* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Debris Belts around Vega - Astronomical Society of the Pacific
Star of Bethlehem wikipedia , lookup
Astrophotography wikipedia , lookup
Cygnus (constellation) wikipedia , lookup
Circumstellar habitable zone wikipedia , lookup
Outer space wikipedia , lookup
James Webb Space Telescope wikipedia , lookup
Kepler (spacecraft) wikipedia , lookup
Rare Earth hypothesis wikipedia , lookup
History of astronomy wikipedia , lookup
Corvus (constellation) wikipedia , lookup
International Ultraviolet Explorer wikipedia , lookup
Space Interferometry Mission wikipedia , lookup
Aquarius (constellation) wikipedia , lookup
Astrobiology wikipedia , lookup
Dwarf planet wikipedia , lookup
Beta Pictoris wikipedia , lookup
Observational astronomy wikipedia , lookup
IAU definition of planet wikipedia , lookup
Exoplanetology wikipedia , lookup
Definition of planet wikipedia , lookup
Nebular hypothesis wikipedia , lookup
Directed panspermia wikipedia , lookup
Extraterrestrial life wikipedia , lookup
Planetary habitability wikipedia , lookup
Solar System wikipedia , lookup
History of Solar System formation and evolution hypotheses wikipedia , lookup
Formation and evolution of the Solar System wikipedia , lookup
Debris Belts around Vega Topic: Exoplanets Concepts: Infrared observations, debris disks, exoplanet detection, planetary systems Missions: Spitzer, Herschel Coordinated by the NASA Astrophysics Forum An Instructor’s Guide for using the slide sets is available at the ASP website: https://www.astrosociety.org/ education/resources-for-the-higher-education-audience/ Vega is wearing two belts! • Infrared observations reveal the star Vega has a “warm” inner dust belt in addition to the previously observed outer “cold” dust belt. • The discovery can be explained by two belts of leftover planetesimals whose ongoing collisions produce the detected dust — analogous to the Sun’s asteroid and Kuiper Belts. Could this also suggest a similar planetary system for Vega? Above: Image of the debris disk around the star Vega taken in infrared light with the Herschel Space Observatory. (Credit: Su et al., 2013) Right: Artist’s illustration of debris belt around Vega. (Credit: NASA/JPL-Caltech) How was the discovery made? • The Spitzer Space Telescope and the Herschel Space Observatory detected infrared light in excess of that expected from the star alone. • By comparing Vega with similar stars, scientists subtracted the infrared emission produced by the star itself, leaving the emission radiated by surrounding dust particles warmed by the star. Herschel Space Observatory infrared image of the debris disk around the star Vega, after subtracting the light of the star Vega itself. (Credit: Su et al., 2013) • The inner region of infrared excess could not be resolved into a belt like the outer one, but the temperature of the dust is consistent with an asteroid belt about the same proportional distance from Vega as ours is from our smaller Sun. The Big Picture • Scientists have found other stars with similar inner and outer debris belts, with the outer belt about ten times farther from the stars than the inner belt. • One such star, HR8799, has been found to have four giant planets orbiting in the gap between belts. • Our own solar system also has four giant planets orbiting between the rocky asteroid belt and the icy Kuiper belt. • No planets have yet been detected around Vega, but if the star were eventually found to have several giant planets in orbit, this may suggest a common model for how stars form planets and how their planetary systems evolve. How does this discovery change our view? • Other stars can host planetary systems similar to the Sun. The outer belts of both Vega and Sun are about ten times more distant from the star than the inner belts. Our solar system has planets between debris belts, and Vega may have planets in the “gap” also. Credit: NASA/JPL-Caltech In this diagram, the Vega system (left) is compared with our Solar system scaled up by a factor of four (right). The inner asteroid belt (orange) and Kuiper belt (red) are similar in relative scale, with the distance from the stars to the outer debris belts about ten times greater than the inner belts. The true relative size of our solar system is illustrated by the small drawing in the middle. • Multiple debris belts may be a clue to the presence of several planets. • Our solar system may not be unique. Resources Press Release about this result: http://www.nasa.gov/home/hqnews/2013/jan/HQ_13-006_Vega_Asteroid_Belt.html Scientific paper: Su, et al., 2013, ApJ 763:118 http://iopscience.iop.org/0004-637X/763/2/118/ Synopsis article: http://astrobites.org/2013/01/20/asteroid-belt-found-in-the-vega-system/ Additional resources: Exoplanet resource guide http://www.astrosociety.org/education/astronomy-resource-guides/ the-search-for-planets-around-other-stars/ AAS announcement by Kate Su https://www.youtube.com/watch?v=neJkNoFl2uM Extrasolar Planets Encyclopaedia http://exoplanet.eu/ Debris Belts around Vega BONUS CONTENT Why haven’t we found planets for Vega? • Vega is oriented on the plane of the sky, so we’re looking at one of its poles, and its debris disk is seen faceon, not edge-on. • We can’t detect planets by the “transit” method, since they wouldn’t pass in front of the star from our perspective. • We can’t detect planets by the “Doppler” method because stars like Vega rotate very fast and have very few narrow lines in their spectra Credit: NASA/JPL-Caltech for detection of the tiny shifts in line position caused by the gravitational tugs of planets. • Direct visual searches have turned up empty, suggesting orbiting planets are too small for us to detect yet by this method. • The more powerful James Webb Space Telescope or more sensitive groundbased searches may eventually find Jupiter-sized or smaller planets orbiting in Vega’s gap. Collected Instructor’s Notes, part 1 “Vega is wearing 2 belts!” (page 2 in this PDF) Debris Disk: a disk of small particles encircling a star or planet. “Belts,” “disks,” and “rings” are all debris disks. The Figure is the Herschel view of the whole system, where the star is very bright at the center The two solid circles mark radii of 5′′ and 7′′, while the dashed circle marks a radius of 14′′ (representing the cold planetesimal ring). “How was the Discovery Made?” (page 3 in this PDF) Herschel = (an ESA* mission with NASA participation) *ESA = European Space Agency Figure is the glowing dust image after the contribution of the star has been taken out. Arrows point to the location of the belts. Colors represent intensity of light, from bright (red) to faint (blue).The inner belt is not resolved into a ring, but rather is detected as excess light at the star’s position. Vega is viewed almost face-on. “The Big Picture” (page 4 in this PDF) Astronomers study stars with varying characteristics to understand how planetary systems evolve. Vega’s system is similar to our solar system, but Vega is different from the Sun. Both stars have cold, outer belts like our Kuiper Belt (~50 K) Vega is young(~400-600 million years old), while the Sun is 4.6 billion years old. Vega is bright (spectral type A), 16-40 times more luminous than the Sun The clear separation of the belts could be explained by the presence of planets clearing the gap. Indeed, HR 8799 is already known to have 4 planets in this region. “How does this discovery change our view” (page 5 in this PDF) Vega and the Sun all have a warm inner belt at ice/gas transition temperature (~170K) and a cold outer belt at ~50K. The outer belt of Vega is about 10X more distant from the star than the inner belt. The distance between our Sun’s (outer, colder) Kuiper and (warmer, inner) Asteroid belts is also a 10:1 ratio Model calculations predict that several planets (smaller than Jupiter) maintain a dust-free zone by sweeping up material in that gap. Thus it is likely that several yet-undetected planets reside in the gap between Vega’s belts. Could double belts be a hallmark of a multi-planet system? – focus future observations on similar systems! 8 Collected Instructor’s Notes, part 2 “Resources” (page 6 in this PDF) Contributing Missions: Herschel Space Observatory: http://www.nasa.gov/mission_pages/herschel/index.htmll Spitzer Space Telescope: http://www.nasa.gov/mission_pages/spitzer/main/index.html “Why haven’t we found planets for Vega?” (page 8 in this PDF) Each technique is sensitive to detecting planets with certain physical characteristics (size, distance from star, inclination, etc). Astronomers use all the evidence available to target their searches. For example, if there’s indirect evidence such as in this case, astronomers could target direct observations. Subtleties in why we can’t detect planets by the “Doppler” method: “early-type” stars like Vega rotate very fast and have very few narrow spectral lines. This means it is very difficult to notice any star wobble. The dominating reason is simply line of sight. 9