Saturday: At 10:00 p.m., very bright Venus is one and a half fists held upright and at arm’s length above the western horizon. Jupiter is to the lower right of Venus, a half a fist above the horizon. Mercury is to the lower right of Jupiter, just above the west-northwestern horizon.
Sunday: At 1:25 a.m. today, the Sun reached its highest
declination (the official name for sky latitude) of 23.5 degrees above the
celestial equator. The celestial equator is the line that divides the northern
sky from the southern sky. That makes today the first full day of summer. In
Ellensburg, the Sun is about seven fists held upright and at arm’s length above
the south horizon at 1:00 p.m. (noon standard time) on the first day of summer.
Contrary to widespread belief, the Sun is never straight
overhead in Ellensburg or anywhere else in the 48 contiguous states. The
northernmost portion of the world where the Sun can be directly overhead is
23.5 degrees north latitude. In ancient times, the Sun was in the constellation
Cancer the crab on the first day of summer. Hence, 23.5 degrees north latitude
has the nickname "Tropic of Cancer". Because the Earth wobbles like a
spinning top, the Sun's apparent path through the sky changes slightly over
time. Now, the Sun is in the constellation Taurus the Bull on the first day of
summer. However, citing the high cost of revising all the science books,
geographers are not changing the name of 23.5 degrees north latitude to
"Tropic of Taurus". The first day of summer is often called the
summer solstice. However, astronomers refer to the summer solstice as the point
in the sky in which the Sun is at its highest declination above the celestial
equator. Summer starts when the Sun is at the summer solstice point.
Monday: Don’t wait until July 4 to watch those wimpy
firecracker shows. Find the hypergiant star Rho Cassiopeiae. Astronomers think
that Rho Cassiopeiae will likely go supernova (explode) in the near future. Of
course, for stars, “near future” might mean tomorrow. It might mean 20,000
years from now. Rho Cassiopeiae is in the constellation Cassiopeia the queen.
At 11:00 tonight, Cassiopeia looks like the letter “W” about two and a half
fists above the north-northeastern horizon. Rho Cassiopeiae is about a finger’s
width to the right of the rightmost star in the “W”. Once you find it you’ll be
thinking, “Big deal, I can hardly see it.” Although it is barely visible to the
naked eye, it is actually very bright. It is the 20th most luminous
star in the sky, a whopping 550,000 times more luminous than the Sun.
Tuesday: The bright star Spica is about a half fist to the
upper right of the moon, in the south-southwestern sky at 10:00 p.m.
Wednesday: “Mom, I can’t sleep. It is too light out!” A poor
excuse you say. Good astronomy skills, I say. The latest sunset of the year
happens around this date. Surprisingly, the earliest sunrise and the latest
sunset do not both happen on the longest day of the year, the day of the summer
solstice. The earliest sunrise occurs just before the longest day and the
latest sunset occurs just after the longest day. This phenomenon relates to the
angle of the Sun’s path near rising and setting. In Ellensburg, that angle is
about 66 degrees above the southern horizon at noon near the first day of
summer. Because of the Earth’s orbit, which causes the Sun’s apparent motion,
the angles are not symmetric. The asymmetry in orbital angles leads to the
asymmetry in rise and set times. This year, the sun sets at about 9:01 p.m.
every night the rest of this week as viewed from Ellensburg, WA. Find sunset
data for your location at https://www.timeanddate.com/sun/.
Thursday: At 4:00 a.m., Mars is one fist above the
east-northeastern horizon. Saturn is two and a half fists above the
south-southeastern horizon at this time.
Friday: The bright star Antares is about a half fist to the
left of the moon at 11:00 p.m., one and a half fists above due south. If you’d
like to learn more about stars like Antares, the CWU Lydig Planetarium has free
shows at 3:00 p.m. and 5:00 p.m. today. They are in Discovery Hall, room 101.
Here is a Google maps link: https://maps.app.goo.gl/Nwp1e5t7qXk5bfE9.
Parking on campus is free after 4:30 p.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.
All times are Pacific Time unless noted.