* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Great Observatories Origins Deep Survey (GOODS) Observation
Leibniz Institute for Astrophysics Potsdam wikipedia , lookup
Formation and evolution of the Solar System wikipedia , lookup
X-ray astronomy satellite wikipedia , lookup
Astrobiology wikipedia , lookup
Corvus (constellation) wikipedia , lookup
Wilkinson Microwave Anisotropy Probe wikipedia , lookup
Dialogue Concerning the Two Chief World Systems wikipedia , lookup
Extraterrestrial life wikipedia , lookup
Dyson sphere wikipedia , lookup
Shape of the universe wikipedia , lookup
Equation of time wikipedia , lookup
International Year of Astronomy wikipedia , lookup
Fine-tuned Universe wikipedia , lookup
Astronomy in the medieval Islamic world wikipedia , lookup
Outer space wikipedia , lookup
Constellation wikipedia , lookup
Geocentric model wikipedia , lookup
Flatness problem wikipedia , lookup
Dark energy wikipedia , lookup
Celestial spheres wikipedia , lookup
Armillary sphere wikipedia , lookup
Expansion of the universe wikipedia , lookup
Epoch (astronomy) wikipedia , lookup
Astrophotography wikipedia , lookup
Astronomical unit wikipedia , lookup
International Ultraviolet Explorer wikipedia , lookup
Archaeoastronomy wikipedia , lookup
Non-standard cosmology wikipedia , lookup
Observable universe wikipedia , lookup
Hubble Deep Field wikipedia , lookup
Physical cosmology wikipedia , lookup
History of astronomy wikipedia , lookup
Chinese astronomy wikipedia , lookup
Theoretical astronomy wikipedia , lookup
Tropical year wikipedia , lookup
WELCOME TO ASTRO330 Special Topics in Astrophysics Fall 2016 Image of the deep space, up to ~1/2 billion year after the Big Bang, taken with the Hubble Space Telescope Contact Information • Dr. Mauro Giavalisco: – Room LGRT-B 520; phone: 413-545-4767 – Office Hours: T/T 2:00 – 3:00, or by appointment – Email: [email protected] Philosophy of the Course • This course consists of some carefully selected topics in astrophysics. It focuses on practical issues, as well as on current research and open questions, mostly in extragalactic research. These will include: – Observations; telescopes, instrumentation, data reduction – Modern astronomical practice: photometry, morphology, properties of sources – Review of current research and open questions: cosmology, star formation and galaxy evolution, cosmic structures, the dark sector (matter and energy) • The goal is to discuss modern astronomical facilities and practice, as well as the state of current research so that if you choose astronomy as a profession, you know what is going on in today’s research (at least in extragalactic astronomy). It probably is the first time you are exposed to what is currently going on in astronomy. • While the course covers both theoretical and observational issues, it focuses on how to measure the relevant physical properties, and it provides guidelines on how to carry out astronomical observations, use the data and interpret them. Format of the Course • Course material will be covered in two weekly lessons (Mo/We), 1hr15m long; studying from my notes and selected papers, texts. • It includes homework. • The syllabus of the course will soon be online, together with most of the material covered in class. The Web site is: www.astro.umass.edu/~mauro/astro330 • Ample opportunity for interactions: ASK QUESTIONS, when you need to. REMEMBER: – there are no stupid questions, except one: the one you never dared to ask! – (there are stupid answers, however). • This is critical: do not hesitate to seek help if you feel you are lagging behind! – Past a given point, you will not be able to catch up and you will be lost and fail the course. • My ultimate goal is to make you a competitive, independent scientist, capable to conduct quantitative creative, hopefully innovative, research. Course Requirements • Grades: will be assigned on a modified straight scale. Scores will be adjusted upward if the assignments/exams are too hard • Guaranteed minimum grade: – – – – – A: A-: B: B-: C: 92% 87% 82% 77% <72% • Totals of components of Final Grade – Final project:………………….………... 40% – Homework:…………………..………… 20% – Term Papers or Research Projects:…….. 40% We have made tremendous progress in understanding the evolution of the universe: the Big Bang theory t=0: the cosmic expansion begins from a singularity. The density of energy and mass and the temperature are infinite. The universe keeps expanding at a very fast rate and cools down t≈500,000 years: the earliest visible universe: the cosmic background The dark age t≈200,000,000: the first stars, black holes and galaxies form, the first sources of light appear t=13.8 billion years: today. The cosmic temperature is 2.7 K But together with some answers, we also got new, more profound questions: e.g. dark matter and dark energy Most of the mass of galaxies is in the form of dark matter Luminous matter amounts to only ≈10% What is it? Theiry DOES NOT predict it! Time in billions of years 0.5 2.2 5.9 8.6 13.8 35 70 93 140 Quantum fluctuations 13 D.M. is key to explain the universe: simulations show that the gravity of dark matter pulls mass into denser regions – universe grows lumpier with time, and the simulated structures are very similar to the observed ones dr/r grows ~a(t): from z ~1,100 to today increased 1,000 times Structures in galaxy maps are quantitatively very similar to the ones found in simulations dark matter dominated universe Dark energy: evidence in the accelerated expansion of the universe Brightness of distant white-dwarf supernovae tells us how much universe has expanded since they exploded because their luminosity at peak is ≈the same Accelerating universe is best fit to supernova data Dark Energy is what accelerates the expansion. But what is it? Big mystery: no theory can predict it Astronomy refresher: when we look at the universe, what we see is sources on the Celestial Sphere To make physical sense of the universe we need to unambiguously measure positions of sources in space. Celestial objects at different distances all appear projected on the celestial sphere. All we can really measure directly are angular positions on the celestial sphere. The measure of distance (i.e. radial distance to the source) is one of the greatest problems of astronomy. (the other is the measure of mass) Angular Measurements (just in case…) • Full circle = 360º = 2p • 1º = 60 (arcminutes) • 1 = 60 (arcseconds) •1 radian (p) = 57.2957795º = 3,437.74677 = 206,264.806 Review: Coordinates on the Earth (spherical) • Latitude: position north or south of equator • Longitude: position east or west of prime meridian (runs through Greenwich, England) Our view from Earth: • Stars near the north celestial pole are circumpolar and never set. • We cannot see stars near the south celestial pole. • All other stars (and Sun, Moon, planets) rise in east and set in west. A circumpolar star never sets Celestial Equator Your Horizon This star never rises The sky varies with latitude but not longitude. Length of a Day • Solar day: defined respect to the Sun. The Sun makes one circuit around the sky in 24 hours Length of a Day • Sidereal day: defined respect to distant stars. Earth rotates once on its axis in 23 hrs, 56 min, and 4.07 sec. Length of a Day • Solar day is longer than a sidereal day by about 1/360 because Earth moves about 1° in orbit each day Mean Solar Time • Length of an apparent solar day changes during the year because Earth’s orbit is slightly elliptical. • Mean solar time is based on the average length of a day. • Noon is average time at which Sun crosses meridian • It is a local definition of time Universal Time (by the Sun) • Universal time (UT or UTC) is defined to be the mean solar time at 0° longitude. • It is also known as Greenwich Mean Time (GMT) because 0° longitude is defined to pass through Greenwich, England • It is the standard time used for astronomy and navigation around the world • Also, commonly referred to as the “Zulu Time” Our Position around the Sun • As the Earth orbits the Sun, the Sun appears to move eastward along the ecliptic. • At midnight, the stars on our meridian are opposite the Sun in the sky. How do we locate objects on the celestial sphere? Insert TCP 5e Figure S1.8 • Coordinate the space by means of static reference points in the sky. • Four such (quasi) static points are the equinoxes and solstices. • We use the Spring Solstice as the zero point of one coordinate. • CAUTION! The solstice actually precesses (50/yr), thus one MUST specify the year. • The 1950 Equinox and the 2000 Equinox (J2000) are the most commonly used (the J2000 is the most widely adopted one). • Too many astronomers have pointed the telescope to the wrong place because they did not pay attention to the year of the equinox!!! Solstices & Equinoxes Celestial Coordinates • Right ascension: Like longitude on celestial sphere (measured in hours with respect to spring equinox). • Declination: Like latitude on celestial sphere (measured in degrees above celestial equator) Time by the Stars • Sidereal Time is the time measured from meridian passage, in units of the sidereal day (i.e. dividing the S.D. in 24 hr, then min, then sec). Sidereal time < Solar time • The local sidereal time is 0h0m when the spring equinox passes through the meridian • Sidereal time is equal to right ascension that is passing through the meridian • A star’s hour angle is the time since it last passed through the meridian Local sidereal time = RA + hour angle Example: Celestial Coordinates of Vega • Right ascension: Vega’s RA of 18h35.2m (out of 24h) places most of the way around celestial sphere from spring equinox. • Declination: Vega’s dec of +38°44’ puts it almost 39° north of celestial equator (negative dec would be south of equator) Unit of length in astronomy: the parsec When is p=1 arcsec, D = 1 parsec (pc) 1 pc = 3.806x1018 cm It takes light 3.26 years to cover 1 pc Imaging: what is an image? Near-Infrared image, about 2,200 nm An image is a spatial map of the intensity of light from a source, at some wavelength recorded on a detector (array of photosensitive elements or “pixels”) The detector records the spatial distribution of light intensity at the position of each pixel PIXEL: the smallest element of the image that the camera can record Imaging: filters Images of astronomical sources are always taken through some passband (filter). The filter lets only some wavelengths to pass and reach the detector, and blocks all the other. The idea is to image the source only in the selected range of wavelengths The purposes of imaging are 1) measure the amount of light emitted (photometry) 2) obtain the morphology NOTE: due to motion or redshift, the observed wavelength DOES NOT correspond to the rest-frame wavelength M. Giavalisco Cosmological redshift: Light needs time to travel across large volumes of space. During this time the expansion of the universe continues The apparent wavelength of light is increased as it travels through an expanding space The observed wavelength λo is longer than the emitted wavelength λe The redshift parameter z: λo = λe x (1+z) The effect of redshift M. Giavalisco 34 Image Quality (resolution) Diffraction limit: the image of point source through an optical system has a finite size, the Airy disk: 2αA 84% of energy Sharp telescopes have thin PSF’s HST with spherical aberration (flowed mirror) HST after the repair Images with bad (left) and good (right) PSF HST with flawed mirror HST after the repair On the ground, image quality is limited by atmospheric seeing Typical optical seeing: FWHM = 0.5 – 1.5 arcsec 1.0 typical 0.3 exceptionally good 3.0 exceptionally bad Image quality DOES the trick!! To study faint galaxies both space-based sensitivity and angular resolution required!! Note how many more details and faint objects can be observed with the HST Subaru + SUPREME HST + ACS