Seeing Red: Hunting Herschel's Garnet Star

Jul 17, 2013 by David Dickinson
Mu Cephei (arrowed) in the constellation Cepheus the King. (Photo & graphic by author).

Quick, what's the reddest star visible to the naked eye?

Depending on your sky conditions, your answer may well be this week's astronomical highlight.

Mu Cephei, also known as Herschel's Garnet Star, is a ruddy gem in the constellation Cepheus near the Cygnus/Lacerta border. A ranging in brightness by a factor of about three-fold from magnitudes 5.0 to 3.7, Mu Cephei is low to the northeast for mid-northern latitude observers in July at dusk, and will be progressively higher as summer wears on.

William Herschel first came across this colorful star, and gave it its nickname while surveying the region in 1783. He noted "A very fine deep garnet color" for the star, and the name stuck. He also went on to describe Mu Cephei as "A most beautiful object, especially if we look for some time at a white star before we turn our telescope to it, such as (+2.5 magnitude) Alpha Cephei, which is near at hand."

Herschel was referring to the color contrast that often occurs when suddenly being confronted with such a visually colorful object in what is often a grey-to-white universe. Curiously, Herschel also notes how earlier stellar cartographers missed this star, perhaps due to its variability. Mu Cephei varies on average over a span of 755 days, although periods as short as 100 days and as long as 12.8 years are also superimposed over the cycle.

Johann Bayer first noted this star with its Greek letter designation of Mu Cephei in the 1600's, although its variable nature was not recorded until 1848 by John Russell Hind. Hind is also famous for the discovery of another ruddy jewel and star party secret weapon, Hind's Crimson Star in the constellation Lepus.

Mu Cephei is also sometimes referred to by the Arabic name Erakis. The name brings to mind the desert world Arrakis of Dune fame, which in the fictional universe of Frank Herbert, orbits around the real world star Canopus. Where the name Erakis comes from isn't immediately clear, although there's conjecture that early star map compilers confused it with Mu Draconis.

Explore further: Survivor of stellar collision is new type of pulsating star

Related Stories

Hubble sees the remains of a star gone supernova

May 03, 2013

( —These delicate wisps of gas make up an object known as SNR B0519-69.0, or SNR 0519 for short. The thin, blood-red shells are actually the remnants from when an unstable progenitor star exploded ...

Betelgeuse braces for a collision

Jan 22, 2013

(—Multiple arcs are revealed around Betelgeuse, the nearest red supergiant star to Earth, in this new image from ESA's Herschel space observatory. The star and its arc-shaped shields could collide ...

Hubble sees J 900 masquerading as a double star

Apr 01, 2013

( —The object in this image is Jonckheere 900 or J 900, a planetary nebula—glowing shells of ionized gas pushed out by a dying star. Discovered in the early 1900s by astronomer Robert Jonckheere, ...

A burst of stars 13 billion years ago

Jun 03, 2013

( —The universe immediately following the big bang contained mostly hydrogen and some helium. All the other elements needed to make galaxies, planets, and life were formed in stellar interiors ...

Recommended for you

A star's early chemistry shapes life-friendly atmospheres

14 hours ago

Born in a disc of gas and rubble, planets eventually come together as larger and larger pieces of dust and rock stick together. They may be hundreds of light-years away from us, but astronomers can nevertheless ...

Image: X-raying the cosmos

Apr 22, 2014

When we gaze up at the night sky, we are only seeing part of the story. Unfortunately, some of the most powerful and energetic events in the Universe are invisible to our eyes – and to even the best optical ...

Mysteries of nearby planetary system's dynamics solved

Apr 22, 2014

Mysteries of one of the most fascinating nearby planetary systems now have been solved, report authors of a scientific paper to be published by the journal Monthly Notices of the Royal Astronomical Society in its ...

User comments : 0

More news stories

First-of-its-kind NASA space-weather project

A NASA scientist is launching a one-to-two-year pilot project this summer that takes advantage of U.S. high-voltage power transmission lines to measure a phenomenon that has caused widespread power outages ...

How many moons does Venus have?

There are dozens upon dozens of moons in the Solar System, ranging from airless worlds like Earth's Moon to those with an atmosphere (most notably, Saturn's Titan). Jupiter and Saturn have many moons each, ...