Vulpecula

Vulpecula, the fox or vixen, is a small northern constellation located in the middle of the Summer Triangle, north of Sagitta and Delphinus. It does not contain any stars of magnitude less than 4.

Notable features

Vulpecula constellation

Despite lacking any bright stars—α Vulpeculae, the brightest, barely reaching magnitude 4.4—some of the key milestones in astronomy have taken place in this constellation. Among them it is worth highlighting the discovery in 1967 of the first pulsar, PSR B1919+21, located in Vulpecula; before the nature of the signal was determined, the researchers, Jocelyn Bell and her supervisor, Ph.D. Antony Hewish, seriously considered the possibility that it was a signal from extraterrestrial life. Also PSR B1937+21, the first millisecond pulsar discovered (in 1982), is located only a few degrees from PSR B1919+21.

α Vulpeculae, known as the Anser, is the only Bayer-named star in the constellation. It is a red giant of spectral type M0.5III with an effective temperature of 3863 K and a luminosity 555 times that of the Sun. It is 291 light-years from Earth.

23 Vulpeculae and 31 Vulpeculae, the second and fourth brightest stars, are yellow-orange giants of spectral type K3III and G7III respectively. The first is 375 times more luminous than the Sun and the second 54 times more. The latter is a spectroscopic binary with an orbital period of 1860 days. Somewhat dimmer, 30 Vulpeculae is also a type K1III orange giant and also a spectroscopic binary, with an orbital period of 2,506 days.

At magnitude 4.65, NT Vulpeculae is a white giant of type A4III and variable Alpha2 Canum Venaticorum. Slightly dimmer, QR Vulpeculae is a B3V-type star and a Gamma Cassiopeiae variable exhibiting brightness fluctuations of 0.2 magnitudes. T Vulpeculae, U Vulpeculae and SV Vulpeculae are three Cepheids whose periods are 4.4355, 7.9907 and 45.01 days respectively; SV Vulpeculae is a very distant star — located approximately 7,900 light years away — with a great luminosity, equivalent to 28,000 suns. Z Vulpeculae is an eclipsing binary composed of a bluish-white main sequence star of type B4V and a white giant of type A3III; during the main eclipse, the brightness of Z Vulpeculae decreases by 1.65 magnitudes, while in the secondary the brightness is only 0.33 magnitudes. By contrast, EP Vulpeculae is a cool S-type star with a luminosity 4,000 times that of the Sun. It is an irregular variable whose brightness fluctuates by 3.7 magnitudes.

HD 188015 and HD 189733 are two stars in the constellation with planetary systems. The planet orbiting the latter star, HD 189773 b, contains significant amounts of water in its atmosphere, as well as oxygen and methane. The one that orbits around HD 188015, presumably a gas giant, does so in the habitable zone of the star.

Another object of interest is Gliese 794, one of the hottest and youngest white dwarfs less than 20 parsecs from the solar system. It has a temperature of 20,700 K and an estimated age—as a stellar remnant—of only 60 million years. Also in Vulpecula is GJ 4166, the least massive white dwarf in our environment, with a mass equivalent to 25% of the solar mass.

Planetary nebula Hen 2-437 (Credits: ESA/Hubble & NASA)

Among the deep sky objects, the planetary nebula M27 or Dumbbell Nebula stands out, the first nebula of this type to be discovered, being described by Charles Messier in 1764. Its central star, a white dwarf, has an estimated radius equal to at 5.5% of the solar radius and is the largest known white dwarf. According to the parallax measured by the GAIA space observatory, M27 is 1,230 light-years from Earth. Another observable planetary nebula in Vulpecula is Hen 2-437, a bipolar nebula where the material ejected from the dying star has spread out into two symmetrical blue lobes.

NGC 6820 is an emission nebula that surrounds the open cluster NGC 6823, formed about two million years ago and in which its young blue stars stand out. It is located about 6,000 light years from Earth.

In Vulpecula you can also observe the elliptical galaxy NGC 7052. The Hubble Space Telescope has discovered a thick disk of dust 3,700 light-years in diameter that may be the remnant of a galactic collision in the past.

The eastern part of Vulpecula is covered by the Hercules-Corona Borealis Great Wall. It is a galactic filament with a length of 3,000 megaparsecs, making it the largest structure in the observable universe.

Main Stars

Artistic conception of the planet HD 189733 b, after confirmation (in 2013) of the blue color of this planet.

• α Vulpeculae (Anser), of visual magnitude 4,44, a red giant to 291 light years of the solar system.
• 1 Vulpeculae, white-smooth subigant of magnitude 4,76.
• 3 Vulpeculae, blue giant of magnitude 5,22; it is a slow pulsating B star (SPB).
• 13 Vulpeculae, third brightest star of the constellation with magnitude 4,58; it is a double star whose main component is a white-azulada giant.
• 15 Vulpeculae (NT Vulpeculae), variable of the Alfa2 Canum Venaticorum type, white star.
• 21 Vulpeculae (NU Vulpeculae), Delta Scuti variable of magnitude 5.20.
• 23 Vulpeculae, the second star in brightness with magnitude 4,52, an orange giant.
• 28 Vulpeculae, white-smooth subigant of magnitude 5.04.
• 29 Vulpeculae, white star of magnitude 4,82.
• 30 Vulpeculae, orange giant and spectroscopic binary of magnitude 4,93.
• 31 Vulpeculae, yellow giant of magnitude 4,58.
• T Vulpeculae, a strained variable whose brightness ranges between magnitude 5,41 and 6.09 in a period of 4,4355 days.
• U Vulpeculae, also strained variable; its brightness varies between magnitude 6.73 and 7.54 in a period of 7,9907 days.
• Z Vulpeculae, variable shimmering binary between magnitude 7.25 and 8.90.
• RR Vulpeculae, 10,00 eclipsing binary.
• SV Vulpeculae, distant long-term cefeide (45.01 days).
• WW Vulpeculae, young star Herbig Ae surrounded by a circum-stellar disk.
• EP Vulpeculae, type S star and irregular variable.
• ER Vulpeculae, binaria with chromosopheric activity of magnitude 7.36.
• PY Vulpeculae, pulsating white dwarf, one of the most brilliant in this group.
• QR Vulpeculae, variable of apparent average magnitude 4.76.
• HD 189733, a yellow-orange star of the main sequence with a giant gaseous planet very close to the star.
• HD 188015, a yellow subgiant star at 172 light years, with a planet in the so-called living area.
• Gliese 794, hot white dwarf of magnitude 11,55 composed mainly of hydrogen. It is located 48 light years from Earth.
• WR 126, peculiar and distant star of Wolf-Rayet that can be more than 14 000 light years.
• PSR B1919+21, the first pulsar discovered in 1967 by Jocelyn Bell and Antony Hewish, with an interval of 1.3373 s.

Deep Sky Objects

Image of M27 obtained by the VLT of the European Southern Observatory

• M27 planetary nebula or Dumbbell Nebula, of magnitude 7.5, the first uncovered planetary nebula. He's an estimated age of 9800 years. It is approximately 1230 light years away from Earth.
• NGC 6820, emission nebula surrounding the NGC 6823 open cluster, located near M 27.
• Resto de supernova SNR G057.2+00.8; it houses in magnetar SGR J1935+2154, the most active one known.
• NGC 6885, distant open cluster 1950 light years.
• NGC 7052, elliptical galaxy. Of apparent magnitude 13,4, it is approximately 191 million light years away. This galaxy is an important fuss.
• Asterism Collinder 399, also known as "La Percha" due to its shape. In the past this object was listed as an open cluster by Per Collinder (1931); however, several independent studies since 1998 have determined that the object is not a true cluster at all, but merely a casual alignment of stars.

History

Vulpecula et Anser en la Uranographia.

This constellation, devised by Johannes Hevelius in 1690, is not associated with any interesting legend or mythological reference. Initially it was called Vulpecula Cum Anser, the Fox with the Goose, but today it is known simply as Vulpecula (the Fox).