Astro Bob: See 2 space stations at dusk — ISS and Tiangong
China recently added on to their Tiangong space station making it brighter and easier to see. Check it out this week.
DULUTH — I recently posted about seeing the International Space Station at dusk. I hope you've had a chance to spot this brilliant, moving "star" gliding silently across the night sky. The station's evening "rounds" finish up for most northern hemisphere locations later this week before it returns to the morning sky at mid-month. For the next few nights, the Chinese Tiangong space station will share the sky with the ISS, crossing from west to east during evening twilight through about mid-December.
Less than a year ago, Tiangong consisted of the single Tianhe module, but this past July and October, China's space agency launched two additional modules: Wentian (Quest for the Heavens) and Mengtian (Dreaming of the Heavens). Both are laboratory cabin units for conducting scientific experiments in space. Together with Tianhe they now complete the Chinese effort to build a permanent human outpost in Earth orbit.
Tiangong shines more brightly than a year ago because it's bigger. Bigger means it has more surface area to reflect sunlight (reflection is the source of a satellite's illumination). During favorable passes, the Chinese space station can reach magnitude -2, similar to Jupiter in brightness.
The International Space Station is considerably larger than Tiangong and can shine up to two magnitudes brighter. Its orbit is also more steeply inclined, providing plenty of high, bright passes for observers across the much of the populated world, including the northern U.S. and Canada.
Tiangong orbit is not as steeply tilted as that of the ISS — 42° versus 51° — so it's neither as bright nor climbs as high during its nightly passes for skywatchers living in more northerly mid-latitudes like Canada or northern Minnesota. But it's still much brighter than it used to be and easily visible if you know where to look.
On a good pass from Duluth, Minnesota, it can glow brighter than Vega, the brightest star in the Summer Triangle. That's a great improvement over the old, "one-module" days when the best it could do was magnitude 2, as bright as the Big Dipper stars.
To find out when and where to see either Tiangong (or the ISS), go to heavens-above.com and select your city by clicking on the blue Change your observing location and other settings link. Then return to the home page and click on the blue Tiangong link to pop up a table of passes that includes time, direction, brightness and altitude. Ten degrees (10°) of altitude is equal to one fist held at arm's length against the sky.
The bigger the negative number in the brightness column the brighter the pass. The bigger the positive number the fainter its appearance. Click on any pass time and a map will appear showing the station's path across the sky. All times shown are local times on the 24-hour clock for your location, so 18:30 = 6:30 p.m. local time and 2:15 = 2:15 a.m.
You can also use astroviewer.net for a list of passes, times and directions to look for both the ISS and Tiangong. While the site doesn't provide maps it's extremely easy to use. Just key in your city's name (or the nearest larger city) and hit enter. The link above will take you to Tiangong. For an ISS list, click on the white Observation ISS link while you're there.
China recently launched a crew of three taikonauts (from the Chinese word "taikong," meaning space or cosmos) to the Tiangong space station. Arriving on Nov. 29, they joined an earlier crew of three astronauts, marking the first time six taikonauts have been in orbit at the same time. That group is set to return to Earth soon, with the new crew remaining aboard the station for six months. They'll stay busy with more than 100 science experiments and perform several spacewalks.
With six astronauts onboard Tiangong and 10 on the ISS, there are currently 16 people in orbit, enough for a soccer team and then some!