... PG 1115+080: A Gravitational Cloverleaf . ... Credit: CISCO , Subaru 8.3-m Telescope , NAOJ Explanation: All four blue images in the above photograph are the same object. The gravitational lens effect of the red, foreground, elliptical galaxy visible near image center creates a cloverleaf image of the single distant quasar . Light from the quasar is pulled around the massive galaxy in different paths, corresponding to different images. ... Publications with words: gravitational lens - quasar . ...

... 2001 June 14 . Around The Arches Cluster . Credit: X-ray; NASA / CXC / Northwestern / F. Zadeh et al., IR; NASA/ HST /NICMOS, . ... Explanation: The most compact cluster of stars known in our galaxy, the Arches cluster , boasts 100 or so massive, young stars contained within a diameter of one light-year. ... Astronomers consider the tightly packed and relatively nearby Arches cluster, an analog of the furious star forming regions in galaxies millions of light-years away. ... About APOD | ...

... 2000, ApJ, 537, L49 . ... F. Palla . Invited Talk at the IAU Symposium 200 "The formation of binary stars" eds. R.D. Mathieu and H. Zinnecker (ASP Conf. Ser.) in press . Optical follow-up of ROSAT discovered candidate members of the open cluster Coma Berenices . ... 2000, A , in press . ... 2000, ApJ, in press . ... 2000, ApJ, in press (Sept. ... 2000, ApJ Lett., in press . ... Click to examine publications from other years . ... Star Formation Group . ... Arcetri Home Page . ...

... Compact Binaries . ... Unlike the Sun, most stars in our Galaxy orbit another star: these systems are called binary stars. Generally it takes many years for the two stars to orbit around each other. ... These binaries are interesting for many reasons. One is that they are predicted to emit lots of gravitational waves. ... Over time as gravitational waves are emitted, the time taken for the two stars to orbit one another changes by a small but measurable amount. ...

... In one situation, we can use light from quasars to probe the material between us and them because that light may pass through one or more galaxies or gas clouds on its way to us. The gas inside the galaxies or the intergalactic clouds acts then as a filter, absorbing selected wavelengths from the quasar light. ... Light from a quasar must pass through clouds of gas and even faint galaxies -- each leaving its imprint on the light -- before we receive it here on Earth. ... Gravitational lensing . ...

Program number . ... Infrared Snapshots of 3CR Radio Galaxies . Abstract . ... Holland Ford, The Johns Hopkins University . ... An ACS H-alpha Survey of the Carina Nebula . ... A Snapshot Survey of the most massive clusters of galaxies . ... An ACS Imaging Survey of the Galaxies Hosting Strong Mg II Absorption . ... ACS observations of the galaxies in a giant Ly-alpha nebula at z~2.7 . ... An ACS Survey of a Complete Sample of Luminous Infrared Galaxies in the Local Universe . ... Past weeks: . ...

... ESO is building what will be the World's largest optical telescope array, The Very Large Telescope (VLT). The VLT Project organisation is responsible for the design and construction of the Unit Telescopes, including enclosures, optics, adapter-rotators and coating unit. ... Unit Telescopes Overview - This page is outdated, an update is in process. ... Secondary mirror (M2 Unit) - This page is outdated, an update is in process. ... Coating Unit - This page is outdated, an update is in process. ...

... X-rays are made up of photons that are emitted from stars, or quasars, or supernovae, the sun, or simply: anything that is undergoing a change either in size or temperature or giving out heat. ... in an X-ray binary star system, in which one normal star's orbit is crossed by a neutron star, when the neutron star by means of gravitational pull takes matter from the normal star X-rays form. ... Artists conception of a normal star (HDE 226868) and a black hole taking matter from the normal star. ...

... Image Quality of the VLT . Total Optical Control . First light for the ESO VLT unit telescope 1 occurred during the workshop. ... The image shown (Figure 1 ) here was obtained with the VLT on May 16, 1998, in red light (R band), i.e. while the mirror was still uncoated. ... In this diagram (FIgure 2), the measured image quality of the VLT UT1 astronomical images is plotted versus the ``seeing", as measured by the Seeing Monitor, a small telescope also located on top of the Paranal Mountain. ...

Stellar Clusters are very useful laboratories for empirically studying stellar evolution. ... All cluster stars are at the same distance . All cluster stars have the same physical age . ... CM diagram Young Cluster In this case we see the Main Sequence fully represented. The blue dots represent massive stars with short main sequence lifetimes. ... Thus, identifying the most massive star which is still on the main sequence is an effective means of determining the age of a stellar cluster. ...

... 50 Weirdest Objects . ... Get to Know the Night Sky . ... Picture of the Day . ... Observing springtime deep-sky objects with a large telescope . ... How can the Hubble Space Telescope (HST) take pictures of objects light-years away but not get a good picture of Pluto? ... At its distance, it subtends a smaller angle on the sky than does a galaxy at a distance of billions of light-years. Get instant access to subscriber content on Astronomy.com! ... Get full access to StarDome PLUS . ...

... Bad Astronomy . Misconceptions . ... Bad Astronomy : "We're light years more advanced than our competition!" ... Even the closest astronomical object, the Moon, is 400,000 kilometers away! ... A beam of light will travel 9,500,000,000,000 kilometers in one year. This distance is defined as a light year ; the distance light travels in a year. ... This is another example of Bad Astronomy; like a light year, a parsec is a unit of distance, not time (to be specific, it equals 3.26 light years) . ...

... Feeding the Monster: Gas Caught in its Death Spiral into a Massive Black Hole . ... Stromlo Professor Mike Dopita have used the Hubble Space Telescope to discover how a massive Black Hole in a nearby galaxy feeds itself. ... Earlier Hubble Telescope data obtained by another team member, Professor Holland Ford of Johns Hopkins University in Baltimore, Maryland, had found a disk of gas rushing around the Black Hole at a speed of 500 kilometers a second. ...

... For the past years I have been working on the problem of synthesis of light curves of close binary systems, consisting of a normal star and a compact object (point object with fixed X-ray luminosity). ... Possible existence of a bright spot on the disk's lateral surface is taken into account. ... The last of then will be published in Gordon and Breach Publishers ( Cherepashchuk A.M., Katysheva N.A., Khruzina T.S., Shugarov S.Yu. ... Cherepashchuk A.M., Katysheva N.A., Khruzina T.S., Shugarov S.Yu. ...

Collins School Star Party - Oct. 5, 1999 Presented by the North Shore Amateur Astronomy Club (NSAAC) For more information: NSAAC: http://www.star.net/people/~nsaac 1.0 Using a telescope Close one eye (use your hand if it's easier) and look straight down into the eyepiece. ... Massive stars use up their fuel much faster - in some cases less than 100 million years. ... Jupiter _____. ... With the chart at left and using the brightest stars as a guide, see if you can find Uranus with binoculars. ...

Astronotes Armagh Planetarium's Stellar Blog! ... Our Galaxy . ... Stars . ... Other Galaxies . ... Light of other eyes, other times: The X-rays and IR radiation making up the image have been travelling for a long time. ... The inspiration here came from a new ESA image of M31, the Andromeda Galaxy, composed from two very different images. ... Our nearest galactic neighbour, the Andromeda Galaxy?s brightness is caused by the hundreds of billions of stars that are contained within. ...

... The Pleiades star cluster, also known as the Seven Sisters and Messier 45, is a conspicuous object in the night sky with a prominent place in ancient mythology . ... The stars in the Pleiades are thought to have formed together around 100 million years ago, making them 1/50th the age of our sun, and they lie some 130 parsecs (425 light years ) away. ... Data for these stars are listed in a table below. ... Yes . ... WEBDA Pleiades cluster data . ... M45: The Pleiades Star Cluster (2007 November 18) ...

... Astrophysics Group . ... AMI Science . ... Observations of galaxy clusters are central to the AMI science programme. The AMI Small Array is used to observe already-known clusters with high-sensitivity and resolution, allowing us to extract detailed information about individual clusters and to build up statistics about the cluster population. ... Observing galaxy clusters at 15 GHz is tricky because of the contamination from foreground radio sources, which is where the Large Array comes in! ...

... Time delay determinations in astrophysics are used most often to find time delays between flux density variations in different spectral bands and/or lines in AGNs, and different images of gravitationally lensed QSOs. ... OB used an idea to take into account the known gravitational lensing time delay to get combined radio and optical light curves and then to use them for determination of the possible radio-from-optical time delay. ... Correction for change of time delay and radio flux. ...

... Archive of publications: . ... 2012 . 2011 . 2009 . 2008 . 2007 . 2006 . 2005 . 2004 . 2003 . ... From 2015 2014 2013 2012 2011 2009 2008 2007 2006 2005 2004 2003 to 2015 2014 2013 2012 2011 2009 2008 2007 2006 2005 2004 2003 . ... Whight light corona at different phases of the solar cycle Sun and Geosphere, V. 6, 1, 2011 . ...