Our Current Sky

Our Current Sky

our-current-skiesWhat’s Up in Southwest Florida’s June Skies: Saturn at Opposition June 15; Solstice June 21: pretty pre-dawn sight

[NOTE: A Total Solar Eclipse will cross the United States on August 21, 2017.  Here in Fort Myers, FL, we are not along the path of totality, so we will see a partial eclipse. A full-country Eclipse 2017 USA map is here (opens in new tab).  An alternative map with local times is here (opens in new tab).]

At the very start of this month, four of the five classically-visible planets are again visible between dusk and dawn.  But Mercury will be invisible again by mid-month (too close to the Sun).

After nightfall, Jupiter is very bright and steadily glowing high in the South, not far from the bluish-white star Spica in Virgo.  Saturn starts the evening low in the east, and on June 15th Saturn is “at opposition” — directly opposite the Sun in Earth’s sky (Saturn, Earth and the sun are all in a straight line, with Earth in the middle), so it should be high in the South at 11 pm (daylight savings time). The best time to observe Saturn and Jupiter both in the night sky is from 10 pm until after midnight: Jupiter sets at 3 a.m. at the beginning of June but sets by 1 a.m. by the end of the month.

To see the cool details, you’ll need a telescope. This year is the right time to look at Saturn through a telescope: it’s at maximum tilt (26.6 degrees) to show the rings off to best advantage. You’ll have a great view of the biggest gap in the rings: the Cassini division. Sounds like a band, doesn’t it? The big gap between inner rings and outer rings was discovered in 1675 by Giovanni Domenico Cassini, namesake of NASA’s Cassini spacecraft. If you waited 7.5 years, those rings would be edge-on and you would be lucky to see them from Earth as a straight line across Saturn’s middle!  Opposition provides the best and closest views of Saturn, its brilliant icy rings and several of its brightest moons.  If you just see one moon near Saturn, that’s Titan. It’s HUGE!  Titan is 50% larger than our own moon. It orbits Saturn about every 16 Earth days. Our moon takes 27.3 days to orbit Earth relative to the background stars, but 29.5 days to go from full to full (because Earth is also moving along our orbit around the Sun during that month!).

By the way, we will be holding an event to commemorate the life accomplishments of the Cassini space probe in September: the spacecraft has been orbiting Saturn since 2004, but now is in its final mission phase. The Cassini Grand Finale has put Cassini on a trajectory that will eventually plunge it into Saturn’s atmosphere and end Cassini’s mission with atmospheric data and a fiery meteor on September 15, 2017. The decision to end the mission this way stems from a desire to keep Cassini from any possibility of crashing into either Titan or Enceladus after it runs out of orbit-adjustment (thruster) fuel. Titan and Enceladus are very special moons, where the possibility of (microbial) life is higher than in most other places in the solar system (except here on Earth, of course!).

Using that telescope I mentioned earlier, you can compare the cloud bands on Saturn to those on Jupiter. Saturn’s cloud bands are much fainter than the dramatic bands of Jupiter. Saturn’s bands vary from almost-white through a pale tan, but Jupiter’s vary from white through deep rusty red and in some spots red-brown. The most important difference here is that Jupiter is more massive AND a faster rotator than Saturn: Jupiter completes a full rotation on its axis in under 10 hours! It’s the fastest-rotating planet in the Solar System, as well as being the largest, so it has a tremendous rotational engine driving the deep views of darker (hotter, deeper, higher-pressure) bands in the Jovian atmosphere. Through binoculars, Jupiter’s four Galilean moons — Io (EYE-oh), Europa, Ganymede and Callisto — are easy to see, but often one of the four will be in front of or behind Jupiter when you look: the inner moons have very fast orbits, so it’s fun to track the changes from night to night.  NASA’s Juno mission recently completed its sixth Jupiter flyby, so you can see some amazing images of the weird polar regions of Jupiter on the June mission website — those are views we don’t get from Earth because we never see the poles of Jupiter (no axial tilt to speak of, only 3 degrees).

Venus dominates the pre-dawn planet lineup and will be brightening in the sky above the sunrise each day, so that anytime after 3 a.m. you will be able to see brilliant Venus in the East and  Saturn high above your southwestern horizon.

On Wednesday, June 21, 2017, at 12:24 a.m., the summer solstice will occur. That’s the longest daylight of the year for locations in the northern hemisphere. Here is what the pre-dawn sky will look like that morning (about 5 hours after the solstice):

2017-06-21-MorningSkyMoonVenusPleiades

The crescent moon is below brilliant Venus at 5:30 in the morning, and the Pleiades cluster in Taurus — AKA the “Seven Sisters” — is visible to the left of the Moon as you face East. That bright star off to the northeast is Capella.

Moon phases this month:

  • Jun 1     1st Quarter
  • Jun 9     Full
  • Jun 17     3rd Quarter
  • Jun 23    New

Heather Preston, Planetarium Director, Calusa Nature Center Planetarium, Fort Myers, FL

Astronomy News Bulletins:

  • Exploding Supernova will change Cygnus

Calvin College professor Larry Molnar and his students along with colleagues from Apache Point Observatory (Karen Kinemuchi) and the University of Wyoming (Henry Kobulnicky) are predicting a change to the night sky that will be visible to the naked eye.

“It’s a one-in-a-million chance that you can predict an explosion,” Molnar said of his bold prognostication. “It’s never been done before.”

Molnar’s prediction is that a binary star (two stars orbiting each other) he is monitoring will merge and explode in 2022, give or take a year; at which time the star will increase its brightness ten thousand fold, becoming one of the brighter stars in the heavens for a time. The star will be visible as part of the constellation Cygnus, and will add a star to the recognizable Northern Cross star pattern.

Read more at: http://phys.org/news/2017-01-astronomers-explosion-night-sky.html

  • Pro-AmComet Observing Invitation

Get in on the Pro-Am Comet Observing Action! Remember, the campaign starts later THIS MONTH: https://astronomynow.com/2016/11/24/worldwide-pro-am-help-sought-for-comet-trio-study/. The actual page with details is at the Planetary Sciences Institute, here: http://www.psi.edu/41P45P46P


Useful Sites for Backyard Astronomers…

Here is an off-site excellent summary (opens in new page) of night sky observables this month…

The International Space Station is visible some nights, and is very bright! For specific visibility direction, greatest altitude, and time at your location: https://spotthestation.nasa.gov/sightings/

The Hubble Space Telescope is visible some nights.  For specific times and routes: http://www.heavens-above.com/