June 2001 Sky from Keeble Observatory

The Cosmic Microwave Background (CMB) has been called the afterglow of the Big Bang. First predicted in 1948 by Ralph Alpher and Ralph Herman, and actually discovered in 1964 by Arno Penzias and Robert Wilson, this radiation contributes about 1% of the static you pick up on your radio and television. Theory tells us that any object whose temperature is above absolute zero (-273 degrees Celsius, or - 459 degrees Fahrenheit, or 0 Kelvin) will give off electromagnetic radiation. The CMB has all the characteristics of an opaque surface at 2.7 Kelvin, and is virtually isotropic, that is it is the same in all directions.

We interpret this as a snapshot of the young universe, just at the instant it cooled below the temperature where all matter was ionized. The matter at the time would have been a mix of hydrogen and helium atoms, and the temperature of about 10,000 Kelvin would have occurred when the universe was only a few hundred thousand years old. The Cosmic Background Explorer satellite (COBE) made a detailed measurement of the CMB in 1992, and found subtle variations in the temperature of the background radiation, on the order of .0001 degrees, which hints at small variations in the density of material at the instant of transparency.

These density variations, believed to be result of sound-like waves rippling through the hot plasma, are also believed to be the seeds around which galaxies formed. Until now, however, there has been scant observational confirmation that the large-scale structure of superclusters of galaxies could have grown from these early sound waves. A group of observers, using the 4 meter Anglo-Australian Telescope at Coonabaraban, Australia, may have changed that. At a conference held the first week of May, they reported evidence that the observed clumps and filaments in the way galaxies are distributed in space bears the imprint of those same acoustic signals. The scale of the present day fluctuations is from 300 million to about 1.5 billion light-years. (Our nearest galactic neighbor, the Andromeda galaxy, is about 2 million light years distant.) As with all scientific discoveries, this one will have to be confirmed by further observations, but it's exciting to think that we now have a convincing connection between those early ripples in the background radiation and the present universe.

Lunar phases for June: Full Moon on the 5th, at 9:39 pm; Last Quarter on the 13th, at 11:28 pm; New Moon at 7:58 am, on the 21st; First Quarter at 11:19 pm, on the 27th.

Evening planet watchers will have to content themselves with Mars, which rises within 90 minutes of sunset at the beginning of the month, reaching opposition on the 13th (rising at sunset). It will be particularly bright all month, and remains visible until fading into morning twilight. Venus will be bright in the east at dawn, with Saturn appearing a bit below and to the left after mid-month. For the frequent flyers, a total solar eclipse will be visible in the South Atlantic, beginning at sunrise off the coast of Uraguay. The Moon's shadow will race across the Atlantic to Africa, crossing Angola, Zambia, and Mozambique. We'll miss it in Virginia!

Summer is not the best observing time from central Virginia, as we find rising humidity and typically hazy conditions. But, for those nights when the sky is clear enough, here's what to expect: Towards the north, we find the "Big Dipper" in Ursa Major inverted, with the bowl of the dipper high above Polaris. Following the curve of the "handle" towards the south, we encounter Arcturus on the southern side of zenith. If we continue along the same arc, we find Spica about 40 degrees above the southern horizon. Turning towards the west, we see Regulus, in the constellation Leo. The familiar sickle of Leo's head is curved towards the horizon. Barely visible to the northwest, just above the horizon and probably lost in the haze we bid farewell to Castor and Pollux in Gemini. To the southeast, Mars is below and to the left of its rival, Antares. Mars will win the battle this month! To the northeast, Vega and Deneb are just rising from the horizon clutter and haze.