New Evidence for Planets Orbiting a Pulsar

By Cowen, Ron | Science News, March 5, 1994 | Go to article overview
Save to active project

New Evidence for Planets Orbiting a Pulsar


Cowen, Ron, Science News


After 2 years of additional study, a radioastronomer reports "irrefutable" evidence confirming the existence of two planets orbiting a dense Milky Way star. Estimated at about three times the mass of Earth, these planets would be the first identified outside the solar system.

Alexander Wolszczan of Pennsylvania State University in University Park reported his initial planetary finding in 1992, after studying radio emissions from a compact star some 1,300 light-years from Earth. Now dubbed PSR B1257+12, this dense resident of the Virgo constellation is a millisecond pulsar - a neutron star that rotates like clockwork hundreds of times a second. A millisecond pulsar acts like a lighthouse beacon, aiming radio waves toward Earth at precise intervals.

But in studying the pulsar with the 305-meter radio telescope at Arecibo Observatory in Puerto Rico, Wolszczan detected small fluctuations in the arrival time of the star's radio signals. Some of the waves arrived about three-thousandths of a second sooner than predicted, while others arrived about three-thousandths of a second later.

The variations suggested that the pulsar wobbles, moving closer to and farther from Earth in a quasiperiodic fashion. Wolszczan and a colleague concluded that the best explanation for the wobbling would be the gravitational tug supplied by two or possibly three unseen planets orbiting the pulsar (SN: 1/11/92, p.20).

Because it's unlikely that current telescopes could detect the dim, faraway planets directly, Wolszczan searched for other ways of verifying his finding. In the Jan. 23, 1992 NATURE, a team of astronomers, including Frederic A. Rasio, now at the Institute for Advanced Study in Princeton, N.J., suggested a strategy, Given the special relationship between the orbital periods of two of the proposed planets, their mutual gravitational tug should produce a tiny additional wavering of the pulsar's radio signals.

The rest of this article is only available to active members of Questia

Sign up now for a free, 1-day trial and receive full access to:

  • Questia's entire collection
  • Automatic bibliography creation
  • More helpful research tools like notes, citations, and highlights
  • Ad-free environment

Already a member? Log in now.

Notes for this article

Add a new note
If you are trying to select text to create highlights or citations, remember that you must now click or tap on the first word, and then click or tap on the last word.
Loading One moment ...
Project items
Notes
Cite this article

Cited article

Style
Citations are available only to our active members.
Sign up now to cite pages or passages in MLA, APA and Chicago citation styles.

Cited article

New Evidence for Planets Orbiting a Pulsar
Settings

Settings

Typeface
Text size Smaller Larger
Search within

Search within this article

Look up

Look up a word

  • Dictionary
  • Thesaurus
Please submit a word or phrase above.
Print this page

Print this page

Why can't I print more than one page at a time?

While we understand printed pages are helpful to our users, this limitation is necessary to help protect our publishers' copyrighted material and prevent its unlawful distribution. We are sorry for any inconvenience.
Full screen

matching results for page

Cited passage

Style
Citations are available only to our active members.
Sign up now to cite pages or passages in MLA, APA and Chicago citation styles.

Cited passage

Welcome to the new Questia Reader

The Questia Reader has been updated to provide you with an even better online reading experience.  It is now 100% Responsive, which means you can read our books and articles on any sized device you wish.  All of your favorite tools like notes, highlights, and citations are still here, but the way you select text has been updated to be easier to use, especially on touchscreen devices.  Here's how:

1. Click or tap the first word you want to select.
2. Click or tap the last word you want to select.

OK, got it!

Thanks for trying Questia!

Please continue trying out our research tools, but please note, full functionality is available only to our active members.

Your work will be lost once you leave this Web page.

For full access in an ad-free environment, sign up now for a FREE, 1-day trial.

Already a member? Log in now.

Are you sure you want to delete this highlight?