A New Class of Variable Stars Revealed

February 26, 2010

(PhysOrg.com) -- Modern astronomy sometimes makes discoveries by looking in new places, the distant universe for example, using telescopes and instruments that extend the previous limits of detection.

But sometimes new discoveries can come from applying modern technologies to the task of more carefully examining conventional data.

The Harvard College Observatory maintains a collection of more than 500,000 glass photographic plates of the sky taken over a century - from between about 1880 and 1980. They constitute the only continuous record of the whole sky in existence for this period, with every point on the sky having been observed between 500 and 1000 times.

The Digital Access to a Sky Century at Harvard (DASCH) is a project now underway to digitize all of these plates and search for changes. In one of the first results of this ongoing program, a new class of variable has been discovered.

Variable stars are stars that change in brightness. They can do so for many reasons, from explosions as to pulsations in their atmospheres to eclipses in binary star systems. Sometimes the changes are periodic and other times erratic, but by far most known variable stars change noticeably in short times - over time scales of less than a year. Variable stars came as quite a shock when they were discovered in the early 1600's because people thought that the stars were cosmic constants, but today variable stars seem rather matter-of-course.

CfA astronomers Sumin Tang, Jonathan Grindlay, and Edward Los, together with a colleague, used the first results of the DASCH project to discover three objects in what appears to be a new class of variable stars that change in optical brightness (both dimming and brightening) by more than a factor of two over a timescale of 10-100 years.

This kind of variation has never been seen before; imagine if the sun were to vary in brightness by a factor of two in a century!

The astronomers use follow-up spectroscopic observations to report that the three stars are similar to one another, and are slightly less massive and older than the sun.

They suggest that the cause of variability could be related to the production of dust, or perhaps involve changes in the nuclear reactions underway. Once DASCH has found other stars of this type, and more detailed follow-up studies can be be undertaken, this new kind of variable star can add the details of its aging personality to our understanding of what happens as stars evolve.

Explore further: Symbiotic Stars

Related Stories

Symbiotic Stars

February 22, 2010

(PhysOrg.com) -- Many, perhaps even most stars, are members of binaries -- two stars that orbit each other. Symbiotic stars are a small subset of binaries with an attitude: they display characteristic, dramatic, episodic ...

Building a stellar time machine

July 7, 2009

(PhysOrg.com) -- Harvard researchers are building a celestial time machine that lets astronomers look back at hundreds of thousands of objects in the Earth’s skies over the past century.

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 ...

Turbulence May Promote the Birth of Massive Stars

February 23, 2009

(PhysOrg.com) -- On long, dark winter nights, the constellation of Orion the Hunter dominates the sky. Within the Hunter's sword, the Orion Nebula swaddles a cluster of newborn stars called the Trapezium. These stars are ...

Recommended for you

The initial mass function

December 11, 2017

The gas and dust in giant molecular clouds gradually come together under the influence of gravity to form stars. Precisely how this occurs, however, is incompletely understood. The mass of a star, for example, is by far the ...

JPL deploys a CubeSat for astronomy

December 8, 2017

Tiny satellites called CubeSats have attracted a lot of attention in recent years. Besides allowing researchers to test new technologies, their relative simplicity also offers hands-on training to early-career engineers.

Galaxy orbits in the local supercluster

December 8, 2017

A team of astronomers from Maryland, Hawaii, Israel, and France has produced the most detailed map ever of the orbits of galaxies in our extended local neighborhood, showing the past motions of almost 1400 galaxies within ...

Black holes' magnetism surprisingly wimpy

December 7, 2017

Black holes are famous for their muscle: an intense gravitational pull known to gobble up entire stars and launch streams of matter into space at almost the speed of light.


Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Feb 26, 2010
This just goes to show how archival plate collections, properly managed and scanned into the digital age, can be an immense treasure trove of information. IIRC, a young Bradley Schaefer first looked for optical images (by light-table blink comparators) of gamma-ray bursters using the HCO photographic archives.
not rated yet Feb 26, 2010
I hope they stick with the research on this particular object and better define the cause of variability.

*waves hand* Must be dust!
not rated yet Feb 26, 2010
I can remember one of Dr. Scheafer's papers actively discussing the possibility of "firefly' emission on several of the Harvard plates. No stone was left unturned.

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.