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07/10/2017 – Ephemeris – Deneb, a super bright star

July 10, 2017 1 comment

Ephemeris for Monday, July 10th. Today the Sun will be up for 15 hours and 20 minutes, setting at 9:27, and it will rise tomorrow at 6:08. The Moon, 1 day past full, will rise at 10:24 this evening.

This evening when it gets dark the bright star Deneb in Cygnus the swan will be high in the east-northeast. Deneb is the dimmest star of the summer triangle. Of the other stars of the triangle, Vega is higher in the east, while Altair is lower in the southeast. While Deneb’s apparent magnitude, or brightness as seen from Earth, makes it the dimmest of the three bright stars, Deneb’s vast distance of possibly 1,400 light years* makes it over 50 times the distance of Vega. If brought as close as Vega, Deneb would be as bright at least as the quarter moon. It is possibly as bright as 200 thousand Suns; and a huge star, possibly as large in diameter as the orbit of the Earth. For all this it is only 20 to 25 times the mass of the sun.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

* Deneb’s distance is not well known.  Over the years with the Ephemeris program and this blog I’ve given various distances to the star.  Having no companion and being beyond the distance where trigonometric parallax is used, at least from the ground, makes distance measurement difficult.  Hipparcos  satellite measurements give a distance about twice as great.  Estimates of the true brightness of a star are based on its known distance.  An error in distance by a factor of two gives an error in terms of intrinsic luminosity by a factor of 4, due to the inverse square law of brightness with distance.

Addendum

The constellations Lyra, Cygnus and Aquila

Deneb with the other stars and constellations in the Summer Triangle. Created using Stellarium.

Deneb & North American Nebula

One of my old photographs of Deneb and the North American Nebula digitized from a slide. Deneb’s ultraviolet emissions cause the North American and unnamed here Pelican Nebulae to glow.  The red color is due to hydrogen.

07/18/2014 – Ephemeris – Deneb is the brightest star of the Summer Triangle… Really

July 18, 2014 Comments off

Ephemeris for Friday, July 18th.  Today the sun will be up for 15 hours and 8 minutes, setting at 9:22.   The moon, at last quarter today, will rise at 12:58 tomorrow morning.  Tomorrow the sun will rise at 6:15.

At 11 this evening the bright star Deneb in Cygnus the swan will be moderately high in the east northeast.  Deneb is the dimmest star of the summer triangle.  Of the other stars of the triangle, Vega is nearly overhead, and Altair to the southeast.  While Deneb’s apparent magnitude, or brightness as seen from Earth, makes it the dimmest of the three bright stars, Deneb has a vast distance of possibly 1,550  light years.  If brought as close as Vega, Deneb would be several times brighter than Venus.  For all this it is only 13-20 times the mass of the sun.  It will have an extremely short life and will explode, go supernova, in perhaps a few million years.  Closer to home, check out the Sun at Kingsley Heritage Days This Saturday and Sunday.

Times are for the Traverse City/Interlochen area of Michigan.  They may be different for your location.

Addendum

Northern Cross

Deneb and the Northern Cross section of Cygnus the swan. Created using Stellarium.

Deneb & North American Nebula

One of my old photographs of Deneb and the North American Nebula digitized from a slide.

The North American Nebula, visible as a faint smudge in binoculars or the naked eye may be ionized and illuminated by Deneb.  It’s distance appears to be comparable to that of Deneb.

You may note that previous postings about Deneb over the years have given different distances of Deneb.  That just denotes how difficult it is to pin down its distance.

10/11/2012 – Ephemeris – North American Nebula

October 11, 2012 Comments off

Ephemeris for Thursday, October 11th.  The sun will rise at 7:53.  It’ll be up for 11 hours and 10 minutes, setting at 7:04.   The moon, 3 days past last quarter, will rise at 4:30 tomorrow morning.

Most of what we see in the Milky Way are just masses of stars, but there are bright  clouds of gas , or to name them properly:  emission nebulae.  These bright clouds are areas of star formation.  It is the ultraviolet light from young massive stars that light up the clouds they were formed from.  A bright one, easily visible in binoculars is just about overhead at 9 p.m. Called the North American Nebula, a glow shaped much like our continent just east of the star Deneb, the northernmost star of the Summer Triangle, and brightest star in Cygnus the swan or Northern Cross.  There are many other nebulae in the Milky Way, visible in binoculars and small telescopes.  Many enjoyable hours can be spent sweeping the Milky Way for nebulae and star clusters.

Times are for the Traverse City/Interlochen area of Michigan.  They may be different for your location.

Addendum

North American Nebula in Red.  My old image.

North American Nebula in Red. My old image.

The red object is the North American Nebula.  Our eyes cannot perceive the color, due to hydrogen.  This was a time exposure on film without telephoto.  The bright star to the upper right is Deneb.  The orientation is approximately correct if facing south.  The photo also shows the stars that make up the glow of the Milky Way to the unaided eye.

Deneb Overhead.  Created using Stellarium.

Deneb Overhead at 9 p.m. on October 11. Created using Stellarium.

The North American Nebula is about the size and position of the C in Cygnus.

Better view of the North American Nebula taken by Scott Anttila.

Better view of the North American Nebula taken by Scott Anttila.

This nebula is cataloged as NGC 7000.