Vega and the Constellation Lyra – 2015-10-30

The bright star Vega at magnitude 0.03 is the 5th brightest star in the sky and the third brightest star visible from the 45th parallel (Ottawa). Sirius at magnitude -1.46 is the brightest star in the sky and Arcturus magnitude -0.05 is the second brightest in the north. Although the yellow-orange star Arcturus is only marginally brighter than Vega, Vega has the advantage of being near the zenith on summer nights and the slight blue tint makes it seem even brighter.

Vega Closeup - 2015-10-30

Vega Closeup – 2015-10-30

Vega is in the constellation Lyra – the lyre or harp. Lyra is one of 48 constellations listed by Ptolemy in the second century and is on the International Astronomical Union’s (IAU) official list of 88 constellations. The long exposure image below shows the 4 bright stars of the harp as well as Epsilon Lyra (ε1, ε2 – the Double Double) left of Vega and Kappa Lyra (κ) to the right.

Vega in the Constellation Lyra - 2015-10-30

Vega in the Constellation Lyra – 2015-10-30

The chart overlay below  shows the location of the bright stars as well as the location of the M57 Ring Nebula. Vega is 25ly from earth while the other stars are at various distances. So the lyre shape is just a chance alignment when viewed from earth.

  • Vega: mag 0.03, dist 25ly
  • Epsilon 1: mag 4.65, dist 162 ly
  • Epsilon 2: mag 4.56, dist 161ly
  • Kappa: mag 4.31, dist 238ly
  • Zeta: mag 4.31, dist 154ly
  • Delta: mag 4.21, 906ly
  • Sheliak: mag 3.50, 882ly
  • Sulafat: mag 3.25, 640ly
Lyra Constellation Stick Figure

Lyra Constellation Stick Figure

The next image is modified to reduce the fainter stars and is more representative of what the sky might look like from a dark site. With this image, the bright stars of the constellation Lyra are more obvious.

Vega in the constellation Lyra - Less Stars -2015-10-30

Vega in the constellation Lyra – Less Stars -2015-10-30

While we think of constellations as the stick figure above or the elaborate drawings of mythical figures, the IAU defines a constellation as a non-overlapping region. So Lyra extends a little past the obvious 7 bright stars and defines a region in the sky between Cygnus to the east and Hercules to the west.

Lyra Constellation Boundaries

Lyra Constellation Boundaries

Lyra is home to a few interesting night sky objects:

Within the “stick figure” there are:

  • Epsilon – the double double
  • Messier 57 – The Ring Nebula
  • Zeta, Delta and Sulafat are doubles

Within the boundaries there are also:

  • M56 – an 8.3 magnitude globular cluster with an apparent size of 5arc-minutes
  • NGC 6791 – an 9th magnitude open cluster spanning 19′

The pair of stars Epsilon Lyra 1 and 2 (ε1, ε2)  are gravitationally bound to each other – meaning they are in the same region and rotate around each other (although in thousands of years). Each of ε1, ε2 is also a pair of stars that can be seen as doubles though a medium to large telescope. ε1, ε2 have a separation of 3.5′ which can be seen in binoculars. The doubles of ε1, ε2 each have separations of 1.3″ and 2.3″ making them challenging doubles to split in a 4″ scope. However, the two pairs are oriented 90° with respect to each other making it easy to compare the star shapes and aiding in detecting the separation. The periods of each pair are in the range of 600 to 1200 years. The finder chart below helps when trying to “split” the doubles.Finder_Chart_Epsilon-Lyra

The image below of the double-double doesn’t quite manage to show a gap between the close pairs. This is what might be typically seen in a smaller scope or a night of poor seeing. Still, by noticing that each pair is actually oval shape, the direction at least of the doubles gives a clue that they are doubles.

DoubleDouble_Epsilon_Lyra_2008-06-10_v1_SJM

Messier 57 (NGC6720) – the Ring Nebula is a large bright planetary nebula. Its visual magnitude is 9.5 and 3 arc-min across. On good nights and a large telescope, the remnants of the central star that exploded is visible. The ring is the expanding cloud of hot gas thrown off when the star shed its outer shell. The image below easily captures this detail as well as the colour which is not discernible through the eyepiece.

M57 - Ring_Nebula - 2011-07-30 - v2

M57 – Ring_Nebula – 2011-07-30 – v2

Vega rises during the late evening in April. It will be low in the north-east at about 9:30pm edt mid-April and makes its way across the sky during the night. By midnight it’s still in the north-east and only 25° above the horizon. It doesn’t transit (crosses due south) until 6am though!

Of course, if one is willing go out at much later times, Vega is also visible in the winter but after midnight. I tend think in terms of what objects are visible during normal evening hours.

Lyra Finder Chart - Sky facing East on 2015-04-15 at 21:30hrs EDT

Lyra Finder Chart – Sky facing East on 2015-04-15 at 21:30hrs EDT

Each month Vega rises two hours earlier. Which means it transits two hours earlier each month. By late summer at 9:30pm edt, Vega is due south and high in the sky near the zenith. The chart below shows Vega and Lyra high in the sky due south nestled between Pegasus and Hercules.

Lyra Finder Chart - Sky facing South on 2015-09-01 at 21-30hrs EDT

Lyra Finder Chart – Sky facing South on 2015-09-01 at 21-30hrs EDT

By December, Vega is low in the west in the evening and soon will disappear altogether from the evening sky.

Lyra Finder Chart - Sky facing East on 2015-04-15 at 21:30hrs EDT

Lyra Finder Chart – Sky facing East on 2015-04-15 at 21:30hrs EDTj

But … as said earlier, if one wanted to go out at other times, Vega can still be seen during winter. Starting in December, Vega is also visible in the early morning sky! The chart below shows Vega rising at 6:30 am (when it’s still dark in Ottawa) the day after it set in the west on the evening before.

Lyra Finder Chart - Sky facing East on 2015-12-16 at 06-30hrs EST

Lyra Finder Chart – Sky facing East on 2015-12-16 at 06-30hrs EST

Each month Vega will rise 2hrs earlier. So in January it rises at 4:30am and in February it rises at 2:30. By April it will be rising at 9:30 again.

So Vega is actual visible all year long, but to see it might mean going outside to look for it while sleeping is a better alternative.