Skywatch Line for Friday, August 2, through Sunday, August 4, written by Sam Salem
This is Dudley Observatory’s Skywatch Line for Friday, August 2, through Sunday, August 4, written by Sam Salem.
On Friday, Sun rises at 5:48am and sets at 8:14pm; Moon rises at 3:23am and sets at 7:41pm.
On the Friday and Saturday mornings, the thin waning crescent Moon will slide by Pollux and Castor, the “twin” stars of Gemini. Pollux is a bit brighter and golden in color. Castor appears white. The dark portion of the Moon will be glowing with earthshine. That’s reflected light from the Earth. The Moon will rise about two hours before sunrise.
Week by week, Venus is getting just a little less low in the sunset. bring binoculars or a wide-field telescope to a place with a very low west horizon, start scanning for them about 20 minutes after sunset. Try to find Venus and then detect Regulus and Mercury to its left. Venus is by far the brightest, magnitude –3.9, so you’ll pick it up it first. It’s a little to the right of due west. Upper left of it are Mercury, fading to +1.3, and Regulus, twinkling at +1.4 magnitude. By August 2nd, Regulus and Mercury are 3° and 8° to the left of Venus, respectively.
Mars and Jupiter, magnitudes +0.9 and –2.1 in the constellation of Taurus, rise by about 2 am., with Aldebaran tagging along with them. Watch for them to come up in the east-northeast. Mars shines upper right of brighter Jupiter. Twinkly Aldebaran is more directly right of Jupiter. Above all three are the Pleiades.
Saturn, magnitude +0.9, near the Aquarius-Pisces border, rises in the east right after the end of twilight. Watch for it to come up lower right of the Great Square of Pegasus, which is balancing on one corner. The Square’s top-right edge points diagonally down almost to Saturn, two fists at arm’s length away. Saturn reaches its highest position in the south, in the steadiest atmospheric seeing for a telescope, in the couple hours before the start of dawn.
Bright Vega passes closest to overhead around 11 pm.
Deneb crosses closest to the zenith almost exactly two hours after Vega. But to see Deneb exactly straight up you need to be farther north, at latitude 45°.
The recurrent nova T Corona Borealis could erupt to 2nd magnitude anytime this summer, or fall, or later. Astronomers are pretty sure it’s getting set to blow sometime soon, for the first time since 1946. Look a third of the way from Arcturus to Vega. There’s Alpha Coronae Borealis, also known as Alphecca. At magnitude 2.2 it’s the only moderately bright star in the delicate Northern Crown. Alphecca is easy to see through suburban light pollution. The rest of Corona Borealis is not.
In 1866 and 1946 T Cor Bor peaked at 2nd or 3rd magnitude, roughly matching Alphecca. Even as it simmers along at its normal 10th magnitude, T CrB is an easy pickup with a small telescope. Give it a look while it’s still gathering its forces.
T Cor Bor’s rise last time took just a few hours, and its peak brightness lasted only a day or so.