August 2015: Hunt the cosmic glow

This month’s issue of Astronomy magazine describes the search for the source of the faint light of the extragalactic background, takes a fresh look at our robotic exploration of Mars, explores the fight to save aging observatories in the era of big data, previews the March total solar eclipse in Indonesia, and more.
By | Published: June 29, 2015 | Last updated on May 18, 2023
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WAUKESHA, Wis. — The universe glows with light of every color and wavelength, and scientists only know where some of that light comes from. While the cosmic microwave background has been stealing the spotlight in recent years, astronomers have been more quietly hunting the extragalactic background light (EBL) of every other kind, from the visible light our eyes see out to X-rays and gamma rays. To find this low-level glow, they must peer through the bright lights of nearby sources like our Sun and the cloud of glowing dust enveloping the solar system, and look past the gleaming band of the Milky Way and its billions of stars, as well as the other millions of galaxies that pepper our view of the cosmos. Finding this dim signal is no easy task.

In “Searching for the universe’s background glow,” Contributing Editor Liz Kruesi guides you through the many ways astronomers hunt the EBL and uncover where the various wavelengths come from. Some of these techniques directly count light from galaxies, while others use indirect methods, such as measuring the light that doesn’t make it to sensitive telescopes. Kruesi explores both the history of the EBL’s discovery and the work still ongoing with telescopes around the world and beyond in space.

To learn more about what’s causing the EBL’s cosmic glow, pick up the August 2015 issue of Astronomy magazine, on newsstands July 7.

“A fresh look at Mars”
Planetary scientist Jim Bell reviews the armada of spacecraft exploring the Red Planet and their latest and most exciting discoveries in “A fresh look at Mars.” The fleet currently includes two active rovers and five orbiting satellites from the American, European, and Indian space programs. They map the planet’s surface, perform geologic and atmospheric studies, and dig ever deeper into the potential for habitability, both past and present.

“Kitt Peak Observatory’s new lease on life”
As the world of research astronomy moves farther away from directed individual projects and toward larger and usually automated surveys, it leaves less time and funding for small groups — or small telescopes, even those considered large and cutting edge only a few decades ago. In “Kitt Peak Observatory’s new lease on life,” Associate Editor Eric Betz reports on how observatories — Kitt Peak in Arizona and others — are adapting to the changing times and technologies.

“Finding our place in the Milky Way”
Humankind longs to understand its place in the cosmos. Determining our position is a task that stretches back to Aristarchus in the third century B.C. and is still ongoing today as we struggle to map the galaxy we inhabit. How did we come to understand the distances to the stars, the shape of the Milky Way, and our place in it? Alan Goldstein retraces the steps to discovering these answers in “Finding our place in the Milky Way.”

August sky events visible without optical aid

  • August 13 — The Perseid meteor shower peaks under Moon-free skies.
  • August 29 — Venus and Mars share the eastern predawn sky.

Also in the August 2015 Astronomy

About Astronomy magazine:
Astronomy offers you the most exciting, visually stunning, thorough, and timely coverage of the heavens above. Each monthly issue includes expert science reporting, vivid color photography, complete sky-event coverage, spot-on observing tips, informative equipment reviews, and more. All of this comes in an easy-to-understand user-friendly style that’s perfect for astronomers at any level. Contact Astronomy, the world’s best-selling astronomy magazine, at 262.796.8776 or email