from the Kepler mission has been used to estimate that there are at least 50 billion planets in our own Galaxy. The first confirmed detection was in 1992.
Other life?!! • Children will ask! • ET? • Recent US citizens’ petition to reveal if their government really knew anything about aliens on Earth – “No”! • The discovery of extra-solar planets has intensified interest in the possibility of extraterrestrial life. Scientists look for the signature of water or chemicals which may sustain or indicate life. Posters on various web-sites (e.g. Observatory).
Nebulae “Pillars of Creation” in the Eagle Nebula
Orion Nebula and Proplyds Space Telescope image of protoplanetary discs in Orion Nebula Orion Nebula imaged from Armagh (Simon Jeffery)
Nebula – often very beautiful images!A nebula (from Latin: "cloud" pl. nebulae), is an interstellar cloud containing largely hydrogen, helium and other gases, as well as interstellar dust. Originally, nebula was a general name for any extended astronomical object, including galaxies beyond the Milky Way (some examples of the older usage survive; for example, the Andromeda Galaxy is still described as the Andromeda Nebula. • Nebulae often form star-forming regions, such as in the Eagle Nebula. This nebula is depicted in one of NASA's most famous images, the "Pillars of Creation". In these regions the formations of gas, dust, and other materials "clump" together to form larger masses, which attract further matter, and eventually become massive enough to form stars. The remaining materials are then believed to form planets, and other planetary system objects.
Galaxy Types:Galaxies come in various sizes and shapes. They can have as few as 10 million stars or as many as 10 trillion. (The Milky Way has about 200 billion stars). In 1936, Edwin Hubble classified galaxy shapes in the Hubble Sequence.
Elliptical: These have a faint, rounded shape, but they're largely devoid of star-forming gas and dust, with no visible bright stars or spiral patterns. Elliptical galaxies probably comprise about 60 percent of the galaxies in the Universe. They show a wide variation in size - most are small (about 1 percent the diameter of the Milky Way), but some are many times larger. • Spiral: The Milky Way is one of the larger spiral galaxies. They're bright and distinctly disk-shaped, with star-forming gas, dust and bright stars in the spiral arms. Because spiral galaxies are bright, they make up most of the visible galaxies, but they're thought to make up only about 20 percent of the galaxies in the Universe.
Irregular: These are small, faint galaxies with large clouds of gas and dust, but often no spiral arms or bright centres. Irregular galaxies contain a mixture of old and new stars and many tend to be small, about 1 percent to 25 percent of the Milky Way's diameter. • Some more galaxy images: Spiral galaxy M31 in Andromeda Giant elliptical galaxy Centaurus A
Gravity • Every time you jump, you experience gravity. It pulls you back down to the ground. Without gravity, you'd float off into the atmosphere along with all of the other matter on Earth. • You see gravity at work any time you drop a book, step on a scale or toss a ball up into the air. It's such a constant presence in our lives, we seldom marvel at the mystery of it but even with several well-received theories out there attempting to explain why a book falls to the ground (and at the same rate as a pebble or a couch, at that), they're still just theories. The ultimate cause of gravity remains a mystery.
So what do we know about gravity? We know that it causes any two objects in the Universe to be drawn to one another. We know that gravity assisted in forming galaxies and other structures in the known Universe, that it keeps the Moon in orbit around the Earth and so on. • As for the science behind the action, we know that Isaac Newton defined gravity as an attractive force, one that attracts all objects to all other objects. However, Albert Einstein said that gravity is the result of the curvature of space-time. These two theories are the most common and widely held (if incomplete) explanations of gravity.
The Expanding Universe!! • The Expanding Universe, the theory developed from the observed correlation between the red shifts of celestial bodies and their distances, suggests that the space between galaxies is expanding. This causes distant galaxies to appear to be moving away from us with a speed that increases with distance, just like the separation of dots on a balloon as you blow it up. • Cosmology is the discipline that deals with the origin, structure, and space-time relationships of the Universe. Cosmologists study the Universe as a whole: its birth, growth, shape, size and eventual fate. Modern cosmology is dominated by the Big Bang theory, which brings together observational astronomy and particle physics.
The Big Bang theory is the prevailing cosmological model that explains the early development of the Universe. According to the Big Bang theory, the Universe was once in an extremely hot and dense state which expanded rapidly. This rapid expansion caused the young Universe to cool and resulted in its present continuously expanding state. According to recent measurements, observations and scientific evidence, this original state existed around 13.7 billion years ago, which is currently considered as the age of the known Universe. Prior to the hot stage of the Big Bang, a very short-lived earlier stage of Inflation is thought to have occurred. End of presentation.