Hubble Space TelescopeMolly Rose Guiyun Merkert, Colorado College

BackgroundThere are two types of optical telescopes: refracting telescopes (uses lenses) and reflecting telescopes (uses mirrors). Refracting telescopes can be affected by to chromatic aberration (where light of different wavelengths focus at different locations). This does not happen in reflecting telescopes.

Observations from Earth based telescopes are often impeded by clouds, light pollution, and astronomical seeing (unpredictable changes in the atmosphere that bend light going through it).

Diffraction patterns are created when a point light source (like a laser or star) illuminates a sharp edged object.

The Hubble Space Telescope● Agencies: NASA, ESA, & STScI● Launch: April 24, 1990● Size: 43.5 ft x 14 ft x 40 ft

● Weight: 24,500 pounds

● Ritchey-Chretien Cassegrain

● Primary Mirror: 94.5” diameter

The FutureThe Hubble Space Telescope will stop functioning. The telescope slowly loses altitude each year as well; eventually it will fall to Earth. However before that, the gyroscopes that are used to point the telescope will wear out.

However, in the future, the James Webb Space Telescope will be sent to space and the European Extra Large Telescope will use lasic adaptive optics to counter astronomical seeing.

COSTAR and Tiny TimTo solve the problems with telescope’s mirror, COSTAR was installed in December 1993. This arrangement of five mirrors bent the light rays to focus at the same place. COSTAR was removed in 2009.

A computer program called Tiny Tim is used to determine star diffraction patterns. If an object deviates too much from this pattern, it is probably not a star.

DiscoveriesOver the past 29 years, the Hubble Space Telescope has observed known objects in higher detail and has been used to confirm theories (like the existence of black holes). It has also been used to research cosmology, dark matter, gravitational lensing, and cosmic expansion. The Hubble Space Telescope has also discovered so many space objects, especially through its deep field images.

AcknowledgmentsSpecial thanks to Professor Shane Burns

and Professor Stephanie DiCenzo“About the James Webb Space Telescope.” NASA, NASA, jwst.nasa.gov/about.html.

Burns, Shane. A Practical Guide to Observational Astronomy. 2017.

Chaisson, Eric J. The Hubble Wars: Astrophysics Meets Astropolitics in the Two-Billion-Dollar Struggle over the Hubble Space Telescope. Harvard University Press, 1998.

Chromey, Frederick R. To Measure the Sky: an Introduction to Observational Astronomy. Cambridge University Press, 2010.

Giancoli, Douglas C. Physics for Scientists & Engineers with Modern Physics. Pearson, 2009.

“Hubble's Top Breakthroughs.” HubbleSite - Hubble Breakthroughs - Home, NASA, hubblesite.org/hubble_discoveries/breakthroughs/.

Petersen, Carolyn Collins., and John C. Brandt. Hubble Vision: Astronomy with the Hubble Space Telescope. Second ed., Cambridge University Press, 1998.

Sparrow, Giles. Hubble: Legacy Edition. Quercus, 2014.

webteam@eso.org. “The European ELT.” ESO, www.eso.org/sci/facilities/eelt/.

How good is Hubble?We can measure how good a telescope is by using the Rayleigh Criterion. It gives the angle needed between two light sources (or stars in this case) for the two sources to be seen as separate objects. For telescopes, this is given by:

where Ө is the angle (in radians) between the two stars, λ is the wavelength of the light, and D is the diameter of the primary mirror.

For the Hubble Space Telescope (with COSTAR), this angle is 0.05 arcseconds. An Earth bound telescope has a limiting resolution of about 1 arcsecond under optimal conditions.

Primary Mirror ProblemA flaw in the telescope’s primary mirror caused the light focus at different places, causing a halo to appear around objects.

Globular Star Cluster M-14 (spacetelescope.org)Left: 4-meter telescope at Cerro Tololo Inter-American Observatory has a resolution of 1.5 arcsecondsRight: Faint object camera has a resolution of 0.08 arcseconds

F1042M Diffraction Patterns (stsci.edu)Left: An image taken by the Hubble Space TelescopeRight: The diffraction pattern created by Tiny Tim

M100 (spacetelescope.org)Left: An image taken by the Hubble Space TelescopeRight: The same object taken with COSTAR installed.

Mirror Flaw (The Hubble Wars)The primary mirror was only 2 microns too flat at the edges.

Strange Halo (spacetelescope.org)The halo around 30 doradus is caused by the problem in the primary mirror.

Hubble Space Telescope (spacetelescope.org)The release of the HST on April 24, 1990.

Diffraction Patterns (britannica.com)An image explaining why diffraction patterns occur.

HST Design (The Hubble Wars)An image of the Ritchey-Chretien Cassegrain optical design

Hubble Deep Field (spacetelescope.org)Approximately 27 million galaxies can be seen in this image from a seemingly empty section of space. Taken in 1995.

aXtreme Deep Field (nasa.gov)A more recent deep field image from 2012

HST Pattern (iopscience.iop.org)What the diffraction pattern from Hubble Space Telescope’s aperture should look like