Uranus queues for the opposition – Sky & Telescope

They may both be blue, but Uranus’ diameter is four times that of Earth and has the coldest atmosphere in the solar system, with temperatures ranging from –243 ° F (–153 ° C) to –370 ° F (–223 ° C). Carbon rings made up of water ice and organic matter encircle the planet. The two hemispheres are shown here on July 11 and 12, 2004, at several near infrared wavelengths converted to blue, green and red. The north pole of the planet is at 4 o’clock.
Lawrence Sromovsky, University of Wisconsin-Madison / WW Keck Observatory / Image of Earth from NASA

On the night of November 4-5, Uranus clashes in a lonely corner of the sky just north of Cetus in Aries. On this date, Earth and the seventh planet pair on the same side of the Sun and are closest for the year. Close is a relative term in astronomy: Uranus will stand 2.8 billion kilometers from Earth in opposition.

To feel the enormity of this distance, let’s get in the car for a ride. Traveling at a highway speed of 80 miles per hour (approximately 130 km / h) and never stopping to go to the bathroom, we would be there in about 2,550 years. Taking a plane speeds up our arrival but not by much, with a one-way ticket of 380 years. Travel is untenable, so we’ll stick to binoculars and telescopes instead.

Point and fetch

At the end of October, the planet rises to about 20 ° high in the eastern sky at 8:30 p.m. DST. It changes to 7:30 p.m. when we return to standard time on November 7th. Fortunately, the Moon won’t interfere until around November 9, so for the next two weeks you’ll have the opportunity to spot Uranus without optical aid.

Uranus wide-field research map
Begin your journey to Uranus by facing east and finding 4th magnitude Mu (μ) Ceti; then follow the Y-shaped asterism to guide you to the planet. Use the more detailed map below, if necessary.

At a magnitude of 5.7, it won’t be difficult in a rural sky. The key to finding the planet is to connect it in a pattern with other nearby stars. The map on the left shows its relation to Mu (μ) Ceti and the 38 stars Arietis, Sigma (σ) Arietis and Omicron (ο) Arietis, which form a “Y”. Uranus is located just west of this asterism. Be sure to watch about rather than directly To the planet. This aligns the most sensitive part of your retina at night with your target in a ploy called diverted vision.

With binoculars, Uranus is child’s play. You just have to know where to point. The planet slowly crawls west in a retrograde motion for the remainder of the year. Covering just 2.3 ° from Oct. 27 to Dec. 31 – barely half a typical binocular field of view – makes tracking easier.

Detailed Uranus Search Map
This map shows Uranus’ path through early 2022 with magnitude 8 stars, as well as the asterism “Y”.
Megastar with permission

It is only in a telescope that Uranus reveals its true nature as a planet, displaying a small disc 3.7 arc seconds wide with magnifications of 100 × and above. Just in case you need more proof of the remoteness of the planet, Uranus is four times the diameter of Earth but only appears twice the apparent size of Jupiter’s moon, Ganymede. Like Neptune, most observers report that the planet appears blue-green, a color due to methane gas in its predominantly hydrogen-helium atmosphere. I only see the lightest blue color when using magnifications of 245x and above.

Uranus in the near infrared
Damian Peach captured a remarkable amount of detail about Uranus using a near infrared filter and a C-14 telescope on October 7-8, 2015.

How can you contribute

I have never seen any disc detail, but other hobbyists report shading differences between the equatorial and polar regions using instruments 8 inches and larger and magnifications north of 300 ×. Seeing must be almost perfect to distinguish such subtle things. Photographically, hobbyists with telescopes 12 inches and larger have clearly recorded polar hoods and bright equatorial belts using near-infrared filters such as the Baader IR685.

In addition to near infrared photography, Richard Schmude, Distant Planets Coordinator with the Association of Lunar & Planetary Observers (ALPO), encourages observers to collect Uranus luminosity measurements using a camera astronomical and a low magnification green filter to include a star field for comparison.

“Another project that hobbyists can participate in is collecting luminosity measurements of Uranus’ four brightest moons,” Schmude said. “It’s well within the range of a 10 inch telescope and CCD camera. They can show variability due to rotation and secondly, they can show brightness or color change as their orientation changes.” You can send your observations to the Distant Planets section of ALPO (click on the link on the left) and to the British Astronomical Association (BAA).

Rings and seasons of Uranus
Uranus’ lateral rotation leads to extreme seasons. In summer, for example, the northern hemisphere of the planet experiences 21 years of continuous sunshine.
NASA / ESA / M. Showalter (SETI Institute)

While most of us will see an unremarkable disc, there is a way to perceive the unbalanced rotation of the planet, caused by its axis tilted at 98 °. Uranus spins sideways like an overturned top. Since the planet’s moons are coplanar with the equator, they do not sway from side to side like Jupiter’s brightest moons do, but rather revolve around the planet.

This video of an imaginary journey to the heart of the planet is strangely fascinating. The “descent” begins two minutes later.
V101 Science

Two of the planet’s 27 known moons are visible in telescopes 10 inches and larger – Titania at magnitude 13.9 and Oberon at 14.1. Look for them at the time of maximum elongation, when their separations with Uranus are around 30 and 40, respectively. I see both faintly with deflected vision in my 15 inch reflector at 245 ×, but 429 × gives a much better view. Sky and TelescopeThe Uranus Moons observation tool will help you find them.

As the weather cools and the sun sinks lower and lower, rest assured. It is much worse in Uranus, where our star is little more than a point of a blinding brilliance barely resolvable with the naked eye and much more miserly of its gifts. Let these cold facts motivate you to visit the planet the next clear night.

Comet 29P is rock’n’roll!

29P / SW evolution September October 2021
Eight images show the evolution of comet 29P / Schwassmann-Wachmann from its explosion in late September until its second eruption this month.
Eliot Herman

At the end of September, we reported on one of the brightest 29P / Schwassmann-Wachmann explosions in recent years. Richard Miles of the BAA considers this to be “the most energetic of the past 40 years”. At the top, this bomb from a comet became as bright as 10th magnitude with a distinct disc-shaped coma and a dense, shiny core. Miles postulates that the comet’s violent explosions are fueled by liquid hydrocarbons that rise to the surface through cracks and explode as cryovolcanoes. The dissolved gases expand rapidly and propel encrusted dust into space to create a rapidly expanding coma.

Just when it looked like 29P was “on the way out”, her coma becoming more and more transparent, a new explosion of about 2.5 magnitude occurred on October 23 and brought her back to life. comet to life. Now that we’ve entered a moonless spell, please take a look. A 10-inch telescope should still show this fiery 60-kilometer-wide ball of ice as a small fuzzy disc near the star Iota (ι) Aurigae. It appeared diffuse through my 15 inches on October 27.1 UT with a coma diameter of 2 ′ and a magnitude of about 11. Click here for a map.

Turn on your zodiacal light

Zodiacal light at dawn in October
The beautiful lenticular shape of the zodiacal light stretches from the southeast horizon of Virgo almost to the meridian of October 18, 2021. It is formed of dust particles – mostly located between Earth and Mars along the plane ecliptic – which backscatter sunlight.
Bob the king

Fall mornings just before the onset of dawn are perfect for seeking out the largest entity that is regularly visible to the naked eye in the solar system – the zodiacal light. I got up twice earlier this month and traced the huge cone of interplanetary twilight from near the horizon across 75 ° of the sky to where it gently brushed against the Milky Way. winter. New research indicates that its true source – long thought to be dust shaken by comets and released in asteroid collisions – may actually be Martian dust.

What remains unknown is the mechanism underway to continuously remove material and propel it to exhaust speed. No matter. Just enjoy the prettiest, grainy, and elegant view in the sky. Your best viewing time begins about an hour before and until early dawn during the moonless window from November 3 to 17. Premium! Stay until the early morning hours of November 3 and you will see an amazing conjunction of the Old Moon and Mercury.

Visit our Uranus and Neptune webpage to learn more about the Ice Giants and for additional maps. Receive the November issue of Sky and Telescope for more fun observing tips on Uranus’ opposition and other events.


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