This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Tuesday, July 10. All times are given as local St. Louis time (Central Daylight Time). For definitions of terminology used in the night sky update, click the highlighted text.

Information updated weekly or as needed.

Join us for our next star party, Friday, August 3, 2018 held in association with the St. Louis Astronomical Society. For details, see the information at the bottom of this page.

The Sun and the Moon
Sunrise is at 5:45 a.m. on Tuesday, July 10 and sunset is at 8:27 p.m. providing us with about 15 hours of daylight. Even after sunset, the light from the sun will still dimly illuminate our sky for roughly 2 hours. This period of time is called twilight, which ends around 10:21 p.m. this week. For those with a sun dial, solar transit or local noon occurs around 1:06 p.m. this week.

Day

Sunrise

Sunset

10 Jul

5:45 a.m.

8:27 p.m.

11 Jul

5:46 a.m.

8:27 p.m.

12 Jul

5:47 a.m.

8:26 p.m.

13 Jul

5:47 a.m.

8:26 p.m.

14 Jul

5:48 a.m.

8:25 p.m.

15 Jul

5:49 a.m.

8:25 p.m.

16 Jul

5:50 a.m.

8:24 p.m.

17 Jul

5:50 a.m.

8:24 p.m.

18 Jul

5:51 a.m.

8:23 p.m.

Moonrise  for Tuesday, July 10 occurs at 3:24 a.m. and moonset will occur at 5:59 p.m. on the following day. On Tuesday, July 10 the moon will be exhibiting a waning crescent phase with roughly 9% of the lunar disk illuminated. New moon occurs on July 12.

International Space Station (ISS) Observing
Visible passes of ISS from St. Louis for the week of July 10 occur in the morning and evening hours. The best of these occur on the mornings of July 11 and 18 and on the evening of July 18. Use the table below for information about these and other visible passes of ISS this week.

The last pass on July 18 will be an unusual pass. ISS will appear and then quickly enter Earth’s shadow only to come back into view a few minutes later above the opposite horizon. In many years of viewing ISS transit the sky I have never seen this.

Catch ISS from St. Louis starting Tuesday, July 10

Mag

Starts

Max. altitude

Ends

Time Alt. Az. Time Alt. Az. Time Alt. Az.

10 Jul

-1.0 02:07:13 17 NE 02:07:13 17 NE 02:08:05 10 NE

10 Jul

-1.1 03:39:51 10 NW 03:41:44 15 NNW 03:43:45 10 NNE

11 Jul

-1.5 02:49:21 21 NNW 02:49:21 21 NNW 02:51:54 10 NNE

12 Jul

-0.9 01:59:11 18 NNE 01:59:11 18 NNE 02:00:19 10 NE

13 Jul

-0.9 02:41:17 13 NW 02:42:07 13 NNW 02:43:51 10 NNE

14 Jul

-0.8 01:50:43 16 N 01:50:43 16 N 01:52:05 10 NNE

14 Jul

-0.6 05:03:24 10 NNW 05:04:58 13 NNE 05:06:31 10 NE

16 Jul

-0.8 04:54:57 10 NNW 04:57:25 19 NNE 04:59:53 10 ENE

17 Jul

-0.5 00:51:04 13 N 00:51:04 13 N 00:51:51 10 NNE

17 Jul

-0.6 04:03:07 10 NNW 04:04:57 14 NNE 04:06:48 10 NE

18 Jul

-2.0 04:46:37 10 NW 04:49:41 35 NNE 04:52:44 10 E

18 Jul

-2.5 21:26:03 10 S 21:28:35 21 SE 21:29:59 16 E

18 Jul

-1.9 23:01:48 10 WSW 23:06:17 24 NNE 23:07:59 10 NE

Magnitude (Mag): The Measure of brightness for a celestial object. The lower the value is, the brighter the object will be.

Altitude (Alt): The angle of a celestial object measured upwards from the observer’s horizon.

Azimuth (Az): The direction of a celestial object, measured clockwise from an observer’s location with north being 0°, east being 90°, south being 180° and west being 270°.

For information about ISS flyovers and other visible satellites, visit www.heavens-above.com

Detailed information regarding all unmanned exploration of our universe, missions past, present, and planned, can be found at Jet Propulsion Laboratories: http://www.jpl.nasa.gov/

The Planets Visible Without a Telescope

This week all five of the naked eye planets are visible. Mercury and Venus are in the west after sunset, Jupiter is visible after sunset in the south, Saturn is in the southeast a little after sunset and Mars is still best after midnight.

Mercury

Mercury can be a tough planet to see because it does not elongate too far from the sun before it heads back to the sun’s glare. Mercury is starting one of its best apparitions for 2018. This evening apparition will be at its best on July 12 as Mercury reaches greatest eastern elongation on this night. Your best chance to see Mercury this apparition will be between July 11 and July 13.

Right now Mercury can be see about 9° above the western horizon 30 minutes after sunset. If you have trouble finding Mercury in the twilight sky grab some binoculars and scan the horizon. If you do this make sure the sun has set so you do not accidentally look at the sun.

Venus

The second planet from the sun is climbing out of the sun’s glare. Typically the 30 minute mark after sunset is what we use to determine if a planet is visible yet. Using this approach Venus will be about 19° above the western horizon around 9:00 p.m.

The evening apparition of Venus that is starting will last all the way through October 2018. So for most of the year Venus will be an early evening target. Another observing note is that Venus will start in a gibbous phase and end this apparition in a crescent phase. Planets that are closer to the sun than we are exhibit phases like the moon does. As the apparition progresses Venus will grow brighter because it will be getting closer to Earth. On October 26 Venus will reach inferior conjunction which is when Venus passes between the Earth and Sun.

Venus and Mercury both exhibit phases like the moon does. This is due to them being closer to the Sun than Earth is. This is also why we only see these planets just after sunset or just before sunrise. Both Venus and Mercury are exhibiting gibbous phases. About 66° of the disk of Venus is currently illuminated which will continue to decrease as the year goes on. Small telescopes and large binoculars will reveal the phases of Venus.

Mars

The red planet has started another apparition and can be found rising in the east by 9:55 p.m. Due to trees and buildings Mars will be best seen after 11:00 p.m. Each week Mars will rise a little earlier than the week before as we approach the 2018 Mars opposition which occurs on July 27.

If you want to start preparing for the upcoming 2018 Mars opposition follow this link: http://www.alpo-astronomy.org/jbeish/2018_MARS.htm

Jupiter

The king of the planets rises before the sun sets. Start looking for it high in the south about 30 minutes after sunset. Jupiter will set by 1:43 a.m.

Saturn

Saturn has been visible in the southern sky for some time now however the angle of the summertime ecliptic will keep the ringed planet low in the southern sky. However, Saturn now rises before sunset so if you have a clear southeastern sky you should be able to spot Saturn by 10:00 p.m.

Our next Star Party will be held on Friday, August 3, 2018, from dusk until 10 p.m.

As part of the Saint Louis Science Center’s First Fridays, weather permitting, the St. Louis Astronomical Society and the Science Center will set up a number of telescopes outdoors and be on-hand to answer your questions. Telescope viewing begins once it is dark. Regardless of the weather on August 3, join us indoors in our planetarium theater for “The Sky Tonight”. Showtime is at 7 p.m.

This free, indoor star program will introduce you to the current night sky, the planets, and the seasonal constellations. Doors open 15 minutes before show time. Shows begin at 7 p.m. Sorry, no late admissions due to safety issues in the darkened theater.

The St. Louis Astronomical Society helps host the monthly Star Parties at the Saint Louis Science Center which are held on the first Friday of each month. Our Monthly Star Parties are open to the public and free of charge. Telescope viewing is scheduled to start around 7:00 p.m. however with the change to daylight saving time, darkness starts closer to 8:00 p.m.