Quantcast

In the Know: Measuring brightness of astronomical objects

Under the magnitude scale, the stars with the smallest magnitude are the brightest while stars with the largest magnitude are the faintest. AFP PHOTO/ARMAGH OBSERVATORY

MANILA, Philippines—Astronomers use a magnitude scale to measure the stellar brightness of astronomical objects.

The ancient Greek astronomer Hipparchus introduced the magnitude system. He categorized the stars into six magnitudes with the brightest stars assigned to the first magnitude and the faintest to the sixth magnitude.

So under the magnitude scale, the stars with the smallest magnitude are the brightest while stars with the largest magnitude are the faintest.

With the advent of telescopes and other modern equipment to aid the human eye, the scale has been extended in both directions.

According to the scientific journal International Comet Quarterly (ICQ), an astronomical object with a -4 could be easily seen with the naked eye even from large cities.

Those with magnitude zero could be seen with the naked eye and generally visible even from large cities, but are difficult to see if near bright artificial lights.

Sirius, the brightest star, shines at visual magnitude -1.5, the ICQ notes.

The comet’s magnitude, however, is called “total visual magnitude” which ICQ describes as magnitude integrated over an observed coma diameter of several arc minutes.

This means a seventh magnitude comet is more difficult to see than a seventh magnitude star, with the latter having all its light in a pinpoint while the former having the same amount of light spreads out over a large area, the ICQ explained.—Inquirer Research

Sources: http://www.icq.eps.harvard.edu, http://spacemath.gsfc.nasa.gov, https://www.e-education.psu.edu/, http://www.stargazing.net/david/constel/magnitude.html


Follow Us




Other Stories:




Recent Stories:

Complete stories on our Digital Edition newsstand for tablets, netbooks and mobile phones; 14-issue free trial. About to step out? Get breaking alerts on your mobile.phone. Text ON INQ BREAKING to 4467, for Globe, Smart and Sun subscribers in the Philippines.



Copyright © 2014, .
To subscribe to the Philippine Daily Inquirer newspaper in the Philippines, call +63 2 896-6000 for Metro Manila and Metro Cebu or email your subscription request here.
Factual errors? Contact the Philippine Daily Inquirer's day desk. Believe this article violates journalistic ethics? Contact the Inquirer's Reader's Advocate. Or write The Readers' Advocate:
c/o Philippine Daily Inquirer Chino Roces Avenue corner Yague and Mascardo Streets, Makati City, Metro Manila, Philippines Or fax nos. +63 2 8974793 to 94
Advertisement
Advertisement
Marketplace