Monthly Night Sky Report: April 2021 and the H-R Diagram

    March proved to be a difficult month for stargazing over Utah.  There were a few clear nights, but unfortunately, these took place during the week instead of the weekend, so I was unable to take any pictures.  In the early evening hours after sunset, I was able to easily see Orion, the Pleiades, Taurus, Mars, and Antares.  I was also able to see bright Jupiter in the morning rising above the mountains, and by knowing Jupiter's location, I could find Saturn, which was much dimmer.  The morning hours before sunrise also offered views of the Big Dipper and from this constellation, I could find Arcturus and Spica.  

    April usually brings warmer weather and hopefully more nights with clear skies for those in Utah, although the region could surely use more precipitation.  Astronomically, April will bring the return of the Lyrid Meteor Shower, ending a two month meteor shower drought.  Unfortunately,  a 79% lit Moon will be in the sky on the night this shower peaks, however, the Moon will sink below the horizon shortly after 4 in the morning, creating a small window to catch some meteors before sunrise.  Mars will continue to be visible after sunset with Jupiter and Saturn becoming visible in the early morning hours before sunrise. 

             

Mercury

   Mercury will be challenge again this month due to its lack of brightness and how close it is to the Sun.  Your best chance of spotting the innermost planet will be towards the end of the month when it will sink below the western horizon shortly after the Sun.  Venus will shine more brightly than Mercury and you may be able to use this to your advantage when viewing the tiny world.  Mercury will be closer to the horizon than Venus until the 24th, at which time both planets will be at nearly the same altitude.  As the last day of the month approaches, Mercury will be found higher in the sky and further from the Sun, increasing your chances of spotting it.  During these last days, look above Venus to find Mercury.    

  

Venus

  Venus returns to view this month, but not until after mid month.  On the 24th, Venus and Mercury can be found at about the same altitude just after sunset, with Venus being much easier to spot due to its clouds reflecting most of the light from the Sun.  As mentioned earlier, you can use the brightness of Venus to help locate Mercury, especially after the 24th as Mercury climbs higher in the sky faster than Venus.      

    

Mars

    Mars will continue to be visible as soon as the Suns evening glow fades from the sky.  The red planet will form a triangle with the red stars Aldebaran in Taurus and Betelgeuse in Orion.  This triangle will change shape each night as Mars continues to move eastward (towards Betelgeuse) against the background stars.  If you are having a hard time differentiating between the two stars and Mars, remember that stars twinkle and planets do not.  Mars continues to move away from the Earth leaving telescopic views less than satisfying.  The Moon will be found less than 1° from Mars on the 17th this month.              

Jupiter

Saturn

    Jupiter will continue to be found in the morning sky before sunrise.  Each passing morning will find this gas giant rising earlier.  It's still too cold for many observers to take their gear out early in the morning to view this planet.  For those anxious to view Jupiter, it will reach opposition later this year, giving observers the chance they are waiting for!  

    Saturn will continue to rise before the Sun and Jupiter throughout the month.  Many anxious observers can't wait to use their telescope to view the rings (myself included!) but like Jupiter, the ringed world will reach opposition later this year, giving observers the view they desire.  The Moon will be found close to Saturn on the 6th and closer to Jupiter the following morning.  

   

Neptune

Uranus

    The outer two planets are best viewed through a telescope but can still be seen through a pair of binoculars.  Uranus will be found closer to the western horizon than Mars, as it leads the planets along the ecliptic through April.  The closest of the ice giants will be a hard target this month as it lies close to the horizon after sunset, causing the glow of the freshly set Sun to obscure it.  As the month continues on, Uranus will move closer to the Sun, reaching conjunction on the 30th.  

    Neptune will be an extremely hard target this month as it recently reached superior conjunction with the Sun.  This most distant world will return to our morning sky towards the end of the month, but will likely be too close to the Sun to spot it.  Neptune will be a better target later this year for those anxious to view it.     

Meteor Shower

   As mentioned in the introduction, we finally have a meteor shower to look forward to this month!  The Lyrids will appear to radiate from the constellation of Lyra on the morning of the 22nd.  A 79% lit Moon will light up the sky until about 4:30 in the morning, so if you are interested in viewing this shower, I would recommend doing so after 4:30 until the Sun rises.  At this time, Lyra can be found nearly overhead.  If you are unsure where Lyra is, look for the bright star Vega which makes up part of this constellation.  You should expect to see up to 20 meteors per hour during the peak date, with less meteors visible leading up to and after this date.    

Spot Me....🕵️  

    I've had you try to spot quite a few different objects in the night sky, most of which require a telescope. April will bring some warmer weather and will hopefully find more observers outside.  As it might still be a little too cold for some to stay outdoors for an extended period of time, I will suggest targets that are quick and easy to view.  For observers interested in evening sky targets, I urge them to look at the Pleiades before they sink below the western horizon and are lost from view until the coming winter.  I recommend using a low power eyepiece or a pair of binoculars on this target so that more of the stars can be seen.  A sky free of light pollution will also be helpful.  I encourage the astronomers that are able to get away from light pollution to look at the winter Milky Way band, which is often neglected due to the colder weather.  It can be found in the southwest sky (by Sirius) and arches over the western horizon to the north through Cassiopeia.  If using a wide field of view eyepiece, scan the Milky Way band for its many different sources of eye candy, including star clusters and nebulae.  

    

    For the early risers or those that stay up until sunrise, look for Antares in the southern sky which marks the right side of the summer Milky Way band that we are used to seeing.  You should also look east before sunrise to catch a glimpse of bright Jupiter and the less bright Saturn to the upper right.  If weather conditions are favorable, you should also be able to see Delphinus the Dolphin high in the eastern sky.                

  

    As always, leave a comment to let us know what you see!

Monthly Breakdown

    April 04:  Last Quarter Moon 🌗

    April 06:  Moon passes within 4° of Saturn

    April 07:  Moon passes within 4°  of Jupiter

    April 09:  Moon passes within 4° of Neptune

    April 11:  New Moon 🌑

    April 13:  Moon passes within 2° of Uranus

    April 17:  Moon passes within 0.1° of Mars

    April 18:  Mercury reaches superior conjunction

    April 20:  First Quarter Moon 🌓

    April 22:  Lyrid Meteor Shower Peaks

    April 26:  Full Moon 🌕 

    April 30:  Uranus and Sun conjunction

    

Think About This....💡

   

    Unfortunately, I was once again thwarted by the weather and my schedule to make and attempt at taking more pictures to share.  I hope that April will be more fruitful for me and others that have been waiting for nicer weather.  

    As the weather warms up, many of us will be spending more time outdoors.  Hopefully this time spent outdoors can be used to glance upwards at the wonders above.  In past posts, I have briefly discussed the difference between the stars and their appearance.  This month, I would like to go into a little more detail.  

    Stars come in different colors and sizes, with our Sun being an average yellow star.  The hotter the star, the bluer it will appear, such as Vega and Sirius, while cooler stars appear red, like Betelgeuse and Antares.  The hottest and bluest stars are classified as O-stars, followed by B, A, F, G, K, and finally M-stars which are red and cooler.  This might be hard to remember since humans label cold things with blue and hot items with red.  The mnemonic I learned to remember the star classifications was, "Oh Be A Fine Girl (or Guy), Kiss Me!"  Typically, the hotter the star, the larger they are, compared to the Sun.  Of course there are always exceptions to the rules, like Betelgeuse being cooler and over 1000 times larger than the Sun.  Typically, the hotter the star and the larger it is, the more luminous it is compared to the Sun.  White dwarfs are the exception to this rule.  They can burn nearly 6 times hotter than the Sun while being 100 times smaller. 

    The first astronomers to plot stars based on their luminosity and temperature were Ejnar Hertzsprung and Henry Norris Russell.  Thanks to them, we now have the Hertzsprung-Russell diagram, or simply the H-R diagram.  Below you will find an updated version of this diagram created by Astronomy Magazine and found on the Astronomy, Science and No Flat Earth! website HERE.  

       This diagram even shows the names of several stars so a viewer can compare them to the Sun.  The stars that make up the main line on this diagram are called Main Sequence stars.  As you can see, the majority of stars are main sequence stars. The outliers are the giant and supergiant stars found at the top, and the dwarf stars that are found below the main sequence stars.  Typically, the more massive the star is the shorter lifespan it will have.  Stars that are more than 50 times the mass of our Sun can have a lifespan of only millions of years instead of billions of years like a main sequence star.  

    I can recall an assignment from a class where I had to take actual data from about 100 stars and plot their brightness compared to their temperature.  The result was an H-R diagram similar to the one above, but admittedly not nearly as pleasing to the eye.  In fact, it was only black and white, but nearly all of the stars that were sampled fell on the main sequence with a few outliers like Rigel (blue supergiant) and Betelgeuse (red supergiant).             

    Stay tuned for more exciting news and events!  

Now get outside and look up!

Planet images taken by NASA.

Andrew vs. the Cosmos taken by Jeff Greenland.