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Posts Tagged ‘Cepheid Variable Stars’

09/07/2021 – Ephemeris – The constellation of Cepheus the king

September 7, 2021 Comments off

This is Bob Moler with Ephemeris for Tuesday, September 7th. Today the Sun will be up for 12 hours and 55 minutes, setting at 8:07, and it will rise tomorrow at 7:13. The Moon, 1 day past new, will set at 8:53 this evening.

There’s a faint constellation in the northeast above the W shaped constellation of Cassiopeia. It’s a nearly upside down church steeple of a constellation called Cepheus the king, and husband of queen Cassiopeia. Cepheus’ claim to modern astronomical fame is that one of its stars, Delta (δ) Cephei, is the archetype for the important Cepheid variable stars. Delta is the bottom most of a trio of stars at the right corner of the constellation. In the early 20th century, Henrietta Leavitt discovered that Cepheids in the nearby galaxy the Large Magellanic Cloud varied in brightness with a period that was related to their average brightness. This meant that Cepheids could be used as standard candles to measure the great distances to other galaxies.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hr). They may be different for your location.

Addendum

Cassiopeia and Cepheus finder animation

Cassiopeia and Cepheus finder animation looking in the northeast at 9-10 pm or about an hour after sunset. Created using Stellarium and GIMP.

Delta Cephei finder for September at 9-10 pm, looking northeast. Created using Cartes du Ciel (Sky Chart).

Delta_Cephei_lightcurve

Light Curve of Delta Cephei. The pulsation period is 5.367 days. Note the Magnitude vertical axis, the lower the magnitude the brighter the star is. Blame that on the Greek astronomer Hipparchus, 2nd century BC. It’s like golf scores, the lower the score, the better the golfer. Credit: Thomas K Vbg – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=13887639.

09/18/2020 – Ephemeris – A closer look at Cepheus the king’s most famous star

September 18, 2020 Comments off

This is Ephemeris for Friday, September 18th. Today the Sun will be up for 12 hours and 20 minutes, setting at 7:46, and it will rise tomorrow at 7:27. The Moon, 1 day past new, will set at 8:52 this evening.

There’s a faint constellation in the northeast above the W shaped constellation of Cassiopeia. It’s a nearly upside down church steeple of a constellation called Cepheus the king, and husband of queen Cassiopeia. Cepheus’ claim to astronomical fame is that one of its stars, Delta (δ) Cephei, is the archetype for the important Cepheid variable stars. Delta is the bottom most of a trio of stars at the right corner of the constellation. In the early 20th century Henrietta Leavitt discovered that Cepheids in the nearby galaxy the Large Magellanic Cloud varied in brightness with a period that was related to their average brightness. This meant that Cepheids could be used as standard candles to measure the great distances to other galaxies.

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

Addendum

Cassiopeia and Cepheus finder animation

Cassiopeia and Cepheus finder animation looking in the northeast at 9 pm or about an hour after sunset in mid-September. Created using Stellarium and GIMP.

Delta Cephei (circled) finder for mid-September at 9 pm or about an hour after sunset looking northeast. The brighter stars are marked by their Bayer Greek letters. Numerical designations are Flamsteed numbers. Created using Cartes du Ciel (Sky Chart).

Delta_Cephei_lightcurve

Light Curve of Delta Cephei. The pulsation period is 5.367 days. Credit: ThomasK Vbg – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=13887639

1122/2016 – Cepheus the king and its one really important star

November 22, 2016 Comments off

Ephemeris for Tuesday, November 22nd.  The Sun will rise at 7:49.  It’ll be up for 9 hours and 18 minutes, setting at 5:08.  The Moon, 1 day past last quarter, will rise at 1:56 tomorrow morning.  |  There’s a faint constellation in the north above Polaris.  It’s a nearly upside down church steeple of a constellation called Cepheus the king, and husband of queen Cassiopeia the W shaped constellation right of it.  Cepheus’ claim to astronomical fame is that one of its stars, Delta (δ) Cephei, is the archetype for the important Cepheid variable stars.  Delta is in a trio of stars at the top corner of the constellation, and the one on the right.  In the early 20th century Henrietta Leavitt discovered that Cepheids in the nearby galaxy the Large Magellanic Cloud varied in brightness with a period that was related to their average brightness.  This meant that Cepheids could be used as standard candles to measure great distances to other galaxies.

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

Addendum

Cepheus

Cepheus animated finder chart for 8 p.m. November 22, 2016. Created using Stellarium and GIMP.

Delta Cephei finder chart

Delta Cephei finder chart. This is the same orientation as the chart above, but created using Cartes du Ciel (Sky Charts). A green line points to Delta (δ) Cephei.

A word about star designations in the chart above.  In general only the brightest stars have proper names.  And those usually come from antiquity, and most of those are Arabic.  Star designations which are Greek lower case letters come from Johann Bayer’s Uranometria star atlas from 1603.  He designated the stars by order of brightness.  In constellations with a lot of stars he moved to the Latin alphabet after running out of Greek letters.  These were, of course, naked eye stars; the atlas being produced a few years before the invention of the telescope.  Stars with numbers are Flamsteed designations from John Flamsteed’s 1725 star catalog.  He numbered his stars from west to east in a particular constellation, but only those stars that could be seen from Great Britain.  A single star can have many catalog designations.  For instance the bright star Vega in Lyra the harp is Alpha (α) Lyrae, Bayer designation; 3 Lyrae, Flamsteed designation; HD 172167, Henry Draper catalog; BD +38 3238,  Bonner Durchmusterung, a German catalog; HIP 91262, Hipparcos catalog, and so on.