ING Scientific Highlights in 1988
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ING Scientific Highlights
in 1989*

*Astronomical discoveries following from observations carried out with the ING telescopes


[ 1988 Scientific Highlights | 1990 Scientific Highlights ]



Reconstructed images of a surface feature on BetelgeuseA high resolution imaging experiment resulted in the first ever reliable images of the surface of a star other than the Sun. Betelgeuse, the nearest huge supergiant star, is only 150 parsec distant and has a diameter of about 600 million kilometres. Its angular diameter as seen from Earth is about 50 milliarcseconds.

The researchers used techniques derived from radio astronomy to make an optical map that just resolved the brightness distribution across the surface of Betelgeuse. A hotspot, contributing about 10 percent of the stellar flux, was discovered on the surface. This is probably caused by a giant convection cell in the atmosphere of the star.

More information

ING facilities involved: 

  • William Herschel Telescope, using GHRIL.
Some references: 
  • Buscher, D.F. et al, 1990, "Detection of a bright feature on the surface of Betelgeuse", MNRAS, 245, 7 
  • Wilson, R. W. et al.,1992, "High resolution Imaging of Betelgeuse and Mira", MNRAS, 257,369 
  • Wilson, A. et al, 1991, "The changing surface of Betelgeuse", GEMINI Newsletter Royal Greenwich Obs., 34, 20


CCD image of PSR1957+20 The recently discovered 1.6 ms binary radio pulsar PSR1957+20 shows radio eclipses whose duration indicates that the occulting body is substantially larger than the Roche lobe of the low-mass companion star. This suggests that this companion is evaporating through the action of a strong pulsar energy flux. An optical counterpart has been detected which shows brightness variations in phase with the 9.2 h orbital cycle. Astronomers have obtained optical charge coupled devive (CCD) images which show that the counterpart is one component of a close visual pair separated by 0.7 arcsec approximately. At maximum both are equally bright with combined V magnitude of 19.9, while at minimum PSR1957+20 is invisible. From spectroscopic observations we find that the contaminating star is a normal G star. The spectrum of PSR1957+20 shows intermittent H-alpha emission. The optical brightness of PSR1957+20 varies in phase with the radio Doppler velocity curve, and find that the amplitude is probably more than 3 magnitudes, minimum light coinciding with the radio eclipse. The optical light curve is consistent with heating of a hydrogen-rich low-mass white dwarf by high-energy radiation from the nearby millisecond pulsar.

The radio observations indicate an extended region of the plasma surrounding the companion, and it has been suggested that this may be due to the evaporation of the companion by the intensity of the radiation from the neutron star. The high quality light curve, obtained in sub-arcsecond seeing conditions, is being used to investigate various properties of the system, for example the temperature difference across the dwarf and the physics of the heating and evaporation mechanisms. 

More information

ING facilities involved: 

  • William Herschel Telescope using a CCD camera at a Nasmyth focus and the Faint Object Spectrograph (FOS) at the Cassegrain focus
Pictures: Some references: 
  • Callanan, P.J. et al, 1989, "The optical light curve of PSR1957+20", MNRAS, 240, 31 
  • Charles, P., 1988, "CCD Pulsar Imaging", Gemini Newsletter, 21, 1.
  • van Paradijs, J., Allington-Smith, J., Callanan, P., Charles, P.A., Hassall, B.J.M., Machin, G., Mason, K.O., Naylor, T. & Smale A.P., 1988, "Optical observations of the eclipsing binary radio pulsar PSR1957+20", Nature, 334, 684.



Velocity and Velocity
Dispersion measurements of the bulge of M31Observations with the WHT and the ISIS spectrograph have greatly improved our knowledge of the rotation properties of a number of nearby galaxies. Two of the galaxies observed, the Andromeda nebula M31, and its compact elliptical companion M32, have been proposed as black hole candidates on the basis of their rapid central rotation. In excellent seeing conditions rotation velocities in the centres were measured with unprecedented spatial resolution. Despite the excellent seeing the central velocity in M31 is still unresolved, strengthening the case for a central black hole of at least 107 and probably 108 solar masses in this galaxy. In M32 the rotation gradient is much less steep, but the case for a central black hole of around 8x106 solar masses is still strong.

Based on the success of these observations, researchers have searched for similarly rotating cores in other galaxies. Two very strong candidates have emerged, NGC3115, a lenticular, and NGC5813, an elliptical. In the later case the rotation gradient is also unresolved, and this is a particularly strong candidate for a black hole. NGC205 is a different kind of galaxy, a dwarf spheroidal companion on M31. It is elongated with an axial ratio of two to one. Observations with the intermediate dispersion spectrograph on the INT have shown that this galaxy does not rotate at all. It must be flattened by an anisotropic velocity dispersion, which is suprising for such a small galaxy.

More information

ING facilities involved:

  • William Herschel Telescope, using ISIS
  • Isaac Newton Telescope, using IDS
Some references: 
  • Carter D. et al., 1993, "High-resolution kinematic observations of rapidly rotating spheroidal components of galaxies", MNRAS, 263, 1049.
  • Carter, D. et al, 1990, "Kinematics of the Dwarf Spheroidal Galaxy NGC205", MNRAS,245, 12


V-band linear polarisation and contour map of 3C368High redshift radio galaxies are characterised by strong UV excesses associated with elongated continuum and emmission line regions aligned along their radio axies. Previous attempts to explain these properties have been in terms of a model in which the radio emitting plasma ionizes and promotes star formation in the interstellar medium through which it passes.

However, observations of a continuum emitting knot in a low redshift radio galaxy led to the proposal of an alternative beaming/scattering model, in which the EUV photons ionize the gas in the clouds, rather like a giant bipolar reflection nebula. A polarisation map of the high redshift radio galaxy 3C268, made on the WHT, using an imaging polarimeter, reveals just such a structure, and is convincing evidence for the beaming/scattering model.

More information

ING facilities involved:

  • William Herschel Telescope, using the Durham Imaging Polarimeter
Some references: 
  • Scarrott. et al., 1990, "Imaging polarimetry of the high-z radio galaxy 3C368", MNRAS, 243, L5



Quasar 2337+0305 lensedOne of the most dramatic manifestations of gravitational lensing is exhibited by the quasar 2237+0305, which has a redshift of z=1.70. The quasar is located exactly behind the centre of a bright spiral galaxy with a redshift of only z=0.04, and the quasar image is split into four separate components separated from each other by less than 2 arcseconds. The light paths through the galaxy to each of the images may pass close to other stars or other compact objects in the galaxy, producing gravitational lensing effects manifested as brightness changes in the images. Such effects are termed "microlensing" events.

Working with images from the WHT, the researchers made the first detection of a gravitational microlensing event in 2337+0305. The group found that the brightest of the four images had increased in brightness by 0.5 magnitudes (in the red band of the spectrum) over a period of less than a year and possibly on a timescale of only a month. The team is following up the detection with a monitoring campaign on the JKT, from which it is hoped to determine an upper limit on the size of the quasar continuum source region.

More information

ING facilities involved:

  • William Herschel Telescope, with a Cassegrain imaging CCD
  • Jacobus Kapteyn Telescope 
Some references: 
  • Irwin, M.J. et al., 1989, "Photometric variations in the Q2237+0305 - First detection of a microlensing event", AJ, 98, 1989
  • Corrigan, R., Jedrzejewski, R., Webster, R., Harding, M., Hewett, P., 1988, "Gravitational Lensing", Gemini Newsletter, 22, 1.
  • Corrigan, R.T. et al, 1990, "Gravitational lensing; Proceedings of the Workshop, Toulouse, France, Sept. 13-15, 1989", Berlin and New York, Springer-Verlag, 1990, p. 206-209


Spectroscopic observations with the INT led to the discovery of 3 quasars with a redshift of z > 4. Prior to these observations only one of these objects was known.

Adaptive optics was employed on the WHT and sharpened stellar images from a diameter of 0.65 arcseconds to 0.35 arcseconds.

Faint steep spectrum radio sources, which seem to be systematically more luminous than normal sources, have been optically identified using the INT, and spectroscopically examined using the WHT. 

The WHT and INT have been used to observe radio-loud quasars in the expectation that they are located in clusters and surrounded by gas. Extensive optical nebulosities have been found around some quasars. Some of this gas may flow in and power the quasar nucleus.

The JKT has been used to detect shock-fronts on the concave sides of spiral arms beyond the corotation radius in spiral galaxies. This is consistent with a theory predicting that the spiral arms point in the same direction as the rotation of the galaxy.

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Last modified: 13 December 2010