What’s Up! July 2019

A monthly look at astronomical events in the sky and on Earth

See What’s Up! for June 2019

The Moon

Best seen as a thin waxing crescent low in the west after sunset on Fri 5th to late gibbous low in the south on Sat 13th. It doesn’t climb much above 18° altitude throughout this period due to the angle of the ecliptic at this time of year. Jupiter will be seen about 1.5° below it on the 13th.

Partial Eclipse of the Moon on July 16th

On that date, the moon will rise in the SE at 2123 BST partially eclipsed. The eclipse will continue until midnight, with its maximum at 2230. The sky view below shows the situation at 2230; note the partially eclipsed moon near lower left together with Jupiter and Saturn.

Night sky for partial lunar eclipse
Night sky for partial lunar eclipse showing Saturn and Jupiter (Stellarium screenshot)

See the full details of the eclipse.

The Sun

If you happen to be visiting the South Pacific, Chile or Argentina, then there’s a total solar eclipse on the 2nd July. All right for some!

Planets

Mercury, Venus and Mars:

All too near the sun to be observable this month.

Jupiter

Jupiter reached opposition on the 10th of June and is observable in the late evenings throughout the month. Unfortunately, it rises to only a little less than 14° so will suffer from poor seeing and a lessening of brightness due to that low altitude. The optimum time to view it is when it transits (is due south) and this occurs at 2330 on the 1st, 2230 on the 15th, and 2130 on the 30th.

One thing that’s not affected by poor seeing is the visibility of the four Galilean moons as they perform their orbital dance. As the moons pass behind Jupiter they disappear, but what’s worth looking out for is when they reappear. Interestingly, once we’re a week or so beyond opposition, a moon emerging from behind Jupiter is still in its shadow and is there but we can’t see it because it’s eclipsed. And if you’re looking at the right time, the moon suddenly appears as if by magic, not from behind Jupiter but some distance from it, to its east. Here are three examples that can be seen  this month. Start looking two or three minutes before the time, to ensure you don’t miss the appearance. And make sure you know which way east is as seen in the eyepiece. If you’re not sure, it’s the direction away from which the planet is moving. If you have a driven telescope, stop the drive for a moment to see which way the planet drifts.

Date Time (BST) Satellite Notes
July 14th 2319 Io  
July 18th 2349 Europa  
July 30th 2138 Io Only 30 mins after sunset.
Screenshot of Jupiter showing the Galilean moons on 14 July
This is the view just after Io’s appearance on July 14. (From SkyViewCafe.com)

Saturn

Saturn reaches opposition on the 9th of July. Unfortunately, like Jupiter, it only climbs to an altitude of 14° and is thus best seen within an hour either side of transit. You might care to wait until August to see it, but if you don’t want to wait, the transit times are 0146 on the 1st, 0047 on the 15th, and 2339 on the 30th. One good thing about this opposition is that Saturn’s rings are really wide open and well seen.

Non-Solar System Objects

Deep Sky

June and July are difficult months to observe deep sky objects because the sky never gets really dark, but they are also the months when some famous nebulae and clusters are visible. These are clustered in the direction of the galactic centre and therefore low in the sky. If you don’t have a go at them in July – the best time – then you’ll miss out until next year. Unfortunately, the Moon is a big problem between the 10th and the 23rd, so avoid that 14 day period. The other thing you need to accept is that these objects can only be seen well very late at night. e.g. around 0100 BST before the 10th and midnight after the 23rd. But if you’re keen enough, your efforts will be rewarded.

The sky view below shows these objects at 0100 on the 5th (or midnight after the 23rd).

Deep sky objects visible in July 2019
Deep sky objects visible in July 2019 (screenshot from SkyViewCafe.com)

Some of the objects listed in the table below can be seen with the naked eye and all are well seen in binoculars or a small telescope.

Messier No.MagnitudeDescription
M115.8The Wild Duck Cluster. One of the richest open clusters (2,900+ stars).
M166.0The Eagle Nebula, cluster and cloud of hot gas. Famous for the Pillars of Creation feature at its centre.
M176.0The Omega Nebula. A cluster of 35 stars within cloud of gas.
M215.9Open cluster of about 40 stars. Impressive in a small telescope.
M225.1Bright globular cluster of about 70,000 stars.
M235.5Loose galactic cluster of about 150 stars
M254.6Compact galactic cluster of about 86 stars of various colours.

Noctilucent Clouds

July is a great month for looking out for the eerie and beautiful noctilucent clouds. (From the Latin for night shining.) These are ice crystal clouds, and the highest on Earth, at about 50 miles up. They can only really be seen between midnight and 2 a.m. low above the northern horizon if the sky is otherwise clear.  The image below was taken on 19th June this year.

Noctilucent clouds
Noctilucent clouds shot by Nando Harmsen of Fstoppers

Passes of the International Space Station (ISS)

July is a particularly good month to spot the ISS as it passes over the UK. It can be very bright as it catches the sunlight high above us when from the ground, the sun has already set. It is visible on the 5th then every night from the 7th to the 31st inclusive. On many nights it is visible twice, and on some nights, three times. The Heavens-Above web site has an excellent visibility table. Use it like this:

  • Note (in the top right) that I have set the link to provide the visibility from York.
  • Note the “Search period start” and “Search period end” indicators.
  • Move to a later or earlier date range by clicking the arrow buttons.
  • Ensure that the “visible only” radio button is selected.
  • If no table entries are shown for a particular date range, the ISS is not visible on those days.
  • The “Start”, “Highest Point” and “End” columns indicate when and in what direction the ISS can first be seen, reaches its highest point in the sky, and disappears respectively.
  • In the FAQ on the web site it states that all the times in the tables are “given in local time”.

Space News

For up-to-date news on space missions, rocket launches etc. scroll https://www.space.com/32286-space-calendar.html

Other News

The world famous Sky&Telescope magazine, founded in 1941, has been acquired by the professional organisation, the American Astronomical Society. The magazine has been published for some years by F+W Media, but they have just filed for bankruptcy. The AAS paid $1.23 million for the magazine and have assured staff and readers that the existing staff will remain in post and the magazine will carry on as normal. Full story here.

Clear skies and good viewing.

John Rowland 22/06/2019