From sasha@khors.Stanford.EDU Thu Dec 19 11:09:40 1996 Return-Path: Received: from khors.Stanford.EDU by quake.Stanford.EDU with SMTP (5.65/25-QUAKE-eef) id AA02194; Thu, 19 Dec 1996 11:09:30 -0800 Received: (from sasha@localhost) by khors.Stanford.EDU (8.7.1/8.6.6) id LAA12661; Thu, 19 Dec 1996 11:09:30 -0800 (PST) From: "Alexander Kosovichev" Message-Id: <9612191109.ZM12657@khors.Stanford.EDU> Date: Thu, 19 Dec 1996 11:09:29 -0800 X-Mailer: Z-Mail (3.2.0 26oct94 MediaMail) To: local@quake.Stanford.EDU, jkuhn@solar Subject: Satellite discovers the sun is covered with bumps Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="PART-BOUNDARY=.19612191109.ZM12657.Stanford.EDU" Status: R --PART-BOUNDARY=.19612191109.ZM12657.Stanford.EDU Content-Description: Text Content-Type: text/plain ; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable X-Zm-Decoding-Hint: mimencode -q -u [TheSan Francisco Examiner] Main News Sports Business Style Commentary Examiner Home The Gat= e -------------------------------------------------------------------------= --- Wednesday, Dec. 18, 1996 =B7 Page A 13 =A9 1996 San Francisco Exam= iner -------------------------------------------------------------------------= -- Satellite discovers the sun is covered with bumps Scientists have no explanation for strange hills 40,000 miles wide Keay Davidson EXAMINER SCIENCE WRITER Here's the latest news from the hottest place in the solar system: 1. It's got bumps, and 2. Albert Einstein can rest in peace. Schoolchildren are taught the sun is shaped like a sphere. Later, in high school or college, they learn it's actually more like a flattened melon, with a love handle-like bulge around its middle. But scientists have debated the exact size and shape of the sun for decades. At stake is a venerable idea, Einstein's theory of general relativity, the bedrock of modern cosmology. Now, while trying to measure the sun's shape using a space satellite, scientists from Stanford University and other institutions have made an unexpected discovery. The sun is covered with enormous "bumps," each one about 40,000 miles wide - five times the diameter of Earth - but very low, like flattened hills, roughly a few thousand feet high. "It's extremely exciting. It's the kind of thing that, having seen, we definitely want to understand," space scientist Ed Rhodes of USC said Tuesday at the American Geophysical Union conference at Moscone Center. Scientists have no explanation for the bumps. They may be like bubbles atop a boiling pot of water and, therefore, a hint of the convective forces churning away within the sun. Or they may reveal how the sun's tangled magnetic field molds its super hot surface of ionized gases and free-flying electrons. The satellite "is a very powerful telescope with which we can see marvelous things which nobody can understand. I fear here we are in heavy water where simple solutions won't suffice," said Werber Dappen of USC. Unlike water-pot bubbles, the sun's bumps are remarkably stable, lasting at least a month each. The discovery was made by a scientific instrument aboard the $1 billion solar and heliospheric observatory or SOHO, launched last year by NASA. Stanford scientists involved in the discovery were Phil Scherrer, Rock Bush, Rick Bogart and Luiz Sa. The instrument - the $75 million Michelson doppler imager, or MDI - was built by scientists from Stanford and Lockheed in Sunnyvale. The MDI is so sensitive that it can detect a change in the sun's shape as slight as 10 feet. "That's as precise as measuring something as small as a quarter on the moon," said Jeffrey Kuhn of the National Solar Observatory in Sunspot, N.M. MDI is doubly aptly named. Doppler refers to the technique by which it measures solar shape - by gauging subtle Doppler shifts in the frequency of sunlight as the Sun quakes like a huge bowl of Jell-O. And Michelson refers to Albert Michelson, a 19th century U.S. physicist who, with Edward Morley, discovered that the speed of light never changes. Their finding paved the path to Einstein's theory of general relativity, a new theory of gravity. The Einstein theory's most celebrated application occurred in 1919. Scientists used it to correctly forecast that during a total eclipse, the Sun's gravitational field would shift the apparent position of a nearby star. Despite that success, skeptics pointed out the forecast was based on the assumption the sun was a slightly flattened - oblate - sphere. What, they asked, if it's really more or less oblate than assumed? That might invalidate Einstein's forecast. For this and other reasons, astronomers spent a few decades trying to precisely measure the sun's shape. In the 1970s, some experts said the sun is tubbier than Einstein assumed - 10 miles wider along its equator than measured from pole to pole. Now SOHO has come to Einstein's rescue by observing the sun from space, unhampered by Earth's turbulent atmosphere. SOHO shows the sun is fairly slim, only "a mile shorter than it is fat," Kuhn said. This "tells us general relativity as Einstein conceived it is safe." --PART-BOUNDARY=.19612191109.ZM12657.Stanford.EDU--