Did William Herschel Discover the Rings of Uranus in the 18th Century?

http://www.ras.org.uk/index.php?option=com_content&task=view&id=1185&Itemid=2

RAS PN 07/08 (NAM 04): DID WILLIAM HERSCHEL DISCOVER THE RINGS OF
URANUS
IN THE 18TH CENTURY?
Contributed by Robert Massey
16 April 2007

In a paper presented at the National Astronomy Meeting in Preston from
16 - 20 April, Dr Stuart Eves of Surrey Satellite Technology Limited
will challenge the orthodox view that the rings around the planet
Uranus
were first detected during an occultation experiment in 1977.
Remarkably, a paper presented to the Royal Society in December 1797 by
the then King's Astronomer, Sir William Herschel, (who had discovered
Uranus in 1781), includes a description of a possible ring around the
planet.

EMBARGOED FOR 00:01 BST, 16 APRIL 2007
Ref.: PN 07/08 (NAM 04)

Issued by RAS Press Officers:

Robert Massey
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E-mail: rm@xxxxxxxxxx <mailto:rm@xxxxxxxxxx>


AND


Anita Heward
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NATIONAL ASTRONOMY MEETING PRESS ROOM (16 - 20 APRIL ONLY):
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CONTACT DETAILS ARE LISTED AT THE END OF THIS RELEASE.


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DID WILLIAM HERSCHEL DISCOVER THE RINGS OF URANUS IN THE 18TH CENTURY?

In a paper presented at the National Astronomy Meeting in Preston from
16 - 20 April, Dr Stuart Eves of Surrey Satellite Technology Limited
will challenge the orthodox view that the rings around the planet
Uranus
were first detected during an occultation experiment in 1977.
Remarkably, a paper presented to the Royal Society in December 1797 by
the then King's Astronomer, Sir William Herschel, (who had discovered
Uranus in 1781), includes a description of a possible ring around the
planet. Dr Eves believes this is the first observation of the rings
that
were not seen again for almost two hundred years.

Even Herschel was unable to confirm his possible sightings, and they
were not repeated by several generations of astronomers who came after
him. (Prior to 1977, when astronomers thought that Uranus lacked
rings,
Herschel's claims were dismissed as "clearly erroneous". And even
after
1977, when the existence of the rings was finally established, it was
suggested that the rings were far too dim to have been detected by
Herschel's telescopes, and so his claim to priority was ignored).

However, a recent re-evaluation of Herschel's 1797 paper by Dr Stuart
Eves of Surrey Satellite Technology Limited, suggests that Herschel's
claim to have seen one of the rings may well have been correct.

"Herschel got a lot of things right", notes Dr Eves, "He has a ring of
roughly the correct size relative to the planet, and he also has the
orientation of this ring in the right direction. In addition, he
accurately describes the way the appearance of the ring changes as
Uranus moves around the Sun, and he even gets its colour right.
Uranus's
Epsilon ring is somewhat red in colour, a fact only recently confirmed
by the Keck telescope, and Herschel mentions this in his paper."

But if Herschel could see the Epsilon ring in the late 1700s, why did
no-one else follow up his observations in subsequent years as the
telescopes astronomers used improved? "There are several mechanisms
that
could account for this", suggests Dr Eves. "The current Cassini
satellite mission to Saturn is telling us that its rings are becoming
darker and also expanding, (becoming more diffuse), over time. If
these
same mechanisms are also operating at Uranus, then the appearance of
its
rings could have changed quite markedly over 200 years, making them
much
harder to detect." Herschel's observations could thus be proof that
planetary ring systems in our solar system are far more dynamic than
has
previously been supposed.

Dr Stuart Eves
Surrey Satellite Technology Limited
Tel: +44 (0)1483 803 803
E-mail: s.eves@xxxxxxxxxx <mailto:s.eves@xxxxxxxxxx>


From 16 to 20 April, Dr Eves can be contacted via the NAM press office
(see above).

NOTES FOR EDITORS

The 2007 RAS National Astronomy Meeting is hosted by the University of
Central Lancashire. It is sponsored by the Royal Astronomical Society
and the UK Science and Technology Facilities Council.

This year the NAM is being held together with the UK Solar Physics
(UKSP) and Magnetosphere, Ionosphere and Solar-Terrestrial (MIST)
spring
meetings. 2007 is International Heliophysical Year.


IMAGES:

These will be posted on the RAS NAM website at
www.nam2007.uclan.ac.uk/press.php

.

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