Researchers report long hidden properties of Polaris

July 30, 2018, Villanova University
Researchers report long hidden properties of Polaris
Credit: Villanova University

Two Villanova University astrophysics professors led a research team that has discovered the long hidden physical properties of Polaris, popularly known as "The North Star." Until now, scientists' wide-ranging estimates of the star's distance from the Earth (322-520 light years), made determining its physical makeup difficult. But, equipped with precise distance measurements recently made by the European Space Agency's (ESA) Gaia Mission (447+/- 1.6 light years), the Villanova team has been able to determine Polaris's radius, intrinsic brightness, age and mass.

Polaris is our nearest Classical Cepheid, one of a rare and important class of very luminous supergiant stars that pulsate. The relation between (luminosity) and pulsation period permits Cepheids to be used as "standard candles" for measuring the distances to galaxies both near and far.

"The previous large uncertainty in the distance to Polaris was a real impediment to pinning down the properties of our nearest (and dearest) Cepheid. The Gaia Mission measured its distance to better than one-half percent," said Guinan. "Working with a precise distance measurement opens up new paths for research into the structure and evolution of Polaris and other Cepheids."

The research team, consisting of principal investigators Research Assistant Professor Scott Engle, Ph.D., and Professor of Astronomy and Astrophysics Edward Guinan, Ph.D., in Villanova's Department of Astrophysics and Planetary Science, as well as Petr Harmanec, DrSc., from the Astronomical Institute at Charles University, Prague, CZ, published its findings in the July 16 issue of Research Notes of The American Astronomical Society. The article, "Toward Ending the Polaris Parallax Debate: A Precise Distance to Our Nearest Cepheid from Gaia DR2," explains the importance of this breakthrough for further study of Polaris, which it says, "serves as an important astrophysical laboratory" for studying stellar pulsation, Cepheid properties, evolution and structure."

"Our study of Polaris provides a clearer understanding of Cepheid variable stars as a class," continued Guinan. "Cepheids are fundamentally important for determining the distances to galaxies and the expansion rate of the universe. All but a few are too far away to determine their fundamental physical properties with the precision now provided by Polaris."

"It's always exciting when new technology or tools are able to settle old debates," said Engle. "Cepheids are such fundamentally important to begin with, and Polaris in particular has long been of great interest. Determining its and stellar properties with such precision is exciting in regard to the star itself, but is a great example of what further studies can be expected with the current (and future) Gaia data."

Explore further: Astronomers clash over the distance to the famed North Star

More information: Scott G. Engle et al. Toward Ending the Polaris Parallax Debate: A Precise Distance to Our Nearest Cepheid from Gaia DR2, Research Notes of the AAS (2018). DOI: 10.3847/2515-5172/aad2d0

Related Stories

Astronomers clash over the distance to the famed North Star

November 30, 2012

(Phys.org)—The North Star (Polaris) has played an important role in human history, yet knowledge of its fundamental parameters is unsatisfactory. That problem is attributable in large part to uncertainties tied to the star's ...

The Polaris Cluster

May 28, 2010

(PhysOrg.com) -- A Cepheid star is one whose mass and age results in physical conditions that generate periodic oscillations in its photosphere. A Cepheid thus varies regularly in brightness, with a period proportional to ...

There's More to the North Star Than Meets the Eye

January 9, 2006

We tend to think of the North Star, Polaris, as a steady, solitary point of light that guided sailors in ages past. But there is more to the North Star than meets the eye - two faint stellar companions. The North Star is ...

Cepheids and their 'cocoons'

February 28, 2006

Using ESO's Very Large Telescope Interferometer (VLTI) at Cerro Paranal, Chile, and the CHARA Interferometer at Mount Wilson, California, a team of French and North American astronomers has discovered envelopes around three ...

Recommended for you

Sprawling galaxy cluster found hiding in plain sight

August 16, 2018

MIT scientists have uncovered a sprawling new galaxy cluster hiding in plain sight. The cluster, which sits a mere 2.4 billion light years from Earth, is made up of hundreds of individual galaxies and surrounds an extremely ...

Hubble paints picture of the evolving universe

August 16, 2018

Astronomers using the ultraviolet vision of NASA's Hubble Space Telescope have captured one of the largest panoramic views of the fire and fury of star birth in the distant universe. The field features approximately 15,000 ...

Unusual doughnut-shaped jet observed in the galaxy NGC 6109

August 15, 2018

Astronomers from the University of Bristol, U.K., have uncovered an unusual doughnut-shaped jet in the radio galaxy NGC 6109. It is the first time that such a jet morphology has been observed in a low-power radio galaxy. ...

Iron and titanium in the atmosphere of an exoplanet

August 15, 2018

Exoplanets, planets in other solar systems, can orbit very close to their host stars. When the host star is much hotter than the sun, the exoplanet becomes as hot as a star. The hottest "ultra-hot" planet was discovered last ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

Nik_2213
5 / 5 (4) Jul 30, 2018
Now the fun really starts.

Having a secure distance to Polaris & Co. will re-calibrate most Cepheid measurements. IIRC, Cluster-based findings were already robust...

But WHY did some Hipparcos ranging differ so significantly from other approaches ? Given there have been other 'odd' H findings, my amateur reading suggests the close-binary nature fooled H's sensors. Unresolved orbital motion munging parallax ? IMHO, this could open some fun research avenues...

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.