Photometry in Astronomy

How photometry is used in Astronomy for our understanding of space.

What is Photometry ?

Photometry in Optics

Photometry is the study of light in terms of its perceived brightness to human eye. It is concerned with quantifying the amount of light that is emitted, transmitted, or received by an object or a system.

Photometry in astronomy

In astronomy, photometry is the study of light radiated by astronomical objects to study celestial bodies.

Basic Methodology

Astronomy was among the earliest applications of photometry. Modern photometers use specialised standard passband filters across the ultraviolet, visible, and infrared wavelengths of the electromagnetic spectrum Any adopted set of filters with known light transmission properties is called a photometric system, and allows the establishment of particular properties about stars and other types of astronomical objects. Several important systems are regularly used, such as the UBV system (or the extended UBVRI system), near infrared JHK or the Strömgren uvbyβ system.

Applications

There are many astronomical applications used with photometric systems. Photometric measurements can be combined with the inverse-square law to determine the luminosity of an object if its distance can be determined, or its distance if its luminosity is known. Other physical properties of an object, such as its temperature or chemical composition, may also be determined via broad or narrow-band spectrophotometry.

Organizations

There are a number of organizations, from professional to amateur, that gather and share photometric data and make it available on-line. Some sites gather the data primarily as a resource for other researchers (ex. AAVSO) and some solicit contributions of data for their own research (ex. CBA):

1. American Association of Variable Star Observers
2. Astronomyonline.org
3. Center for Backyard Astrophysics (CBA)

The information here is borrowed from Wikipedia.