Sky Scene March to May 2001

<body topmargin=0 leftmargin=0 marginheight=0 marginwidth=0> <table cellpadding=0 cellspacing=0 border=0><tr> <td valign="top" colspan=2 height=22 BGCOLOR="#330099" TEXT="#080000" bgproperties="fixed" background="040000d2erkqrf.gif"> <div> Derby and District Astronomical Society - Aries Magazine</div> <div> </div> </td> </tr><tr> <td valign="top" width=145 BGCOLOR="#333399" TEXT="#080000" background="03fa2c00erkjzj.gif"> <div> <A HREF="index.htm" TARGET="_top" TITLE="Aries Astronomy magazine on line From th"><U>HOME</U></A></div> <bR> <div> <A HREF="editorial26.htm" TARGET="_top" TITLE="Aries on line Spring 2001 editorial"><U>Aries on line - Spring 2001 editorial</U></A></div> <div> <A HREF="id39.htm" TARGET="_top" TITLE="Forgotten Astronauts"><U>Forgotten Astronauts</U></A></div> <div> <A HREF="id41.htm" TARGET="_top" TITLE="New cosmological theory"><U>New cosmological theory</U></A></div> <div> <B>Sky Scene March to May 2001</B></div> <bR> </td> <td valign="top" height=458 BGCOLOR="#FFFFFF" TEXT="#080000" background="06a92963.gif"> <div> <B>Aries Astronomy magazine on line- From the Derby and District Astronomical Society</B></div> <div> <IMG SRC="04107040.gif" border=0 width="263" height="4" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <div> Sky Scene</div> <bR> <div> <I><B>March</B></I></div> <bR> <div> Taurus and Orion are sinking low in the west by 10 p.m. this month. Castor and Pollux in Gemini are still noticeable whilst Capella is prominent in the north-west. Regulus and the ‘Sickle’ asterism of Leo are obvious in the south and below it is the constellation of Hydra, with no bright stars. The ‘Plough’ of Ursa Major is well placed for observing the galaxies in this part of the sky. In the east, Spica and Arcturus are rising, always a sign that Spring is on its way. Jupiter and Saturn are sinking lower in the west and will set around midnight by the middle of the month. Mars is a morning object, together with the elusive Mercury and Neptune. The latter two will not be easy to spot. The second half of this month will be good for deep sky observers – the Leo/Virgo galaxies are high in the sky and the Moon will be out of the way by midnight after the 18th.  In Leo,  the brightest of the galaxies are M65 and M66, both about magnitude 9. They are spiral galaxies but M65 is actually edgeways on to our line of sight and thus appears as an elliptical galaxy. They will, however, appear as little more than misty patches of light in small telescopes. If you relish a more difficult challenge, try to find M95 and M96. In terms of double stars, find gamma Leonis and use a high power magnification. You should see that it is a magnificent pair of orange-yellow stars. But, how about a sextuple star! Castor, the brightest star in Gemini, appears as a single bright star to the naked eye. Using a moderate size telescope and a high power, you find that it is in fact two blue-white stars. Looking carefully with a larger telescope, it is possible to see a third star in the system – orange-red, faint at magnitude 9. Using a spectroscope, all three stars are found to be doubles, too close together to be separated using even the largest of telescopes. </div> <bR> <div> <I><B>April</B></I></div> <bR> <div> The two bears, Ursa Major and Minor stand high in the sky on April evenings. The 7 brightest stars of Ursa Major form one of the best known asterisms in the sky – the Plough. Unlike most stars in asterisms and constellations, five of the seven stars are related, moving at the same speed and in the same direction through space. As a result, in 100,000 years, the plough shape will be unrecognisable. In the pan handle, you can observe the double star of Alcor and Mizar. The two are actually about 30 light years apart in space and so are not physically related as a binary. Closer inspection of Mizar does however reveal a 4th magnitude companion, orbiting in a 10,000 year cycle. This companion was discovered in 1650 by Italian astronomer Giovanni Riccioli. Mizar was thus the first double star to be discovered by telescope. Another first for Mizar was that it was the first double star to be photographed, by Harvard’s George Bond in 1867. Furthermore, it was the first star to be discovered to be a spectroscopic binary by another Harvard astronomer, Edward Pickering. Subsequently, both the companion of Mizar and also Alcor, were found to be spectroscopic binaries. A remarkable stellar grouping indeed! Major is also home to several notable galaxies. The elusive M101 lies on the border of Ursa Major and Bootes. It is large but has a low surface brightness and it is that which makes it hard to see – just ask John Holmes! M109 lies close to Phecda, the bottom left of the plough blade whilst M 108 lies near Merak. M 81 and M82 are two related galaxies, at a distance of about 10 million light years from Earth, north and west of the blade. Just over the border from the handle of the plough lie the galaxies of M51 and M 106. </div> <bR> <div> <I><B>May</B></I></div> <bR> <div> M51 is still visible this month, it lies in the constellation of Canes Venatici – the hunting dogs. Its popular name is the whirlpool galaxy. This is because it was the first galaxy in which the spiral structure was observed. In 1845, Lord Rosse turned his 72 inch reflector on this galaxy and drew a diagram that distinctly showed structure in the galaxy. It has an interesting feature of a small satellite galaxy at the end of one of the spiral arms, this is visible in moderate size telescopes. Follow the curve of the Plough’s handle and you will see a very bright star. This is Arcturus, the fourth brightest star in the sky. It is much bigger (about 27 times bigger) and gives out about 100 times more light. Despite this, it is more or less the same mass as the Sun. Arcturus is a red giant (orange in fact). A red giant is a star in its last stages. The nuclear fuel in its core runs out and so the next layer begins to ‘burn’. The effect of this is to cause the star to swell in size and lowers the surface temperature. What you are seeing is a picture of our Sun about 5,000 million years into the future. The Earth will be destroyed when this happens, it will actually end being swallowed by the Sun as it becomes a red giant. </div> <bR> <div> <I><B>If you are new to astronomy, why not visit the </B></I><A HREF="http://go.to/astrodictionary" TARGET="_top" TITLE="http://go.to/astrodictionary"><U><I><B>DDAS on line astronomical dictionary</B></I></U></A><I><B>?</B></I></div> <bR> <div> I have not included any star charts here because there are plenty of astronomy books and places on the web  that you can get them. </div> </td> </tr></table></body>