Saturday: Cygnus the swan flies tonight. Deneb, the brightest star in the constellation, whose name means “tail” in Arabic, is two and a half fists held upright and at arm’s length above due northeast at 10:00 p.m. Cygnus’ wings make a vertical line one half a fist to the right of Deneb. Its head, marked by the star Albireo, is two fists to the right of Deneb. While Deneb is at the tail of Cygnus, it is at the head of the line of bright stars. It is 160,000 times more luminous than the Sun making it one of the brightest stars in the galaxy. It does not dominate our night sky because it is 2,600 light years away, one of the farthest naked eye stars. If Deneb were 25 light years away, it would shine as bright as a crescent moon. Compare that to Vega, its fellow Summer Triangle star. Vega IS 25 light years away and certainly doesn’t rival the light of the crescent Moon. Vega is about two fists to the upper right of Deneb.
Sunday: Mercury will be as far away from the Sun in the sky
as it will get this orbital cycle. This "farthest away" point is
known as the planet's greatest elongation. Since Mercury is in the morning sky,
it is west of the Sun and this occurrence is called the greatest western
elongation. This morning, Mercury is just above the east-northeastern horizon
at 4:30 a.m., near Jupiter, the brightest point of light in the sky at this
time. Over the next few weeks, Mercury will move toward the Sun in the sky. By
mid July, it will be visible in the evening sky.
Monday: Stonehenge was created on the island of Great
Britain by Neolithic people. “Manhattanhenge” was created on the island of
Manhattan by modern day architects and construction workers. Twice a year, the
end of May and mid-July, the setting Sun aligns perfectly with the Manhattan
grid pattern. That means observers will see the Sun set at the end of the
street. The first Manhattanhenge sunset is tonight at 8:13 p.m. Eastern time
and then again tomorrow at 8:12 p.m. Eastern time. For more information about
Manhattanhenge, go to https://www.amnh.org/research/hayden-planetarium/manhattanhenge.
Tuesday: Spica is less than a half a fist to the lower left
of the moon. Both are in the southern sky at 9:30 p.m.
Wednesday: Venus is two and a half fists above the western
horizon at 9:30 p.m. The stars Pollux and Castor are just to the upper right of
Venus. The planet Mars is a little less than a fist to the upper left of Venus.
To the upper left of Mars is the Beehive Cluster, an open star cluster
consisting of about 200 stars.
Thursday: Altair, the lowest star in the Summer Triangle, is
about one fist above due east at 10:45 p.m.
Friday: As the weather warms up, people start thinking about
swimming in a nice cool body of water. A few years ago, astronomers discovered
evidence of an ocean about 20 miles beneath the surface of Saturn’s moon
Enceladus. NASA’s Cassini probes measured variations in how the moon’s gravity
pulled on the orbiting spacecraft. These variations can be explained by a large
amount of liquid water under one section of the ice because liquid water is
denser than an equal volume of ice. While you need a very large telescope to
see Enceladus, you can easily see Saturn two fists above due southeast at 4:30
a.m.
The positional information in this column about stars and
planets is typically accurate for the entire week. For up to date information
about the night sky, go to https://nightsky.jpl.nasa.gov/planner.cfm.
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