Skywatcher's Guide: June and July 2020
- Stars and Constellations
- Solar System
- Calendar of Night Sky Events
- Deep Sky
- Frequently Asked Questions
Stars and Constellations
In June, the spring sky is now prominent overhead, along with the familiar Big Dipper. The Big Dipper is high in the north, and the two stars at the end of the bowl can be used to find Polaris, our north star. Also, the handle can be used to "arc to Arcturus", a bright star in the constellation Boötes. Then Hercules is just below towards the east. Next, Leo the lion is very high in the west, with the constellation Virgo nearby to the south. A few winter constellations are still visible, now vert low in the west. Castor and Pollux, the heads of Gemini the twins, are the most prominent, to the west-northwest. The summer sky is now just starting to come up at the beginning of the night. The bright star Vega in the constellation Lyra the harp is towards the east-northeast. In the southeast we have the constellation Scorpius the scorpion, with the bright star Antares. Further to the south we can also see the constellations of Centaurus and Lupus the wolf right along the horizon.
In July, the last of the winter constellations are now gone, and the spring constellations are beginning to head to the west. The summer constellations are now mostly up in the east. We can easily see all three stars in the Summer Triangle, Vega being the highest in the east-northeast, Deneb a little lower to the northeast, and Altair to the east. To the southeast we can see the Teapot of Sagittarius near the tail of Scorpius. Also, to the north-northeast we can see the W of Cassiopeia the queen.
Interesting Stars Visible in June and July (during observatory hours)
|Name / Designation||Apparent Magnitude
(lower = brighter)
|Regulus||1.36||77||means "Little King"|
|Alpheratz or Sirrah||2.07||97|
|Albireo||3.2 / 5.8 & 5.1||390 / 380||possibly a triple star system|
|Eta Cassiopeiae||3.5 / 7.4||19||480 yr orbit|
Mercury will be visible in the west after sunset for the first half of June. It will then pass between us and the Sun and emerge in the east before sunrise by the end of July.
Venus passes between us and the Sun at the beginning of June, but will be visible in the east before sunrise by the end of the month.
Mars rises early in the morning during June, moving through Aquarius and Pisces, and eventually coming up before midnight in July.
Jupiter rises earlier each night, and eventually comes up at sunset in mid July. It will be very prominent in the east in the constellation of Sagittarius.
Saturn comes up right after Jupiter in the constellation of Capricornus, also easy to spot.
|06/03/20||Venus at inferior conjunction. — Between Earth and the Sun.|
|06/04/20||Mercury at greatest eastern elongation. — Visible after sunset.|
|06/06/20||Peak of Daytime Arietids meteor shower.|
|06/12/20||Last Quarter Moon.|
|06/13/20||Appulse of Mars and Neptune. — Separated by 1.6°.|
|06/20/20||Earth at northern solstice. — Beginning of our Summer.|
|06/20/20||New Moon and Annular Solar Eclipse. — Not visible from Tucson.|
|06/28/20||First Quarter Moon.|
|06/30/20||Appulse of Jupiter and Pluto. — Separated by 0.7°.|
|06/30/20||Mercury at inferior conjunction. — Between Earth and the Sun.|
|07/04/20||Earth at aphelion. — Our farthest distance from the Sun.|
|07/04/20||Full Moon and Penumbral Lunar Eclipse.|
|07/05/20||Comet NEOWISE at predicted brightest.|
|07/12/20||Last Quarter Moon.|
|07/14/20||Jupiter at opposition. — Best time to see our largest planet.|
|07/15/20||Pluto at opposition. — Best time to look for this dwarf planet.|
|07/20/20||Saturn at opposition. — Best time to see this ringed planet.|
|07/22/20||Mercury at greatest western elongation. — Visible before sunrise.|
|07/27/20||First Quarter Moon.|
There are several open star clusters we can see this time of year. First, Coma Berenices (Bernice's Hair) is high in the west near the tail of Leo. Next, there is the Ptolemy cluster (M7) and the Butterfly (M6) in the southeast near the tail of Scorpius. Also nearby is the Wild Duck (M11) in the constellation of Scutum.
Now that the Milky Way is coming up, there are several globular clusters we can see. M3 is high in the west, in the constellation Boötes. Nearby, the famous Hercules Globular (M13) is high in the east. We also have M5 high in the south in the constellation of Serpens. Finally, for those with a clear horizon, the amazing Omega Centauri (C80) is visible low to the south.
For nebulae, we can see the Swan (M17), the Lagoon (M8), and the Trifid (M20) to the southeast in the constellation Sagittarius. The Eagle (M16) is nearby in the constellation of Serpens. The North America nebula is also in the northeast in Cygnus. For planetary nebulae, we have the Owl (M97) in Ursa Major high in the northwest. We also have the Dumbbell (M27) in the west-northwest in the constellation of Vulpecula and the Ring (M57) nearby in Lyra.
And now the galaxies: In Ursa Major to the northwest we have Bode's Galaxy (M81) and the Cigar Galaxy (M82), close enough to be seen together in a low-power telescope. Nearby in the constellation Canes Venatici we have the Whirlpool (M51), which is a pair of colliding galaxies. The Pinwheel Galaxy (M101) is also nearby near the handle of the Big Dipper. Then the Southern Pinwheel (M83) is to the southwest in the constellation Hydra. The Sombrero Galaxy (M104) is nearby in the constellation Virgo.
Interesting Deep Sky Objects to Observe during June and July (during observatory hours)
|Designation||Name||Apparent Magnitude||Apparent Size||Distance
|Messier 31||Andromeda Galaxy||3.4||3° x 1°||2,900,000||spiral galaxy|
|Messier 44||Beehive Cluster||3.7||95'||577||open cluster|
|Messier 3||(in Canes Venatici)||6.2||18'||34,000||globular cluster|
|Messier 27||Dumbbell Nebula||7.4||8' × 6'||1,250||planetary nebula|
|NGC 7009||Saturn Nebula||8||36"||2,400||planetary nebula|
|Messier 81||Bode's Galaxy||8.5||21'||12,000,000||spiral galaxy|
|NGC 3242||Ghost of Jupiter||8.6||25"||1,400||planetary nebula|
|Messier 57||Ring Nebula||8.8||1'||2,300||planetary nebula|
|Messier 82||Cigar Galaxy||9.5||14'||12,000,000||galaxy|
What is a dwarf planet? How many are there?
You probably know that Pluto used to be a planet, but now it is a dwarf planet. Even young kids ask about this a lot, despite the fact that they are not old enough to remember when Pluto was a planet! Well, nothing about Pluto itself changed, but merely the way that we classify objects in our solar system.
First, let's go back to the year 1800. At the time, there were seven known planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, and Uranus (although the name of Uranus was not fully settled for a few more decades). Then in 1801, Italian astronomer Giuseppe Piazzi discovered something between the orbits of Mars and Jupiter, which was designated a planet and named Ceres. This was followed by discovery of Pallas in 1802, Juno in 1804, and Vesta in 1807, bringing the number of planets up to 11. There was some debate at the time about whether these objects should be classified as planets or something else, since they were clearly different from the 7 previously known planets. Nevertheless, they retained their titles for a few more decades.
Then in the late 1840s, discoveries started taking off. Astraea in 1845, Neptune in 1846, and five more objects between Mars and Jupiter before 1850. Somewhere in this time span is when it became common to call these small objects asteroids or minor planets rather than planets. So the number of planets dropped back to 8 (the previous 7 plus Neptune), and asteroids became a new class to themselves. The rate of discovery has continued to increase ever since.
One more thing to mention before I move on: comets. Comet Halley was the first to have its orbit calculated in 1705 and confirmed in 1758. As far as I can tell, it was never called a planet, probably due to its very different appearance and very elliptical orbit. Only 4 more periodic comets were known before 1850: Encke in 1819, Biela in 1826, Faye in 1844, and Brorsen in 1846. And like the asteroids, their numbers have increased considerably since then.
Next we'll jump ahead to 1930. American astronomer Clyde Tombaugh discovers something moving out past Neptune. This object of course was Pluto. At the time, it was thought to be the size of Earth or larger, so it was immediately called a planet. Over the years, estimates of Pluto's size got revised down until it was much smaller than our Moon, yet it still retained its planetary status. Searches for other larger planets even farther out yielded no results, so our solar system sat happily at 9 planets for many decades.
Now we'll zoom forward to 1992. This was the year a second object was discovered past Neptune. This object, now known as Albion, is much smaller than Pluto, so didn't really pose a threat to Pluto's status. However, it was the first of many, and just like the asteroids, there proved to be an entire belt of material past Neptune, now called the Kuiper Belt. Finally, in 2005 Eris was discovered, which rivaled Pluto in size, and so it forced the question of where to draw the line between what is considered a planet and what is not.
So in 2006, the International Astronomical Union came up with 3 criteria that something has to meet to be called a planet: It has to orbit the Sun, it has to be big enough to be round by its own gravity, and it has to have cleared its orbit. Pluto meets the first two criteria, but not the third, and so it officially lost its planetary status. However, the IAU also came up with a "consolation prize" by calling it a dwarf planet. Besides Pluto, there are four other dwarf planets currently recognized: Ceres and Eris mentioned earlier, plus Haumea and Makemake also in the Kuiper Belt. There are several other candidates for dwarf planets, but their status hasn't been officially confirmed yet. Some scientists estimate that there could be hundreds of potential dwarf planets waiting to be classified or discovered.
There is still a search for one or more planets that may be lurking beyond the Kuiper Belt, so our planetary family may grow again, but we'll just have to wait and see.
If you have any questions you'd like me to answer in the next issue of SWG, please let me know. I'm also happy to take suggestions or comments, and also pictures if you'd like to send them. Happy viewing!
- Cornelius, Geoffrey. The Starlore Handbook: an Essential Guide to the Night Sky. San Francisco, CA: Chronicle, 1997. Print.
- Ottewell, Guy. Astronomical Calendar 2012. Raynham, Mass: Universal Workshop, 2011. Print.
- Ottewell, Guy. Astronomical Calendar 2013. Raynham, Mass: Universal Workshop, 2012. Print.
- Ottewell, Guy. The Astronomical Companion. 2nd ed. Raynham, Mass: Universal Workshop, 2010. Print.
- Astronomy Magazine. February 2013. Volume 41, No 2.
- Astronomy Magazine. February 2013. Volume 41, No 3.
- Sky & Telescope. February 2013. Volume 125, No 2.
- Sky & Telescope. March 2013. Volume 125, No 3.