Heads UP! for October: So many planets seem to have stage fright this month. Mercury and Jupiter are hiding in the sun’s glare, Saturn is low in the southwest, Venus is low in the dawn sky, but still dazzling, even near its dimmest. Mars is very dim as it climbs past Venus, both across the solar system from us.
Use a Solar Observatory for Watching Planets!
The hidden planets can be found using the Solar Heliographic Observatory (SOHO) as they appear to trespass into the most intense solar glare. Mercury will pass through SOHO LASCO C3 instrument from right to left during almost all of October, and be caught by the narrower view of LASCO C2 for a few days from the 6th through the 11th.
10/3/2017 view from SOHO C3. Mercury to the right of the Sun (which is blocked; the sun is the size of the white circle).
Sun, Mercury and morning planets as seen from Earth 10/3. Via NASA Solar System Simulator. Extra Credit: Can you pick out the asteroid Vesta in the C3 image? Using the animated GIF may help as Vesta (and Mercury) move against the background stars.
Jupiter nearly passes behind the sun from our point of view. It’s visible after midmonth in the C3 (October 16th through November 5th) and in the C2 from the 24th through the 28th. Spica takes Regulus’ place as the bright star in the C3 field this month.
Comet P96 Machhotz is streaming into the inner solar system, reaching perihelion by Oct 27 passing inside the orbit of Mercury. It get as bright as magnitude +2, but it (too!) will be in the Sun’s glare from Earth’s point of view. Use the SOHO C3 to see it sweep through from bottom to top of C3 field October 25th through 30th. For nighttime observers, there is a well-placed comet in the northern skies. C/2017 O1 was discovered in photos from July 19th taken for the All-Sky Automated Survey for Supernovae (ASASSN) program. O1 is forecast to brighten perhaps +6 or 7 as it passes perihelion beyond the orbit of Mars in October. O1 is up all night, but highest in the morning as it moves from between Perseus and Auriga into the Camel (Camelopardalis). Its green color is from diatomic carbon and may be visible in telescopes. It’s even more likely to show up in time exposures.
What’s a bright object fan to do?
Stay inside and watch the SOHO feed? Look for Saturn, sliding into the haze and fog in the southwestern sky. It sets before 9pm by the end of the month. The Moon comes by to provide consolation on the 22nd and 23. Consider that the earlier darkness and lingering warmth makes October a good month to show off the brighter stars and Saturn to crowds of people, so all is not lost.
Saturn’s rings are still tilted wide open at 27 degrees, the largest for 2017. Titan makes two trips around Saturn each month. Iapetus is not as bright as Titan, but still visible in most telescopes. It’s brightest when it is furthest west of the planet, around mid-month. It’s nice to see another place in our Solar System where humans have left our marks, thanks to the Cassini/Huygens mission.
Venus, Tiny, but Bright!
Venus is trying to hold on to its place in the pre-dawn sky, rising less than two hours before sunrise. It’s a not-quite-round blob in the telescope, 90 percent illuminated this month, while shrinking in size. Mars and Venus are less than the apparent size of the Moon apart on the morning of the 4th. Mars is less than half the apparent size of Venus, because it ‘s a bit smaller and further away; and much dimmer at magnitude plus 1.8 vs. Venus’ minus 3.9. The Moon joins the morning party on the 17th and 18th.
The Moon takes its revenge on Regulus for photobombing the total solar eclipse by eclipsing Regulus in the dawn sky on the 15th. Regulus will disappear behind the Sunlit crescent about 544am and reappear on the Earthlit edge about 643am. Sunrise is 707am.
Dark Mornings Late!
Early risers, we can use daylight time to our advantage. The latest sunrise of the year, according to clock time, occurs in the last week of the month. Even earlier risers at 4am will get to see Orion standing up high in the southern sky. Orionid meteors are an early morning bonus with up to 10 more meteors an hour than usual on the 21st and a day before and after. Orionids are some of the fastest meteors of the year. A few Taurid meteors may show up in advance of their November peak. You can tell Taurids from the Orionids, since most Taurids are bright and slower moving.
Space Station Stats
The International Space Station is an evening object through the 18th and a morning object starting on the 29th. Check for the latest updates on the orbit of the Air Force space plane. Based on its present orbit, visible overflights are likely in the evening sky. At 400km altitude, the X-37B could be seen crossing our skies at magnitude +1 or 2.