Spring Equinox 2016

Today is the first day of spring in the northern hemisphere! At 0430UT (GMT) this morning, 20 March 2016, the Earth’s axis of rotation went momentarily side-on to the Sun. For the past six months the Earth’s northern hemisphere has be angled away from the Sun, and now we’re angled towards it. Lots more info about equinoxes and equiluxes in a previous post.

As most people take delight in the lengthening daylight hours spare a thought for the amateur astronomers who, in a few weeks time, will be packing away their scopes for the summer, eagerly waiting for the darkening nights later in the year.

Constellation of the Month: Leo the Lion

Head outside during April just as the sky gets properly dark and sitting high in the south is the constellation of Leo the Lion.

Leo is well-known as it’s one of the signs of the zodiac, and therefore one of the constellations through which the planets, Sun and Moon pass over the course of the year.

Leo is also well-known due to its most prominent feature, a pattern of stars within the constellation (called an asterism) known as The Sickle, which looks like a backwards question mark, with the bright star Regulus as the dot.

Regulus is known as the king star, and is one of the brightest stars in the sky, shining blue-white in late winter and spring.

Within the constellation of Leo are two groups of galaxies, marked as 1 and 2 on the chart above.

1. The Leo Triplet: M65, M66, and NGC3628

2. The M96 Group: Including M95 & M96

Any of these galaxies can be seen with even a small telescope, but their detailed structure can only really be seen in larger scopes.

Enjoy the spring skies, and happy galaxy hunting!

Maps and descriptions like this one for each of the 88 constellations can be found in my new book, Stargazing for Dummies. Click on the image on the right for more info.

Spring Equinox 2012

Today is the first day of spring in the northern hemisphere! At 0514UT (GMT) this morning, 20 March 2012, the Earth’s axis of rotation went momentarily side-on to the Sun. For the past six months the Earth’s northern hemisphere has be angled away from the Sun, and now we’re angled towards it. Lot’s more info about equinoxes and equiluxes in a previous post.

As most people take delight in the lengthening daylight hours spare a thought for the amateur astronomers who, in a few weeks time, will be packing away their scopes for the summer, eagerly waiting for the darkening nights later in the year.

Happy Spring Equilux 2012

Today, Saturday 17 March 2012,  it is the Spring Equilux throughout the UK (and possibly elsewhere too*) meaning that there are almost exactly 12 hours between sunrise and sunset.

Sunrise

This date differs from the Spring, or Vernal, Equinox (2321 GMT on Sunday 20 March 2011) for a variety of reasons, which I explain in a previous post but here is a list of sunrise / sunset times for a variety of towns and cities throughout the UK:

Town / City	Sunrise	Sunset
Aberdeen	0617	1817
Glasgow	0626	1825
Belfast	0633	1832
Newcastle	0615	1815
Manchester	0618	1817
Birmingham	0617	1816
Cardiff	0621	1821
London	0610	1810

As you can see the time between sunrise and sunset is not exactly 12 hours everywhere but this is the day of the year when that is closest to being true everywhere*. Yesterday the sun rose a couple of minutes later and set a couple of minutes earlier, and tomorrow the sun will rise a couple of minutes earlier and set a couple of minutes later, as the days lengthen.

Also, the reason that sunrise and sunset does not occur at the same time everywhere* is due mainly to the longitude of the town, the further east a town is the earlier it sees the sun in the morning, and the earlier it loses it again at night.

So happy Equilux everyone*!

* interestingly, the equilux does not occur on the same same day for everyone, it depends on your latitude. The closer you are to the equator the earlier the date of your equilux. For example the equilux in most US cities occurred yesterday, 16 March, and in cities near the equator there is never a day with exactly twelve hours between sunrise and sunset! Take Quito, the capital city of Ecuador (latitude 0 degrees 14 minutes south) for instance. The length of day there only ever varies between 12 hours and 6 minutes long and 12 hours and 8 minutes long!

The Stars of Spring

As winter fades and spring arrives the stars in our evening sky change and new stars, not seen over the winter, make a reappearance.

Two of those stars are Arcturus, in the constellation of Bootes, and Spica, in Virgo, both of which will become early evening objects in April (in early March Spica doesn’t rise until 2130, three hours after sunset).

Spica, or the “ear of wheat” is held by Virgo the Virgin, and its presence in the evening sky has long been used by ancient astronomers as an indication that spring is coming.

Stars of Spring

To find these stars start with the curved handle of the Plough and continue that arc down to Arcturus. Spica is the same distance again beyond Arcturus. You can use the common mnemonic: “Arc to Arcturus and spike down to Spica”.

These stars should be easy to spot as they’re very bright, Arcturus being the fourth brightest star in the night sky at -0.04 magnitude (only Sirius, Canopus and Alpha Centauri are brighter, and only one of these – Sirius – is visible from the UK), and Spica is the 15th brightest at +1.04 magnitude.

Arcturus is so bright for two reasons: (1) is it intrinsically quite bright, being an orange giant star (the Sun would fit inside Arcturus 17000 times), and (2) it is quite close to us, being only 37 light years away.

Spica, by comparison, is intrinsically even brighter (it too is a giant star, but it is a super-hot blue-white giant compared to the rather cooler orange Arcturus), but it is a little smaller (“only” 400 Suns would fill it) and much further away, around 260 light years distant.