September’s a swell month for increasing the magnification of our Solar System’s residents. Jupiter, Venus and Mars swell to larger sizes and Comet ISON might get in range of larger telescopes. Even a star in our Milky Way swelled up so much it got a new name: Nova Delphinus 2013.
Venus is magnitude minus 4.1 and still stunning after sunset, if the trees don’t get in the way. Venus is our sister planet, if you ignore the sulfuric acid cloud layers and surface temperature of 800 plus degrees and a surface pressure of 90 Earth atmospheres. But Venus is getting larger this month as it comes nearer the Earth, running away with the title of closest planet to Earth until Mercury sneaks closer at the end of October. Telescopes show a slightly more than half-lit Venus, best seen with a telescope while the sky is still bright.
Mercury slips over to the evening side of the Sun, but is even lower in the sky than Venus. They are easier to see from Earth’s Southern Hemisphere. Both Venus and Mercury appear to move to the left, parallel to the horizon, during this month. Saturn takes a more direct approach and appears to dive to the horizon. Saturn will still be a fun object at star parties in September and October, but it’s getting low for sharp viewing.
Once it gets dark, the Milky Way bisects the sky, with our guest star, Nova Delphinus 2013 overhead. Even with the constellation Sagitta (the Arrow!) pointing in its direction to help me find it, above the dim dolphin (Delphinus), I couldn’t tell which star was the nova. (I get lost a lot in the Milky Way- so many stars, so little time to get to know them all!) Nova Del (as his friends call him) peaked about 5th magnitude and was dropping through magnitude 6 as of late August.
Whether you have your own telescope or not, you can use some unlikely telescopes to see what you can’t see from our ground-based scopes. Mercury is completing a pass behind the Sun, visible as a bright dot in the SOHO C3 solar telescope. Other dots in SOHO’s view include stars, perhaps an asteroid or two; and if you look carefully, somedays you can see a small comet making a one-way trip to evaporate in the Sun’s atmosphere.
Curiosity, the latest Mars rover, snapped a shot of a Martian moon, Phobos, crossing the Sun, while using other cameras to photograph the change in brightness on the ground caused by this Phobean partial eclipse of the Sun. Go to the Planetary Society’s blog and scroll to “A special Phobos eclipse” to see the action.
If all goes well, on September 6th at 11:27pm, the Wallops Island spaceport on the DEMARVA peninsula will launch LADEE, a probe to sample the incredibly thin atmosphere of our moon. We’ll be able, if no clouds get in our way, to see parts of its powered flight into space. When have you seen, with your own eyes, a spacecraft launching to the Moon? (You lucky folks who saw an Apollo/Saturn V launch at the Kennedy Space Center put your hands down, now.) Find their web site in case of any delays due to weather or mechanical problems.
As Comet ISON heads into the inner solar system, it will appear near Mars in our morning skies during late September. It’s likely to be very dim, an object for larger telescopes. But this is a wonderful situation where the comet will not just look like it’s near Mars from our point of view, but will actually be passing over Mars’ north pole on October 1st. C/2012 S1 (ISON) (its full name) will pass about 6 million miles away from Mars on its way in to the inner solar system. But, wait, that close pass will be bested by Comet C/2013 A1 (Sidding Spring) when it passes about 80,000 miles from Mars on October 19th, 2014. A number of our satellites in orbit around Mars and the two existing Mars rovers will become astronomers, tasked with getting data to help us learn more about how these comets evolve as they get closer to our Sun. It’s hard to tell how bright ISON will become, since the Sun has been blocking our observations until recently.
The Moon starts and ends the month between Jupiter and Mars in the morning sky. On the 8th, it will almost run over Venus – a great scene that binoculars make spectacular. The International Space Station is visible before sunrise after the 12th, a bonus while you check out Jupiter and its moons. Mars stands out in front of the faint star cluster, the Beehive, on the 8th and 9th. Use binoculars to get the whole scene.
Phobos eclipse: http://www.planetary.org/blogs/emily-lakdawalla/2013/08201724-a-special-phobos-eclipse.html
Instructions for viewing the launch from the eastern United States:
Link to brightness curve for Nova Delphinus: http://www.aavso.org/nova-del-2013