This Restless Globe
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Constructing a Galactic Coordinate System Based on Near-Infrared and Radio Catalogs
A&A 536, A102 (2011) Astronomy DOI: 10.1051/0004-6361/201116947 & c ESO 2011 Astrophysics Constructing a Galactic coordinate system based on near-infrared and radio catalogs J.-C. Liu1,2,Z.Zhu1,2, and B. Hu3,4 1 Department of astronomy, Nanjing University, Nanjing 210093, PR China e-mail: [jcliu;zhuzi]@nju.edu.cn 2 key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education, Nanjing 210093, PR China 3 Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, PR China 4 Graduate School of Chinese Academy of Sciences, Beijing 100049, PR China e-mail: [email protected] Received 24 March 2011 / Accepted 13 October 2011 ABSTRACT Context. The definition of the Galactic coordinate system was announced by the IAU Sub-Commission 33b on behalf of the IAU in 1958. An unrigorous transformation was adopted by the Hipparcos group to transform the Galactic coordinate system from the FK4-based B1950.0 system to the FK5-based J2000.0 system or to the International Celestial Reference System (ICRS). For more than 50 years, the definition of the Galactic coordinate system has remained unchanged from this IAU1958 version. On the basis of deep and all-sky catalogs, the position of the Galactic plane can be revised and updated definitions of the Galactic coordinate systems can be proposed. Aims. We re-determine the position of the Galactic plane based on modern large catalogs, such as the Two-Micron All-Sky Survey (2MASS) and the SPECFIND v2.0. This paper also aims to propose a possible definition of the optimal Galactic coordinate system by adopting the ICRS position of the Sgr A* at the Galactic center. -
Constellations with Prominent Stars That Can Be Found Near the Meridian at 10 Pm on January 15
ONSTELLATIONS C Altitude Ruler The rotation of the Earth on its axis causes the stars to rise and set each evening. In addition, the orbit of the Earth around the Sun places different regions of the sky in our Horizon night-time view. The PLANISPHERE is an extremely useful tool for finding stars and 10 constellation in the sky, depicting not only what is currently in the sky but it also allows the 20 prediction of the rising and setting times of various celestial objects. 30 THE LAYOUT OF THE PLANISPHERE 40 50 The outer circumference of the dark blue circular disk (which is called the star wheel) you’ll notice that the wheel is divided into the 12 months, and that each month is divided into 60 individual dates. The star wheel rotates about the brass fastener, which represents the 70 North Celestial Pole. The frame of the planisphere has times along the outer edge. 80 Holding the planisphere on the southern corner you'll see "midnight" at the top. Moving Zenith counterclockwise, notice how the hours progress, through 1 AM, 2 AM, and so on through "noon" at the bottom. The hours then proceed through the afternoon and evening (1 PM, 2 PM, etc.) back toward midnight. Once you have the wheel set properly for the correct time and day, the displayed part represents what you see if you stand with the star and planet locator held directly over your head with the brass fastener toward the north. (Notice that the compass directions are also written on the corners of the frame.) Of course, you don't have to actually stand that way to make use of the Star and Planet Locator--this is just a description to help you understand what is displayed. -
Earth-Centred Universe
Earth-centred Universe The fixed stars appear on the celestial sphere Earth rotates in one sidereal day The solar day is longer by about 4 minutes → scattered sunlight obscures the stars by day The constellations are historical → learn to recognise: Ursa Major, Ursa Minor, Cassiopeia, Pegasus, Auriga, Gemini, Orion, Taurus Sun’s Motion in the Sky The Sun moves West to East against the background of Stars Stars Stars stars Us Us Us Sun Sun Sun z z z Start 1 sidereal day later 1 solar day later Compared to the stars, the Sun takes on average 3 min 56.5 sec extra to go round once The Sun does not travel quite at a constant speed, making the actual length of a solar day vary throughout the year Pleiades Stars near the Sun Sun Above the atmosphere: stars seen near the Sun by the SOHO probe Shield Sun in Taurus Image: Hyades http://sohowww.nascom.nasa.g ov//data/realtime/javagif/gifs/20 070525_0042_c3.gif Constellations Figures courtesy: K & K From The Beauty of the Heavens by C. F. Blunt (1842) The Celestial Sphere The celestial sphere rotates anti-clockwise looking north → Its fixed points are the north celestial pole and the south celestial pole All the stars on the celestial equator are above the Earth’s equator How high in the sky is the pole star? It is as high as your latitude on the Earth Motion of the Sky (animated ) Courtesy: K & K Pole Star above the Horizon To north celestial pole Zenith The latitude of Northern horizon Aberdeen is the angle at 57º the centre of the Earth A Earth shown in the diagram as 57° 57º Equator Centre The pole star is the same angle above the northern horizon as your latitude. -
Exercise E1: Finding Your Way Around the Sky
E – Star Finding Exercise E1: Finding Your Way Around the Sky Student name: ________________________ Class: ____________ Date: _____________ Check the box with the correct answer. Question 1: What is the orientation of the Big Dipper asterism in winter? a. It appears upside down. b. It sits with its handle downwards. c. It appears to sit upright, resting upon its bowl. d. The Big Dipper is not visible in the winter. Question 2: Polaris is part of which constellation? (Hint: Select Constellations from the Settings view to display IAU Boundaries and Show Names). a. Cepheus b. Draco c. Ursa Minor d. Ursa Major Question 3: What happens to the position of Polaris in your sky as time advances over a period of a year? a. It remains absolutely fixed, and does not change its position. b. The north celestial pole revolves about Polaris. c. It revolves in a very small circle around the north celestial pole. d. Its altitude changes by + and - 23.5 degrees throughout the year because of the tilt of the Earth's spin axis. Starry Night College Version 7 1 Question 4: What is the relationship between the altitude of Polaris and the latitude of the observer? a. There is no relationship between these two parameters. b. The altitude of Polaris is almost the same as the latitude of the observer. c. The altitude of Polaris is almost the equal to 90 degrees minus the latitude of the observer. d. The latitude equals the altitude of Polaris minus the altitude of the North celestial Pole. Question 5: What is the nearest star to the south celestial pole, as shown in the Main Window? (Hint: Use the Search facility to locate these stars and zoom in towards the SCP. -
Calibration of the Angular Momenta of the Minor Planets in the Solar System Jian Li1, Zhihong Jeff Xia2, Liyong Zhou1
Astronomy & Astrophysics manuscript no. arXiv c ESO 2019 September 26, 2019 Calibration of the angular momenta of the minor planets in the solar system Jian Li1, Zhihong Jeff Xia2, Liyong Zhou1 1School of Astronomy and Space Science & Key Laboratory of Modern Astronomy and Astrophysics in Ministry of Education, Nanjing University, 163 Xianlin Road, Nanjing 210023, PR China e-mail: [email protected] 2Department of Mathematics, Northwestern University, 2033 Sheridan Road, Evanston, IL 60208, USA e-mail: [email protected] September 26, 2019 ABSTRACT Aims. We aim to determine the relative angle between the total angular momentum of the minor planets and that of the Sun-planets system, and to improve the orientation of the invariable plane of the solar system. Methods. By utilizing physical parameters available in public domain archives, we assigned reasonable masses to 718041 minor plan- ets throughout the solar system, including near-Earth objects, main belt asteroids, Jupiter trojans, trans-Neptunian objects, scattered- disk objects, and centaurs. Then we combined the orbital data to calibrate the angular momenta of these small bodies, and evaluated the specific contribution of the massive dwarf planets. The effects of uncertainties on the mass determination and the observational incompleteness were also estimated. Results. We determine the total angular momentum of the known minor planets to be 1:7817 × 1046 g · cm2 · s−1. The relative angle α between this vector and the total angular momentum of the Sun-planets system is calculated to be about 14:74◦. By excluding the dwarf planets Eris, Pluto, and Haumea, which have peculiar angular momentum directions, the angle α drops sharply to 1:76◦; a similar result applies to each individual minor planet group (e.g., trans-Neptunian objects). -
Astronomy and Astrology
Astronomy and Astrology Philippe Zarka CNRS & Observatoire de Paris, France Daniel Kunth CNRS- I.A.P, France 1. Introduction : what is astrology ? 2. Astrology & Society 3. Astrology & Astronomy 4. Astrology & Science 5. Conclusion : the success of Astrology and the role of Science • References 1. Introduction : what is astrology ? 2. Astrology & Society 3. Astrology & Astronomy 4. Astrology & Science 5. Conclusion : the success of Astrology and the role of Science • References The influence of celestial bodies on Earth has several obvious manifestations : life on Earth depends on the Sun, seasons are linked to its position in the sky (due to the non–perpendicularity of the Earth’s rotation axis with respect to the ecliptic plane), … Seasons … ocean tides are controlled by the position of the Moon (via its differential gravitation) and of the Sun, and eclipses are due to Sun–Moon–Earth alignments. Solar eclipse High/Low tides Astrology extrapolates these factual influences by postulating that the positions of the Sun, Moon and 8 planets* other than Earth (hereafter the « luminars ») with respect to the sky background, as well as with respect to each other, influence terrestrial events and human psychology and destiny. *wandering celestial bodies Apparent trajectory of Mars as seen from Earth, and explanation The position of luminars is considered - relative to the tropical zodiac, defined by Hipparchus* : 12 « signs » dividing in 30° sectors the band of constellations upon which the motions of the Sun and planets are projected during the year, with an arbitrary origin at the vernal – spring – equinox (γ), and - relative to the « houses », a local reference frame dividing the local sky in 12 sectors. -
The Coriolis Effect in Meteorology
THE CORIOLIS EFFECT IN METEOROLOGY On this page I discuss the rotation-of-Earth-effect that is taken into account in Meteorology, where it is referred to as 'the Coriolis effect'. (For the rotation of Earth effect that applies in ballistics, see the following two Java simulations: Great circles and Ballistics). The rotating Earth A key consequence of the Earth's rotation is the deviation from perfectly spherical form: there is an equatorial bulge. The bulge is small; on Earth pictures taken from outer space you can't see it. It may seem unimportant but it's not: what matters for meteorology is an effect that arises from the Earth's rotation and Earth's oblateness together. A model: parabolic dish Thinking about motion over the Earth's surface is rather complicated, so I turn now to a model that is simpler but still presents the feature that gives rise to the Coriolis effect. Source: PAOC, MIT Courtesy of John Marshall The dish in the picture is used by students of Geophysical Fluid Dynamics for lab exercises. This dish was manufactured as follows: a flat platform with a rim was rotating at a very constant angular velocity (10 revolutions per minute), and a synthetic resin was poured onto the platform. The resin flowed out, covering the entire area. It had enough time to reach an equilibrium state before it started to set. The surface was sanded to a very smooth finish. Also, note the construction that is hanging over the dish. The vertical rod is not attached to the table but to the dish; when the dish rotates the rod rotates with it. -
The Spin, the Nutation and the Precession of the Earth's Axis Revisited
The spin, the nutation and the precession of the Earth’s axis revisited The spin, the nutation and the precession of the Earth’s axis revisited: A (numerical) mechanics perspective W. H. M¨uller [email protected] Abstract Mechanical models describing the motion of the Earth’s axis, i.e., its spin, nutation and its precession, have been presented for more than 400 years. Newton himself treated the problem of the precession of the Earth, a.k.a. the precession of the equinoxes, in Liber III, Propositio XXXIX of his Principia [1]. He decomposes the duration of the full precession into a part due to the Sun and another part due to the Moon, to predict a total duration of 26,918 years. This agrees fairly well with the experimentally observed value. However, Newton does not really provide a concise rational derivation of his result. This task was left to Chandrasekhar in Chapter 26 of his annotations to Newton’s book [2] starting from Euler’s equations for the gyroscope and calculating the torques due to the Sun and to the Moon on a tilted spheroidal Earth. These differential equations can be solved approximately in an analytic fashion, yielding Newton’s result. However, they can also be treated numerically by using a Runge-Kutta approach allowing for a study of their general non-linear behavior. This paper will show how and explore the intricacies of the numerical solution. When solving the Euler equations for the aforementioned case numerically it shows that besides the precessional movement of the Earth’s axis there is also a nu- tation present. -
From Our Perspective... the Ecliptic
2/9/09 Why don’t we see the same Mastering Astronomy Assignment 3 constellations throughout the year? • Due Feb 17, 11 am • Read Sections 2.1, 2.2 and S1.2 The Earth also revolves around the Sun, From our perspective... which changes our view of the stars March September Earth circles the Sun in 365.25 days and, The Ecliptic consequently, the Sun appears to go once around the ecliptic in the same period. If we could see • As the Earth orbits background stars in the daytime, our Sun would the Sun, the Sun appears to move a) appear to move against them at a rate of 360° per eastward among the day. stars following a path b) appear to move against them at a rate of about called the ecliptic 15° per day. • The ecliptic is a c) appear to move against them at a rate of about 1° projection of Earth’s per day. orbit onto the The tilt of the Earth's axis d) remain stationary against these stars. celestial sphere causes the ecliptic to be tilted to the celestial equator 1 2/9/09 The sky varies as Earth orbits the Sun • As the Earth orbits the Sun, the Sun appears to move along the Zodiac ecliptic. • At midnight, the stars on our meridian are opposite the Sun in The 13 Zodiacal constellations that our Sun the sky. covers-up (blocks) in the course of one year (used to be only 12) • Aquarius • Leo • Pisces • Libra • Aries • Virgo • Scorpius • Taurus • Ophiuchus • Gemini • Sagittarius • Cancer • Capricornus The Zodiacal Constellations that our Sun blocks in the course of one year (only 12 are shown here) North Star Aquarius Pisces Capricornus Aries 1 day Sagittarius Taurus Scorpius 365 days Libra Gemini Virgo Cancer Leo North Star Aquarius Pisces Capricornus In-class Activities: Seasonal Stars Aries 1 day Sagittarius • Work with a partner! Taurus Scorpius • Read the instructions and questions carefully. -
How Long Is a Year.Pdf
How Long Is A Year? Dr. Bryan Mendez Space Sciences Laboratory UC Berkeley Keeping Time The basic unit of time is a Day. Different starting points: • Sunrise, • Noon, • Sunset, • Midnight tied to the Sun’s motion. Universal Time uses midnight as the starting point of a day. Length: sunrise to sunrise, sunset to sunset? Day Noon to noon – The seasonal motion of the Sun changes its rise and set times, so sunrise to sunrise would be a variable measure. Noon to noon is far more constant. Noon: time of the Sun’s transit of the meridian Stellarium View and measure a day Day Aday is caused by Earth’s motion: spinning on an axis and orbiting around the Sun. Earth’s spin is very regular (daily variations on the order of a few milliseconds, due to internal rearrangement of Earth’s mass and external gravitational forces primarily from the Moon and Sun). Synodic Day Noon to noon = synodic or solar day (point 1 to 3). This is not the time for one complete spin of Earth (1 to 2). Because Earth also orbits at the same time as it is spinning, it takes a little extra time for the Sun to come back to noon after one complete spin. Because the orbit is elliptical, when Earth is closest to the Sun it is moving faster, and it takes longer to bring the Sun back around to noon. When Earth is farther it moves slower and it takes less time to rotate the Sun back to noon. Mean Solar Day is an average of the amount time it takes to go from noon to noon throughout an orbit = 24 Hours Real solar day varies by up to 30 seconds depending on the time of year. -
Ibrāhīm Ibn Sinān Ibn Thābit Ibn Qurra
From: Thomas Hockey et al. (eds.). The Biographical Encyclopedia of Astronomers, Springer Reference. New York: Springer, 2007, p. 574 Courtesy of http://dx.doi.org/10.1007/978-0-387-30400-7_697 Ibrāhīm ibn Sinān ibn Thābit ibn Qurra Glen Van Brummelen Born Baghdad, (Iraq), 908/909 Died Baghdad, (Iraq), 946 Ibrāhīm ibn Sinān was a creative scientist who, despite his short life, made numerous important contributions to both mathematics and astronomy. He was born to an illustrious scientific family. As his name suggests his grandfather was the renowned Thābit ibn Qurra; his father Sinān ibn Thābit was also an important mathematician and physician. Ibn Sinān was productive from an early age; according to his autobiography, he began his research at 15 and had written his first work (on shadow instruments) by 16 or 17. We have his own word that he intended to return to Baghdad to make observations to test his astronomical theories. He did return, but it is unknown whether he made his observations. Ibn Sinān died suffering from a swollen liver. Ibn Sinān's mathematical works contain a number of powerful and novel investigations. These include a treatise on how to draw conic sections, useful for the construction of sundials; an elegant and original proof of the theorem that the area of a parabolic segment is 4/3 the inscribed triangle (Archimedes' work on the parabola was not available to the Arabs); a work on tangent circles; and one of the most important Islamic studies on the meaning and use of the ancient Greek technique of analysis and synthesis. -
Thomas Precession Is the Basis for the Structure of Matter and Space Preston Guynn
Thomas Precession is the Basis for the Structure of Matter and Space Preston Guynn To cite this version: Preston Guynn. Thomas Precession is the Basis for the Structure of Matter and Space. 2018. hal- 02628032 HAL Id: hal-02628032 https://hal.archives-ouvertes.fr/hal-02628032 Submitted on 26 May 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Thomas Precession is the Basis for the Structure of Matter and Space Einstein's theory of special relativity was incomplete as originally formulated since it did not include the rotational effect described twenty years later by Thomas, now referred to as Thomas precession. Though Thomas precession has been accepted for decades, its relationship to particle structure is a recent discovery, first described in an article titled "Electromagnetic effects and structure of particles due to special relativity". Thomas precession acts as a velocity dependent counter-rotation, so that at a rotation velocity of 3 / 2 c , precession is equal to rotation, resulting in an inertial frame of reference. During the last year and a half significant progress was made in determining further details of the role of Thomas precession in particle structure, fundamental constants, and the galactic rotation velocity.