September 30, 2014

AstroChallenge: The Sub-Giants of Delta Serpentis.

You might’ve noticed that we here at Astroguyz have a “thing” for double stars. This can be a controversial affliction among deep-sky observers, as many an astro-imager sees mere “stars” as boring compared to their quest for faint nebulae and galaxies. But for many an observer trapped in the ‘burbs, double stars offer a deep sky target that still holds up well under light polluted skies when those +14th magnitude galaxies just don’t stand a chance of ever shining through. This week, we look at the fascinating system of Delta Serpentis.  This yellow white pair is 210 light years distant in the constellation Serpens Caput (The Head of the Serpent). A complex system, the bright pair has 4.1” arc seconds of separation & magnitudes +4.2 (Component A) and +5.2 (Component B), respectively. Position angle of the A-B pairing is 178°. Also, sharp-eyed viewers may be able to catch another associated pair 66” distant at position angle 14°, with 14th and 15th magnitude components with a 4.4” arc second spread.  The A and B components are both F-type sub-giants off of the main sequence shining at 76 and 31 times the luminosity of our own Sun. The primary pair is embraced in a 3200 year orbit, while the distant has an unknown period.

Delta Serpentis: A finder chart. (Created by the Author in Starry Night).

The position for the system is as follows;

Right Ascension: 15 Hours 34.8’

Declination:  +10° 32’

The pair is well positioned to the west after sunset for the next month…good luck, and let us know of your triumphs and tales of hunting down double-star prey!

The Astro-Word of the Week is Delta Scuti Variable. Also sometimes referred to as a Dwarf Cepheid variable stars, this is a rare form of variable of which the A component of Delta Serpentis is a “card carrying” member. Hey, you knew something was special about the pair, right?  Lesser known than traditional Cepheids, these smaller F-type stars also have a period-luminosity relationship and also serve a crucial standard candles. Credit for discovery of the variability of the prototype Delta Scuti goes to a paper written by W. W. Campbell and W.H. Wright in 1900. Drawings depict Delta Scuti as far back as Flamsteed’s 1781 southern sky star catalog.  These stars occupy a remarkable branch of the Hertzsprung-Russell diagram; a metal poor branch of instability near the center of the traditional “lazy-S” curve. Most of these stars are between 1 and 2.5 solar masses and have a very short range of variability of 0.03 to 0.3 days.   Why study Delta Scuti variables? Well, astrophysical modeling on these stars has proven crucial to the emerging field of astro-seismology. Delta Scuti-style variables can be further divided into high amplitude and low amplitude variables. This fast variability characteristic coupled with an asymmetric non-radial pulsation enables astronomers to map and model “star-quakes” within the interior of Delta Scuti type stars much the same as helioseismologists study acoustic waves resonating through our own Sun.  Backyard observers have also gotten into the act, and some suspected Delta Scuti type variables awaiting validation include V703 Scorpii, YZ Bootis, and CY Aquarii. These swiftly evolving F-type stars do not reside in the instability region of the H-R diagram for long relative to their lifetimes, a prime reason that this particular class of variable stars is comparatively rare in the sky. It’s amazing that we can glean so much information from a few photons of light!

 

Variable Star Observing 101.

An artist’s conception of an accreting binary system. (Credit: NASA).

Bored and looking for something new to do in astronomy? Tired of hauling out that imaging rig you took out a 2nd mortgage for just to see “how M31 looks in my 10-inch SCT tonight?” Let me introduce you to the fun field of variable star observing, an exciting endeavor that you can actually contribute some real science to. But first, a little history; [Read more...]

15.04.11: T Pyxidis in Outburst!

The field of T Pyx with 1 deg & 5 deg FOV…(Created by Author in Starry Night).

We interrupt this week’s regularly scheduled book review (which will run tomorrow) to bring notice to a recent celestial goings on. Early Thursday morning, AAVSO alert notice #436 graced our inbox; recurrent nova T Pyxidis is currently in outburst. [Read more...]

19.02.11: V1647 Orionis-A Request for Observations.

The region of M78 (Arrowed). (Credit: Clay M. Davis).

This past Tuesday, a call for observations went out from the American Association for Variable Star Observers (AAVSO) for observations past and present of a very poorly understood variable. In AAVSO Special Notice #235 Dr. Colin Aspin of the University of Hawaii has requested images past and present of the area surrounding M78 and the object known as McNeil’s Nebula. [Read more...]

22.01.11: A Quasar Campaign.

  Field for 3C 273. (Credit: Marcus Hauser Landessternwarte Heidelberg-Koenigstuhl)

   A call recently went out from the American Association of Variable Star Observers (AAVSO) that we thought was worth passing along. Specifically, Alert Notice 430 is calling for well-equipped and skilled observers to monitor to two exotic objects: Blazar-type quasars 3C 273 and 3C 279. If 3C 273 is sounding familiar, that’s because it was one of our astronomy challenges last year; at around magnitude +12.7, 3C 273 was the first quasar identified as such and is one of the brightest quasars in the sky. [Read more...]

17.01.11: Tracking Vestoids.

Vesta: Hubble’s best…(Credit: NASA/JPL/ESA/Space Telescope Institute).

The American Association of Variable Star Observers & NASA wants YOU to assist them with the up and coming Dawn mission. Specifically, scientists are looking to characterize “Vestoids,” or Vesta-like asteroids in preparation for Dawn’s exploration of the real thing in July of this year. To this end, the AAVSO has selected three targets for amateurs to observe; 1981 Midas (1973 EA), 4688 (1980 WF) and 137052 (1998 VO33). These Near Earth Objects (NEOs) are all thought to be very similar to the asteroid Vesta, and brightness estimates may constrain sizes and compositions. [Read more...]

24.02.10: A Robotic Telescope Raffle!

A robotic telescope; yours to play with before bedtime? (Credit: AAVSO).

A robotic telescope; yours to play with before bedtime? (Credit: AAVSO).

   Ever wish you could have your very own robotic telescope based at a world class dark sky site to utilize on those murky winter nights? Well, the American Association of Variable Star Observers (AAVSO) is having a raffle next month to award a winner a years’ free access to their recently established AAVSONet, a network of 5 robotic telescopes in New Mexico. [Read more...]

U Scorpii is Currently in Outburst.

A generated 15 degree field for u Scoprii. (Credit: AAVSO).

A generated 15 degree field for u Scoprii. (Credit: AAVSO).

This is a quick shout out for all variable star watchers to catch a rare object; recurrent nova U Scorpii is currently in outburst. Followers of this space will recall that we blogged about this flare star last September; the AASVO issued Alert Notice 415 earlier today stating that U Sco is currently at +8 magnitude and climbing. Scorpius is currently placed low in the south east in the hours before dawn, and U Sco should be a binocular object. This is a fast one, so be sure to try and catch it over this next few mornings, as after this weekend it will have propably faded out, and we will also have a past Full Moon to contend with… good luck!

AstroEvent of the Week: 27.04.09: Epsilon Aurigae.

Epsilon Aurigae.

Epsilon Aurigae. (Credit: Stellarium).

The American Association of Variable Star Observers wants you to help gather data on a very enigmatic astronomical object; the variable star Epsilon Aurigae. This seemingly ordinary star varies in a very peculiar way. The primary is a type F0 super-giant star, and what is known is that every 27.06 years an unseen mass dims its light from its usual +3.0 magnitude to about +3.8 for about a year. [Read more...]

AstroEvent of the Week: January 19th-25th, 2009: Will EE Cephei Fade?

EE Cep.



Light Curve models of EE Cephei during the 2003 event. (Credit: Simostronomy).

Variable star observing stands as a key area that amateur astronomers can still make a significant contribution. Either via imaging or visual observation, its fun to know that you are doing some of the grunt work of science and not just taking pretty pictures. This week’s event will require a telescope of at least 4″ aperture; it’s a rare dimming of the eclipsing variable EE Cephei. [Read more...]