Astral adventures

This month our Sky Guy, Dr. Rolly Chiasson, talks about Hydra.

Hi sky lovers.

It’s time for another look into our night sky and stories about it. Let’s focus on constellations this month. I am going to talk about Hydra, the largest constellation in the night sky.

First, just for review, a constellation is a large group of stars, or a fenced off segment of the night sky. Many people believe that constellations are groups of stars in the sky making up shapes. Not so. In the 19th century, astronomers met and divided up the total sky all around us into 88 constellations – or areas of the sky with defined but irregular boundaries or fences. These areas might or might not contain a shape familiar to us, such as the Big Dipper or the shape of Leo the Lion. Now to Hydra, AKA the Water Snake, the largest of the 88 constellations. First, how do we find it? It’s a very long constellation. It has a snake’s head of six stars just south of the constellation Cancer the Crab. It’s actually easier (and more fun) to look this up in a star map book, rather than find it in the sky at first.

It then stretches westward in a crooked line for greater than 50 degrees of our sky to end at its tail as we would expect. Along the way, it is associated with or borders on several other smaller constellations such as Corvus the Crow, Crater, Sextans and Antlia.

Within the constellation, we find a star V Hydrae, occasionally barely visible to the naked eye. Many astronomers refer to this as the reddest star in the sky. (By the way, I haven’t seen this one myself yet.) There’s a fun story about Hydra, called “Forgotten Cat.” In the 18th century, the astronomer Le Francais de Lalonde in his Astronomie, placed a cat Felis just beneath one of Hydra’s coils, explaining that he was very fond of cats. Felis has, of course, subsequently disappeared from our modern sky charts. In mythology, Hydra, who was very evil, was slain by Hercules. It had many heads and every time one was cut off three new ones grew. You will have to read yourself to see how he finally succeeded. So much for mythology.

Although none of the stars in Hydra are very bright, if you want to look for it, first of all, have a sky map, and then using the sky map, at this time of year, look low in the sky all the way from south southeast to the west southwest. That is a lot of sky. If I write anything more about Hydra, I will go snaky.

So, what is in the sky for us this month?

As usual let’s start with our night sky. It’s a good month. Jupiter is the planet to concentrate on this month. It reaches opposition on May 8. That means that it is opposite the sun in our sky, and thus is “up” or visible on that date, but really for several days around it, from dusk to dawn. Around these dates, Jupiter will be low in the southeast as twilight deepens and will set in the southwest at sunrise.

As the month passes, it will both rise and set earlier. If you are up for a challenge, try to see Jupiter’s Galilean moons. Jupiter has many moons but the Galileans are four in number, the closest four to the planet, and in binoculars, are like tiny diamonds in a little “solar system” of its own around Jupiter. (Of course they are not really a solar system, as they circle Jupiter. We will call them a Jovian System)

There will usually be two to four visible each night as they circle the planet. You can see what ones are visible each night all month by looking in the May issue of the magazine “Astron- omy,” which on page 41, gives you a map for the moons for each night. So – Io, Europa, Callisto, Ganymede. Let’s try and see them.

Still in the night sky, the other brilliant planet is Venus. We can see Venus in the western sky shortly after sunset. It’s relatively low in the sky and doesn’t get much higher all month, but it is brilliant.

Now for the morning, or really midnight to dawn.

We start with Saturn, which at the beginning of the month, rises just after midnight, in the east, of course. It is interesting that as Jupiter reaches opposition May 8, so Saturn reaches opposition on June 27. Mars, which we will discuss next, then reaches its opposition this year on July 27. Three months in a row with great oppositions. How wonderful.

Now Mars is special this year. It has been visible since January but it has been increasing dramatically in brightness throughout these months and this is because it is actually approaching us. On July 31 it is at its closest to us in 15 years, but more on that to come. Mars, at month’s beginning, rises in the eastsoutheast at about 1:30 in the early morning, and by month’s end, just after midnight.

In the morning, Mercury at the beginning of the month, rises in the east-southeast, very low, at about 30 minutes before sunrise. Then, interestingly, over the next two weeks, it goes lower, but gets brighter. Finally, the new moon is May 15 and the full moon is May 29.

Well that is it again folks. See you next month.