Vulpecula - the Little Fox

Vulpecula - the Little Fox
Vulpecula isn't a well known constellation, and its stars are dim. Yet it's interesting. It contains both the first planetary nebula and the first pulsar ever discovered, a handful of exoplanets, and part of the biggest structure in the known Universe.

History and mythology
This dim little constellation tucked away in the Summer Triangle isn't a classical constellation, so it has no associated myths. However its creator, Polish astronomer Johannes Hevelius (1611-1687), gave it a story. He named it Vulpecula et Anser (Little Fox with Goose), saying it was a fox carrying a goose to Cerberus, the three-headed beast that guarded the gates of Hades. [Urania's Mirror, photo credit: Sidney Hall] By now, the goose is no longer mentioned except as the name Anser for Vulpecula's brightest star.

Stars & planets
Vulpecula is located in the Summer Triangle, but isn't easy to see to see with the unaided eye. If we compare Vulpecula with a bright constellation like its neighbor Cygnus, the latter contains twenty stars brighter than Anser.

It's Anser's distance from us that makes it appear dim, because it's a red giant about 45 times the size of our Sun and nearly 400 times brighter. But it's also 300 light years away. If it were as close to us as Alpha Centauri, it would look nearly as bright.

Five of Vulpecula's stars are known to have planets [as of July 2018]. One of them, HD 189733 b, is the nearest transiting hot Jupiter to Earth and has been extensively studied. It was discovered as it transited its star, i.e., crossed in front of it, allowing astronomers to detect a slight drop in the amount of starlight received. A hot Jupiter is a Jupiter-sized planet orbiting very close to its star. HD 189733 b is so close to its star that it orbits in just over two Earth days.

From their study of HD 189733 b, astronomers have discovered that the exoplanet is blue and that it has significant amounts of water vapor in its atmosphere. Some oxygen and carbon dioxide were also detected. But you definitely would not want to go there. It's a gas giant with one side always facing the star, and has winds that blow at seven times the speed of sound.

LGM-1
A pulsar is a spinning neutron star. It's a remnant of a supernova explosion that followed the collapse of a massive star that ran out of fuel. Although the outer layers were explosively ejected, the core collapsed so completely that even its atoms collapsed. Electrons were squashed into the nucleus and combined with protons to form neutrons. What's left is matter so dense that a teaspoonful of it would weigh billions of tons.

The text book from my first college astronomy course doesn't even mention neutron stars. The only end point of stellar evolution was white dwarfs. Neutron stars were little more than an esoteric theoretical notion in the 1960s.

Then in 1967 Jocelyn Bell, a graduate student at Cambridge University, noted that their radio array was picking up a regular recurrence of a strong pulsating signal. She brought it to the attention of her thesis supervisor Antony Hewish. It was jokingly named LGM-1 (LGM = little green men) when it sounded a bit like an extra-terrestrial beacon. Others identified its behavior as matching what you'd expect from a rapidly rotating neutron star with a strong magnetic field.

This first discovery is now designated PSR B1919+21, and it's in Vulpecula.

Deep Sky objects
Dumbbell Nebula (Messier 27)
The best known deep-sky object in Vulpecula is the Dumbbell Nebula (Messier 27), also called the Apple Core Nebula. It was the first planetary nebula ever discovered, formed when a dying star threw off its outer layers. English astronomer John Herschel gave it the nickname because its double lobed shape resembled a bar-bell. [Photo credit: Trevor Jones]

Cluster or asterism?
A little star group was described by 10th century Persian astronomer Al Sufi (903-986) and independently discovered by Giovanni Batista Hodierna (1110-1164), but it's commonly called Brocchi's Cluster. In the 1920s Dalmiro Brocchi made a map of the cluster for the American Association of Variable Star Observers. Observers used the map to calibrate photometers, instruments to measure light intensity.

Brocchi's Cluster had been considered an open star cluster, but recent study doesn't support that. It is however an asterism, a recognizable group of stars that's part of one or more constellations. As the Coathanger, it's more convincing in the southern hemisphere than in the northern where it's upside down. (Photo credit: John Chumack)

NGC 7052
NGC 7052 is an elliptical galaxy with strong radio emissions that lies about 200 million light years away. It contains an active supermassive black hole with a mass of 300 million suns. The galaxy has a central dust disk 3700 light years across, which suggests that the galaxy is the result of an ancient galactic merger. The black hole is likely to consume the dust disk over the next few billion years.

Hercules-Corona Borealis Great Wall
Gravitational attraction holds a galaxy together, but it also pulls galaxies into clusters, galactic clusters into superclusters, and superclusters into enormous filaments and superstructures of billions of light years in size. Part of the Hercules-Corona Great Wall is in Vulpecula. It's over 10 billion light years across and is the largest and most massive structure in the known Universe.



You Should Also Read:
Johannes Hevelius
Death of a Massive Star
Searching for Exoplanets

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Content copyright © 2018 by Mona Evans. All rights reserved.
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