Follow the Arc to Spica and Venus

   During the hour or so before the Sun rises, the inner planet Venus will shine brightly over the eastern horizon. Over the next several days Venus will be in a close conjunction with the blue-white star Spica in the constellation Virgo the Harvest Maiden. Venus will pass within 1-2o from Spica. Venus is unmistakable with an apparent magnitude of -4.7, and for comparison Spica has an apparent magnitude of 0.98, which is bright but not bright like Venus!

   The animated graphic shows the sky at 6 am CST from November 12th to November 17th. The first graphic shows the connection between the stars of the Big Dipper, the curved handle, aka the “arc”, and the stars Arcturus and Spica.

   Follow the arc to Arcturus, then speed to Spica.”

    Dwarf Planet Ceres is shown but with an apparent 8th> would require optical assistance to be visible. Reddish Arcturus in Bootes the Herdsman has an apparent magnitude of -0.07 and is certainly visible.
   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.


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Follow the Arc to Spica, or Jupiter

   There is an ‘old’ Astronomical saying, a sort of memory aid, for finding at least two constellations by way of their alpha, or brightest star in their respective constellation. In Bootes the Herdsman there is the orange-reddish star Arcturus, and in Virgo the Harvest Maiden the bluish-white star Spica. The saying – “follow the arc to Arcturus, then speed to Spica” is how you connect these two stars with the curve, or arc, in the handle of the Big Dipper. This is typically done during the Northern Hemisphere spring and summer season when Bootes and Virgo are in the evening skies. However during the late autumn and winter months in the Northern Hemisphere this memory aid works best in the early morning skies before the Sun rises.
   So despite the graphic showing the morning sky for December 8th you could go out any morning for the next few months and find the 7 stars making up the Big Dipper. Then look for the curved handle and follow the arc or curved handle toward Arcturus and then continue on to Spica, or for the time being, the planet Jupiter.

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.

Follow the Arc to the Moon

   Thursday evening March 24th the 16-day old waning gibbous Moon rises about an hour after local time for sunset. About 3o from the Moon is the blue-white star Spica in the left hand of Virgo the Harvest Maiden.

   This is also the time of year when some would look at the sky and say, “Follow the arc to Arcturus and then speed to Spica.” This sort of silly sounding phrase links the curved handle, the arc, of the Big Dipper with the reddish star Arcturus in Bootes the Herdsman, and the blue-white star Spica. The Moon, at times, is part of the lineup as it is this time.

   
   
   
   

Caution: Objects viewed with an optical aid are further than they appear.
Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

Follow the Arc to a Pulsar!

   During Spring in the northern hemisphere, the seven bright stars that form the Big Dipper are easily seen high over the northern horizon. Located at the hindquarters of the Great Bear (Ursa Major), this asterism (group of stars) has long been used as a celestial guide by travelers. During the American Civil War, slaves memorized a song called “Follow the Drinking Gourd” that helped them locate the stars that would point their way to freedom. By walking in the direction of the ‘drinking gourd’ stars the escaping, freedom seeking slaves, would be following a northerly route taking them away from the slave states to the free states to the north, or to Canada.
   There is an ‘old’ Astronomical saying, a sort of memory aid, for finding at least two constellations by way of their alpha, or brightest star in their respective constellation. In Bootes the Herdsman there is the orange-reddish star Arcturus, and in Virgo the Harvest Maiden the bluish-white star Spica. The saying – “follow the arc to Arcturus, then speed to Spica” is how you connect these two stars with the curve, or arc, in the handle of the Big Dipper.
   Simply look toward the northeast to find the 7 stars making up the Big Dipper. Then look for the curved handle and follow the arc or curved handle toward Arcturus and then continue on to Spica. This is typically done during the Northern Hemisphere spring and summer season when Bootes and Virgo are in the evening skies.
   While you are looking toward this region of the sky, you can also investigate some of our neighboring solar systems.
   Scientists now believe that two sunlike stars in this region have at least one orbiting satellite each, and that a nearby pulsar could have up to three satellites. Just below the bowl of the Big Dipper lies 47 Ursa Majoris, a star with an orbiting object estimated to have two to three times the mass of Jupiter and a revolution rate of 1103 Earth days. Near the northern boundaries of Virgo, an object orbiting around 70 Virginis is estimated to have six to seven times the mass of Jupiter and a revolution rate of 117 Earth days. Although the objects themselves are too far away to be seen, the suns around which they orbit are visible to the naked eye.
   A third solar system you could direct your attention to is also within the boundaries of Virgo. Unlike the other two solar systems, the objects in this system orbit a pulsar, PSR 1257+12. A pulsar is a small, extremely dense, and rapidly rotating neutron star, a remnant of a massive star that has collapsed into itself following a supernova event. PSR 1257+ 12 gets its name from its celestial coordinates, 12 hours 57 minutes right ascension and 12o north declination. This pulsar is one of at least several known pulsars in our galaxy and this one has an estimated diameter of 16 km, and a mass that is one to two times that of our Sun.
pulsar   Pulsars earn their name from the radio waves they emit, which we receive in regular pulses. Pulsars emit radio waves as a narrow beam, much like the beam of light emitted from a lighthouse. Just as direct light from a lighthouse sweeps past a point regularly, so does the beam of radio waves emitted from a pulsar. PSR 1257+ 12 emits radio waves that reach the Earth with at an interval of 6.2 milliseconds. Because we receive pulsed radio waves from a pulsar as a result of its rotation, we know a pulsar’s pulse interval coincides with its period of rotation. This means that PSR 1257 + 12 rotates every 6.2 milliseconds!
kepler   Exo-solar systems and their planets have been detected through various methods with the greater majority of these exo-solar systems being discovered by the Kepler orbiting observatory. To date more than 1,000 objects have been confirmed as an exo-planet, with more than 4,600 objects waiting confirmation.
distant-worlds-cover   Download a series of monthly star maps and data pages. Each monthly star map shows the location of many of the stars we know or are reasonably certain that are stars with their own planets. Click here to download the “Where Are the Distant Worlds Star Maps”. (2-3 Mb PDF)

   
   
   
   
   
   
   
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Caution: Objects viewed with an optical aid are further than they appear.
Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

Follow the Arc

The ‘Evening Arc’

   There is an ‘old’ Astronomical saying, a sort of memory aid, for finding at least two constellations by way of their alpha, or brightest star in their respective constellation. In Bootes the Herdsman there is the orange-reddish star Arcturus, and in Virgo the Harvest Maiden the bluish-white star Spica. The saying – “follow the arc to Arcturus, then speed to Spica” is how you connect these two stars with the curve, or arc, in the handle of the Big Dipper. Simply look toward the north to find the 7 stars making up the Big Dipper, look for the curved handle and follow the arc or curve toward Arcturus and then continue on to Spica. This is typically done during the Northern Hemisphere spring and summer season when Bootes and Virgo are in the evening skies. However you can start this observation at sunset by looking northwest for the Big Dipper and then toward the southwest for the star Arcturus. Do this early enough as Arcturus sets about an hour after sunset and in the next couple of weeks Arcturus will become too close to the Sun and will not be visible again until later during the winter as a morning visible star.

The ‘Morning arc’

   And you could continue this observation the following morning as this part of the sky rises before the Sun and you trace out the arc passing through Arcturus and ending at Spica. As the ‘Morning Arc’ graphic shows the planet Venus is close to Spica.
   Keep an eye on this part of the sky as later this month the planets Saturn and Mercury start becoming visible before sunrise. On the 26th Venus will be very close to Saturn. As the graphic shows the two planets will be close enough for both to fit within the field of view of binoculars.

Click here to go to the Qué tal in the Current Skies web site for more observing information.