Observing Challenge: 6 White Dwarf Stars to See in Your Backyard Telescope

Wednesday, August 6, 2014

Observing Challenge: 6 White Dwarf Stars to See in Your Backyard Telescope

Observing Challenge: 6 White Dwarf Stars to See in Your Backyard Telescope:

Dazzlimg Sirius, with its white dwarf companion to the lower left. Credit: NASA, ESA, H. Bond (STScI) and M. Barstow (University of Leicester).

Dazzling Sirius, with its white dwarf companion to the lower left. Credit: NASA, ESA, H. Bond (STScI) and M. Barstow (University of Leicester).

Looking for something off beat to observe? Some examples of curious astronomical objects lie within the reach of the dedicated amateur armed with a moderate-sized backyard telescope. With a little skill and persistence, you just might be able to track down a white dwarf star. Unlike splashy nebulae or globular clusters, a white dwarf star will just appear as a speck, a tiny dot in the field of view of your telescope’s eyepiece. But just as in the case of observing other exotic objects such as red giants and quasars, part of the thrill of tracking down these astrophysical beasties is in knowing just what it is that you’re seeing. Heck, many amateur astronomers fail to realize that any white dwarf stars are within range of their instruments and have never tracked one down.

The astrophysical nature of white dwarf stars was first uncovered in the early 20^th century. Most of the early white dwarf stars discovered were companions in binary star systems and this allowed astronomers to gauge their mass by following the orbital motion of such pairs over time. Soon, astronomers realized that they were looking at something peculiar, a new type of compact but massive stellar object that stubbornly refused to be pigeon-holed along the main sequence of the freshly conceived Hertzsprung-Russell diagram.

Today, we know that white dwarf stars are the remnants of stars which have long since passed the Red Giant stage. We say that a white dwarf is a degenerate star, and no, this not a commentary on its moral state. The Chandrasekhar limit gives us an upper limit in size for a white dwarf at about 1.4 solar masses, beyond which electron degeneracy pressure can no longer act against the inward pull of gravity. Our Sun will one day become a white dwarf, over 6 billion years from now. Think of cramming the mass of our star into the volume of the Earth and you have some idea just how dense a white dwarf is: a cubic centimetre of white dwarf weighs 250 about tons, and two cup fulls of white dwarf would weigh more than a Nimitz-class aircraft carrier.

Think of a white dwarf as a cooling ember of a star long past its hydrogen fusing prime. And white dwarfs will cool down to infrared radiating black dwarfs over trillions of years, far longer than the present 13.7 billion year age of the universe. In fact, the age of white dwarfs currently observed is one on the underpinning tenets of modern Big Bang cosmology.

All amazing stuff. In any event, here is a baker’s half dozen of white dwarf stars that you can find with a telescope tonight. A more extensive list of the nearest white dwarfs to the Earth can be found on Sol Station.

The orbit of Sirius B. Wikimedia Commons image in the Public Domain.

Sirius B: This is the nearest white dwarf to the Earth at 8.6 light years distant. Shining at magnitude +8.5, Sirius B would be a cinch to see, if only dazzling Sirius A — the brightest star in our sky at magnitude -1.5 — were not nearby. Sirius B orbits its primary once every 50 years and will reach a maximum separation of 11.5” from its primary in 2025, a prime time to cross it off of your life list in the coming decade. Blocking the primary just out of the field of view, or using an occulting bar eyepiece is key to finding Sirius B.

Sirius B was discovered by American telescope maker Alvan Graham Clark in 1862. The Dogon people of Mali also have some curious myths surrounding the star Sirius.

Constellation: Canis Major

Right Ascension: 6 Hours 45’

Declination: -16° 43’

The apparent orbit of Procyon B through 2039. Graphic created by the author.

Procyon B: Located 11.5 light years distant, Procyon B was discovered in 1896 by John Martin Schaeberle from the Lick observatory. Shining at magnitude +10.7, the chief difficultly with spotting this white dwarf, as with Sirius B, is that it has a companion about 10 magnitudes – that’s 10,000 times brighter – nearby just 4.3” away.

Constellation: Canis Minor

Right Ascension: 7 hours 39’

Declination: +5 13’

The location of GJ 440 (HIP 57367) in the southern sky. Credit: Starry Night Education Software.

-LP145-141: Also known as GJ 440, LP145-141 is one of the best southern hemisphere white dwarf stars on the list. LP145-141 is a solitary white dwarf shining at magnitude +11.5. Located 15 light years distant, LP145-141 is thought to be a member of the nearby Wolf 219 Moving Group of stars.

Constellation: Musca

Right Ascension: 11 Hours 46’

Declination: -64° 50’

The location of Van Maanen’s Star in the constellation Pisces. Credit: Stellarium

-Van Maanen’s Star: Shining at magnitude +12.4 and located 14.1 light years distant, Van Maanen’s star is the closest solitary white dwarf to Earth and the best example of a white dwarf for small telescopes. Discovered by Ariaan van Maanen in 1917, Van Maanen’s Star also has a very high proper motion of 3” per year.

Constellation: Pisces

Right Ascension: 00 Hours 49’

Declination: 05° 23’

The 40 Omicron Eridani system. Image by Author

-40 Omicron Eridani B: This is a great one to track down. The triple system of 40 Omicron Eridani b contains a fine example of a red and white dwarf orbiting a main sequence star. Located 16.5 light years distant and shining at magnitude +9.5, Omicron Eridani was the first white dwarf star discovered in 1783 by Sir William Herschel, although its true nature wasn’t deduced until 1910. Omicron Eridani B is currently 82” from its primary, an easy split.

Constellation: Eridanus

Right Ascension: 4 Hours 15’

Declination: 7° 39’

-Stein 2051: Rounding off the list and located just over 18 light years distant, Stein 2051 is another example of a red dwarf/white dwarf pair. Stein 2051 b shines at a similar brightest to Van Maanen’s star at magnitude +12.4.

Constellation: Camelopardalis

Right Ascension: 04 Hours 31’

Declination: +58° 59’

Let us know about your trials and triumphs in hunting down these fascinating objects!

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The National Aeronautics and Space Administration (NASA) is the United States government agency responsible for the civilian space program as well as aeronautics and aerospace research. President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA's predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

UFO SIGHTINGS PHOTO PHOTOGRAPHY

The Oxford English Dictionary defines a UFO as "An unidentified flying object; a 'flying saucer'." The first published book to use the word was authored by Donald E. Keyhoe. The acronym "UFO" was coined by Captain Edward J. Ruppelt, who headed Project Blue Book, then the USAF's official investigation of UFOs. He wrote, "Obviously the term 'flying saucer' is misleading when applied to objects of every conceivable shape and performance. For this reason the military prefers the more general, if less colorful, name: unidentified flying objects. UFO (pronounced Yoo-foe) for short." Other phrases that were used officially and that predate the UFO acronym include "flying flapjack", "flying disc", "unexplained flying discs", "unidentifiable object", and "flying saucer". The phrase "flying saucer" had gained widespread attention after the summer of 1947. On June 24, a civilian pilot named Kenneth Arnold reported seeing nine objects flying in formation near Mount Rainier. Arnold timed the sighting and estimated the speed of discs to be over 1,200 mph (1,931 km/h). At the time, he described the objects' shape as being somewhat disc-like or saucer-like, leading to newspaper accounts of "flying saucers" and "flying discs". In popular usage the term UFO came to be used to refer to claims of alien spacecraft. and because of the public and media ridicule associated with the topic, some investigators prefer to use such terms as unidentified aerial phenomenon (or UAP) or anomalous phenomena, as in the title of the National Aviation Reporting Center on Anomalous Phenomena (NARCAP).

UFO PHOTO PHOTOGRAPHY

UFO - Unidentified Flying Object An unidentified flying object, or UFO, in its most general definition, is any apparent anomaly in the sky that is not identifiable as a known object or phenomenon. Culturally, UFOs are associated with claims of visitation by extraterrestrial life or government-related conspiracy theories, and have become popular subjects in fiction. While UFOs are often later identified, sometimes identification may not be possible owing to the usually low quality of evidence related to UFO sightings (generally anecdotal evidence and eyewitness accounts). Stories of fantastical celestial apparitions have been told since antiquity, but the term "UFO" (or "UFOB") was officially created in 1953 by the United States Air Force (USAF) to serve as a catch-all for all such reports. In its initial definition, the USAF stated that a "UFOB" was "any airborne object which by performance, aerodynamic characteristics, or unusual features, does not conform to any presently known aircraft or missile type, or which cannot be positively identified as a familiar object." Accordingly, the term was initially restricted to that fraction of cases which remained unidentified after investigation, as the USAF was interested in potential national security reasons and/or "technical aspects" (see Air Force Regulation 200-2). During the late 1940s and through the 1950s, UFOs were often referred to popularly as "flying saucers" or "flying discs". The term UFO became more widespread during the 1950s, at first in technical literature, but later in popular use. UFOs garnered considerable interest during the Cold War, an era associated with a heightened concern for national security. Various studies have concluded that the phenomenon does not represent a threat to national security nor does it contain anything worthy of scientific pursuit (e.g., 1951 Flying Saucer Working Party, 1953 CIA Robertson Panel, USAF Project Blue Book, Condon Committee).

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Photos of Nature | Nature Photography What is The Universe

Wednesday, August 6, 2014