Tag Archives: Variable Star

NASA Night Sky Notes: Summer Triangle Corner – Vega

Poster’s Note: One of the many under-appreciated aspects of NASA is the extent to which it publishes quality science content for children and Ph.D.’s alike. Your tax dollars help promote science! The following article was provided for reprinting by the Night Sky Network in June, 2020.

By David Prosper and Vivian White

If you live in the Northern Hemisphere and look up during June evenings, you’ll see the brilliant star Vega shining overhead. Did you know that Vega is one of the most studied stars in our skies? As one of the brightest summer stars, Vega has fascinated astronomers for thousands of years.

Vega is the brightest star in the small Greek constellation of Lyra, the harp. It’s also one of the three points of the large “Summer Triangle” asterism, making Vega one of the easiest stars to find for novice stargazers. Ancient humans from 14,000 years ago likely knew Vega for another reason: it was the Earth’s northern pole star! Compare Vega’s current position with that of the current north star, Polaris, and you can see how much the direction of Earth’s axis changes over thousands of years. This slow movement of axial rotation is called precession, and in 12,000 years Vega will return to the northern pole star position. Bright Vega has been observed closely since the beginning of modern astronomy and even helped to set the standard for the current magnitude scale used to categorize the brightness of stars. Polaris and Vega have something else in common, besides being once and future pole stars: their brightness varies over time, making them variable stars. Variable stars’ light can change for many different reasons. Dust, smaller stars, or even planets may block the light we see from the star. Or the star itself might be unstable with active sunspots, expansions, or eruptions changing its brightness. Most stars are so far away that we only record the change in light, and can’t see their surface.

NASA’s TESS satellite has ultra-sensitive light sensors primed to look for the tiny dimming of starlight caused by transits of extrasolar planets. Their sensitivity also allowed TESS to observe much smaller pulsations in a certain type of variable star’s light than previously observed. These observations of Delta Scuti variable stars will help astronomers model their complex interiors and make sense of their distinct, seemingly chaotic, pulsations. This is a major contribution towards the field of astroseismology: the study of stellar interiors via observations of how sound waves “sing” as they travel through stars. The findings may help settle the debate over what kind of variable star Vega is. Find more details on this research, including a sonification demo that lets you “hear” the heartbeat of one of these stars, at: bit.ly/DeltaScutiTESS

Interested in learning more about variable stars? Want to observe their changing brightness? Check out the website for the American Association of Variable Star Observers (AAVSO) at aavso.org. You can also find the latest news about Vega and other fascinating stars at nasa.gov.

Vega possesses two debris fields, similar to our own solar system’s asteroid and Kuiper belts. Astronomers continue to hunt for planets orbiting Vega, but as of May 2020 none have been confirmed. More info: bit.ly/VegaSystem Credit: NASA/JPL-Caltech
Can you spot Vega? You may need to look straight up to find it, especially if observing after midnight.

The Night Sky Network program supports astronomy clubs across the USA dedicated to astronomy outreach. Visit nightsky.jpl.nasa.gov to find local clubs, events, and more!

An Update On Nova Del 2013 (PNVJ20233073+2046041) – Dimmer Views And A Distance Estimate

Greetings fellow astrophiles!

While the Night Sky is always inspiring, it is quite… constant. The positions of objects within our own Solar System change with respect to the background of stars, weather patterns on Jupiter and Saturn can produce a bit of variety for backyard telescopes, Iridium flares and other satellites produce some nice bursts of reflected sunlight, the Sun can prove to be a many-varied treat to afternoon solar watchers, and the most astute observers can pick out the differences in brightness of variable stars. That said, much of the rest of the Night Sky only changes due to the rotation of the Earth about its axis and the revolution of the Earth around the Sun (within the lifetimes of most observers, that is).

Significant changes to stars, nebulae, and galaxies can take decades, lifetimes, or eons, meaning even many observers take in the same deep sky views throughout their entire lives. The recent nova in Delphinus was then noteworthy as something that (1) changed dramatically over the course of days and (2) occurred within our own Milky Way galaxy. CNYO members held their first Scope Mob at Jamesville Beach to take in a prime view of the nova from just outside Syracuse, finding a quite reasonable spot for future sessions at the same time.


“Animation of Possible Nova in Del by E. Guido & N. Howes,”
taken from s176.photobucket.com/…/gif_1531x1459_2db958_zps3f68f105.gif.html

With several excellent websites providing great detail on the nova itself (I specifically direct you to universetoday.com, space.com, and AstroBob’s article (link HERE), which I count as the most thorough article written on the event), a group of astronomers have provided an official measurement of the distance to Nova Del 2013, posted to Astronomers Telegram on 23 August. In their report, they determine that the nova is 4.2 kiloparsecs (I refer you to the wikipedia article on the parsec for more info), or about 13,700 light years, away. As our own galaxy is about 100,000 light years across and we’re about 25,000 light years from the center, this puts the nova in our own celestial neighborhood. That said, this means the nova itself occurred near the end of Beringia, the land at the bottom of the Bering Strait, after the last great ice retreat but before the flooding that separated Asia from America (so it’s been a while, but an eye blink in celestial terms).

A snippet of the abstract that includes the reported distance estimate is reproduced below from the original post, which can be found at: www.astronomerstelegram.org/?read=5313

Distance of nova Del 2013 from MMRD relations

ATel #5313; M. M.M. Santangelo, M. Pasquini, S. Gambogi, G. Cavalletti (OAC – Osservatorio Astronomico di Capannori and IRF – Istituto Ricerche Fotometriche, Italy)
on 23 Aug 2013; 15:56 UT
Credential Certification: Filippo Mannucci (filippo@arcetri.astro.it)

Subjects: Optical, Nova

… So the distance of the nova is d ~ 4.2 +/- 0.4 kpc Using the linear Mv-log(t2) relation of Downes & Duerbeck (2000, AJ 120, p.2007) a t2 = 8.5 implies an absolute magnitude of Mv ~ -8.9 +/- 0.2. So, ceteris paribus, the distance changes to d ~ 3.5 +/- 0.4 kpc. As a final preliminary estimate, we can adopt a value around 4 kpc (or a bit less) for the distance of the nova DEL 2013.