Page 22

22 • JULY 2017

www.desertexposure.com

THE STARRY DOME • BERT STEVENS

Circinus, the Compasses Unique, interesting star system features different gases, X-rays

505-469-7505 sivaraven@gmail.com

non-denominational

Valley Community Church

19-A Racetrack Road, Arenas Valley, NM Sunday Worship at 10 A.M. Vacation Bible School July 10 thru 14 9:30 A.M. To Noon Phone: 575-538-9311 for more info

Where Everyone is Welcome!

Open Your Mind Join with us for our Sunday morning service 10:00 AM Enjoy Fellowship & Stimulating Topics

Unitarian Universalist Fellowship of Silver City 3845 North Swan

Questions: (575) 538-0101

Eighth Year Anniversary Saturday, August 5 from 11am - 6pm

Music will be provided by Teresa Smergut Noon - 2:00pm Brandon Perrault & Friends 2:30pm - 5:30pm Food available for purchase by

Acosta Farms

Hamburgers, Fajitas & Quesadillas

La Esperanza Vineyard and Winery is located off Royal John Mine Road off Hwy 61. A 30 minute scenic drive from Silver City.

Come and celebrate this very special occasion with International Our Regular Wine Tastings David & Esperanza Gurule owners/vinters Award-Winning WINES Fridays - Saturdays 11am-6pm 505 259-9523 • 505 238-6252 Sundays Noon to 6pm Anniversary Special www.laesperanzavineyardandwinery.com

La Esperanza Vineyard and Winery is located off Royal John Mine Road off Hwy 61. A 30 minute scenic drive from Silver City.

20% DISCOUNT for Case of Wine Mix or Match New Mexico Handcrafted Beers will be available for purchase Please visit our website for more information.

Our Regular Wine Tastings David & Esperanza Gurule owners/vinters Fridays - Saturdays - Sundays 505 259-9523 • 505 238-6252 Noon to 6pm www.laesperanzavineyardandwinery.com

O

n July evenings, the very top of the constellation Circinus, the Compasses, peaks over our southern horizon for just a few hours. This constellation has just a few stars that are bright enough to be seen from the city, but they all stay below our southern horizon. Circinus is a small constellation, 85th out of the 88 official constellations. Circinus has no mythological story related to its presence in the sky; indeed, it was not even known in ancient times. It came into existence in 1756 when French astronomer Nicolas-Louis de Lacaille was assembling a list of 400 of the brightest stars that he observed and recorded during his stay in South Africa. He created Circinus as a pair of dividing compasses with the French name le Compas. Circinus was one of the 14 constellations he fashioned at that time. It, along with two adjoining constellations, represent a set of drafter’s instruments, the Square (Norma), the Southern Triangle (Triangulum Australe), and the Compasses (Circinus). The names were changed from French to the modern, Latinized, names in his star catalog of 10,000 southern stars published in 1763, a year after his death. Alpha Circini is the brightest star in Circinus, but it shines at a rather faint magnitude 3.2. It is a middle-aged white star like many stars in the sky. However, unlike many stars, it pulsates very rapidly, as quickly as every 6.8 minutes. It also has slower cycles, some as long as four months. Alpha Circini has localized magnetic fields up to 500 times that of our sun. This star’s outer atmosphere lacks the usual amount of carbon, nitrogen and oxygen, while it has an excess of strontium, chromium and europium compared to stars like our sun. The chemical abnormalities are likely caused by those localized magnetic fields, but exactly how they cause these chemical anomalies is unknown. This star is also a rapid rotator, taking only 4.8 days to make one turn, compared to almost 30 days for our sun. This rapid rotation contributes to the unusual composition of the star’s atmosphere as well. Another star in this constellation goes by the name Circinus X-1. From the designation, you can probably guess that this is an X-ray star. X-rays from celestial sources are absorbed by our atmosphere, so we cannot observe them directly from here on Earth. So in the 1960s astronomers began launching sounding rockets with detectors to scan the sky for X-rays. Some of the earliest of these were launched from White Sands Missile Range here in New Mexico. Sounding rockets do not send their instrument packages into orbit, but still get them above the atmosphere for around 15 minutes before they return to Earth. On June 14, 1969, astronomers launched an Aerobee 150 sounding rocket from Natal, Rio Grande de Norte, Brazil, to study the southern sky in X-rays. It detected a source in Circinus that was first called

Even at its highest, only the very northern end of Circinus, the Compasses, rises above our southern horizon. This tiny constellation contains only a few stars that would be visible from a suburban area. Nevertheless, with Circinus being in the middle of the Milky Way, there are 493 variable stars and a few stars that have planets orbiting them. There are also three open clusters and a planetary nebula visible through small telescopes in this constellation.

Calendar of Events – JULY 2017 (MST) 08 10:07 p.m. 16 1:26 p.m. 23 3:46 a.m. 29 11 p.m. 30 9:23 a.m.

Full Moon Last Quarter Moon New Moon Mercury greatest distance east of the Sun (27 degrees) First Quarter Moon

Circinus XR-1, but later renamed to Circinus X-1. Since then, NASA has launched the Chandra X-Ray Observatory into orbit to allow for a more prolonged study of the sky in x-rays than sounding rockets allowed. Chandra studied Circinus X-1 and provided new information on this star. Astronomers determined this star is 30,700 light-years away from us. Circinus X-1 started out as a binary star system with the primary star being between eight and 20 times the mass of our sun. The secondary star was also a massive star, but somewhat smaller, and thereby longer-lived. The primary star soon reached the end of its life in a supernova explosion when its core collapsed, sending out a shockwave that tore the star apart no longer than 4,600 years ago (as seen from Earth). When the core collapsed, it formed a neutron star as gravity forced all the electrons into the protons to form neutrons, which along with the existing neutrons, became packed very closely together. This makes a neutron star extremely dense. The explosion also kicked the neutron star into an elliptical orbit. When it comes near the remaining secondary star, it pulls some of the gas from the younger star’s atmosphere. Both the gas cloud left over from the supernova explosion and the neutron star as it absorbs the stolen gas, emits the X-rays that we can observe with the Chandra. On June 2, 2005, Chandra’s observations revealed that an additional source of x-rays in the Circinus X-1 system is jets of ionized gas being blasted out from the neutron star. This normally only happens with a black hole, not a neutron star. This is the first extended x-ray jet associated with a neutron star in a binary system, marking Circinus X-1 as a unique and very interesting star system.

The Planets for July 2017 Mars is still too close to the Sun to

be seen this month. It moves from central Gemini to central Cancer. Mercury makes an appearance in the evening sky for most of the month. It will be nine degrees up in the west-northwest as it gets dark, setting around 9:30 p.m. The Messenger of the Gods travels from central Gemini, through Cancer and into central Leo where it ends the month. At midmonth, its disc will be 6.2 seconds-of-arc across and 67 percent illuminated. Mercury shines at magnitude -0.1. It will be furthest from the Sun on July 29. Jupiter is 40 degrees above the southwestern horizon as it gets dark. Glowing at magnitude -2.0, the King of the Planets has a disc that is 35.7 seconds-of-arc across. It is moving slowly eastward in central Virgo and it sets around 12:15 a.m. Further east, in southern Ophiuchus, Saturn is moving slowly westward. The Ringed Planet shines at magnitude +0.4 in our evening sky. The Rings are 40.9 seconds-of-arc across, tilted down 26.7 degrees with the northern face showing. Saturn’s disc is 18.0 seconds-of-arc across. It is 27 degrees above the southeast horizon as it gets dark and sets by 1:30 a.m. Rising just three hours before the Sun, Venus appears on the east-northeastern horizon at 3:15 a.m. Shining at magnitude -4.1, the Goddess of Love’s disc is 16.1 seconds-of-arc across at midmonth and 69 percent illuminated. During July, it moves eastward from western Taurus, through far northern Orion, and then into far western Gemini. Each day begins with brilliant Venus heralding the return of the Sun, ending the short summer nights during which we “keep watching the sky”! An amateur astronomer for more than 45 years, Bert Stevens is co-director of Desert Moon Observatory in Las Cruces.

Desert Exposure - July 2017  
Desert Exposure - July 2017