Weekly Online Lesson Online Lesson Archives Grade Level: 9-12 Subject: Science

We're Not Alone

It seems we're not alone in the Universe. While scientists still haven't proven the existence of extraterrestrial life (life on a world other than Earth), astronomers from four different institutions of research announced on April 15, 1999, that they have found evidence of another solar system in our galaxy. The newly discovered system is composed of three Jupiter-sized planets orbiting the star Upsilon Andromedae.

This is big news in astronomy circles. Considering that astronomers have surveyed only 107 stars (out of the 200 billion stars in the galaxy), the new finding suggests that planetary systems like ours may be abundant in the galaxy. It is also changing the way scientists think about the formation of planets. You can read more about this announcement and it's ramifications for science at Astronomy Online, Britain's leading astronomy magazine.

If you are using a browser with Real Video capabilities, watch the BBC's excellent 2-minute video report on the discovery. CNN's coverage of the announcement likewise includes Real Video coverage, as well as QuickTime animation of the Upsilon Andromedae planetary orbits.

This week's online lesson sets it's sights on a star 44 light years from our own, and on the search for extrasolar planets and planetary systems. It's not just out of this world—it's out of this solar system.

SFSU Physics

In 1996, San Francisco State University astronomer Geoffrey Marcey and his colleague R. Paul Bulter (who works at the Anglo-Australian Observatory) found evidence of a planet in close orbit around Upsilon Andromedae. Data from telescope observations at Lick Observatory near San Jose, CA, now suggests that two other giant planets are in orbit around the sun-like star.

Pay a visit to San Francisco State University's Department of Physics and Astronomy and click on the Upsilon Andromedae orbit chart, which will take you to Discovery of Extrasolar Planets.

Begin by scrolling down and clicking Introduction to Extrasolar Planets. Here you will find links to news stories and journal articles about the work of Marcey and Butler. In particular, read the article these two astronomers wrote for Scientific American entitled "Giant Planets Orbiting Faraway Stars" (3/98). It contains a good background on extrasolar planetary exploration. Consider also reading an earlier Scientific American article entitled "A Parade of New Planets" (5/96).

Now go back to Discovery of Extrasolar Planets and follow the link to Upsilon Andromedae: A Multiple Planet System, where you will find a description of the three-planet orbital chart. How did Marcey and Butler know the planets were there? After all, these planets are far too distant to be observed directly. By reading this description you will be able to follow theoretical detective work that led to their discovery.

You can learn more about Marcey, Butler, and other members of the SFSU Planet Search Team by visiting their individual sites.

Harvard-Smithsonian Center for Astrophysics

About the time Marcey and Butler were confirming the results of their research, scientists at the Harvard-Smithsonian Center for Astrophysics were arriving at the same conclusion. Their findings were based on measurements taken from Whipple Observatory, near Tuscon Arizona, using an instrument called the Advanced Fiber-Optic Eschelle (AFOE) spectrometer. You can read a more detailed description of AFOE and how it helped unlock a stellar secret by visiting this site.

Other sites of interest at Harvard-Smithsonian include a description of the Upsilon Andromedae Planetary System, along with several animated Java simulations of the orbits, and a copy of the official press release. You can also browse the Extrasolar Planets Encyclopedia, featuring the Extrasolar Planets Catalog of all known planets outside our solar system. Just don't get any ideas about buying one of these planets online—it's not that kind of catalog.

If by now your curiosity is peaked, and you'd like to have a first-hand look at the star with a confirmed solar system in orbiting, look at the Constellation Andromedae chart, which will give you complete directions for locating it.

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