plan­ets on dis­play

Uranus reaches op­po­si­tion, mak­ing it a great tar­get

All About Space - - Contents -

Rather bizarrely, it could be said that Uranus is ‘dom­i­nat­ing’ the evening sky this month. How could that pos­si­bly be? Af­ter all, the planet’s low mag­ni­tude of 5.7 means that tech­ni­cally it is a naked-eye ob­ject, but in re­al­ity it is only vis­i­ble with the as­sis­tance of a pair of binoc­u­lars or a tele­scope to ob­servers with al­most-per­fect eye­sight look­ing for it from a dark­sky lo­ca­tion with­out any in­ter­fer­ence from the light pol­lu­tion caused by ar­ti­fi­cial lights, or from the bright glow of the Moon.

Even un­der those per­fect con­di­tions the planet’s low mag­ni­tude means that it does not stand out from the other stars around it; to iden­tify which of the many dots in the sky Uranus is, an ob­server needs to know the planet’s po­si­tion rel­a­tive to all those back­ground stars very, very ac­cu­rately.

That will re­quire the use of a de­tailed star chart, ei­ther gen­er­ated by an app on a phone or tablet, an as­tron­omy web­site or a com­puter plan­e­tar­ium pro­gram such as Stel­lar­ium.

Then, when you’ve pinned down which part of the sky it is in, if you want to see Uranus it­self you will need to scan the sky us­ing a pair of binoc­u­lars or a small tele­scope to make the planet stand out more clearly. Through a pair of binoc­u­lars Uranus is given away by its colour alone – it ap­pears as a green-white ‘star’ sur­rounded by less colour­ful, but bril­liant, white or blue-white stars.

Through a small tele­scope Uranus will stand out from the ce­les­tial crowd more ob­vi­ously be­cause it will look like a tiny, pale-green disc in­stead of a sharp point of light. Higher mag­ni­fi­ca­tions make the disc larger, but will also en­hance its sub­tle colour. If you’re the owner of a 12” or larger tele­scope Uranus will look a lot like a plan­e­tary neb­ula, mi­nus the cen­tral star of course.

If Uranus is so unim­pres­sive, why bother look­ing for it in the first place? Be­cause – as with so many things in the night sky – the ap­peal of look­ing at Uranus isn’t its ac­tual ap­pear­ance in your eye­piece, but know­ing and ap­pre­ci­at­ing what it is you’re look­ing at. The good news is that this month you’ll have plenty of time to track it down on the next clear night be­cause it is vis­i­ble right through the night, from dusk un­til dawn. As the sky dark­ens af­ter sun­set you’ll find Uranus over in the east, al­ready quite high, shin­ing just in­side the south­ern bor­der of Aries. It will then be car­ried from east to west through the evening, and by the time the west­ern sky is start­ing to brighten with the ap­proach of dawn it will be low in the west.

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