November 13, 2018

Astronomy Video of the Week: Chasing Barnard’s Star

Speedy Barnard’s Star. Click here for the animation.

Credit: The Virtual Telescope Project

Double wow.

When it comes to stellar motion, the pattern of constellations you see tonite will look pretty much the same on the day that you die as they appeared on the day you were born. Sure, we’re all whizzing around the core of the Milky Way Galaxy with our stellar neighbors, but the distances between the stars is so vast, that this motion (known as apparent or proper motion) is tiny from year to year. [Read more...]

AstroEvent: The Passage of 61 Cygni.

To the naked eye observer, the positions of the stars will appear pretty much the same on the day you die as the day you were born; stellar motion doesn’t add up to much over the span of a human lifetime. This week, however, we’ll look at an interesting configuration that just might show some changes through the telescope over the coming years; 61 Cygni. No less an authority than Burnham’s Celestial Handbook lists 61 Cygni as “historically one of the most interesting objects in the heavens.” A good double star for small telescopes, 61 Cygni lies within a few degrees of the bright star Deneb and is currently placed high in the west for northern hemisphere observers immediately after sunset.  Sometimes known as Bessel’s Star or Piazzi’s Flying Star, 61 Cygni attracted the attention of astronomers around 1800 after Giuseppe Piazzi noted a large proper motion for the pair of 5.22” per year towards a direction of position angle 52°. This is extremely fast, currently the seventh fastest known. The pair itself is just above the naked eye visibility threshold at about +5.2 magnitude, and are currently separated by 30+ arc seconds in its 653 year orbit. In fact, the pair of orange-hued stars will reach maximum apparent separation around 2100 A.D., and thus will continue to separate throughout our lifetimes. An interesting fact about the pair came to our attention via a letter published in the November 2010 Sky & Telescope magazine submitted by Richard Stanton of Three Rivers, California: Component A of the pair is currently “flying by” a distant 11th magnitude background star, and tracking its motion over the next few years could provide an interesting challenge. The constellation Cygnus is well placed in the summer months, but you can start acquainting yourself with the pair tonight. The coordinates of the pair are;

Right Ascension: 21h 06m 54s

Declination: +38° 44’ 45”

The background star should currently be approaching a position angle of 26° and a separation of 5” the summer of 2011 and will be at its closest apparent approach on the following year at a separation of less than 3”. Sketching or tracking the pair would be an interesting exercise in observing proper motion… an even more intriguing feat would be to construct a stop motion animation of the motion of the pair. Do give 61 Cygni a look over the next few years, and marvel at the slow change of movement in the heavens!

The astroword for this week is: Proper Motion. This is the apparent shift of stars against the background as seen from our particular vantage point in space. As we wheel about the core of our galaxy, nearby stars appear to slowly shift in position due to their differing relative motion. The measured proper motion is cumulative between the observed stars’ true radial motion and that of our own solar system; generally, the higher the proper motion, the nearer the star is to us. Think of observing a flock of birds passing by; the birds closer will appear to move faster. It was this fact that brought 61 Cygni to the attention of astronomers in the early 19th century; it wound up on a short list of target stars due to its large proper motion, as it was suspected to be nearby in the galactic hood. It achieved historical notoriety in 1838, when Friedrich Wilhelm Bessel successfully measured its stellar parallax at a tiny 0.29” (this was over the span of six months!) giving 61 Cygni a distance of 10.3 light years, close to the accepted value of 11.4. 61 Cygni was the first star to have its stellar parallax measured, and is now known to be the 14th nearest star system from our own Sun. As you look at the tiny pair this holiday season, remember its place in astronomical history and the role it played in discovering that the universe was indeed a vast place!

 

16.05.10- Gliese 710: A Future Stellar Threat?

Our quiet corner of the local galaxy may be in for a future interloper. A possible solar system side-swipe comes in the form of Gliese 710, an unassuming +10 magnitude orange dwarf star currently 63 light years distant in the constellation Serpens. As we swirl around the center of our galaxy, stellar neighbors come and go like in-laws during your favorite respective obligatory familial holiday season. The low proper motion of this star hid its true nature until about a decade ago; generally, the lower the apparent motion, the more distant the star. Gliese 710, however, fits into a different class; a star that shows a low apparent motion because it’s moving towards us. Closest approach has been calculated by astronomer Joan Garcia-Sanchez of JPL as about 1.3 light years in 1.5 million years time. Doesn’t sound like much? Well, this skirts the edge of our Oort Cloud, that vast reservoir of comets that extends out to about 1.6 light years distant…Gliese 710 stands an 86% chance of breaking this threshold. In addition, a 2007 review of Hipparcos data by Vadim V. Bobylev shows that this star may pass as close as 0.02 of a light year, about 50 times farther than the (sometimes) planet Pluto. This could make things really interesting, as Gliese 710 could really stir things up in our Oort cloud. And of course, there is the question of whether or not Gliese 710 has an Oort Cloud of its own. More than likely, this pulse of comets will last for about a several million year span of time. Could our inner solar system have sustained such shocks before? One only has to look at the crater-scarred surface of our Moon to realize the inner solar system has served as a shooting gallery over the eons. The statistical probability of a really (i.e. 1,000 AU) approach is about 1 in 10,000, so don’t max out those credit cards just yet… this uncertainly stems from incomplete knowledge of all the gravitational factors at work. As more sensitive astrometrical platforms, such as ESA’s Gaia spacecraft come online, the nature of the threat from Gliese 710 will be more precisely known. At its closest approach, this inbound star will be about as bright as the red giant star Antares… here’s to the neighbors!

Event: Mars passes the Beehive.

This week offers a two-fer, an easy to spot naked eye conjunction of two very different objects and a difficult to observe occultation. 1st up is a close pairing of the planet Mars and M44, the Beehive Cluster. From the 13th of April until the 20th, both will be grouped in a visual circle less than 2° arc degrees in diameter, an easy target for both camera lens or binocs. Mars will be at closest apparent approach on the evening of the 16th. Both ride high near the zenith in the dusk skies for northern hemisphere viewers, making for an easy photo op. Of course, Mars is a scant 3 odd light minutes away; M44 is at an estimated distance of 577 light years. Also known as Praesepe, the Manger, this cluster in the heart of the constellation Cancer has been known since ancient times. Proper motion studies suggest that this open cluster may share its origins with the V-shaped Hyades in the constellation Taurus; about 1010 members of this group have been identified, including 11 white dwarfs.

Up for a challenge? On the evening of the 15th, the 3 day old crescent Moon will occult the close spectroscopic binary star Mu (µ) Arietis.  The action occurs around 3:00 UT (on the 16th) and favors viewers on the North American west coast. Unfortunately, the event does not occur under the most favorable circumstances; the Moon will be a thin crescent, the star is +6 magnitude, and the entire event will be low in the dusk skies. Still, we’d love to hear from anyone who successfully witnessed this difficult to observe event!

The astro-word for the week is Messier Object. Back in 1771, French astronomer Charles Messier got tired of misidentifying faint little fuzzies he came across in the night sky in his quest for comets and decided to compose a catalog of these objects. The original published list contained 45 objects and Messier later expanded it to 103. The current tally stands at 110, although the list contains a few dubious entries. The catalog was the first list of deep sky objects, and has since spurred countless “Messier Marathons” common in spring. Morphologically, the catalog contains open & globular clusters, planetary nebulae, emission nebulae and galaxies. Of course, Messier had no inkling what these objects truly were when he cataloged them. It’s somewhat odd that such un-comet like objects as M44 and the Pleiades made this list, but say, the Double Cluster on the Perseus-Cassiopeia border did not. And of course, there was a whole menagerie southern sky objects yet to be categorized. That would have to wait for the Herschel dynasty of astronomers, and their expanded New General Catalog!

Searching for Robert Burnham.

Sometimes, the quietest minds among us also have the most to share with the world.

Last month, on a warm summer’s day in August, the East Valley Astronomy Club, in connection with the Robert Burnham Jr. Memorial Fund, honored a man with the dedication of a small plaque placed on the Pluto walk at the Lowell Observatory. That man is probably the most unknown, but influential amateur astronomer of the 20th century; Robert Burnham Jr. a man that but for a singular colossal work, might have passed on into total obscurity. The book is Burnham’s Celestial Handbook, a three volume guide to the wonders of the night sky. [Read more...]